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Relatively well-preserved echinoids from Palaeozoic strata are exceptionally rare fossils. New fossil finds can thus have an important impact on our understanding of the morphology, phylogenetic relationships and history of diversification of early sea urchins. The Devonian strata of Germany have long been known to contain echinoids, predominantly through the relatively abundant record of disarticulated plates and spines. In contrast, only select articulated or semi-articulated specimens are recorded. We herein describe new specimens from the Middle and Late Devonian belonging to two Palaeozoic echinoid taxa, Rhenechinus hopstaetteri and Lepidocentrus eifelianus. These specimens are amongst the most-complete known for these two taxa, and provide novel insight into their morphology and stratigraphic range. Additionally, the record of Rhenechinus is the youngest occurrence of an echinocystitid echinoid in the fossil record, indicating that this family ranged from the Silurian (Aeronian or Telychian) to at least the Middle Devonian (Givetian), prior to going extinct. The morphological details provided by the new specimen of L. eifelianus highlights similarities between this species and other Devonian echinoids known from elsewhere in Europe and North America, and suggest that the lepidocentrids were widely dispersed and abundant during the Devonian. [ABSTRACT FROM AUTHOR]

It is essential to understand the spatial distribution of a target species for effective stock management, particularly in the case of less mobile rock-dwelling species such as sea urchins. However, sea urchins exhibit an aggregated distribution within fishing grounds, thereby necessitating diving surveys at multiple sites to elucidate their spatial distribution at a fine scale. In Mikuni, Sakai City, Fukui Prefecture, Japan, female divers are well-acquainted with the underwater landscape and can determine the sea urchin catch per fishing ground. They also conduct voluntary fishery management for the sea urchin. Therefore, we enlisted female divers to report the sea urchin Hemicentrotus pulcherrimus catch during the 2020–2022 period and subsequently visualized the spatial distribution of these catches and estimated initial abundance using the Leslie method according to the fishing ground. The catch per unit effort did not decrease although the cumulative catch increased in many fishing grounds. This was because divers sensibly perceived the status of sea urchin stocks at each fishing ground through the dive fishery and they voluntarily controlled their fishing efforts to prevent stock depletion. Our results highlight that the catch data are often used for stock estimation but are influenced by fishermen's management of the fishery. [ABSTRACT FROM AUTHOR]

Gametogenesis and the accumulation of nutrients such as proteins progress in sea urchin gonads during their growth. In vertebrate species, these physiological mechanisms are regulated by nuclear receptors. Although it has been estimated that there are several dozen nuclear receptor homologs in the genome of the purple sea urchin Strongylocentrotus purpuratus their functions and which ones are expressed in the gonads remain unclear. Here, we investigated the expression of nuclear receptor genes in early gametogenesis and the dynamics of their expression during germ cell formation in the northern sea urchin Mesocentrotus nudus. First, we identified the vasa sequence in M. nudus, and quantitative PCR of vasa and histological analysis revealed that germline cells were undergoing proliferation and differentiation in the growing gonads. During this period, 23 nuclear receptor genes were expressed in the male and female gonads. The expression levels of five nuclear receptor genes (eip78c, trβ, bar, rxrγ, and ftz-f1β) were found to be increased during gonadal growth in both sexes, suggesting that these nuclear receptors exert certain functions during the growth period of the gonads. Our results provide the first comprehensive experimental data on nuclear receptors for a species of sea urchin. [ABSTRACT FROM AUTHOR]

The effect of a fraction of phlorethol (CcPh), one of the polyphenolic compounds isolated from the brown alga Costaria costata (Turn.) Saund (Laminariales), on gametes and embryogenesis of the sea urchin Strongylocentrotus intermedius (A. Agassiz, 1864) was studied. Using a model of developing sea urchin embryos, it was shown that phlorethol at concentrations of ≤700 μg/mL did not exert a cytotoxic effect on early developmental stages (from the zygote to the 16-celled stage blastomere). The embryotoxic effect of phlorethol that caused the death of 50% of the embryos was expressed in a concentration (I) range of 50 < I ≤ 100 μg/mL only after 24 h of incubation, in the blastula stage. When exposed to concentrations greater than 100 μg/mL, embryos that survived to the blastula stage did not develop further and died after 36 h of incubation. Under the effect of phlorethol, the fertilizing capacity of sea urchin spermatozoa and oocytes decreased. The concentration of phlorethol that inhibited fertilization by 50% (IC50) when acting on sperm was 1.28 ± 0.38 μg/mL and when acting on oocytes was 3.83 ± 0.82 μg/mL. Thus, phlorethol reduces the fertilizing capacity of sea urchin gametes at concentrations much lower than embryotoxic concentrations and can potentially find practical application as part of new contraceptive drugs for mammals and humans. [ABSTRACT FROM AUTHOR]

Background: Echinometra mathaei (family Echinometridae), is one of the sea urchins widely distributed on the Egyptian coasts in the Red Sea. This organism contains edible and non-edible parts. The present study was carried out to analyze and identify the metabolites present in the non-edible parts (Aristotle's lantern and viscera) using LC/MS. Also, the cytotoxic activity on Vero cell line and antiviral activity against herpes simplex virus type 1 were evaluated using MTT colorimetric assay. Results: Chemical profiling of the crude extracts of Aristotle's lantern and viscera using LC/MS indicated the presence of 51 and 59 compounds, respectively. The main metabolites present in both non-edible parts were phospholipids, amino acids, peptides, fatty acids and glycerol derivatives. However, the characteristic difference was the presence of carotenoid pigments only in viscera. The crude extract of Aristotle's lantern and viscera showed no cytotoxic activity on Vero cell line and significant antiviral activity against herpes simplex virus with an IC50 value equal to 115.48 ± 1.20 and 122.4 ± 0.50 µg/mL, respectively. Conclusions: In the present study, the crude extracts of the non-edible parts of E. mathaei were analyzed using LC.MS.MS.QTOF and indicated the existence of 110 chemical compounds, with significant antiviral activity against HSV-1 and no cytotoxic activity. The diversity of the identified compounds with two main categories of compounds, phospholipids and peptides, may contribute to the antiviral activity of Aristotle's lantern and viscera. Additionally, this research focused on clarification of nutritive, pharmaceutical and economic values of these parts. As future prospects, further studies are required to isolate the metabolites and assess the detailed mechanism of antiviral activity via in vitro, in vivo and in silico studies. [ABSTRACT FROM AUTHOR]

The sea urchin Tripneustes gratilla holds substantial ecological and economic importance in tropical marine ecosystems. To better understand the population structure and genetic diversity of T. gratilla, here we developed a suite of 29 polymorphic microsatellite makers based on high-throughput sequencing. The range of alleles characterized by these primers varied from 6 to 19, with an average number of 12.31. The observed and expected heterozygosities ranged from 0.250 to 1.000 and from 0.808 to 0.955, respectively. All the polymorphism information content values of the 29 loci were above 0.5, suggestive of highly informative. Demonstrating adherence to Hardy–Weinberg equilibrium, these 29 primer pairs present robust candidates for conducting population genetics and phylogeographic analyses in T. gratilla, which may provide valuable information for sustainable management and conservation efforts of this urchin. [ABSTRACT FROM AUTHOR]

