Sea Urchin Larvae Research Articles

Integrative sediment assessment at Atlantic Spanish harbours by means of chemical and ecotoxicological tools

This study refers to the integrative assessment of sediment quality in three harbour areas at the Spanish Atlantic Coast: Vigo (Northwestern Spain), Bilbao and Pasajes (Northern Spain). At each site, two lines of evidence have been considered: chemical analyses (metal, PAH and PCB concentrations in sediments and ammonia concentration in bioassays) and toxicity tests (Microtox®, Corophium sp. marine amphipod and Paracentrotus lividus sea urchin larvae). Chemical and ecotoxicological results have been integrated by means of a tabular matrix and a multivariate factorial analysis (FA). Highly toxic samples have been characterised in Vigo and Pasajes harbours while Bilbao samples present toxicity levels ranging from non-toxic to moderately toxic. High toxicity is associated with high levels of contaminants whereas confounding factors (ammonia, organic matter and mud) have been identified to be the main cause of low to moderate toxicity. Based on the obtained results, it can be concluded that deriving potential toxicity of sediments based on comparison with Sediment Quality Guidelines (SQGs) is in agreement to toxicity results in areas presenting high levels of contaminants. However, at lower levels of toxicity (low to moderate), the mismatch between the potential toxicity (SQG approach) and the toxicity measured by bioassays is greater, as the former only accounts for chemical concentrations, without considering the interaction between contaminants and the effect of confounding factors. Contrarily, the multivariate analysis seems to be a robust tool for the integration and interpretation of different lines of evidence in areas affected by different sources of contamination.

Binding Properties of Thyroxine to Nuclear Extract from Sea Urchin Larvae

We previously reported that thyroid hormones are involved in the formation of the adult rudiment and adult-type skeleton in sea urchin larvae, as well as in the resorption of larval tissues. In the present study, to search for the presence of thyroid hormone receptor in sea urchin larvae, we performed a ligand-binding assay between radiolabeled thyroid hormones and nuclear extracts from the larvae of the sea urchin Hemicentrotus pulcherrimus. The presence of binding sites with a high affinity to thyroxine (T4) was detected in the nuclear extract, but not in the cytoplasmic fraction. The dissociation constants for the T4 binding to the nuclear extracts were estimated to be about 18 pM from the mesenchyme-blastula stage to the four-armed pluteus stage. The quantity of T4 binding sites in the nuclear extracts increased during larval development. These results suggest that the binding affinity to T4 in the nuclear extracts was caused by a putative nuclear thyroid hormone receptor in sea urchin larvae.

Identification of specific malformations of sea urchin larvae for toxicity assessment: Application to marine pisciculture effluents

Standard toxicity screening tests are useful tools in the management of impacted coastal ecosystems. To our knowledge, this is the first time that the sea urchin embryo development test has been used to evaluate the potential impact of effluents from land-based aquaculture farms in coastal areas. The toxicity of effluents from 8 land-based turbot farms was determined by calculating the percentage of abnormal larvae, according to two criteria: (a) standard, considering as normal pyramid-shaped larvae with differentiated components, and (b) skeletal, a new criterion that considers detailed skeletal characteristics. The skeletal criterion appeared to be more sensitive and enabled calculation of effective concentrations EC5, EC10, EC20 and EC50, unlike the classical criterion. Inclusion of the skeleton criterion in the sea urchin embryo development test may be useful for categorizing the relatively low toxicity of discharges from land-based marine fish farms. Further studies are encouraged to establish any causative relationships between pollutants and specific larval deformities.

