301
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Immler S, Mazzoldi C, Rasotto MB. From sneaker to parental male: Change of reproductive traits in the black goby,Gobius niger (Teleostei, Gobiidae). ACTA ACUST UNITED AC 2004; 301:177-85. [PMID: 14743517 DOI: 10.1002/jez.a.20019] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This study focuses on the consequences of the switch of tactic from parasitic to parental male in the black goby, Gobius niger (Teleostei: Gobiidae), a species showing two alternative male mating tactics. Older and larger males defend nests, court, and perform parental care on eggs, while younger and smaller ones behave as parasites, sneaking into nests while spawning occurs. Males adopting different tactics are known to present differences in primary and secondary sex traits. The social context of sneaker males was manipulated to induce a tactic switch. Sneakers were kept under two different experimental treatments with or without a female, and under exclusion of male-male competition. Males changed tactics, courting females, spawning, and performing parental care. All males showed substantial changes in primary sexual traits, such as a reduction in gonadal development and an increase in the investment in accessory structures. The experimental groups differed in the functionality of gonads and accessory organs and in the development of the secondary sex traits. These results demonstrate that the moment of switching is not genetically fixed in the black goby. Sneaker males are able to quickly reallocate energy in primary and secondary sex traits, in accordance with the adopted tactic. Several aspects of this flexible reproductive pattern resemble the socially controlled sex change found in sequential hermaphrodites.
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Affiliation(s)
- Simone Immler
- University of Basel, Zoological Institute, Rheinsprung 9, 4051 Basel, Switzerland
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302
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Byrne PG, Simmons LW, Roberts JD. Sperm competition and the evolution of gamete morphology in frogs. Proc Biol Sci 2003; 270:2079-86. [PMID: 14561298 PMCID: PMC1691467 DOI: 10.1098/rspb.2003.2433] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Despite detailed knowledge of the ultrastructure of spermatozoa, there is a paucity of information on the selective pressures that influence sperm form and function. Theoretical models for both internal and external fertilizers predict that sperm competition could favour the evolution of longer sperm. Empirical tests of the external-fertilization model have been restricted to just one group, the fishes, and these tests have proved equivocal. We investigated how sperm competition affects sperm morphology in externally fertilizing myobatrachid frogs. We also examined selection acting on egg size, and covariation between sperm and egg morphology. Species were ranked according to probability of group spawning and hence risk of sperm competition. Body size, testis size and oviposition environment may also influence gamete traits and were included in our analyses. After controlling for phylogenetic relationships between the species examined, we found that an increased risk of sperm competition was associated with increased sperm head and tail lengths. Path analysis showed that sperm competition had its greatest direct effect on sperm tail length, as might be expected under selection resulting from competitive fertilization. Sperm competition did not influence egg size. Oviposition location had a strong influence on egg size and a weak influence on sperm length, with terrestrial spawners having larger gametes than aquatic spawners. Our analysis revealed significant correlated evolution between egg morphology and sperm morphology. These data provide a conclusive demonstration that sperm competition selects for increased sperm length in frogs, and evidence for evolutionary covariance between aspects of male and female gamete morphology.
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Affiliation(s)
- Phillip G Byrne
- Evolutionary Biology Research Group, Zoology Building, School of Animal Biology (M092), University of Western Australia, WA 6009, Australia
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303
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Pitnick S, Miller GT, Schneider K, Markow TA. Ejaculate-female coevolution in Drosophila mojavensis. Proc Biol Sci 2003; 270:1507-12. [PMID: 12965017 PMCID: PMC1691392 DOI: 10.1098/rspb.2003.2382] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Interspecific studies indicate that sperm morphology and other ejaculatory traits diverge more rapidly than other types of character in Drosophila and other taxa. This pattern has largely been attributed to postcopulatory sexual selection involving interaction between the sexes. Such divergence has been suggested to lead rapidly to reproductive isolation among populations and thus to be an 'engine of speciation.' Here, we test two critical predictions of this hypothesis: (i) there is significant variation in reproductive traits among incipient species; and (ii) divergence in interacting sex-specific traits exhibits a coevolutionary pattern among populations within a species, by examining geographical variation in Drosophila mojavensis, a species in the early stages of speciation. Significant among-population variation was identified in sperm length and female sperm-storage organ length, and a strong pattern of correlated evolution between these interacting traits was observed. In addition, crosses among populations revealed coevolution of male and female contributions to egg size. Support for these two important predictions confirms that coevolving internal characters that mediate successful reproduction may play an important part in speciation. The next step is to determine exactly what that role is.
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Affiliation(s)
- Scott Pitnick
- Department of Biology, Syracuse University, 108 College Place, Syracuse, NY 13244-1270, USA.
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304
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Fishelson L. Comparison of testes structure, spermatogenesis, and spermatocytogenesis in young, aging, and hybrid cichlid fish (Cichlidae, Teleostei). J Morphol 2003; 256:285-300. [PMID: 12655611 DOI: 10.1002/jmor.10089] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Testis structure, spermatogenesis, and spermatocytogenesis were compared in 13 species of cichlid fishes, belonging to the subfamilies Haplochrominae and Tilapinae. The species studied were either mouth brooders, in which fertilization occurs mostly inside the mouth of the brooding fish, or substrate brooders, whose eggs adhere to a substrate over which the sperm is ejaculated. In this study, the embryogenesis of testes anlagen and sperm production was followed in embryos and in fish up to 15 years old, as well as in hybrids of the two subfamilies. In cichlids, the testes are of the unrestricted type and primary spermatogonia develop along the entire length of the developing sperm tubule. The first primary spermatogonia are observed in the testes anlagen 2-5 days after fertilization and they continue to develop in cysts formed by the enveloping Sertoli cells and the intertubular elements. The dimensions of such primary and secondary spermatocysts are correlated with the number of spermatogonia they contain and the corresponding number of mitotic multiplications. The largest mature cysts attained 300 microm, and contained 2,200-2,400 spermatids in the mouth-brooding species and 2,600-3,200 in the substrate-brooding species. Despite the fact that in such cysts cytoplasmic bridges connect only the isogamete spermatids, the maturation of all cells and consequent spermiation is synchronized. Meristic characters distinguish the sperm of mouth brooders from those of substrate brooders, especially in the number of mitochondria and length of the flagellum. In older fish and hybrids, various changes can be seen in the gametogenic epithelium and intertubular cells. These include thickening of the connective tissue, formation of "yellow" groups of Leydig cells, cell apoptosis and degeneration, and, especially, formation of large spermatogonia, with large, electron-dense nucleoli, that have the cytological characteristics of oocytes. The intra- and interspecific variability of sperm dimensions in the studied cichlids poses an interesting question in the context of sperm competition.
