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Kaczmarski M, Kaczmarek JM, Jankowiak Ł, Kolenda K, Tryjanowski P. Digit ratio in the common toad Bufo bufo: the effects of reduced fingers and of age dependency. ZOOLOGICAL LETTERS 2021; 7:5. [PMID: 33766147 PMCID: PMC7992345 DOI: 10.1186/s40851-021-00174-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 03/11/2021] [Indexed: 06/12/2023]
Abstract
INTRODUCTION Despite the growing number of studies describing digit ratio patterns in tetrapods, knowledge concerning certain basic issues is still scarce. In lower vertebrates such as tailless amphibians (Anura), the numbering of individual fingers on the forelimbs and their homology with the fingers of other vertebrates pose an unsolved problem. Based on reviewed data on anuran limb development, we argue that the correct finger numbering scheme should be based on the assumption that the first finger, not the fifth finger, was reduced on the forelimbs. We analyzed the digit ratio in the common toad (Bufo bufo, Bufonidae), a species characterized by well-developed sexual dimorphism whereby females are larger than males, using both numbering schemes present in the literature. RESULTS We found that the digit ratio on hindlimbs differed significantly between the sexes only in the cases of left 2D:3D, with lower digit ratios in females, and of left 3D:4D, with lower digit ratios in males. We found that sex was the only significant variable for forelimbs, differentiating 2D:3D on the left forelimb, with lower digit ratios in females; 2D:4D on the right forelimb, with lower digit ratios in males; and 3D:4D on both forelimbs, with lower digit ratios in males. These results relate to variant II reflecting the hypothesis that the first digit was reduced during phylogenesis. There was no relationship between the body size (SVL) of individuals and any digit ratio, excluding 2D:4D on the right forelimbs in models with age variables. Additionally, for a subset of data where individual age was known, the models indicated that age was linked to significant differences in 2D:4D and 3D:4D on the left hindlimbs, while age, SVL, and sex influenced 2D:4D on the right forelimbs. CONCLUSION We emphasize the importance of the problem of the correct numbering of forelimb digits in Anura and, under the assumption that it was the fifth digit that was reduced, argue that earlier results on digit ratio in this group should be interpreted with caution. The detected relationship between digit ratio and age in amphibians expands our knowledge, indicating that the age of individuals should be included in future digit ratio studies. This relationship may also apply to studies using digit ratio as a noninvasive indicator of endocrine disruption in amphibians.
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Affiliation(s)
- Mikołaj Kaczmarski
- Institute of Zoology, Poznań University of Life Sciences, Wojska Polskiego 71c, PL 60-625 Poznań, Poland
| | - Jan M. Kaczmarek
- Institute of Zoology, Poznań University of Life Sciences, Wojska Polskiego 71c, PL 60-625 Poznań, Poland
| | - Łukasz Jankowiak
- Institute of Biology, University of Szczecin, Wąska 13, PL 71-415 Szczecin, Poland
| | - Krzysztof Kolenda
- Amphibian Biology Group, Department of Evolutionary Biology and Conservation of Vertebrates, Institute of Environmental Biology, University of Wrocław, Sienkiewicza 21, PL 50-335 Wrocław, Poland
| | - Piotr Tryjanowski
- Institute of Zoology, Poznań University of Life Sciences, Wojska Polskiego 71c, PL 60-625 Poznań, Poland
- Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 00 Prague 6, Czech Republic
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Stibbard-Hawkes DNE. No Association between 2D:4D Ratio and Hunting Success among Hadza Hunters. HUMAN NATURE (HAWTHORNE, N.Y.) 2020; 31:22-42. [PMID: 31838723 DOI: 10.1007/s12110-019-09359-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The ratio of index- and ring-finger lengths (2D:4D ratio) is thought to be related to prenatal androgen exposure, and in many, though not all, populations, men have a lower average digit ratio than do women. In many studies an inverse relationship has been observed, among both men and women, between 2D:4D ratio and measures of athletic ability. It has been further suggested that, in hunter-gatherer populations, 2D:4D ratio might also be negatively correlated with hunting ability, itself assumed to be contingent on athleticism. This hypothesis has been tested using endurance running performance among runners from a Western, educated, and industrialized population as a proximate measure of hunting ability. However, it has not previously been tested among actual hunter-gatherers using more ecologically valid measures of hunting ability and success. The current study addresses this question among Tanzanian Hadza hunter-gatherers. I employ a novel method of assessing hunting reputation that, unlike previous methods, allows granular distinctions to be made between hunters at all levels of perceived ability. I find no statistically significant relationship between digit ratio and either hunting reputation or two important hunting skills. I confirm that Hadza men have higher mean 2D:4D ratios than men in many Western populations. I discuss the notion that 2D:4D ratio may be the consequence of an allometric scaling relationship between relative and absolute finger lengths. Although it is difficult to draw clear conclusions from these results, the current study provides no support for the theorized relationship between 2D:4D ratio and hunting skill.
