Consumption of carotenoids not increased by bacterial infection in brown trout embryos (Salmo trutta)

Abstract

These authors contributed equally to this work. AbstractCarotenoids are organic pigment molecules that play important roles in signalling, control of oxidative stress, and immunity. Fish allocate carotenoids to their eggs, which gives them the typical yellow to red colouration and supports their resistance against microbial infections. However, it is still unclear whether carotenoids act mainly as a shield against infection or are used up during the embryos' immune defence. We investigated this question with experimental families produced from wild-caught brown trout (Salmo trutta). Singly raised embryos were either exposed to the bacterial pathogen Pseudomonas fluorescens or shamtreated at one of two stages during their development. A previous study on these experimental families reported positive effects of egg carotenoids on embryo growth and resistance against the infection. Here, we quantified carotenoid consumption in these infected and sham-infected maternal sib groups. We found that carotenoid contents mostly decreased during embryogenesis. However, these decreases were neither linked to the virulence induced by the pathogen nor dependent on the time point of infection. We conclude that egg carotenoids are not significantly used up by the embryos' immune defence.

Low adaptive potential for tolerance to ethynylestradiol, but also low toxicity, in a grayling population (Thymallus thymallus)

“…In salmonids, maternal environmental effects comprises characteristics such as egg size [50] and compounds that females allocate to their eggs [e.g. 47,[48][49][50][51]. We found strong direct maternal effects on every offspring trait that we measured, and a dam x EE2 interaction on the timing of hatching.…”

“…Time to emergence, and body size at emergence, is likely to be linked to fitness in salmonids because larvae that emerge earlier and larger than others may face less competition for resources (e.g. feeding territory) and are more prone to outcompete their late emerging counterparts [50,51].…”