Diatom Diversity on the Skin of Frozen Historic Loggerhead Sea Turtle Specimens

Abstract

In recent years, biofilm-forming diatoms have received increased attention as sea turtle epibionts. However, most of the research has focused on carapace-associated taxa and communities, while less is known about diatoms growing on sea turtle skin. The current study investigated diatom diversity on the skin of loggerhead sea turtle heads detached from the carcasses found along the Adriatic coast between 1995 and 2004 and stored frozen for a prolonged period of time. By using both light and scanning electron microscopy we have found diatom frustules in 7 out of 14 analysed sea turtle samples. Altogether, 113 diatom taxa were recorded, with a minimum of seven and a maximum of 35 taxa per sample. Eight taxa, Achnanthes elongata, Berkeleya cf. fennica, Chelonicola sp., Licmophora hyalina, Nagumoea sp., Navicula sp., Nitzschia cf. lanceolata, and Poulinea lepidochelicola exceeded 5% of relative abundance in any one sample. The presumably obligately epizoic diatom taxa, A. elongata, Chelonicola sp., and P. lepidochelicola, dominated in six loggerhead samples, contributing up to 97.1% of the total diatom abundance. These observations suggest that on the sea turtle skin highly specialised taxa gain even greater ecological advantage and dominance over the co-occurring benthic forms than in the carapace biofilms. The suitability of frozen sea turtle skin specimens for diatom analysis and limitations of this approach are discussed.

Surface microbiota of Mediterranean loggerhead sea turtles unraveled by 16S and 18S amplicon sequencing

“…The epimicrobiomes of sea turtles, in turn, have received far less attention. Recent years brought increased interest in 10.3389/fevo.2022.907368 micro-eukaryotic surface assemblages of sea turtles largely due to a series of projects exploring the diversity of sea turtleassociated diatoms (Majewska et al, 2015;Robinson et al, 2016;Rivera et al, 2018;Azari et al, 2020;Kanjer et al, 2020;Van de Vijver et al, 2020). Those studies identified a group of the diatom core taxa typical of sea turtles but also showed some biogeographic differences between diatom epizoic assemblages ( Van de Vijver et al, 2020).…”

Surface microbiota of Mediterranean loggerhead sea turtles unravelled by 16S and 18S amplicon sequencing

“…The epimicrobiomes of sea turtles, in turn, have received far less attention. Recent years brought increased interest in micro-eukaryotic surface assemblages of sea turtles largely due to a series of projects exploring the diversity of sea turtle-associated diatoms (Majewska et al, 2015; Robinson et al, 2016; Rivera et al, 2018; Azari et al, 2020; Kanjer et al, 2020; Van de Vijver et al, 2020). Those studies identified a group of the diatom core taxa typical of sea turtles but also showed some biogeographic differences between diatom epizoic assemblages (Van de Vijver et al, 2020).…”