Digestive mechanics and gluttonous feeding in the feather starOligometra serripinna (Echinodermata: Crinoidea)

The movement and digestion of food in the gut ofOligometra serripinna (Carpenter) were studied at Lizard Island (14°3842S; 145°2710E) in the austral winter of 1986. Feather stars in the laboratory were fed a brief, small meal of brine shrimp nauplii and killed at increasing time intervals thereafter. Histological reconstructions showed that the ingested nauplii progressed along the digestive tract surprisingly quickly. Some nauplii were found in the mid and hind intestine in only 30 min, and all of the nauplii had reached the hind intestine and rectum in 1 h. Digestion of the nauplii had started at 1 h, and only a few fragments of naupliar exoskeleton remained in the hind intestine and rectum 5 h after the start of feeding. Videotape analysis showed that no fecal pellets were released during this experiment. In the natural environment ofO. serripinna, ingested particles may similarly be transported quickly to the hind part of the gut and digested there — when feather stars were fixed in the field, most of the gut contents were found in the hind intestine and rectum.O. serripinna, which efficiently rejects inert particles before they are ingested, usually defecates infrequently (probably not more than once over a span of many hours) and differs from some other feather stars that ingest numerous inert particles and defecate much more frequently. When specimens ofO. serripinna were fed continuously on brine shrimp nauplii,Artemia sp. (San Francisco strain), in the laboratory, the feather stars fed gluttonously, packing their guts with several hundred nauplii in 1 to 2 h. Thereafter, superfluous feeding began (i.e., further ingestions appeared to force undigested nauplii, some of them still living, out of the anus). These observations suggest thatO. serripinna usually feeds at relatively modest rates in its natural habitat, but can feed gluttonously to take advantage of infrequent patches of highly concentrated, nutritious particles (e.g. copepod swarms, migrating demersal zooplankton, and invertebrate gametes from mass spawnings). It is likely that such patches of nutritious particles are usually small enough to drift out of reach of the feather stars before gluttonous feeding proceeds to superfluous feeding. Opportunities for superfluous feeding in nature are probably very infrequent (e.g. ingestion of coral gametes and embryos after a mass spawning), and the feather stars evidently have no behavior that stops further ingestions after the gut becomes filled to capacity.     

Effects of current speed on filtration during suspension feeding in Oligometra serripinna (Echinodermata: Crinoidea)

Suspension feeding by the crinod Oligometra serripinna was studied at Lizard Island, Australia, in 1986. Video recordings were made of 90-m particles interacting with the filter of the crinoid in a laboratory flow chamber. A complete census of particles was possible because both the capture event and the filter area could be defined unequivocally. Also, because O. serripinna is a passive suspension feeder, a census of partcles could be made at different ambient current speeds without interference due to active pumping by the crinoid. Experiments were run at seven current speeds from 0.9 to 13.3 cm s^-1. Particles approaching the filter: (1) were captured, (2) passed through the filter without triggering a capture event, (3) passed through the filter after escaping from an unsuccessful capture event, or (4) were deflected around the filter. With increasing current speed, the proportion of deflections declined and the proportion of particles passing through rose: these results could be partially explained by the progressive widening of the spaces within the filter due to distortion of filter parts by the current. The proportion of captures (normalized to approaches) was comparatively low at 0.9 cm s^-1, rose to a relatively constant maximum from 1.7 to 6.4 cm s^-1, and then declined progressively at 9.5 and 13.3 cm s^-1. These proportions were translated into capture rates for whole crinoids by taking into consideration both the encounters with particles and the reduction of filter area by distortion of body parts at higher speeds. When plotted against current speed, capture rate peaked at 6.4 cm s^-1, which was close to the mean current speed that we measured on the reef in the microhabitat of O. serripinna.     

