Urchin Species Research Articles

Abundance, size and biomass of long-spined sea urchins (Centrostephanus rodgersii) and red sea urchins (Heliocidaris tuberculata) in New South Wales, Australia

Context Detailed demographic information for the commercially harvested long-spined sea urchins (Centrostephanus rodgersii) and red sea urchins (Heliocidaris tuberculata) on nearshore reefs of New South Wales is unavailable. Aims This is the first detailed study of abundances and sizes of these sea urchin species on shallow reefs of New South Wales where the fishery operates. Methods Divers counted sea urchins and measured their sizes in transects in the nearshore mosaic habitat and in extensive barrens habitat at 51 sites along ~800 km of coast. Key results Centrostephanus was found at most sites in both habitats, whereas Heliocidaris was found at lower densities and at fewer sites. Heliocidaris was rare in the far south and in barrens habitat. Centrostephanus was, on average, smaller in barrens habitat than in the nearshore mosaic habitat, and size structures shifted towards smaller individuals from north to south. Conclusions Centrostephanus occurred at higher densities than did Heliocidaris and had a broader distribution along the coast and across the nearshore reefs where the fishery operates. Implications This study provides a historical baseline for these commercially and ecologically important species. The small biomass of Heliocidaris (~3% that of Centrostephanus) and its restricted distribution suggest it is vulnerable to overfishing.

Characterization of cellular and molecular immune components of the painted white sea urchin Lytechinus pictus in response to bacterial infection.

Sea urchins are basal deuterostomes that share key molecular components of innate immunity with vertebrates. They are a powerful model for the study of innate immune system evolution and function, especially during early development. Here we characterize the morphology and associated molecular markers of larval immune cell types in a newly developed model sea urchin, Lytechinus pictus. We then challenge larvae through infection with an established pathogenic Vibrio and characterize phenotypic and molecular responses. We contrast these to the previously described immune responses of the purple sea urchin Strongylocentrotus purpuratus. The results revealed shared cellular morphologies and homologs of known pigment cell immunocyte markers (PKS, srcr142) but a striking absence of subsets of perforin-like macpf genes in blastocoelar cell immunocytes. We also identified novel patterning of cells expressing a scavenger receptor cysteine rich (SRCR) gene in the coelomic pouches of the larva (the embryonic stem cell niche). The SRCR signal becomes further enriched in both pouches in response to bacterial infection. Collectively, these results provide a foundation for the study of immune responses in L. pictus. The characterization of the larval immune system of this rapidly developing and genetically enabled sea urchin species will facilitate more sophisticated studies of innate immunity and the crosstalk between the immune system and development.

Contrasting the development of larval and adult body plans during the evolution of biphasic lifecycles in sea urchins.

Biphasic lifecycles are widespread among animals, but little is known about how the developmental transition between larvae and adults is regulated. Sea urchins are a unique system for studying this phenomenon because of the stark differences between their bilateral larval and pentaradial adult body plans. Here, we use single-cell RNA sequencing to analyze the development of Heliocidaris erythrogramma (He), a sea urchin species with an accelerated, non-feeding mode of larval development. The sequencing time course extends from embryogenesis to roughly a day before the onset of metamorphosis in He larvae, which is a period that has not been covered by previous datasets. We find that the non-feeding developmental strategy of He is associated with several changes in the specification of larval cell types compared to sea urchins with feeding larvae, such as the loss of a larva-specific skeletal cell population. Furthermore, the development of the larval and adult body plans in sea urchins may utilize largely different sets of regulatory genes. These findings lay the groundwork for extending existing developmental gene regulatory networks to cover additional stages of biphasic lifecycles.

Determination of steroid hormones in sea urchins by microwave-assisted extraction and ultrahigh-performance liquid chromatography tandem mass spectrometry