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Lipshutz SE, George EM, Bentz AB, Rosvall KA. Evaluating testosterone as a phenotypic integrator: From tissues to individuals to species. Mol Cell Endocrinol 2019; 496:110531. [PMID: 31376416 PMCID: PMC6731036 DOI: 10.1016/j.mce.2019.110531] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 06/14/2019] [Accepted: 07/30/2019] [Indexed: 12/19/2022]
Abstract
Hormones have the potential to bring about rapid phenotypic change; however, they are highly conserved over millions of years of evolution. Here, we examine the evolution of hormone-mediated phenotypes, and the extent to which regulation is achieved via independence or integration of the many components of endocrine systems. We focus on the sex steroid testosterone (T), its cognate receptor (androgen receptor) and related endocrine components. We pose predictions about the mechanisms underlying phenotypic integration, including coordinated sensitivity to T within and among tissues and along the HPG axis. We then assess these predictions with case studies from wild birds, asking whether gene expression related to androgenic signaling naturally co-varies among individuals in ways that would promote phenotypic integration. Finally, we review how mechanisms of integration and independence vary over developmental or evolutionary time, and we find limited support for integration.
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Affiliation(s)
- S E Lipshutz
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA.
| | - E M George
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405, USA
| | - A B Bentz
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405, USA
| | - K A Rosvall
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA; Center for the Integrative Study of Animal Behavior, Indiana University, Bloomington, IN, 47405, USA
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Cain KE, Pryke SR. Testosterone production ability predicts breeding success and tracks breeding stage in male finches. J Evol Biol 2016; 30:430-436. [PMID: 27797442 DOI: 10.1111/jeb.13005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 10/25/2016] [Accepted: 10/26/2016] [Indexed: 11/29/2022]
Abstract
Testosterone (T) is an important mediator of reproductive behaviours and potential target for selection. However, there are few data relating natural variation in T to fitness estimates. Here, we used the GnRH challenge (an injection of gonadotropin-releasing hormone which stimulates maximal T release), to examine how individual differences in T relate to reproductive success and how T changes across date and breeding stage. We measured pre- and post-challenge T, in captive male Gouldian finches (Erythrura gouldiae), before and after introducing females, and across breeding stage. Post-challenge T before introducing females positively predicted breeding success. Post-challenge T levels were unrelated to date, but strongly related to stage; T production ability was strongly attenuated in incubating males. Prechallenge T levels related only to date. Our results suggest that T production ability is an important target for selection and that when males invest heavily in parental care they reduce their sensitivity to GnRH.
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Affiliation(s)
- K E Cain
- Research School of Biology, Australian National University, Canberra, ACT, Australia.,School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - S R Pryke
- Research School of Biology, Australian National University, Canberra, ACT, Australia
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Hasegawa M, Arai E. Female Attraction to Higher Pitched Male Enticement Calls in Barn Swallows. Ethology 2016. [DOI: 10.1111/eth.12492] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Masaru Hasegawa
- Department of Evolutionary Studies of Biosystems; Sokendai (The Graduate University for Advanced Studies); Miura-gun, Kanagawa Japan
| | - Emi Arai
- Division of Ecology and Evolutionary Biology; Graduate School of Life Sciences; Tohoku University; Aoba-ku, Sendai Japan
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Balogová M, Nelson E, Uhrin M, Figurová M, Ledecký V, Zyśk B. No Sexual Dimorphism Detected in Digit Ratios of the Fire Salamander (Salamandra salamandra). Anat Rec (Hoboken) 2015. [PMID: 26199217 DOI: 10.1002/ar.23197] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
It has been proposed that digit ratio may be used as a biomarker of early developmental effects. Specifically, the second-to-fourth digit ratio (2D:4D) has been linked to the effects of sex hormones and their receptor genes, but other digit ratios have also been investigated. Across taxa, patterns of sexual dimorphism in digit ratios are ambiguous and a scarcity of studies in basal tetrapods makes it difficult to understand how ratios have evolved. Here, we focus on examining sex differences in digit ratios (2D:3D, 2D:4D, and 3D:4D) in a common amphibian, the fire salamander (Salamandra salamandra). We used graphic software to measure soft tissue digit length and digit bone length from X-rays. We found a nonsignificant tendency in males to have a lower 2D:3D than females; however, no sexual differences were detected in the other ratios. We discuss our results in the context of other studies of digit ratios, and how sex determination systems, as well as other factors, might impact patterns of sexual dimorphism, particularly in reptiles and in amphibians. Our findings suggest that caution is needed when using digit ratios as a potential indicator of prenatal hormonal effects in amphibians and highlight the need for more comparative studies to elucidate the evolutionary and genetic mechanisms implicated in sexually dimorphic patterns across taxonomic groups.
