Coral reef associated marine invertebrates, such as the blue sea star Linckia laevigata, have a life history with two phases: sedentary adults and planktonic larvae. On the one hand it is hypothesised that the long pelagic larval duration facilitates large distance dispersal. On the other hand, complex oceanographic and geographic characteristics of the Visayan seascape could cause isolation of populations. The study aims to investigate the genetic diversity, genetic population structure and gene flow in L. laevigata to reveal connectivity among populations in the Visayas. The analysis is based on partial sequences (626 bp in length) of the mitochondrial cytochrome oxidase I gene (COI) from 124 individuals collected from five localities in the Visayas. A comparative analysis of these populations with populations from the Indo-Malay Archipelago (IMA) published previously is also presented. Genetic diversity was high (h = 0.98, π = 1.6%) and comparable with preceding studies. Analyses of molecular variance (AMOVA) revealed a lack of spatial population differentiation among sample sites in the Visayas (ΦST-value = 0.009; P > 0.05). The lack of genetic population structure indicates high gene flow among populations of L. laevigata in the Visayas. Comparative analysis with data from the previous study indicates high connectivity of the Visayas with the central part of the IMA.

Specimens collected in or near Pensacola Bay, Florida matching the descriptions of Luidia lawrencei and Luidia clathrata (the congener from which L. lawrencei was recently split) were compared to determine whether their recent taxonomic separation is supported by differences in sediment preference, salinity tolerance and COX-1 mtDNA sequences. Luidia clathrata has a preference for smaller grain sizes, while no statistically significant preference was found for Luidia lawrencei, and no significant difference was found between the species. Luidia clathrata is more tolerant of lower salinity based on the righting response than Luidia lawrencei, especially at salinities lower than 25 g kg−1. The COX-1 comparison returned over 99% homology among individuals of the two species. While sediment preference and salinity tolerance results indicate differences in response to habitat dissimilarities, the COX-1 genetic result is strong evidence against the recently proposed separation of the species. In light of the COX-1 result, we interpret the sediment and salinity results as long-term acclimation responses.

The starfish Pharia pyramidatus is a tropical species of high ecological importance, mainly because of its role as generalist predator. Nevertheless, there are no studies about its reproduction. This study analysed the reproductive biology of P. pyramidatus based on monthly time-series samples from April 2008 to March 2009 at Isla Montosa in the Mexican tropical Pacific. The gonad index (GI), and pyloric caecum index (PCI) were determined and the results were corroborated by histological examination of the gonads. Pharia pyramidatus is a gonochoric asteroid and the ratio of males to females was not significantly different throughout the year. Gametogenesis showed high synchrony among males and females and five stages were recognized for both sexes. Spawning occurred from July to September. Maximum oocyte size was ~150 μm and mean fecundity was 7.3 ± 1.2 millions of oocytes per female. GI and PCI showed seasonal variations and an inverse relationship from May to August. Sea-bottom temperature and photoperiod showed a direct relationship with GI, and apparently constitute the proximate causes of the seasonal reproductive pattern observed in P. pyramidatus, while the highly seasonal rainfall and strong upwelling probably act as ultimate causes.

Living specimens of the amphi-Atlantic asteroid Hacelia superba have been collected in different areas of Gazul mud volcano in the Gulf of Cadiz, south-western Iberian Peninsula, at depths of 380–487 m. This starfish displayed low abundances (~1 ind. 2000 m−2) in beam trawl catches on the mud vulcano and adjacent soft bottoms. The absence of previous records in this area could be due to a low sampling effort on bathyal hard bottoms of the Gulf of Cadiz, especially those of dormant mud volcanoes, as well as a possible misidentification as Hacelia attenuata that also occurs in the area but is restricted to infralittoral and circalitoral bottoms.

To highlight the diversity of extracellular embryonic matrix (ECM) secreting structures in the gastrulae of the starfish Pisaster ochraceus the localization of antibody generated to hyaline layer, was studied. It was shown that hyaline layer epitope takes place in the cortical granules. Moreover, this material was revealed in secretory vacuoles and secretory vesicles which are situated in the apical parts of ectoderm cells. Besides, the same molecules were found in the yolk granules having loosened content. It seems likely that in P. ochraceus the ECM is secreted by four types of secretory structures.