Marine pollution poses significant threats to ecosystems by contaminating habitats and degrading marine life. This involves the need to develop efficient methodologies to evaluate the compounds that affect marine organisms, such as steroid hormones. The study of the presence of these compounds in marine organisms like sea urchins is very interesting given their role as bioindicators because they feed on algae and are constantly in contact with sediments. Given the low concentrations of steroid hormones in marine environments, it is necessary to develop extraction procedures that allow these pollutants to be extracted and preconcentrated before chemical analyses. Of all the extraction methods, microwave-assisted extraction (MAE) has been used for its many advantages compared to traditional extraction techniques, such as easy sample handling or scarce organic solvents use, and for providing very selective extractions. This study presents the novel MAE optimisation for the extraction of 15 hormones, including five oestrogens, three androgens, four progestogens and three glucocorticoids from sea urchin tissues. The extracted hormones were subsequently determined by high-performance liquid chromatography tandem mass spectrometry. To the best of the authors' knowledge, this approach has not been previously developed. To perform extraction optimisation, different variables were studied following factorial experimental designs. The optimised extraction method showed very appropriate analytical parameters, with limits of detection between 0.21 and 20.4 ng·g-1 for the four families of studied steroid hormones, and recovery extractions over 60 % for most target compounds. After optimisation, the analytical methodology was applied to samples of three different sea urchins species (Arbacia lixula, Paracentrotus lividus, Sphaerechinus granularis) caught in different locations around the Gran Canaria island (Canary Islands, Spain). The results showed the great applicability of the optimised methodology and two target hormones, boldenone and prednisolone, which were quantified in different samples and locations. This indicates the potential of sea urchins as bioindicators of the health of marine ecosystems and of anthropogenic contamination.

Stable germline transgenesis using the Minos Tc1/mariner element in the sea urchin Lytechinus pictus.

Stable transgenesis is a transformative tool in model organism biology. Although the sea urchin is one of the oldest animal models in cell and developmental biology, studies in this animal have largely relied on transient manipulation of wild animals, without a strategy for stable transgenesis. Here, we build on recent progress to develop a more genetically tractable sea urchin species, Lytechinus pictus, and establish a robust transgene integration method. Three commonly used transposons (Minos, Tol2 and piggyBac) were tested for non-autonomous transposition, using plasmids containing a polyubiquitin promoter upstream of a H2B-mCerulean nuclear marker. Minos was the only transposable element that resulted in significant expression beyond metamorphosis. F0 animals were raised to sexual maturity, and spawned to determine germline integration and transgene inheritance frequency, and to characterize expression patterns of the transgene in F1 progeny. The results demonstrate transgene transmission through the germline, the first example of a germline transgenic sea urchin and, indeed, of any echinoderm. This milestone paves the way for the generation of diverse transgenic resources that will dramatically enhance the utility, reproducibility and efficiency of sea urchin research.

Expression and Transcriptional Targets of TGFβ-RII in Paracentrotus lividus Larval Skeletogenesis.

Organisms from the five kingdoms of life use minerals to harden their tissues and make teeth, shells and skeletons, in the process of biomineralization. The sea urchin larval skeleton is an excellent system to study the biological regulation of biomineralization and its evolution. The gene regulatory network (GRN) that controls sea urchin skeletogenesis is known in great details and shows similarity to the GRN that controls vertebrates' vascularization while it is quite distinct from the GRN that drives vertebrates' bone formation. Yet, transforming growth factor beta (TGF-β) signaling regulates both sea urchin and vertebrates' skeletogenesis. Here, we study the upstream regulation and identify transcriptional targets of TGF-β in the Mediterranean Sea urchin species, Paracentrotus lividus. TGF-βRII is transiently active in the skeletogenic cells downstream of vascular endothelial growth factor (VEGF) signaling, in P. lividus. Continuous perturbation of TGF-βRII activity significantly impairs skeletal elongation and the expression of key skeletogenic genes. Perturbation of TGF-βRII after skeletal initiation leads to a delay in skeletal elongation and minor changes in gene expression. TGF-β targets are distinct from its transcriptional targets during vertebrates' bone formation, suggesting that the role of TGF-β in biomineralization in these two phyla results from convergent evolution.

Trace metals pollution and trophic position of three sea urchin species in the Gulf of California.

Sea urchin species are ecologically important in the Gulf of California and are becoming popular as a local fishery due to their commercial value. The most abundant species are Echinometra vanbrunti, Eucidaris thouarsii, and Tripneustes depressus. The objective of this study was to evaluate cadmium, lead, copper, zinc, and iron concentrations, as well as stable isotope values in these sea urchin species in the Santa Rosalia mining area (STR), in three sites: Punta Gorda, Punta el Aterrizaje, and Punta Salina. The highest Fe concentration (100.2 mg kg-1) was found in E. vanbrunti, while the highest concentrations of Pb (15.1 mg kg-1), Cu (14.5 mg kg-1), and Zn (347.7 mg kg-1) were recorded in E. thouarsii, and the highest Cd concentration (10.8 mg kg-1) was found in T. depressus. The main health risk of trace metal pollution in STR may be caused by Cd and Pb. δ15N and δ13C values were higher in E. thouarsii and T. depressus, respectively; E. thouarsii has the highest trophic position. Specimen size was not related to metal concentrations, but a positive relationship was observed between specimen size and isotopic values in T. depressus. The three species showed different bioaccumulation patterns for the metals analyzed. Additionally, collection sites and seasons play an important role in the variability of metal concentration.