Kelp forests have deteriorated globally due to anthropogenic stressors. There is an urgent need to extend baselines, to understand the processes that underlie the persistence and recovery of kelp forests, and to distinguish the normal range of ecosystem variability from more extreme changes. Using a mixed-method, historical ecology approach, we integrate archival data, oral histories, and contemporary ecological data to examine the dynamics of kelp forests over a multi-decadal to multi-century time-period in central California. We focus on sea otters, sunflower seastars, sea urchins, kelp cover, kelp species dynamics, and climate. From 1826 to 2020, kelp was highly variable. There were seven periods of low kelp cover and two periods of exceptionally low kelp cover (1897–1899; 2014–2016) following El Niño-Southern Oscillations (ENSOs). Exceptionally low kelp cover did not occur when two predators—seastars and sea otters—were both present. In all cases, kelp recovered following times of extremely low cover, with a lag, which was extended by the duration of warm water anomalies (ENSO Recovery Lag). Kelp remained low for approximately 2 years following 80% of ENSOs. The greatest kelp decline (12-fold) was in Santa Cruz (northern Monterey Bay). Herbivore populations (sea urchins) were highly variable over the past century and exhibited short- and long-term changes in abundance. Sunflower seastars were present in low, stable abundances prior to seastar wasting disease (1938–2013, mean density = 0.02/m2) when they declined by 97.5%. Insights from this reconstruction indicate that kelp recovery following extended warm water anomalies exhibits a lag and occurs over multiple years. [ABSTRACT FROM AUTHOR]

Alterations in seawater chemistry posed by acidification may lead to immunological and antioxidant defence impairment in sea urchins, with differences among local populations. Here, we analyzed the effects of reduced pH on Paracentrotus lividus, with a multibiomarker approach, and the possible intraspecific variations in sea urchin responses. Two groups of animals with different ecological histories (i.e., the pattern of environmental characteristics and pressures experienced throughout the organism's lifetime) were maintained at ambient pH and pH reduced of 0.4 units for 8 months. Changes in gonadosomatic index (GSI), immunological, and oxidative stress biomarkers were assessed in coelomic fluid, gonads, and digestive tract. Animals maintained at reduced pH showed limited impact of seawater acidification compared to the ambient pH condition. However, sea urchins from the two sites were differently influenced by the seawater pH (as shown by multivariate analyses). GSI and immunological and antioxidant status were differentially modulated between the two sexes, with generally higher values in females, but differences between sexes in relation to the pH of exposure were limited. Overall, our findings highlight that the impact of environmental stressors may differ in sea urchins from different locations. This has implications for the maintenance of P. lividus wild populations under future global change scenarios. [ABSTRACT FROM AUTHOR]

It is crucial to understand the role of temperature in rearing sea urchin larvae for large-scale production of sea urchin seeds. The development of purple sea urchins, Heliocidaris crassispina, such as fertilization, hatching, embryonic development, larval growth, ingestion, metabolism, and metamorphosis, was investigated at four temperatures: 20, 24, 28, and 32 °C. In the four temperatures, fertilization and hatching of sea urchins first increased with temperature and then decreased. The optimal condition was found at a temperature of 28 °C, where the fertilization and hatching rates exceeded 90%, and embryonic development was highly synchronized. This condition did not differ from the results observed at a temperature of 24 °C (P > 0.05). The fertilization and hatching rates were lower at 20 °C and 32 °C, among which 32 °C had the fastest embryo development but the second highest mortality. In contrast, 20 °C had the slowest embryo development and the most increased mortality. The optimal growth temperature for larvae is 28 °C, at which their growth and development rate are the fastest. However, at 24 °C, it is the second highest. At 20 °C, the growth rate is the lowest, with sluggish physiological responses and the lowest digestion and metabolism capacity. The metamorphosis rate did not differ between 28 and 32 °C (P < 0.05), with 50.0% and 61.1%, respectively, while remaining below 4% at 20 °C. This indicates that temperature significantly impacts the early development of Heliocidaris crassispina sea urchins, whose larvae may be sensitive to low temperatures but have higher temperature tolerance. [ABSTRACT FROM AUTHOR]

Basket height and stocking density are crucial and related factors for successful commercial sea urchin aquaculture, but these factors have not been definitively determined for production of Tripneustes gratilla. This study investigated the effects of varying basket heights (deep 30 cm vs. shallow 15 cm) and stocking densities (4, 6 and 8 kg.m−2 or 13, 19 and 24% coverage of available basket surface area) on aquacultural production of T. gratilla. Contrary to previous suggestions, reduced consumption was identified as the cause of decreased production in deeper baskets. Consumption was significantly higher in shallow baskets than deep baskets for both the fresh seaweed, Ulva lacinulata, (W = 38, p = 0.026) and formulated feed (W = 76.5, p = 0.007). Consequently, baskets of approximately 15 cm deep are recommended to enhance production of T. gratilla and possibly other urchin species. Two subsequent trials assessed production of T. gratilla at different stocking densities. Trial 1 aimed to maximize urchin size over a three-month grow-out period using fresh U. lacinulata, while trial 2 focused on enhancing gonad production over two months using formulated feed. Although greater stocking density significantly reduced the specific growth rates of individual urchin mass in both trials (p < 0.044), there was no significant impact on mortality, net production or gonad size and quality. The variations in growth rates were attributed to spine loss resulting from negative behavioural interactions (F2, 9 = 9.551; p = 0.005). Based on the objectives of both grow-out and gonad-enhancement phases, we recommend a stocking density of approximately 20% coverage. [ABSTRACT FROM AUTHOR]

Understanding early life histories of keystone marine herbivores can broaden insight into population dynamics and ecosystem functioning. Settlement, defined as the transitional process from planktonic larva to benthic juvenile, is not well understood for the long-spined sea urchin Diadema antillarum despite outsized herbivory effects on Caribbean coral reefs. Recent advances in aquaculture methods have enabled experimental investigation of larval ontogeny and cue-mediated settlement dynamics otherwise difficult to understand through field observations. In this study, the morphological attributes preceding metamorphosis of feeding larvae were characterized and factors influencing development of these attributes were examined. Simple access to the nutritious microalgae Rhodomonas lens led to metamorphic competence, defined here by presence of a large rudiment, or imaginal disc, and either internal or external podia with suction rings at the terminal tips. Subsequent exposure to a suite of individual cues revealed highest settlement to two calcareous algae, Halimeda sp. and crustose coralline algae, at 58.0% (± 3.7 SE) and 46.0% (± 5.1 SE), respectively, and zero settlement to a sterile seawater negative control. Significantly higher settlement to a ceramic tile overgrown with biofilm compared to separate sterile tile and isolated biofilm treatments revealed a synergistic relationship between a structural and biochemical cue. Microalgae exposure further enhanced settlement, but only when a strongly inductive primary cue was present. Together, these results provide insight into active habitat selection and factors likely influencing D. antillarum recruitment potential. Findings can be applied to improve both population dynamics models and aquaculture production methods. [ABSTRACT FROM AUTHOR]

The green seaweed Ulva is close to becoming popular due to its suitability as potential feedstock production and for food items. However, there is a general lack of studies on the aversion or acceptability of this alga by marine organisms, particularly on its role as a chemoattractant and/or phagostimulant activity. Here we tested the effect of Ulva compressa and other biochemicals as potential chemostimulating compounds for a valuable sea urchin species, Paracentrotus lividus, selected as model species for our tests. Sea urchins' chemical sensitivity was estimated by analysing movements of spines, pedicellariae, tube feet, and individual locomotion using an innovative bioassay. Our results showed that all forms of Ulva (fresh, defrosted, and fragmented) resulted in an effective stimulus, evoking in sea urchins strong responses with robust activation of spines and tube feet, where the defrosted one was the most stimulating. Among the amino acids tested, glycine, alanine, and glutamine produced a significant response, highlighting for the latter a concentration–response relationship. Sea urchins responded to glucose, not to fructose and sucrose. Spirulina resulted as the most effective stimulus, acting in a dose-dependent manner. Major results indicate the role of Ulva as a chemostimulant and strongly attractant for such herbivore species. From an applied point of view, the presence of potential Ulva's feed-related compounds, acting as chemoattractants (to reduce food searching time) and/or feeding stimulants (to stimulate ingestion), would improve the several applications of Ulva in the formulation of the feeds for sustainable aquaculture. [ABSTRACT FROM AUTHOR]