Dissolved histamine: a potential habitat marker promoting settlement and metamorphosis in sea urchin larvae

Many species of marine invertebrate larvae settle and metamorphose in response to chemicals produced by organisms associated with the adult habitat, and histamine is a cue for larvae of the sea urchin Holopneustes purpurascens. This study investigated the effect of histamine on larval metamorphosis of six sea urchin species. Histamine induced metamorphosis in larvae of three lecithotrophic species (H. purpurascens, Holopneustes inflatus and Heliocidaris erythrogramma) and in one planktotrophic species (Centrostephanus rodgersii). Direct comparisons of metamorphic rates of lecithotrophic and planktotrophic larvae in assays cannot be made due to different proportions of larvae being competent. Histamine (10 μM) induced metamorphosis in 95% of larvae of H. purpurascens and H. inflatus after 1 h, while the coralline alga Amphiroa anceps induced metamorphosis in 40–50% of these larvae. Histamine (10 μM) and A. anceps induced 40 and 80% metamorphosis, respectively, in the larvae of H. erythrogramma after 24 h. Histamine (10 μM) and the coralline alga Corallina sp. induced 30 and 70% metamorphosis, respectively, in the larvae of C. rodgersii after 24 h. No metamorphosis of any larval species occurred in seawater controls. Larvae of two planktotrophic species (Tripneustes gratilla and Heliocidaris tuberculata) did not metamorphose in response to histamine. Seagrasses, the host plants of H. inflatus, induced rapid metamorphosis in larvae of the two Holopneustes species, and several algae induced metamorphosis in C. rodgersii larvae. Histamine leaching from algae and seagrasses may act as a habitat marker and metamorphic cue for larvae of several ecologically important sea urchin species.

Iodine accumulation in sea urchin larvae is dependent on peroxide

Iodine has many important biological functions and its concentrations vary with the environment. Recent research has provided novel insights into iodine uptake mechanisms in marine bacteria and kelp through hydrogen peroxide-dependent diffusion (PDD). This mechanism is distinct from sodium-dependent mechanisms known from vertebrates. In vertebrates, iodine accumulates in the thyroid gland by the action of the apical iodide transporter (AIT) and the sodium/iodide symporter (NIS). Neither of these proteins has, thus far, been identified outside of the chordates, and PDD (as an iodine uptake mechanism) has never been studied in animals. Using (125)I as a marker for total iodine influx, we tested iodine uptake via sodium-dependent transport versus PDD in embryos and larvae of the sea urchin Strongylocentrotus purpuratus. We found that iodine uptake in S. purpuratus is largely independent of NIS/AIT. Instead, we found that uptake is dependent on the presence and production of hydrogen peroxide, indicating that sea urchin larvae use PDD as a mechanism for iodine acquisition. Our data, for the first time, provide conclusive evidence for this mechanism in an animal. Furthermore, our data provide preliminary evidence that sodium-dependent iodine uptake via active transporter proteins is a synapomorphy of vertebrates.

Agglomeration of Silver Nanoparticles in Sea Urchin

Silver nanoparticles (AgNPs) are one of the most important nanomaterials for toxicological study due to their extensive use in consumer products and their potential effects on both human and animal health, and the environment. There is, however, insufficient information on their impact on the marine environment. Here, we study the effect of AgNPs in sea urchin (Paracentrotus lividus) development by X-ray absorption near edge structure (XANES) and Fourier transform infrared (FTIR) spectroscopy. Agglomerated AgNPs were observed in sea urchin larva at 51 h after exposure to AgNPs with a concentration of 0.3 mg/L. XANES shows that agglomerated AgNPs contain oxidized Ag species complexed with S and O/N ligands. FTIR results confirm the presence of additional sulphur compounds suggestive of a biological response to the toxicity of AgNPs in the sea urchins. Additionally, it could be concluded from the FTIR results that there is a loss of calcite in the sea urchins exposed to AgNPs.

Influence of microalgal species and dietary rations on larval development and survival of the purple sea urchin, Strongylocentrotus purpuratus (Stimpson, 1857)