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Affiliation(s)
- Lev Fishelson
- Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
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305
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Hills JM, Thomason JC. The ‘ghost of settlement past’ determines mortality and fecundity in the barnacle,Semibalanus balanoides. OIKOS 2003. [DOI: 10.1034/j.1600-0706.2003.12332.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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306
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Muñoz RC, Warner RR. A new version of the size-advantage hypothesis for sex change: incorporating sperm competition and size-fecundity skew. Am Nat 2003; 161:749-61. [PMID: 12858282 DOI: 10.1086/374345] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2001] [Accepted: 10/28/2002] [Indexed: 11/03/2022]
Abstract
Traditional sex-change theory cannot explain the existence of protogynous species in which the largest females do not change sex when provided an opportunity. We present an expected reproductive success threshold model that incorporates previously unconsidered factors (size-fecundity skew and sperm competition) that can strongly affect reproductive expectations. The model predicts a variety of circumstances when the largest females remaining in a social group should not change sex in the absence of the dominant male, yet it also predicts that these same conditions should promote sex change in smaller females. If a large female's fecundity is markedly higher than the aggregate of the other members of her social group (i.e., there exists a skew in the size-fecundity distribution that raises a large female's expected reproductive success threshold), she should defer from sex change. Sperm competition can strongly lower the expectation of paternity obtained as a sex-changed male, and this also raises the threshold. The model suggests that deferral of sex change should be more common in species in which intense sperm competition is prevalent (such as fishes living in seagrass beds). This prediction appears consistent with patterns seen in nature.
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Affiliation(s)
- Roldan C Muñoz
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California 93106-9610, USA.
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307
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Abstract
Sperm length is highly variable within and across species, but relatively little attention has been paid to this variation. Two recent studies employing laboratory selection experiments have provided novel insights into the evolution of sperm size.
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Affiliation(s)
- D J Hosken
- Zoology Museum, The University of Zürich, Winterthurerstr. 190, 8057 Zürich, Switzerland.
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308
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Schulte-Hostedde AI, Millar JS, Hickling GJ. Intraspecific variation in testis size of small mammals: implications for muscle mass. CAN J ZOOL 2003. [DOI: 10.1139/z03-040] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intraspecific variation in testis size is usually interpreted in the context of sperm competition, yet an unconsidered consequence of increased testis size may be an increase in the production of testosterone, which can affect the growth of muscle mass. After muscle mass is corrected for body size, male small mammals have more muscle mass than females, which suggests that it may be a sexually selected trait. An enhanced musculature may have fitness consequences with respect to male mate-searching activities and malemale competition for access to females. We tested the prediction that males with large testes have more muscle mass (measured as lean dry mass) by examining testis size and body composition in three species of small mammals (bushy-tailed wood rat (Neotoma cinerea), deer mouse (Peromyscus maniculatus), and red-backed vole (Clethrionomys gapperi)) from the Kananaskis Valley, Alberta. In all three species, males with relatively large testes had relatively more lean dry mass than males with relatively small testes. This suggests that a secondary consequence of relatively large testes may be a relative increase in muscle mass. Further research should investigate alternative effects of intraspecific variation in testis size on individual fitness within wild populations to gain further insight into sexual selection.
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309
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Gage MJG, Freckleton RP. Relative testis size and sperm morphometry across mammals: no evidence for an association between sperm competition and sperm length. Proc Biol Sci 2003; 270:625-32. [PMID: 12769463 PMCID: PMC1691278 DOI: 10.1098/rspb.2002.2258] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Understanding why there is extensive variation in sperm form and function across taxa has been a challenge because sperm are specialized cells operating at a microscopic level in a complex environment. This comparative study collates published data to determine whether the evolution of sperm morphometry (sperm total length and separate component dimensions) is associated with sperm competition (when different males' sperm mix and compete for a female's ova) across 83 mammalian species. We use relative testes mass as an indicator of the intensity of sperm competition across taxa: relative investment into testes is widely accepted to predict the level of sperm competition that a species or population endures. Although we found evidence for positive associations between relative testes mass (controlling for allometry) and sperm morphometry across 83 mammalian species, these relationships were phylogenetically dependent. When we appropriately controlled for phylogenetic association using multiple regression within a phylogenetic framework, there was no relationship between relative testes mass and sperm length across mammals. Furthermore, we found no evidence for associations between relative testes mass and sperm head, mid-piece or flagellar lengths, nor was there a relationship with mid-piece or mitochondrial volumes. Results, therefore, indicate that sperm competition does not select for longer or shorter sperm across mammals, and alternative forces selecting on sperm form and function are discussed.
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Affiliation(s)
- Matthew J G Gage
- Centre for Ecology, Evolution and Conservation, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
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310
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Preston BT, Stevenson IR, Pemberton JM, Coltman DW, Wilson K. Overt and covert competition in a promiscuous mammal: the importance of weaponry and testes size to male reproductive success. Proc Biol Sci 2003; 270:633-40. [PMID: 12769464 PMCID: PMC1691283 DOI: 10.1098/rspb.2002.2268] [Citation(s) in RCA: 201] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Male contests for access to receptive females are thought to have selected for the larger male body size and conspicuous weaponry frequently observed in mammalian species. However, when females copulate with multiple males within an oestrus, male reproductive success is a function of both pre- and postcopulatory strategies. The relative importance of these overt and covert forms of sexual competition has rarely been assessed in wild populations. The Soay sheep mating system is characterized by male contests for mating opportunities and high female promiscuity. We find that greater horn length, body size and good condition each independently influence a male's ability to monopolize receptive females. For males with large horns at least, this behavioural success translates into greater siring success. Consistent with sperm-competition theory, we also find that larger testes are independently associated with both higher copulation rates and increased siring success. This advantage of larger testes emerges, and strengthens, as the number of oestrous females increases, as dominant males can no longer control access to them all. Our results thus provide direct quantitative evidence that male reproductive success in wild populations of mammals is dependent upon the relative magnitude of both overt contest competition and covert sperm competition.
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Affiliation(s)
- B T Preston
- Institute of Biological Sciences, University of Stirling, Stirling FK9 4LA, UK.
