engleski

Loggerhead sea-turtle-associated epizoic vs. non- epizoic diatoms: isolation, identification, and co-cultivation experiments

Marine vertebrates, such as manatees, dolphins, whales, or sea turtles, often harbor biofilm- forming diatoms on their external surfaces. Loggerhead sea turtles (Caretta caretta) are hosts to certain diatom taxa (e.g., Achnanthes elongata, Poulinea lepidochelicola) that are considered host-specific. Even though putative epizoic diatom taxa have not yet been found on other surfaces in the turtles’ environment, conclusive evidence supporting their exclusively epizoic lifestyle specificity is still lacking. Morphological and DNA metabarcoding data on sea turtle-associated diatom communities reveal the consistent presence of putative epizoic diatoms on the sea turtles’ carapace despite the higher abundance and, usually, faster growth of non-epizoic opportunistic diatom taxa. In this study, we isolated putative epizoic and non-epizoic diatoms from the carapace biofilm of incidentally caught loggerhead sea turtles, established monocultures, and identified them based on morphology (LM and SEM) and by sequencing molecular markers (rbcL and psbC genes). To investigate potential diatom interactions, which could affect diatom community composition on the turtle carapace, we co- cultivated epizoic (A. elongata), and two strains of non-epizoic (Psammodictyon panduriforme) diatoms and examined their respective growth. We hypothesized that, in the laboratory co-culture setup, the epizoic A. elongata and non-epizoic P. panduriforme change their growth rates in favor of the epizoic A. elongata. The initial results show that A. elongata grew faster when co-cultured with P. panduriforme strains, while the P. panduriforme strains did not show significant differences in growth. Our co-culturing setup cannot fully reflect the complexity of microbial interactions on the turtle carapace, however, it adds to the interpretation of data collected on epizoic diatoms and their lifestyle.

diatom, co-culture, growth

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