シオマネキのメガロパの飼育下における変態条件

Abstract

The settling condition and metamorphosis of megalops of the mud fiddler crab Uca arcuata were studied on the basis of a series of laboratory experiments. All the megalops on the emerged substrate succeeded in the metamorphose, but those on the submerged substrate showed less than 20% metamorphosing success. When the mud and sand substrates were provided in the emerged condition, megalops settled to make their own burrows and metamorphosed only on mud. Five types of substrates with different grain size compositions were provided to test burrow making and metamorphosing success. The survival rate of megalops was not different over the whole substrate, but metamorphosing success was significantly higher in the muddier sediment, while no metamorphosis occured in the sandy sediment. When the chance to meet an adequate substrate was manipulated, the megalops extended their pelagic phase and kept their metamorphosing ability for 20 days after molting.