Comparison of Immune Indicators Related to Phagocytosis of Five Species of Sea Urchins under Artificial Infection with the Pathogenic Bacterium of Black Mouth Disease.

To screen for immune indicators closely related to disease resistance, two species of sea urchin susceptible to black mouth disease (Strongylocentrotus intermedius, S. intermedius ♀ × Heliocidaris crassispina ♂) and three species of sea urchin resistant to black mouth disease (H. crassispina, H. crassispina ♀ × S. intermedius ♂ and Mesocentrotus nudus) were artificially infected with the black mouth pathogen Vibrio echinoideorum. The phagocytosis-related immune indices of the five sea urchin species were compared at different time points post-infection. The results demonstrated that the parameters such as apoptotic rate of phagocytes, mean contribution value (MCV) of single effective phagocyte on Acid Phosphatase (ACP), Reactive Oxygen Species (ROS), and Total Antioxidant Capacity (T-AOC) of the five sea urchin species first increased and then decreased after infection. The key time points were 3 h to 6 h and 48 h post-infection when the black mouth disease-resistant and susceptible sea urchins demonstrated differences. At 3 h or 6 h post-infection, the up-regulation folds in MCV of ACP, ROS and T-AOC of black mouth disease-resistant sea urchins were considerably higher than that of the susceptible sea urchins. At 6 h post-infection, the apoptosis rate and the phagocytic index (PI) of the black mouth disease-resistant sea urchins were significantly higher than those of the susceptible sea urchins (p < 0.05). At 48 h post-infection, the necrosis rate of phagocytes, MCV of ACP and MCV of ROS of the black mouth disease-resistant sea urchins were significantly lower than those of the susceptible sea urchins (p < 0.05). The apoptosis and necrosis rate of phagocytes, PI, and MCV on ACP, ROS may be used as indicators of disease resistance in sea urchins. Disease resistance standards in immune indices can be summarized as phagocytosis increases greatly in the early infection stage and decreases timely to a normal level after killing the pathogen in a short period.

Community Structure of Sea Urchins (Echinoidea) in the Intertidal Zone of Thomas Beach, Uluwatu

Thomas Beach, located in Uluwatu, Province of Bali, is a rocky shore inhabited by sea urchins. The research aims to discover the habitat characteristics and community structure of sea urchins (Echinoidea) in the intertidal zone of Thomas Beach. Data collection was conducted from April to May 2023 during the lowest tide. A quantitative method with modified line transects was used for data collection. Data collected included the number and species of sea urchins, water quality parameters (temperature, salinity, pH, dissolved oxygen, water clarity, and depth), and substrate types. Data were analyzed using Microsoft Excel, including individual density, diversity index, uniformity index, and dominance index. The research findings revealed five species of sea urchins: Echinotrix calamaris, Echinometra oblonga, Echinometra mathaei, Tripneustes gratilla, and Stomopneustes variolaris. The highest density of sea urchins was found in E. oblonga (16.91 ind/m2). The diversity index values ranged from 0.4936 to 0.8721, indicating a low level of diversity. The uniformity index values ranged from 0.4493 to 0.784, suggesting the community is relatively unstable. The dominance index values ranged from 0.5036 to 0.7166, indicating a moderate level of dominance. The aquatic habitat characteristics, based on the research findings, it was determined that a temperature of 30℃, salinity ranging from 31.77 to 32.76, pH of 8, dissolved oxygen (DO) of 5 mg/l, water clarity of 100%, and a depth ranging from 8.4 to 33.93 cm. The substrate type was rocky at station 1, sandy with seagrass at station 2, and rocky sandy at station 3.

