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Abstract. Oviparous animals store yolk proteins within the developing oocyte. These proteins are used in gametogenesis and as a nutritional source for embryogenesis. Vitellogenin and the major yolk protein are [...]

Abstract. Echinoderms have excellent healing and regeneration abilities, but little is known about how they deal with the related challenge of durable foreign bodies that become lodged within their bodies. [...]

Responses by marine species to ocean acidification (OA) have recently been shown to be modulated by external factors including temperature, food supply and salinity. However the role of a fundamental biological parameter relevant to all organisms, that of body size, in governing responses to multiple stressors has been almost entirely overlooked. Recent consensus suggests allometric scaling of metabolism with body size differs between species, the commonly cited 'universal' mass scaling exponent (b) of 3/4 representing an average of exponents that naturally vary. One model, the Metabolic-Level Boundaries hypothesis, provides a testable prediction: that b will decrease within species under increasing temperature. However, no previous studies have examined how metabolic scaling may be directly affected by OA. We acclimated a wide body-mass range of three common NE Atlantic echinoderms (the sea star Asterias rubens, the brittlestars Ophiothrix fragilis and Amphiura filiformis) to two levels of pC[O.sub.2] and three temperatures, and metabolic rates were determined using closed-chamber respirometry. The results show that contrary to some models these echinoderm species possess a notable degree of stability in metabolic scaling under different abiotic conditions; the mass scaling exponent (b) varied in value between species, but not within species under different conditions. Additionally, we found no effect of OA on metabolic rates in any species. These data suggest responses to abiotic stressors are not modulated by body size in these species, as reflected in the stability of the metabolic scaling relationship. Such equivalence in response across ontogenetic size ranges has important implications for the stability of ecological food webs., Introduction In the marine environment, the most serious anthropogenic stressors are a consequence of increasing atmospheric C[O.sub.2], which has two major impacts; increased retention of heat in the atmosphere, the [...]

Stiffness changes in response to mechanical and chemical stimulation were studied in muscle-free dermal samples from the body wall of the starfish Linckia laevigata. The ultrastructural study showed that the dermis was packed with collagen fibrils between which only a small number of cells were observed. Muscles were found only in the walls of coelomic extensions leading to papulae. Stress-strain tests were performed on isolated dermis containing no muscles. The tangent modulus was 27.5 MPa at 0.04% strain rate in the stress-strain tests. It was increased to 40.7 MPa by mechanical stimulation, which also increased the tensile strength and breaking-strain energy density. Dynamic mechanical tests showed that the increase in stiffness in response to mechanical stimulation was transient. Acetylcholine ([10.sup.-6] - [10.sup.-3] mol [l.sup.-1) and artificial seawater with an elevated potassium concentration (KASW) stiffened the dermis. Mechanical stimulation caused a 12% mass loss. KASW also caused mass loss, which was inhibited by anesthesia. These results clearly showed that the stiffness changes in the starfish dermis were based on a non-muscular mechanism that was similar to that of other echinoderm connective tissues with mechanical mutability., Introduction Starfish change their body stiffness. On one hand they stiffen the body when it is mechanically stimulated (Motokawa and Wainwright, 1991), which is very probably a defensive behavior. On [...]

Mass individual pairing or pseudo-copulation of the sea star Archaster angulatus was observed in November and December 2009, suggesting a late-spring/summer spawning period for this species on the west coast of Australia. Detailed measurements were made on the second of these occasions. Density of sea stars was 1.11 per m.sup.2 and 68.5% were in mating pairs. Copulating pairs were mostly male on female, occasionally male on male. There was no difference in size between males and females in mating pairs. No evidence was found to indicate mating and spawning is coincident with lunar or tidal cycles. Females outnumbered males by more than 20%, but the difference in sex ratio was not statistically significant. Analysis of the reproductive cycle revealed that gonad indices reached their peak in October and declined from then until January. Histological sections of gonads confirmed that sea stars are in peak reproductive condition in October and November and are fully spent by January. Males have a much lower (ca. 1/3rd) gonad index than females when each are in peak reproductive condition, the second lowest recorded for any sea star. Pyloric caecae indices showed little annual variation and monthly averages of just 3-4% are among the lowest ever recorded for an asteroid. It is suggested that these characteristics are associated with the copulatory behaviour of the deposit feeding A. angulatus, enabling the species to maintain a high level of fertilisation success while also minimising the allocation of energy to gonad development in habitats with low or variable food availability. However, it is still difficult to explain why a species which ensures a high level of fertilisation by pseudo-copulation also does this en masse and synchronously. One hypothesis is that competition for males and the benefits of having eggs fertilised by multiple males favours both synchrony and aggregation., Author(s): John K. Keesing [sup.1] , Fiona Graham [sup.1] , Tennille R. Irvine [sup.1] , Ryan Crossing [sup.1] Author Affiliations: (1) CSIRO Wealth from Oceans Flagship, Marine and Atmospheric Research, [...]