Reproductive biology and early life history of the hermaphroditic feather star Dorometra sesokonis (Echinodermata: Crinoidea)

Reproduction and larval/post-larval development of the one of the smallest known comatulid Dorometra sesokonis were studied on the coral reefs of Sesoko-jima Island, Okinawa, Japan. Breeding individuals were found every month from May 2003 to April 2004 indicating continuous reproduction. Individuals possessed both mature ovaries and testes, and were therefore characterized as simultaneous hermaphrodites. This species was observed to be an external brooder in which the embryos developed on the surface of parental genital pinnules until the doliolaria larval stage, and subsequently released doliolariae settled on substrata within 4 days after hatching. Larvae then metamorphosed into the post-larval cystidean stage, which lasted for more than a month. The reproductive features of this species are unique among crinoids, and, together with juvenile morphological features observed in adults, can be interpreted as adaptations to their cryptic habitat, which is subject to frequent natural disturbances.     

Time-lapse cinematography of feather stars (Echinodermata: Crinoidea) on the Great Barrier Reef,Australia: demonstrations of posture changes,locomotion, spawning and possible predation by fish

Aspects of feather star behavior and ecology were recorded by time-lapse cinematography approximately 1 frame min^-1 on the Great Barrier Reef, Australia over a 1 mo period in 1983. The current regime influenced body postures of most species studied, whether nocturnal or not. Moreover, feather stars of several species crawled on the substratum with their arms; each crawling episode lasted roughly 10 min, and the maximum speed attained was about 1 arm length min^-1. Nocturnal feather stars crawled to their nighttime feeding perches around dusk and crawled back to their daytime hiding places around dawn. Surprisingly, some species of feather stars living on the reef surface both day and night also crawled around at dawn and dusk for reasons that are not known. In the time-lapse films, and individual of Comanthus bennetti (sex undetermined) spawned for about 2 min just after dark on 5 July 1983. Another film showed possible predation on a feather star (Himerometra robustipinna) by a saddled coralfish (Chaetodon ephippium).     

Observations on the food of Antedon bifida (Echinodermata: Crinoidea)

The gut contents of specimens of the temperate crinoid Antedon bifida (Pennant) were collected from Dalkey, County Dublin, at monthly intervals for 1 yr, and occasionally from other areas around the Irish coast. Quantitative analysis showed the main components to be detritus (65%), plankton (18%) and inorganic particles (17%). This composition was remarkably constant throughout the year and at all locations, the main variation being in the plankton which was at a minimum in February (4%) and reached a maximum in August (36%). Food particle collection appeared to be nonselective within the appropriate size group, the essential feature of a particle being that it would fit into the ambulacral groove. Fragile planktonic diatoms and dinoflagellates, which occurred in blooms in summer and autumn, were digested by A. bifida, but more robust diatoms passed intact through the gut. Histochemical investigations indicate that the bulk of the detritus is refractory, and it is suggested that its associated micro-flora and micro-fauna may be a major source of nutriment for this crinoid.     

Reproductive biology of the common antarctic crinoid Promachocrinus kerguelensis (Echinodermata: Crinoidea)

Histological examinations of the gonads of Promachocrinus kerguelensis Carpenter, 1888 collected in November 1984 from McMurdo Sound, Antarctica, revealed ripe ovaries containing three distinct size classes of oocytes: 20 to 90, 91 to 150 and 151 to 180 m diameter as well as ova. Testes were ripe, and filled with mature sperms. There was marked inter-pinnule and inter-individual synchrony of gametogenesis and spawning is probably synchronous, at least within the sub-population sampled. The number of eggs per pinnule is allometrically related to body size. Body weight and arm length are positively correlated with total egg number. Annual fecundity was estimated to be 29 000 eggs (full-grown oocytes and ova) for a crinoid weighing 53.6 g wet weight with an arm length of 16.3 cm. The eggs float. Female genital pinnules contain more lipid and energy than male pinnules. Reproductive output and effort (23.4 to 65.2 kJ and 26 to 38%, respectively) increase with body size and are similar to values reported for other echinoderms with lecithotrophic larvae. The greatest overall energetic contribution is represented by the arms and genital pinnules. Spawning in P. kerguelensis probably occurs in November and December within McMurdo Sound. If development is slow, as in all other antarctic echinoderms studied to date, then settlement most likely occurs 2 to 3 mo later, after the short summer period of high phytoplankton productivity. High fecundity, a pelagic mode of reproduction, and the high probability of a slow rate of development may contribute to the wide geographic distribution of this common antarctic crinoid.     

