title: The HMA-LMA dichotomy revisited: an electron microscopical survey of 56 sponge species.
abstract: 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.
authors.affiliation: Julius-von-Sachs Institute for Biological Sciences, Department of Botany II, University of Wuerzburg, Julius-von-Sachs Platz 3, 97082 Wuerzburg, Germany;
authors.forename: Volker
authors.initials: V
authors.lastname: Gloeckner
authors.affiliation: Julius-von-Sachs Institute for Biological Sciences, Department of Botany II, University of Wuerzburg, Julius-von-Sachs Platz 3, 97082 Wuerzburg, Germany;
authors.forename: Markus
authors.initials: M
authors.lastname: Wehrl
authors.affiliation: Julius-von-Sachs Institute for Biological Sciences, Department of Botany II, University of Wuerzburg, Julius-von-Sachs Platz 3, 97082 Wuerzburg, Germany;
authors.forename: Lucas
authors.initials: L
authors.lastname: Moitinho-Silva
authors.affiliation: Julius-von-Sachs Institute for Biological Sciences, Department of Botany II, University of Wuerzburg, Julius-von-Sachs Platz 3, 97082 Wuerzburg, Germany;
authors.forename: Christine
authors.initials: C
authors.lastname: Gernert
authors.affiliation: Carl-von-Ossietzky University Oldenburg, Institute for Chemistry and Biology of the Marine Environment (ICBM), Schleusenstr. 1, 26382 Wilhelmshaven, Germany;
authors.forename: Peter
authors.initials: P
authors.lastname: Schupp
authors.affiliation: Department of Biology and Marine Biology, Center for Marine Science, University of North Carolina Wilmington, North Carolina, USA;
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Pawlik
authors.affiliation: Institute of Marine Sciences, University of North Carolina at Chapel Hill, North Carolina, USA;
authors.forename: Niels L
authors.initials: NL
authors.lastname: Lindquist
authors.affiliation: Department of Earth and Environmental Sciences, Palaeontology & Geobiology, & GeoBio-Center, Ludwig-Maximilians-Universität München, Richard-Wagner-Str. 10, 80333 München, Germany; and.
authors.forename: Dirk
authors.initials: D
authors.lastname: Erpenbeck
authors.affiliation: Department of Earth and Environmental Sciences, Palaeontology & Geobiology, & GeoBio-Center, Ludwig-Maximilians-Universität München, Richard-Wagner-Str. 10, 80333 München, Germany; and SNSB-Bayerische Staatssammlung für Paläontologie und Geologie, Richard-Wagner-Str. 10, 80333 München, Germany.
authors.forename: Gert
authors.initials: G
authors.lastname: Wörheide
authors.affiliation: Julius-von-Sachs Institute for Biological Sciences, Department of Botany II, University of Wuerzburg, Julius-von-Sachs Platz 3, 97082 Wuerzburg, Germany; ute.hentschel@uni-wuerzburg.de.
authors.forename: Ute
authors.initials: U
authors.lastname: Hentschel
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D001419:Bacteria / Q000235:genetics; D018407:Bacterial Physiological Phenomena; D044822:Biodiversity; D004269:DNA, Bacterial / Q000235:genetics; D019156:Indian Ocean; D007211:Indoles; D008522:Mediterranean Sea; D064307:Microbiota; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D010802:Phylogeny; D011161:Porifera / Q000382:microbiology* / Q000648:ultrastructure*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013559:Symbiosis / Q000502:physiology*
chemical_list: D004269:DNA, Bacterial; D007211:Indoles; D012336:RNA, Ribosomal, 16S; C007293:DAPI