DN A sequence-based analysis of the gill parasite small subunit rRN A gene identifies the proposed causative agent as being closely related to the apostome ciliate Hyalophysa chattoni; however, morphological characteristics of the ciliate observed by electron microscopy are inconsistent with this identification.
KEY WORDS: penaeid shrimp, Apostome ciliate, black gill, parasite, fishery, next generation sequencing
In penaeid shrimp, unidentified apostome ciliate cysts are associated with black gill disease in the Gulf of Mexico (Couch 1978, Overstreet 1978).
Because the apostome ciliate Synophrya is known to cause black gill in decapod crustaceans (Johnson & Bradbury 1976) and the 18S rRNA from this organism had not previously been sequenced, it was sequenced in this study.
Similar "membrane organelles" are known from apostome ciliates.
When three nucleotide mismatches were allowed, other apostome ciliates were matched including Gymnodinoides pitelk ae (EU503534), Gymnodinoides sp.
This study reports on fishery and fishery-independent monitoring of sBG and suggests that the cause of the epidemic is an apostome ciliate closely related to Hyalophysa chattoni.
Based on its 18S rRNA gene sequence, the ciliate associated with sBG is closely related to the apostome ciliate Hyalophysa chattoni.
In silico and empirical specificity evaluation indicated that although the assay developed is theoretically specific to the genus Hyalophysa, in practice, the assay will amplify the 18S rRNA gene from Hyalophysa and closely related apostome ciliates.
Phylogenetic position of the apostome ciliates (Phylum ciliophora, subclass Apostomatia) tested using small subunit rRNA gene sequences.