The rates and patterns of feeding and displacement of predators constitute two of the most important plastic behavioral responses that allow individuals to respond quickly to changes in abundance of their prey, predation risks and to rapid alterations in environmental conditions. In this study, we quantified seasonal and spatial variation in displacement (net changes in location in 12 or 24 h periods) and prey consumed of marked individuals of the keystone seastar Heliaster helianthus at six sites spanning 600 km along the coast of north-central Chile. We evaluated the hypotheses that: (1) at sites with low availability (cover) of the main prey, the mussel Perumytilus purpuratus, Heliaster displays larger displacements and consumes a greater proportion of other prey (e.g. mobile species) than at sites with high mussel cover, (2) daily displacements will be correlated with sea surface temperature (SST) and (3) increased wave action will reduce seastar daily displacement. Our results show that Heliaster displacement is higher at sites with lower availability of P. purpuratus; and at these sites, a larger proportion of Heliaster individuals are observed feeding, mostly on other prey (e.g. limpets), which could offset the higher costs associated with increased movement. In addition, wave forces affected the activity of Heliaster negatively. Contrary to our expectations, the daily displacements did not show any relationship with SST measured on the day or the previous days of the surveys, despite the fact that average displacement was generally higher in summer than in winter months. Future studies should examine Heliaster movement during single foraging excursions and determine whether these responses affect the growth and reproductive output of individuals. Such information is vital to understand how changes in prey abundance and environmental conditions alter the behavior and energy budget of this predator and its ability to control prey populations., Author(s): Mario Barahona [sup.1] , Sergio A. Navarrete [sup.1] Author Affiliations: (1) grid.7870.8, 0000000121570406, Estación Costera de Investigaciones Marinas, Las Cruces & Center for Advanced Studies in Ecology and Biodiversity [...]

Gonad-stimulating substance (GSS) of starfish is the only known invertebrate peptide hormone responsible for final gamete maturation, rendering it functionally analogous to the vertebrate luteinizing hormone (LH). Here, we purified GSS of starfish, Asterina pectinifera, from radial nerves and determined its amino acid sequence. The purified GSS was a heterodimer composed of 2 different peptides, A and B chains, with disulfide cross-linkages. Based on its cysteine motif, starfish GSS was classified as a member of the insulin/insulin-like growth factor (IGF)/relaxin superfamily. The cDNA of GSS encodes a preprohormone sequence with a C peptide between the A and B chains. Phylogenetic analyses revealed that starfish GSS was a relaxin-like peptide. Chemically synthesized GSS induced not only oocyte maturation and ovulation in isolated ovarian fragments, but also unique spawning behavior, followed by release of gametes shortly after the injection. Importantly, the action of the synthetic GSS on oocyte maturation and ovulation was mediated through the production of cAMP by isolated ovarian follicle cells, thereby producing the maturation-inducing hormone of this species, 1-methyladenine. In situ hybridization showed the transcription of GSS to occur in the periphery of radial nerves at the side of tube feet. Together, the structure, sequence, and mode of signal transduction strongly suggest that GSS is closely related to the vertebrate relaxin. gonadotropin | gonad-stimulating substance | insulin-like growth factor/relaxin superfamily | 1-methyladenine | in situ hybridization

Of the five echinoderm classes, only the modern sea urchins (euechinoids) generate a precociously specified embryonic micromere lineage that ingresses before gastrulation and then secretes the biomineral embryonic skeleton. The gene regulatory network (GRN) underlying the specification and differentiation of this lineage is now known. Many of the same differentiation genes as are used in the biomineralization of the embryo skeleton are also used to make the similar biomineral of the spines and test plates of the adult body. Here, we determine the components of the regulatory state upstream of these differentiation genes that are shared between embryonic and adult skeletogenesis. An abrupt 'break point' in the micromere GRN is thus revealed, on one side of which most of the regulatory genes are used in both, and on the other side of which the regulatory apparatus is entirely micromere specific. This reveals the specific linkages of the micromere GRN forged in the evolutionary process by which the skeletogenic gene batteries were caused to be activated in the embryonic micromere lineage. We also show, by comparison with adult skeletogenesis in the sea star, a distant echinoderm outgroup, that the regulatory apparatus responsible for driving the skeletogenic differentiation gene batteries is an ancient pleisiomorphic aspect of the echinoderm-specific regulatory heritage. embryonic and adult skeletogenesis | gene network evolution | sea urchin | sea star