Most reported Diadema antillarum restocking has resulted in low survival and retention. These outcomes challenge conservation and restoration goals. A manipulative study was conducted to evaluate site retention, tandem coral-urchin restoration, and herbivory from 200 adult D. antillarum translocated to five experimental plots off Key Biscayne, Florida. Two additional plots were monitored as controls. Surveys revealed homogeneous dispersal over time, with overall retention of 94.5%, 79.5%, 56.0% and 22.5% at 1-, 7-, 84- and 267-days post-release, respectively. Rugosity significantly predicted urchin retention and plots with higher relief exhibited reduced emigration rates. Benthic image analysis revealed a significant decline in macroalgae relative to controls when urchin densities were above 0.15 m−2 but not at 0.04 m−2. Urchin plots experienced a 27% reduction in macroalgae from days 7 to 84. Results indicated higher long-term retention, especially within plots with greater relief, and evidence for ecologically significant herbivory following a single translocation event. [ABSTRACT FROM AUTHOR]

Slow or nonexistent natural recovery of the Caribbean long-spined sea urchin (Diadema antillarum) following a mass mortality event in 1983–1984 has prompted interest in hatchery-origin production and restocking to aid coral-reef restoration. A critical first step is the ability to propagate D. antillarum from gametes, at scale. However, a unique larval biology and difficult and lengthy culture period of ~ 40 days has resulted in inconsistent success over the past 20-plus years. The purpose of this study was to develop protocols for rearing D. antillarum within a novel 1800-L recirculating aquaculture system capable of scaled production. Five separate experiments investigated larval development in response to diet quantity, diet composition, and initial stocking density within 40-L replicate culture tanks. The initial experiment was used to develop a microalgae reference diet consisting of Tisochrysis lutea and Chaetoceros sp. and revealed similar growth and survival between high quantity (40.0 × 103 cells mL−1) and low quantity (10.0 × 103 cells mL−1) treatments at 21 days post-fertilization (DPF). Experiments 2–4 examined diet quality by comparing carbon-equivalent microalgae compositions. Mixed diets containing Rhodomonas lens outperformed the reference diet in multiple experiments and a tripartite diet containing all three species resulted in significantly higher survival at 42 DPF. The highest growth overall occurred from a monoalgal R. lens diet, which indicated that this species is critically important. Further observations of density-dependent growth dynamics revealed that initial stocking densities > 1 larvae mL−1 significantly reduced growth over 28 DPF. Data generated were used to establish fundamental larviculture protocols that have since led to the production of over 1000 juveniles. [ABSTRACT FROM AUTHOR]

Rapid industrialization in the State of Kuwait caused unprecedented pollution in the marine environment over the recent years. Studies on the effect of mercury (Hg) was least evidenced when compared to other trace metals in Echinometra mathaei, sea urchin collected from the Al-Fintas (Site-A) and Mina Abduallah (Site-B), Southern Kuwait. Reasons were attributed to (a) seasonal restriction of sea urchin abundance, (b) their low mercury concentrations in the Coastal waters (c) analytical imperfection and sensitivity of the instrumentation. In this study, the instrumental lacunae were overcome by using direct mercury analyzer (DMA-80, Milestone, Italy) which yielded consistent and reproducible Hg concentrations in all the samples. In nature, high Hg concentrations were observed in the seawater at 23 °C > 15 °C > 12 °C irrespective of the sites although the total mean Hg concentration was high in Site-A over Site-B. The 96 h and 180 d exposed E. mathaei to LC50 toxicity, and bioaccumulation tests revealed high Hg concentrations in E. mathaei in relation to differential temperature in the sequence of 15 °C > 23 °C > 12 °C with minimal fluctuation of the hydrological parameters. Season-wise analysis showed high Hg concentrations in both the seawater and sea urchin body parts during the winter seasons compared to the summer season and irrespective of the two sites. Thus, this study recommends possible Hg mitigation that affects the socioeconomic condition of the marine resources besides, labeling the sea urchin as a bio-monitoring tool to Hg pollution. [ABSTRACT FROM AUTHOR]

The effects of three relevant organic pollutants: chlorpyrifos (CPF), a widely used insecticide, triphenyl phosphate (TPHP), employed as flame retardant and as plastic additive, and bisphenol A (BPA), used primarily as plastic additive, on sea urchin (Paracentrotus lividus) larvae, were investigated. Experiments consisted of exposing sea urchin fertilized eggs throughout their development to the 4-arm pluteus larval stage. The antioxidant enzymes glutathione reductase (GR) and catalase (CAT), the phase II detoxification enzyme glutathione S-transferase (GST), and the neurotransmitter catabolism enzyme acetylcholinesterase (AChE) were assessed in combination with responses at the individual level (larval growth). CPF was the most toxic compound with 10 and 50% effective concentrations (EC10 and EC50) values of 60 and 279 μg/l (0.17 and 0.80 μM), followed by TPHP with EC10 and EC50 values of 224 and 1213 μg/l (0.68 and 3.7 μM), and by BPA with EC10 and EC50 values of 885 and 1549 μg/l (3.9 and 6.8 μM). The toxicity of the three compounds was attributed to oxidative stress, to the modulation of the AChE response, and/or to the reduction of the detoxification efficacy. Increasing trends in CAT activity were observed for BPA and, to a lower extent, for CPF. GR activity showed a bell-shaped response in larvae exposed to CPF, whereas BPA caused an increasing trend in GR. GST also displayed a bell-shaped response to CPF exposure and a decreasing trend was observed for TPHP. An inhibition pattern in AChE activity was observed at increasing BPA concentrations. A potential role of the GST in the metabolism of CPF was proposed, but not for TPHP or BPA, and a significant increase of AChE activity associated with oxidative stress was observed in TPHP-exposed larvae. Among the biochemical responses, the GR activity was found to be a reliable biomarker of exposure for sea urchin early-life stages, providing a first sign of damage. These results show that the integration of responses at the biochemical level with fitness-related responses (e.g., growth) may help to improve knowledge about the impact of toxic substances on marine ecosystems. [ABSTRACT FROM AUTHOR]

Sea urchins are keystone herbivores in many marine benthic habitats and can significantly influence coral-algae phase shifts and reef carbonate budgets. Hall Bank Reef in Western Australia is a unique high latitude reef with high hermatypic coral cover but lacking macroalgae and soft corals. Since the reef status is thought to result from grazing of the urchin Centrostephanus tenuispinus, this study was focused on evaluating bio-erosion by C. tenuispinus with respect to size structure and seasonality. Monthly samples of urchins were collected during 2014–2016 and gut composition was analysed. Gut evacuation rates were calculated using urchins dissected at time intervals up to 96 h. Reworked CaCO3 was calculated using caged urchins in a nearby seagrass bed. Mean percentages of organic, CaCO3, and siliceous components in C. tenuispinus gut contents were 86.3 ± 3.2, 10.3 ± 2.8, and 3.4 ± 1.5%, respectively. Gut evacuation rates for autumn, winter, spring, and summer were 0.70, 0.24, 0.48, and 0.72 day −1. Bio-erosion rates were significantly higher in summer (3.5 g CaCO3 m−2 day−1) than in winter (1.3 g CaCO3 m−2 day−1) and higher rates recorded for large urchins. Urchin bio-erosion was 1 kg CaCO3 m−2 annum−1. Variation in food ingestion rates in response to seawater temperature changes was found to be the main driver for differences in seasonal bio-erosion rates, which likely contribute to the absence of macroalgae and the maintenance of high coral cover on Hall Bank Reef. This study provides baseline data on bio-erosion by a sea urchin at Hall Bank Reef, which will be essential in monitoring and managing reefs in this region, especially under current trends in climate change. [ABSTRACT FROM AUTHOR]

