Through a glass darkly? Divergent reactions of eight Lake Tanganyika cichlid species towards their mirror image in their natural environment

Behavioural reactions towards a mirror image are frequently used to measure individual aggression in a standardized way, especially in fishes. However, this approach was criticized recently on several grounds. One point of concern is that mirror tests are often conducted under highly artificial laboratory settings, while there exists a lack of knowledge of how individuals will react towards their reflection in the wild. We measured the responses of eight sympatric lamprologine cichlid species towards their mirror images in their natural environment in Lake Tanganyika. All species reacted by showing aggression towards their mirror image. The occurrence of overt and restrained aggression varied between species, reflecting species-specific aggressive behaviours. The finding that larger species showed a higher amount of overt attacks further supports this interpretation. A commonality across all species was that aggression escalated over time, resembling behavioural patterns during prolonged aggressive encounters between life opponents with similar resource holding potential. These results shed light on the behaviour of closely related fish species towards their mirror image under natural conditions and contribute knowledge to the ongoing discussion on the suitability of mirror tests when measuring aggression

The Ursinus Weekly, October 6, 1966

Cultural opportunities abound at U.C. during 1966: Art exhibit • Orientation brings return of the dink: Red and gold revived on the U.C. scene • U.C. hosts parents on October 8 • Politics main theme of Forums • Record enrollment • NSA tests open to upperclassmen • Academy of Music sponsors student concerts • Luxurious new dorms opened • Editorial • Frosh meet challenge of matriculation blues • Letters to the editor • Book review • What\u27s in a name? You\u27d be amazed! • New cars, big engines in news • Wilkinson\u27s inmates undismayed by unfinished state of dorm • Booters strive for coherence, consistency • Bears impress in scoreless opener • Youthful gridders much improved since 1965 • Gurzynski\u27s runners face Eastern Baptist Friday • Fall hockey preview: Loss of strong line players leaves gaps • Greek gleaningshttps://digitalcommons.ursinus.edu/weekly/1191/thumbnail.jp

Age‐ and sex‐dependent variation in relatedness corresponds to reproductive skew, territory inheritance and workload in cooperatively breeding cichlids

Kin selection plays a major role in the evolution of cooperative systems. However, many social species exhibit complex within-group relatedness structures, where kin selection alone cannot explain the occurrence of cooperative behavior. Understanding such social structures is crucial to elucidate the evolution and maintenance of multi-layered cooperative societies. In lamprologine cichlids, intragroup relatedness seems to correlate positively with reproductive skew, suggesting that in this clade dominants tend to provide reproductive concessions to unrelated subordinates to secure their participation in brood care. We investigate how patterns of within-group relatedness covary with direct and indirect fitness benefits of cooperation in a highly social vertebrate, the cooperatively breeding, polygynous lamprologine cichlid Neolamprologus savoryi. Behavioral and genetic data from 43 groups containing 578 individuals show that groups are socially and genetically structured into subgroups. About 17% of group members were unrelated immigrants, and average relatedness between breeders and brood care helpers declined with helper age due to group membership dynamics. Hence the relative importance of direct and indirect fitness benefits of cooperation depends on helper age. Our findings highlight how both direct and indirect fitness benefits of cooperation and group membership can select for cooperative behavior in societies comprising complex social and relatedness structures

Experimental predator intrusions in a cooperative breeder reveal threat-dependent task partitioning

In cooperatively breeding species, nonbreeding individuals provide alloparental care and help in territory maintenance and defense. Antipredator behaviors of subordinates can enhance offspring survival, which may provide direct and indirect fitness benefits to all group members. Helping abilities and involved costs and benefits, risks, and outside options (e.g., breeding independently) usually diverge between group members, which calls for status-specific differentiated behavioral responses. Such role differentiation within groups may generate task-specific division of labor, as exemplified by eusocial animals. In vertebrates, little is known about such task differentiation among group members. We show how breeders and helpers of the cooperatively breeding cichlid Neolamprologus savoryi partition predator defense depending on intruder type and the presence of dependent young. In the field, we experimentally simulated intrusions by different fish species posing a risk either specifically to eggs, young, or adults. We used intrusions by harmless algae eaters as a control. Breeders defended most when dependent young were present, while helper investment hinged mainly on their body size and on the potential threat posed by the respective intruders. Breeders and helpers partitioned defense tasks primarily when dependent young were exposed to immediate risk, with breeders investing most in antipredator defense, while helpers increased guarding and care in the breeding chamber. Breeders' defense likely benefits helpers as well, as it was especially enhanced in the treatment where helpers were also at risk. These findings illustrate that in a highly social fish different group members exhibit fine-tuned behavioral responses in dependence of ecological and reproductive parameter variation

