Myzostomes from Papua New Guinea, with related Indo-West Pacific distribution records and description of five new species

Eighteen species of myzostomes were found in association with crinoids collected in Papua New Guinea. Thirteen of the former are described by means of in vivo, light microscopical, and SEM-based observations. Five are new to science: Myzostoma cuniculus, M. laingense, M. nigromaculatum, and M. longitergum are ectocommensals; Contramyzostoma sphaera is a parasite living in a soft cyst induced upon its host. The eight previously described species, six of which are redescribed in detail, include Myzostoma ambiguum Graff, M. capitocutis Eeckhaut, VandenSpiegel and Grygier, M. fissum Graff, M. mortenseni (Jägersten), M. polycyclus Atkins, and M. stochoeides Atkins, as well as Hypomyzostoma crosslandi (Boulenger) and Notopharyngoides aruensis (Remscheid). Most are ectocommensals but the last is an intradigestive symbiont. New Indo-West Pacific distribution and host records for all eight are listed, based on surveys of museum collections, and their entire range are mapped. Hypomyzostoma Perrier, 1897 (type species Myzostoma folium Graff) is resurrected for one of the species-groups previously recognized within Myzostoma, and a lectotype is selected for H. crosslandi. Specimens from Singapore previously identified as M. elegans Graff are reassigned to M. capitocutis

Unique morphologies of <i>Encheliophis vermiops</i> (Carapidae) with revised diagnosis of the genus

Encheliophis vermiops was first briefly described in 1990 on the basis of three specimens. This study validates this species and provides previously unrecorded useful characters to realise the identification: (1) the forward orientation of the palatine teeth, (2) the enlarged teeth of the third basibranchial, (3) the particularly well-developed pharyngeal apparatus, (4) the unpigmented band along the base of anal fin and (5) the insertion of the primary sonic muscle on the parasphenoid. Moreover, the particular morphology of Encheliophis vermiops forces us to reconsider the diagnosis of the genus

How different sterols contribute to saponin tolerant plasma membranes in sea cucumbers

Sea cucumbers produce saponins as a chemical defense mechanism, however their cells can tolerate the cytotoxic nature of these chemicals. To elucidate the molecular mechanisms behind this tolerance a suite of complementary biophysical tools was used, firstly using liposomes for in vitro techniques then using in silico approaches for a molecular-level insight. The holothuroid saponin Frondoside A, caused significantly less permeabilization in liposomes containing a Δ7 holothuroid sterol than those containing cholesterol and resulted in endothermic interactions versus exothermic interactions with cholesterol containing liposomes. Lipid phases simulations revealed that Frondoside A has an agglomerating effect on cholesterol domains, however, induced small irregular Δ7 sterol clusters. Our results suggest that the structural peculiarities of holothuroid sterols provide sea cucumbers with a mechanism to mitigate the sterol-agglomerating effect of saponins, and therefore to protect their cells from the cytotoxicity of the saponins they produce

Identification and quantification of spinochromes in body compartments of <i>Echinometra mathaei</i>'s coloured types

Sea urchin pigmentation is mainly due to polyhydroxy-1,4-naphthoquinones called spinochromes. If their molecular structures are well known in test and spines of many species, their abundance and distribution in other body compartments remain unstudied. The aim of this study is to analyse the pigment composition in four body compartments (test/spines, digestive system, gonads and coelomic fluid) of four coloured types of the sea urchin Echinometra mathaei. Qualitative and quantitative measurements by mass spectrometry highlight the existence of 13 different pigments; among which are five isomers of known spinochromes as well as three potentially new ones. The composition comparison shows the largest spinochrome diversity in ‘test/spines’ body compartments. The spinochrome concentrations vary from 48 to 1279 mg kg−1 of dried body compartment. It is the highest in the digestive system, although it is also important in the organic fraction of the ‘test/spines’ body compartment. This observation may be explained by higher exposures of some body compartments to external environments and by the protective role fulfilled by spinochromes against microorganisms, ultraviolet radiation and reactive oxygen species. The ‘black’ type—the most common coloured type in coral reefs—has the highest concentration of spinochromes indicating their importance in Echinoids' fitness by acting as a protective agent