Journal Article

Lazy males? Bioenergetic differences in energy acquisition and metabolism help to explain sexual size dimorphism in percids

Rennie, Michael D., Purchase, Craig F., Shuter, Brian J., Abrams, Peter A., Lester, Nigel, Collins, Nicholas C.

2008

Overview

1. Differences in energy use between genders is a probable mechanism underlying sexual size dimorphism (SSD), but testing this hypothesis in the field has proven difficult. We evaluated this mechanism as an explanation for SSD in two North American percid species - walleye Sander vitreus and yellow perch Perca flavescens. 2. Data from 47 walleye and 67 yellow perch populations indicated that SSD is associated with the onset of maturation: typically, males of both species matured smaller and earlier and attained a smaller asymptotic size than females. Males also demonstrated equal (perch) or longer (walleye) reproductive life spans compared with females. 3. To examine whether reduced post-maturation growth in males was due to lower energy acquisition or higher reproductive costs we applied a contaminant mass-balance model combined with a bioenergetics model to estimate metabolic costs and food consumption of each sex. Mature males exhibited lower food consumption, metabolic costs and food conversion efficiencies compared with females. 4. We propose that slower growth in males at the onset of maturity is a result of decreased feeding activity to reduce predation risk. Our finding that SSD in percids is associated with the onset of maturity is supported by laboratory-based observations reported elsewhere, showing that changes in growth rate, consumption and food conversion efficiency were elicited by oestrogen (positive effects) or androgen (negative effects) exposure in P. flavescens and P. fluviatilis. 5. Researchers applying bioenergetic models for comparative studies across populations should use caution in applying bioenergetic models in the absence of information on population sex ratio and potential differences between the sexes in energetic parameters.

• Publisher: Oxford, UK : Blackwell Publishing Ltd,British Ecological Society,Blackwell Publishing Ltd,Blackwell
• Subject: activity / adverse effects / Agnatha. Pisces / anatomy & histology / Animal and plant ecology / Animal ecology / Animal populations / Animal, plant and microbial ecology / Animals / Bioenergetics / Biological and medical sciences / Comparative studies / consumption / Contaminants / Ecological modeling / Ecology / energy / Energy consumption / Energy Metabolism / Evolutionary Ecology / Female / Female animals / Females / Fish / Fisheries science / Food / food consumption / food conversion / Freshwater fishes / Fundamental and applied biological sciences. Psychology / Gender differences / General aspects / growth & development / Growth rate / Life span / Male / Male animals / males / Maturity / Measurement techniques / Metabolism / Perca / Perca flavescens / perch / Perches / Perches - anatomy & histology / Perches - growth & development / Perches - metabolism / predation / reproductive investment / risk / Sander vitreus / Sex Characteristics / Sex ratio / Sexual dimorphism / Time Factors / Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution / walleye / yellow perch