Zootaxa 4369 (4): 501–514 ISSN 1175-5326 (print edition) http://www.mapress.com/j/zt/ Article ZOOTAXA Copyright © 2018 Magnolia Press ISSN 1175-5334 (online edition) https://doi.org/10.11646/zootaxa.4369.4.3 http://zoobank.org/urn:lsid:zoobank.org:pub:A216E1AB-8A63-4E42-A525-5B161F8B5D00 Description of the first Caribbean Oscarellidae (Porifera: Homoscleromorpha) THIERRY PEREZ1,2 & CESAR RUIZ1 1Institut Méditerranéen de Biodiversité et d’Ecologie marine et continentale, CNRS, Aix Marseille Univ, IRD, Avignon Univ. Station Marine d’Endoume, chemin de la Batterie des Lions, 13007 Marseille, France 2E-mail: [email protected] Abstract The sponge class Homoscleromorpha has a challenging taxonomy and its systematics is still a matter of debate. A signif- icant effort has recently been deployed to better evaluate the diversity of these sponges, and each new exploration of cryp- tic habitats reveals new species. Although several undescribed or wrongly determined Oscarella-like sponges have been reported by different authors, the Oscarellidae family still lacks description of its true Caribbean representatives. The ex- ploration of various submarine caves in the Lesser Antilles has allowed us to find and to formally describe the first two Oscarellidae of the Caribbean Sea, Oscarella filipoi sp. nov. and Oscarella zoranja sp. nov. Both new species are quite common in semi-dark habitats throughout the Lesser Antilles. Moreover, O. filipoi sp. nov. is the largest Oscarellidae ever observed world-wide. Both species harbor a sylleibid aquiferous system and a high density of ovoid to spherical choano- cyte chambers. The molecular taxonomy clearly shows their affiliation to the Oscarella clade containing the type species of the Oscarellidae family. In addition to their growth forms, these two species differ in the shape of their mesohylar cells, and in the degree of development of their basal region. This latter trait is particularly remarkable in large specimens of O. filipoi which can have a very thick ectosome. Key words: Sponges, Homosclerophorida, Oscarella, Lesser Antilles, Submarine caves Introduction Sponge diversity is underestimated in a great number of the islands of the Lesser Antilles. A recent inventory performed in Martinique has begun to complete this knowledge gap, highlighting a reservoir of hidden sponge diversity dwelling in cryptic habitats such as crevices, overhangs, tunnels and submarine caves (Pérez et al. 2017). The knowledge gain was evident for Homoscleromorpha, with 11 species added after this inventory, including several new species. This sponge group was recently elevated to the rank of class (Gazave et al. 2012), and in spite of its challenging taxonomy, it presents one of the highest rates of new taxa descriptions (Cárdenas et al. 2012). The Caribbean Sea today counts 18 Homoscleromorpha species, but they currently belong to the Plakinidae family (Van Soest et al. 2017; Ruiz et al. 2017). Some of these species have been described recently, such as Oscarella nathaliae, which was the only Caribbean representative of the Oscarellidae family for three years (Ereskovsky, Lavrov & Willenz 2014; Ruiz et al. 2017). Indeed, one of the main motivations of Ereskovsky et al. (2014) in attempting to assign this new species to the genus Oscarella was its lack of a skeleton. However, later molecular evidence and the re-examination of certain morphological traits demonstrated that this species actually belongs to Plakina (Ruiz et al. 2017). The Plakinidae definition has been further overturned following the description of the new aspiculate sponge Aspiculophora madinina by Ruiz, Muricy, Lage, Domingos, Chenesseau & Pérez (2017). Consequently, the lack of a skeleton is no longer a specific characteristic of the Oscarellidae, and this family remains with no properly described Caribbean representatives. All former reports of Oscarella specimens referred to undescribed specimens or to wrongly named O. lobularis (Schmidt, 1862) (e.g. Vacelet 1998; Diaz & Van Soest 1994) which has long been thought to be cosmopolitan. Several research projects are currently underway to improve our knowledge of Caribbean sponge fauna, with particular attention paid to underwater cave communities similar to those in other seas where Homoscleromorpha Accepted by M. Klautau: 22 Nov. 2017; published: 8 Jan. 2018 501 were known to be an abundant and diverse taxonomic group (Ereskovsky et al. 2009; Gerovasileiou & Voultsiadou 2012). Every recently explored cave in the Lesser Antilles has revealed a huge diversity of this sponge Class (Fauvelot 2015; Pérez 2015). Descriptions have used an integrative taxonomy approach on the most common representatives (see Ruiz et al. 2017). Hereafter, we describe two new sympatric Oscarella species which