Strongylocentrotus Purpuratus Research Articles

Light-Dependent Electrical Activity in Sea Urchin Tube Feet Cells.

Sea urchins can detect and respond to light, and many species of sea urchins are negatively phototaxic. Light detection is hypothesized to occur via photoreceptors located on sea urchin tube feet, and opsins have been detected in tube feet, spines, and the test. However, the molecular mechanisms underlying light detection are, for the most part, unknown. Individual tube feet disc cells were isolated from purple sea urchins (Strongylocentrotus purpuratus), and the electrical responses of these cells to varying levels of illumination were quantified using the patch clamp technique. No currents were observed under bright illumination, whereas under dark conditions, large, slowly activating currents were consistently observed. Two types of cells were functionally identified based on their responses to darkness. Type I cells sustained currents indefinitely in the dark, whereas Type II cell currents spontaneously decayed after several seconds. The large currents observed were composed of the summation of many smaller events that were characterized by a rapid onset and an exponentially decaying component, which may be indicative of direct vesicular release from the tube feet disc cells in response to the dark conditions.

The Purple Sea Urchin Strongylocentrotus purpuratus Demonstrates a Compartmentalization of Gut Bacterial Microbiota, Predictive Functional Attributes, and Taxonomic Co-Occurrence.

The sea urchin Strongylocentrotus purpuratus (order Camarodonta, family Strongylocentrotidae) can be found dominating low intertidal pool biomass on the southern coast of Oregon, USA. In this case study, three adult sea urchins were collected from their shared intertidal pool, and the bacteriome of their pharynx, gut tissue, and gut digesta, including their tide pool water and algae, was determined using targeted high-throughput sequencing (HTS) of the 16S rRNA genes and bioinformatics tools. Overall, the gut tissue demonstrated Arcobacter and Sulfurimonas (Epsilonproteobacteria) to be abundant, whereas the gut digesta was dominated by Psychromonas (Gammaproteobacteria), Propionigenium (Fusobacteria), and Flavobacteriales (Bacteroidetes). Alpha and beta diversity analyses indicated low species richness and distinct microbial communities comprising the gut tissue and digesta, while the pharynx tissue had higher richness, more closely resembling the water microbiota. Predicted functional profiles showed Kyoto Encyclopedia of Genes and Genomes (KEGG) Level-2 categories of energy metabolism, membrane transport, cell motility, and signal transduction in the gut tissue, and the gut digesta represented amino acid, carbohydrate, vitamin and cofactor metabolisms, and replication and repair. Co-occurrence network analysis showed the potential relationships and key taxa, such as the highly abundant Arcobacter and Propionigenium, influencing population patterns and taxonomic organization between the gut tissue and digesta. These results demonstrate a trend of microbial community integration, allocation, predicted metabolic roles, and taxonomic co-occurrence patterns in the S. purpuratus gut ecosystem.

Mifepristone affects fertility and development in the sea urchin Paracentrotus lividus

Drugs such as oral contraceptives and hormone replacement therapies are known to find their way into rivers, lakes and seas, and have the potential to affect reproduction and development of the wildlife. The knowledge of the reproductive mechanisms and their regulation in aquatic species is of fundamental importance for predicting and preventing the damage by the increasing release of such chemicals in the environment. Mifepristone, a synthetic steroid used as a drug for chemical abortion, works by blocking the effects of progesterone. Its presence in fresh and salt water has been reported, representing a danger for aquatic species. In this frame, we evaluated in both acute and chronic exposures, the effects of mifepristone on the reproductive performance of the sea urchin P. lividus. In both acute and chronic exposures, mifepristone did not affect the histological structure of the gonads. However, mifepristone administered to females caused the decrease of the percentage of normal developed plutei larvae compared with the control, whereas it did not alter sperm motility parameters and fertilization success in males. The immunohistological localization of progesterone receptor-like immunoreactivity on the plasma membrane of oocytes and ova and the molecular weight of a progesterone receptor-like immunoband identified by western blotting, are in agreement with a membrane progesterone receptor deducted from the genome sequence of the sea urchin Strongylocentrotus purpuratus and suggest that in P. lividus mifepristone actions may be mediated by a progesterone receptor.

A species distribution model for Paracentrotus lividus: predicted projections of habitat suitability

A species distribution model for Paracentrotus lividus: predicted projections of habitat suitability

Effects of ocean warming on larvae development of Patella tenuis crenata in the Canary Islands

Effects of ocean warming on larvae development of Patella tenuis crenata in the Canary Islands

Methods for collection, handling, and analysis of sea urchin coelomocytes.

