Isolation and in vitro characterisation of prohaemocytes from the spider crab, Hyas araneus (L.)

A population of small, mostly undifferentiated, haemocytes were identified and enriched from the circulation of the spider crab, H. araneus, using a two-step density gradient separation procedure. Typically, these cells are spherical, ca. 8-12 μm diameter and have a high nucleus:cytoplasm ratio. Their number in the circulation increases significantly 24 h after a state of haemocytopenia has been created by withdrawal of 2 mL of haemolymph. The rise in the number of these cells at this time is consistent with a left shift phenomenon. A two-step separation procedure was developed to generate enriched populations of these small cells from the haemolymph and in vitro assays revealed that ca. 47% are BrdU-positive in vitro. By contrast BrdU uptake was not observed in the hyaline, semigranular or granular cells. The proliferative ability of the small cells, coupled with their close morphological resemblance to immature haemocytes reported from the haematopoietic tissue of other decapod species, leads us to conclude that these cells are prohaemocytes.