Cytological evidence for cryptic speciation in MediterraneanOscarellaspecies (Porifera, Homoscleromorpha)

Abstract

Three new sponge species without a skeleton, Oscarella viridis, O. microlobata, and O. imperialis, were found in sublittoral caves and on vertical walls along the coast of Provence (western Mediterranean Sea, France). Their morphology, anatomy, and cytology are described and they are compared with the two other valid Mediterranean Oscarella species, O. lobularis and O. tuberculata. Reproductive and internal anatomical characters are uniform in the genus, but details of external morphology and especially cytological characters (mesohylar cells with inclusions) provide good diagnostic features at the species level. Careful observation of morphological and cytological characters is essential for clarifying the systematics of Oscarella and reveals an unexpected biodiversity of this genus in the Mediterranean Sea.

Metabolic fingerprinting as an indicator of biodiversity: towards understanding inter-specific relationships among Homoscleromorpha sponges

“…Taxonomy of Homoscleromorpha is highly challenging and their phylogeny remains debated, because many species are devoid of skeleton (Borchiellini et al 2004;Ereskovsky 2009a;Nichols 2005;Philippe et al 2009). This lack of convenient morphological character makes Oscarella lobularis a typical example of a sponge species that has been considered for a long time as ''cosmopolitan'' and finally turned out to be a highly diversified complex of different species (Boury-Esnault et al 1992;Muricy et al 1996), with potential new species. For such a problematic sponge group, it has been necessary to describe in details the cytology and associated bacteria for each species identification (Muricy 1999;Muricy et al 1999).…”

A molecular phylogeny and historical biogeography of the marine sponge genus Placospongia (Phylum Porifera) indicate low dispersal capabilities and widespread crypsis

“…There is widespread opinion that sponges do not disperse far (Maldonado and Young, 1996;Lindquist et al, 1997;Uriz et al, 1998;Maldonado and Bergquist, 2002), despite the fact that different sponge species exhibit a range of reproductive strategies (Maldonado and Bergquist, 2002) and life histories that possibly result in a range of dispersal outcomes. The existence of sponge species with cosmopolitan distributions has stood in apparent contradiction to the prediction that sponges are capable of only short-distance dispersal but a number of studies have demonstrated that cosmopolitanism is often just a case of boverconservative systematicsQ due to the paucity of morphological characters useful for fine-scale species discrimination (Sole-Cava and Thorpe, 1986;BouryEsnault et al, 1992;Sole-Cava et al, 1992;Klautau et al, 1994Muricy et al, 1996;Wörheide et al, 2003). Most cosmopolitan species [with notable exceptions as given in Lazoski et al (2001)], when evaluated using molecular genetic techniques, are found to encompass cryptic species diversity and high levels of population genetic structure on geographic scales more compatible with hypotheses of limited dispersal ability (Sole-Cava and Thorpe, 1986;BouryEsnault et al, 1992;Sole-Cava et al, 1992;Klautau et al, 1994Muricy et al, 1996;Wörheide et al, 2003).…”

“…The existence of sponge species with cosmopolitan distributions has stood in apparent contradiction to the prediction that sponges are capable of only short-distance dispersal but a number of studies have demonstrated that cosmopolitanism is often just a case of boverconservative systematicsQ due to the paucity of morphological characters useful for fine-scale species discrimination (Sole-Cava and Thorpe, 1986;BouryEsnault et al, 1992;Sole-Cava et al, 1992;Klautau et al, 1994Muricy et al, 1996;Wörheide et al, 2003). Most cosmopolitan species [with notable exceptions as given in Lazoski et al (2001)], when evaluated using molecular genetic techniques, are found to encompass cryptic species diversity and high levels of population genetic structure on geographic scales more compatible with hypotheses of limited dispersal ability (Sole-Cava and Thorpe, 1986;BouryEsnault et al, 1992;Sole-Cava et al, 1992;Klautau et al, 1994Muricy et al, 1996;Wörheide et al, 2003). In fact, morphologically cryptic species are hypothesized to be more prevalent among sponges than other taxa due to the simplicity and plasticity of their morphological characters .…”

Taxonomic revision of the genusLatrunculiaDu Bocage (Porifera: Demospongiae: Latrunculiidae) in New Zealand

“…Other sponge genera, such as Corticium, Oscarella Hooper et al 1990), Cliona (Barbieri et al 1995), and Plakina (Muricy et al 1996b) contain cryptic species that have been detected with genetic techniques and as in Latrunculia, are morphologically homogenous. In some of these cases (e.g., BouryEsnault et al 1992;Muricy et al 1996a) however, the species can be discriminated by cytological characters further highlighting the significance of morphological studies in resolving the taxonomy of sponge species.…”