Mating system and kin relationship between adults and young in the shell-brooding cichlid fish Neolamprologus meeli in Lake Tanganyika

Fight, fatigue, and flight: narrowing of attention to a threat compensates for decreased anti-predator vigilance

Fighting carries predation risk because animals have limited attention, constraining their ability to simultaneously engage in aggression and anti-predator vigilance. However, the influence of interspecific aggression and fatigue on the predation cost of fighting is seldom examined, although both are unignorable aspects of fighting. Here, I incorporated both factors in a series of field experiments on the cichlid Lamprologus ocellatus. If territorial males respond more strongly to conspecific territorial intruders than heterospecific intruders, then they should delay escape more frequently during intraspecific fighting than interspecific fighting. Consequently, although I predict that vigilance would be decreased as fighting progresses in both fighting, intraspecific aggression should decrease vigilance more than interspecific aggression. Males were also exposed to a predator approaching at different (slow or fast) speeds during these fighting bouts. Delays in predator detection and flight initiation were quantified and these predictions were tested. As predicted, males were responded more strongly to intraspecific intruders, resulting in slower predator detection and fleeing times than when encountering interspecific intruders. Furthermore, flight latency decreased with increasing fight duration, suggesting that fatigue negatively influenced escape responses. However, contrary to prediction, the vigilance decrement rate was faster in response to slow predators than to rapid predators, and was not influenced by intruder identity. This suggests that fighting males reserve their attention for information critical to their survival and are less vigilant toward a less-threatening (slow approaching) predator. This cognitive allocation may be an adaptive compensation for fatigue-related low vigilance during fighting.

Same school, different conduct: rates of multiple paternity vary within a mixed-species breeding school of semi-pelagic cichlid fish (Cyprichromis spp.)

Mating system variability is known to exist between and within species, often due to environmental influences. An open question is whether, vice versa, similar environmental conditions entail congruent mating behavior, for example in terms of multiple paternity, in species or populations sharing largely comparable breeding modes. This study employed microsatellite markers to investigate the incidence of multiple paternity in Cyprichromis coloratus and Cyprichromis leptosoma, two sympatric, closely related, mouthbrooding Lake Tanganyika cichlids with similar ecological and behavioral characteristics including the formation of open‐water schools. Mouthbrooding females of both species were collected from the same mixed‐species breeding school at the same time, minimizing environmental variation during courtship and mating. In C. coloratus, four of 12 broods had more than one sire, with a mean of 1.33 reconstructed sires per brood. C. leptosoma exhibited multiple paternity in 18 of 22 broods, with a mean of 2.59 or 2.86 reconstructed sires per brood according to the programs gerud and colony, respectively. In addition, two broods were found to contain offspring transplanted from another brood. There was no significant difference in brood size between species, but mean sire number did differ significantly. Hence, substantial similarity in reproductive behavior along with shared environmental conditions during courtship and spawning did not lead to equal rates of polyandry or sneaking in the two species.

Non-random brood mixing suggests adoption in a colonial cichlid

Parental care of unrelated offspring is widespread but not well understood. We used 11 polymorphic microsatellite loci to investigate the relatedness of fry and parentally caring adults in a 118-nest colony of the socially and genetically monogamous cichlid fish Neolamprologus caudopunctatus in Lake Tanganyika. There was a high proportion of brood mixing, with 59% of 32 broods containing fry unrelated to both parents, and 18% of all 291 sampled fry being unrelated to the breeding pair. There was no evidence of kin selection for adoption because the genetic and foster parents were not more related than expected by chance. Parentage was assigned to 12 adopted fry from 10 broods. Distances traversed by fry varied markedly, from less than one to over 40 meters. The larger distances suggest that at least some brood mixing was instigated by parents transporting portions of their broods in their mouths, as occurs in some cichlids. Further evidence of non-random brood mixing was that foreign fry did not differ in size from their foster siblings within broods, even though they were significantly larger than fry produced by the tending pairs within the colony. These findings suggest that at least some foreign fry had dispersed non-randomly and were adopted by their foster parents. Enlarged broods are known to provide reduced per capita predation, making it potentially adaptive for breeders to adopt unrelated offspring.

