Contextual modulation of social and endocrine correlates of fitness: insights from the life history of a sex changing fish

Abstract

Steroid hormones are critical regulators of reproductive life history, and the steroid sensitive traits (morphology, behavior, physiology) associated with particular life history stages can have substantial fitness consequences for an organism. Hormones, behavior and fitness are reciprocally associated and can be used in an integrative fashion to understand how the environment impacts organismal function. To address the fitness component, we highlight the importance of using reliable proxies of reproductive success when studying proximate regulation of reproductive phenotypes. To understand the mechanisms by which the endocrine system regulates phenotype, we discuss the use of particular endocrine proxies and the need for appropriate functional interpretation of each. Lastly, in any experimental paradigm, the responses of animals vary based on the subtle differences in environmental and social context and this must also be considered. We explore these different levels of analyses by focusing on the fascinating life history transitions exhibited by the bi-directionally hermaphroditic fish, Lythrypnus dalli. Sex changing fish are excellent models for providing a deeper understanding of the fitness consequences associated with behavioral and endocrine variation. We close by proposing that local regulation of steroids is one potential mechanism that allows for the expression of novel phenotypes that can be characteristic of specific life history stages. A comparative species approach will facilitate progress in understanding the diversity of mechanisms underlying the contextual regulation of phenotypes and their associated fitness correlates.

Ancestral androgenic differentiation pathways are repurposed during the evolution of adult sexual plasticity

“…and Grober M.S., unpublished data). Thus, remaining sensitive to androgens throughout life might be one mechanism by which both sexes avoid early phenotypic canalization (Pradhan et al ). Our results illustrate a striking similarity between adult and juvenile AR patterning during genitalia morphogenesis, which is consistent with the idea that adult sex change does not utilize a novel mechanism to regulate phenotypic transitions, but rather is repurposing ancestral mechanisms, at least one of which regulates male sexual differentiation (Wilkins ; Rodgers et al ).…”

A simple egg marking method for polygynous fishes

“…Quantifying fitness is fundamentally important to testing the adaptive function of 41 traits in the study of evolution and its underlying mechanisms. Reproductive success is 42 one of the best approximations of fitness (reviewed in Pradhan et al, 2015), and it is 43 feasible to quantify the number of offspring produced by an individual in a diversity of 44 species in the field (e.g., Buston, 2004;Griffith et al, 2008;Silk et al, 2009) Svensson and Kvarnemo, 2007) in fish can result in parents 59 caring for unrelated offspring. For gobies, one of the largest families of advanced fishes, 60 multiple females can lay eggs in the same nest within short succession (Tamada, 2008).…”