Effects of larval size and hydrodynamics on the growth rates of the black fly Simulium tribulatum

Abstract

Black flies are ubiquitous and important members of lotic ecosystems. Size is known to affect many aspects of their life in the aquatic larval stage, including intraspecific competition for feeding sites. As filter feeders, flow affects their ability to feed and reach sufficiently fast flow. This, in turn, can lead to risky fluid-mediated dispersal behavior in search of better conditions. It is surprising, therefore, that little information is available regarding how physiological and environmental factors combine to affect larval growth rates. The present study determines the relative growth rates of small (0.6 mm) and large (approximately 4 mm) larvae in laboratory flumes designed to produce spatially homogeneous and temporally consistent flow regimes at ecologically relevant velocities (44 and 64 cm/s). Our results indicate that size and flow both influence growth rates and that the 2 interact significantly. Young larvae exhibit faster growth rates and a greater positive response to increased flow speed. This result might help explain why smaller larvae have a greater propensity to disperse than larger larvae: the benefit of increased growth rate that they receive from relocating to faster flow might balance the risks inherent in dispersal.

Comparative Study of Potential Habitats for Simulium qinghaiense (Diptera: Simuliidae) in the Huangshui River Basin, Qinghai–Tibet Plateau: An Analysis Using Four Ecological Niche Models and Optimized Approaches

“…This aligns with our study findings, underscoring the critical role of altitude in a suitable environment for S. qinghaiense. Previous studies have indicated that the abundance of blackflies is higher and the young larvae exhibit faster growth rates in fastflowing streams [69,70]. It is worth noting the influence of current velocity on S. qinghaiense.…”

Scale‐dependent relationships between suspension‐feeding stream insects and water velocity in spatially heterogeneous flow environments

“…We used water velocity as a measure of resource availability because of its demonstrated strong influence on the feeding performance of Simulium tribulatum, one of the most widespread and well-studied blackflies in North America. Rates of ingestion and growth of larval blackflies increase with increasing velocity (Charpentier & Morin, 1994;Finelli et al, 2002;Brannin, O'Donnell & Fingerut, 2012), often leading to greater male mating success and female fecundity (Tarrant et al, 1983;Edman & Simmons, 1985). Moreover, while near-bed velocities experienced by benthic biota can exhibit marked spatial variation within individual substrates as well as among different habitat types (e.g.…”