Total and differential haemocyte counts in western rock lobsters (Panulirus cygnus George) under post-harvest stress

Abstract

Total and differential haemocyte counts (THCs and DHCs) were obtained from 36 white and 36 red western rock lobsters (Panulirus cygnus) that had experienced stress during capture and transportation. The lobsters were divided into three different groups on the basis of their holding time in the factory tanks and their health status (fresh arrivals, healthy and moribund). THCs were obtained with a haemocytometer from fresh haemolymph stained with gentian violet. THCs ranged from 2.5 10⁶ to 15.9 10⁶ cells mL^-1 in the three groups, being lowest in the moribund lobsters. DHCs were obtained from haemolymph smears stained with both Giemsa and May–GrÜnwald. Three major haemocyte groups could be identified in lobster haemolymph: hyalinocytes, semi-granulocytes and granulocytes. The proportion of hyalinocytes in the three lobster groups ranged from 29.1% to 37.0%, that of semi- granulocytes from 51.1% to 62.9%, and that of granulocytes from 5.1% to 13.1%. The proportion of granulocytes declined in lobsters after they were held for 16 h in the factory tanks and was lowest in moribund lobsters. The results show that THCs and DHCs may be useful in assessing stress or health status in the western rock lobster or other lobsters.