Sea urchin coelomocytes can be collected in large numbers from adult sea urchins of the species, Strongylocentrotus purpuratus, which typically has 12-40mL of coelomic fluid. Coelomocytes are used for analysis of immune reactions and immune gene expression in addition to basic functions of cells, in particular for understanding structure and modifications of the cytoskeleton in phagocytes. The methods described here include coelomocyte isolation, blocking the clotting reaction, establishing and maintaining primary cultures, separation of different types of coelomocytes into fractions, processing live coelomocytes for light microscopy, fixation and staining for light and electron microscopy, analysis of coelomocyte populations by flow cytometry, and sorting single cells for more detailed follow-up analyses including transcriptomics or genomic characteristics. These methods are provided to make working with coelomocytes accessible to researchers who are unfamiliar with these cells and perhaps to aid others who have worked extensively with invertebrate cells.

Microinjection methods for sea urchin eggs and blastomeres.

Methods for microinjection into sea urchin eggs have become relatively easier because of the technical improvements by a number of researchers in the past decades. However, the size and the characteristics, such as the elasticity and toughness, of the eggs and embryos differ in species, so that we still need to modify the details of methods to adapt to each target. In this section, I list microinjection methods for three species: Hemicentrotus pulcherrimus, which has relatively tough eggs, Temnopleurus reevesii, which has slightly weak eggs, and Strongylocentrotus purpuratus, which is the most used species in sea urchin biology. In addition, I describe the methods for co-injection of morpholino anti-sense oligonucleotides and mRNAs, as well as the method for microinjection into blastomeres.

East to West: Population genòmics and hierarchical analyses reveal differential adaptation footprints in the edible sea urchin Paracentrotus lividus

East to West: Population genòmics and hierarchical analyses reveal differential adaptation footprints in the edible sea urchin Paracentrotus lividus

The painted sea urchin, Lytechinus pictus, as a genetically-enabled developmental model.

Although sea urchins are one of the oldest and most widely used marine model systems, few species have been routinely kept in culture through multiple generations. The workhorse of the field is the purple urchin Strongylocentrotus purpuratus. However, one disadvantage of S. purpuratus is its long generation time, making it impractical as a model for generating and maintaining transgenic lines. In an effort to develop a sea urchin that is suitable for transgenerational experiments and the generation of transgenic lines, we have focused on development of updated culturing methods and genomic resources for the painted sea urchin, Lytechinus pictus. Compared to S. purpuratus, L. pictus have relatively large eggs, develop into optically clear embryos, and the smaller adults can become gravid in under a year. Fifty years ago, Hinegardner developed culturing methods for raising L. pictus through metamorphosis. Here, we provide an updated protocol for establishing and maintaining L. pictus in the laboratory, and describe a new genome resource for this urchin. In our hands, L. pictus reach the 4-armed pluteus stage at 4 days; become competent to metamorphosis at 24 days; and are gravid by 6 months. Plutei and juveniles are fed on a diet of algae and diatoms, and adults are fed on kelp. We also make available a L. pictus transcriptome generated from developmental stages (eggs to 2-day-old plutei) to support the annotation of our genome sequencing project, and to enhance the utility of this species for molecular studies and transgenesis.

Conserved regulatory state expression controlled by divergent developmental gene regulatory networks in echinoids.

Evolution of the animal body plan is driven by changes in developmental gene regulatory networks (GRNs), but how networks change to control novel developmental phenotypes remains, in most cases, unresolved. Here, we address GRN evolution by comparing the endomesoderm GRN in two echinoid sea urchins, Strongylocentrotus purpuratus and Eucidaris tribuloides, with at least 268 million years of independent evolution. We first analyzed the expression of twelve transcription factors and signaling molecules of the S. purpuratus GRN in E. tribuloides embryos, showing that orthologous regulatory genes are expressed in corresponding endomesodermal cell fates in the two species. However, perturbation of regulatory genes revealed that important regulatory circuits of the S. purpuratus GRN are significantly different in E. tribuloides For example, mesodermal Delta/Notch signaling controls exclusion of alternative cell fates in E. tribuloides but controls mesoderm induction and activation of a positive feedback circuit in S. purpuratus These results indicate that the architecture of the sea urchin endomesoderm GRN evolved by extensive gain and loss of regulatory interactions between a conserved set of regulatory factors that control endomesodermal cell fate specification.

