Abstract

Neurobiology researchers at a marine laboratory in North Carolina noticed the presence of numerous small (0.5 to 1.0 millimeter diameter) pale white cysts associated with the esophagus of the Atlantic octopus, Octopus vulgaris. Dozens of these mature cephalopods were infected and in rare instances lesions were observed in the brain. Microscopic examination of these lesions indicated that they are coccidian protozoal parasites, most likely belonging to the family Aggregatidae.

A number of apicomplexan parasites belonging to the genus Aggregata have been described in the literature to infect cephalopod mollusks. The majority of these reports discuss eastern Pacific or eastern Atlantic cephalopods. The life cycle of these parasites usually involves two hosts with an arthropod intermediate host. This research is the first thorough examination of these parasites in the large western Atlantic octopus, Octopus vulgaris.

Gross and microscopic morphology and pathology, as well as taxonomic importance, are discussed.

Discussion

This report describes infection in 4 Atlantic octopuses with an apicomplexan parasite of the genus Aggregata. These mature male octopuses had been caught off the coast of North Carolina and held in captivity for several weeks at the Duke Marine Research Laboratory in Beaufort, NC. The octopuses were among a group of 30 animals held at this facility and used in a behavioral study. Some of the animals had surgery performed on the brain as part of the behavioral research. Two of the animals in this study had brain operations. They were housed individually in 20 gallon tanks with recirculating natural sea water and fed shrimp. An increase in morbidity and mortality among the population of octopuses prompted an examination of the four animals. Moribund animals frequently became anorexic and developed generalized skin lesions.

All four animals died. Complete necropsies were performed on two, the gastrointestinal tract was examined on the third, and only a section of esophagus was submitted for histopathology from the fourth animal. Bacterial infection was the likely cause of death and bacteria isolated from these animals included Listonella damsela, Vibrio parahaemolyticus and Aeromonas salmonicida. Necropsy on the first three animals did not reveal gross lesions except for numerous 0.5 to 1.0 millimeter diameter white foci visible from both the serosal and mucosal surfaces of the esophagus, crop, spiral cecum and extending most of the length of the intestine. It is unlikely that the coccidian parasites contributed to the death of the octopuses. Microscopic examination showed that these white foci were oocysts of a coccidian parasite. Oocycsts in the esophagus from animal #4 were located primarily in the mucosa, subjacent to the epithelium, but occasionally were subserosal. None of the cysts appeared to be eliciting a host response, and the epithelium overlying the parasites was in all instances intact. Oocysts varied from 230 X 280 microns up to 340 X 400 microns, and contained numerous 15 micron diameter sporocysts. Each sporocyst in turn contained several sporozoites with their nuclei clustered at one pole. Histopathological results from the other three animals are pending.

Infestation with two species of Aggregata, A. dobelli and A. millerorum have recently been described by Poynton, Reimschussel and Stoskopf in two species of Pacific octopuses, octopus bimaculoides and 0. dofleini, that died shortly after they were captured (1). Infection has apparently not been reported in Atlantic octopuses from North American waters, although A. octopiana and A. spinosa have been reported from 0. vulgaris in Europe. The paper by Poynton and colleagues describes oocysts containing sporocysts in the same locations as those in our specimens of 0. vulgaris, namely the esophagus, crop, stomach, spiral cecum and intestine anterior to the anus. In these animals, A. dobelli and A. millerorum both caused ulceration of the intestinal mucosa. The authors believed Aggregata infection was not the primary cause of death, but that heavy parasitism may have contributed to death in some cases.

Aggregata sp. have a two host life cycle, with merogony occurring in a crustacean and gametogony and sporogony in a cephalopod. Infection occurs in cuttlefish as well as octopus.

Acknowledgments

The authors would like to thank Dr. R. David Robertson and Mr. Doug Murlless of the Duke University Marine Laboratory for their cooperation in this study.

Reference

1.  Poynton, SL, Reimschuessel, R and M Stoskopf. Aggregata dobelli n. sp. and Aggregata millerorum n. sp. (Apicomplexa; Aggregatidae) from two species of octopus (Mollusca: Octopodidae) from the eastern north Pacific ocean. J. Protozool., 39(1): 248­256, 1992.