The morphological characteristics and the population genetic structures of the fissiparous seastar Coscinasterias acutispina were investigated for eight sites in the Sea of Japan in order to clarify the presence of sexual and asexual reproduction. Morphological observation based on arm length showed that fission was common at all eight sites examined, indicating the likely production of clonal individuals. A random amplified polymorphic DNA (RAPD) marker was used to detect clones arising by fission and to assess gene flow among sites. A simulation approach using RAPD data revealed the presence of clonal individuals at almost all sites, suggesting the existence of asexual reproduction. The result of phylogenetic analysis according to RAPD genotype showed no relationship between genetic and geographic distances. Considering the limited movement ability of seastar species during the adult phase, these observations suggest the existence of marked gene flow among sites, due to dispersal of planktonic larvae produced by sexual reproduction. These observations suggest that multi-locus genotypic compositions depend on the relative amounts of recruitment from sexual and asexual reproduction in each population., Introduction Some animals, such as sessile and sedimentary marine invertebrates, have an asexual mode of reproduction as well as a sexual mode, although sexual reproduction predominates in most other animals [...]

Plasma membrane wound repair is an important but poorly understood process. We used femtosecond pulses from a Ti-Sapphire laser to make multiphoton excitation--induced disruptions of the plasma membrane while monitoring the membrane potential and resistance. We observed two types of wounds that depolarized the plasma membrane. At threshold light levels, the membrane potential and resistance returned to prewound values within seconds; these wounds were not easily observed by light microscopy and resealed in the absence of extracellular [Ca.sup.2+]. Higher light intensities create wounds that are easily visible by light microscopy and require extracellular [Ca.sup.2+] to reseal. Within a few seconds the membrane resistance is ~100-fold lower, while the membrane potential has depolarized from -80 to -30 mV and is now sensitive to the [Cl.sup.-] concentration but not to that of [Na.sup.+], [K.sup.+], or [H.sup.+]. We suggest that the chloride sensitivity of the membrane potential, after wound resealing, is due to the fusion of chloride-permeable intracellular membranes with the plasma membrane.

Peptides released from eggs of marine invertebrates play a central role in fertilization. About 80 different peptides from various phyla have been isolated, however, with one exception, their respective receptors on the sperm surface have not been unequivocally identified and the pertinent signaling pathways remain ill defined. Using rapid mixing techniques and novel membrane-permeable caged compounds of cyclic nucleotides, we show that the sperm-activating peptide asterosap evokes a fast and transient increase of the cGMP concentration in sperm of the starfish Asterias amurensis, followed by a transient cGMP-stimulated increase in the [Ca.sup.2+] concentration. In contrast, cAMP levels did not change significantly and the [Ca.sup.2+] response evoked by photolysis of caged cAMP was significantly smaller than that using caged cGMP. By cloning of cDNA and chemical crosslinking, we identified a receptor-type guanylyl cyclase in the sperm flagellum as the asterosap-binding protein. Sperm respond exquisitely sensitive to picomolar concentrations of asterosap, suggesting that the peptide serves a chemosensory function like resact, a peptide involved in chemotaxis of sperm of the sea urchin Arbacia punctulata. A unifying principle emerges that chemosensory transduction in sperm of marine invertebrates uses cGMP as the primary messenger, although there may be variations in the detail. Keywords: Caged compounds; Chemotaxis; Cyclic nucleotides; Kinetic measurements; Sperm

Breakdown of the nuclear envelope (NE) was analyzed in live starfish oocytes using a size series of fluorescently labeled dextrans, membrane dyes, and GFP-tagged proteins of the nuclear pore complex (NPC) and the nuclear lamina. Permeabilization of the nucleus occurred in two sequential phases. In phase I the NE became increasingly permeable for molecules up to ~40 nm in diameter, concurrent with a loss of peripheral nuclear pore components over a time course of 10 min. The NE remained intact on the ultrastructural level during this time. In phase II the NE was completely permeabilized within 35 s. This rapid permeabilization spread as a wave from one epicenter on the animal half across the nuclear surface and allowed free diffusion of particles up to ~100 nm in diameter into the nucleus. While the lamina and nuclear membranes appeared intact at the light microscopic level, a fenestration of the NE was clearly visible by electron microscopy in phase II. We conclude that NE breakdown in starfish oocytes is triggered by slow sequential disassembly of the NPCs followed by a rapidly spreading fenestration of the NE caused by the removal of nuclear pores from nuclear membranes still attached to the lamina.