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311
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Oppliger A, Naciri-Graven Y, Ribi G, Hosken DJ. Sperm length influences fertilization success during sperm competition in the snail Viviparus ater. Mol Ecol 2003; 12:485-92. [PMID: 12535098 DOI: 10.1046/j.1365-294x.2003.01748.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Sperm form and size is tremendously variable within and across species. However, a general explanation for this variation is lacking. It has been suggested that sperm size may influence sperm competition, and there is evidence for this in some taxa but not others. In addition to normal fertilizing sperm, a number of molluscs and insects produce nonfertile sperm that are also extremely morphologically variable, and distinct from fertilizing forms. There is evidence that nonfertile sperm play an indirect role in sperm competition by decreasing female remating propensity in Lepidopterans, but in most taxa the function of parasperm is unknown. We investigated the role of nonfertile (oligopyrene) sperm during sperm competition in the fresh water snail Viviparus ater. Previous studies found that the proportion of oligopyrene sperm increased with the risk of sperm competition, and hence it seems likely that these sperm influence fertilization success during competitive matings. In mating experiments in which females were sequentially housed with males, we examined a range of male characteristics which potentially influence fertilization success. We found that the size of oligopyrene sperm was the best predictor of fertilization success, with males having the longer sperm siring the highest proportion of offspring. Furthermore, we found a positive shell size and sperm concentration effect on paternity, and females with multiply sired families produced more offspring than females mating with only one male. This result suggests polyandry is beneficial for female snails.
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Affiliation(s)
- A Oppliger
- Zoology Museum, University of Zürich, Zürich, Switzerland, Institute of Ecology, Department of Zoology, Lausanne, Switzerland
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312
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Fraser EJ, Stacey N. Isolation increases milt production in goldfish. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 2002; 293:511-24. [PMID: 12486811 DOI: 10.1002/jez.10120] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Milt volume in goldfish is increased by female steroid and prostaglandin pheromones, by exposure to males with elevated gonadotropin levels, and by isolation from conspecifies. This study examined various aspects of the isolation effect on milt volume and serum gonadotropin II (GTH II). The latency of isolation-induced milt increase in this study (12-24 hr) was longer than the latencies to pheromone-induced milt increase in previous work (0.5-6.0 hr), was not affected by the time of day at which males were isolated, persisted for at least 72 hr in isolated males, and was terminated within 24 hr in males that were returned to groups. Isolated males maintained high milt production when separated from tank mates by a perforated barrier or when exposed to visual and odor cues from males in other tanks, suggesting that the unknown conspecific cues that maintain low milt production in groups operate at close range. Isolation appears to increase milt through a mechanism different from that mediating response to female pheromones because: (1) unlike female pheromones, which consistently increase serum GTH II, no isolation or regrouping treatment in this study affected male GTH II concentration; and (2) the effects of isolation and of exposure to the female pheromone 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) are additive. Finally, males that were previously isolated or exposed to 17,20 beta-P increased milt (but not GTH II) in grouped males, suggesting that the effects of isolation and pheromone exposure can indirectly stimulate male conspecifics. Although the biological function of the isolation effect is not clear, we propose that it illustrates the effect of removal from inhibitory cues normally received from male conspecifies.
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Affiliation(s)
- E Jane Fraser
- School of Biological Sciences, University of Liverpool, Liverpool L69 3GS, United Kingdom.
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313
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Hellriegel B, Blanckenhorn W. Environmental influences on the gametic investment of yellow dung fly males. Evol Ecol 2002. [DOI: 10.1023/a:1020875021823] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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314
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Morrow EH, Arnqvist G, Pitcher TE. The evolution of infertility: does hatching rate in birds coevolve with female polyandry? J Evol Biol 2002. [DOI: 10.1046/j.1420-9101.2002.00445.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- E. H. Morrow
- Department of Animal Ecology, Evolutionary Biology Centre, Uppsala University, Norbyvägen, Uppsala, Sweden
| | - G. Arnqvist
- Department of Animal Ecology, Evolutionary Biology Centre, Uppsala University, Norbyvägen, Uppsala, Sweden
| | - T. E. Pitcher
- Department of Zoology, University of Toronto, Toronto, Ontario, Canada
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315
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Candolin U, Reynolds JD. Adjustments of ejaculation rates in response to risk of sperm competition in a fish, the bitterling (Rhodeus sericeus). Proc Biol Sci 2002; 269:1549-53. [PMID: 12184824 PMCID: PMC1691068 DOI: 10.1098/rspb.2002.2055] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Game theory models of sperm competition predict that within species, males should increase their sperm expenditure when they have one competitor, but decrease expenditure with increasing numbers of competitors. So far, there have been few tests or support for this prediction. Here, we show that males of a freshwater fish, the European bitterling, Rhodeus sericeus, do indeed adjust their ejaculation rate to the number of male competitors by first increasing and then decreasing their ejaculation rates as the number of competitors increases. However, this occurred only under restricted conditions. Specifically, the prediction was upheld as long as no female had deposited eggs in the live mussels that are used as spawning sites. After one or more females had spawned, males did not decrease their ejaculation rates with the number of competitors, but instead they became more aggressive. This indicates that decreased ejaculation rate and increased aggression are alternative responses to increased risk of sperm competition.
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Affiliation(s)
- Ulrika Candolin
- School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
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316
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Simmons LW, Kotiaho JS. Evolution of ejaculates: patterns of phenotypic and genotypic variation and condition dependence in sperm competition traits. Evolution 2002; 56:1622-31. [PMID: 12353755 DOI: 10.1111/j.0014-3820.2002.tb01474.x] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Sperm competition is widely recognized as a potent force in evolution, influencing male behavior, morphology, and physiology. Recent game theory analyses have examined how sperm competition can influence the evolution of ejaculate expenditure by males and the morphology of sperm contained within ejaculates. Theoretical analyses rest on the assumption that there is sufficient genetic variance in traits important in sperm competition to allow evolving populations to move to the evolutionarily stable equilibrium. Moreover, patterns of genotypic variation can provide valuable insight into the nature of selection currently acting on traits. However, our knowledge of genetic variance underlying traits important in sperm competition is limited. Here we examine patterns of phenotypic and genotypic variation in four sperm competition traits in the dung beetle Onthophagus taurus. Testis weight, ejaculate volume, and copula duration were found to have high coefficients of additive genetic variation (CV(A)S), which is characteristic of fitness traits and traits subject to sexual selection. Heritabilities were high, and there was some evidence for Y-linked inheritance in testis weight. In contrast, sperm length had a low CV(A), which is characteristic of traits subject to stabilizing selection. Nevertheless, there was little residual variance so that the heritability of sperm length exceeded 1.0. Such a pattern is consistent with Y-linked inheritance in sperm length. Interestingly, we found that testis weight and sperm length were genetically correlated with heritable male condition. This finding holds important implications for potential indirect benefits associated with the evolution of polyandry.
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Affiliation(s)
- Leigh W Simmons
- Department of Zoology, University of Western Australia, Nedlands, Australia.
