AUTHOR=Cárdenas Paco 

TITLE=Surface Microornamentation of Demosponge Sterraster Spicules, Phylogenetic and Paleontological Implications

JOURNAL=Frontiers in Marine Science

VOLUME=7

YEAR=2020

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2020.613610

DOI=10.3389/fmars.2020.613610

ISSN=2296-7745

ABSTRACT=<p>Siliceous spicules in demosponges exist in a variety of shapes, some of which look like minute spheres of glass. They are called “sterrasters” when they belong to the Geodiidae family (Tetractinellida order) and “selenasters” when they belong to the Placospongiidae family (Clionaida order). Today, the Geodiidae represent a highly diverse sponge family with more than 340 species, occurring in shallow to deep waters worldwide, except for the Antarctic. The molecular phylogeny of Geodiidae is currently difficult to interpret because we are lacking morphological characters to support most of its clades. To fill this knowledge gap, the surface microornamentations of sterrasters were compared in different genera. Observations with scanning electron microscopy revealed four types of surfaces, which remarkably matched some of the Geodiidae genera: type I characteristic of <italic>Geodia</italic>, type II characteristic of <italic>Pachymatisma, Caminus</italic>, and some <italic>Erylus</italic>; type III characteristic of other <italic>Erylus</italic>; type IV characteristic of <italic>Caminella</italic>. Two subtypes were identified in <italic>Geodia</italic> species: warty vs. smooth rosettes. These different microornamentations were mapped on new Geodiidae <italic>COI</italic> (Folmer fragment) and <italic>28S (C1–D2)</italic> phylogenetic trees. The monophyly of the Geodiidae was once again challenged, thereby suggesting that sterrasters have evolved independently at least three times: in the Geodiinae, in the Erylinae and in <italic>Caminella</italic>. Surface microornamentations were used to review the fossil record of sterrasters and selenasters through the paleontology literature and examination of fossils. It was concluded that “rhaxes” in the literature may represent mixes of sterrasters and selenasters: while <italic>Rhaxella</italic> spicules may belong to the Placospongiidae, <italic>Rhaxelloides</italic> spicules belong to the Geodiidae. The putative Geodiidae fossil genera, <italic>Geoditesia</italic>, and <italic>Geodiopsis</italic>, are reallocated to Tetractinellida <italic>incertae sedis</italic>. Isolated Miocene-Pliocene fossil sterrasters <italic>Hataina</italic> (<xref ref-type="bibr" rid="B45">Huang, 1967</xref>), <italic>Silicosphaera</italic> (<xref ref-type="bibr" rid="B46">Hughes, 1985</xref>) and <italic>Conciliaspongia</italic> (<xref ref-type="bibr" rid="B90">Robinson and Haslett, 1995</xref>) become junior synonyms of <italic>Geodia</italic> (<xref ref-type="bibr" rid="B57">Lamarck, 1815</xref>). Overall, the fossil record suggested that Geodiidae was present at least since the Middle Jurassic (163–166 Mya), while <italic>Geodia</italic> sterrasters were present since the Santonian/Campanian boundary, Late Cretaceous (83.6 Mya).</p><sec><title>ZooBank Article Registration</title><p>urn:lsid:<ext-link ext-link-type="uri" xlink:href="http://zoobank.org/" xmlns:xlink="http://www.w3.org/1999/xlink">zoobank.org</ext-link>:pub:91B1B3AC-8862-4751-B272-8A3BDF4DEE77.</p></sec>