Biology of the bottom-dwelling shrimp Nauticaris marionis Bate, 1888 at the sub-Antarctic Prince Edward Islands

Sub-Antarctic bottom-dwelling caridean shrimps Nauticaris marionis were col lected in April/May between 1984 and 1997 over the shelf region of the Prin ce Edward Islands (37 degrees 50'E, 46 degrees 45'S). N. marionis is a part ially protandric hermaphrodite. Hatching probably occurs just before April each year, but may persist until May. During the Ist year N. marionis seem to survive in undetected localities, moult into juveniles, and then settle amongst the benthos from the plankton beginning probably after November. Di el vertical migration then occurs up to an unknown larger size. The vast ma jority of juveniles develop into males, most of which transmutate into fema les by April/May of their 3rd year. Reproduction can occur before all male secondary characteristics have been lost. A minority of individuals develop directly into females without passing through a male phase. Individuals ol der than 5 years are undetectable using samples of the sizes analysed, but they may well persist in the population. The von Bertalanffy growth paramet ers for N. marionis are tentatively identified as k = 0.2353/year, L-infini ty = 12.6 mm, t(0) = -0.2828 years and WWinfinity = 2.03 g. Sex-reversal in N. marionis at Marion Island may be affected by the changing environment a s sexual differentiation is probably determined during the planktonic stage .