Sycettusa Haeckel, 1872

Van, Rob W. M. & De, Nicole J., 2018, Calcareous sponges of the Western Indian Ocean and Red Sea, Zootaxa 4426 (1), pp. 1-160 : 112

Genus Sycettusa Haeckel, 1872

Sycetta (Sycettusa) Haeckel, 1872: 236

? Grantilla Row, 1909: 187 ; Borojević et al. 2002b: 1176.

Remarks. According to the Systema Porifera, chapter on the order Leucosolenida by Borojević et al. 2002b, Sycettusa Haeckel, 1872 and Grantilla Row, 1909 , differ only in the presence in the latter of pseudosagittal tetractines in addition to pseudosagittal triactines. We borrowed two slides of the type specimen of Grantilla quadriradiata Row, 1909 from the collections of the Natural History Museum, London, BMNH 1912.2.1.8a. This species is the type and only member of the genus Grantilla recognized by Borojević et al. 2002b. The slides consisted of sections and dissociated spicule mounts. Remarkably these did not contain a single recognizable subcortical pseudosagittal tetractine, but instead had only pseudosagittal triactines (called ‘prochiacts’ by Row). There was not a single tetractine in the borrowed material, despite its alleged occurrence in the extensive description of Row (1909, p. 198). We studied a number of Sycettusa specimens answering to the description of Grantilla hastifera Row, 1909 , and these are not separable from the studied type material of Grantilla quadriradiata . We propose to consider Grantilla a junior synonym of Sycettusa because even if Row’s material ultimately will be found to contain a few quadriradiate pseudosagittal spicules, their rarity and overall similarity with Sycettusa hastifera is hardly a difference meriting generic distinction.

Sycettusa was erected by Haeckel (1872), as a subgenus of his genus Sycetta , for type species Sycetta stauridia Haeckel, 1872 , but subsequently he refrained from using the combination. He did use a further combination Sycothamnus stauridia in his confusing artificial system as a ‘generische Individualität’, a remnant from his 1870 Prodomus, which is hopefully to be suppressed in the near future as a source for named sponge taxa.

A further issue in the genus Sycettusa is the lack of differentiation in the complement of the spicules and their sizes and shapes in many forms that differ distinctly in habitus (color, shape, size, oscular openings and protruding diactines). Apparently, overall shape is an important marker for species recognition.

We obtained several partial 28S sequences of members of the genus, some of which tend to support specific distinction of specimens showing very little differentiation in their spicule complement. The genus appears to be non-monophyletic in our phylogeny of Fig. 3 , with Sycettusa zanzibaris ( Jenkin, 1908) and New Caledonian S. tenuis Borojević & Klautau, 2000 grouped with Grantessa cf. intusarticulata , separated from a predominantly Red Sea group of Sycettusa species by Grantessa woerheidei , and Uteopsis and Ute . As argued above, the small number of Calcaronea partial 28S rRNA sequences, may be responsible for this inconsistent result. Nevertheless, it may be possible that Sycettusa is genuinely non-monophyletic.

Figures

FIGURE 3. Maximum-likelihood tree based on analysis of sequences of the partial 28S gene (C2–D2 region, comprising 461 sites) of Western Indian Ocean Calcaronea newly generated by the Naturalis Biodiversity Center and sequences additionally obtained from GenBank, the Sponge Barcode Project and from Oliver Voigt (München) from the Red Sea, Indonesia, Australia, and a few sequences from other parts of the world, to demonstrate the affiliation of the compared species. Numbers at the root of clades are bootstrap values of 1000 replicates.