Introduction

The apicomplexan Aggregata is a parasite of the digestive tract of cephalopods. The genus has been extensively studied in the cephalopods Sepia and Octopus in Europe, but little studied in North America. (Hochberg, 1983).

Review

Despite the role of Octopus in the marine ecosystem, and their importance to man as food items and for biomedical research, aspects of their parasite fauna are little known. Studies in Europe (Dobell, 1925) have shown that the protozoan parasite Aggregata commonly infects cephalopods. In the pioneering studies of this genus, Dobell showed that A. eberthi has a two host lifecycle. Merogony (or vegetative reproduction) takes place in a crab. When the crab is eaten by a cephalopod, the parasite passes to the new hosts' digestive tract, where gametogony (production of gametes) and sporogony (production of spores) occurs. The life cycle is completed when mature sporocysts, which have been passed from the cephalopod in the faeces, are eaten by a crab.

Taxonomy of species of Aggregata is based upon morphology of the sporocysts and sporozoites. Although there are numerous reports of Aggregata infection in cephalopods, few species have been well documented. Three species are reported from European cephalopods namely A. eberthi (Dobell,1925), A. octoDiana (Moroff,1908; Wurmbach,1935), A. sipinosa (Moroff, 1908); A. kudoi is reported from Sepia in India (Narasimhamurti,1979).

Reports on the histopathology of the infections in the final host include observations of the intracellular nature of the parasites, and enlargement of the host cells.

Work in Progress

We have recently examined tissues from ailing North Pacific Giant Octopus Octopus dofleini martini and California two-spotted octopus Octopus bimaculoides held at the National Aquarium in Baltimore between 1981 and 1989. Histological sections have been prepared from a number of different sites in the digestive tract. Development of the Aggregata gametes and sporocysts in the two hosts has been recorded, as has the distribution of the parasites in different layers and regions of the digestive tracts.The histopathology of the infections has been observed.

References

1.  Dobell,C.1925. The life history and chromosome cycle of Aggregata eberthi (Protozoa: Sporozoa: Coccidia) Parasitology 17,1-136, + vi plates.

2.  Hochberg,F.G. 1983. Parasites of cephalopods: a review. Memoirs of the National Museum of Victoria, Melbourne, Australia 44,109 145.

3.  Moroff,T. 1908. Die bei den Cephalopoden vorkommenden Aggregataarten als Grundlage einer kritischen Studie uber die Physiologie des Zellkernes. Archive fur Protistenkunde 11, 1-224.

4.  Narasimhamurti,C.C. 1979.The eimeriid Aggregata kudoi n.sp. from Sepia ellilptica. Angew. Parasitol. 20, 154 - 158.

5.  Wurmbach,H.1935 : Uber die Beeinflussung des Wirtswewebs durch Aggregata octoplana und Klossia helicina. Archiv fur Protistenkunde 84, 257 - 284.