Systematics and Molecular Phylogeny of the Family Oscarellidae (Homoscleromorpha) with Description of Two New Oscarella Species

Abstract

The family Oscarellidae is one of the two families in the class Homoscleromorpha (phylum Porifera) and is characterized by the absence of a skeleton and the presence of a specific mitochondrial gene, tatC. This family currently encompasses sponges in two genera: Oscarella with 17 described species and Pseudocorticium with one described species. Although sponges in this group are relatively well-studied, phylogenetic relationships among members of Oscarellidae and the validity of genus Pseudocorticium remain open questions. Here we present a phylogenetic analysis of Oscarellidae using four markers (18S rDNA, 28S rDNA, atp6, tatC), and argue that it should become a mono-generic family, with Pseudocorticium being synonymized with Oscarella, and with the transfer of Pseudocorticium jarrei to Oscarella jarrei. We show that the genus Oscarella can be subdivided into four clades, each of which is supported by either a small number of morphological characters or by molecular synapomorphies. In addition, we describe two new species of Oscarella from Norwegian fjords: O. bergenensis sp. nov. and O. nicolae sp. nov., and we compare their morphology, anatomy, and cytology with other species in this genus. Internal anatomical characters are similar in both species, but details of external morphology and particularly of cytological characters provide diagnostic features. Our study also confirms that O. lobularis and O. tuberculata are two distinct polychromic sibling species. This study highlights the difficulties of species identification in skeleton-less sponges and, more generally, in groups where morphological characters are scarce. Adopting a multi-marker approach is thus highly suitable for these groups.

The Conservation of the Germline Multipotency Program, from Sponges to Vertebrates: A Stepping Stone to Understanding the Somatic and Germline Origins

“…6 A ). These cytological features are commonly found in what was defined as archeocytes in most sponges (Ereskovsky 2010; Funayama 2010) including closely related Oscarella species (Gazave, Lavrov, et al. 2013).…”

Kinetid structure of choanoflagellates and choanocytes of sponges does not support their close relationship

“…In spite of only having limited data on the choanocyte kinetid structure in the class Homoscleromorpha, we can make some preliminary assumptions based on the occurrence of the selected types of kinetid on the Homoscleromorpha phylogenetic tree (Gazave et al, 2013;Wörheide et al, 2012). Since the "Corticium" kinetid type was noted in two genera of Plakinidae and in Fig.…”

Taxonomy of family Plakinidae (Porifera: Homoscleromorpha) from eastern Pacific coral reefs, through morphology andcox1andcob mtDNA data

“…), the relationships within Oscarellidae agreed with the two gene fragments that we used. These results are congruent with the current molecular hypothesis, which suggests the potential synonymy of Oscarella and Pseudocorticium ; consequently Oscarellidae would be a monogeneric family (Gazave et al ., ).…”

“…The highest species diversity of Homoscleromorpha is present in the Caribbean, Mediterranean, and West Pacific areas (Muricy & Díaz, ; Ereskovsky et al ., ; Muricy, ; Ereskovsky et al ., ). This is probably because of a larger tradition of sponge systematic studies (Ereskovsky et al ., , ; Gazave et al ., , ), whereas other areas remain poorly known. In the eastern Pacific region, in the 1980s there was no record of Homoscleromorpha, but in the last few years, the number of species has significantly increased (see below) (Green & Bakus, ; Desqueyroux‐Faúndez & van Soest, ; Muricy & Pearse, ; Cruz‐Barraza & Carballo, ; Lehnert, Stone & Heimler, ; van Soest, Kaiser & Syoc, ).…”

“…Several species are also known for their production of biologically active substances, many of which have potential value in the pharmacological field (Berrué et al, 2005;Holzwarth et al, 2005). As a result of this, the number of new species (Muricy, 2011;Ereskovsky, Lavrov & Willenz, 2014;Gazave et al, 2013) and studies on the phylogenetic relationships of the group have substantially increased in the last few years (see Borchiellini et al, 2004;Peterson et al, 2008;Sperling, Pisani & Peterson, 2007;Philippe et al, 2009;Sperling, Peterson & Pisani, 2009;Gazave et al, 2010Gazave et al, , 2013Ivanisêvić et al, 2011;Boury-Esnault et al, 2013).…”