EPPECT OF SALIMITY VARIATION OM HEMOLYMPH CALCIUM COHCEXTRATIOH DURIHG THE MOULT CYCLE OP THE PRAWH PEKAEUS JAPOHICUS (BATE)

EPPECT OF SALIMITY VARIATION OM HEMOLYMPH CALCIUM COHCEXTRATIOH DURIHG THE
MOULT CYCLE OP THE PRAWH PEKAEUS JAPOHICUS (BATE)
8y
KADIA F. ABO EI-HAMID1 , ABO H.O. HASHEM,
*Institute of Oceanography and Fisheries, Alexandria, Egypt.
Key words: Prawn, Penaeus Japonicus, Effect of Salinity, Hemolymph, Moult Cycle
ABSTRACT
Prawns Pena~~ i~pon!_~us were obtained from Abu-Kir Bay (east,of
Alexandria) and maintained in glass aquaria in laboratory at different
salinities ranging from 10 to 40\0′ Total hemolrmph calcium levels
were measured during the moult cycle. Results showed that these
levels were largely affected by moult stage and to a lesser degree
by salinity. A sharp, transient increase in hemol~ph calcium
occurred 3 to 6 h postmoult, followed by an equally rapid decrease
from 6h postmoult to intermoult. This biphasic response was limited
to prawns in 10, 20 and 30\0 salinity; while in 40\0 salinity,
hemolymph calcium remained the same throughout the experimental
period. Peak concentrations of total calcium observed for low
salinities, (10 &20\0) were still higher than those recorded for the
higher salinity (30 & 40\0). Salinity had no effect either on the
duration of moult cycle or on time of moult occurrence.