Reassessment of Homology of Morphological Characters in Tetractinellid Sponges Based on Molecular Data

Abstract

In sponges, as in other taxa with simple organization, the evaluation and use of morphological characters is difficult. Phylogenetic analysis of the first 850 nucleotides from the 5' end of the 28S rRNA gene is used here to assess the homology of spicules used in the classification of the subclass Tetractinellida. A single well-supported MP tree was obtained. The monophyly of the nine Tetractinellida species studied confirms the tetraxon megasclere as a morphological synapomorphy for the Tetractinellida. Two species are reallocated, Penares helleri as a Geodiidae, now thought to have lost sterraster microscleres, and Stryphnus mucronatus to the Streptosclerophorida. SEM micrographs of Stryphnus microscleres show that the morphology of the sanidasters is compatible with the hypothesis that they are homologous with streptoscleres and confirm this reallocation. Two other synapomorphies are confirmed within the tetractinellid clade, the simultaneous presence of tetraxon megasclere and aster-type microsclere (Astrophorida) and the loss of the streptosclere and persistence of the euaster s.s. microscleres (Euastrophorida) evidenced by the reallocation of Stryphnus mucronatus. The streptosclere microscleres cannot be evaluated in terms of homology because Streptosclerophorida may be paraphyletic (although these nodes are not supported by reliable bootstrap proportions) contrary to the currently accepted classification.

Two new desma-less species of Theonella Gray, 1868 (Demospongiae: Astrophorida: Theonellidae), from the Great Barrier Reef, Australia,and a re-evaluation of one species assigned previously to Dercitus Gray, 1867

“…Early molecular studies of the Astrophorida (Chombard et al 1998), based on 28S rDNA genes, indicated that although streptasters appeared early within the Astrophorida, they were lost subsequently in higher groups on the tree, such as the Geodiidae and Calthropellidae. Although branch support for deeper relationships is limited, our phylogenetic trees are in contrast with that presented by Chombard et al (1998), indicating that clades bearing streptasters (e.g.…”

A new species of the calcareous sponge genus Leuclathrina (Calcarea: Calcinea: Clathrinida) from the Maldives

“…DNA of two specimens (SNSB-BSPG GW3934 and SNSB-BSPG GW4029) was extracted with the NucleoSpin Tissue kit (Macherey-Nagel); extracted DNA was quantified using a nanodrop. About 1 ng of genomic DNA was used as template in 25 µl reaction-mixes to amplify the C-region of the 28S ribosomal RNA (rRNA) gene by PCR with the following primers: fwd: 5'-GAAAAGAACTTTGRARAGAGAGT-3' and rv: 5'-TCCGTGTTTCAAGACGGG-3' (Chombard et al 1998) Alignment and phylogenetic analysis. The sequences of L. translucida sp.…”

Molecular biodiversity of Red Sea demosponges

“…For the 28S fragment the primers 28S-C2-fwd (GAA AAG AAC TTT GRA RAG AGA GT) and 28S-D2-rev (TCC GTG TTT CAA GAC GGG) were used (Chombard et al, 1998). The 25 µL PCR mix consisted of 5 µL 5x green GoTaq ® PCR Buffer (Promega Corp, Madison, WI), 4µL 25mM MgCl2 (Promega Corp, Madison, WI), 2 µL 10mM dNTPs, 2 µL BSA (100µg/ml), 1 µL each primer (5µM), 7.8 µL water, 0.2µL GoTaq® DNA polymerase (5u/μl) (Promega Corp, Madison, WI) and 2 µL DNA template.…”

“…This marker shows considerable phylogenetic signal on lower taxonomic levels (e.g., Chombard et al, 1998;Erpenbeck et al, 2007a;Cardenas et al, 2009;Schuster et al, 2015) and has also been successfully applied for the molecular taxonomy of Calcarea (Voigt and Wörheide, 2016).…”