This study evaluated the effect of diet and ration on the growth and survival of larvae of the purple sea urchin, Strongylocentrotus purpuratus. Larval total length, mid-line body length, body width, post-oral arm length, time to reach metamorphic competency, and survival rate were assessed during the experimental period (28 days). In the first experiment, seven algal diets [ i.e. Dunaliella tertiolecta, Chaetoceros muelleri, Isochrysis sp. (Tahitian strain) and all possible binary and tertiary combinations] were assessed, along with a control treatment of no food. Larvae reared on the bi-algal diet of D. tertiolecta/ Isochrysis sp. and the uni-algal diet of D. tertiolecta provided significantly better growth than all other treatments. Larvae were successfully raised to metamorphic competency with both the binary combination of D. tertiolecta/ Isochrysis sp. and the single species D. tertiolecta within 28 days of culture, whereas larvae in all other dietary treatments failed to reach competence within 28 days. In the second experiment, a bi-algal diet ( D. tertiolecta and Isochrysis sp. at equal biovolumes) was evaluated using five rations: (1) low ration: 1.25 × 10 3 cells ml − 1 ; (2) normal ration: 2.5 × 10 3 cells ml − 1 ; (3) standardized ration: 2.5 × 10 3 to 10.0 × 10 3 cells ml − 1 , with increasing ration according to developmental stage; (4) medium ration: 5.0 × 10 3 cells ml − 1 ; and (5) high ration: 10.0 × 10 3 cells ml − 1 . Typical echinoid larval development in all body dimensions was only achieved for larvae offered the standardized ration. Larvae reared on this ration attained metamorphic competency within 28 days, whereas larvae fed the fixed rations (lower or higher concentrations) failed to attain competency by the end of the experiment. In general, in comparison to larvae fed the standardized ration, larvae on the low ration showed longer post-oral arm length and narrower body width whereas larvae on the high ration showed shorter post-oral arm length and body width in relation to their total length. Overall survival (from prism stage to metamorphic competency) for the best treatments in both experiments was 44.4 ± 2.9 and 53.3 ± 1.9% (mean ± SE) for the binary diet of D. tertiolecta/ Isochrysis sp. and standardized ration treatments, respectively. Based on these results, larvae fed a binary combination of D. tertiolecta and Isochrysis sp. or D. tertiolecta alone with a ration increasing with developmental stage is recommended for hatchery production of S. purpuratus.

Rapid adaptation to food availability by a dopamine-mediated morphogenetic response.

Food can act as a powerful stimulus, eliciting metabolic, behavioral and developmental responses. These phenotypic changes can alter ecological and evolutionary processes; yet, the molecular mechanisms underlying many plastic phenotypic responses remain unknown. Here we show that dopamine signaling through a type-D2 receptor mediates developmental plasticity by regulating arm length in pre-feeding sea urchin larvae in response to food availability. While prey-induced traits are often thought to improve food acquisition, the mechanism underlying this plastic response acts to reduce feeding structure size and subsequent feeding rate. Consequently, the developmental program and/or maternal provisioning predetermine the maximum possible feeding rate, and food-induced dopamine signaling reduces food acquisition potential during periods of abundant resources to preserve maternal energetic reserves. Sea urchin larvae may have co-opted the widespread use of food-induced dopamine signaling from behavioral responses to instead alter their development.

Species-specific effects of fluid shear on grazing by sea urchin larvae: comparison of experimental results with encounter-model predictions

Small-scale turbulence can alter the rate of plankton predator–prey encounters. Encounter models predict that prey ingestion by slow-swimming zooplankton is enhanced at low levels of turbulence. We investigated whether small-scale turbulence increases ingestion for the slow-swimming, suspension-feeding pluteus larvae of the white urchin Lytechinus pictus and the purple urchin Strongylocentrotus purpuratus. Model predictions of the critical level of turbulence, ecr, above which encounters due to turbulence are greater than those due to behavior (swimming or suspension feeding) alone, were experimentally tested using shortand long-term grazing treatments. Because urchin larvae are smaller than the smallest eddy scales of turbulence and thus experience turbulence as laminar shear, larvae were exposed to flow conditions using a simple laminar shear flow with dissipation rates, e, of 0, 0.1, 0.4, and 1 cm2 s–3. Short-term ingestion of beads by L. pictus larvae was unaffected by e < 1 cm2 s–3 but was 30% greater at this level, which was greater than ecr based on flow speeds produced in suspension feeding. Long-term flow treatments with algal prey had no significant effect on grazing or growth. Short-term ingestion of beads by S. purpuratus larvae was unaffected by e < ecr based on suspension feeding; the effect of long-term flow exposure on ingestion and growth could not be investigated because of high mortality, suggesting greater sensitivity to flow exposure compared to L. pictus. Experimental results are consistent with model predictions that ecr is high, and thus levels of turbulence in the ocean are not expected to significantly increase ingestion and reduce food limitation in suspension-feeding urchin larvae.