The early embryology of the basket star Gorgonocephalus caryi (Echinodermata,Ophiuroidea)

The changes in morphology of Gorgonocephalus caryi embryos over the 8 1/2 day period of their survival are described. Fertilized eggs are 220 in diameter. Division is equal and holoblastic, and the blastula stage is reached within 24 h. Gastrulation begins at about 40 h. At 68 h, the anterior end of the embryo begins to elongate. The embryos are pear-shaped at 72 h. At about 84 h the anterior end begins to bend towards one side. By 98 h the entire embryo has flattened perpendicular to the anterior-posterior axis, and the embryo is a flattened, trilobed structure. At 4 1/2 days the anterior tip twists around to lie with its axis in a plane perpendicular to the other 2 lobes. They, meanwhile, shift in position so that the resulting embryo resembles an umbrella which is flat on top and has a curved handle. Meanwhile, the hydrocoel forms as an out-pouching from the archenteron in the anterior lobe. The general coelom develops by schizocoely. Between 5 and 5 1/2 days, the anterior lobe coelesces with the flattened area as it becomes pentagonal. By 5 1/2 days, many embryos are starshaped. At 6 1/2 days the mouth begins to form. By 8 days the embryos were dying, and none lived beyond 10 1/2 days. At no time did cilia or other locomotory structures develop. The development of G. caryi does not resemble that of any other ophiuroid studied. There is not trace of a pluteus, and it is postulated that the pluteus evolved after the Phrynophiurida and the Ophiurida were differentiated.     

Reproduction and population dynamics of the fissiparous brittle star Ophiactis savignyi (Echinodermata: Ophiuroidea)

Reproductive cycle, asexual reproduction, and population dynamics of the fissiparous brittle star, Ophiactis savignyi, which inhabits the exhalant passages of the sponge Haliclona sp. were examined monthly from February 1991 to January 1992 at Wanlitung, southern Taiwan (22°N; 120°E). Mature gametes were found from March to December, but release was mainly in May and June. Sexual recruits were found from May to December, with the highest frequency (14.1% of population) in June. Sexual recruits composed 2.4% of the 1-yr sample. Sex ratio of male to female was 24:1. Fission occurred throughout the year, although the frequency of recently split individuals was lower from January to June (6 to 31%), and higher from July to December (42 to 52%). The occurrence of fission was highest after spawning. Regenerating individuals composed 48.2% of the 1-yr sample. Population density fluctuated greatly during summer due to recruitment by fission and mortality or dispersal due to the stressful environmental conditions. Both sexual and asexual reproduction of O. savignyi were successful at this site.     

Costs of extended brood protection in the Antarctic sea star, Neosmilaster georgianus (Echinodermata: Asteroidea)

Changes in size, morphology, and biochemical composition in adults and embryos of a brooding sea star, Neosmilaster georgianus (Sladen), were studied in a population adjacent to Anvers Island, Antarctic Peninsula (64°46′S; 64°04′W) during the austral spring, 1991. Five morphological stages of development were designated in 24 broods, and for each the weight and biochemical composition of the brooding adults and their embryos were determined. Between Stage 1 and 2, the dry weight (dw) and organic weight (ow) of the embryo did not change. From Stage 2 to 3, the dw and ow increased significantly by 10%. Stage 2 and 3 embryos were in clusters of a few (2 to 10) to as many as 40 individuals. In the smaller clusters, individual embryos were attached by tissue cords to another, sometimes atrophied, brood member. In the larger clusters, they were attached to a central mass of tissue containing remnants of embryos. We interpret these interactions as a form of cannibalism which may account for the weight gains between Stage 2 and 3. During Stages 4 and 5, as juvenile form was approached, the dw and ash weight of the young increased significantly and the ow decreased significantly. The calculated energy content for the juvenile (Stage 5) was not significantly different from the energy content of the earliest undifferentiated stage (Stage 1), an indication that most of the organic matter in the egg is the primary contribution to the large juvenile. In brooding females, pyloric caeca indices declined by 52% from Stage 1 to Stage 5 and pyloric energy stores declined by 63% due to proportionately equivalent declines in protein and lipid. The ovary index was low and increased only slightly during brood protection, while the size of the largest oocytes remained approximately 23% that of ova. Energy stores in the pyloric caeca of brooding N. georgianus thus become depleted over a long period of incubation during which the adults apparently starve. This may delay oocyte development and ultimately limit the frequency of individual reproduction. Received: 15 September 1998 / Accepted: 9 March 1999     

