Bacterial communities of oceanic sea star (Asteroidea: Echinodermata) larvae
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Planktotrophic sea star larvae of several species are abundant in oligotrophic waters of the Gulf Stream, western Sargasso Sea, and Caribbean Sea. One abundant larval morphotype at the bipinnaria stage of development is unusual in its ability to constitutively produce clones and in harboring a community of auto-fluorescent bacteria. We hypothesized that the bacterial community would be distinct in these larvae compared to those that do not consistently reproduce clonally. Three sea star larval morphotypes were collected in the Gulf Stream off the coast of Florida. We used DNA-based maximum likelihood phylogenetic analyses to taxonomically classify the larvae and 16S rDNA profiling by deep sequencing to characterize the bacterial communities harbored within. The cloning bipinnaria and non-cloning brachiolaria morphotypes were determined to be a single species of Asteroidea in the family Oreasteridae. The third morphotype, a non-cloning bipinnaria, was identified as Mithrodia clavigera. With bacterial 16S rDNA profiling, we found that the two species of larvae harbor bacterial communities distinct from each other. The Oreasteridae bacterial community at both developmental stages has a photosynthetic Cyanobacteria Synechococcus sp. as the most abundant bacteria. The M. clavigera larvae host a flora consisting primarily of Gammaproteobacteria. The identification of the larval microbiomes is a step toward understanding their host–microbe interactions. Specifically, the association of photosynthetic bacteria with cloning larvae allows for future assessments of whether the bacteria supplement the nutrition of the larvae during extended periods of development and clonal reproduction in open ocean regions where phytoplankton food for the larvae may be in limited supply.
KeywordsBacterial Community Synechococcus Gulf Stream Prochlorococcus Brittle Star
We would like to thank Dr. Simon Coppard for sharing the Panamanian Oreaster reticulatus sequence, Boyan Alexandrov and Dr. Francisco A. Solis-Marin for adult sea star tissues, Timm Hamp for help with Sanger sequencing, Michael Zianni and Anthony McCoy for the 454 sequencing, Dr. Anthony Fodor for help with bacterial 16S sequence analysis and manuscript comments, Monique Cristina Dos Santos for her sequencing work, and the reviewers for their helpful comments. This material is based upon work supported by the National Science Foundation under Grant Number 1036416 and an REU supplement for joint work with the students of Carlos Renato Rezende Ventura supported by the Brazilian Federal Ministry of Education (CAPES Coordenação de Aperfeiçoamento de Pessoal de Nível Superior).
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