In sea urchin hatcheries that produce seeds for the Strongylocentrotus intermedius stock enhancement program, promoting broodstock maturation is advantageous for early gamete collection and the resultant increase in seed size when they are released on fishery grounds. Here, the effects of photoperiod control were investigated to develop a method for promoting gonadal maturation. Adult sea urchins collected from the southwestern coast of Hokkaido in the Sea of Japan were reared from December to August or November under an ambient photoperiod and three accelerated photoperiods that shortened the annual change in day length between the two winter solstices to 8, 6, or 4 months. Maturation progress was evaluated by histological observations and spawning reaction tests, which involved observing gamete release from the gonopore after removing the coelomic fluid. The sea urchins reared under any of the accelerated photoperiods matured in June or July, 2–3 months earlier than those reared under the ambient photoperiod. The eggs and sperm collected from the photoperiod-treated sea urchins were fertilizable and grew normally into juveniles through metamorphosis. Therefore, accelerated photoperiods are effective for promoting maturation and early gamete collection in S. intermedius. [ABSTRACT FROM AUTHOR]

Accumulation of yolk precursor protein in the oviparous egg is essential for embryo growth. Transferrin-like protein, also known as major yolk protein, is a major precursor protein in sea urchins and sea cucumbers. In sea urchins, a new yolk protein was recently detected in Strongylocentrotus intermedius and Mesocentrotus nudus eggs. This protein, tentatively named yolk-related protein (YRP), was thought to have important physiological functions for sea urchin gonadal growth and gametogenesis. To understand the relationship between YRP and vitellogenesis, we investigated the molecular structure of sea urchin YRP, quantified the transcript levels during oogenesis, and identified the presence of YRP in coelomic fluid. Using molecular cloning, we characterized one cDNA that encoded YRP (mn-yrp). Structural analysis revealed that mn-YRP is an apolipoprotein B (ApoB)-like protein that belongs to the large lipid transfer protein superfamily. Quantification of mn-yrp (mn-apob) transcripts showed that mn-apob is mainly expressed in the stomach during gonadal growth. Immunobiochemical methods using antiserum revealed that mn-ApoB was present in the coelomic fluid. These results indicate that ApoB has a role in the transport of nutrients, such as sugar, lipids, and carotenoids, from the digestive tract to eggs via coelomic fluid in sea urchin. [ABSTRACT FROM AUTHOR]

We propose an expansion of neuroecological comparisons to include the capabilities of brainless and non-neural organisms. We begin this enterprise by conducting a systematic search for studies on learning in echinoderms. Echinodermata are marine invertebrates comprising starfish, brittle stars, sea cucumbers, sea urchins, and sea lilies. Animals in this phylum lack any centralized brain and instead possess diffuse neural networks known as nerve nets. The learning abilities of these animals are of particular interest as, within the bilaterian clade, they are close evolutionary neighbors to chordates, a phylum whose members exhibit complex feats in learning and contain highly specialized brains. The learning capacities and limitations of echinoderms can inform the evolution of nervous systems and learning in Bilateria. We find evidence of both non-associative and associative learning (in the form of classical conditioning) in echinoderms, which was primarily focused on starfish. Additional evidence of learning is documented in brittle stars, sand dollars, and sea urchins. We then discuss the evolutionary significance of learning capabilities without a brain, the presence of embodied cognition across multiple groups, and compare the learning present in echinoderms with the impressive cognitive abilities documented in the oldest linage group within vertebrates (the major group within the phylum of chordates), fish. [ABSTRACT FROM AUTHOR]

To examine the effects of the crab Charybdis japonica (72–96 mm in carapace width) on the grazing behavior of the sea urchin Mesocentrotus nudus, cage experiments were conducted in a sea urchin-dominated barren ground and in land-based tanks. In the field, one crab consumed almost all 10 sea urchins (20–40 mm in test diameter: TD) given in an unescapable small-mesh cage within 4–15 days. In a coarse-mesh cage experiment where smaller sea urchins (< 31 mm in TD) could pass through the mesh, a crab prevented intrusion and grazing on kelp blades (100 g per cage), while 4–50 sea urchins intruded and grazed on kelp blades in the control cage (no crabs inside). In the laboratory, different-sized coarse-mesh cage experiments showed that one crab could repel sea urchins and protect kelp blades even in the largest cage (6 m2). Furthermore, a year-round feeding experiment (14 months) revealed that three crabs consumed sea urchins from May to December (> 12 °C in water temperature), and that predation rates varied among the crabs, ranging from 1653 to 4777 g (124 to 312 sea urchins) per crab per year. These results suggest the importance of C. japonica in the control of grazing by M. nudus. [ABSTRACT FROM AUTHOR]

In the present study, sea urchin Sterechinus neumayeri tissues were used for the passive biomonitoring of toxic and trace elements at the Comandante Ferraz Station, Antarctica and compared to a pristine region (Botany). As, Ba, Br, Ca, Co, Cr, Fe, K, Na, Rb, Sc, Se and Zn concentrations were determined by instrumental neutron activation analysis (INAA), while toxic metals (Cd, Hg, Ni and Pb), and Cu were determined by atomic absorption spectrometry (GF-AAS). The findings were compared to other organisms commonly applied for biomonitoring purposes and to the sediment concentrations of each sampling region. Urchins from the Ferraz Station area presented higher Br, Co, Cr, Cs, K, Se and Zn levels than the pristine location. The results obtained herein suggest S. neumayeri can be applied to the biomonitoring of Cr and Zn. The present study also contributes to knowledge of the mineral composition of the sea urchin S. neumayeri. [ABSTRACT FROM AUTHOR]

The effects of polyphenolic impurities on the biological activity of fucoidan samples from the brown alga Fucus distichus subsp. evanescens were studied using the model of developing embryos of the sea urchin Strongylocentrotus intermedius. The embryotoxic action of fucophloretol from F. evanescens (IC50 = 96.90 ± 12.20 μmol/L) and cucumarioside A7 (a triterpene glycoside) from Cucumaria frondosa subsp. japonica (IC50 = 0.39 ± 0.01 μmol/L) was assessed. The ability of fucoidans with different levels of polyphenolic impurities to partially or completely reduce the embryotoxic action of cucumarioside A7 from C. japonica has been shown. [ABSTRACT FROM AUTHOR]

The main objective of this study was to describe the reproductive cycle of the sea urchin Paracentrotus lividus (Lamarck, 1816) on the south Atlantic coast of Morocco. In this study, we selected three sites in the Agadir region: Sidi R'bat, Cap Ghir, and Anza to study from March 2018 to February 2019 some aspects of reproduction in this species through sex-ratio, the histological identification of the stages of sexual maturity, their monthly evolution, the evolution of the gonad index, as well as the size at first sexual maturity. The results show that at the three study sites, the sex-ratio is unbalanced in favor of females. The histology of the gonads revealed six different stages: recovering, growing, premature, mature, partly spawned, and spent. The gonadal cycle is synchronous for both sexes; histological examination confirmed the presence of spawning (March–October) in three sites. A perfect correlation observed between the gonad index, and the histological results suggest that the gonad index decreases when the individual is spawning. Temperature and photoperiod are important factors controlling the reproduction cycle. The beginning of spawning in the three sites coincides with the increase in temperature and photoperiod, which may act as environmental triggers. On the other hand, the size at first sexual maturity was ranged between 30 and 40 mm, and the values of L50 of females are higher than L50 of males signifying that males reach sexual maturity before females. [ABSTRACT FROM AUTHOR]

Association of the idoteid isopod, Synidotea variegata Collinge 1917 with the echinoid sea urchin, Stomopneustes variolaris Lamarck, 1816 is reported for the first time from the rocky subtidal region of Vizhinjam coast, southwestern India. Isopods infested the spines and peristome of sea urchins and the intensity of infection increased with the increasing test diameter of the host. [ABSTRACT FROM AUTHOR]

