Abstract
Fish develop morphological specializations in their trophic and locomotor systems as a result of varying functional demands in response to environmental pressures at different life stages. These specializations should maximize particular performances in specialists, adapting them to their trophic and habitat niches at each ontogenetic stage. Because differential growth rates of the structural components comprised in the head are likely to be linked to the diet of a fish throughout its development, we investigated the ontogenetic development of two haplochromine cichlid species belonging to different trophic guilds. We employed geometric morphometric techniques to evaluate whether starting from morphologically similar fry they diverge into phenotypes that characterize trophic guilds and locomotor types. Our examination of overall body shape shows that certain specialized morphological features are already present in fry, whereas other traits diverge through ontogeny due to differences in species-specific allometric variation. Allometric shape variation was found to be more relevant for the biter specialist than for the sucker morphotype. Our results confirm that phenotypic changes during ontogeny can be linked to dietary and habitat shifts in these fish. Furthermore, evidence for an integrated development of trophic and locomotor specializations in morphology was observed.
Highlights
* corresponding author: ABSTRACT result of varying functional demands in response to environmental pressures at different life stages
In order to account for the influence of domestication on shape, three type specimens from Lake Victoria, Tanzania were included for H. piceatus (RMNH 62769) and two for H. fischeri, provided by the NCB Naturalis
Species-specific allometric shape variation accounted for a larger percentage of the shape variation within the ontogenetic sample
Summary
* corresponding author: ABSTRACT result of varying functional demands in response to environmental pressures at different life stages. Evolution considering functional morphology, ecological speciation, phenotypic plasticity, and convergent morphotypes In this context, East African cichlids exhibit a large array of ecotypes in relation to selective pressures on foraging performance and/or behavior, occupying a large range of habitats and trophic niches The characterization of these ecotypes is based upon the functional pressures on their internal and external anatomy, which interrelate with environmental factors that stimulate the expression of genetic and plastic responses in their morphology (Sage & Selander, 1975) In accordance, these functional pressures change ontogenetically (Osse, 1990; Zengeya et al, 2007), parallel to dietary and niche shifts that many of these species experience (Galis & De Jong, 1988; Goldshmidt et al., 1990; Galis, 1993). It has been documented that certain morphological specializations in locomotor anatomical structures reiteratively correspond to specific trophic guilds, advocating a connection between the development of locomotor and trophic specializations in cichlid fish (Barel, 1983)
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