The stimulation of oocyte maturation by 1-methyladenine in starfish, and by a steroid in frogs, has been proposed to involve G-protein-coupled receptors. To examine whether activation of receptors linked to [G.sub.i] or [G.sub.z] was sufficient to cause oocyte maturation, we expressed mammalian [G.sub.i]- and [G.sub.z]-linked receptors in starfish and frog oocytes. Application of the corresponding agonists caused meiosis to resume in the starfish but not the frog oocytes. We confirmed that the receptors were effectively expressed in the frog oocytes by using a chimeric G-protein, [G.sub.qi], that converts input from [G.sub.i]- and [G.sub.z]-linked receptors to a [G.sub.q] output and results in a contraction of the oocyte's pigment. These results argue against [G.sub.i] or [G.sub.z] functioning to cause maturation in frog oocytes. Consistently, maturation-inducing steroids did not cause pigment contraction in frog oocytes expressing [G.sub.qi], and [G.sub.z] protein was not detectable in frog oocytes. For starfish oocytes, however, our results support the conclusion that [G.sub.i] functions in 1-methyladenine signaling and suggest the possibility of using frog oocyte pigment contraction as an assay to identify the 1-methyladenine receptor. To test this concept, we coexpressed [G.sub.qi] and a starfish adenosine receptor in frog oocytes and showed that applying adenosine caused pigment contraction. Key Words: G-protein; receptor; oocyte maturation; frog; starfish.

The structure, distribution, and population abundance of Oreaster reticulatus (Linnaeus, 1758) in 47,157 ha of shallow-water habitat in the archipelago of Bocas del Toro, Panama, were assessed from May to October 2000. The reproductive cycle of the sea star was studied in Isla Solarte, from February 2000 to February 2001. In total, 4,818 sea stars were recorded with a mean density of 149.7 ind. [ha.sup.-1], and a population of over 7 million was estimated for the archipelago. O. reticulatus was absent in ca. 50% of the evaluated areas, possibly due to high runoff and sedimentation; highest density was observed in an intermediate-runoff regime (255 ind. [ha.sup.-1]). About 45% of the population was found in substrata dominated by seagrass (Thalassia testudinum) and coarse, calcareous sand, 51% occurred in habitats where coral reef patches were mixed with seagrass, and 4% exclusively on coral reefs. The average size, based on the major radius, was 9.5 cm (3-21 cm), with a population structure composed of ca. 83% juveniles and 17% adults. The average reproductive size, measured as major radius, was 15 cm, and the minimum was 7 cm. Both males and females with a maximum stage (IV) of gonad development were observed throughout the year. The gonad index showed three peaks of maximum reproductive activity, which is not comparable to studies from other localities. The reproductive cycle did not seem to be related to water temperature, which ranged from 27[degrees]C to 30[degrees]C, but may respond more closely to changes in local rainfall. This relationship was not statistically significant based on this 1-year study. These data provide a useful baseline for management of local populations in the face of an increasing harvest for the aquarium trade and as souvenirs.

Research has been conducted on the six-rayed sea stars of the genus Leptasterias. The molecular and morphological approaches combined with the molecular systematic results have been combined in investigating these species to establish the relationship between the traditional taxa and molecular lineages and the results indicate that the species correspond to the separate clades of a molecular phylogeny.

Research has been conducted on the regeneration rates of the starfish caught in a towed commercial fishing gears deployed on different sea bed types. The arm damage and loss have been investigated and the results indicate that there is no difference in regeneration rates between the fish caught by commercial gears and by a control set.

Arm damage is a widely reported but superficially investigated aspect of the biology of the starfish Asterias rubens L. In the present study, the incidence of arm damage was surveyed in populations of A. rubens at two sites in the Firth of Clyde, Scotland, and three sites in Gullmarsfjorden, Sweden. The mean ([+ or -]SD) incidence across all sites of individuals with basal arm damage (resulting from detachment at the basal autotomy plane) was 19.69 [+ or -] 8.86%, the incidence of those with distal arm damage (resulting from amputation at more distal levels) was 7.74 [+ or -] 10.01%. The mean incidence of arms with basal damage was 5.28 [+ or -] 4.12%, of those with distal damage 1.83 [+ or -] 2.45%. There was a significant negative correlation between size and the incidence of basal damage at all but one site, but no significant correlation between size and distal damage at any site. Mechanical tests on specimens of the aboral body wall from the basal region of the arm (which included the autotomy plane) and from a more distal region revealed that with increasing body size there was a significant increase in yield stress, ultimate stress and Young's modulus (stiffness) but no significant change in yield strain and ultimate strain. There was no significant difference between the relationships for basal and distal specimens. It is hypothesised that in larger individuals increased mechanical toughness replaces autotomy as an effective antipredator strategy. Using two methods to induce autotomy, a significant positive correlation between size and the delay between the onset of stimulation and arm detachment was found; this may represent a size-related decline in the efficiency of the autotomy mechanism through the relaxation of selection pressure. Since size is an unreliable indicator of age in A. rubens, the trends identified herein can be interpreted only tentatively as age-associated phenomena.