The relative importance of parental diet/population and larval diet were examined on egg, growth, morphology and biochemistry of Sclerasterias mollis larvae. Adult S. mollis were fed one cockle (Austrovenus stutchburyi) per two animals each week, as a low diet, or two cockles per animal each week, as a high diet. The experiment was run for one year. In addition, two field populations (Otago inshore and offshore) with dissimilar nutritional status (based on the gonad index) were selected. Otago inshore starfish had higher gonad indices and assumed to have better nutritional status. The low and high diet laboratory starfish produced eggs with similar characteristics. Eggs from the low diet laboratory parents had the highest carbohydrate concentration. The eggs from the field parents had higher fertilization rate and lower carbohydrate concentration than eggs from the laboratory parents. The Otago inshore starfish had smaller eggs with a lower carbohydrate concentration than the starfish from Otago offshore. Parents from the laboratory or the field had significant effects on larval growth, morphological phenotypic plasticity (measured by the body length relative to the body width) and development rate. Larvae from Otago offshore parents had highest growth and morphological phenotypic plasticity. Larvae from the low diet laboratory parents and those from Otago inshore had the highest development rate. Larvae from low diet laboratory parents had the highest carbohydrate concentration. Neither the parents nor the larval diet had a significant effect on larval mortality. A higher concentration planktonic diet resulted in higher growth, morphological phenotypic plasticity and development rate. Parents were however more important than larval diet on growth and phenotypic plasticity of the larvae. This study showed that parental nutrition has an important effect on growth, morphological phenotypic plasticity and body composition of S. mollis larvae. The nutritional status of the parents does not influence the larvae through a change in the egg size, protein, lipid, carbohydrate and energy content.

In recent years there has been an increasing interest in the effects of water temperature changes on the structure of marine populations. During the 1970s the burrowing starfish Astropecten jonston was present in large numbers along the south-east of Sardinia (Italy). When investigations were resumed in 1999 fewer active individuals could be found than in the 1970s, with anecdotal evidence suggesting an increase in sightings of dying animals on the sand surface. These observations, combined with a hitherto unknown susceptibility to handling stress, caused us to investigate the effect of water temperature, salinity and individual size on A. jonstoni survival. Results indicated that significantly fewer starfish were affected by a wasting disease when kept at 12°C compared with individuals maintained at 20°C and 25°C regardless of salinity (28 or 35 ppt) and that smaller starfish were less affected. Microbiological analysis revealed that, amongst other species, bacteria of the genus Vibrio, which have been associated with diseases of stressed marine invertebrates, were present in both field and laboratory animals.

The existence of two Pisaster ochraceus subspecies has been proposed; one located northwards (P. ochraceus ochraceus) and the other southwards (Pisaster ochraceus segnis) from Point Conception. We used polymerase chain reaction–restriction fragment length polymorphism of the CO I and CO III mitochondrial genes to assess the degree of population structure from 126 samples collected along the western coast of North America, from Vancouver, Canada to Punta San Carlos, of Baja California, Mexico. The genetic structure was tested through molecular analysis of variance and by Monte Carlo simulations of the original data set. The phylogeographical pattern was deduced from a minimum spanning network analysis. No genetic structure was detected. Instead, a high degree of genetic homogeneity along the species distribution was evident from haplotype frequencies at each location. Two haplotypes, Po1 and Po5, were predominant along the distribution and were considered ancestral because of their central position in the minimum spanning network. Since Pisaster ochraceus depicts a planktotrophic larval stage with very long duration before settlement, it seems to be able to surpass the biogeographical boundary that limits other species around Point Conception, thereby maintaining homogeneity of its genetic pool. Results of this study recognize P. ochraceus as a single species.

The acrosome reaction (AR) is a fundamental event for fertilization, which is induced in concert with acrosome reaction-inducing substance (ARIS) and asterosap, both of which are components of starfish egg jelly (EJ). During the AR, a spermatozoon undergoes a series of physiological changes, such as in intracellular cGMP concentration ([cGMP]i), pHi and intracellular Ca2+ concentration ([Ca2+]i). Affinity purification of cGMP-binding protein resulted in the isolation of a regulatory subunit of the cAMP-dependent protein kinase A (PKA), suggesting the involvement of a cAMP-dependent pathway in the AR. By using a cAMP enzyme immunoassay, [cAMP]i was found to increase in starfish spermatozoa when stimulated with ARIS and asterosap. ARIS could also increase the [cAMP]i in the presence of high pH seawater. Pretreatment of spermatozoa with two specific and cell-permeable PKA inhibitors, H89 and KT5720, prevented the induction of the AR in a concentration-dependent manner. These results suggest that PKA activity participates in the induction of the AR with ARIS and asterosap. To investigate this, we have cloned a gene that encodes a regulatory subunit of PKA that had been identified in starfish spermatozoa.

