Cellular reactions of field crickets (Acheta pennsylvanicus Burmeister) and German cockroaches (Blatella germanica L.) to Physaloptera maxillaris Molin (Nematoda: Physalopteroidea)

The site of development, survival of larvae, and reaction to the presence of Physaloptera maxillaris [a nematode parasite of the skunk Mephitis mephitis that has arthropod intermediate hosts] are described in Gryllus pennsylvanicus Burm. (Acheta pennsylvanicus) and Blattella germanica (L.) from observations on artificially infected examples in the laboratory. In Gryllus, the preferred site of development was the villous segment of the ileum, whereas in Blattella larval nematodes developed mainly in the colon. Few larvae became melanised in Gryllus, but in Blattella many became melanised and died. Most larvae developed in capsules within the hind-gut. Each capsule was a giant cell with large nuclei and granular cytoplasm derived from coalesced epithelial cells. Larvae apparently ingested capsule contents. In Blattella, the capsule walls were thin and haemocytes invaded the capsule and melanisation destroyed many larvae. Capsules in Gryllus were thick walled; few haemocytes invaded them, little melanisation occurred, and most larvae survived for long periods. Larvae that penetrated directly into the haemocoel were surrounded by haemocytes and became melanised.ADDITIONAL ABSTRACT:The site of development, survival of larvae, and reaction to the presence of Physaloptera maxillaris in field crickets (Acheta pennsylvanicus) and German cockroaches (Blatella germanica) were compared. The preferred site of development in crickets was the villous segment of the ileum. Few larvae became melanized. Larvae developed mainly in the colon in cockroaches and numerous larvae became melanized and died. Most larvae developed in capsules within the hindgut. Each capsule was a giant cell with large nuclei and granular cytoplasm derived from coalesced epithelial cells. Larvae apparently ingested capsule contents. In cockroaches the capsule walls were thin and haemocytes invaded the capsule and melanization destroyed many larvae. Capsules in crickets were thick walled; few haemocytes invaded them, little melanization occurred, and most larvae survived for long periods. Larvae which penetrated directly into the haemocoel were surrounded by haemocytes and became melanized. [AS].