Responses of echinoid larvae to food patches of different algal densities

摘要: High densities of larvae have been found in areas high primary production, but it remains unclear whether this is the result hydrodynamics or larval aggregative behaviour presence food. In study, we examined changes vertical distribution and swimming patterns four-armed sea-urchin Echinometra lucunter (Linnaeus) around food patches a range microalgal densities. We reared laboratory low concentration either single (Isochrysis galbana) mixed (I. galbana, Dunaliella tertiolecta, Thalassiosira weissflogii) species. Plexiglas cylinders, experimentally constructed haloclines which salinity bottom water-layer was 33‰ that top 24‰. thin layer middle halocline, inserted patch consisted 0, 2500, 5000 10 000 T. weissflogii cells ml−1. The had pronounced effect on larvae. This depended upon algal density varied with dietary conditioning. number were above within decreased increasing density, greater if low-ration single-species diets than high-ration mixed-species diets. Tracking individual paths showed few minutes, swam into to positions just below two higher densities, remained there until end experimental period. digestive tracts from treatments those without confirmed feeding patch. To our knowledge, first study show an behavioural response invertebrate Such may reduce probability limitation therefore enhance survival.