Food composition of crinoids (Crinoidea: Echinodermata) in relation to stalk length and fan density: their paleoecological implications

Crinoids have been diverse organisms in marine epifaunal filter feeding communities at any level of tiering above the substrate since they appeared in the Ordovician. Feeding is regarded as the most important factor in producing the crinoid tiering, which is primarily defined by stalk length. The gut contents of five sympatric crinoid species (three isocrines and two comatulids) were observed, and these were compared with the stalk length and the fan density. We have classified these crinoid species into four groups based on the stalk length and fan density, e.g., long stalk with low fan density, long stalk with high fan density, short stalk with low fan density, and short stalk with high fan density. In the gut contents, diatom crusts were found mainly from species with longer stalks, and chlorophyll-like fluorescent material were only detected from the groups with a shorter or no stalk. The group with lower fan density contained more inorganic particles than the group with higher fan density. Therefore, the gut contents and their amounts depend on their stalk lengths and their fan densities. The results imply that diversified morphologies in the crinoids have evolved through adaptations to different ecological factors such as difference in their diets.     

Development,settling behaviour,metamorphosis and pentacrinoid feeding and growth of the feather star Florometra serratissima

Embryonic development of the northeastern Pacific feather star Florometra serratissima takes place within a ridged fertilization membrane. Cleavage is radial, resulting in a coeloblastula, and gastrulations is by invagination. Cilia are swollen terminally during ciliogenesis whereas fully grown cilia possess several swellings along the length of their shafts. Young doliolaria larvae begin to hatch from the fertilization membranes 35 h after fertilization (9.5° to 11.5°C); by 4 d the doliolaria has acquired ciliated bands, a vestibular invagination and an antero-ventral adhesive pit. The surface of the larva is covered with a delicate glycocalyx supported by microvilli. Larvae swim along a vertical sinusoidal path just below the water surface; they begin to explore the substratum at 4.5 d and settlement begins as early as 4.6 d, but can be delayed for up to 9 more days. Larvae settle gregariously in culture and it is suggested that gregarious settlement plays a role in the formation and maintenance of adult aggregations of F. serratissima. Metamorphosis into a stalked cystidean following settlement is rapid. Major changes at this period include: loss of cilia; withdrawal of ectoderm from the glycocalyx; covering over of the vestibular invagination; and a 90 degree rotation of the vestibule to the former posterior end of the doliolaria. Transformation from cystidean to pentacrinoid includes the opening of the 5 oral plates, the extension of the 15 papillate tube feet and further elongation of the stalk. The pentacrinoid is able to feed on small food particles. Rudiments of all 10 adult arms are present by 4 months; at 6 months the pentacrinoid has an arm span of 6.5 mm but cirri and pinnules are not yet present.     

On the distribution and variability of the Indo-Pacific sea star Asterina wega (Echinodermata: Asteroidea) in the Mediterranean sea

The distribution of the Mediterranean populations of Asterina wega Perrier is described. Four populations were found to differ in size of animals and regeneration rate. The possible migratory pattern is duscussed.     

Phylogeography of the sea star Marthasterias glacialis (Asteroidea, Echinodermata): deep genetic divergence between mitochondrial lineages in the north-western mediterranean

We explore the phylogeography of the broadcast spawner Marthasterias glacialis along south Europe and Azores. Sequences of the cytochrome c oxidase gene from 225 specimens, belonging to 10 localities, were analysed. We found 73 haplotypes grouped within two lineages (divergence 2.9%). One lineage was Atlanto–Mediterranean, whereas another one was exclusively Mediterranean. Estimation of lineages split goes back to 830,000–580,000 (±120,000) years ago. This suggests that sea-level oscillations during the Pleistocene glaciations promoted gene flow interruption, lineage divergence between basins and cryptic speciation. Secondary contact between populations allowed a recolonization of the Mediterranean by the Atlantic lineage. When animals of the Atlanto–Mediterranean lineage were considered separately, F _st index and AMOVA did not show significant differences between populations along either the Iberian Peninsula or basins. Isolation by distance between populations was not detected, and only populations of Plymouth and Azores showed significant differences to all the others. The remoteness of Azores islands might explain the structure of this population. Haphazard arrival of larvae and local extinctions rather than contemporary restricted gene flow might be responsible for the distinctive population structure of Plymouth.     

