The thermotropic behavior and major molecular species composition of the phospholipids of echinoderms

This study examines the molecular species composition and heat-induced crystalline-liquid crystalline phase transitions of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) from the muscle tissues of six species of echinoderms that were collected during the summer: the starfishes Distolasterias nipon and Asterias amurensis, the sea urchin Strongylocentrotus intermedius, and the holothurians Eupentacta fraudatrix, Cucumaria frondosa japonica, and Apostichopus japonicus. Phospholipids (PLs) were in the liquid crystalline state, which is optimal for the functioning of the cell membranes. The use of data on the molecular species composition of PLs for the interpretation of their thermotropic behavior indicated that homeoviscous adaptation is achieved by various rearrangements in the composition of the aliphatic groups of PLs. The phase transitions of PC and PE of echinoderms (except holothurians) were symbatic. The presence of a high-temperature peak on the PC thermograms of C. frondosa japonica and A. japonicus is attributable to the melting of the phospholipid domain, which is composed of molecular species with saturated aliphatic groups. Such domains are responsible for a significant shift in the temperature ranges of the phase transitions of phospholipids of holothurians and sea urchin towards temperatures above 0°C.     

Inventory of echinoderms in the Iles Eparses (Europa,Glorieuses, Juan de Nova), Mozambique Channel,France

The multidisciplinary programme BioReCIE (Biodiversity, Resources and Conservation of coral reefs at Eparses Is.) inventoried multiple marine animal groups in order to provide information on the coral reef health of the Iles Eparses. All five classes of echinoderms were observed by visual census, photographed and later identified. About 100 species are reported, including a few unidentified ones which require further studies. The Holothuroidea and Ophiuroidea are the most diverse. One new species, the asterinid Aquilonastra chantalae O'Loughlin and McKenzie (2013), was discovered in addition to several new records of echinoderms. The illegal fishery targeting holothurians, which are presently highly valuable resources in this zone, is discussed.     

Species composition and distribution of echinoderms (Echinodermata) in the upper subtidal zone of Kola Bay,Barents Sea

The species composition and patterns of distribution of echinoderms from the upper sublittoral zone to depth of 30 m in the southern and middle of Kola Bay in the Barents Sea were studied. In total, five species of starfishes, four species of brittle stars, three species of sea urchins and one species of holothurians were recorded. From the beginning of 20th century, under the impact of climate change and anthropogenic effect, the number of echinoderm species in the surveyed area decreased by two times, and the fauna has a more boreal character against the background of the domination of boreal-arctic species. The occurrence, population density and biomass of echinoderms, especially of common species, were several times less in the middle bend of the bay than in the southern one. The causes of this phenomenon have been discussed. The quantitative data (frequency of occurrence, number and biomass) for most of the species of echinoderms living in Kola Bay are given for the first time.     

Is there a link between the type of habitat and the patterns of abundance of holothurians in shallow rocky reefs?

The presence of a mosaic of habitats, largely determined by sea urchin grazing, across shallow rocky reefs may potentially influence in differences in the distribution patterns of invertebrates. The aim of this paper was to assess, using a correlative approach, whether the type of habitat influences the abundance patterns of holothurians in the eastern Atlantic. We hypothesized that abundances of large (> 10 cm) holothurians varied among four types of habitat (3 vegetated habitats with low abundances of the sea urchin D. antillarum vs. ‘barrens’ with hyperabundances of sea urchins), and that these differences were consistent at a hierarchy of spatial scales, including two islands and several replicated sites within each type of habitat and island. Three species of large holothurians were found, accounting for a total of 300 specimens. We found remarkable differences in abundances of holothurians between the ‘barrens’ and the three vegetated habitats. This pattern was strongest for the numerically dominant species, Holothuria sanctorii. Total abundances of holothurians were between 5 and 46 times more abundant in ‘barrens’ compared with the vegetated habitats. Inter-habitat differences were species-specific with some inconsistent patterns from one island to the other. The total abundances of holothurians tended to increase with the abundance of sea urchins within ‘barrens’. Our study suggests that there may be a link, at least for the dominant species Holothuria sanctorii, between the distribution and abundances of large holothurians and the habitat across shallow-waters of the eastern Atlantic.     