Spatio-temporal patterns based on demographic and genetic diversity of the purple sea urchin Paracentrotus lividus in the area around Corsica (Mediterranean Sea)

Sea urchins were harvested for decades in many areas throughout its distribution range, potentially leading to population collapse. In France, the purple sea urchin Paracentrotus lividus is intensively harvested. Yet, the demography and population dynamics remained under-documented, particularly in Corsica. In this context, we have characterized the fluctuations in density of several size classes at 8 sites around the island, and assessed the genetic diversity and structuring of the population. Densities recorded lie between 0 and 2.18 (± 0.41) individuals.m-2 and spatio-temporal variabilities have also been highlighted. The study of the influence of vegetation cover on the size classes suggests that small- and medium- sized individuals prefer substrates of intermediate heights, whereas individuals with a diameter ≥ 5 cm are more often observed on encrusting substrates, and may be responsible for the continuation of this type of benthic community. The genetic study indicates a high genetic diversity with a low genetic structuring. The Ne values obtained are similar to those described in previous papers. Due to estimates of local contemporary Ne and the homogeneous genetic diversity, our data tend to show that the Corsican population of P. lividus is not overexploited.

Physiology of growth in typical and transversus echinopluteus larvae

AbstractMarine invertebrate larvae are diverse in size and shape. Understanding the functional differences among these larvae and their ecological consequences is critical for understanding the evolution of larval forms and predicting responses to varying environmental conditions. This study compared the growth physiology of two morphologically distinct feeding larvae of echinoid echinoderms: the typical echinopluteus of Strongylocentrotus purpuratus, and the less well‐known echinopluteus transversus larva of Centrostephanus coronatus. Larvae of both types were reared at 16°C with 20,000 algal cells/ml of food. Despite striking differences in morphology (with late larvae of the two species bearing eight or two arms, respectively), ciliary band length grew at similar rates in both types of larvae. Significant differences between larval types were observed in growth in midline body length and stomach size. Physiologically, the typical echinopluteus larvae of S. purpuratus exhibited higher rates of protein growth, daily ingestion of algae, and aerobic respiration than did the echinopluteus transversus larvae of C. coronatus. The relationships between ingestion rate and ciliary band length or stomach size differed as well, with ingestion rate in larvae of S. purpuratus increasing much more rapidly than that of larvae in C. coronatus in relation to both morphological features. The higher physiological rates in S. purpuratus were not at the expense of increased physiological efficiency: larvae of S. purpuratus had digestive and growth efficiencies that were up to threefold higher than those in larvae of C. coronatus. Taken together, these results demonstrate fundamental differences in performance that go beyond the readily observable differences in morphology of these two larval forms. The reduced physiological capacity and growth efficiency of transversus larvae of C. coronatus provide a physiological basis for their long planktonic duration and possible teleplanktonic dispersal capabilities. The high physiological capacity and efficiency of the typical larvae of S. purpuratus may be adaptive for growing in areas of high seasonal algal abundance.

Neuropeptidergic Systems in Pluteus Larvae of the Sea Urchin Strongylocentrotus purpuratus: Neurochemical Complexity in a "Simple" Nervous System.

The nervous system of the free-living planktonic larvae of sea urchins is relatively “simple,” but sufficiently complex to enable sensing of the environment and control of swimming and feeding behaviors. At the pluteus stage of development, the nervous system comprises a central ganglion of serotonergic neurons located in the apical organ and sensory and motor neurons associated with the ciliary band and the gut. Neuropeptides are key mediators of neuronal signaling in nervous systems but currently little is known about neuropeptidergic systems in sea urchin larvae. Analysis of the genome sequence of the sea urchin Strongylocentrotus purpuratus has enabled the identification of 38 genes encoding neuropeptide precursors (NP) in this species. Here we characterize for the first time the expression of nine of these NP genes in S. purpuratus larvae, providing a basis for a functional understanding of the neurochemical organization of the larval nervous system. In order to accomplish this we used single and double in situ hybridization, coupled with immunohistochemistry, to investigate NP gene expression in comparison with known markers (e.g., the neurotransmitter serotonin). Several sub-populations of cells that express one or more NP genes were identified, which are located in the apica organ, at the base of the arms, around the mouth, in the ciliary band and in the mid- and fore-gut. Furthermore, high levels of cell proliferation were observed in neurogenic territories, consistent with an increase in the number of neuropeptidergic cells at late larval stages. This study has revealed that the sea urchin larval nervous system is far more complex at a neurochemical level than was previously known. Our NP gene expression map provides the basis for future work, aimed at understanding the role of diverse neuropeptides in control of various aspects of embryonic and larval behavior.

