Mating system and kin relationship between adults and young in the shell-brooding cichlid fish <Emphasis Type="Italic">Neolamprologus meeli</Emphasis> in Lake Tanganyika

Mating system and parental behavior of ten monogamous pairs and two polygynous groups of the Tanganyikan cichlid Neolamprologus meeli were observed in their natural habitat. The home ranges of males and females overlapped with each other. Most groups included one to six young. Paternal and maternal relationships were determined for 22 young from DNA microsatellite markers. Three types of kinship were found: (I) kinship to both the male and female; (II) kinship to females only; and (III) non-kinship to both sexes. In the groups with type II young, step-fathering or sneaking may have occurred. Type III young were larger than type I, suggesting that the former were of sufficient size to leave their birth nest and settle in the territories of foster parents. Both males and females drove out potential predators of young (including three species of Lepidiolamprologus) as a parental behavior. Adults with type III young attacked approaching predators with as much frequency as those with type I young only, indicating that they provided alloparental care. Adults and young swam together, but, a significant difference existed in the frequencies of interactions between adults versus kin young and adults versus non-kin young. The results suggest that both adults and young recognized kin. Electronic Publication     

Biparental mouthbrooding of the catfish Phyllonemus filinemus in Lake Tanganyika

This article reports biparental mouthbrooding of the bagrid catfish Phyllonemus filinemus in Lake Tanganyika, based on analysis of specimens collected during SCUBA diving. This catfish was nocturnally active, and in the daytime it was concealed singly or in pairs beneath rocks. Within a breeding pair, the male or female alone incubated all the brood in the mouth until the offspring attained 12 mm or so in total length, but thereafter joint mouthbrooding or guarding by both parents took place. Most females of nonbrooding pairs showed high values of gonadosomatic index (GSI), whereas all females of brooding pairs and most single females showed low GSI values. This fact indicated that a pair is formed at a time near the gonadal maturation of the female and separates after the brood is reared. No significant difference in body condition among parents of different reproductive states was observed, which suggested that their condition does not deteriorate markedly as the result of foraging by an off-duty parent. Received: September 16, 2000 / Revised: November 18, 2000 / Accepted: January 23, 2001     

Systematics of Tanganyikan cichlid fishes (Teleostei: Perciformes)

The relationships among 53 genera of Tanganyikan cichlid fishes were analyzed based on internal and external morphological features. Comparison of the morphological cladistic tree with a previously proposed classification showed 5 of 12 tribes to be nonmonophyletic. Sixteen tribes were recognized, the changes in classification being that Trematocarini was treated as a junior synonym of Bathybatini; 5 new tribes were established for each of the following genera, Benthochromis, Boulengerochromis, Ctenochromis benthicola, Cyphotilapia, and Greenwoodochromis; Ctenochromis horei was transferred from Haplochromini to Tropheini; and Gnathochromis pfefferi was transferred from Limnochromini to Tropheini. The revised classification was supported by previously proposed molecular trees.     

Intraspecific brood-mixing of the cichlid fishPerissodus microlepis in Lake Tanganyika

Synopsis The frequency and origin of intraspecific brood-mixing in the biparental cichlid fishPerissodus microlepis were investigated by the cohort analysis of schooling young and the underwater observation of guarding parents. The cohort analysis showed that brood-mixing started from the early guarding state when the young were smaller than 10 mm standard length and nearly all schools of young larger than 16 mm contained alien young from up to 6 broods. Brood farming-out of this fish, which was originally proposed to be a way adopted only by a deserted parent, was performed also by paired parents. We suggest that brood-mixing inP. microlepis is attributed mainly to brood farming-out by paired and deserted parents.     

Mating systems of two midwater-spawning cichlids,Cyprichromis microlepidotus andParacyprichromis brieni,in Lake Tanganyika

The breeding habits of 2 maternal mouthbrooding cichlids,Cyprichromis microlepidotus andParacyprichromis brieni, were investigated in Lake Tanganyika. Although spawning on the substrate in the male's mating territory is prevalent in maternal mouthbrooders, bothC. microlepidotus andP. brieni spawned in the water column. MaleC. microlepidotus established their mating territories in the open water column, while maleP. brieni did so around fixed spawning sites near a vertical rock surface. In both species, females visited male mating territories, departing soon after spawning and collecting the eggs. Sneaking, which was observed only inP. brieni, may be attributed to the presence of refuges for sneakers in this species. FemaleC. microlepidotus deposited their entire clutch of about 9 eggs in one male territory. In contrast, femaleP. brieni divided their clutch of about 11 eggs among several males. After the final egg-release, femaleC. microlepidotus repeatedly approached their mate, with the mouth near the abdomen of the latter (nuzzling), but femaleP. brieni often departed without nuzzling. Males may eject sperm during nuzzling to fertilize eggs inside the female's mouth. However, maleP. brieni is also known to eject sperm near spawning females when the females are not nuzzling. Such behavior seems to be a male countermeasure against female mate infidelity, because males could not ensure paternity of eggs by ejecting sperm only during female nuzzling.     