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317
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Uglem I, Mayer I, Rosenqvist G. Variation in plasma steroids and reproductive traits in dimorphic males of corkwing wrasse (Symphodus melops L.). Horm Behav 2002; 41:396-404. [PMID: 12018935 DOI: 10.1006/hbeh.2002.1779] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Differences in plasma steroid levels may reflect behavioral, gonadal, or morphological specializations that characterize different male reproductive phenotypes in teleost fishes. In the present study, we investigated whether differences in plasma steroid levels exist between two distinct male morphs shown in the corkwing wrasse Symphodus melops. In addition, we examined differences in male reproductive traits, including gonad mass, sperm motility, and sperm concentration, between the two male types. Possible associations between plasma steroid levels and reproductive traits were also investigated. The results indicated that males with typical male secondary sexual characters (territorial males) had higher plasma levels of 11-ketotestosterone (11kT) compared to smaller males with female secondary sexual characters (female mimics). The female mimics in turn had higher plasma levels of both testosterone (T) and 17beta-estradiol. In addition, female mimics had relatively larger gonads and longer-lived sperm than territorial males. Relative gonad mass covaried significantly with the plasma levels of 11kT and T among the morphs, indicating that the relative gonad size correlates positively with the plasma level of these two steroids. However, there was no significant covariance between sperm traits and plasma steroids for the two male morphs. Hence, our results do not indicate any causal link between sperm quality and hormones.
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Affiliation(s)
- Ingebrigt Uglem
- Department of Zoology, Norwegian University of Technology and Science, No-7491 Trondheim, Norway.
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318
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Pizzari T, Birkhead TR. The sexually-selected sperm hypothesis: sex-biased inheritance and sexual antagonism. Biol Rev Camb Philos Soc 2002; 77:183-209. [PMID: 12056746 DOI: 10.1017/s1464793101005863] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
When females are inseminated by more than one male (polyandry) sexual selection continues after insemination in the form of sperm competition and cryptic female choice. The sexually-selected sperm hypothesis proposes that, under the risk of sperm competition, additive variation in male traits determining fertilising efficiency will select for female propensity to be polyandrous in order to increase the probability of producing sons with superior fertilising efficiency. Two factors complicate this prediction: sex-biased transmission of male fertilising efficiency traits and sexual antagonism of sex-limited traits, fostered by sex-biased inheritance. Here, we (i) review the evidence that male traits contributing towards fertilising efficiency are heritable through sex-biased mechanisms, and (ii) explore the evolutionary implications for male and female reproductive strategies caused by both sex-biased transmission and sexual antagonism of fertilising efficiency traits. Many male fertilising efficiency traits are heritable through sex-biased mechanisms and may not necessarily increase female fitness. The predictions of the sexually-selected sperm hypothesis change dramatically under these different mechanisms of inheritance of fertilising efficiency traits, and different fitness pay-offs derived by females from the expression of such traits. Both sex-biased control of fertilising efficiency and sexual antagonism may also be important in explaining the maintenance of the genetic variance and selection potential of fertilising efficiency. We propose that a useful approach to test the sexually-selected sperm hypothesis is to combine studies which identify behavioural and physiological mechanisms explaining variation in reproductive success with artificial selection experiments to infer the underlying evolutionary patterns.
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Affiliation(s)
- T Pizzari
- Animal & Plant Science Department, University of Sheffield, UK.
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319
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Byrne PG, Roberts JD, Simmons LW. Sperm competition selects for increased testes mass in Australian frogs. J Evol Biol 2002. [DOI: 10.1046/j.1420-9101.2002.00409.x] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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320
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Abstract
The female reproductive tract is where competition between the sperm of different males takes place, aided and abetted by the female herself. Intense postcopulatory sexual selection fosters inter-sexual conflict and drives rapid evolutionary change to generate a startling diversity of morphological, behavioural and physiological adaptations. We identify three main issues that should be resolved to advance our understanding of postcopulatory sexual selection. We need to determine the genetic basis of different male fertility traits and female traits that mediate sperm selection; identify the genes or genomic regions that control these traits; and establish the coevolutionary trajectory of sexes.
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Affiliation(s)
- Timothy R Birkhead
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
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321
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Schaus JM, Sakaluk SK. Repeatability of sperm number across multiple matings in three cricket species, Gryllodes sigillatus, Gryllus veletis, and Gryllus texensis (Orthoptera: Gryllidae). CAN J ZOOL 2002. [DOI: 10.1139/z02-012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although studies of various taxa have shown that males can alter the number of sperm in their ejaculates according to the risk of sperm competition, few studies have examined the extent to which the number of sperm transferred by males across multiple matings is repeatable. We assess the within-male and between-male components of variation in sperm number by counting the sperm in multiple ejaculates of males of three cricket species and determining the repeatability of sperm number. Sperm number was highly repeatable across multiple matings in all three species, leaving open the possibility that variation in sperm number is based, in part, on heritable genetic variation.
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322
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Simmons LW, Kotiaho JS. EVOLUTION OF EJACULATES: PATTERNS OF PHENOTYPIC AND GENOTYPIC VARIATION AND CONDITION DEPENDENCE IN SPERM COMPETITION TRAITS. Evolution 2002. [DOI: 10.1554/0014-3820(2002)056[1622:eoepop]2.0.co;2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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323
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Bekkevold D, Hansen MM, Loeschcke V. Male reproductive competition in spawning aggregations of cod (Gadus morhua, L.). Mol Ecol 2002; 11:91-102. [PMID: 11903907 DOI: 10.1046/j.0962-1083.2001.01424.x] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Reproductive competition may lead to a large skew in reproductive success among individuals. Very few studies have analysed the paternity contribution of individual males in spawning aggregations of fish species with huge census population sizes. We quantified the variance in male reproductive success in spawning aggregations of cod under experimental conditions over an entire spawning season. Male reproductive success was estimated by microsatellite-based parentage analysis of offspring produced in six separate groups of spawning cod. In total, 1340 offspring and 102 spawnings distributed across a spawning season were analysed. Our results show that multiple males contributed sperm to most spawnings but that paternity frequencies were highly skewed among males, with larger males on average siring higher proportions of offspring. It was further indicated that male reproductive success was dependent on the magnitude of the size difference between a female and a male. We discuss our results in relation to the cod mating system. Finally, we suggest that the highly skewed distribution of paternity success observed in cod may be a factor contributing to the low effective population size/census population size ratios observed in many marine organisms.
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Affiliation(s)
- D Bekkevold
- Institute of Biological Sciences, Department of Ecology & Genetics, University of Aarhus, DK-8000 Arhus C, Denmark.
