Body size-related constraints on the movement behaviour of the arctic notostracan Lepidurus arcticus (Pallas, 1973) under laboratory conditions

The movement behaviour of individuals has long been acknowledged as a key determinant of species distribution in space and time. Information on benthic macroinvertebrates from aquatic habitats are still scant, however, and for polar species are virtually nonexistent. Here, the influence of body size on the movement behaviour of the arctic notostracan Lepidurus arcticus (Pallas) was examined under resource-free laboratory conditions. The mean step length, total path length and average speed were determined for specimens varying in body dry mass by six orders of magnitude. The scale-independent fractal dimension D was used to quantify movement path tortuosity. Among the different movement metrics considered, the body size of specimens scaled significantly only with path tortuosity; specifically, a negative relationship with a breakpoint was observed between individual body masses and the D values of the respective movement paths. The results are discussed considering similar results obtained for benthic crustaceans from temperate habitats. Additionally, their implications for future investigations explicitly considering temperature effects on movement behaviour are briefly considered.