Growth and social behavior in a cichlid fish are affected by social rearing environment and kinship

Abstract

Living in groups is a widespread phenomenon in many animal taxa. The reduction of predation risk is thought to be an important cause for the formation of groups. Consequently, grouping behavior is particularly pronounced during vulnerable life stages, i.e., as juveniles. However, group living does not only provide benefits but also imposes costs on group members, e.g., increased competition for food. Thus, benefits of grouping behavior might not be evident when predation risk is absent. The adaptive significance of living and also developing in a group independent from predation risk has received relatively little attention although this might have important implications on the evolution and maintenance of group living. The first aim of the present study was to examine whether the social environment affects juvenile performance in the cichlid fish Pelvicachromis taeniatus and, secondly, whether kinship affects social behavior. Kin selection theory predicts benefits from grouping with kin. Here, we demonstrate that juveniles reared in a group grow on average faster compared to juveniles reared in isolation under standardized laboratory conditions without predation risk. Furthermore, we found significant differences in social behavior between juveniles reared in a group and reared in isolation. Fish reared in isolation were significantly more aggressive and less willing to shoal than group-reared fish. As expected, genetic relatedness influenced social behavior in group-reared fish as well: dyads of juveniles consisting of kin showed increased group cohesiveness compared to non-kin dyads. We discuss the potential benefits of group living in general and living with kin in particular.

Kinship reinforces cooperative predator inspection in a cichlid fish

“…Still, the adaptive significance is often ambigous. Benefits of grouping with kin are suggested to include improved responses to predators (Hain & Neff, 2009) and increased shoal cohesion (Hesse & Th€ unken, 2014), increased growth rates (Gerlach et al, 2007;Th€ unken et al, 2015) and less aggression (Olsen et al, 1996). Still, other studies did not describe such advantages (e.g.…”

“…Our study animal, Pelvicachromis taeniatus , is a small biparental cichlid fish capable of recognizing kin through phenotype matching (Thünken et al ., ; Hesse et al ., ; Thünken et al ., ). Juveniles form loose shoals in nature (Lamboj, ) and under laboratory conditions, and kin forms denser shoals than nonkin (Hesse & Thünken, ). Furthermore, juveniles engage in predator inspection behaviour (Hesse et al ., ).…”

Phenotype Matching and Early Social Conditions Affect Shoaling and Exploration Decisions

“…However, while the role of early social conditions in shaping social behaviour is recognized (Kaiser & Sachser ), how social changes during ontogeny influences the process of recognition and consequently how it affects behavioural decision‐making process remains limited (Barbosa et al. ; Hesse & Thünken ; Hesse et al. ).…”

“…It is during the early life stages that by observing and interacting with others, juveniles acquire the ability to recognize and discriminate between related, familiar and unfamiliar individuals (Quinn & Hara 1986;Emlen 1997). However, while the role of early social conditions in shaping social behaviour is recognized (Kaiser & Sachser 2005), how social changes during ontogeny influences the process of recognition and consequently how it affects behavioural decisionmaking process remains limited (Barbosa et al 2013;Hesse & Th€ unken 2014;Hesse et al 2015). Here we address this gap and ask how changes to social conditions during ontogeny affect the propensity to associate with same population conspecifics, and with familiar or unfamiliar individuals, in a novel environment.…”

Evolution of alarm cues: a test of the kin selection hypothesis

“…Afterwards they live in shoals without defined territories throughout the juvenile stage 68 . Laboratory experiments showed that they prefer to shoal with familiar kin (TT, Saskia Hesse, Theo C. M. Bakker, SAB, unpublished data) and that kin form tighter shoals 83 . Furthermore, P. taeniatus prefers to mate with kin 69 which is most likely also true for the natural population 84 .…”