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324
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Vladić TV, Afzelius BA, Bronnikov GE. Sperm quality as reflected through morphology in salmon alternative life histories. Biol Reprod 2002; 66:98-105. [PMID: 11751270 DOI: 10.1095/biolreprod66.1.98] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Male salmon exhibit alternative mating strategies, as both older anadromous adults and precocious juveniles (parr) participate in the spawning of a single female. This study tested the following hypotheses: 1) different intensities of sperm competition may reflect different sperm tail optima; 2) long spermatozoa are superior to short ones, with an associated cost on sperm longevity; and 3) a disfavored role in sperm competition selects for parr investing more in sperm quality. Comparisons included sperm morphological traits, whereas sperm quality was investigated by motility duration observations, measurement of the sperm adenylate system, and fertilization experiments. No evidence of different adaptive sperm dimensions between the male types was found. Positive association between spermatocrit and energy charge was, however, detected. Sperm length parameters correlated positively with ATP, energy charge, and fertilization success, whereas no evidence for an effect of sperm morphology on longevity was found. Male parr had greater spermatocrit than adults and fertilized equal proportions of eggs as adults despite a pronounced numerical subordinance in the fertilization experiments. It is concluded that a long sperm tail and midpiece may be selected to optimize energetic demands under conditions of increased sperm competition intensity.
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Affiliation(s)
- Tomislav V Vladić
- Department of Zoology, Stockholm University, SE-106 91 Stockholm, Sweden.
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325
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Mery F, Joly D. Multiple mating, sperm transfer and oviposition pattern in the giant sperm species, Drosophila bifurca. J Evol Biol 2002. [DOI: 10.1046/j.1420-9101.2002.00364.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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326
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Stacey N, Fraser EJ, Sorensen P, Van der Kraak G. Milt production in goldfish: regulation by multiple social stimuli. Comp Biochem Physiol C Toxicol Pharmacol 2001; 130:467-76. [PMID: 11738634 DOI: 10.1016/s1532-0456(01)00273-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Previous studies in goldfish (Carassius auratus) demonstrate that milt (sperm and seminal fluid) volume is increased both by a preovulatory steroidal pheromone, 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P), that acts by increasing serum concentrations of gonadotropin II (GTH-II), and by a post-ovulatory prostaglandin (PG) pheromone, that acts by stimulating sexual interactions. Here, we show that male goldfish also increase milt volume when isolated for 24 h, or when placed with another male injected with human chorionic gonadotropin (hCG) for 12 h. In contrast to the milt increase induced by pheromonal 17,20 beta-P, the milt increase following isolation or exposure to hCG-injected males was not associated with increased serum GTH-II. Serum growth hormone also was unaffected, although serum testosterone increased in isolated males. The absence of GTH-II increase following isolation or exposure to hCG-injected males and the long latency time for these two types of responses, suggests these effects are mediated by a novel mechanism as yet undescribed. The present findings suggest that sperm competition has selected for complex mechanisms regulating milt production and fertility in goldfish: males regulate milt production not only in response to stimulatory pheromonal cues from ovulatory females, but also in response to unknown stimulatory and inhibitory cues from male competitors.
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Affiliation(s)
- N Stacey
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9.
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327
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Morrow EH, Gage MJ. Sperm competition experiments between lines of crickets producing different sperm lengths. Proc Biol Sci 2001; 268:2281-6. [PMID: 11674877 PMCID: PMC1088877 DOI: 10.1098/rspb.2001.1807] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Sperm numbers can be important determinants of fertilization success in sperm competition. However, the importance of variation in sperm size is less well understood. Sperm size varies significantly both between and within species and comparative studies have suggested that some of this variance can be explained by sperm competition. In this study we examine whether variation in sperm length has consequences for fertilization precedence using controlled sperm competition experiments in the field cricket Gryllus bimaculatus. This species is an ideal model for such investigations because the mechanism of sperm competition generates complete mixing of different males' spermatozoa in the female (thereby allowing individual sperm to express their own competitive abilities). We successfully bred lines of crickets, the males of which produced short, medium and long sperm types with narrow and non-overlapping distributions. Males of different lines were then sequentially mated with control females in order to create two-male sperm competitions. The paternity outcomes of these competitions were measured after matings using an irradiated male technique (with a full reciprocal design that controls for natural fertility and any irradiation effects on gamete competitiveness) over a 12 day oviposition period. However, having successfully bred diverging sperm length lines and competing males that differed in sperm length, we found no evidence that a male's sperm size explained any of the variation in their relative fertilization success. Males from lines producing longer sperm showed no fertilization advantage over males producing shorter sperm across 97 double matings. There was also no advantage for males producing a sperm length close to the population mean over those competitors whose sperm length had been selectively diverged across 63 matings.
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Affiliation(s)
- E H Morrow
- Department of Ecology and Environmental Science, University of Umeå, SE-901 87 Umeå, Sweden.
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328
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Morrow EH, Gage MJ. Artificial selection and heritability of sperm length in Gryllus bimaculatus. Heredity (Edinb) 2001; 87:356-62. [PMID: 11737282 DOI: 10.1046/j.1365-2540.2001.00921.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The adaptive significance of variation in sperm size remains poorly understood but there has been even less attention focused on the genetic mechanisms controlling spermatozoal traits (only three species have been studied). Here we explore heritability and artificial selection of sperm length in the cricket Gryllus bimaculatus. Using a within-family selection design we selected sperm with increasing and decreasing sperm size and bred divergence across five generations. Although we recorded no significant parent-offspring heritability, realized heritability from a within-family analysis was significant at 0.52 +/- 0.06 SE (P = 0.01) and we successfully achieved significant divergence. However, we only achieved a response when the maternal line was incorporated into selection (from the F1 onwards) and our findings therefore suggest that sperm length in G. bimaculatus is a sex-linked trait that is influenced by genes which are active on the female chromosome. Accordingly, sperm length heritability in G. bimaculatus can only be measured using a within-family design because the spermatozoal phenotype is sex-limited (to males) while the genotype is sex-linked (to females). The evolutionary significance of the heritability of sperm length is discussed with reference to sex-linkage of this important sex-limited trait.
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Affiliation(s)
- E H Morrow
- Population and Evolutionary Biology Research Group, Nicholson Building, School of Biological Sciences, University of Liverpool, Liverpool, L69 3BX, UK.