Feeding behavior of the sea star Astropecten articulatus (Echinodermata: Asteroidea): an evaluation of energy-efficient foraging in a soft-bottom predator

The energy efficiency of the foraging behavior of Astropecten articulatus (Say) was evaluated in the laboratory. Individuals utilized in the study were collected in the northern Gulf of Mexico from 1990 to 1992. Sea stars presented with equal numbers and weights of low-quality and high-quality prey consistently selected prey of the higher quality. Choice of prey appeared to be mediated by contact chemoreception. Individuals presented with equal weights or equal numbers of different-sized prey models demonstrated a significant preference for smaller prey. Size-selective feeding may be attributable to the ease of manipulation and ingestion of smaller prey, which mazimizes food intake per unit time. In the absence of prey, A. articulatus exhibited a directional pattern of movement. However, as prey were encountered, both the frequency and magnitude of angular deviations in the foraging path increased, resulting in increased foraging in areas of higher prey density. This response to prey availability may increase foraging efficiency by maximizing the rate of prey encounter. Like four other species of the genus Astropecten, A. articulatus exhibited two peaks of activity corresponding with dawn and dusk. Diurnal activities with periods of increased prey availability or periods during which predators are diminished or absent. The sea star A. articulatus exhibits foraging behaviors consistent with the maximization of net energy intake per unit foraging time.     

The systematic position of some boring sponges (Demospongiae,Hadromerida) studied by molecular analysis

A phylogenetic analysis of some bioeroding sponges of the family Clionaidae (Order Hadromerida) was performed to resolve some taxonomic problems both at the specific and the supraspecific level using the D2 and D3 regions of 28S rDNA. Species belonging to the genera Cliona, Cliothosa, Spheciospongia (fam. Clionaidae) and Diplastrella (fam. Spirastrellidae) from the Mediterranean Sea and Celebes Sea (Indonesia) were analysed. In the phylogenetic tree, the species clustered on two main branches, one comprising Cliona celata, C. rhodensis, C. utricularis, and Cliothosa hancocki, and the other made up of C. viridis, C. nigricans, C. schmidti, C. jullieni, Spheciospongia solida and S. vagabunda. Above the species level, data do not support the separation of the genus Cliothosa from Cliona, while they do support the inclusion of some massive boring species, previously assigned to the genus Spirastrella, in the family Clionaidae. At the species level, data demonstrated the genetic identity of taxa C. viridis and C. nigricans, in spite of their considerable morphological differences. In contrast, the yellow species commonly attributed to C. celata are probably to be considered as a complex of sibling species with a number of distinct taxa present in the Mediterranean. Data also showed the identity of the Mediterranean and Pacific populations of C. schmidti, suggesting the status of a Tethyan relict for this species.     

Karyotype analysis of the sea urchinParacentrotus lividus (Echinodermata): evidence for a heteromorphic chromosome sex mechanism

A consistent diploid number of 2n = 36 was determined for the sea urchinParacentrotus lividus from the Gulf of Palermo by analysis of mitotic chromosomes of both early developing embryos and male gonads. The haploid numbern = 18 was determined by counts of spermatocyte bivalents at diakinesis. A heteromorphic chromosome sex mechanism of the XY type is likely present in this species. This is indicated by the occurrence of a chromosomal pair, pair No. 2, which is heteromorphic in both morphology and size in about 50% of the mitotic figures (metaphases and anaphases) of einbryos. In addition, heteromorphism of the same pair of chromosomes occurred during spermatogonial metaphases in the five male specimens investigated here. The detection of a low chromosome number (2n = 36) compared to other echinoids (2n = 42 to 44), a heteromorphic chromosome sex system and the involvement of three chromosome pairs in nucleolar organization (NORs) provide evidence of the specialization of theP. lividus karyotype.     

