Morphometric variation in bluegill Lepomis macrochirus and green sunfish Lepomis cyanellus in lentic and lotic systems

Abstract

Bluegill Lepomis macrochirus and green sunfish Lepomis cyanellus were examined using geometric morphometrics to evaluate the variation in morphology between fishes that reside in lentic (e.g. lakes) and lotic (e.g. streams) ecosystems. Live fishes were collected from reservoirs and rivers in central Indiana, while additional fishes were sampled from museum collections at Ball State University and the Illinois Natural History Survey. Male and female L. macrochirus and female L. cyanellus from lentic systems display a deeper body than those from lotic systems, while no differences were found in male L. cyanellus morphometry. A deeper body promotes greater manoeuverability, typically desirable in lentic systems. In contrast, the more streamlined body of the fishes found in lotic systems reduces drag as it contends with flowing water, ultimately maximizing energy efficiency. The absence of morphological differences, such as those found in male L. cyanellus, may be caused by fish occupying both lentic and lotic systems, from the population not having been present in the body of water long enough to display any adaptations, or from a lack of statistical power caused by the small sample size.

Shape variation in the least killifish: ecological associations of phenotypic variation and the effects of a common garden

“…2004; Herczeg et al. 2010; Gaston and Lauer 2015). However, habitats rarely differ in only a single putative ecological agent of selection.…”

“…Fish populations occurring in high flow areas are often thinner and have more streamlined bodies when compared to conspecifics found in low flow areas (Franssen 2011; Fu et al. 2013; Gaston and Lauer 2015). Foraging habits and the position of available food resources, whether they are suspended in the water column, floating on the surface or located in the benthos, have been found to affect morphological development in fishes (Robinson and Wilson 1995; Svanbäck and Eklöv 2002).…”

“…A large proportion of this literature focuses on how specific phenotypic traits vary among habitats. Populations are often grouped into broad habitat types based on either a single biotic selective agent such as presence or absence of predators or a single abiotic contrast such as that between lentic and lotic bodies of water Herczeg et al 2010;Gaston and Lauer 2015). However, habitats rarely differ in only a single putative ecological agent of selection.…”

Changing environmental gradients over forty years alter ecomorphological variation in Guadalupe Bass Micropterus treculii throughout a river basin

“…Under decreased current or stagnant environments deeper bodied individuals have shown improved foraging ability and predator avoidance performance (Franssen et al., ; Santos & Araújo, ). For example, when Bluegill Lepomis macrochirus and Green Sunfish Lepomis cyanellus were compared between lotic and lentic habitats, which naturally represent two extremes in flow conditions, the individuals in the reservoir habitats tended to have deeper bodies, while streamlined individuals were found in lotic environments (Gaston & Lauer, ). Morphological differentiation in Guadalupe Bass was not compared across the extremes of stream versus reservoir habitat; however, similar increases in body depth were observed between contrasting temporal flow conditions.…”

Functional morphology of the tetra fish Astyanax lacustris differs between divergent habitats in the Pantanal wetlands

“…Morphological differences between fish populations inhabiting lentic and lotic habitats have been documented in several species (Langerhans et al , ; Foster et al , ; Gaston & Lauer, ). In the case of A .…”