Studies on the total haemocyte count and haemolymph volume in Periplaneta americana (L.) with special reference to the last moulting cycle

Abstract

The calculated number of haemocytes in the entire insect (= absolute count) gives far more reliable information concerning changes in haemocyte numbers than total haemocyte counts (= THC) alone because the latter obviously will vary according to the haemolymph volume. The absolute number of circulating haemocytes in the entire Periplaneta americana (L.) does not increase prior to ecdysis even though the number of haemocytes per cubic millimetre increases. This relative increase in haemocytes is due to a decrease in haemolymph volume. The absolute number of circulating haemocytes does not decline at ecdysis itself even though there is a significant decrease in the number of haemocytes per cubic millimetre. This relative decrease in THC is directly related to a significant increase in the haemolymph volume. At ecdysis there is a great increase in coagulability of the haemolymph and in absolute numbers of one specific type—the cystocytes (= coagulocytes). However, the absolute number of circulating haemocytes significantly decreases 24 hr after ecdysis, but there is no change in the number of haemocytes per cubic millimetre at this time because the haemolymph volume has returned (decreased) to normal. Simultaneously there is a significant decrease in the absolute numbers of circulating cystocytes and a decrease in the coagulability of the haemolymph.