Strongylocentrotus Purpuratus Research Articles

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.

Thyroid Hormones Accelerate Initiation of Skeletogenesis via MAPK (ERK1/2) in Larval Sea Urchins (Strongylocentrotus purpuratus).

Thyroid hormones are important regulators of development and metabolism in animals. Their function via genomic and non-genomic actions is well-established in vertebrate species but remains largely elusive among invertebrates. Previous work suggests that thyroid hormones, principally 3,5,3′,5′-Tetraiodo-L-thyronine (T4), regulate development to metamorphosis in sea urchins. Here we show that thyroid hormones, including T4, 3,5,3′-triiodo-l-thyronine (T3), and 3,5-Diiodothyronine (T2) accelerate initiation of skeletogenesis in sea urchin gastrulae and pluteus larvae of the sea urchin Strongylocentrotus purpuratus, as measured by skeletal spicule formation. Fluorescently conjugated hormones show T4 binding to primary mesenchyme cells in sea urchin gastrulae. Furthermore, our investigation of TH mediated skeletogenesis shows that Ets1, a transcription factor controlling initiation of skeletogenesis, is a target of activated (phosphorylated) mitogen-activated protein kinase [MAPK; extracellular signal-regulated kinase 1/2 (ERK1/2)]. As well, we show that PD98059, an inhibitor of ERK1/2 MAPK signaling, prevents the T4 mediated acceleration of skeletogenesis and upregulation of Ets1. In contrast, SB203580, an inhibitor of p38 MAPK signaling, did not inhibit the effect of T4. Immunohistochemistry revealed that T4 causes phosphorylation of ERK1/2 in presumptive primary mesenchyme cells and the basal membrane of epithelial cells in the gastrula. Pre-incubation of sea urchin gastrulae with RGD peptide, a competitive inhibitor of TH binding to integrins, inhibited the effect of T4 on skeletogenesis. Together, these experiments provide evidence that T4 acts via a MAPK- (ERK1/2) mediated integrin membrane receptor to accelerate skeletogenesis in sea urchin mesenchyme cells. These findings shed light, for the first time, on a putative non-genomic pathway of TH action in a non-chordate deuterostome and help elucidate the evolutionary history of TH signaling in animals.

Barrens of gold: gonad conditioning of an overabundant sea urchin

AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 10:345-361 (2018) - DOI: https://doi.org/10.3354/aei00274 Barrens of gold: gonad conditioning of an overabundant sea urchin Cassandra G. Pert1,2,*, Stephen E. Swearer2, Symon Dworjanyn3, Nina Kriegisch4, Giovanni M. Turchini5, David S. Francis5, Tim Dempster1 1Sustainable Aquaculture Laboratory - Temperate and Tropical (SALTT), Department of Biosciences, University of Melbourne, Victoria 3010, Australia 2National Centre for Coasts and Climate (NCCC), School of Biosciences, University of Melbourne, Victoria 3010, Australia 3National Marine Science Centre, Southern Cross University, Coffs Harbour, New South Wales 2450, Australia 4Institute for Marine & Antarctic Studies, University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia 5School of Life and Environmental Sciences, Deakin University, Geelong, Victoria 3220, Australia *Corresponding author: pertcg@gmail.com ABSTRACT: Overgrazing by the overabundant native purple urchin Heliocidaris erythrogramma has caused kelp-dominated reefs to shift to urchin barrens throughout southeastern Australia. These areas are characterised by low kelp abundance, low biodiversity and high urchin densities. As purple urchin gonads are a delicacy in many countries, commercial harvest from barrens could aid kelp recovery. However, the lack of macroalgae in these habitats, driven by high urchin densities, results in urchins with small, poor-quality roe that is commercially undesirable. To overcome this, we assessed whether urchin gonad quantity and quality could be improved with access to high-quality feed and optimal environmental conditions, a process known as ‘gonad conditioning’. Specifically, we (1) surveyed the quality of urchins from barrens and kelp sites in Port Phillip Bay, Australia, over 18 mo and (2) tested if gonad conditioning was effective on urchins from barrens during and after the harvest season. Field surveys revealed considerable variation in gonad size across sites, habitats and collection periods (mean gonad index range: 3 to 12%). Gonad conditioning with the best diet increased urchin gonad size by up to 2.8 times during the harvest season. Moreover, gonads of conditioned urchins from one barren were 3 times brighter in colour and contained lower concentrations of arsenic than wild urchins. In contrast, gonad conditioning at 22°C after the harvest season was ineffective. Our results show that targeted in-season harvest from barrens and subsequent gonad conditioning produces roe of commercial quality, promoting the use of urchin fisheries as a tool for managing urchin barrens. KEY WORDS: Roe enhancement · Heliocidaris erythrogramma · Aquaculture · Urchin barren · Temperature · Purple urchin Full text in pdf format Supplementary material PreviousNextCite this article as: Pert CG, Swearer SE, Dworjanyn S, Kriegisch N, Turchini GM, Francis DS, Dempster T (2018) Barrens of gold: gonad conditioning of an overabundant sea urchin. Aquacult Environ Interact 10:345-361. https://doi.org/10.3354/aei00274 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 10. Online publication date: August 01, 2018 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2018 Inter-Research.

