Immune challenge affects reproductive behaviour in the guppy (Poecilia reticulata)

Abstract

Immunocompetence and reproduction are among the most important determinants of fitness. However, energetic and metabolic constraints create conflict between these two life-history traits. While many studies have explored the relationship between immune activity and reproductive fitness in birds and mammals inoculated with bacterial endotoxin, very few have focused on fish. Fish have been neglected in this area due, in part, to the claim that they are largely resistant to the immune effects of endotoxins. However, the present study suggests that they are susceptible to significant effects with respect to reproductive behaviour. Here, we examined the reproductive behaviour of male guppies following exposure to bacterial lipopolysaccharides (LPS) in comparison to that of male guppies in a control treatment. Additionally, we investigated the responses of females to these males. We show that although immune challenge does not suppress general activity in male guppies, it significantly reduces mating effort. While females showed no difference in general activity as a function of male treatments, they did exhibit reduced group cohesion in the presence of LPS-exposed males. We discuss this in the context of sickness behaviours, social avoidance of immune-challenged individuals and the effects of mounting an immune response on reproductive behaviour.

Sex-dependent effects of infection on guppy reproductive fitness and offspring parasite resistance

“…Previous work has shown that Gyrodactylus spp. infection (Kennedy et al, 1987;López, 1998López, , 1999 and immune challenges (Encel et al, 2023) affect guppy reproductive behaviour and, consistent with this explanation, the heaviest infected males appear more interested in contact with females (Stephenson, 2019). This behavioural explanation may be a component of a broader explanation that fathers who become heavily infected may generally have a faster pace of life.…”

Associating with kin selects for disease resistance and against tolerance

“…Guppies may associate with kin as juveniles in the laboratory [ 51 ] and the wild [ 33 ] but they do not as adults [ 51 , 52 ]. Further, uninfected and infected hosts can differ in their behavioural resistance [ 3 ] as infected guppies may seek contact [ 3 , 53 ] while uninfected guppies may avoid contact [ 46 , 54 , 55 ], potentially reducing overall rates of social contact [ 55 ]. Thus, this focal system provides empirically derived parameter values as well as empirical motivation for model ingredients like weak kin association and infection-class differences in behavioural resistance.…”

Associating with kin selects against disease tolerance

“…Juvenile guppies show some ability to detect kin in laboratory conditions [45] and wild populations vary in whether juveniles are disproportionately related to their shoalmates [27] but wild adults are not disproportionately related to their shoalmates [45, 46]. Further, uninfected and infected hosts can differ in their behavioural resistance [3] as infected guppies may seek contact [3, 47] while uninfected guppies may avoid contact [40, 48, 49], potentially reducing overall rates of social contact [49]. Thus, this focal system provides empirically-derived parameter values as well as empirical motivation for model ingredients like weak kin association and infection-class differences in behavioural resistance.…”