The superorder Forcipulatacea (Asteroidea, Echinodermata) includes two orders, the Brisingida and the Forcipulatida. The Forcipulatida is diverse, including the Asteriidae, Coscinasteriinae, Pedicellasteridae, Labidiasteridae, Neomorphasteridae, Pycnopodiinae (Asteriidae), Heliasteridae, and the Zoroasteridae, whereas the Brisingida is limited to the Brisingasteridae, Brisingidae, Freyellidae, Hymenodiscidae, and Odinellidae. A phylogenetic analysis of forcipulataceans using morphological characters resulted in 12 most parsimonious trees at a tree length of 68 steps. The Brisingida, recognized as basal in one early analysis and derived in another, is here considered to be derived. Two genera of pedicellasterids emerged as the sister group to the remaining Forcipulatida. Bremer and bootstrap measures show strong support for the brisingidan and zoroasterid plus neomorphasterid clades. Certain other traditional taxonomic groupings, including the Pedicellasteridae, Labidiasteridae, Asteriidae, and Pycnopodiinae, are not supported as monophyletic. Support for the pedicellasterids as a sister group to the remainder of the Forcipulatida is not robust. Morphological data suggest widespread homoplasy and therefore comprehensive generic or even species-level analyses are required to further evaluate questions of derivation and relationships among these taxa.

Tube-foot morphology has been included among a variety of taxonomic criteria for the Asteroidea over the past twenty-five years. Other than a few families belonging to the order Paxillosida, which are thought to have pointed, non-suckered tube feet that are used for digging and burial in soft sediments, the presumption has been that asteroids have flat-tipped, suckered tube feet. This has become an accepted model despite the fact that the comparative morphology of asteroid tube feet has not been considered. In the present study we examine tube-foot morphology of 45 species of Asteroidea representing 19 families. Our analysis confirms that members of the Luidiidae and Astropectinidae (order Paxillosida) lack suckers on the tips of their pointed tube feet. We demonstrate that there is considerable variation in tube-foot morphology among members of the Asteroidea including an entirely new type of flat-tipped, non-suckered tube foot in species belonging to the order Valvatida. The external morphology of tube feet in species belonging to the order Velatida could not be distinguished from "typical" flat-tipped, suckered tube feet; nonetheless, histological sections revealed a distinctive internal morphology. Finally, we report the first observations of the tube-foot morphology of representatives of deep-sea asteroids belonging to the orders Notomyotida and Brisingida, a group that also lacks the typical flat-tipped, suckered tube-foot morphology. The results of our study demonstrate that the current tube-foot morphology model needs to be reconsidered, as there is considerably greater variation than was previously believed to be the case. Moreover, we conclude that while tube-foot morphologies show consistent similarities within orders, tube-foot morphology is less appropriate as a taxonomic character below this level.

Because of limited research, a generally accepted hypothesis has not emerged for the phylogeny of the Asteroidea. The fossil record is a potential source of needed data, although fossil asteroids are rare, and they tend to be poorly preserved. Emphasis in the taxonomy of both recent and fossil asteroids has been on characters visible from the exterior, and paleontologists have sought to fit even the most ancient (i.e., Ordovician) specimens into taxonomic ordinal schemes devised for recent asteroids. Animal form and arrangement of body wall ossicles of Paleozoic asteroids can be similar to those of younger species, thereby suggesting close affinities, yet ambulacral arrangements indicate clear separation of Paleozoic stem groups from the crown group. Traits taken from the ambulacral column that mark crown-group asteroids include presence of dorsal podial pores (which allowed transfer of the ampullae to the arm interior), an offset arrangement of ambulacrals on the adambulacrals, and increased complexity of the articulation structures between ambulacrals and adambulacrals. Transfer of ampullae to the arm interior provided protection and more space for ampullae within the arm, as well as space within the furrow and between the ambulacral and adambulacral ossicles for elaboration of the soft tissues that enhance arm motion.