High frequency of multiple paternity in broods of a socially monogamous cichlid fish with biparental nest defence

In several animal taxa, genetic analyses have demonstrated that social monogamy and biparental brood care do not preclude polygamous reproduction. Few studies have been conducted in fish, but in fish species without alternative reproductive phenotypes, social monogamy was largely congruent with genetic parentage. In contrast to these findings, we report an exceptionally high level of multiple paternity in a socially monogamous cichlid fish with biparental nest defence ( Variabilichromis moorii ), inferred from microsatellite and mitochondrial data of 10 broods. Whereas all offspring in a nest shared a common mother, each brood was sired by 2 to > 10 males. None of the inferred sires was assigned a large proportion of the brood. Paternity was estimated as the minimum number of sires required to explain multilocus offspring genotypes, and as the maximum-likelihood number of sires given population allele frequencies. Analysis of simulated brood genotypes suggested that, although these two methods tend to under- and overestimate, respectively, the true number of sires, primary sires with many offspring in a brood would have been detected. Hence, the genetic data indicate that the nest tending males suffer substantial cuckoldry and provide alloparental care for a large number of unrelated fry. We have no data on the social status of the cuckolding males, but due to synchronous spawning of pairs and commitment to brood care of paired males, it is possible that most of the parasitic spawners are solitary males.     

Where Am I? Niche constraints due to morphological specialization in two Tanganyikan cichlid fish species

Food resource specialization within novel environments is considered a common axis of diversification in adaptive radiations. Feeding specializations are often coupled with striking morphological adaptations and exemplify the relation between morphology and diet (phenotype–environment correlations), as seen in, for example, Darwin finches, Hawaiian spiders, and the cichlid fish radiations in East African lakes. The cichlids' potential to rapidly exploit and occupy a variety of different habitats has previously been attributed to the variability and adaptability of their trophic structures including the pharyngeal jaw apparatus. Here we report a reciprocal transplant experiment designed to explore the adaptability of the trophic structures in highly specialized cichlid fish species. More specifically, we forced two common but ecologically distinct cichlid species from Lake Tanganyika, Tropheus moorii (rock‐dweller), and Xenotilapia boulengeri (sand‐dweller), to live on their preferred as well as on an unpreferred habitat (sand and rock, respectively). We measured their overall performance on the different habitat types and explored whether adaptive phenotypic plasticity is involved in adaptation. We found that, while habitat had no effect on the performance of X. boulengeri, T. moorii performed significantly better in its preferred habitat. Despite an experimental duration of several months, we did not find a shift in the morphology of the lower pharyngeal jaw bone that would be indicative of adaptive phenotypic plasticity in this trait.     

Reproductive success in female Neolamprologus mondabu (Cichlidae): influence of substrate types

Individual variation in body size, home range size, and reproductive success among Neolamprologus mondabu (Cichlidae) females were investigated with reference to substrate types in the littoral zone of northern Lake Tanganyika. Larger females occupied sandy substrates and smaller ones stony substrates. Female reproductive success, estimated as the number of offspring successfully released per month, was higher on sandy substrates than on stony substrates. This may be attributable to higher spawning intensity and better protection of broods against predators in open, sandy habitats.     

Intestinal coiling pattern in the epilithic algal-feeding cichlids (Pisces, Teleostei) of Lake Tanganyika, and its phylogenetic significance

This paper suggests that, on the basis of ontogenetic change in intestinal coiling pattern, four types and four subtypes could be recognized within 20 species of epilithic algal-feeding cichlids in Lake Tanganyika. The phylogenetically useful anatomical features characterizing each type are as follows. Petrochromis type: torsion of the intestinal tract generally occurs at Stage 5 Intersecting Point (IP), and the haplochromine loop and a two-loop coiling system are observable. Cyathopharynx type: the value of IP becomes 7 before torsion occurs, and the coiling system changes qualitatively from one-loop to two-loop types. Asprotilapia type: torsion occurs at Stage 5 IP, and a one-loop coiling system is retained throughout ontogeny. Telmatochromis type: no torsion occurs, and a one-loop coiling system is retained throughout ontogeny. Within the Petrochromis type, each of the four subtypes is characterized by the following features. Petrochromis subtype: the rostrally directed haplochromine loop has its rostral part situated to the right side of the stomach in the adult stage. Pseudosimochromis subtype: a circular haplochromine loop is present. Eretmodus subtype: the haplochromine loop tends to be prolonged and bends through 90 or 180 further counter-clockwise. Tropheus subtype: torsion occurs at Stage 7 IP.     