were originally collected in Martinique Island and later in various islands of the Lesser Antilles. They are among the most common Homoscleromorpha species and were found in every semi-dark community investigated. One of these is the largest Oscarella ever recorded world-wide. Material and methods Sampling. Specimens were collected by SCUBA diving between June 2011 and April 2016 in the South of Martinique Island and during the PACOTILLES cruise across the Lesser Antilles, from Anguilla to Mayreau Island (May–June 2015) (Fig. 1). Some testimonies accompanied by underwater pictures were also used to delineate the distribution of the new species, but these records were not confirmed by samples. FIGURE 1. Sampling sites, current distribution of the two new Caribbean Oscarellidae ; black stars : Oscarella filipoi sp. nov. ; grey stars: Oscarella zoranja sp. nov. The two new species live in sympatry. All specimens were found on vertical walls, under horizontal rocky surfaces or on the ceilings of submarine caves varying in depth from very shallow (3 m) to 50 m depth.. Underwater photographs and general information, such as the size, shape, color and consistency, were registered for each individual. Each sample was fixed in 95% ethanol and in 2.5% glutaraldehyde for molecular and morphological analyses, respectively. Prior to further analysis, the absence of spicules was verified for each specimen. 502 · Zootaxa 4369 (4) © 2018 Magnolia Press PEREZ & RUIZ Cytology. A small fragment of each specimen was fixed in 2.5% glutaraldehyde in 2 M phosphate buffer and filtered sea water (1 vol: 4 vol: 5 vol), then post-fixed in 2% OsO4 in sea water (Boury-Esnault et al.1984). For semi-thin and ultra-thin sections, each fragment was embedded in AralditeTM. Semi-thin sections were stained with toluidine blue and observed under a Leica DMBL light microscope (LM). Ultra-thin sections were made using a RCMC ultramicrotome PTXL. The cuts were placed on a copper grid (3.05 mm in diameter, 300 mesh) and stained with 2% uranyl acetate for 15 min. Observations were carried out with a JEOL JEM-1400 transmission electron microscope (TEM). The cytological and prokaryotic compositions of each sample were analyzed, taking into account cell morphology, dimensions and cytoplasm characteristics. TABLE 1. NCBI data base accession numbers of specimens used for the molecular taxonomy. Specie Sample code Accession number Aspiculophora madinina KU674367.1 Plakinastrella onkodes EU237487 Plakortis halichondroides HQ269359.1 Plakortis angulospiculatus Plakina jani NC_014860.1 Corticium candelabrum HQ269363.1 Oscarella zoranja 131203MT3CR2 MG009495 Oscarella zoranja GR27HOM16 MG009496 Oscarella zoranja 150516MT8CR4 MG009497 Oscarella zoranja GR26HOM4 MG009498 Oscarella zoranja GR34HOM29 MG009499 Oscarella zoranja GR30HOM25 MG009500 Oscarella zoranja 110611MT4TP12 MG009501 Oscarella zoranja 110611MT3TP5 KX348266 Oscarella zoranja 150516MT4CR13 MG009502 Oscarella zoranja 150516MT1TP7 KX348267 Oscarella zoranja 150516MT4CR8 MG009503 Oscarella zoranja GR26HOM1 MG009504 Oscarella zoranja GR27HOM20 MG009506 Oscarella filipoi 131203MT3CR1 MG009507 Oscarella filipoi 120325MT1TP14 KX348268 Oscarella filipoi 120325MT4TP13 MG009508 Oscarella filipoi 120325MT1TP12 MG009509 Oscarella tuberculata 3170974238 Oscarella lobularis 317134132 Oscarella balibaloi Pseudocorticium jarrei HQ269357.1 Xestospongia muta EU237490.1 DNA analyses. For the molecular taxonomy study, we chose CO1 markers which had proved reliable in differentiating closely related species among Homoscleromorpha in previous works (see for instance Pérez et al. 2011; Boury-Esnault et al. 2013, Ruiz et al. 2015, 2017). DNA extractions were performed from small sponge fragments (2 cm3) using QIAamp DNA Mini Kit (QIAGEN). Universal primers C1-Npor2760 and C1-J2165 were used to amplify a 507-bp fragment (I3-M11) of the CO1 mitochondrial gene (Misof et al. 2000; Erpenbeck et al. 2006). Amplifications were done in a 40 µl total reaction volume with: 4 µl of each primer (10 µM), 6.4 µl dNTPs (10 mM), 8 µl polymerase buffer, 5 µl MgCl2 (25 mM), 0.2 µl Taq polymerase (5 U*µl-1), 2.4 µl extracted DNA DESCRIPTION OF THE FIRST CARIBBEAN OSCARELLIDAE Zootaxa 4369 (4) © 2018 Magnolia Press · 503 and 14 10 µl of ultrapure (Milli-Q) water. PCR were performed using a Mastercycler gradient PCR-S Eppendorf thermocycler with an initial step of 5 min at 94° C followed by 40 amplification cycles (denaturation at 94° C for 1 min; annealing at 42° C for 1 min; and extension at 72° C for 1 min), and a final extension step at 72° C for 5 min. PCR products were directly sequenced in each primer direction by the Eurofins laboratory (Ebersberg, Germany). To construct the phylogenetic tree, another four sequences were taken from