Behaviour of drifting insect larvae

Abstract

The larval drift behaviour of 23 species representing Ephemeroptera, Plecoptera and Trichoptera was investigated in the laboratory using different current regimes. Mayfly nymphs often performed swimming, while caddis larvae were reluctant to do so. Stonefly nymphs were intermediate. In mayflies swimming seemed to be used to reach the substrate as soon as possible. In contrast most stonefly nymphs by swimming prolonged the time spent in the water column. Modes of swimming and sinking posture differed markedly between the orders. Living passively sinking animals often reached bottom faster than dead control specimens, so consequently behaviour did not always express itself in activity. Some caddis larvae spun adherent anchor lines. Differences among taxa seemed more important in explaining swimming activity compared to preferred habitats (as stream, river and lake) in each species. However, observed differences among closely related species indicated subtle differences related to microhabitat to be of profound importance in explaining the alternative behavioural strategies used.

Modeling the influence of flow on invertebrate drift across spatial scales using a 2D hydraulic model and a 1D population model

“…First, future studies might incorporate additional behavior in the "particles" that represent drifting animals, for instance by coupling individual-based simulations with hydraulic models. While many stream organisms may drift and settle passively (Elliott, 1971a), many others actively swim or reposition their bodies in the drift (Allan and Feifarek, 1989;Campbell, 1985;Oldmeadow et al, 2010;Otto and Sjostrom, 1986). Settlement patterns may also be complicated by small-scale hydrology (Fonseca and Hart, 2001) and the mechanisms by which organisms re-attach to the benthos (Fingerut et al, 2006(Fingerut et al, , 2011.…”

“…The effect of settling velocity (ω s ) and dispersion (D H and D V ) have been shown to play important roles on the pattern of drift transport in previous models (Ciborowski, 1983;Hayes et al, 2007). An added complication arises from the fact that many stream macroinvertebrates exhibit control over their behavior in the drift and settle at rates that differ from similar sized inanimate particles (Allan and Feifarek, 1989;Campbell, 1985;Elliott, 1971a;Oldmeadow et al, 2010;Otto and Sjostrom, 1986). Because of this violation of the assumptions of Stoke's law, we estimated settlement velocities from published experiments on drift settlement (see Section 2.2.4.1).…”

Settling distances of benthic invertebrates in a sediment mobilization simulation in semi-natural flumes

“…This resulted in taxon-dependent settling distances, which can be compared with data from previous studies on the same genera of mayflies, stoneflies, caddisflies. Otto and Sjöström (1986), investigated drift behaviour in 25 species of mayflies, stoneflies and caddisflies in a laboratory stream. Although they recorded some differences in all orders, even between closely related species, as a general trend mayfly nymphs swam to reach the substrate as quickly as possible; stonefly nymphs prolonged the time spent in the water column by swimming, and caddisfly larvae were reluctant to swim.…”

“…settled within 10 m, and started settling from 4 m. Net-spinning caddisflies often trail a silk thread to enhance their settling efficiency (Elliott, 1971;Otto and Sjöström, 1986). The remaining two caddisflies, Rhyacophila sp.…”

Seasonal drift-benthos trends on a moss-covered tufa barrier within a karst barrage hydrosystem (Plitvice Lakes, Croatia)

“…the increased flow velocities erode (i.e., dislodge) the substrate (e.g., moss) and substrate-associated particles and organisms, and often prevent their settling, especially if they are small (Speaker et al, 1984;fonseca, 1999). Once dislodged from the stream bed, larger particles (e.g., CPOm and mOSS) exhibit higher sinking rates, spending less time in the water column and reaching the stream bed faster than the smaller particles (Otto & Sjöström, 1985;fonseca, 1999). whereas the larger particles are less affected by flow oscillations, abrupt flow changes and water column conditions and they easily get settled in the pool habitats, the finer particles are mostly "kept in drift" by the turbulence (fonseca, 1999).…”