Variations in vertical distribution of developing snow crab Chionoecetes opilio and red snow crab Chionoecetes japonicus (Crustacea, Decapoda, Majoidea) larvae in experimental temperature gradients

Le résumé fourni par la source

In the Sea of Japan, field studies have found snow crab and red snow crab larvae occur between the surface and depths of up to 550 m and 1100 m, respectively. In this region, snow crab larvae hatch at depths of 240–260 m and red snow crab larvae hatch at 1000–1500 m. To understand their vertical distribution during the larval period, we investigated the upward swimming speed of newly hatched larvae (first-stage zoea) and the behaviour of all larval stages (first and second zoeal and megalopal stages) in a temperature gradient under laboratory conditions. Our results showed that the larvae have the potential to reach the surface within a few days of hatching. As the larvae developed, they preferred greater depth and lower temperatures; although they temporarily rose to higher levels immediately after each moult. The zoeae and megalopae of both species did not occur beyond the 16 and 6°C temperature layers, respectively. The preferred position of the larvae in the gradient temperature did not differ between the two species. The present study suggests that Chionoecetes larvae transported to unsuitable temperatures may not die, but could escape from low temperatures by upward swimming and from high temperatures by sinking.

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