Nuclear proteins which are phosphorylated during meiotic maturation of starfish, Asterina pectinifera, oocytes have been studied to determine their chemical structure. Results indicate that it is likely that the tertiary structure of nucleic acid binding proteins (NAAPs) affects the target specificity of the cdc2 kinase.

Incubation of isolated germinal vesicles in the homogenate from maturing starfish oocytes resulted in synchronous germinal vesicle breakdown (GVBD), and chromosome condensation and gathering within 30 min. GVBD in this cell-free system required aerobic conditions. The endogenous ATP-generation system was preserved in the homogenate and effective under aerobic conditions, and thus exogenous ATP was not added to the homogenate. Injection of the homogenate into immature starfish oocytes induced meiotic maturation without 1-methyladenine, indicating high activity of maturation-promoting factor (MPF) in the homogenate. MPF activity in the homogenate was stable for 2 h at room temperature, while it disappeared within 1 h in the supernatant prepared by centrifugation of the homogenate. This disappearance of MPF activity is regulated by cyclin B destruction, similar to that seen in vivo. Key Words: starfish; oocyte; GVBD; cell free.

The gametes of the starfish Marthasterias glacialis were studied, both before and after fertilization, using several histochemical methods at the ultrastructural level. Results showed that the oocyte jelly coat (JC) could be morphologically differentiated into a fibrillar network of acidic polysaccharides, probably containing glycosaminoglycans (GAGs), and a loose component made of neutral polysaccharides that occupies the interstices of the former. Results also suggested that it is the fibrillar component of the JC to which the spermatozoon attaches and reacts. Staining of the acrosomal vesicle contents confirmed that the peripheral dense component attaches the spermatozoon to the JC, whereas the central and apical electron-lucent component coats the acrosomal process as it extends through the oocyte investments. The acrosomal process membrane was also shown to be negatively charged. Staining of cortical vesicles confirmed their tripartite compartmentalization: the spiral lamellae fused with the fertilization envelope (FE), transferring its staining to the inner layer of the FE, whereas the matrix could be subdivided into two components - a fibrillar mesh of acidic polysaccharides that fused with the FE and some amorphous aggregates that seem to become dispersed in the perivitelline space.

Histochemical studies revealed the presence of two major polysaccharides in the oocyte jelly coat (JC) of Marthasterias glacialis: a fibrillar component that contains carboxylic and sulfated groups and a loose component composed of neutral or weakly acidic polysaccharides. When isolated JC was submitted to cellulose acetate electrophoresis (CAE) and then stained with alcian blue, three bands appeared, of which one remained at the origin and two migrated toward the anode. Glycosaminoglycan-like molecules isolated from JC were separated by CAE into three main moving bands, two that present an R(sub f) similar to that of the intermediary moving band of total JC and one that has an R(sub f) similar to that of the faster moving band of total JC. These bands also have critical electrolyte points similar to those of total JC. Chondroitinase ABC mainly attacked the faster moving band, whereas protease and hyaluronidase seemed to digest all bands. These results and the R(sub f)s of isolated and standard glycosaminoglycans after mono- and bidimensional CAE suggest that the glycosaminoglycan-like molecules bear some resemblance to chondroitan sulfate, heparan sulfate, and hyaluronic acid.

The mechanism for the stimulation of meiotic maturation of starfish oocytes by the hormone 1-methyladenine was investigated. The study protocol involved the injection into starfish oocytes of mammalian G-protein alpha and beta-gamma subunits and of phosducin, a protein which binds G-protein beta-gamma subunits. The results showed that the beta-gamma subunit mediates the stimulation of oocyte maturation by 1-methyladenine, and is thus the primary stimulus for the maturation of starfish oocytes.

The effects of combinations of temperatureand salinity on the survival and growth of juvenile seastar (Patiriella pseudoexigua) were investigated. Laboratory-spawned, post-metamorphosed juvenile P. pseudoexigua were fed a diet of benthic algae Navicula sp. and exposed to different temperature and salinity regimes for 40 days. The results showed that both temperature and salinity had significant effects on juvenile survival and growth. The best temperature and salinity regimes for survival andgrowth are reported.

