OSMOREGULATION AND SALINITY TOLERANCE IN ZOEAE AND JUVENILES OF THE SNOW CRAB CHIONOECETES-OPILIO

Osmoregulation and salinity tolerance were studied in zoeae 1 and inst ar IX juveniles of Chionoecetes opilio. In zoeae 1, the lower and uppe r lethal salinities for 50% of the animals (LS 50) at 14 degrees C wer e about 10 and 42 parts per thousand at 24 h, 18 and 41 parts per thou sand at 48 h, 25 and 38 parts per thousand at 96 h. In juveniles, the approximate 48 h LS 50 s at 6 degrees C were 13.5 and 46 parts per tho usand. Both developmental stages are able to withstand relatively ampl e but brief variations of salinity. Their short-term euryhalinity is d iscussed in relation to the salinity of their habitat. Zoeae were hype r-osmoconformers. Juveniles were osmoconformers and isoionic to the ex ternal medium except for Mg++ which was hypo-regulated. Isosmotic and isoionic regulation in post-metamorphic stages are presumably an attri bute of the family Majidae. The pattern of osmoregulation in zoeae 1 a nd juveniles relate C. opilio to the first of three groups of species previously characterized by their pattern of ontogeny of osmoregulatio n.