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329
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Evans JP, Magurran AE. Patterns of sperm precedence and predictors of paternity in the Trinidadian guppy. Proc Biol Sci 2001; 268:719-24. [PMID: 11321060 PMCID: PMC1088661 DOI: 10.1098/rspb.2000.1577] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Despite its widespread occurrence in animals, sperm competition has been studied in a limited range of taxa. Among the most neglected groups in this respect are internally fertilizing fish in which virtually nothing is known about the dynamics of sperm competition. In this study, we examined the outcome of sperm competition when virgin female guppies mated with two males. Behavioural cues were used to ensure that each male mated once (with female cooperation) and that sperm were successfully inseminated at copulation. Two polymorphic microsatellite loci were used to estimate the proportion of offspring sired by the second male (P2) and the results revealed a bimodal distribution with either first or (more often) second male priority The observed P2 distribution differed from that expected under the 'fair raffle' model of sperm competition. Random sperm mixing is therefore unlikely to account for the observed variance in P2 in this study. A further aim of our study was to identify predictors of male reproductive success. Using logistic linear modelling, we found that the best predictors of paternity were time to remating and the difference in courtship display rate between first and second males. Males that mated quickly and performed relatively high numbers of sigmoid displays obtained greater parentage than their slower and less vigorous counterparts. Since females are attracted to high-displaying males, our results suggest that female choice may facilitate sperm competition and/or sperm choice in guppies.
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Affiliation(s)
- J P Evans
- Environmental and Evolutionary Biology, University of St Andrews, Fife, UK.
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330
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331
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Brockmann HJ, Nguyen C, Potts W. Paternity in horseshoe crabs when spawning in multiple-male groups. Anim Behav 2000; 60:837-849. [PMID: 11124883 DOI: 10.1006/anbe.2000.1547] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Unpaired or satellite male horseshoe crabs, Limulus polyphemus, are attracted to and often form a group around a pair (a female with an attached male) that is nesting in the high intertidal zone. These males are engaged in sperm competition. We observed nesting pairs and their associated satellites in the wild, collected and reared their eggs and used genetic markers to examine paternity. We found that the unpaired, satellite males are highly successful at fertilizing eggs; two satellites can leave the attached male with few fertilizations. Two satellites together are each as successful as one spawning with a pair. A satellite's location around the female greatly affects his success, and males compete for access to a position over the dorsal canal between the prosoma and opisthosoma of the female and under the front margin of the paired male where they are most likely to fertilize eggs. Although eggs and sperm retain their viability for some time after spawning, nearly all eggs are fertilized by the satellites that are around the nesting pair at the time of egg laying and by the attached male. A number of factors including beach current, female size and male behaviour affect the outcome of sperm competition in this externally fertilizing species. Copyright 2000 The Association for the Study of Animal Behaviour.
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332
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Alonzo SH, Warner RR. Allocation to Mate Guarding or Increased Sperm Production in a Mediterranean Wrasse. Am Nat 2000; 156:266-275. [PMID: 29587505 DOI: 10.1086/303391] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
An excellent body of literature exists that examines sperm expenditure when males allocate only to sperm production. However, in many species, males can also allocate energy to behaviors that influence sperm competition. We model whether males in sperm competition should allocate energy to mate guarding or additional sperm production. Mate guarding is predicted to lead to greater reproductive success than increased sperm output, and mate-guarding males are not predicted to alter their allocation to sperm production with increasing sperm competition. Only when mate guarding is ineffective or greatly reduces sperm production are males predicted to allocate to sperm production. In a Mediterranean wrasse Symphodus ocellatus, three male alternative reproductive behaviors coexist. While nesting males and satellites guard mates to decrease sperm competition, sneaker males only compete via sperm production. Sneakers produce four times as much sperm per spawn as either nesting males or satellites. As predicted by the model, mate guarding but not sperm production increased with increased risk of sperm competition in nesting males. We argue that this can be explained by nesting males allocating to mate guarding rather than sperm production. Considering allocation among behaviors that affect sperm competition enhances our ability to explain and to predict sperm allocation patterns.
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333
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334
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Pitnick S, Miller GT. Correlated response in reproductive and life history traits to selection on testis length in Drosophila hydei. Heredity (Edinb) 2000; 84 ( Pt 4):416-26. [PMID: 10849065 DOI: 10.1046/j.1365-2540.2000.00679.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Flies in the genus Drosophila have undergone striking evolutionary divergence in the size and number of sperm produced. Based on comparative studies of sperm length, testis length, and other reproductive and life history traits, including body size, age at first reproduction, and the number of sperm produced, macroevolutionary trade-offs resulting from the need to produce high-investment testes have been postulated. To understand better the microevolutionary processes underlying these interspecific patterns, we imposed replicated bidirectional selection for testis length for 11-12 generations on D. hydei, a species with 23.5 mm-long sperm and 30 mm-long testes. Testis length exhibited realized heritabilities ranging from 0.45 to 0.72. Following selection, traits were assayed for correlated responses. Thorax length, testis mass, sperm length, egg-to-adult development time, and posteclosion maturation time showed consistent positive correlated responses. Numbers of sperm produced and transferred to females, male longevity, female egg productivity, and seminal receptacle length did not show consistent correlated responses to selection on testis length. The pattern of correlated responses to testis length reveal the potential for the evolution of reproductive strategies to alter important life history attributes.
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Affiliation(s)
- S Pitnick
- Department of Biology, Syracuse University, 108 College Place, Syracuse, NY, 13244-1270, USA.
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335
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Abstract
Sperm form and function remain poorly understood despite being of fundamental biological importance. An instructive approach has been to examine evolutionary associations across comparable taxa between sperm characters and other, potentially selective reproductive traits. We adopt this approach here in a comparative study examining how sperm lengths are associated with male and female reproductive characters across moths. Primary data have revealed Lepidoptera to be an ideal order for examination: there is profound variation in the dimensions (but not organization) of the reproductive traits between closely related species which all share a monophyletic ancestry, for example, eupyrene sperm length varies from 110 to 12,675 microm. Eupyrene (normal fertilizing) and apyrene (anucleate and non-fertile) sperm lengths are positively correlated across taxa and both sperm types show positive associations with mating pattern (as measured by the residual testis size). At fertilization, eupyrene sperm must migrate down the often elongated female spermathecal duct from storage to unite with the ovum. Across taxa, the elongation of this duct is associated with increased eupyrene sperm length, suggesting a positive female influence on sperm size since longer, more powerful sperm may be selected to migrate and/or compete successfully down greater ductal lengths. Apyrene sperm length is not associated with female reproductive tract dimensions. However, we found a positive relationship between the residual testis volume and spermathecal volume, suggesting coevolution between male investment in spermatogenesis and the extent of the female sperm storage capacity. Within males, there is a positive association between the two organs which form the ejaculate-containing spermatophore: the testes and the accessory gland. The 'trade-up' in investment to these components is discussed in relation to paternal investment and mating patterns.