Symbiotic Bacteria on the Epidermis of Species of the Nemertodermatida (Platyhelminthes,Acoelomorpha)

Meara stichopi and an undescribed species of Meara, both endosymbiotic in the intestine of aspidochirote holothurians, possess filiform extraepidermal bacteria among the epidermal cilia. Similar bacteria were also observed on one specimen of the free-living species Nemertoderma westbladi. The bacteria are of the gram-negative type, as evident by cell wall structure and results from gramstaining. On a few specimens of M. stichopi, the bacteria were found to carry peculiar distal appendages, or buds, on stalked cup-shaped cell extensions. As the bacteria described here appear to be species specific, they can be used in addition to other features in the often problematic characterization of the nemertodermatid species.     

Sea Cucumbers Triterpene Glycosides, the Recent Progress in Structural Elucidation and Chemotaxonomy

Triterpene glycosides are characteristic metabolites of sea cucumbers (Holothurioidea, Echinodermata). Majority of the glycosides belong to holostane type (lanostane derivatives with 18(20)-lactone). Carbohydrate chains of these glycosides contain xylose, glucose, quinovose, 3-O-methylglucose and 3-O-methyl sylose. During the last 5 years, main investigations were focused on holothurians belonging to the order Dendrochirotida collected in the North Pacific, North Atlantic, Antarctic and in subtropical waters. The glycosides of holothurians belonging to the order Aspidochirotida have also been studied. The most uncommon structural features of carbohydrate chains of new glycosides were: (1) the presence of quinovose as fifth terminal monosaccharide unit and the presence of two quinovose residues; (2) the presence of glucose instead of common xylose as fifth terminal monosaccharide unit; (3) trisaccharide carbohydrate chain; (4) the presence of two 3-O-methylxylose terminal monosaccharide units; (5) the presence of sulfate group at C-3 of quinovose residue. New glycosides without lactone or with 18(16)-lactone and having shortened side chains have also been isolated. The presence of 17α and 12α-hydroxyls, which are characteristic for glycosides from holothurians belonging to the family Holothuriidae (Aspidochirotida) in glycosides of dendrochirotids confirms parallel and relatively independent character of evolution of glycosides. All three families belonging to the order Aspidochirotida: Holothuriidae, Stichopodidae and Synallactidae have similar and parallel trends in evolution of the glycosides carbohydrate chains, namely from non-sulfated hexaosides to sulfated tetraosides. Sets of aglycones in glycosides from holothurians belonging to the genus Cucumaria (Cucumariidae, Dendrochirotida) are specific for each species. The carbohydrate chains are similar in all representatives of the genus Cucumaria.     

Activities of digestive enzymes of polar and subtropical echinoderms

Activities and characteristics of digestive enzymes of polar and subtropical echinoderms are similar. Specific adaptations to facilitate digestion at low temperature were not observed. Levels of chymotrypsin and β-glucosidase of digestive tissues of the Antarctic asteroids Odontaster validus and Odontaster meridionalis, and the Antarctic echinoid Sterechinus neumayeri, are comparable to levels of the asteroids Henricia downii and Astropecten articulatus from the Gulf of Mexico. α-Glucosidase activities are similar for S. neumayeri and A. articulatus. The pH of maximal activity is 7.5 for disaccharidases and 8.5–9.5 for chymotrypsin for both polar and subtropical species. Affinities for substrates were higher at 25°C than at 0°C for disaccharidases of all species. However, K_m values for chymotrypsin increased from 0 to 25°C. Lack of sufficient adaptation by polar echinoderms to facilitate digestion at low temperature may reduce their capacity to digest food. Received: 24 July 1996 / Accepted: 31 January 1997     

Ultrastructure of coelomic lining in echinoderm podia: significance for concepts in the evolution of muscle and peritoneal cells