Fertilization of starfish eggs during meiosis results in rapid progression to embryogenesis as soon as meiosis II is completed. Unfertilized eggs complete meiosis and arrest in postmeiotic interphase for an, until now, indeterminate time. If they remain unfertilized, the mature postmeiotic eggs ultimately die. The aim of this study is to characterize the mechanism of death in postmeiotic unfertilized starfish eggs. We report that, in two species of starfish, in the absence of fertilization, postmeiotic interphase arrest persists for 16-20 h, after which time the cells synchronously and rapidly die. Dying eggs extrude membrane blebs, undergo cytoplasmic contraction and darkening, and fragment into vesicles in a manner reminiscent of apoptotic cells. The DNA of dying eggs is condensed, fragmented, and labeled by the TUNEL assay. Taken together, these data suggest that the default fate of postmeiotic starfish eggs, like their mammalian counterparts, is death by apoptosis. We further report that the onset and execution of apoptosis in this system is dependent on ongoing protein synthesis and is inhibited by a rise in intracellular [Ca.sup.2+], an essential component of the fertilization signaling pathway. We propose starfish eggs as a useful model to study developmentally regulated apoptosis. Key Words: programmed cell death; apoptosis; meiotic maturation; oocyte; postmeiotic egg; protein synthesis; starfish.

Spermatozoa of the starfish, Asterias amurensis, have a specific receptor for asterosap, a sperm-activating peptide isolated from the jelly coat of homologous eggs. We characterized the receptor by using several asterosap derivatives. Analysis of equilibrium binding of radioactive di-iodinated Bolton-Hunter reagent-labeled asterosap ([sup.125][I.sub.2]-BHP15) to the spermatozoa indicated that the cell has 1.1 x [10.sup.5] binding sites of high affinity ([K.sub.d] = 57 pM), and also the receptor showed positive cooperativity for asterosap binding. When spermatozoa were treated with fluorophore-labeled asterosap, the sperm flagella were labeled, indicating that the receptors are mostly localized in the sperm tail. When spermatozoa were reacted with radioactive asterosap prelabeled with photoaffinity cross-linkers, a single 130-kDa membrane protein of sperm flagella was specifically radiolabeled. This result was reproducible regardless of the length of spacer arm of cross-linkers so far studied. Therefore, the 130-kDa protein is likely to be the receptor for asterosaps. Modification of asterosap at the N-terminal region with bulky molecules such as carboxyfluorescein did not affect the activity of asterosap, suggesting that the N-terminus of asterosap is not involved in the ligand-receptor interaction. On the other hand, S-alkylated asterosaps did not compete with [sup.125][I.sub.2]-BHP15 for binding to the receptor, indicating that disulfide linkage of asterosap is essential for the ligand-receptor interaction. The properties of the receptor, high affinity and high concentration, enabled us to apply the fluorescence polarization technique to study the molecular interaction between asterosap and the receptor. Using this method, we performed binding experiments in almost real time and found that divalent cations are significantly involved in the interaction between asterosap and the receptor. [C] 2000 Academic Press Key Words: sperm-activating peptide; receptor; equilibrium binding; cross-linking; fluorescence polarization.

We examined the relationship between egg volume (ml) and egg energy content (J) in 48 species of echinoderms using regression analysis on published data. Two least squares regression models, a linear model (Y=a + bX) and a non-linear full allometric model (Y=a + bXk) were evaluated. Egg volume and energy content both spanned five orders of magnitude across these species. In general, egg energy scales isometrically, or nearly so, with egg volume. This result holds both within and among modes of development excepting planktotrophy, in which egg energy scales with negative allometry relative to egg size. Two Antarctic asteroids (Notasterias armata and Perknaster fuscus) deviated substantially from the general trend, suggesting exceptional features in their reproductive biology, meriting further investigation. Most regressions had an excellent fit, but predictive power was poor (as demonstrated previously for intraspecific relationships). These results raise serious questions about the valid use of egg size to infer levels of parental investment in life history studies

The possession of a water vascular system (including tube feet) makes the Echinodermata unique among the marine invertebrates. Tube foot morphology has historically been included among several characteristics used in taxonomic classification. Specifically, the presence or absence of a sucker on the distal end of the tube foot has been considered an important character in asteroid taxonomy. Nonetheless, asteroid tube foot morphology has been poorly studied from the perspective of its use as a taxonomic criterion. In the present study, the external and internal morphology of the tube feet from 46 species of asteroids representing 18 families were examined. The results reveal a novel tube foot morphology in representatives from several families that is intermediate between pointed non-suckered and suckered tube feet. Patterns of tube foot morphology are interpreted within the context of contemporary classification schemes among the Asteroidea.

