Effect of salinity on the development of larvae and juvenile instars of <i>Neoepisesarma</i> (<i>Neoepisesarma</i>) <i>mederi</i> (H. Milne Edwards)

Abstract

There are 4 zoeal stages and a megalopa in the larval life history of <i>Neoepisesarma</i> (<i>N.</i>) <i>mederi</i>. Salinity effect on the development of larvae and first 2 juvenile instars was studied in 7 test salinities (5, 10, 15, 20 25, 30 and 35 x 10^-3). Complete development of zoeal stages was recorded in a salinity range of 10-30 x 10^-3, whereas the metamorphosis of megalopa and first 2 juvenile instars proceeded from 5 x 10^-3 to 30 x 10^-3 salinity. Zoeal development did not proceed in 5 and 35 x 10^-3 salinities. When megalopa and juvenile instars raised in the salinity range of 10-30 x 10^-3 were introduced into 5 and 35 x 10^-3 salinities, development proceeded only in 5 x 10^-3 salinity whereas total mortality was observed in other. The optimum salinity for the zoeal development was 25 x 10^-3. But the megalopa and first 2 juvenile instars preferred 5 x 10^-3 salinity in which 100% survival and rapid moulting were observed suggesting that this is the salinity optimum for development of megalopa and first 2 juvenile instars. While 5 and 35 x 10^-3 salinities were lethal for zoeal stages, 35 x 10^-3 salinity was lethal for the megalopa and first 2 juvenile instars.