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The article reports on the Hepatopancreatic rickettsial infection of the penaeid shrimp. Frozen Penaeus (P.) marginatus tissues were screened for pathogens by shrimp bioassay. Preserved shrimp were processed for routine histopathology and stained with haematoxyiin and eosin. The rickettsial agent from P. marginatus was found to be highly infectious for juvenile P. stylirostris. Based on the data presented, P. stylirostris bioassay would appear to be of use as a method to determine the presence of this rickettsia in wild-caught P. marginatus, and juvenile P. stylirostris could be used as a suitable host for experimental culture of this rickettsia under laboratory conditions.

This article reports the occurrence of B. penaei in an additional host species, Penaeus marginatus Randall, and geographical area, Hawaii. Penaeus marginatus or Opai Lolo is the only member of the genus Penaeus indigenous to the Hawaiian Islands. Additional juvenile (01 to 4-0 g) P. marginatus were collected from the Kuliouou tidal flats from January to March 1984. These shrimp were held in aquaria for 7-10 days prior to examination. Shrimp were sacrificed by injection and immersion in Davidson's fixative, and after 24 h transferred to 50% ethanol for storage. Preserved hepatopancreata were processed for routine histopathology and stained with haematoxylin and eosin.