Crystallization Pathways in Biomineralization

A crystallization pathway describes the movement of ions from their source to the final product. Cells are intimately involved in biological crystallization pathways. In many pathways the cells utilize a unique strategy: They temporarily concentrate ions in intracellular membrane-bound vesicles in the form of a highly disordered solid phase. This phase is then transported to the final mineralization site, where it is destabilized and crystallizes. We present four case studies, each of which demonstrates specific aspects of biological crystallization pathways: seawater uptake by foraminifera, calcite spicule formation by sea urchin larvae, goethite formation in the teeth of limpets, and guanine crystal formation in fish skin and spider cuticles. Three representative crystallization pathways are described, and aspects of the different stages of crystallization are discussed. An in-depth understanding of these complex processes can lead to new ideas for synthetic crystallization processes of interest to materials science.

Sea urchin Arbacia dufresnei (Blainville 1825) larvae response to ocean acidification

Increased atmospheric CO2 emissions are inducing changes in seawater carbon chemistry, lowering its pH, decreasing carbonate ion availability and reducing calcium carbonate saturation state. This phenomenon, known as ocean acidification, is happening at a faster rate in cold regions, i.e., polar and sub-polar waters. The larval development of Arbacia dufresnei from a sub-Antarctic population was studied at high (8.0), medium (7.7) and low (7.4) pH waters. The results show that the offspring from sub-Antarctic populations of A. dufresnei are susceptible to a development delay at low pH, with no significant increase in abnormal forms. Larvae were isometric between pH treatments. Even at calcium carbonate (CaCO3) saturation states (of both calcite and aragonite, used as proxies of the magnesium calcite) <1, skeleton deposition occurred. Polar and sub-polar sea urchin larvae can show a certain degree of resilience to acidification, also emphasizing A. dufresnei potential to poleward migrate and further colonize southern regions.

Pengaruh Penambahan Vitamin B pada Media Blotong 12 Kering terhadap Pertumbuhan Populasi Dunaliella salina &lt;br&gt;&lt;i&gt;[Effect of Adding Vitamin B on Blotong Dry Media 12 Againts Population Growth Dunaliella salina]&lt;i&gt;

Abstract Dunaliella salina is one natural food that is good enough for the larvae of sea urchins and also can be used as food Brachionus plicatilis and Artemia in aquaculture feed Artemia. Blotong is precipitated in the process of purification juice before cooking and crystallized into sugar. Purification is a process to separate the juice from dirt or fibers. Sugarcane is used as fertilizer by using oven dried first. Vitamin B is needed some algae to build 12 proteins and essential as a coenzyme necessary for DNA synthesis in the formation of new cells. Vitamin B is a 12 coenzyme B -dependent methionine synthase and vitamin B -dependent ribonucleotide reductase. Vitamin B 12 12 12 dependent methionine synthase function for synthesis methionin (essential amino acids), whereas vitamin B 12 dependent ribonucleotide reductase functions to DNA synthesis. This study aims to determine the effect of vitamin B in dry blotong media on the growth of D. salina 12 population and to determine the optimal dosage of vitamin B in dry blotong media which can produce the highest 12 population growth of D. salina. This research used Completely Randomized Design (CRD) with seven treatments and three replications. The study used namely: Fertilizer blotong dried with the addition of vitamin B 10 g / L (A), dose of 12 12 ug / L (B), the dose of 14 ug / L (C), a dose of 16 ug / L (D), dose 18 ug / L (E), a dose of 20 ug / L (F) and control treatment of dry sugarcane fertilizer without adding vitamin B12 or dose 0 g / L (G). The main parameter used is the population of D. salina, while supporting the water quality parameters (salinity, pH and water temperature). Data were analyzed with ANOVA (analysis of variants) and to know the differences among the treatments performed Duncan's Multiple Range Test. The results showed that the addition of vitamin B in dry blotong media had no effect on the growth of population D. salina (p&gt; 0.05).