Summary Ultrastructural data are presented on the histological organization of coelomic lining in the podia of ten species of the five major groups of extant echinoderms. Further evidence of the incorporation of podial retractor muscle cells (myocytes) into a monociliated myoepithelial coelomic lining is provided. In the podia of the crinoid Nemaster rubinginosa and the ophiuroid Ophiophragmus wurdemani as well as in the feeding tentacles of the holothurian Leptosynapta tenuis, coelomic linings are organized as simple myoepithelia consisting of non-contractile peritoneal cells (peritoneocytes) and myocytes. Coelomic linings in the holothurian Thyonella gemmata, the echinoids Eucidaris cf. tribuloides and Lytechinus variegatus, and the asteroids Asterias forbesi and Astropecten sp. are pseudostratified or bipartite pseudostratified myoepithelia consisting of subapical myocytes and apically situated peritoneocytes. The ophiuroid podia of Ophioderma brevispinum and Ophiothrix angulata exhibit transitions from simple myoepithelia to partially pseudostratified epithelia. Intermediate forms between the extremes in myoepithelial organization also occur in the podial lining of single species (e.g. Eucidaris cf. tribuloides). These data supplement recent ultrastructural studies on the podial lining of echinoderms and, in conjunction with published ultrastructural data on the myoepithelial organization of other coelomic linings in echinoderms and in other coelomates, suggest myoepithelial organization of the coelomic lining is a plesiomorph feature in Bilateria.     

Echinoderms from Marino Ballena National Park, Pacific, Costa Rica

A total of 25 species of echinoderms (four asteroids, six ophiuroids, five echinoids and ten holothurians) were recorded at Marino Ballena National Park, using 25 m2 quadrants, parallel to the coast, at seven sites. The ophiuroids were the most abundant group with 581 individuals and the asteroids the less abundant (48 individuals). Echinoderms densities were low, with the exception of the ophiuroids. Diversity, density and the number of groups were higher where sedimentation was lower. We suggest that sedimentation is having a negative effect on the diversity of echinoderms and on the development of the coral reefs in this park.     

The Evolution and Diversity of SALMFamide Neuropeptides

The SALMFamides are a family of neuropeptides that act as muscle relaxants in echinoderms. Two types of SALMFamides have been identified: L-type (e.g. the starfish neuropeptides S1 and S2) with the C-terminal motif LxFamide (x is variable) and F-type with the C-terminal motif FxFamide. In the sea urchin Strongylocentrotus purpuratus (class Echinoidea) there are two SALMFamide genes, one encoding L-type SALMFamides and a second encoding F-type SALMFamides, but hitherto it was not known if this applies to other echinoderms. Here we report the identification of SALMFamide genes in the sea cucumber Apostichopus japonicus (class Holothuroidea) and the starfish Patiria miniata (class Asteroidea). In both species there are two SALMFamide genes: one gene encoding L-type SALMFamides (e.g. S1 in P. miniata) and a second gene encoding F-type SALMFamides plus one or more L-type SALMFamides (e.g. S2-like peptide in P. miniata). Thus, the ancestry of the two SALMFamide gene types traces back to the common ancestor of echinoids, holothurians and asteroids, although it is not clear if the occurrence of L-type peptides in F-type SALMFamide precursors is an ancestral or derived character. The gene sequences also reveal a remarkable diversity of SALMFamide neuropeptides. Originally just two peptides (S1 and S2) were isolated from starfish but now we find that in P. miniata, for example, there are sixteen putative SALMFamide neuropeptides. Thus, the SALMFamides would be a good model system for experimental analysis of the physiological significance of neuropeptide “cocktails” derived from the same precursor protein.     

On the sites of secondary podia formation in a juvenile echinoid: growth of the body types in echinoderms

The growth of the adult echinoderm body is addressed here in the echinoid Holopneustes purpurescens in a study of the early development of the secondary podia along the five radial canals of the adult rudiment. At a stage when the first four secondary podia have formed along each radius oral to the primary podium, two podia are on one side of the radius and two are on the other side, all at a different distance from the primary podium. The pattern of the connexions of these secondary podia to the radial canals changes in successive radii in a manner similar to Lovén’s law for skeletal plates and matches the reported sequence in the times at which the first ambulacral skeletal plates form in the adult echinoid rudiment. A similar pattern is described for the reported origins of the secondary podia in apodid holothurians. A common plan for the growth of the body types is described for echinoids, asteroids, holothurians and concentricycloids. The five metameric series of secondary podia formed in echinoderms have a coelomic developmental origin like the single metameric series of somites formed in the axial structures of chordates.     

