The HMA-LMA Dichotomy Revisited: an Electron Microscopical Survey of 56 Sponge Species

Volker Gloeckner, Markus Wehrl, Lucas Moitinho-Silva, Christine Gernert, Peter Schupp, Joseph R. Pawlik, Niels L. Lindquist, Dirk Erpenbeck, Gert Woerheide, Ute Hentschel

Research output: Contribution to journalArticlepeer-review

155 Scopus citations


The dichotomy between high microbial abundance (HMA) and low microbial abundance (LMA) sponges has been long recognized. In the present study, 56 sponge species from three geographic regions (greater Caribbean, Mediterranean, Red Sea) were investigated by transmission electron microscopy for the presence of microorganisms in the mesohyl matrix. Additionally, bacterial enumeration by DAPI-counting was performed on a subset of samples. Of the 56 species investigated, 28 were identified as belonging to the HMA and 28 to the LMA category. The sponge orders Agelasida and Verongida consisted exclusively of HMA species, and the Poecilosclerida were composed only of LMA sponges. Other taxa contained both types of microbial associations (e.g., marine Haplosclerida, Homoscleromorpha, Dictyoceratida), and a clear phylogenetic pattern could not be identified. For a few sponge species, an intermediate microbial load was determined, and the microscopy data did not suffice to reliably determine HMA or LMA status. To experimentally determine the HMA or LMA status of a sponge species, we therefore recommend a combination of transmission electron microscopy and 16S rRNA gene sequence data. This study significantly expands previous reports on microbial abundances in sponge tissues and contributes to a better understanding of the HMA-LMA dichotomy in sponge-microbe symbioses.
Original languageEnglish (US)
Pages (from-to)78-88
Number of pages11
JournalBiological Bulletin
Issue number1
StatePublished - 2014
Externally publishedYes


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