Locomotor activity rhythms of North Atlantic coastal talitroids

Locomotor activity rhythms of one hyalid and six talitrids were deterermined extending published rhythms to species in three new ecotopes previously not examined in this way: eulittoral – the hyalid, <i>Apohyale prevosti</i> (H. Milne Edwards 1830) with a circatidal rhythm, supralittoral/palustral – the talitrid, ‘<i>Orchestia’ grillus</i> Bosc 1802 and supralittoral/xylophagous talitrid, <i>Macarorchestia remyi</i> (Schellenberg 1950), where activity was random in both. A xylophagous-acclimated population of <i>Platorchestia platensis</i> (Krøyer 1845) living in a secondary ecotope also exhibited random activity. Endogenous diel rhthyms with maximum activity during darkness were present in the supralittoral wrack generalists [<i>P. platensis</i> and <i>Orchestia gammarellus</i> (Pallas 1766)] and sand-burrowing specialists [<i>Americorchestia longicornis</i> (Say 1818) and <i>A. megalophthalma</i> (Spence Bate 1862)]. The tentative order for talitrids examined here and in the literature, from high to low, in their susceptibility to passive, natural dispersal in wrack/driftwood is therefore as follows: <i>O. gammarellus</i> + <i>P. platensis</i> &gt; <i>O. mediterranea</i> Costa 1853 &gt; marsh-hoppers &gt; sand-hoppers &gt; driftwood-hoppers.