Revista Chilena de Historia Natural 78 (3): 441-450, 2005
RESEARCH ARTICLE
Microhabitat use by the protozoan parasite Aggregata patagonica Sardella, Ré
& Timi, 2000 (Apicomplexa: Aggregatidae) in his definitive host Enteroctopus megalocyathus (Gould, 1852)
(Cephalopoda: Octopodidae) in southern Chile
The protozoan parasites of the family Aggregatidae, require two hosts to complete their
life cycle, a crustacean and a cephalopod. This research looks for evidence of differential microhabitat use of Aggregata
patagonica infrapopulations between two zones of the digestive tract of his definitive host, the octopus Enteroctopus
megalocyathus. Forty specimens from Ancud and 37 from Quellón coming from artisanal catch from Chiloé Island in southern
Chile were examined. The size and density of the oocysts were quantified in the caecum and intestine of the host. Histological
preparations were carried out to determine quantitatively the occurrence of the different development stages of the parasite. In Ancud,
80 % of octopuses were parasited in the caecum and intestine, while in Quellón 100 % had oocyst. Four development stages
(microgametes, zygotes, immature and mature sporocysts) were recognized. The oocysts of Aggregata patagonica
were smaller and more abundant in the caecum, but their coverage was higher in the intestine. Moreover, density and coverage
increased in few months between samples. Apparently, Aggregata patagonica does not use the two
microhabitats as preferential places to pass the different developmental stages, but rather, and according to the conditions of the
microhabitat, the oocysts would grow more in the intestine albeit in small number, occupying a higher surface of the microhabitat,
contrary to what happens in the caecum. This suggests that A. patagonica may have two distinct life history
strategies.
Key words:
microhabitat,
Aggregata patagonica, Enteroctopus megalocyathus, oocysts