Oxidative Damage in Response to Natural Levels of UV‐B Radiation in Larvae of the Tropical Sea Urchin Tripneustes gratilla

To assess the effects of UV radiation (280-400nm) on development, oxidative damage and antioxidant defence in larvae of the tropical sea urchin Tripneustes gratilla, a field experiment was conducted at two depths in Aitutaki, Cook Islands (18.85°S, 159.75°E) in May 2008. Compared with field controls (larvae shielded from UV-R but exposed to VIS-radiation), UV-B exposure resulted in developmental abnormality and increases in oxidative damage to proteins (but not lipids) in embryos of T. gratilla held at 1m depth. Results also indicated that larvae had the capacity to increase the activities of protective antioxidant enzymes when exposed to UV-B. The same trends in oxidative damage and antioxidant defence were observed for embryos held at 4m, although the differences were smaller and more variable. In contrast to UV-B exposure, larvae exposed to UV-A only showed no significant increases in abnormality or oxidative damage to lipids and proteins compared with field controls. This was true at both experimental depths. Furthermore, exposure to UV-A did not cause a significant increase in the activities of antioxidants. This study indicates that oxidative stress is an important response of tropical sea urchin larvae to exposure to UV radiation.

Impact of Ocean Warming and Ocean Acidification on Larval Development and Calcification in the Sea Urchin Tripneustes gratilla

BackgroundAs the oceans simultaneously warm, acidify and increase in P CO2, prospects for marine biota are of concern. Calcifying species may find it difficult to produce their skeleton because ocean acidification decreases calcium carbonate saturation and accompanying hypercapnia suppresses metabolism. However, this may be buffered by enhanced growth and metabolism due to warming.Methodology/Principal FindingsWe examined the interactive effects of near-future ocean warming and increased acidification/P CO2 on larval development in the tropical sea urchin Tripneustes gratilla. Larvae were reared in multifactorial experiments in flow-through conditions in all combinations of three temperature and three pH/P CO2 treatments. Experiments were placed in the setting of projected near future conditions for SE Australia, a global change hot spot. Increased acidity/P CO2 and decreased carbonate mineral saturation significantly reduced larval growth resulting in decreased skeletal length. Increased temperature (+3°C) stimulated growth, producing significantly bigger larvae across all pH/P CO2 treatments up to a thermal threshold (+6°C). Increased acidity (-0.3-0.5 pH units) and hypercapnia significantly reduced larval calcification. A +3°C warming diminished the negative effects of acidification and hypercapnia on larval growth.Conclusions and SignificanceThis study of the effects of ocean warming and CO2 driven acidification on development and calcification of marine invertebrate larvae reared in experimental conditions from the outset of development (fertilization) shows the positive and negative effects of these stressors. In simultaneous exposure to stressors the dwarfing effects of acidification were dominant. Reduction in size of sea urchin larvae in a high P CO2 ocean would likely impair their performance with negative consequent effects for benthic adult populations.

Spawning Behavior and Early Life History of the Sharpnose Puffer, Canthigaster rivulata, in the Aquarium