Sperm size of African cichlids in relation to sperm competition

We compared pairs of closely related taxa of cichlid fishesfrom Lake Tanganyika to examine the relationship between spermsize and the presumed intensity of sperm competition. In contrastto previous reports of relatively short sperm in polygamousfishes across a variety of taxa, we found that polygamous cichlidshad significantly longer sperm than their closest monogamousrelatives. In addition, sperm length was significantly relatedto relative testis size (controlling for body size and phylogeny).The site of fertilization may also be correlated with spermlength, as species that fertilize in the female's buccal cavityhad significantly shorter sperm than those that fertilizedeggs on the substrate. Assuming that relatively large testesand polygamous mating are indicative of more intense sperm competition, these results indicate that sperm length is related to the intensityof sperm competition in this clade of cichlids, as has beenfound previously in insects, birds, and mammals.     

Helping opportunities and space segregation in cooperatively breeding cichlids

Studies of cooperative breeding have largely ignored the roleof conflict among helpers and how it shapes group dynamics andhelping behavior. In the present study, performing laboratoryexperiments with cooperatively breeding cichlids from Lake Tanganyika,we show that secondary group members (potential helpers) occupyhome ranges within the group territory and may be aggressiveto one another. Experimental removal of secondary group membersallowed the individual next in rank to move closer to the removedindividual's home range. In the field, dominant secondary groupmembers stayed closer to the brood chamber than did subordinategroup members of similar size, and proximity to the brood chamberwas related to the length of time spent inside. We suggest thatspace segregation and competition among secondary group membersis common in these cichlids, and may limit the opportunitiesto provide help.     

Male reproductive suppression in the cooperatively breeding fish Neolamprologus pulcher

In most cooperative breeders, dominants suppress the reproductionof subordinates. However, two previous studies of Neolamprologuspulcher, a cooperatively breeding cichlid fish, have suggestedthat socially subordinate helper males sneak fertilizationsfrom dominant breeding males. If such sneaking does occur, boththeoretical work and empirical studies of other fish speciessuggest that sperm competition will select for increased reproductiveinvestment by sneaker males, relative to more dominant males.To address these issues, we quantified gonadal investment andsperm characteristics of 41 N. pulcher male breeders and 62male helpers from 55 groups in Lake Tanganyika. Gonadal investmentfollowed patterns consistent with reproductive suppression,with breeders having considerably larger testes masses thanhelpers. Breeders also had faster and longer swimming spermand a higher percentage of motile sperm compared to helpers.However, sperm characteristics of large helpers were similarto those of breeders, but these same helpers had lower testesmasses. Thus, large helpers had sperm that were physiologicallyequivalent to that of breeders, but their relatively small gonadsimply that they were reproductively suppressed.     

Farming-out of offspring is a predominantly male tactics in a biparental mouthbrooding cichlid <Emphasis Type="BoldItalic">Perrisodus mircolepis</Emphasis>

Synopsis Intraspecific brood-mixing of a Tanganyikan biparental cichlid fish Perissodus microlepis has been attributed to farming-out, a behaviour in which a parent transport some or all of their free-swimming young in the mouth and put them under the care of other guarding parents. We conducted observations under natural conditions to understand how often farming-out occurs and which sex is the primary performer. At most brooding sites, young in a school entirely disappeared before attaining to the size of independence. At many of these sites, farming-out and its precursory behaviours by males preceded disappearance of their young. Females never performed farming-out. We proposed that farming-out by males is an alternative tactics to brood desertion to evade paternal roles for remating.     

Food intake by mouthbrooding females ofCyphotilapia frontosa (Cichlidae) to feed both themselves and their young

Synopsis Feeding behaviour of mouthbrooding females ofCyphotilapia frontosa was observed in their natural habitat, and specimens of mouthbrooding females and the young in their mouths were examined in the laboratory. Mouthbrooding females exhibited feeding actions and their guts contained about one quarter as much food as those of nonbrooding adults. A substantial amount of food was found in young 12.5 mm TL who retained a large quantity of yolk, and gut fullness of young increased as they grew. Weight changes of the young suggested that the buccal feeding augmented their growth.