Use of a clinical cell flow cytometer for differential counts of prawn Penaeus monodon haemocytes

Flow cytometry (FC) has been used extensively for monitoring human blood cell populations and it would be useful if this technology could be applied to the analysis of prawn haemocytes. This paper shows that the Cell-Dyn 3000 flow cytometer can distinguish haemocyte types from Penaeus monodon and then describes the range of haemocyte counts within normal prawns. The total haemocyte count was 23.3 x 10(6) cells ml(-1) using a haemocytometer and 21.0 x 10(6) cells ml(-1) with the FC. With light microscopy, nongranular, small-granular and large-granular haemocytes were 82.7 +/- 14, 15.6 +/- 17, and 1.7 +/- 2% respectively of the cell types, whilst with FC, the proportions were 82.6 +/- 17, 14.5 +/- 15, and 2.9 +/- 3 % respectively. Neither age, weight, carapace length nor population source had any significant effect (p > 0.05) on total or differential haemocyte counts. However, sex had a significant effect (p < 0.05) and once sexual dimorphism, as measured by total length, had occurred in the prawn population, females showed increased nongranular haemocyte counts (F = 4.56, df = 1,39, p < 0.05) and, consequently, total haemocyte counts (F = 4.60, df = 1,39, p < 0.05). The third sequential bleeding of prawns (0.1 ml of haemolymph bleed(-1)) produced a significant decrease in total haemocyte numbers with proportional increases in granular haemocytes.