Population dynamics,reproduction and growth of the Indo-Pacific horned sea star, <Emphasis Type="Italic">Protoreaster nodosus</Emphasis> (Echinodermata; Asteroidea)

The horned sea star (Protoreaster nodosus) is relatively common in the Indo-Pacific region, but there is little information about its biology. This study of the population biology of P. nodosus was carried out in Davao Gulf, The Philippines (7°5′N, 125°45′E) between September 2006 and May 2008. Protoreaster nodosus was found in sand and seagrass dominated habitats at a mean density of 29 specimens per 100 m² and a mean biomass of 7.4 kg per 100 m², whereas a significantly lower density and biomass was found in coral and rock dominated habitats. Adult specimens (mean radius R = 10.0 cm) were found at depths of 0–37 m, whereas juveniles (R < 8 cm) were only found in shallow sandy habitats with abundant seagrass (water depth ≤2 m). Increased gonad weights were found from March to May (spawning period), which coincided with an increasing water temperature and a decreasing salinity. Density and biomass did not change significantly during reproduction, but sea stars avoided intertidal habitats. All specimens with R > 8 cm had well developed gonads and their sex ratio was 1:1. Protoreaster nodosus grew relatively slowly in an enclosure as described by the exponential function G = 7.433 e^{−0.257 × R} . Maturing specimens (R = 6–8 cm) were estimated to have an age of 2–3 years. Specimens with a radius of 10 cm (population mean) were calculated to have an age of 5–6 years, while the maximum age (R = 14 cm) was estimated as 17 years. Potential effects of ornamental collection on the sea star populations are discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Growth and production of Sterechinus neumayeri (Echinoidea: Echinodermata) in McMurdo Sound,Antarctica

Population dynamics of Sterechinus neumayeri were investigated at four sites in McMurdo Sound: Cape Evans, McMurdo Station, East Cape Armitage and New Harbor. The annual formation of natural growth bands in the jaws of the Aristotle's lantern was verified by a tagging-recapture experiment. Growth functions based on natural growth bands indicated differences among stations but showed S. neumayeri to be a slow growing species, reaching its maximum diameter of 70 mm at an age of about 40 yr. Annual production ranged between 2.4 (C. Evans) and 0.65 g ash free dry mass m^-2 (New Harbor) and was related to differences in food conditions. More than 95% of total production was invested in reproduction, and less than 5% was invested in somatic growth. Consumption estimates for S. neumayeri showed this species to play a significant role in the benthic trophic web of McMurdo Sound.     

Ontogenetic habitat shift,population growth,and burrowing behavior of the Indo-Pacific beach star, <Emphasis Type="Italic">Archaster typicus</Emphasis> (Echinodermata; Asteroidea)

Archaster typicus, a common sea star in Indo-Pacific regions, has been a target for the ornamental trade, even though little is known about its population biology. Spatial and temporal patterns of abundance and size structure of A. typicus were studied in the Davao Gulf, the Philippines (125°42.7′E, 7°0.6′N), from February 2008 to December 2009. Specimens of A. typicus were associated with intertidal mangrove prop roots, seagrass meadows, sandy beaches, and shoals. Among prop roots, specimens were significantly smaller and had highest densities (131 ind. m⁻²) between November and March. High organic matter in sediment and a relatively low predation rate seemed to support juvenile life among mangroves. Size and density analyses provided evidence that individuals gradually move to seagrass, sandy habitats, and shoals as they age. Specimens were significantly larger at a shoal (maximum radius R = 81 mm). New recruits were found between August and November in both 2008 and 2009. Timing of recruitment and population size frequencies confirmed a seasonal reproductive cycle. Juveniles had relatively high growth rates (2–7 mm month⁻¹) and may reach an R of 20–25 mm after 1 year. Growth rates of larger specimens (R > 30 mm) were generally <2 mm month⁻¹. The activity pattern of A. typicus was related to the tidal phase and not to time of day: Specimens moved over the sediment surface during low tides and were burrowed during high tides possibly avoiding predation. This is one of the first studies to document an ontogenetic habitat shift for sea stars and provides new biological information as a basis for management of harvested A. typicus populations.