Two undescribed polyoxygenated furanocembranoid derivatives, methyl 15-(9-hydroxy-8-methoxy-2,12-dimethyl-15-oxa-bicyclo[10.2.1]pentadeca-2,4,6,11-tetraen-3-yl)propanoate (salmacembrane A) and 1-(16-methyl-2,16-dihydrofuran)-8-methoxy-12-methyl-20-oxabicyclo[10.2.1]pentadeca-2,4,6,11-tetraen-9-ol (salmacembrane B), were isolated from the organic extract of sea urchin Salmacis bicolor (family Temnopleuridae) by extensive chromatographic purification. Their structures were elucidated using detailed spectroscopic evidence. Salmacembrane A displayed significantly greater attenuation property against pro-inflammatory cyclooxygenase-2 (IC50 1.71 mM) than that exhibited by salmacembrane B (IC50 1.99 mM). Salmacembrane A could potentially inhibit 5-lipoxygenase (IC50 1.87 mM) and its activity was significantly greater than that exhibited by anti-inflammatory agent ibuprofen (IC50 4.50 mM, p < 0.05). The greater selectivity index (anti-cyclooxygense-2/anti-cyclooxygense-1) of salmacembrane A (1.06) than ibuprofen (0.43) further supported higher selectivity toward pro-inflammatory isoenzyme cyclooxygenase-2. Salmacembrane A displayed higher antioxidant properties against 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl (IC50 1.57 and 1.65 mM, respectively) than those exhibited by salmacembrane B (IC50 > 1.85 mM). In addition, these antioxidant activities were comparable to the standard α-tocopherol (IC50 DPPH 1.51 mM, IC50 ABTS+ 1.70 mM p < 0.05). The higher electronic parameters obtained from structure–activity relationship analysis along with greater binding affinities of salmacembrane A at the active site of cyclooxygenase-2 ascribed its potential anti-inflammatory activity. [ABSTRACT FROM AUTHOR]

The annual kelp Saccharina japonica grows along the northeastern coast of Japan, making the coast highly productive for the fishery for herbivores such as sea urchins and abalones. The biomass of the kelp along this coast drastically varies each year due to variable environmental factors, i.e., seawater temperature and nutrient concentrations, during the period of kelp germination. We carried out a field investigation to elucidate how the gonad production fluctuates in an environment where the kelp production varies each year. Seaweed biomass and gonad weight of the sea urchin Mesocentrotus nudus were examined monthly from March 2015 through December 2018. The kelp was abundant and the gonad index (= gonad ∕ body weight × 100) of the sea urchins reached more than 20% in 2015. However, in the following 3 years (2016 to 2018), the kelp was nearly absent from the area and the maximum gonad index was significantly less than that in the kelp-abundant year (2015). During the kelp-scarce 3 years, the gonad index showed a significant decrease from one kelp-scarce year to another, indicating that the effect of a poor algal growth on the gonad production of sea urchins was cumulative over the following years. [ABSTRACT FROM AUTHOR]

Early sea urchin embryos are sensitive to agonists and antagonists of transmitter receptors, both metabotropic and channel ones. In this work, we studied mechanisms of the cytostatic action of cyproheptadine and haloperidol–antagonists of serotonin 5HT2 receptors and dopamine D2 receptors, respectively. For this purpose, we employed the model of the blockade of the first cleavage division in sea urchin, which allows quantifying the effects of embryotoxic substances. The action of haloperidol and cyproheptadine is mediated by the effects on cytoskeleton elements. Both antagonists caused an increase in the degree of polymerization of the actin cytoskeleton, both in the cortical layer and in the cytoplasm. In addition, both antagonists affected the tubulin cytoskeleton: haloperidol predominantly disturbed spatial organization of the mitotic spindle, while cyproheptadine caused a complete depolymerization of tubulin and arrest of mitotic processes. The results indicate that cytostatic effects of dopamine and serotonin antagonists on cleavage divisions of sea urchin embryos are mediated by similar and/or crosstalk molecular mechanisms but also have significant differences that require further research. [ABSTRACT FROM AUTHOR]

Strong physical disturbance from hurricanes can disrupt coral reef ecosystems and precipitate a regime shift toward algal dominance, particularly in the absence of grazing pressure to regulate algal growth post-storm. Here, we examine the influence of Hurricane Irma on a keystone grazer, Diadema antillarum, and the surrounding coral reef benthic community in the Florida Keys. D. antillarum densities and test diameters, as well as percent cover of coral reef benthic groups, were measured at 10 sites in the middle and upper Keys before and after Irma. Significant decreases in mean D. antillarum density and median test diameter were observed following the storm. There was a correlation between the magnitude of decline in D. antillarum density and the magnitude of sediment deposition on reefs, suggesting that abrasion or burial from sediment transport may have contributed to D. antillarum mortality. We detected significant decreases in the percent cover of sponges and hydrocorals following the storm, but no change in scleractinian coral cover, which was very low (3% mean cover) at the onset of the study. Macroalgal cover increased at sites in the upper Keys and decreased at sites in the middle Keys. There was no relationship between post-storm D. antillarum density and the change in percent cover of macroalgae or turf-algal-sediment matrix (TAS), likely due to low overall abundance of the grazer. We predict that coral reefs will remain in an algal-dominated ecosystem state due to, among other factors, increasing frequency of strong hurricanes that impact the D. antillarum population. [ABSTRACT FROM AUTHOR]

The assessment of the gametogenic cycle and gonadal stage in commercial species relevant for shellfisheries and aquaculture is essential for the optimal management of the resource. However, currently this assessment frequently relies on the subjective classification of the specimens into discrete stages of development, with a strong dependence on the observer. The present study developed a quantitative, continuous, and observer-independent method for the analysis of the gonadal stage of the edible sea urchin, Paracentrotus lividus. This new approach takes advantage of image analysis to assess in histological preparations of the gonads the cellular growth of germ cells and calculate a Pixelar index (PI). The PI can be calculated taking into account just the proportion of the area covered by germinal vs somatic cells in the gonad follicle (PI1) or computing also the empty space created in the follicle lumen after spawning (PI2), which reduces the variability of the index. In both cases, PI showed a bell-shaped dependence on the traditional gametogenic stage that could be fitted to a Gaussian model, providing a tool that can be used for the quantitative evaluation of effects on sea urchin gonads of any kind of environmental factors, from aquaculture rearing conditions to ecotoxicological effects of pollutants on wild stocks. Further assessment of intraindividual—both among gonads and within gonads—variability in this index will be necessary for refinement of this quantitative tool. [ABSTRACT FROM AUTHOR]

Previous study has shown that feeding fresh Saccharina japonica kelp at the late sporophyte stage to Mesocentrotus nudus from a barren can improve the gonad quality of the sea urchin. In particular, the basal frond portion of S. japonica, which accumulates amino acids during maturation, greatly enhances the sweet and umami taste of the gonads. In the kelp Undaria pinnatifida, resources are accumulated in the blade for growth, then translocated to the sporophyll for maturation at the late sporophyte stage. In this study, we demonstrate the effects of feeding U. pinnatifida sporophyll to M. nudus from a barren from May to July on gonad quality (size, color (L*a*b*), and taste (free amino acids)) compared with the effects of feeding the U. pinnatifida midrib (negative control) and the basal frond portion of S. japonica (positive control). Feeding M. nudus the U. pinnatifida sporophyll, which has high protein, carbohydrate, and total and free alanine contents, improved M. nudus gonad size and color and increased alanine content and decreased arginine content in the gonad, similar to the results of feeding M. nudus the basal frond portion of S. japonica. The sporophyll increased free glutamic acid and decreased bitter-tasting amino acid contents in the gonads of sea urchins, indicating that feeding of the sporophyll improved the gonad taste more than feeding of the basal frond portion of S. japonica. This study first indicated that the sporophyll of U. pinnatifida is a high potential feed to improve gonad taste of M. nudus. The appropriate feeding period in which gonad quality can be improved must be confirmed in order to shorten the duration of M. nudus culture. [ABSTRACT FROM AUTHOR]