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Affiliation(s)
- Monika Balogová
- Institute of Biology and Ecology, Faculty of Science, P. J. Šafárik University, Košice, Slovakia
| | - Emma Nelson
- School of Medicine, University of Liverpool, Liverpool, United Kingdom.,Archaeology, Classics and Egyptology, University of Liverpool, Liverpool, United Kingdom
| | - Marcel Uhrin
- Institute of Biology and Ecology, Faculty of Science, P. J. Šafárik University, Košice, Slovakia.,Department of Forest Protection and Wildlife Management, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Praha 6, Czech Republic
| | - Mária Figurová
- Clinic of Small Animals, University of Veterinary Medicine and Pharmacy, Košice, Slovakia
| | - Valent Ledecký
- Clinic of Small Animals, University of Veterinary Medicine and Pharmacy, Košice, Slovakia
| | - Bartłomiej Zyśk
- Department of Vertebrate Zoology and Human Biology, Institute of Biology, Cracow Pedagogical University, Kraków, Poland
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Costs and benefits of competitive traits in females: aggression, maternal care and reproductive success. PLoS One 2013; 8:e77816. [PMID: 24204980 PMCID: PMC3813731 DOI: 10.1371/journal.pone.0077816] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 09/04/2013] [Indexed: 11/23/2022] Open
Abstract
Recent research has shown that female expression of competitive traits can be advantageous, providing greater access to limited reproductive resources. In males increased competitive trait expression often comes at a cost, e.g. trading off with parental effort. However, it is currently unclear whether, and to what extent, females also face such tradeoffs, whether the costs associated with that tradeoff overwhelm the potential benefits of resource acquisition, and how environmental factors might alter those relationships. To address this gap, we examine the relationships between aggression, maternal effort, offspring quality and reproductive success in a common songbird, the dark-eyed junco (Junco hyemalis), over two breeding seasons. We found that compared to less aggressive females, more aggressive females spent less time brooding nestlings, but fed nestlings more frequently. In the year with better breeding conditions, more aggressive females produced smaller eggs and lighter hatchlings, but in the year with poorer breeding conditions they produced larger eggs and achieved greater nest success. There was no relationship between aggression and nestling mass after hatch day in either year. These findings suggest that though females appear to tradeoff competitive ability with some forms of maternal care, the costs may be less than previously thought. Further, the observed year effects suggest that costs and benefits vary according to environmental variables, which may help to account for variation in the level of trait expression.
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Cain KE, Ketterson ED. Individual variation in testosterone and parental care in a female songbird; the dark-eyed junco (Junco hyemalis). Horm Behav 2013; 64:685-92. [PMID: 24060498 PMCID: PMC4013145 DOI: 10.1016/j.yhbeh.2013.09.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 09/11/2013] [Accepted: 09/13/2013] [Indexed: 10/26/2022]
Abstract
When competition for sex-specific resources overlaps in time with offspring production and care, trade-offs can occur. Steroid hormones, particularly testosterone (T), play a crucial role in mediating such trade-offs in males, often increasing competitive behaviors while decreasing paternal behavior. Recent research has shown that females also face such trade-offs; however, we know little about the role of T in mediating female phenotypes in general, and the role of T in mediating trade-offs in females in particular. Here we examine the relationship between individual variation in maternal effort and endogenous T in the dark-eyed junco, a common songbird. Specifically, we measure circulating T before and after a physiological challenge (injection of gonadotropin releasing hormone, GnRH), and determine whether either measure is related to provisioning, brooding, or the amount of T sequestered in egg yolk. We found that females producing more T in response to a challenge spent less time brooding nestlings, but provisioned nestlings more frequently, and deposited more T in their eggs. These findings suggest that, while T is likely important in mediating maternal phenotypes and female life history tradeoffs, the direction of the relationships between T and phenotype may differ from what is generally observed in males, and that high levels of endogenous T are not necessarily as costly as previous work might suggest.
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Affiliation(s)
- Kristal E Cain
- Research School of Biology, The Australian National University, ACT 0200, Australia; Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Bloomington, IN 47405, USA.
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