From genome to anatomy: The architecture and evolution of the skeletogenic gene regulatory network of sea urchins and other echinoderms.

The skeletogenic gene regulatory network (GRN) of sea urchins and other echinoderms is one of the most intensively studied transcriptional networks in any developing organism. As such, it serves as a preeminent model of GRN architecture and evolution. This review summarizes our current understanding of this developmental network. We describe in detail the most comprehensive model of the skeletogenic GRN, one developed for the euechinoid sea urchin Strongylocentrotus purpuratus, including its initial deployment by maternal inputs, its elaboration and stabilization through regulatory gene interactions, and its control of downstream effector genes that directly drive skeletal morphogenesis. We highlight recent comparative studies that have leveraged the euechinoid GRN model to examine the evolution of skeletogenic programs in diverse echinoderms, studies that have revealed both conserved and divergent features of skeletogenesis within the phylum. Last, we summarize the major insights that have emerged from analysis of the structure and evolution of the echinoderm skeletogenic GRN and identify key, unresolved questions as a guide for future work.

Secrets of the Sea Urchin Spicule Revealed: Protein Cooperativity Is Responsible for ACC Transformation, Intracrystalline Incorporation, and Guided Mineral Particle Assembly in Biocomposite Material Formation.

The formation of the sea urchin spicule involves the stabilization and transformation of amorphous calcium carbonate (ACC) and assembly of ACC nanoparticle precursors into a mesoscale single crystal of fracture-resistant calcite. This process of particle assembly or attachment is under the control of a family of proteins known as the spicule matrix [Strongylocentrotus purpuratus (SpSM)] proteome. Recently, two members of this proteome, SpSM50 and the glycoprotein SpSM30B/C-G (in recombinant forms), were found to interact together via SpSM30B/C-G oligosaccharide–SpSM50 protein interactions to form hybrid protein hydrogels with unique physical properties. In this study, we investigate the mineralization properties of this hybrid hydrogel alongside the hydrogels formed by SpSM50 and SpSM30B/C-G individually. We find that the SpSM50 + SpSM30B/C-G hybrid hydrogel is synergistic with regard to surface modifications and intracrystalline inclusions of existing calcite crystals, the inhibition of ACC formation, and the kinetic destabilization of ACC to form a crystalline phase. Most importantly, the hybrid hydrogel phase assembles and organizes mineral particles into discrete clusters or domains within in vitro mineralization environments. Thus, the interactions of SpSM50 and SpSM30B/C-G, mediated by carbohydrate–protein binding, reflect the need for protein cooperativity for the ACC-to-crystalline transformation, intracrystalline void formation, and guided mineral particle assembly processes that are instrumental in spicule formation.

Onset of feeding in juvenile sea urchins and its relation to nutrient signalling

ABSTRACTThe purple sea urchin, Strongylocentrotus purpuratus, has been the focus of extensive ecological and developmental research over the years. Strongylocentrotus purpuratus larvae transition into the juvenile stage after an extensive planktonic period. The metamorphic transition is characterized by dramatic changes in morphology and physiology of the juvenile compared to the larval form and mechanisms underlying this process, especially the early days post-settlement, remain poorly understood. We used SEM and phalloidin stain analysis as well as whole mount in situ hybridization to gain a detailed understanding of juvenile development in relation to nutrient signalling [insulin-like growth factor (IIS), FoxO (forkhead box, sub-group ‘O’) and TOR (target of rampamycin), also known as IIS/TOR/FoxO signalling]. Our results show that the majority of juvenile feeding features are fully developed only after 8-days of juvenile development, leaving an extensive period of nutritional stress. We found that FoxO gene expression increases during that time period and is localized in juvenile tube feet, potentially associated with sensory structures involved in nutrient signalling. Our data complement existing work on sea urchin juvenile development and shed new light on the perimetamorphic period of Strongylocentrotus purpuratus, with respect to nutrient signalling and the potential stressful pre-feeding period of juvenile sea urchins.

