engleski

New observations on some sea turtle associated Craspedostauros species

The diatom genus Craspedostauros E.J.Cox (Cox 1999) currently comprises eleven, predominantly marine species. Craspedostauros taxa have been recorded from various habitats including Antarctic saline lakes, Red Sea plankton and diverse marine benthic environments worldwide. Morphological characteristics of the genus include a stauros narrower than the fascia, cells constricted at the center in girdle view, multiple narrow double-perforated girdle bands, cribrate areolae with four to many pores, and two H-shaped chloroplasts. Recently, a new species C. alatus Majewska & Ashworth (Majewska et al. 2018) was described from carapace samples of carcasses of Kemp’s ridley and green turtle, and a morphologically similar strain CCMP1120 was found in the UTEX culture collection isolated back in 1967 from the equatorial Pacific. During the survey of the diatom assemblages found on carapaces of sea turtles from the Adriatic Sea and Kosi Bay (eastern coast of South Africa) we observed several populations of four distinct Craspedostauros taxa. Specimens from the first population found on Adriatic loggerheads morphologically correspond to epizoic C. alatus in having the external wing-like structures near the valve apices and an elongated, weakly constricted rectelevatum. In addition, based on detailed SEM and LM observations of wild populations and cultivated strains we distinguish three new species, two of them from loggerhead carapaces and one found on leatherback-associated barnacles, Platylepas coriacea. The first unknown taxon has centrally constricted valves, irregularly shaped areolae with 2-6 cribrate pores, a rectelevatum with a central distinct silica knob and multiple rows of pores around the valve apex. The second loggerhead-associated taxon also possesses a central silica knob on a rectelevatum, but has square areolae with four cribrate pores and lip-like silica flaps covering the central raphe endings. The third taxon was found on epibiotic barnacles on leatherback turtles and possesses narrow linear valves and lacks the stauros resembling C. paradoxa Ashworth & Lobban – the first Craspedostauros with strongly reduced stauros. Our findings confirm that Craspedostauros taxa are not uncommon component of the sea turtle diatom flora. Currently, however, it is still uncertain whether these taxa prefer animal substrate or attach to the sea turtle carapace and barnacles opportunistically.

epizoic diatoms ; loggerhead sea turtles ; taxonomy ; new species

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