Consumption and prey size selection of the nematode Caenorhabditis elegans by different juvenile stages of freshwater fish

Abstract

Meiofauna, and nematodes in particular, play an essential role in the diet of certain juvenile freshwater fish. However, the specific consumption and prey size selection of fishes on nematodes is largely unrecognised. In this study, the effects of different juvenile stages of widely distributed common European freshwater fish, gudgeon (Gobio gobio), roach (Rutilus rutilus), ninespine stickleback (Pungitius pungitius), and two strains of common carp (Cyprinus carpio (scaled) and C. carpio (mirror)), on abundances of the nematode Caenorhabditis elegans were investigated in controlled laboratory experiments with a known number of prey. Gudgeon, carp (scaled), and carp (mirror) consumed significant amounts of nematodes, whereas the roach and ninespine stickleback did not. Both strains of common carp reduced nematode abundance dependent on the size of the fish, with smaller fish causing a greater reduction than medium-size or large fish, although fish of all sizes fed significantly on nematodes of all size classes (<0.5, 0.5-1.0 and >1.0 mm). While the gudgeon also reduced nematode abundance dependent on the size of the fish, with increasing body length there was a dietary shift towards larger nematode size classes (0.5-1.0 and >1.0 mm). Morphometric analysis of the branchial basket indicated that the mesh width of gudgeon and both strains of common carp, but not of roach and ninespine stickleback, is suitable for feeding on specific size classes of nematodes. Together, the results showed that nematodes are used as a food source for different juvenile stages of certain species of freshwater fish.

The effects of predation by juvenile fish on the meiobenthic community structure in a natural pond

“…In others, fish predation on meiofauna was assumed to be nearly negligible because these prey populations are large and, with their short generation times, are able to recover very quickly such that they are not strongly impacted by the comparatively small numbers of predatory fish (Coull, ; Shaw & Jenkins, ; Cross & Curran, ). Yet, in other studies, benthic meiofauna were shown to be an important food source, especially for small and juvenile fish species (Schückel et al ., ; Weber & Traunspurger, ,b). Although this discrepancy has been attributed to differences in methodologies (e.g.…”

“…The main aim of this study was to close the knowledge gap between highly replicable small‐scale experiments and field studies with respect to the effects of fish predation on meiobenthic communities in natural freshwater ecosystems. At the same time, it is also important to recognise that the effect of fish predation on the meiobenthic community is often species specific (Dineen & Robertson, ; Spieth et al ., ; Weber & Traunspurger, ,b). For example, juvenile stages of the widely distributed carp Cyprinus carpio L. 1758 are bottom‐feeding consumers of meiofauna (Spieth et al ., ; Weber & Traunspurger, ,b).…”

“…Meiofauna serve as a link between basal resources (algae and detritus) and predators such as larger invertebrates and fish (Schmid & Schmid‐Araya, ; Weber & Traunspurger, ,b; Majdi & Traunspurger, ). The effects of marine fish predation on benthic meiofauna have been studied intensively, but the results have been inconsistent.…”

“…In small‐scale (e.g. microcosm and laboratory) experiments, freshwater fish species were shown to alter the abundance and composition of meiobenthic communities (Spieth et al ., ; Weber & Traunspurger, ,b), but these studies could not reproduce the influence of environmental factors, such as wave action and current velocity, nor such factors as emigration and immigration (Blanchet, Loot & Dodson, ; Englund & Leonardsson, ; Ludlam & Magoulick, ); thus, extrapolation of their results to natural conditions is problematic (Aarnio, ; Petersen & Englund, ; Meissner & Muotka, ). In the few cases in which the results could be compared, differences in predator–prey interaction strength were relatively large, with stronger effects reported either for small‐scale experiments or in field studies (Peckarsky, Cooper & McIntosh, ; Englund & Leonardsson, ).…”

Sazanın (Cyprinus carpio L., 1758) Tatlısu Ekosistemlerine Etkileri İçin Deneysel Kanıt: Türkiye İç Suları İçin Yönetim Yönlendirmeleri Derlemesi

“…: Enclosures within tanks), the results indicated that meiobenthos may represent a significant, yet often overlooked, food resource for 0+ C. carpio. These findings were supported by another series of experiments involving different size classes of 0+ C. carpio of the fully-scaled and mirror phenotypes, which indicated both size-and strain-related differences in the rate of consumption of the nematode Caenorhabditis elegans (Weber and Traunspurger 2014a). As a result of a related aquarium-based experiment, in which however no effects on nitrogen, phosphorus and chlorophyll a were detected, a conclusion was made that 0+ C. carpio may be able to exert top-down control of meiobenthic communities (Weber and Traunspurger 2014b).…”