Sex-specific routes to independent breeding in a polygynous cooperative breeder

How can individuals obtain a breeding position and what are the benefits associated with philopatry compared to dispersal? These questions are particularly intriguing in polygamous cooperative breeders, where dispersal strategies reflect major life history decisions, and routes to independent breeding may utterly differ between the sexes. We scrutinized sex-dependent life-history routes by investigating dispersal patterns, growth rates and mortality in a wild colony of the cooperatively breeding cichlid Neolamprologus savoryi. Our data reveal that female helpers typically obtain dominant breeding positions immediately after reaching sexual maturity, which is associated with strongly reduced growth. In contrast, males obtain breeder status only at twice the age of females. After reaching sexual maturity, males follow one of two strategies: (i) they may retain their subordinate status within the harem of a dominant male, which may provide protection against predators but involves costs by helping in territory maintenance, defence and brood care; or (ii) they may disperse and adopt a solitary status, which diminishes survival chances and apparently reflects a best-of-a-bad-job strategy, as there are no obvious compensating future fitness benefits associated with this pathway. Our study illustrates that sex-dependent life history strategies strongly relate to specific social structures and mating patterns, with important implications for growth rates, the age at which breeding status is obtained, and survival

Ecological variation drives morphological differentiation in a highly social vertebrate

Animals may respond to ecological heterogeneity by genetic differentiation or phenotypic plasticity. Responses of organisms to their ecology can include adaptation at various levels of organization, including morphology, behaviour and social structure. Adaptations at one level might constrain or enhance adaptations on other levels, which highlights the importance of understanding their interactions. In highly social animals, understanding the influence of their ecological niche on the evolution and maintenance of complex social organization poses an intriguing challenge. Predation risk and habitat characteristics determine social structure in the cooperatively breeding cichlid Neolamprologus pulcher. Here we examine how varying combinations of these ecological factors across eight distinct populations influence morphological differentiation. We investigated the relationship between body shape and ecological parameters for 137 wild-caught individuals from eight distinct populations. Furthermore, we examined the genetic structure and differentiation among these populations using microsatellites. Finally, to disentangle heritable from plastic responses, we raised two successive generations from six populations in the laboratory under common garden conditions and screened 188 individuals for morphological differentiation. We found that body shape of N. pulcher strongly correlates with the measured ecological parameters. Low predation risk, low habitat structure and small shelter size favoured shallow bodies, whereas at the opposite end of these environmental gradients deep body shapes prevail. These consistent morphological differences persisted over two laboratory-reared generations, revealing a heritable basis. In contrast to the significant effect of local ecology on morphological differentiation between populations, both geographical and genetic distance had little explanatory power, suggesting that morphological differentiation between populations is not a simple by-product of genetic isolation. Remarkably, the largest difference in body depth emerged between the two populations located closest to each other, but differing strongly in their ecological niche. These results highlight that morphological variation is a key component of local adaptation in neighbouring populations of a highly social species. Such morphological differentiation has the potential to influence individual cooperative behaviour, which will eventually feed back on group structure and mediate the evolution and maintenance of complex social systems

First field evidence for alloparental egg care in cooperatively breeding fish

Helping behaviour in cooperative breeders has been intensively studied in many animal taxa, including arthropods, birds and mammals. In these highly social systems, helpers typically engage in brood care and the protection of dependent young. Such helping systems also exist in cooperatively breeding cichlid species of Lake Tanganyika. However, breeding in these species happens in clefts, narrow holes or shelters underneath stones. Therefore, direct brood care by breeders and helpers has thus far only been observed under artificial laboratory conditions. Under natural conditions, brood care behaviour has been estimated indirectly by determining the time spent in the breeding chamber, or by the number of visits to the breeding chamber. The reliability of such substitutes needs to be validated, for instance, by demonstrating alloparental egg care of helpers through direct observations in nature. Here, we describe direct egg care by a male helper of the cooperatively breeding cichlid Neolamprologus savoryi in the field. The helper inspected and cleaned the eggs and defended them against predators. By reconstructing the genetic relatedness using microsatellite markers, we show that the helper was the son of the breeding male, but unrelated to the breeding female. The genetic mother of the helper was defending a different territory next to the one where the helper showed alloparental egg care. This indicates that the helper had dispersed inside the male territory to assist another female to care for his half‐siblings. These results demonstrate alloparental egg care without reproductive share in a fish species under natural conditions, underlining that helping behaviour in cooperatively breeding fish has a strong non‐self‐serving component

Investment of group members is contingent on helper number and the presence of young in a cooperative breeder

In cooperatively breeding societies dominant breeders are assisted by other individuals in raising their young. In many of these species helping behaviours and their benefits for breeders have been studied by investigating the helpers' contribution to direct offspring care, even though a significant proportion of help is not targeted specifically to offspring. Here, we investigated how breeders and helpers share the effort in shelter maintenance and how their investment is influenced by the presence of dependent young in the cooperatively breeding cichlid Neolamprologus savoryi. Shelters provide essential protection from predators, independently of a group's breeding status. Shelter maintenance is costly in terms of time investment and energy expenditure. In the field we manipulated the workload of groups that differed in the presence and number of helpers and the reproductive state of breeders by increasing the need for digging out the breeding shelter. Helper presence correlated with workload reduction of dominant females, even in the absence of dependent young. This emphasizes the importance of shelters for the whole group, independently of the current reproductive status of the breeding pair. The described benefits increased with the number and body size of the helpers. Additionally, breeding females and helpers visited the breeding chamber more often if young were present, and helper presence enhanced the reproductive success of breeders. These findings highlight the importance of studying the role of helpers and their benefits to breeders not only in the context of direct brood care, but also for other cooperative tasks, in order to understand the evolution of complex animal societies