Larval Biometry as an Endpoint in Chronic Sea Urchin Assays Echinometra lucunter (Linnaeus, 1758)

This study was carried out with the aim of contributing to the improvement of the evaluation of sea urchin embryo-larval tests, reducing its analysis subjectivity and also to solve the problems associated with the morphology of different Echinodermata larvae used in ecotoxicological tests. In this regard, the larval size technique (biometrics) was applied as an endpoint in sub-lethal assays using the reference toxicants zinc sulfate and potassium dichromate as a standard for calibrating the EC50 estimate (Median Effective Concentration) and NOEC (No Observed Effect Concentration). The tests, using the sea urchin species Echinometra lucunter, were carried out between the years 2017 to 2019 and were analyzed by two methods, the traditional one (counting normal larvae and those with developmental delay) and biometrics based on the maximum length of the larvae obtained in the treatments. It was established that the minimum number of measurements of the different stages of development (egg, embryo and larva) was 35 (n) per replicate. For the tests carried out over 15 months, it was verified, based on the Wald Test, that there is a seasonality in the sizes of the larvae. The EC50 of the metals tested was similar between the traditional and biometric methods when adopting the size of 18-hour-old larvae as a reference for 100% effect, but there was disagreement between the methods when the size of the eggs is considered as the total effect. On the other hand, the estimates of the NOEC were more sensitive by the biometry method, in disagreement with the traditional method.

Selection Shapes the Genomic Landscape of Introgressed Ancestry in a Pair of Sympatric Sea Urchin Species.

A growing number of recent studies have demonstrated that introgression is common across the tree of life. However, we still have a limited understanding of the fate and fitness consequence of introgressed variation at the whole-genome scale across diverse taxonomic groups. Here, we implemented a phylogenetic hidden Markov model to identify and characterize introgressed genomic regions in a pair of well-diverged, nonsister sea urchin species: Strongylocentrotus pallidus and Strongylocentrotus droebachiensis. Despite the old age of introgression, a sizable fraction of the genome (1% to 5%) exhibited introgressed ancestry, including numerous genes showing signals of historical positive selection that may represent cases of adaptive introgression. One striking result was the overrepresentation of hyalin genes in the identified introgressed regions despite observing considerable overall evidence of selection against introgression. There was a negative correlation between introgression and chromosome gene density, and two chromosomes were observed with considerably reduced introgression. Relative to the nonintrogressed genome-wide background, introgressed regions had significantly reduced nucleotide divergence (dXY) and overlapped fewer protein-coding genes, coding bases, and genes with a history of positive selection. Additionally, genes residing within introgressed regions showed slower rates of evolution (dN, dS, dN/dS) than random samples of genes without introgressed ancestry. Overall, our findings are consistent with widespread selection against introgressed ancestry across the genome and suggest that slowly evolving, low-divergence genomic regions are more likely to move between species and avoid negative selection following hybridization and introgression.

Sea urchin roe quality within urchin barrens and improvement through kelp restoration

AbstractSea urchin overgrazing is a major cause of kelp loss and consequently sea urchin removal is frequently promoted as a tool for restoring kelp in urchin barrens. While many sea urchin species support high‐end roe fisheries, roe condition is generally lower in barrens than in kelp forests due to reduced food availability. Understanding how roe condition varies between kelp and barren habitats, and in response to kelp restoration, is key to developing effective, culturally and socially acceptable approaches to sea urchin removal and for assessing the potential benefits of kelp restoration. We assessed whether sea urchin roe quality within urchin barrens in northeastern Aotearoa New Zealand can be sufficient for harvest, and whether sea urchin removal can ultimately enhance urchin roe condition (by increasing food quality and quantity). We monitored roe condition (roe weight and gonadosomatic index [GSI]) in kelp forest and urchin barrens monthly for one year at two sites, and quarterly over two years at four sites following large‐scale (1.6–2 ha) sea urchin removal from urchin barrens. While roe condition was generally lower in barrens, the magnitude of this difference varied seasonally and among sites. Sea urchin roe quality within barrens was sufficient for commercial harvest (GSI ≥ 6%) during spring–summer at three sites. Following large‐scale sea urchin removal, kelp and fucoid density increased over two years (~9–58 plants m−2), but remained low in barren control areas. Although variable, sea urchins from removal areas (restored kelp) typically showed increased GSI, roe weight, and improved roe color within nine months following removal. These results suggest that, at some locations, harvest may provide a viable method for removing urchins from urchin barrens for kelp restoration purposes. However, to ensure sea urchin densities are reduced and maintained below the critical levels needed to achieve restoration outcomes, strategic approaches with critical evaluation of methods are required. Furthermore, we demonstrate that effectively removing urchins and promoting kelp recovery can ultimately improve urchin roe quality.