Toxicity of shallow-water Antarctic echinoderms

Summary The toxicity of 23 species of shallow-water antarctic echinoderms from McMurdo Sound was investigated using Gambusia affinis (Vertebrata: Pisces) as a test organism. Ichthyotoxicity assays were conducted on the body wall tissues of thirteen species of asteroids and three species of holothuroids, the tests of three species of echinoids and the arms of three species of ophiuroids and one species of crinoid. Patterns of toxicity were class-specific, with varying degrees of toxicity occurring exclusively among the Asteroidea and Holothuroidea. Seven of the thirteen species of asteroids were mildly to highly toxic (54%), while one of the three holothuroids was mildly and one highly toxic. Toxicity was not related to the level of calcification of the body wall and energy level in asteroids. The only armored asteroid, Notasterias armata, was non-toxic. The occurrence of toxins in the body tissues of antarctic echinoderms is similar in pattern and frequency with that of temperate and tropical species.     

Predictable and unpredictable spawning events: in situ behavioural data from free-spawning coral reef invertebrates

Summary

We describe the spawning behaviour and some aspects of spawning periodicity in a diverse group of marine invertebrates, principally echinoderms, but including sponges, anthozoans, molluscs, and polychaetes. Our observations were made both opportunistically and on a systematic basis between 1978 and 1992 on the central and northern Great Barrier Reef. Spawning was predictable in some of the species observed, for example Bohadschia argus, Euapta godeffroyi, and Stichopus variegatus (Holothuroidea), which exhibited regular lunar and diel periodicity. Others, such as Holothuria coluber, Actinopyga lecanora, and Bohadschia graffei (Holothuroidea), Acanthaster planei (Asteroidea), Hyotissa hyotis and Arca spp. (Bivalvia) exhibited no clear lunar or diel periodicity in spawning behaviour. Mass heterospecific spawnings which involved several species, often from different phyla, were commonly observed. The species participating were usually those with unpredictable spawning patterns and while the species involved were diverse there were also occasions when spawning involved species from the same genera. Fertilization rates were measured in situ for the predictable spawner Bohadschia argus and were found to vary between 0–96% depending on the circumstances of the spawnings. Fertilization rates for the unpredictable spawners showed similar variability; Holothuria coluber and Actinopyga lecanora ranged from 9–83%.     

Move,burrow, feed – repeat! A compound trace fossil from the Solnhofen Plattenkalke possibly made by holothurians

Abstract

Bromlichnus bromleyi n.igen. n.isp., a compound trace fossil consisting of two segments representing dwelling and feeding, is described. Owing to a concentric spreite in a bow-shaped burrow, B. bromleyi is interpreted as made by holothurians. In most cases, it is connected to a repichnion. The new ichnotaxon derives from the narrow Pfalzpaint Subbasin of the Solnhofen archipelago (Upper Jurassic, SE Germany), interpreted as a tidal channel connecting two basins. The interrelationships of different behaviours reflected in compound trace fossils allow holistic analysis of the work of individual animals, enabling more accurate interpretation of tracemaker anatomy and function.     

Diversity and abundance of echinoderms from the reef lagoon at Cahuita National Park, Caribbean from Costa Rica

A total of 15 species of echinoderms (one asteroid, seven ophiuroids, five echinoids and two holothurians) were recorded at the Cahuita National Park reef lagoon, between September and October 2003, using a 1 m2 quadrant. The sites with coral substrate and algae were the most diverse, while those with seagrass and sand were the least. Ophiuroids were the most abundant group with 170 individuals, asteroids were the least abundant. Adding other studies and reports of echinoderms to this study, a total of 23 species have been found at Cahuita National Park, which is the most diverse area on the Caribbean of Costa Rica. We report nine new echinoderm records for Costa Rica's Caribbean.     

Simultaneous Spawning of Six Species of Echinoderms in Barkley Sound,British Columbia

Summary

Six species of echinoderms were observed spawning (1 holothuroid, 1 echinoid, 4 asteroids) during a single 40 min dive to 10 to 18 m depth in Barkley Sound, Vancouver Island, on the afternoon of 9 August 1987, the day after the full moon. Most of the spawning animals were not close to conspecific individuals. None were observed spawning the following day. Published reports indicate that it is not uncommon for widely scattered individuals of echinoderms to broadcast spawn in the field. Fertilization success often may be low. Moreover, simultaneous spawning by different species, as we and others have observed, indicates that the incidence of hybridization (either lethal or viable) could be high and have important consequences to the biology of the species involved.