Open Access Highly Accessed Open Badges Research article

Molecular evidence for a diverse green algal community growing in the hair of sloths and a specific association with Trichophilus welckeri (Chlorophyta, Ulvophyceae)

Milla Suutari1, Markus Majaneva2, David P Fewer3, Bryson Voirin4, Annette Aiello5, Thomas Friedl6, Adriano G Chiarello7 and Jaanika Blomster1*

Author Affiliations

1 Department of Environmental Sciences, P.O.Box 65, FIN-00014, University of Helsinki, Helsinki, Finland

2 Tvärminne Zoological Station, J.A. Palménin tie 260, FIN-10900 Hanko, Finland

3 Department of Food and Environmental Sciences, P.O. Box 66, FIN-00014, University of Helsinki, Helsinki, Finland

4 Max-Planck Institute for Ornithology, Schloß Möggingen, Schloßallee 2, 78315 Radolfzell, Germany

5 Smithsonian Tropical Research Institute, Apartado 0843-03092 Balboa, Ancon, Rep. Panama

6 Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Abteilung Experimentelle Phykologie and Sammlung für Algenkulturen, Universität Göttingen, Untere Karspüle 2, 37073 Göttingen, Germany

7 Catholic University of Minas Gerais, Programa de pós-graduação em Zoologia de Vertebrados, Av. Dom José Gaspar 500, Prédio 41, Belo Horizonte, MG, CEP: 30.535-610, Brazil

For all author emails, please log on.

BMC Evolutionary Biology 2010, 10:86  doi:10.1186/1471-2148-10-86

Published: 30 March 2010



Sloths are slow-moving arboreal mammals inhabiting tropical rainforests in Central and South America. The six living species of sloths are occasionally reported to display a greenish discoloration of their pelage. Trichophilus welckeri, a green algal species first described more than a century ago, is widely believed to discolor the animals fur and provide the sloth with effective camouflage. However, this phenomenon has not been explored in any detail and there is little evidence to substantiate this widely held opinion.


Here we investigate the genetic diversity of the eukaryotic community present in fur of all six extant species of sloth. Analysis of 71 sloth hair samples yielding 426 partial 18S rRNA gene sequences demonstrates a diverse eukaryotic microbial assemblage. Phylogenetic analysis reveals that sloth fur hosts a number of green algal species and suggests that acquisition of these organisms from the surrounding rainforest plays an important role in the discoloration of sloth fur. However, an alga corresponding to the morphological description of Trichophilus welckeri was found to be frequent and abundant on sloth fur. Phylogenetic analysis demonstrated the retention of this alga on the fur of sloths independent of geographic location.


These results demonstrate a unique diverse microbial eukaryotic community in the fur of sloths from Central and South America. Our analysis streghtens the case for symbiosis between sloths and Trichophilus welckeri.