Asterosap, a group of equally active isoforms of sperm-activating peptides from the egg jelly of the starfish Asterias amurensis, functions as a chemotactic factor for sperm. It transiently increases the intracellular cGMP level of sperm, which in turn induces a transient elevation of intracellular Ca2+ concentration ([Ca2+]i). Using a fluorescent Ca2+-sensitive dye, Fluo-4 AM, we measured the changes in sperm [Ca2+]i in response to asterosap. KB-R7943 (KB), a selective inhibitor of Na+/Ca2+ exchanger (NCX), significantly inhibited the asterosap-induced transient elevation of [Ca2+]i, suggesting that asterosap influences [Ca2+]i through activation of a K+-dependent NCX (NCKX). An NCKX activity of starfish sperm also shows K+ dependency like other NCKXs. Therefore, we cloned an NCKX from the starfish testes and predicted that it codes for a 616 amino acid protein that is a member of the NCKX family. Pharmacological evidence suggests that this exchanger participates in the asterosap-induced Ca2+ entry into sperm.

The obtention of hydroxyapatite (HAp) is reported using brushite (CaHPO4·2H2O) and the skeleton of a starfish (Mellita eduardobarrosoi sp. nov.), primarily composed of magnesian calcite ((Ca,Mg)CO3) as precursors. Stoichiometric amounts of both were reacted under hydrothermal conditions: a pressure of 5.8 MPa and a temperature of 200°C for 2, 4, 6, 8, 10, and 20 h of reaction times. The samples obtained were characterized by means of scanning electron microscopy, X-ray diffraction, infrared spectroscopy, and transmission electron microscopy. Two defined populations of HAp fibers were found: A bundle of fibers 75 μm in length and 1–13 μm in diameter, and a second bundle of fibers 5 μm in length and less than 0.5 μm in diameter. Furthermore, an increase in HAp formation and a Ca/P ratio as a function of reaction time were observed. The growth mechanism of HAp is also discussed.

In the starfish, Asterias amurensis, the cooperation of three components of the egg jelly, namely ARIS (acrosome reaction-inducing substance), Co-ARIS and asterosap, is responsible for the induction of acrosome reaction. For the induction, ARIS alone is enough in high-Ca2+ or high-pH seawater, but, besides ARIS, the addition of either Co-ARIS or asterosap is required in normal seawater. Asterosap transiently increased both the intracellular pH (pHi) and Ca2+ ([Ca2+]i), while ARIS slightly elevated the basal level of [Ca2+]i. However, a sustained elevation of [Ca2+]i and acrosome reaction occurred if sperm were simultaneously treated with ARIS and asterosap. EGTA inhibited the sustained [Ca2+]i elevation and acrosome reaction. The sustained [Ca2+]i elevation and acrosome reaction were highly susceptible to SKF96365 and Ni2+, specific blockers of the store-operated Ca2+ channel (SOC). These results suggest that sustained [Ca2+]i elevation, mediated by the SOC-like channel, is a prerequisite for the acrosome reaction. In high-pH seawater, ARIS alone induced a prominent [Ca2+]i increase and acrosome reaction, which were similarly sensitive to SKF96365. The acrosome reaction was effectively induced by ARIS alone when pHi was artificially increased to more than 7.7. Asterosap increased pHi from 7.6±0.1 to 7.7±0.1. Furthermore, the sustained [Ca2+]i elevation and acrosome reaction, induced by a combination of ARIS and asterosap, were drastically inhibited by a slight reduction in pHi. Taking these results into account, we suggest that an asterosap-induced pHi elevation is required for triggering the ARIS-induced sustained [Ca2+]i elevation and consequent acrosome reaction.

In the starfish, Asterias amurensis, the cooperation of three components of the egg jelly, i.e. ARIS (acrosome reaction-inducing substance), Co-ARIS and asterosap, is responsible for inducing the acrosome reaction. Experimentally, ARIS and asterosap are sufficient for the induction. However, when sperm are treated only with asterosap, they become unresponsive to the egg jelly to undergo the reaction. In this study, we analysed the mechanism of the acrosome reaction, using sperm inactivation by asterosap as a clue. Asterosap causes a rapid and transient increase in intracellular cGMP through the activation of the asterosap receptor, a guanylyl cyclase, and causes an increase in intracellular Ca2+. When sperm were pretreated with asterosap, the guanylyl cyclase seemed to be inactivated irreversibly by dephosphorylation. They were still responsive to ARIS but no longer to asterosap. However, in the presence of IBMX or zaprinast, inhibitors against phosphodiesterases (PDEs), they retained their capacity to undergo the acrosome reaction in response to the egg jelly or ARIS alone. IBMX and zaprinast suppressed the intracellular catabolism of cGMP, but not of cAMP. These results suggest that guanylyl cyclase and cGMP-specific, IBMX- and zaprinast-susceptible PDEs are involved in the regulation of the acrosome reaction.