Life cycles, breeding periods and vertical distribution ofIdotea granulosarathke andI. Pelagicaleach (Crustacea, Isopoda) on Icelandic shores

Abstract

Abstract The life cycles, breeding periods and vertical distribution of two species of Idotea from three intertidal localities in Iceland were investigated over a period of two years. Two of the localities (Straumsvik, Haanef) were in southwestern Iceland while one (Husavik) was in northern Iceland where sea temperatures are considerably lower. The vertical distribution was widest during the summer for both species. During summer, I. granulosa had a wider distribution at Straumsvik than at Husavik, while the more southern I. pelagica was restricted to the lowermost part of the shore. During winter at Straumsvik I. granulosa receded to the lowermost part of the shore and disappeared altogether from the intertidal zone at Husavik. I. pelagica at Haanef also disappeared from the shore during winter but for a considerably longer period. Oostegites started to develop on females in late winter and the juveniles were mainly released in the autumn in all cases. Females of I. granulosa and I. pelagica in the south...