New insights into the association between epizoic diatoms and the sea turtle Chelonia mydas: new Mastogloia taxon (Bacillariophyceae) from Iran

ABSTRACT Two epizoic species of Mastogloia, one of them a new taxon, have been found for the first time growing on the carapace of sea turtle Chelonia mydas from the Strait of Hormuz (Iran). Before this work, taxa belonging to the genus Mastogloia had never been identified as epibionts of C. mydas. The cleaned material of diatoms, collected from turtle carapaces was studied by light (LM) and scanning electron microscopy (SEM). Mastogloia hormuzensis sp. nov. is elliptical to linear-elliptical in valve view with rounded to slightly rostrate apices. Partecta are of different size and shape, with the larger one at the centre, and there is a very short partectal flange. The new epizoic diatom is unique in its morphology, and can be compared with Mastogloia exigua and M. pusilla, which show a similar combination of characters (e.g. the shape of areolae, type of partectal ring). Mastogloia hormuzensis sp. nov. fits into Hustedt’s species group Inaequales, to which it adds the feature of having a very short partecta flange. A second species, Mastogloia paradoxa, was also found living as epizoic for the first time.