Investigation on parasites of wild day octopus (octopus cyanea) in selected indian ocean fishing sites in Tanga, Tanzania

Abstract

This is the first study done in Tanzania concerning with parasites of octopus, aimed to investigate parasites in Octopus cyanea along the Indian Ocean of Tanga region in Tanzania. Information from fishermen was required so as to determine their awareness on parasitic infections in octopus. Twenty five per cent (25.3%) agreed on the presence of parasites in octopus skin and muscles but these were not observed during laboratory investigation. Gamogony and sporogony of Aggregata sp (Apicomplexa: Aggregatidae) were observed during histopathological examination of the digestive tracts of octopuses collected along Tanga coastal area. Octopus cyanea was infected with coccidian parasite, Aggregata spp with a prevalence 41.1% (23 of 56 hosts examined) and organs like liver and gills were found be infected. Oocysts were sub-spherical in the mucosa wall of the intestine and caecum measuring 263 - 279 μm. Sporocysts were smooth‐surfaced, dark‐staining, spherical, typically 10–15 μm wide, and contained 9–22 banana-shaped sporozoites with a size of 2 -6 μm long and 0.2- 0.3μm wide. The coccidian infection in octopuses accompanied with replacement of the infected cells with sporocysts. Parasite infection of Aggregata spp was not significantly correlated with the weight of octopus, study site or sex of the host. Molecular analysis was used to confirm the parasite species in which 68% of samples were positive when PCR products visualized in 1.5% agarose gel. Molecular characterization revealed that the coccidian was the Aggregata octopiana after sequencing its 18S rRNA gene using designed Aggregata primers. Alignments revealed that the coccidian from O. cyanea resembled for 89% with Aggregata octopiana isolated from common Octopus in Spain. Despite of the presence of Aggregata octopiana in O. cyanea, the parasite does not cause any effects to consumers unless the octopus is infected with other epizootiological agent.