Skeletal morphology of two controversial Poecilosclerid genera (Porifera, Demospongiae):Discorhabdella andCrambe

Abstract

The genera Discorhabdella and Crambe are characterized by bearing uncommon spicule types, i.e. pseudoastrose acanthostyles and sphaeroclones, respectively. They have traditionally been considered to be unrelated taxa, but the present reexamination made evident that an important amount of skeletal features are shared by both. Some of these morphological features, such as the ornamentation on the point of the ectosomal subtylostyles, are reported for the first time. The study also revealed that a tuberose nature of the tyles of the main choanosomal megascleres could be a common ancestral condition in both genera. The morphology of the multi-toothed anchorate chelae showed a gradual transition across the species, suggesting that the morphological diversity in chelae was generated in these genera through a "palmate-anchorate-arcuate" evolutionary sequence. However, the forward or backward direction of this sequence remained unclear from the available evidence. Important levels of skeletal variability were found to affect many of the skeletal characters, especially in the genus Crambe. In some cases, this variabihty transgressed the limits theoretically defining a species, making evident that the traditional procedure just based on comparison of the skeletons becomes unreliable when tackling the taxonomy of these genera. Most of the skeletal variability seemed to correspond to genetic polymorphisms, except in the case of C. acuata. In this taxon, the skeletal variability could be a result of the existence of a cryptic species, originated by a misconceived synonymy between C. acuata and C. chelastra.Besides the skeletal variability, the obscure taxonomic meaning of many skeletal features favored the existence of conflicting taxonomic proposals for the suprageneric location of these genera, depending on the author's criteria. This study made evident that any subsequent attempt of phylogenetic inference should be based on an unweighted analysis of the available skeletal information.

First record of the sponge generaCrambeandDiscorhabdellafor the eastern Pacific, with description of three new species

“…Taxonomic interpretation and discussion of the new species are based on either recent or previous re-examination of material belonging to all extant species of the genera Crambe, Discorhabdella and Vetulina Schmidt, 1879 (see Maldonado and Uriz, 1996). We re-examined material stored in the Natural History Museum of London (NHML), Muse um National d' Histoire Naturelle, Paris (MNHN ), Museo Civico de Storia Naturale, Genoa (MCSN ), Museum of Monaco (MM ), Station Marine d' Endoume, Marseille (SME ), Landesmuseum Johanneum Graz, Steiermarkische (LMJG ), and Centro de Estudios Avanzados de Blanes (CEAB), as follows: Vetulina stalactites Schmidt, 1879 (syntype in NHML); Crambe crambe (Schmidt, 1862) (slide from the holotypeÐ as Suberites crambeÐ in NHML, paralectotype of Suberites fruticosum and Suberites crambe in LMJG, plus diverse Mediterranean material from SME and CEAB colls.…”

“…These two genera, which are here reported for the ® rst time from the eastern Paci® c, are characterized by peculiar spicules whose signi® cance in the skeletal evolution of the order Poecilosclerida still remains the subject of intense debate (e.g. Le vi, 1960;Hajdu et al, 1994;Uriz and Maldonado, 1995;Maldonado and Uriz, 1996;Maldonado et al, 1999 ).…”

Silica deposition in Demosponges: spiculogenesis in Crambe crambe

“…In this study, we have examined spiculogenesis in the Demosponge Crambe crambe (Schmidt), a widespread Mediterranean littoral sponge (Uriz et al 1992), the skeleton of which varies with the geographical locality (Maldonado and Uriz 1996). This species was first described as having styles to subtylostyles as megascleres and asteroid desmas and unguiferous tree-teeth isochelae as microscleres (Thiele 1899).…”

Phenotypic plasticity in the Caribbean sponge <i>Callyspongia vaginalis</i> (Porifera: Haplosclerida)

“…These characteristics are often not diagnostic beyond the genus level and show high levels of intra-specific variability (e.g. Maldonado and Uriz, 1996;Erwin and Thacker, 2007a).…”