engleski

Phylogeny and q-PCR detection of Aggregata octopiana (Aggregatidae, Apicomplexa) parasitising digestive tissues of common octopus (Octopus vulgaris) from the Adriatic Sea

Aggregata octopiana (Aggregatidae, Apicomplexa) is the most prevalent coccidian in the wild common octopus (Octopus vulgaris), whose heteroxenous life cycle includes gamogony and sporogony in the octopus digestive tract. In the intensively infected reared octopi, an unusual extraintestinal distribution of the coccidian, with both gamogony and sporogony ongoing in dermal and gill tissues can be observed, often leading to mortalities in the aquaculture environment. Although with a 100% prevalence in adult octopi in the wild, there is scarce data concerning phylogenetic diversity of Aggregata sp. in the Adriatic Sea. Recently, a study analysed a locus of 18S rRNA gene of A. octopiana from the NE Atlantic coast and compared it to a single sequence previously isolated from the Adriatic Sea, revealing considerable genetic distance between two A. octopiana lineages that suggested the existence of two species. Therefore, the aim of our study was to isolate apicomplexan from wild octopi sampled through wide geographical area of the East Adriatic Sea and asses its phylogenetic relationship within and outside the Adriatic using PCR. For the analysis, we used two primer pairs that amplified 1000 and 600 bps of partial 18S rRNA sequence, respectively. Faced with an often varying success of locus amplification by PCR, being correlated with the scarce quantity of apicomplexan oocysts, we also developed a q-PCR assay for more sensitive quantification of the parasites in octopus tissues. Phylogenetic analysis of A. octopiana population evidenced a panmictic character of the parasite within the Adriatic, while comparison with Atlantic lineages supported previous hypothesis of potential species differentiation. Q-PCR proved to be a successful tool for quantification of low-level infections.

Coccidia; phylogenetic diversity; partial 18S rRNA

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