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Affiliation(s)
- E H Morrow
- Population and Evolutionary Biology Research Group, School of Biological Sciences, University of Liverpool, UK.
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336
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Abstract
There has been wide disagreement as to whether sperm competition among animals can produce a soldier class of sperm to fight against other males. Utilizing mathematical models, we analyze the appropriate conditions for the evolution and maintenance of a soldier sperm class. We conclude that: (1) soldier sperm evolve even if one soldier sperm can kill or block less than one competing sperm; (2) soldier sperm evolve faster when there is a large variance in the number of competing sperm; (3) soldier ratio increases until reproductive sperm are too scarce to fertilize all ova or a sperm intensely refuses to become a soldier; and (4) soldier sperm are more likely to be smaller than reproductive sperm. Our models suggest that the conditions for the evolution of a soldier sperm class are not stringent.
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Affiliation(s)
- T Kura
- Department of Zoology, Graduate School of Science, Kyoto University, Japan.
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337
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338
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Evans JP, Magurran AE. Male mating behaviour and sperm production characteristics under varying sperm competition risk in guppies. Anim Behav 1999; 58:1001-1006. [PMID: 10564602 DOI: 10.1006/anbe.1999.1212] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Since natural populations of guppies, Poecilia reticulata, often differ from one another in social structure, the intensity of sperm competition is likely to vary between localities. Guppies are promiscuous, with female choice for colourful males playing a central role in the mating system. In addition, male guppies use forced copulations to circumvent female choice. Both methods of copulation are used interchangeably by individual males, but the degree to which either is used may depend on the social environment into which males are born. Here we show that male mating behaviour varies according to the rearing sex ratio: when reared in male-biased groups, males performed more forced copulations and fewer courtship displays but showed the opposite pattern of behaviour when reared in female-biased groups. Our prediction, based on sperm competition theory, that stripped sperm number would reflect social structure was not supported by our results. Instead, the overall level of sexual activity (gonopodial thrusts+sigmoid displays) was a better predictor of sperm number in the different groups of males. Rearing density, where sex ratio was controlled, did not significantly affect male mating behaviour or sperm traits. Males reared under the different sex ratios continued to show their characteristic behaviour patterns when placed in equal sex ratio tanks. We conclude, therefore, that males adopt mating strategies to suit their social environment, and that these strategies remain fixed, for short periods at least, if population structure changes. Copyright 1999 The Association for the Study of Animal Behaviour.
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Affiliation(s)
- JP Evans
- Institute of Environmental and Evolutionary Biology, University of St Andrews
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339
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Evans J, Magurran AE. Geographic variation in sperm production by Trinidadian guppies. Proc Biol Sci 1999. [DOI: 10.1098/rspb.1999.0891] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Jonathan.P. Evans
- Institute of Environmental and Evolutionary Biology, University of St Andrews, St Andrews, Fife KY16 9TS, UK
| | - Anne E. Magurran
- Institute of Environmental and Evolutionary Biology, University of St Andrews, St Andrews, Fife KY16 9TS, UK
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340
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Liljedal S, Folstad I, Skarstein F. Secondary sex traits, parasites, immunity and ejaculate quality in the Arctic charr. Proc Biol Sci 1999. [DOI: 10.1098/rspb.1999.0863] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Ståle Liljedal
- Department of Ecology, Faculty of Science, University of Tromso, N–9037 TromsB, Norway
| | - Ivar Folstad
- Department of Ecology, Faculty of Science, University of Tromso, N–9037 TromsB, Norway
| | - Frode Skarstein
- Department of Ecology, Faculty of Science, University of Tromso, N–9037 TromsB, Norway
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341
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Wedell N, Cook PA. Butterflies tailor their ejaculate in response to sperm competition risk and intensity. Proc Biol Sci 1999. [DOI: 10.1098/rspb.1999.0740] [Citation(s) in RCA: 154] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Nina Wedell
- Department of Zoology, University of Stockholm, S–106 91 Stockholm, Sweden
| | - Penny A. Cook
- Department of Zoology, University of Stockholm, S–106 91 Stockholm, Sweden
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342
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Coevolution of sperm and female reproductive tract morphology in stalk-eyed flies. Proc Biol Sci 1999; 266:1041-1047. [PMCID: PMC1689941 DOI: 10.1098/rspb.1999.0741] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/26/2024] Open
Abstract
Sperm and female reproductive tract morphology are among the most rapidly evolving characters known in insects. To investigate whether interspecific variation in these traits results from divergent coevolution we examined testis size, sperm length and female reproductive tract morphology for evidence of correlated evolution using 13 species of diopsid stalk-eyed flies. We found that sperm dimorphism (the simultaneous production of two size classes of sperm by individual males) is ancestral and occurs in four genera while sperm monomorphism evolved once and persists in one genus. The length of 'long-sperm' types, though unrelated to male body or testis size, exhibits correlated evolution with two regions of the female reproductive tract, the spermathecae and ventral receptacle, where sperm are typically stored and used for fertilization, respectively. Two lines of evidence indicate that 'short sperm', which are probably incapable of fertilization, coevolve with spermathecae. First, loss of sperm dimorphism coincides phylogenetically with reduction or loss of spermathecae. Second, evolutionary change in short-sperm length correlates with change in spermathecal size but not spermathecal duct length or ventral receptacle length. Morphological coevolution between sperm and female reproductive tracts is consistent with a history of female-mediated selection on sperm length.
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343
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Scaggiante M, Mazzoldi C, Petersen C, Rasotto M. Sperm competition and mode of fertilization in the grass gobyZosterisessor ophiocephalus(Teleostei: Gobiidae). ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1097-010x(19990101)283:1<81::aid-jez9>3.0.co;2-9] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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344
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Sperm competition affects male behaviour and sperm output in the rainbow darter. Proc Biol Sci 1998; 265:2365-2371. [PMCID: PMC1689547 DOI: 10.1098/rspb.1998.0585] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023] Open
Abstract
Rainbow darters, Etheostoma caeruleum , are promiscuous fish with moderate rates of group spawning (between one and five males may simultaneously mate with one female). In this study, I examined male sperm output and male willingness to spawn under different levels of sperm competition intensity. One male and one female were allowed to spawn in an aquarium where they had visual and olfactory access to one of four treatments: four males, one male, zero males, or one female. Theory predicts that males should reduce sperm output when there are more than the average number of males at a group spawning (four-male treatment) and should increase sperm output when there are fewer than average males at a group spawning (one-male treatment). Mean sperm output did not differ among treatments. However, males released more sperm when spawning in the presence of competing males (four-male and one-male treatments pooled) than when spawning in the absence of competing males (zero-male and one-female treatments pooled). Males were also most likely to forego spawning opportunities when sperm competition intensity was high. Furthermore, male willingness to spawn was size dependent. Large males were more likely to forego spawning opportunities under high sperm competition intensity. Large males may be better off waiting for future spawning opportunities when there is a lower potential for sperm competition intensity.