Gonad quality (color, texture, and taste) of adult Mesocentrotus nudus from a barren can be improved by feeding with the kelp Saccharina japonica. Fronds of cultivated S. japonica accumulate resources from May or June as they form zoospores (maturation). In this study, the effect of feeding cultivated S. japonica at the late sporophyte stage (May–July) on the gonad quality of M. nudus from a barren and cultured in cages suspended offshore in Shizugawa Bay, Miyagi Prefecture, Japan, was investigated. At the end of the culture period, gonad indices, hardness, color (L*, a*, b*), free amino acid (FAA) content in the gonads, the consistency of these traits among individuals, and sensory scores of the cultured sea urchins (CE) were compared to those of a natural population from a barren (BE), an Eisenia bicyclis bed (EE) (fishing ground), and urchins from the barren at the start of the culture period (BS). The CE group exhibited a higher gonad index and L* value, and lower gonad hardness and variation among individuals than those of the BS group. Sensory evaluation showed that gonad taste and overall quality of the CE group was more desirable than the EE group. The desirable taste is a result of sweetness due to a high alanine content, strong umami, and low arginine content. It is likely that increased gonad size and improved gonad quality and consistency among individuals were due to feeding the urchins with mature, nutritious S. japonica at the late sporophyte stage. Further research is required to identify the nutrient constituents of S. japonica at the late sporophyte stage that affect gonad taste. [ABSTRACT FROM AUTHOR]

The substances contained in the aqueous–ethanol and aqueous extracts from freshly collected and destroyed brown algae Saccharina cichorioides in their second vegetation season and from excrement of the sea urchins Strongylocentrotus intermedius that had been fed these algae specimens were studied for effects on the digestive enzyme 1,3-β-D-glucanase, sperm, egg cells, and developing embryos of the sea urchin. The yield, composition, and structure of substances from fresh and destroyed S. cichorioides and from sea urchin excrement were analyzed. Sea urchins assimilated mannitol, proteins, and almost completely laminarans from destroyed thalli of S. cichorioides. The detection of activators of sea urchin 1,3-β-D-glucanase in the aqueous–ethanol extracts of destroyed algae and inhibitors of fertilization processes in the extracts of fresh algae is consistent with field observations. The biochemical study has shown that the digestion and reproduction processes in S. intermedius are controlled by metabolites of S. cichorioides to a significant extent. [ABSTRACT FROM AUTHOR]

Herbivorous damselfish that cultivate algal farms frequently exhibit aggressive territorial behaviour to defend their investment from intruders, particularly against other herbivorous fish and invertebrates. On a coastal coral reef in New Caledonia, the response of the damselfish Hemiglyphidodon plagiometopon to intruders of varying type and level of threat to their algal farm was tested. Responses to live and dead coral fragments, carnivorous whelks, shells, and rocks varied from no response to biting and extrusion from farms. Damselfish elicited the strongest defensive response to the herbivorous sea urchin Echinometra mathaei, rapidly attacking the urchin by biting and lifting it from farms, before extruding it up to 3.5 m away. H. plagiometopon responded in a similar manner to dead urchins (no threat of herbivory) as to live urchins, but typically did not extrude them as far. Ultimately, damselfish responded to intruders in a manner largely consistent with the level of threat posed to their algal farm, with the similar response between live and dead urchins suggesting such strong defensive behaviours may be combination of 'hard-wired' and learned behaviours in reaction to the level of realised threat. [ABSTRACT FROM AUTHOR]

Water chlorination is the most widely used technique to avoid microbial contamination and biofouling. Adding chlorine to bromide-rich waters leads to the rapid oxidation of bromide ions and leads to the formation of brominated disinfection by-products (bromo-DBPs) that exert adverse effects on various biological models. Bromo-DBPs are regularly encountered within industrialized embayments, potentially impacting marine organisms. Of these, bromoform, tribromoacetic acid and tribromophenol are among the most prevalent. In the present study, we tested the potential toxicity and genotoxicity of these disinfection by-products, using sea urchin, Paracentrotus lividus, embryos. We highlighted that tribromophenol showed higher toxicity compared to bromoform and tribromoacetic acid. Furthermore, a synergistic effect was detected when tested in combination. Pluteus cells exposed for 1 h to mixtures of DBPs at several concentrations demonstrated significant DNA damage. Finally, when compared to a non-exposed population, sea urchins living in a bromo-DPB-polluted area produced more resistant progenies, as if they were locally adapted. This hypothesis remains to be tested in order to better understand the obvious impact of complex bromo-DBPs environments on marine wildlife. [ABSTRACT FROM AUTHOR]

Lack of recovery of the sea urchin Diadema antillarum in the Caribbean region following a widespread epizootic in 1983–1984 has garnered great interest due to the role of this species as a grazer of macroalgae that exclude reef-building corals. In the Florida Keys, USA, previous research suggests that reestablishment of D. antillarum is limited by low fertilization success and a lack of larval supply. However, the physical mechanisms determining larval supply in the Florida Keys remain poorly resolved. Here, we use coupled biological and physical oceanographic datasets of D. antillarum larval supply to settlement collectors, sea surface temperatures and heights, and the Okubo Weiss parameter to examine a link between influx of larvae to the middle Florida Keys and Tortugas Eddy activity in the Straits of Florida. The greatest magnitude of settlement over 3 months of measurements occurred from late May to late June 2015, coinciding with the passage and dissociation of a Tortugas Eddy. Settlement occurred on collectors only at offshore bank-barrier reef sites, consistent with a temperature signal of a passing eddy at these sites. No D. antillarum were observed by divers at sites 1 yr following settlement on the collectors. The results indicate that despite the lack of population recovery, D. antillarum larval influx can occur during intermittent oceanographic events. [ABSTRACT FROM AUTHOR]

Over the past five decades, transitions from kelp beds (or forests) to barrens have occurred as a result of sea urchin overgrazing along the temperate coastlines. The deterioration of mature kelp beds has been mainly observed for Laminaria, Saccharina, and Macrocystis in the order Laminariales. In northern Miyagi Prefecture, Japan, the destruction of adult Ecklonia bicyclis kelp beds by the overgrazing of Mesocentrotus nudus was observed since 2013. In this study, we analyzed the process of deterioration of an E. bicyclis bed, from the changes in morphology of the thallus, with or without urchin grazing marks and urchin attachment, from video and photographic records. The processes of deterioration followed one of two strategies. In the first strategy, sea urchins climb from the stipes to the branches under calm conditions in winter. Subsequently, the fronds and branches are grazed by these urchins, as shown by large numbers of bare stipes and holdfasts. After the disappearance of the fronds and the branches, sea urchins mainly graze above the stipe bases, as illustrated by the high percentage of stipes with grazing marks. Finally, rigid holdfasts are left on the seafloor. The kelp bed is most likely to be destroyed by this grazing strategy. In the second strategy, urchins aggregate on the holdfasts of the entire plants and graze the stipe bases, particularly in February. The stipes are severely grazed by sea urchins, and the thalli above the stipe bases fall to the seafloor. Urchins aggregated firstly graze the fronds of the detached thalli followed by the branches and the stipes. The results of this study suggest that protection of the stipes from the grazing and climbing of M. nudus would be desirable for the conservation and restoration of E. bicyclis kelp beds. [ABSTRACT FROM AUTHOR]

Metamorphosis induction cues (by chemical mediation or direct contact) were tested in Paracentrotus lividus using three different macroalgae treatments: Corallina sp., Palmaria palmata, and Laminaria digitata. Higher percentages of metamorphosis were reached in Paracentrotus lividus larvae by direct contact with a Palmaria palmata substrate. [ABSTRACT FROM AUTHOR]