Larval development of Holothuria tubulosa, a new tractable system for evo-devo

To explore animal diversity, new experimentally tractable organisms must be established. Echinoderms include five groups of marine animals that have been used as developmental models for over a century thanks to their low costs, high fecundity, optically clear larvae and genetic tractability. An additional advantage of echinoderms is that their larval forms display diverse morphologies. This rich diversity enables comparative studies to investigate the evolutionary relationships among cell types, tissues, and organs. However, reproducible protocols to obtain gametes, detailed information on embryogenesis, and genomic tools have been optimized only for selected species of sea urchins and sea stars. To address this gap, we established the abundant Mediterranean sea cucumber Holothuria tubulosa as a new experimental system. Here we describe a method to reliably obtain gametes and make embryonic cultures multiple times from the same animal and characterize unique larval tissues combining immunohistochemistry and high-resolution microscopy. This work represents a step forward in our understanding of holothurian development and establishes H. tubulosa as an emerging experimental system for evo-devo and other biological disciplines.

Investigating the timing of spawning of two sea urchins (Tripneustes gratilla and Toxopneustes pileolus)

AbstractMany marine organisms broadcast gametes for external fertilization, thus conspecifics need to concentrate the time of gamete release through synchronization with environmental factors. We investigated the timing of spawning in two sea urchin species, Tripneustes gratilla and Toxopneustes pileolus, by assessing the spawning potential of individuals using both surveys and experiments in southern Taiwan from March to November 2010. We developed a new method to observe the spawning potential without sacrificing any individuals, defining those individuals‐initiated spawning within 30 min after 10 s of exposure to air as having the spawning potential. We discovered that the percentage of individuals with spawning potential, that is, the spawning ratios of the population, varied greatly from 0% to 80% in To. pileolus and from 0% to 50% in Tr. gratilla within the reproductive seasons. We evaluated the possibility of a lunar/semilunar rhythm of spawning ratios of the population and tested three environmental factors, that is, light intensity, tide, and temperature that could potentially affect the spawning potential of the sea urchins by experiments. Individuals with spawning potential were neither randomly nor evenly distributed among days but were aggregated on certain days; however, no lunar/semilunar rhythm of the spawning ratios was detected within the reproductive season. The possible role of the tidal factor within a day was not found in experiments in either species. However, when water temperature was &gt;27°C in our surveys, significantly higher spawning ratios were observed in To. pileolus, but not in Tr. gratilla in the reproductive season. A further temperature experiment in To. pileolus supported the positive role of high temperature on the spawning ratios of individuals. In addition, To. pileolus was more likely to spawn during the day than at night, and the light/dark experiments suggested that the spawning potential was controlled by an endogenous biological clock rather than by the ambient light conditions directly. The lack of rhythmic pattern and yet concentrated spawning of these sea urchins may be adaptive to avoid predation.

Characterization of thyrotropin-releasing hormone producing neurons in sea urchin, from larva to juvenile.

Most sea urchin species are indirect developers, going through a larval stage called pluteus. The pluteus possesses its own nervous system, consisting mainly of the apical organ neurons (controlling metamorphosis and settlement) and ciliary band neurons (controlling swimming behavior and food collection). Additional neurons are located in various areas of the gut. In recent years, the molecular complexity of this apparently "simple" nervous system has become apparent, with at least 12 neuronal populations identified through scRNA-sequencing in the species Strongylocentrotus purpuratus. Among these, there is a cluster of neurosecretory cells that produce a thyrotropin-releasing hormone-type neuropeptide (TRHergic) and that are also photosensory (expressing a Go-Opsin). However, much less is known about the organization of the nervous system in other sea urchin species. The aim of this work was to thoroughly characterize the localization of the TRHergic cells from early pluteus to juvenile stages in the Mediterranean sea urchin species Paracentrotus lividus combining immunostaining and whole mount in situ hybridization. We also compared the localization of TRHergic cells in early plutei of two other sea urchin species, Arbacia lixula and Heliocidaris tuberculata. This work provides new information on the anatomy and development of the nervous system in sea urchins. Moreover, by comparing the molecular signature of the TRHergic cells in P. lividus and S. purpuratus, we have obtained new insights how TRH-type neuropeptide signaling evolved in relatively closely related species.

