Standing on the shoulders of giants

Marine mammals and sea turtles host rich diatom floras, and current evidence indicates that these associations have driven the evolution of new species and novel traits. The fate of these diatom communities is inextricably linked to their hosts, many of which are threatened by extinction.

Nearly 50 species of obligately epizoic marine diatoms have been described from the skins of West Indian manatees (Frankovich et al. 2018), cetaceans (Holmes et al. 1993; Denys, 1997), and sea turtles (e.g., Majewska et al. 2018). Despite this progress, epizoic diatom communities are an important reservoir of undescribed species (Majewska et al. 2019) and novel metabolic diversity (Frankovich et al. 2018).

This project will describe new species of obligately epizoic diatoms, and a phylogeny of these diatoms will be constructed and used to test hypotheses about origins, host associations, and genome evolution of epizoic diatoms. The functional relationships between diatoms and their hosts are likely mediated, in part, by symbiotic bacteria. Multi-omics approaches will reveal the extent to which diatoms rely on host- and bacterial-derived metabolites, which may underlie the narrow host specialization of some species and, in one special case, the switch to heterotrophy in the genus Tursiocola—a trophic shift that has occurred only one other time in diatoms.

REFERENCES

Frankovich TA, Ashworth MP, Sullivan MJ, Theriot EC and Stacy NI. 2018. Epizoic and apochlorotic Tursiocola species (Bacillariophyta) from the skin of Florida manatees (Trichechus manatus latirostris). Protist 169: 539–568.

Holmes, R. W., Nagasawa, S., and Takano, H. (1993). The morphology and geographic distribution of epidermal diatoms of the Dall’s porpoise (Phocoenoides dalli True) in the Northern Pacific Ocean. Bulletin of the National Science Museum, Tokyo Series B 19: 1–18.

Denys L. 1997. Morphology and taxonomy of epizoic diatoms (Epiphalaina and Tursiocola) on a sperm whale (Physeter macrocephalus) stranded on the coast of Belgium. Diatom Research 12: 1–18.

Majewska R, De Stefano M and Van de Vijver B. 2018. Labellicula lecohuiana, a new epizoic diatom species living on green turtles in Costa Rica. Nova Hedwigia Beiheft 146: 23–31.

Majewska R, Bosak S, Frankovich TA, Ashworth MP, Sullivan MJ, Robinson NJ, Lazo-Wasem EA, Pinou T, Nel R, Manning SR, et al. 2019. Six new epibiotic Proschkinia (Bacillariophyta) species and new insights into the genus phylogeny. European Journal of Phycology 54: 609–631