Specimens ofCanthigaster rivulata (Temminck et Schlegel) were collected from Kominato and Hayama, central Japan, from May, 1985 to October, 1986. On the basis of the gonadosomatic index, gonadal histology and results of artificial fertilization of these specimens, the spawning season is considered to extend from late June to mid-September. The specimens exhibited the following dimorphic differences associated with sex: 1) The male is larger than the female. 2) Ventral side of the body is brownish orange in the male with vermiculated or reticulated patterns of bright violet, while it is white in the female. 3) The male has a well-developed skin fold along the mid-dorsal and mid-ventral lines, which is greatly elevated during courtship; whereas the female’s skin folds are not or slightly developed and conspicuous only during courtship. In an aquarium with the water temperatures of 22 to 26°C, a pair of fish spawned every four days late in the morning for three consecutive months. Courtship and spawning occurred in a pair. The male swam in front of the female, and elevated the skin folds both dorsally and ventrally, fully spreading the unpaired fins, with the ventral side of the body flashing bright blue and the dorsal side turning dark. Both fish swam in a circular fashion, elevating the skin folds. The male followed the female nudging her abdomen with his snout. Both fish turned upward, and released gametes. The eggs are spherical, 0.53–0.73 mm in diameter, demersal, adhesive, transparent, and pale yellowish orange in color, and contain a cross-shaped or asteroid cluster of oil globules. The egg membrane was thick and consisted of about 14 concentric layers. The incubation period ranged from 73.5 hours at 28.2–28.5°C to 145.0 hours at 22.1–22.4°C. The newly hatched larvae were 1.38–1.98 mm in total length (TL) with 84-11-13 = 19–21 myomeres. The yolk was absorbed when the larvae attained 1.49–2.22 mm TL, three days after hatching. The larvae were fed on oyster larvae, blue mussel larvae, sea-urchin larvae and rotifers, but all of them died in 16 days. During the embryonic and early larval stages, the only pigment cells that appeared on the body were the black chromatophores.

The neurotoxic effects of monocrotophos on the formation of the serotonergic nervous system and swimming activity in the larvae of the sea urchin Hemicentrotus pulcherrimus

The neurotoxicity of monocrotophos (MCP) in the development of the serotonergic nervous system and swimming activity of larvae of the sea urchin, Hemicentrotus pulcherrimus, was examined. Lethal dose 50% of MCP was 43 μg/ml. Overall morphology was not affected in larvae that received up to 30 μg/ml of MCP soon after fertilization until the 53 h post-fertilization pluteus stage. However, while 70 ± 0.6% of larvae in 5 μg/ml MCP swam actively, the proportion decreased to 30 ± 1.7% in 30 μg/ml MCP. Accordingly, immunoblotting indicated that MCP decreased the relative intensity of immunoreaction of serotonin receptor protein. Whole-mount immunohistochemistry indicated that MCP inhibited serotonergic axon growth, reduced the number of serotonergic cells at the apical ganglion, and perturbed formation of the serotonin receptor cell network. The present study demonstrated that sea urchin larva is a useful model for evaluating the working mechanism of environmental toxicants in neurogenesis and behavior.

Light influences feeding and growth of echinoplutei

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 404:69-78 (2010) - DOI: https://doi.org/10.3354/meps08488 Light influences feeding and growth of echinoplutei L. Milonas1, B. Pernet2, B. L. Bingham1,* 1Department of Environmental Sciences, Western Washington University, Bellingham, Washington 98225, USA 2Department of Biological Sciences, California State University, Long Beach, Long Beach, California 90840, USA *Corresponding author. Email: brian.bingham@wwu.edu ABSTRACT: Because planktonic invertebrate larvae may be food-limited, anything that increases feeding and digestive efficiency should increase the chances of larval survival to metamorphosis. As light directly enhances both feeding and digestion in some planktonic heterotrophic protists, we hypothesize that similar processes might occur in the larvae of marine invertebrates. We studied the direct effects of light on feeding and development in sea urchin larvae (Strongylocentrotus droebachiensis, S. franciscanus and sand dollar Dendraster excentricus). Larvae were placed in 12:12 h light:dark cycles or in complete darkness and ingestion rates were measured. We monitored larval morphology during the first 2 to 3 wk of development and tested for light-related differences. Short-term changes in light regime had no effect on feeding rates. However, larvae of all 3 species showed longer-term diel feeding patterns with ingestion rates generally higher during daylight hours. These patterns persisted in S. franciscanus larvae even when larvae were held in complete darkness for 3 d. Larvae of D. excentricus exposed to natural light cycles developed longer arms usually associated with food limitation; those held in darkness had significantly shorter arms. The developing juvenile structures (i.e., rudiments) of S. droebachiensis larvae exposed to light were significantly smaller than those of larvae held in continuous darkness, suggesting that light may have negative effects on larval growth and development. Measuring the effects of light on feeding and growth may clarify the behaviors of invertebrate larvae during their critically important planktonic period. KEY WORDS: Light effects · Larval feeding · Larval growth · Larval morphology Full text in pdf format PreviousNextCite this article as: Milonas L, Pernet B, Bingham BL (2010) Light influences feeding and growth of echinoplutei. Mar Ecol Prog Ser 404:69-78. https://doi.org/10.3354/meps08488 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 404. Online publication date: April 08, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Extrinsic and intrinsic factors affecting the metamorphic rate of Tripneustes gratilla (Echinodermata: Echinoidea)