Spontaneous intersibling polymorphism in the development of dopaminergic neuroendocrine cells in sea urchin larvae: impacts on the expansion of marine benthic species.

The plasticity of the nervous system plays a crucial role in shaping adaptive neural circuits and corresponding animal behaviors. Understanding the mechanisms underlying neural plasticity during development and its implications for animal adaptation constitutes an intriguing area of research. Sea urchin larvae offer a fascinating subject for investigation due to their remarkable evolutionary and ecological diversity, as well as their diverse developmental forms and behavioral patterns. We conducted immunochemical and histochemical analyses of serotonin-containing (5-HT-neurons) and dopamine-containing (DA-positive) neurons to study their developmental dynamics in two sea urchin species: Mesocentrotus nudus and Paracentrotus lividus. Our approach involved detailed visualization of 5-HT- and DA-positive neurons at gastrula-pluteus stages, coupled with behavioral assays to assess larval upward and downward swimming in the water column, with a focus on correlating cell numbers with larval swimming ability. The study reveals a heterochronic polymorphism in the appearance of post-oral DA-positive neuroendocrine cells and confirms the stable differentiation pattern of apical 5-HT neurons in larvae of both species. Notably, larvae of the same age exhibit a two- to four-fold difference in DA neurons. An increased number of DA neurons and application of dopamine positively correlate with larval downward swimming, whereas 5-HT-neurons and serotonin application induce upward swimming. The ratio of 5-HT/DA neurons determines the stage-dependent vertical distribution of larvae within the water column. Consequently, larvae from the same generation with a higher number of DA-positive neurons tend to remain at the bottom compared to those with fewer DA-positive neurons. The proportion of 5-HT and DA neurons within larvae of the same age underlies the different potentials of individuals for upward and downward swimming. A proposed model illustrates how coordination in humoral regulation, based on heterochrony in DA-positive neuroendocrine cell differentiation, influences larval behavior, mitigates competition between siblings, and ensures optimal population expansion. The study explores the evolutionary and ecological implications of these neuroendocrine adaptations in marine species.

Reproductive toxicity assessment of cellulose nanofibers, citric acid, and branched polyethylenimine in sea urchins: Eco-design of nanostructured cellulose sponge framework (Part B)

In the framework of a safe-by-design approach, we previously assessed the eco-safety of nanostructured cellulose sponge (CNS) leachate on sea urchin reproduction. It impaired gamete quality, gamete fertilization competence, and embryo development possibly due to the leaching of chemical additives used during the CNS synthesis process. To extend this observation and identify the component(s) that contribute to CNS ecotoxicity, in the present study, we individually screened the cytotoxic effects on sea urchin Arbacia lixula and Paracentrotus lividus gametes and embryos of the three main constituents of CNS, namely cellulose nanofibers, citric acid, and branched polyethylenimine. The study aimed to minimize any potential safety risk of these components and to obtain an eco-safe CNS. Among the three CNS constituents, branched polyethylenimine resulted in the most toxic agent. Indeed, it affected the physiology and fertilization competence of male and female gametes as well as embryo development in both sea urchin species. These results are consistent with those previously reported for CNS leachate. Moreover, the characterisation of CNS leachate confirmed the presence of detectable branched polyethylenimine in the conditioned seawater even though in a very limited amount. Altogether, these data indicate that the presence of branched polyethylenimine is a cause-effect associated with a significant risk in CNS formulations due to its leaching upon contact with seawater. Nevertheless, the suggested safety protocol consisting of consecutive leaching treatments and conditioning of CNS in seawater can successfully ameliorate the CNS ecotoxicity while maintaining the efficacy of its sorbent properties supporting potential environmental applications.

