Cnidae variability in <i>Balanophyllia europaea</i> and <i>B. regia</i> (Scleractinia: Dendrophylliidae) in the NE Atlantic and Mediterranean Sea

Abstract

SUMMARY: Traditionally and for practical reasons, skeleton structure has been the main source of taxonomic characters for scleractinian systematics, whereas information from soft tissues has been comparatively neglected. However, skeleton variability may leave species identification uncertain. The use of characters from soft tissues (e.g. polyp anatomy, cnidae size) is routine in the study of other ("soft") hexacorallian orders. This contribution aims to determine whether cnidae characters are useful in taxonomic studies of scleractinians. The cnidae composition of two congeneric species-Balanophyllia europaea (Risso, 1826) and Balanophyllia regia Gosse, 1860-have been studied throughout a wide geographical area. The data obtained show consistent qualitative and quantitative differences between the two species. This study shows that the cnidae characters can be useful taxonomic criteria for distinguishing congeneric species.Key words: Scleractinia, Balanophyllia, cnidome, taxonomy, geographical variability. RESUMEN: VARIABILIDAD EN LOS CNIDOCISTOS DEBALANOPHYLLIA EUROPAEA Y B. REGIA (SCLERACTINIA: DENDROPHYLLIIDAE) EN EL ATLÁNTICO NORDESTE Y MEDITERRÁNEO. -Tradicionalmente, y por razones prácticas, la estructura del esqueleto ha sido la fuente principal de caracteres en la sistemática de escleractinias, mientras que la obtención de información a partir de los tejidos esta prácticamente desatendida. Sin embargo, la variabilidad del esqueleto puede resultar en identificaciones dudosas. El uso de caracteres a partir de la parte orgánica (e.g. anatomía del pólipo, dimensiones de los cnidocistos) es rutinario en el estudio de otros ordenes de hexacoralarios (blandos). La presente contribución tiene como objetivo evaluar la utilidad en estudios taxonómicos en escleractinias de los caracteres a partir de los cnidocistos. Se estudia la composición de cnidoscistos de dos especies cogenéricas -Balanophyllia europaea (Risso, 1826) y Balanophyllia regia Gosse, 1860-en una amplia área geográfica. Los datos obtenidos muestran consistentes diferencias cualitativas y cuantitativas entre las dos especies. Este estudio muestra que los caracteres a partir del estudio de los cnidocistos pueden ser criterios taxonómi-cos útiles para distinguir especies cogenéricas.

A phylogeny reconstruction of the Dendrophylliidae (Cnidaria, Scleractinia) based on molecular and micromorphological criteria, and its ecological implications

“…). Morphological variation among nematocysts type is less susceptible to changes caused by biotic and abiotic factors than skeletal features (Pires & Pitombo ; Terròn‐Sigler & Lòpez‐Gozàles ), and thus, they might be useful for reconstructing evolutionary relationships. However, the evaluation of these structures as potentially informative characters has so far been limited to a restricted number of taxa, and its usefulness for resolving phylogenetic relationships between genera remains to be explored.…”

The zooxanthellate scleractinian coral Oulastrea crispata (Lamarck, 1816), an overlooked newcomer in the Mediterranean Sea?

“…The importance of cnidae in taxonomic studies on scleractinians has been noted by Pires (1997). Later, several studies supported the relevance of observing cnidae, as well as other useful characters for identifying scleractinians (see Terrón-Sigler & López-González, 2005;Ocaña & Brito, 2013).…”

Histological data in a combined phylogenetic analysis of scleractinian reef corals

“…A cylindrical cell may appear as an oval when cut longitudinal, or tapering when cut obliquely. Therefore, characters such as cnidocyte size used in Terron‐Sigler and Lopez‐Gonzalez () could not be used. An illustrated guide to identifying and coding all characters is provided in Figures (also Table C1 for matrix).…”

“…Unlike scleractinians, use of histomorphology in cnidarians such as sea anemones (Rodriguez et al, ), staurozoans (Miranda et al, ), and zoanthids (Ryland et al, ), is standard practice in taxonomy. Previous analyses focusing on cnidocyte structures and distribution have been performed in hydrozoans (Garcia‐Arredondo et al, ) and actiniarians (Reft and Daly, ), but few have been done on scleractinians (but see Terron‐Sigler and Lopez‐Gonzalez, ; Fautin, ; Martinez‐Baraldes et al, ). Furthermore, descriptions of cnidarian tissue layers in groups such as octocorals (Menzel et al, ) and sea anemones (Reitzel et al, ), have been performed, but these have focused on pathology rather than taxonomy.…”