Experiments were conducted to determine the effects of water conditioned with Sargassum (i.e. fresh and ground Sargassum and excreta of Sargassum-fed Tripneustes gratilla) — as well as the effects of adult sea urchins (i.e. Salmacis sphaeroides and T. gratilla), larval age and parentage — on the settlement and metamorphic rate of full-sibling batches of T. gratilla larvae. The majority of larvae (35 to 57 d old) settled within the first hour of the assays, but significantly more settled and metamorphosed completely in the conditioned water treatments than in the control (boiled filtered seawater). Completely metamorphosed larvae in the control treatment indicate that specific cues are not necessary to induce settlement and metamorphosis of competent larvae. However, habitat cues enhanced metamorphic rate significantly. Complete metamorphosis occurred earlier in Sargassum treatments, and the number of completely metamorphosed larvae was significantly higher in the ground Sargassum treatment. Observations of early juvenile aggregations on Sargassum further suggest that algal metabolites may enhance benthic recruitment. The sensitivity of sea urchin larvae to waterborne cues differed among larval age groups. Older batches of larvae metamorphosed faster, particularly in the ground Sargassum treatment, while the intermediate age group also had high metamorphic rates in both sea urchin treatments. There were significant differences in metamorphic rate among full sibling batches of larvae of the same age, as well as significant interaction between batch and treatment over time. Results indicate that differences in the age of competent larvae and genetic factors affect the ability of larvae to detect cues to initiate and complete metamorphosis.

Seasonal variability in gonad development in the sea urchin (Paracentrotus lividus) on the Basque coast (Southeastern Bay of Biscay)

The main limiting factor to carrying out toxicological bioassays with sea urchin larvae is the restricted period for the availability of viable gametes. Although studies have been undertaken of the reproductive cycle of the sea urchin for several areas of the Bay of Biscay, only limited information exists for the southeasternmost area (the Basque coast). Furthermore, this geographical zone presents some particular environmental conditions, e.g., relatively warm waters. In this study, the gonad state of a population of Paracentrotus lividus, settled on the rocky shores of the city of Donostia-San Sebastian have been monitored. These sea urchins are observed to behave like a typical Atlantic population, with generally high gonad indices and a single yearly main spawning period, between April and May. Further, females show a shorter spawning period than males, becoming the limiting organisms for the availability of larvae.

Effect of supercritical and aqueous-alcoholic extracts from Halocynthia Aurantium on gametes, zygotes, and embryos of sea urchin

The influence of supercritical (SC) and aqueous-alcoholic extracts of Halocynthia Aurantium (Ascidiaceae, Tunicata) on gametes, embryos, and larvae of sea urchin Strongylocentrotus intermedius was studied. It was demonstrated that aqueous-alcoholic extract produce no appreciable effect on embryos and larvae of sea urchin. When supercritical extract is added at the stage of gamete fusion, fission is not affected, but gastrulation process changes, producing exogastrulae. In addition, the development of infusoria was suppressed in the presence of supercritical extract. The distinctions in the biological activity of aqueous-alcoholic and SC-CO2 extracts of Halocynthia Aurantium tunic are evidently associated not with the lipid fraction but with the fractions of peptides and secondary metabolites, since the lipid fractions were virtually identical.