Sea Urchin Food Waste into Bioactives: Collagen and Polyhydroxynaphtoquinones from P. lividus and S. granularis

Approximately 75,000 tons of different sea urchin species are globally harvested for their edible gonads. Applying a circular economy approach, we have recently demonstrated that non-edible parts of the Mediterranean Sea urchin Paracentrotus lividus can be fully valorized into high-value products: antioxidant pigments (polyhydroxynaphthoquinones—PHNQs) and fibrillar collagen can be extracted to produce innovative biomaterials for biomedical applications. Can waste from other edible sea urchin species (e.g., Sphaerechinus granularis) be similarly valorised? A comparative study on PHNQs and collagen extraction was conducted. PHNQ extraction yields were compared, pigments were quantified and identified, and antioxidant activities were assessed (by ABTS assay) and correlated to specific PHNQ presence (i.e., spinochrome E). Similarly, collagen extraction yields were evaluated, and the resulting collagen-based biomaterials were compared in terms of their ultrastructure, degradation kinetics, and resistance to compression. Results showed a partially similar PHNQ profile in both species, with significantly higher yield in P. lividus, while S. granularis exhibited better antioxidant activity. P. lividus samples showed higher collagen extraction yield, but S. granularis scaffolds showed higher stability. In conclusion, waste from different species can be successfully valorised through PHNQ and collagen extraction, offering diverse applications in the biomedical field, according to specific technical requirements.

Multi-omic analysis reveals genes and proteins integral to bioactivity of Echinochrome A isolated from the waste stream of the sea urchin industry in Aotearoa New Zealand.

Evechinus chloroticus (commonly known as kina) is a sea urchin species endemic to New Zealand. Its roe is a culinary delicacy to the indigenous Māori and a globally exported food product. Echinochrome A (Ech A) is a bioactive compound isolated from the waste product of kina shells and spines; however, the molecular mechanisms of Ech A bioactivity are not well understood, partly due to Ech A never being studied using unbiased genome-wide analysis. To explore the high-value pharmaceutical potential of kina food waste, we obtained unbiased functional genomic and proteomic profiles of yeast cells treated with Echinochrome A. Abundance was measured for 4100 proteins every 30 min for four hours using fluorescent microscopy, resulting in the identification of 92 proteins with significant alterations in protein abundance caused by Ech A treatment that were over-represented with specific changes in DNA replication, repair and RNA binding after 30 min, followed by specific changes in the metabolism of metal ions (specifically iron and copper) from 60-240 min. Further analysis indicated that Ech A chelated iron, and that iron supplementation negated the growth inhibition caused by Ech A. Via a growth-based genome-wide analysis of 4800 gene deletion strains, 20 gene deletion strains were sensitive to Ech A in an iron-dependent manner. These genes were over-represented in the cellular response to oxidative stress, suggesting that Ech A suppressed growth inhibition caused by oxidative stress. Unexpectedly, genes integral to cardiolipin and inositol phosphate biosynthesis were required for Ech A bioactivity. Overall, these results identify genes, proteins, and cellular processes mediating the bioactivity of Ech A. Moreover, we demonstrate unbiased genomic and proteomic methodology that will be useful for characterizing bioactive compounds in food and food waste.

Testing sea urchin and green sea turtle consumption of the allelopathic macroalga Galaxaura divaricata.

Galaxaura divaricata is a partially calcified macroalga that hampers coral recruitment, growth, and recovery via the excretion of allelopathic secondary metabolites. Herbivorous fishes are not major consumers of Galaxaura spp. and there is a need to understand feeding preferences for Galaxaura divaricata in other macroherbivores, like sea urchins and green sea turtles that could act as potential controlling agents. Under certain environmental conditions, G. divaricata can proliferate and overgrow degraded reefs for several years, as documented for several coral patch reefs in the lagoon of Dongsha Atoll, South China Sea. This study aimed to experimentally test the feeding preferences of five species of sea urchin and two individual green sea turtles, Chelonia mydas, for G. divaricata. Specifically, we quantified and compared the consumption rates of the allelopathic G. divaricata with Gracilaria edulis, a nonallelopathic, fleshy red alga, known to be highly favored by herbivores. Results showed that the five urchin species fed on both G. edulis and G. divaricata. However, urchins consumed 2-8 times less wet weight of G. divaricata (range 0.3-3.1 g urchin-1 24 h-1) compared to G. edulis (range 0.6-18 g urchin-1 24 h-1), suggesting that urchin grazing may exert some control on G. divaricata abundance but is likely ineffective for a large-scale removal of the alga. Further, both green sea turtles avoided G. divaricata and selectively fed on G. edulis. More experiments are needed to test the potential role of herbivores in controlling the overgrowth of coral competitive and allelopathic macroalgae, like Galaxaura on coral reefs.