Understanding the strength and type of interactions among species is vital to anticipate how ecosystems will respond to ongoing anthropogenic stressors. Here, we examine the ecological function of native (Ecklonia radiata) and invasive (Undaria pinnatifida) kelps in resisting shifts to sediment-trapping turf on reefs within the highly urbanized temperate Port Phillip Bay (PPB), Australia. Short-term (30 days) and long-term (232 days) manipulations demonstrated that kelp laminae can clear and maintain the substratum free of turfs, while conversely, removal of kelp leads to a proliferation of turfs. Analyses looking at the relationship between total length of E. radiata and U. pinnatifida and the area cleared of turf algae showed that the clearing effect of E. radiata over a year was greater than that of U. pinnatifida due to the annual die-back of the invasive. A natural experiment (608 days) identified that ongoing sea urchin (Heliocidaris erythrogramma) grazing led to native kelp bed decline, facilitating turf dominance. Even though U. pinnatifida establishes once native beds are disturbed, its ecological function in clearing turf is weaker than E. radiata, given its annual habit. In PPB, turfs represent the more persistent and problematic algal group and are likely changing the structure, function, and energy flows of shallow temperate reefs in this urbanised embayment. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons including benz[a]anthracene (BaA) are priority pollutants in the aquatic environment. Our previous study revealed that BaA and its metabolite, 4-monohydroxylated BaA (4-OHBaA) inhibit larval skeletogenesis in the sea urchin Hemicentrotus pulcherrimus. Here we report studies to elucidate the target of skeletogenesis inhibition elicited by BaA and 4-OHBaA. First, we performed an in vitro experiment using isolated micromeres which give rise to the larval skeletogenic mesenchyme. However, skeletogenesis was not repressed by BaA and 4-OHBaA, implying that these chemicals indirectly influence on the formation of larval skeleton. Next, we analyzed their influence in vivo using embryos. Vascular endothelial growth factor (VEGF) that is expressed in the ectoderm and induces spicule formation was inhibited by BaA and 4-OHBaA treatment. These chemicals also suppressed the expression of the heparan sulfate 6-O endosulfatase (Sulf) known as a VEGF signaling modulator. We, therefore, propose that BaA and 4-OHBaA effects on larval skeletogenesis via VEGF signaling. Furthermore, we showed that the expression of Endo16 mRNA, an endodermal marker, decreased after BaA and 4-OHBaA exposure, suggesting that these chemicals affect endodermal function together with skeletogenesis. This study demonstrates that BaA and 4-OHBaA exert multiple detrimental effects on the development of H. pulcherrimus. [ABSTRACT FROM AUTHOR]

Ozone depletion induced by anthropogenic gases has been increasing the transmission of solar ultraviolet-B radiation (UV-B, 280–315 nm) through the atmosphere, which may impact the fitness of marine invertebrates in intertidal and shallow waters. To our knowledge, however, the responses of fitness related behaviors to UV-B radiation at different intensities have been rarely studied in marine invertebrates. For the first time, the present study investigated the effects of exposure of one hour to UV-B radiation at different intensities on foraging behavior, Aristotle's lantern reflex and righting behavior of the sea urchin Strongylocentrotus intermedius. Exposure of one hour to UV-B radiation at 10 μW/cm2 significantly reduced foraging behavior. An intensity dependent effect of exposure to UV-B radiation was found in the duration of the Aristotle's lantern reflex. Exposure to UV-B radiation at 20 μW/cm2 for one hour significantly reduced the duration of the Aristotle's lantern reflex, but 10 μW/cm2 did not. There was no significant difference of righting response time among sea urchins exposed to 0, 10 and 20 μW/cm2 for one hour. To test potential carryover effects, the behavioral traits were re-measured three days later. We found significant carryover effects of UV-B radiation on foraging time and righting response time, but not on the duration of the Aristotle's lantern reflex. The present study indicates that a brief exposure of one hour to UV-B radiation can significantly affect the duration of Aristotle's lantern reflex, righting response time and foraging behavior of a sea urchin, although the immediate impacts and carryover effects were highly trait dependent. This study provides new information into the behavioral responses of marine invertebrates to exposure to UV-B radiation. Future studies should be carried out to investigate long-term carryover effects of UV-B radiation on behavioral and physiological fitness related traits. [ABSTRACT FROM AUTHOR]

The gonads of sea urchins (Strongylocentrotus intermedius) are characterized by high levels of arachidonic acid (ARA, 20:4n-6) and eicosapentaenoic acid (EPA, 20:5n-3). However, to our knowledge, little information is available regarding the physiological response of adult sea urchins to dietary ARA. In the present study, four dietary feeds were formulated with graded ARA (0, 0.5%, 1%, and 2% dry diet). Each diet was randomly allocated to three cages during a 56-day feeding experiment. The results showed that the sea urchin weight gain rate (WGR) and the gonadosomatic index (GI) significantly increased as ARA was equal to or above 1.0% of dry diet (P < 0.05). The activities of superoxide dismutase (SOD), catalase (CAT), and total anti-oxidative capacity (T-AOC) were the highest in the coelomic fluid of sea urchins that were fed diets with 1% ARA. The total essential amino acid (TEAA) and its ratio to total non-essential amino acid (TNEAA) showed a similar tendency to WGR and GI as dietary ARA increased, and the highest TEAA and TEAA/TNEAA were observed in the gonads of sea urchins that were fed diets with 1% ARA. Levels of ARA and ARA/EPA of the gonads increased while n-3/n-6 polyunsaturated fatty acid (PUFA) decreased with the increase of dietary ARA (P < 0.05). EPA in the gonads of experimental animals fed with formulated feeds showed no significant differences (P > 0.05), but was significantly lower than those fed with kelp (P < 0.05). These results suggested that relatively higher levels of ARA (1% dry diet) significantly promoted growth, gonad development, activities of antioxidant enzymes, as well as nutritional values (TEAA, TEAA/TNEAA, and PUFA) of adult S. intermedius. [ABSTRACT FROM AUTHOR]

The population ecology of the sand dollar Sculpsitechinus auritus was studied in shallow coastal habitats of the Gulf of Suez, Egypt, from January 2013 to October 2014. Bimonthly sampling revealed that 95 % of the individuals had a width of 100-145 mm and that juveniles were absent throughout the sampling period. The mean gonadosomatic index (GSI) reached peaks of >2 % in September 2013 and August 2014, which concurred with seasonal highs of water temperature. Declining GSI values indicated that spawning took place between October and January. Histological examination of the gonads confirmed that spawning started in October. Locomotion rate was 88.7 mm h−1 in September, which was significantly higher than 56.3 mm h−1 in December. Similarly, water temperature was significantly higher in September (26 °C) than in December (17 °C), most probably explaining locomotion differences. Organic matter and grain size fractions of the sediment were not significantly different. Maximum density of 0.68 individuals m−2 was found at 4 m depth, whereas at other depths densities were significantly lower (≤0.05 individuals m−2). The epibiotic brittle star Ophiodaphne scripta was found on >67 % of the sand dollars and its frequency was significantly higher (>1.5 per host) between September and November coinciding with the onset of S. auritus’s spawning period. [ABSTRACT FROM AUTHOR]