Gene expression across tissues, sex, and life stages in the sea urchin Tripneustes gratilla [Toxopneustidae, Odontophora, Camarodonta

The pan-tropical sea urchin Tripneustes gratilla is an ecologically and economically important shallow water algal grazer. The aquaculture of T. gratilla has spurred growing interest in the population biology of the species, and by extension the generation of more molecular resources. To this purpose, de novo transcriptomes of T. gratilla were generated for two adults, a male and a female, as well as for a cohort of approximately 1000 plutei larvae. Gene expression profiles of three adult tissue samples were quantified and compared. These samples were of gonadal tissue, the neural ring, and pooled tube feet and pedicellariae. Levels of shared and different gene expression between sexes, as well as across functional categories of interest, including the immune system, toxins, genes involved in fertilization, and sensory genes are highlighted. Differences in expression of isoforms between the sexes and Sex determining Region Y-related High Mobility Group box groups is observed. Additionally an expansion of the tumor suppressor DMBT1 is observed in T. gratilla when compared to the annotated genome of the sea urchin Strongylocentrotus purpuratus. The draft transcriptome of T. gratilla is presented here in order to facilitate more genomic level analysis of emerging model sea urchin systems.

The role of dissolved organic carbon concentration and composition on nickel toxicity to early life-stages of the blue mussel Mytilus edulis and purple sea urchin Strongylocentrotus purpuratus

Nickel (Ni) emissions resulting from production and transportation raise concerns about the impact of Ni exposure to marine ecosystems. Ni bioavailability models are established for FW systems, but the influence of chemical parameters (e.g. dissolved organic carbon (DOC)) on Ni toxicity within marine systems is less well understood. To examine the effects of DOC concentration and composition on Ni toxicity, acute toxicity tests were conducted on early life-stages of blue mussels (Mytilus edulis) and sea urchin embryos (Strongylocentrotus purpuratus) in full strength sea water (32 ppt). Nine different field collected samples of water with varying concentration (up to 4.5 mg C/L) and composition of DOC were collected from the east coast of the United States. Organic matter compositional analysis included molecular fluorescence and absorbance spectroscopy. The different DOC sources had different protective effects against embryo toxicity. The control (no DOC) Ni 48 h-EC50 for Mytilus embryos was 133 µg/L (95% confidence interval (C.I.) of 123–144 µg/L), while Strongylocentrotus embryos displayed control 96-h EC50 values of 207 µg/L (167–247 µg/L). The most significantly protective sample had high humic acid concentrations (as determined from fluorescence spectroscopy), which yielded an EC50 of 195 µg/L (169–222 µg/L) for Mytilus, and an EC50 of 394 µg/L (369–419 µg/L) for S. purpuratus. Among all samples, protection was related to both DOC quantity and quality, with fluorescence-resolved humic and fulvic acid concentrations showing the strongest correlations with protection for both species. These data suggest that DOC is protective against Ni toxicity in M. edulis and S. purpuratus, and that accounting for a DOC quality factor will improve predictive toxicity models such as the biotic ligand model.