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345
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346
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Oppliger A, Hosken DJ, Ribi G. Snail sperm production characteristics vary with sperm competition risk. Proc Biol Sci 1998. [DOI: 10.1098/rspb.1998.0468] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- A. Oppliger
- Zoological Museum of the University of Zü rich, Winterthurerstrasse 190, 8057 Zü rich, Switzerland
| | - D. J. Hosken
- Zoological Museum of the University of Zü rich, Winterthurerstrasse 190, 8057 Zü rich, Switzerland
| | - G. Ribi
- Zoological Museum of the University of Zü rich, Winterthurerstrasse 190, 8057 Zü rich, Switzerland
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347
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Abstract
Understanding the adaptive significance of sperm form and function has been a challenge to biologists because sperm are highly specialized cells operating at a microscopic level in a complex environment. A fruitful course of investigation has been to use the comparative approach. This comparative study attempts to address some fundamental questions of the evolution of mammalian sperm morphometry. Data on sperm morphometry for 445 mammalian species were collated from published sources. I use contemporary phylogenetic analysis to control for the inherent non-independence of species and explore relationships between the morphometric dimensions of the three essential spermatozoal components: head, mid-piece and flagellum. Energy for flagellar action is metabolized by the mitochondrial-dense mid-piece and these combine to propel the sperm head, carrying the male haplotype, to the ovum. I therefore search for evolutionary associations between sperm morphometry and body mass, karyotype and the duration of oestrus. In contrast to previous findings, there is no inverse correlation between body weight and sperm length. Sperm mid-piece and flagellum lengths are positively associated with both head length and area, and the slopes of these relationships are discussed. Flagellum length is positively associated with mid-piece length but, in contrast to previous research and after phylogenetic control, I find no relationship between flagellum length and the volume of the mitochondrial sheath. Sperm head dimensions are not related to either genome mass or chromosome number, and there are no relationships between sperm morphometry and the duration of oestrus.
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Affiliation(s)
- M J Gage
- Population Biology Research Group, School of Biological Sciences, University of Liverpool.
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348
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Parker GA, Ball MA, Stockley P, Gage MJ. Sperm competition games: a prospective analysis of risk assessment. Proc Biol Sci 1997; 264:1793-802. [PMID: 9447737 PMCID: PMC1688741 DOI: 10.1098/rspb.1997.0249] [Citation(s) in RCA: 304] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We develop the logic of assessment of sperm competition risk by individual males where the mechanism of sperm competition follows a 'loaded raffle' (first and second inseminates of a female have unequal prospects). Male roles (first or second to mate) are determined randomly. In model 1, males have no information about the risk associated with individual females and ejaculation strategy depends only on the probability, q, that females mate twice. Evolutionarily stable strategy (ESS) ejaculate expenditure increases linearly from zero with q, and reduces with increasing inequality between ejaculates, though the direction of the loading (which role is favoured) is unimportant. In model 2, males have perfect information and can identify each of three risk states: females that will (1) mate just once ('no risk'), (2) mate twice but have not yet mated ('future risk'), and (3) mate twice and have already mated ('past risk'). The ESS is to ejaculate minimally with 'no risk' females, and to expand equally with 'past' and 'future' risk females; the direction of the competitive loading is again unimportant. Expenditure again increases with risk, but is now non-zero at extremely low risk. Model 3 examines three cases of partial information where males can identify only one of the three risk states and cannot distinguish between the other two: they therefore have just two information sets or 'contexts'. Expenditure in both contexts typically rises non-linearly from zero with q, but (whatever the loading direction) expenditure is higher in the context with higher risk (e.g. if contexts are 'mated' and 'virgin', males spend more with mated females). However, in highly loaded raffles, sperm expenditure can decrease over part of the range of risk. Also, the direction of the loading now affects expenditure. Biological evidence for the predictions of the models is summarized and discussed.
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Affiliation(s)
- G A Parker
- Population Biology Research Group, School of Biological Sciences, University of Liverpool, UK.
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Ejaculate expenditure by malebush crickets decreases with sperm competition intensity. Proc Biol Sci 1997; 264:1203-1208. [PMCID: PMC1688574 DOI: 10.1098/rspb.1997.0166] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023] Open
Abstract
Male bushcrickets transfer a spermatophore at mating that consists of a sperm-containing ampulla and a sperm-free mass, the spermatophylax, that is consumed by the female during insemination. The costs of spermatophore production for males and benefits of consumption for females result in reversals in courtship roles in nutrient limited populations that increase both the risk and intensity of sperm competition. Here we show that under conditions characteristic of courtship role reversal, male expenditure on the spermatophore is dependent on female size. When mating with small females, males increase the amount of spermatophylax material and sperm, as expected from the increased sperm competition risk associated with courtship role reversal. However, males reduce the amount of spermatophylax material and sperm transferred to larger females. Since larger females have a higher mating success when competing for nurturant males, the intensity of sperm competition covaries with female size. Reduced ejaculate expenditure under increased sperm competition intensity is in accord with theoretical expectation.
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350
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Abstract
Sperm competition is a widespread phenomenon influencing the evolution of male anatomy, physiology and behaviour. Bats are an ideal group for studying sperm competition. Females store fertile sperm for up to 200 days and the size of social groups varies from single animals to groups of hundreds of thousands. This study examines the relationship between social group size and investment in spermatogenesis across 31 species of microchiropteran bat using new and published data on testis mass and sperm length. In addition to male competition, I examined the effects of female reproductive biology on characteristics of spermatogenesis. Comparative studies indicate that relative testis mass is positively related to sperm competition risk in a wide range of taxa. Social group size may also influence the level of sperm competition, and one of the costs of living in groups may be decreased confidence of paternity. I used comparative analysis of independent contrast (CAIC) to control for phylogeny. Using two possible phylogenies and two measures of social group size, I found a significant positive relationship between social group size and testis mass. There was no relationship between testis mass and the dimension of the female reproductive tract or oestrus duration. Sperm length was not significantly related to body mass or group size, nor was it related to oestrus duration.
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Affiliation(s)
- D J Hosken
- Zoology Department, University of Western Australia, Nedlands, Perth, Australia
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