Alternative Reproductive Tactics in the Shell-Brooding Lake Tanganyika Cichlid Neolamprologus brevis

Alternative reproductive tactics (ARTs) are found in several Lake Tanganyika shell-brooding cichlids. Field studies were conducted in the Wonzye population to examine reproductive ecology and ARTs in the Lake Tanganyika shell-brooding cichlid Neolamprologus brevis. We discovered that this fish occurred in both rocky- and sandy-bottom habitats, but in rocky habitats, brood-caring females exclusively occurred in shell-patches that another cichlid species created. All N. brevis of both sexes in the patches were sexually mature, whereas immature males and females with unripe eggs were found frequently in sandy-bottom habitats. Males in sandy-bottom habitats were smaller, but fed more frequently and were in better somatic condition than males in the patches. Similar tendency was found in females. This indicates that N. brevis uses different habitats depending on the stage of its life history, with migration from sandy-bottom habitats to the shell-patches for reproduction. Males in the patches exhibited different behavior patterns: floating above the patches and lying in the patches. The former was larger, more aggressive, and invested less in gonads (relative to body size) than the latter. These results accord with those of other shell-brooding Lake Tanganyika cichlids with ARTs, and they therefore suggest the presence of ARTs in N. brevis.

Mating and Parental Care in Lake Tanganyika's Cichlids

Cichlid fishes of Lake Tanganyika display a variety of mating and parental care behaviors, including polygamous and monogamous mouthbrooding and substrate breeding, cooperative breeding, as well as various alternative reproductive tactics such as sneaking and piracy. Moreover, reproductive behaviors sometimes vary within species both in space and in time. Here, I survey reports on mating and parenting behaviors of Lake Tanganyika cichlid species and address the evolution of mating and parental care patterns and sexual dimorphism. Notes on measures of sexual selection intensity and the difficulties of defining mating systems and estimating selection intensities at species level conclude the essay.

Evolutionary history of the Lake Tanganyika cichlid tribe Lamprologini (Teleostei: Perciformes) derived from mitochondrial and nuclear DNA data

Lake Tanganyika comprises a cichlid species flock with substrate-breeding and mouthbrooding lineages. While sexual selection via mate choice on male mating color is thought to boost speciation rates in mouthbrooding cichlids, this is not the case in substrate-breeding lamprologines, which mostly form stable pairs and lack sexual dichromatism. We present a comprehensive reconstruction of the evolution of the cichlid tribe Lamprologini, based upon mtDNA sequences and multilocus nuclear DNA (AFLP) markers. Twelve mtDNA clades were identified, seven of which were corroborated by the AFLP tree. The radiation is likely to have started about 5.3 MYA, contemporarily with that of the mouthbrooding C-lineage, and probably triggered by the onset of deep-water conditions in Lake Tanganyika. Neither the Congo- nor the Malagarazi River species form the most ancestral branch. Several conflicts in the mtDNA phylogeny with taxonomic assignments based upon color, eco-morphology and behavior could be resolved and complemented by the AFLP analysis. Introgressive hybridization upon secondary contact seems to be the most likely cause for paraphyly of taxa due to mtDNA capture in species involving brood-care helpers, while accidental hybridization best explains the para- or polyphyly of several gastropod shell breeders. Taxonomic error or paraphyly due to the survival of ancestral lineages appear responsible for inconsistencies in the genera Lamprologus and Neolamprologus.

Alternative male mating tactics of the substrate brooding cichlid Telmatochromis temporalis in Lake Tanganyika

Telmatochromis temporalis is a bi-parental substrate brooding cichlid endemic to Lake Tanganyika. Paired males were always larger than their mates and had territories around nests against conspecific males. However, males smaller than the paired females were found in 18% of the nests. Here we report a reproductive tactic of these small males. The small males had as heavy gonads as paired males, and the gonad somatic index (GSI) of the small males was much higher than that of the latter. The examinations of the paternity and maternity using microsatellite-DNA as a genetic marker revealed that the small males were not genetically related to the pair members, and sired some young in 3 of 5 nests. These small males did not guard the broods, suggesting that they are likely to perform reproductive parasitism as sneakers. Paired males could not enter their spawning nests due to their large size, which made it difficult to chase out sneakers once they entered the nest. Some males as small as the sneakers were found outside the territories of paired males, and their gonads were quite small. Circumstantial evidence suggests that small males have two alternative investment patterns: investing in gonad to be sneakers, and investing in growth to probably be territorial males.