Short-term variation of abundance of the purple sea urchin, Paracentrotus lividus (Lamarck, 1816), subject to harvesting in northern Portugal

Paracentrotus lividus is a common and intensely harvested sea urchin at several European locations, including the Mediterranean Sea and the Atlantic coast of the Iberian Peninsula. The increasing human pressure on this resource due to the growing demand and market value of sea urchin gonads as seafood raises concerns on the ecological sustainability of present fisheries, which are showing a technological improvement and an expansion towards previously non-harvested areas. We examined the abundance of P. lividus of both commercial and non-commercial size before, during and after the harvesting season (from October to April) in the rocky shallow subtidal habitat along the northern Portuguese coast. The abundance of commercial (≥50 mm in test diameter) P. lividus individuals increased in the harvesting season, but drastically dropped by about 90% in the after-harvesting period. Such a pattern was consistent among three rocky shores spanning about 65 km of coast. The multivariate population structure and most size classes of non-commercial sea urchins did not differ depending on the period. The only exception was Class 4 (test diameter between 30 and 40 mm), which was more abundant in the harvesting than in the before- and, further, the after-harvesting period, but only at one shore. Very small (Class 1, test diameter below 10 mm) urchins were never found. The present findings suggest that human harvesting may cause considerable reductions in the abundance of target P. lividus, but that such an effect would not be evident concomitantly with harvesting, but in the subsequent period. Even if just under a precautionary principle, protection strategies focused on sea urchin populations and the harvesting period are advisable to contribute to maintain a sustainable local fishery of P. lividus populations that are likely to be negatively affected also by other natural and anthropogenic perturbations.

Metallothionein cDNA Cloning and Metallothionein Expression in Sea Cucumber (Apostichopus japonicus, Slenka) from the WeiHai Coast of China

The aims of this work were (1) the identification of the metallothionein (MT) gene cDNA sequence in Apostichopus japonicus and (2) the quantification of MT mRNA expression in the intestine, body wall and respiratory tree of A. japonicas after exposure to cadmium or zinc. Using RT-PCR and RACE-PCR, we cloned the MT complete cDNA sequence of A. japonicus using the RNA extracted from Cadmium-exposed intestines. The 1351 bp MT cDNA consisted of a 126 bp 5’ untranslated region, a 1069 bp 3’ untranslated region, and a 156 bp open reading frame coding for 51 amino acids, including 16 cysteines. The MT sequence of A. japonicus was 47% identical to the sequence of MT from Strongylocentrotus purpuratus. Through real-time quantitative PCR analysis, we found that the MT expression levels were significantly higher when the specimens were exposed to heavy metals, and the response to combined metal ions exposure occurred earlier than that for single metal ion exposure. Additionally, the induction of MT transcription was more responsive to zinc and can be envisaged as a potential biomarker for zinc contamination.

Obtaining hydroxyapatite from the exoskeleton and spines of the purple sea urchin Strongylocentrotus purpuratus

AbstractWe present a simple, quick, and viable way to produce hydroxyapatite (HA) from a waste by‐product of the sea food industry, this was achieved by submitting the exoskeleton of the purple sea urchin Strongylocentrotus purpuratus through a chemical reaction with H3PO4 at 3 different times (3, 18, and 36 hours) with constant stirring at 35‐40°C. The characterization of the materials was made by several techniques (FTIR, XRD, SEM‐EDS, and TEM).The FTIR results confirmed the presence of the HA characteristic functional groups OH, PO4, and CO3, the XRD characterization showed that the synthesis of calcium phosphates such as brushite and HA was achieved by confirming the presence of its characteristic peaks, also the EDS analysis confirmed the expected HA Ca/P atomic ratio of 1.67. This work shows that we can take advantage from raw materials derived from processing sea food by giving it an added value for the biomedical industry.

Antioxidant peptides derived from the hydrolyzate of purple sea urchin (Strongylocentrotus nudus) gonad alleviate oxidative stress in Caenorhabditis elegans

The papain hydrolyzate prepared from purple sea urchin (Strongylocentrotus nudus) gonad exerts significant antioxidant activity. Through ultrafiltration, gel filtration and high performance liquid chromatography, the active fractions from the hydrolyzate were screened by alleviating paraquat-induced oxidative stress in Caenorhabditis elegans, and the peptide components were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Two antioxidant peptides SnP7 (AAVPSGASTGIYEALELR, 1805.03 Da) and SnP10 (NPLLEAFGNAK, 1173.34 Da) exhibit significant antioxidant capacity, which reduce reactive oxygen species (ROS) level and the expression of superoxide dismutase-3 (SOD-3) and heat shock protein-16.2 (HSP-16.2) in oxidation-damaged nematodes. Further studies indicated that SnP7 and SnP10 induce DAF-16 nuclear translocation and the expression of stress-related genes such as sod-3. RNA interference (RNAi) suggested that peptide-induced enhancement of resistance is dependent on DAF-16. Taken together, S. nudus antioxidant peptides might act through activate DAF-16 signaling pathway, and induce the expression of DAF-16 target genes that enhance antioxidant potential of organisms.