Sea urchins play a crucial role in the health and dynamics of reef ecosystems. Diadema mexicanum is a dominant grazer and erosive agent of the substratum in reef environments in the eastern tropical Pacific. Its reported distribution extends from the middle of the Gulf of California (26° N) to northern Peru (6°23′ S), including oceanic islands. Here, we report the occurrence of Diadema mexicanum in Isla San Jorge (31°0′38.53″ N, 113°14′34.84″ W), the northernmost island in the Gulf of California, which extends its range an additional 600 km northward. Sea urchins, ranging in test size from 4.5 to 12.4 cm, were present at 2-6 m in October 2015. This test size was one of the largest reported for this species in the eastern tropical Pacific. Spine length in sea urchins in the upper gulf ranged from 3.3 to 15.6 cm. Variation in body size of sea urchin may reflect variation in more structurally complex reefs from isolated islands that provide shelter from predation. The reef structure of Isla San Jorge is formed by high coral cover of the scleractinian coral Porites panamensis, with an average colony height of 26.27 cm (standard error, SE ±1.58, n = 60), similar to coral reef communities of the southern Gulf of California. Although D. mexicanum is considered a great force of erosion to the substratum in reef environments in the eastern tropical Pacific, no evidence of erosion was observed at Isla San Jorge, indicating a balanced dynamic between herbivores, macroalgae, and corals. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the sea urchin Lytechinus variegatus as an environmental biomonitor and contribute to the knowledge of its nutritional aspects for two regions of the northern coast of the São Paulo State, Brazil. Mass fractions were determined by instrumental neutron activation analysis. Concentrations of Ca, Cs, Cr, Fe, Rb, Sc, and Zn were higher at Praia Grande (contaminated area), while As, Br, and Se higher at Praia Preta (control). An exploratory principal component analysis indicated that Praia Grande was influenced by Cr, Cs, Fe and Zn possibly due to environmental contamination. Results indicate the possibility of applying this organism for biomonitoring purposes for metals Cr, Fe, Zn and the semimetal As. [ABSTRACT FROM AUTHOR]

Growing evidence indicates that ocean acidification has a significant impact on calcifying marine organisms. However, there is a lack of exposure risk assessments for aquatic organisms under future environmentally relevant ocean acidification scenarios. The objective of this study was to investigate the probabilistic effects of acidified seawater on the life-stage response dynamics of fertilization, larvae growth, and larvae mortality of the green sea urchin (Strongylocentrotus droebachiensis). We incorporated the regulation of primary body cavity (PBC) pH in response to seawater pH into the assessment by constructing an explicit model to assess effective life-stage response dynamics to seawater or PBC pH levels. The likelihood of exposure to ocean acidification was also evaluated by addressing the uncertainties of the risk characterization. For unsuccessful fertilization, the estimated 50% effect level of seawater acidification (EC50SW) was 0.55 ± 0.014 (mean ± SE) pH units. This life stage was more sensitive than growth inhibition and mortality, for which the EC50 values were 1.13 and 1.03 pH units, respectively. The estimated 50% effect levels of PBC pH (EC50PBC) were 0.99 ± 0.05 and 0.88 ± 0.006 pH units for growth inhibition and mortality, respectively. We also predicted the probability distributions for seawater and PBC pH levels in 2100. The level of unsuccessful fertilization had 50 and 90% probability risks of 5.07-24.51 (95% CI) and 0-6.95%, respectively. We conclude that this probabilistic risk analysis model is parsimonious enough to quantify the multiple vulnerabilities of the green sea urchin while addressing the systemic effects of ocean acidification. This study found a high potential risk of acidification affecting the fertilization of the green sea urchin, whereas there was no evidence for adverse effects on growth and mortality resulting from exposure to the predicted acidified environment. [ABSTRACT FROM AUTHOR]

The aim of the present work was to extend our knowledge on the variability of trace metals in sea urchin tissues, focusing on seasonal fluctuations (2010 February for “winter,” May for “spring,” August for “summer,” November for “autumn”) in the three different sampling sites of Algerian west coast (Oran Harbor (S1), Ain Defla (S2), and Hadjaj (belonging to Mostaganem City S3)). For this purpose, the bioavailability (metal indices) and bioaccumulation (metal concentrations in soft tissues) of heavy metals (Zn, Cu, Pb, and Cd), the physiological characteristics (e.g., biological indices such as condition index (CI), repletion index (RI), gonad index (GI)), and the biometric parameters (diameter (D) and the height (H)) of sea urchins Paracentrotus lividus were assessed and related to seasons and sites. To investigate the metal bioavailability to sea urchins more precisely, the metal indices were used as a reliable tool in the present work, instead of the metal concentrations only. The interest to standardize metal concentrations with the weight of the urchin test is to overcome the metal burden variations in the soft tissues of urchin related to the seasonal weight changes of the soft body of animal. We evidence that the most contaminated sites were S1 and S2. Furthermore, it should be noted that the bioavailability of metals, corresponding to the values of metal indices, is also more pronounced in S1 and S2 compared to that measured in S3. Thus, a correlation is observed between seasonal metal content in urchin tissues from the three sites and the corresponding metal indices. The high metal concentrations were obtained during the period when RI and CI were highest. So, it appears that the bioaccumulation of metals in sea urchins of the three sites studied is significantly influenced by the reproductive cycle and diet, feeding activity, and physiological state of these organisms. We noticed that the sea urchins from the sites S1 and S2 were small in size. It is probable that these animals, whose internal tissues contained high concentrations of metals, have been exposed to metal pollution, which might have affected both their growth and altered their physiological capacity. This approach is very original and might be used in the monitoring of the quality of coastal waters, and the present work provided a useful data set for Mediterranean monitoring network. [ABSTRACT FROM AUTHOR]

In the present study, we examined the localization of the major yolk protein (MYP) in the intestine of the sea urchin Strongylocentrotus intermedius. First, partial MYP complementary DNA was isolated from the sea urchin intestine. The expression level of MYP messenger RNA (mRNA) along the sea urchin digestive tract is highest in the intestine, so we performed in situ hybridization and immunohistochemical analysis using this tissue. No MYP mRNA was detected in the luminal epithelium, connective tissue, muscle tissue, or coelomic epithelium by in situ hybridization analysis. Positive immunohistochemical staining was observed in the luminal epithelium, inner epithelium and connective tissue, the signal being strongest in the latter. We conclude that MYP synthesized in the inner epithelial cells is moved to and stored in connective tissue and the luminal epithelium, before being secreted into the body cavity and the inner digestive cavity of the sea urchin. [ABSTRACT FROM AUTHOR]

In order to improve the efficiency of stock enhancement programs for the sea urchin Hemicentrotus pulcherrimus, information on food algal species, which affect growth and gonad production greatly, is necessary. Since it is difficult to identify species from the macroalgal fragments within the gut contents of the sea urchin by microscopic observation, we tried to apply a DNA barcoding method for gut contents analysis. We used a partial rbcL gene sequence for taxonomic section and newly designed primer sets, respectively, for brown algae and for red algae. Direct sequencing of the PCR products was carried out. Species identification was based on the phylogenetic relationship. We could objectively identify four species and two taxonomic groups (genus or family) in brown algae, and two species and four taxonomic groups in red algae from the gut contents. Sargassum hemiphyllum was the most abundant brown alga in the gut contents but was not dominant in the study site. The result showed the importance of identification to the species level. In addition, red algal epiphytes were detected with brown algal fragments. The DNA barcoding method will enable the researchers to verify the important role of epiphytes as a potential food source. [ABSTRACT FROM AUTHOR]

Food shortage of kelp Saccharina japonica is one of the most serious concerns for aquaculture of juvenile Strongylocentrotus intermedius in summer. For the first time, the present study provides a cost-effective approach to addressing this problem for field aquaculture. We found juvenile S. intermedius fed gulfweed Sargassum horneri (group S) had significantly higher food consumption and better growth than those fed S. japonica (group K). S. intermedius fed S. horneri and S. japonica (group M) showed significantly larger test diameter, test weight, body weight, and higher specific growth rate than those fed S. japonica only (group K), but not significantly larger or higher than those fed S. horneri only (group S). Further, gonad weight and index were significantly smaller in the group S than in the groups K and M, which indicates that S. horneri is not only a better diet for aquaculture of juvenile sea urchins S. intermedius, but leads a suitable energy allocation for cultured juvenile S. intermedius in summer. According to the present study, full replacement of S. japonica with S. horneri and the feeding regime of S. horneri and S. japonica are both acceptable for juvenile S. intermedius aquaculture in summer. Therefore, we suggest aqua-farmers choose suitable replacement according to the local availability and cost of S. horneri and S. japonica in summer. [ABSTRACT FROM AUTHOR]