MEPS 320:177-184 (2006)  -  doi:10.3354/meps320177

Diversity of Symbiodinium dinoflagellate symbionts from the Indo-Pacific sea slug Pteraeolidia ianthina (Gastropoda: Mollusca)

William K. W. Loh1,*, Melissa Cowlishaw1,2, Nerida G. Wilson1,3

1Centre for Marine Studies, University of Queensland, St Lucia, Queensland 4072, Australia
2Present address: School of Marine Biology and Aquaculture, James Cook University, Townsville, Queensland 4811, Australia
3Present address: Department of Biological Sciences, 101 Rouse Life Sciences Building, Auburn University, Auburn, Alabama 36849, USA

ABSTRACT: The aeolid nudibranch Pteraeolidia ianthina hosts symbiotic dinoflagellates in the same way as many reef-building corals. This widespread Indo-Pacific sea slug ranges from tropical to temperate waters, and offers a unique opportunity to examine a symbiosis that occurs over a large latitudinal gradient. We used partial 28S and 18S nuclear ribosomal (nr) DNA to examine the genetic diversity of the Symbiodinium dinoflagellates contained within P. ianthina. We detected Symbiodinium from genetic clades A, B, C and D. P. ianthina from tropical regions (Singapore, Sulawesi) host Symbiodinium clade C or D or both; those from the subtropical eastern Australian coast (Heron Island, Mon Repo, Moreton Bay, Tweed Heads) host Symbiodinium clade C, but those from the temperate southeastern Australian coastline (Port Stephens, Bare Island) host clade A or B or both. The Symbiodinium populations within 1 individual nudibranch could be homogeneous or heterogeneous at inter- or intra-clade levels (or both). Our results suggested that the Pteraeolidia-Symbiodinium symbiosis is flexible and favours symbiont phylotypes best adapted for that environment. This flexibility probably reflects the function of the symbiont clade in relation to the changing environments experienced along the latitudinal range, and facilitates the large geographic range of P. ianthina.


KEY WORDS: Symbiosis · Zooxanthellae · Nudibranchia · Molecular diversity · Biogeography


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