Observations on the Biology and Post-Embryonic Development of Idotea Viridis (Slabber) (Isopoda, Valvifera) from New England Creek, South-East Essex

Abstract

A local race of Idotea viridis from south-east Essex is described and its classification as /. viridis discussed. This animal is a nektonic form and so far has only been found in New England Creek in south-east Essex. The biology and post-embryonic development of this race is described. Quantitative samples were taken of the animals present in the creek in 1934, 1935 and 1936. I. viridis was rare in the first five months of the year; numbers rose to a maximum in late June and July and remained comparatively high until the end of October.The number of young in the brood pouch is very variable. There is some evidence that the number of fertilized eggs was reduced by the expulsion of embryos before their development was complete. The newly hatched I viridisis described.