Multiradiate starfish evolved independently in several families. The FIVE-PLUS hypothesis is that supernumary rays develop separately from the five primary rays. The ontogeny of the primary rays is proposed to be highly integrated (`en bloc' hypothesis), closely timed (synchronic), and `tamper proof'. The `en bloc' hypothesis postulates that the five primary rays develop as a unit. The deep structure of this unit is believed to be a 2-1-2, BA-A-BA, organization. The synchronic hypothesis postulates that there is only a brief time at metamorphosis during which the `en bloc' pathway operates. There is a pause before the development of supernumary rays. The `tamper proof' hypothesis postulates that the `eh bloc' pathway has no heritable variation and cannot be co-opted for the production of supernumary rays. There is diversity of timing and pattern in the development of supernumary rays. Postgeneration of rays in the rudiment and intercalary regeneration of rays in the imago are independent ray-producing pathways that may have been co-opted variously and recurrently in the multiple origins of multiradiate starfish.

Since 1987, phylogenetic approaches have sparked controversy over traditional views of asteroid systematics. Despite recent attempts at resolving these differences and, evidence of some consensus, our understanding of asteroid relationships is often viewed as unsatisfactory. Here, preliminary results of a broad phylogenetic study of the Asteroidea using DNA sequence data from both mitochondrial and nuclear genes are presented, showing insight to ordinal and familial relationships. This data and its potential for increasing our understanding of asteroid systematics will be evaluated in the context of previous work and future applications.

Starfish can use eyes at the tips of their arms to find their way home. Most sea-star species have compound eyes on their arms, but there has been no direct [...]

Echinoderms possess collagenous connective tissues that are capable of rapid, nervously mediated changes in their tensile strength. Arm autotomy in sea stars is facilitated by a rapid decrease in the tensile strength of connective tissues in the arm base. In this study, an autotomy-promoting factor (APF) has been isolated from the fluids released by scalded or autotomizing sea stars (Pycnopodia helianthoides). When injected into the coleom, APF elicits a complex behavioral response that culminates within minutes in multiple arm autotomy and a generalized softening of the body wall. Injection of fluid from intact, untreated sea stars does not promote the autotomy response. APF is a water soluble, heat-labile substance derived from the body wall. It is ammonium sulphate precipitable and its activity is reduced or destroyed by several proteolytic enzymes. On the basis of its gel permeation elution pattern, APF has [M.sub.r] of about 1200 Daltons. APF can be purified to a single peak of activity by reversed-phase HPLC. We conclude the substance is a peptide or has a peptide component.

The nervous system of the starfish Asterias rubens was subjected to immunocytochemical investigation using antisera raised against the molluscan neuropeptide FMRFamide. Immunoreactivity was detected in the radial nerve cords and the circumoral nerve ring, as well as in the sub-epithelial nerve plexus of the tube foot system. The hyponeural part of the radial cords contained numerous immunoreactive cell bodies. In the ectoneural tissue, immunoreactive cells were present in the epithelium, with cell bodies especially abundant in the lateral parts of the nerve, close to the site of emergence of the innervation to the tube feet. The sub-epithelial nerve plexus of the tube feet contained immunoreactive fibers that were continuous with an extensive system of ectoneural immunoreactive fibers in the radial nerve cords. Immunoreactive fibers were particularly evident in the regenerating radial nerves of previously sectioned arms.

The parasitic turbellarian Acholades asteris (Neorhabdocoela: Acholadidae) lives encysted on the ambulacral tube-feet of the starfish Coscinasterias calamaria in Tasmanian waters. Cysts, each containing one worm, generally occur singly as spindle-shaped protrusions from near the bases of the tube-feet; the cyst wall consists of tube-foot epidermis, with nervous tissue, and part of the outer layer of the tube-foot's two-layered connective tissue sheath. The inner layer, musculature, and coelomic epithelium are not involved, and the tube-foot remains functional. The turbellarian lies within the split outer layer with its anterior towards the base of the tube-foot. It lacks mouth, pharynx, and intestine and feeds via its ciliated epidermis on the surrounding collagenous and cellular materials. These are partially digested by enzymes from epidermal and subepidermal glands, products are pinocytosed, and digestion is completed in epidermal phagosomes formed by fusion of pinocytotic vesicles. Food uptake occurs over the entire body surface but especially anteriorly where the epidermis is thicker, deeply invaginated, and underlain by concentrations of gland cells. In approximately 25% of flatworms examined, the epidermis and adjacent parenchyma contained trophozoites and other stages of Monocystella sp., an aseptate gregarine whose other, known, species occur in turbellarian alimentary systems.

Bacterivory: A Novel Feeding Mode for Asteroid Larvae ECHINODERM LARVAE HAVE A COSMOPOLITAN distribution (1). They can ingest phytoplankton, bacteria, and detritus (2-4) as well as directly absorb dissolved organic [...]