Conserved RNA binding activity of a Yin-Yang 1 homologue in the ova of the purple sea urchin Strongylocentrotus purpuratus

Yin-Yang 1 (YY1) is a highly conserved transcription factor possessing RNA-binding activity. A putative YY1 homologue was previously identified in the developmental model organism Strongylocentrotus purpuratus (the purple sea urchin) by genomic sequencing. We identified a high degree of sequence similarity with YY1 homologues of vertebrate origin which shared 100% protein sequence identity over the DNA- and RNA-binding zinc-finger region with high similarity in the N-terminal transcriptional activation domain. SpYY1 demonstrated identical DNA- and RNA-binding characteristics between Xenopus laevis and S. purpuratus indicating that it maintains similar functional and biochemical properties across widely divergent deuterostome species. SpYY1 binds to the consensus YY1 DNA element, and also to U-rich RNA sequences. Although we detected SpYY1 RNA-binding activity in ova lysates and observed cytoplasmic localization, SpYY1 was not associated with maternal mRNA in ova. SpYY1 expressed in Xenopus oocytes was excluded from the nucleus and associated with maternally expressed cytoplasmic mRNA molecules. These data demonstrate the existence of an YY1 homologue in S. purpuratus with similar structural and biochemical features to those of the well-studied vertebrate YY1; however, the data reveal major differences in the biological role of YY1 in the regulation of maternally expressed mRNA in the two species.

AID/APOBEC-like cytidine deaminases are ancient innate immune mediators in invertebrates

In the course of both innate and adaptive immunity, cytidine deaminases within the activation induced cytidine deaminase (AID)/apolipoprotein B editing complex (APOBEC) family modulate immune responses by mutating specific nucleic acid sequences of hosts and pathogens. The evolutionary emergence of these mediators, however, seems to coincide precisely with the emergence of adaptive immunity in vertebrates. Here, we show a family of genes in species within two divergent invertebrate phyla—the echinoderm Strongylocentrotus purpuratus and the brachiopod Lingula anatina—that encode proteins with similarities in amino acid sequence and enzymatic activities to the vertebrate AID/APOBECs. The expression of these invertebrate factors is enriched in tissues undergoing constant, direct interactions with microbes and can be induced upon pathogen challenge. Our findings suggest that AID/APOBEC proteins, and their function in immunity, emerged far earlier than previously thought. Thus, cytidine deamination is probably an ancient innate immune mechanism that predates the protostome/deuterostome divergence.

Histidine168 is crucial for ΔpH-dependent gating of the human voltage-gated proton channel, hHV1.

We recently identified a voltage-gated proton channel gene in the snail Helisoma trivolvis, HtHV1, and determined its electrophysiological properties. Consistent with early studies of proton currents in snail neurons, HtHV1 opens rapidly, but it unexpectedly exhibits uniquely defective sensitivity to intracellular pH (pHi). The H+ conductance (gH)-V relationship in the voltage-gated proton channel (HV1) from other species shifts 40 mV when either pHi or pHo (extracellular pH) is changed by 1 unit. This property, called ΔpH-dependent gating, is crucial to the functions of HV1 in many species and in numerous human tissues. The HtHV1 channel exhibits normal pHo dependence but anomalously weak pHi dependence. In this study, we show that a single point mutation in human hHV1-changing His168 to Gln168, the corresponding residue in HtHV1-compromises the pHi dependence of gating in the human channel so that it recapitulates the HtHV1 response. This location was previously identified as a contributor to the rapid gating kinetics of HV1 in Strongylocentrotus purpuratus His168 mutation in human HV1 accelerates activation but accounts for only a fraction of the species difference. H168Q, H168S, or H168T mutants exhibit normal pHo dependence, but changing pHi shifts the gH-V relationship on average by <20 mV/unit. Thus, His168 is critical to pHi sensing in hHV1. His168, located at the inner end of the pore on the S3 transmembrane helix, is the first residue identified in HV1 that significantly impairs pH sensing when mutated. Because pHo dependence remains intact, the selective erosion of pHi dependence supports the idea that there are distinct internal and external pH sensors. Although His168 may itself be a pHi sensor, the converse mutation, Q229H, does not normalize the pHi sensitivity of the HtHV1 channel. We hypothesize that the imidazole group of His168 interacts with nearby Phe165 or other parts of hHV1 to transduce pHi into shifts of voltage-dependent gating.

SpTransformer proteins from the purple sea urchin opsonize bacteria, augment phagocytosis, and retard bacterial growth.

The purple sea urchin, Strongylocentrotus purpuratus, has a complex and robust immune system that is mediated by a number of multi-gene families including the SpTransformer (SpTrf) gene family (formerly Sp185/333). In response to immune challenge from bacteria and various pathogen-associated molecular patterns, the SpTrf genes are up-regulated in sea urchin phagocytes and express a diverse array of SpTrf proteins. We show here that SpTrf proteins from coelomocytes and isolated by nickel affinity (cNi-SpTrf) bind to Gram-positive and Gram-negative bacteria and to Baker’s yeast, Saccharomyces cerevisiae, with saturable kinetics and specificity. cNi-SpTrf opsonization of the marine bacteria, Vibrio diazotrophicus, augments phagocytosis, however, opsonization by the recombinant protein, rSpTrf-E1, does not. Binding by cNi-SpTrf proteins retards growth rates significantly for several species of bacteria. SpTrf proteins, previously thought to be strictly membrane-associated, are secreted from phagocytes in short term cultures and bind V. diazotrophicus that are located both outside of and within phagocytes. Our results demonstrate anti-microbial activities of native SpTrf proteins and suggest variable functions among different SpTrf isoforms. Multiple isoforms may act synergistically to detect a wide array of pathogens and provide flexible and efficient host immunity.

Influence of a prepared diet and a macroalga (Ulva sp.) on the growth, nutritional and sensory qualities of gonads of the sea urchin Paracentrotus lividus

This study evaluated the growth of the purple sea urchin Paracentrotus lividus, fed with two diets, in sea- and land-based systems compared to wild populations. The experiments investigated the effects of the feeding regimes on gonad yield, nutritional traits and overall quality. Sea-based trials were performed by the CNR of Taranto (Trial S), whereas land-based trials were performed in the facilities of the University of Cagliari (Trial L). Urchins fed with a laboratory prepared pelletized diet (P), and a mix diet PU (50% of P-Diet and 50% of fresh Ulva sp.) were compared to wild urchins (W). In both trials the experimental diets supported a gonad growth when compared to wild population (p < .05). Sensory characteristics, assessed by 6 panel experts for each trial, highlighted significant differences in gonad colour and taste in both trials, while only in Trial S for texture (p < .05). The changes in the biochemical composition of sea urchins' gonads caused significant variations in the nutritional profile. Sea urchins fed with the experimental diets contained higher levels of total protein and lipids and PUFAs than wild sea urchins, although EPA, DHA and n-3/n-6 ratio, were lower in urchins fed with artificial diets. In Trial L, total free amino acids showed an increase respect to W gonads (p < .05), whereas in Trial S, total free amino acids showed a decrease only in sea urchin fed with P-Diet (p < .05). The results presented in this study provide evidence of the good performance of the formulated diet assuming its application for the development of Mediterranean echinoculture.

Exploring the Sea Urchin Neuropeptide Landscape by Mass Spectrometry.

Neuropeptides are essential cell-to-cell signaling messengers and serve important regulatory roles in animals. Although remarkable progress has been made in peptide identification across the Metazoa, for some phyla such as Echinodermata, limited neuropeptides are known and even fewer have been verified on the protein level. We employed peptidomic approaches using bioinformatics and mass spectrometry (MS) to experimentally confirm 23 prohormones and to characterize a new prohormone in nervous system tissue from Strongylocentrotus purpuratus, the purple sea urchin. Ninety-three distinct peptides from known and novel prohormones were detected with MS from extracts of the radial nerves, many of which are reported or experimentally confirmed here for the first time, representing a large-scale study of neuropeptides from the phylum Echinodermata. Many of the identified peptides and their precursor proteins have low homology to known prohormones from other species/phyla and are unique to the sea urchin. By pairing bioinformatics with MS, the capacity to characterize novel peptides and annotate prohormone genes is enhanced. Graphical Abstract.