No apparent impact of moderate temperature increase on growth and fecundity in the sea star Asterias rubens.

Oogenesis requires complex interactions between germline and somatic cell types in the ovary. How did these cell types and their signaling interactions evolve? Here we use the sea star Patiria miniata as a non-chordate deuterostome representative to define the ovarian cell type toolkit in echinoderms. Sea stars continuously produce millions of new oocytes throughout their lifespan, making them a practical system to understand the mechanisms that drive oogenesis from a biomedical and evolutionary perspective. We performed scRNA-seq combined with high-resolution 3D imaging to reveal the ovarian cell types and their spatial organization. Our data support the presence of putative oogonial stem cells, granulosa-like, and theca-like cells, which display similarities with their mammalian counterparts. We also describe possible signaling interactions between somatic and germ line cells. Lastly, our data may suggest an intrinsic ovarian neuroendocrine system which could potentially regulate oogenesis.

Biomineralized structures produced by living organisms are widely recognized for their exceptional mechanical performance, yet their potential optical roles are relatively less explored. Here, we demonstrate that within the calcitic ossicle-based skeleton of the sea star Protoreaster nodosus, where each ossicle represents a discrete skeletal element, one specialized ossicle, known as the terminal plate, contains a radially arranged array of light-guiding structures (LGSs). These LGSs exhibit an elongated, cone-like geometry (~250 μm in length) and are embedded within the porous stereom, a characteristic meshwork architecture of echinoderms analogous to open-cell cellular solids and composed of magnesium-containing single-crystalline calcite. Optical experiments demonstrate that, unlike other skeletal elements, the terminal plate can transmit and focus light into an internal cavity via the LGS array. Combined optical analyses using ray-tracing and finite-difference time-domain simulations reveal that each LGS transmits ca. 70% of incident light at normal incidence and concentrates it up to 2.8-fold at its exiting surface. Furthermore, when acting collectively as the LGS array within the terminal plate, the LGSs capture light over a broad field of view (~120°), resulting in an integrated transmitted intensity that is sixfold to eightfold greater than the incoming intensity perceived by a single LGS. Although the biological function of this optical capability remains uncertain, this natural porous structure demonstrates that cellular solids can integrate efficient light-guiding behavior while enhancing mechanical properties (i.e., threefold increase in stiffness compared with random stereom), offering design insights for lightweight, multifunctional structures.

Beating the heat at low tide: infrared thermography suggests persistent evaporative cooling in a keystone predator (Pisaster ochraceus).

Abstract Ecological studies of marine invertebrates lacking external sexual dimorphism have often overlooked potential roles of sex and sex determination systems. Yet sex-dependent effects can influence ecological outcomes for many species, including keystone echinoderms like the sunflower sea star (Pycnopodia helianthoides), which can play important roles in maintaining marine biodiversity. Although DNA sequencing has previously been used to document genetic associations with sex in some echinoderms, there is currently little information on sex determination in sea stars lacking sexual dimorphism. Here, we used whole-genome resequencing of 16 female and 18 male P. helianthoides to test for genetic associations with sex and to identify candidate genes. Principal component analysis and outlier tests were used to identify sex-associated genome regions and single-nucleotide polymorphisms distinguishing males from females. We used the annotated P. helianthoides genome to associate gene models with candidate single-nucleotide polymorphisms. Sex-associated single-nucleotide polymorphisms, characterized by male homozygosity and female heterozygosity, were concentrated in distinct haplotypes; the majority (86%) were on just two chromosomes. Of the 76 outlier sex-specific single-nucleotide polymorphisms identified, 73 always discriminated female sea stars from males. These single-nucleotide polymorphisms are in or adjacent to genes involved in gonad formation, sex-specific gene expression, and sex determination processes. These results provide an important resource for identifying sex and enable study of the role that sex plays in the biology, ecology, and conservation of the sunflower sea star.

Sea star wasting (SSW) disease has devastated sea star populations along the North American Pacific coast with some recovery since 2013. Though Vibrio pectenicida has recently been implicated as a causative agent, the dynamics of disease progression and host response in natural environments remain understudied. Here, we integrate transcriptomic and microbial data from wild Pycnopodia helianthoides sampled across sites affected and unaffected by SSW in southeast Alaska during the initial outbreak recorded in the region in 2016. Individuals exposed to SSW but lacking visible signs of disease showed elevated expression of complement system components, pathogen recognition and immune regulatory pathways relative to naive individuals. Differential expression of extracellular matrix and tissue remodelling genes suggests disruption of tissue homeostasis preceding visible signs of disease. Furthermore, network analyses revealed certain microbial abundances, including Vibrio spp., correlated with immune response and tissue integrity gene expression. Although V. pectenicida was detected in some samples, its rarity prevented detailed analysis. Nevertheless, higher prevalence in exposed samples is consistent with growing evidence implicating Vibrio infection as an agent of SSW. Together, our findings offer insight into early host-pathogen dynamics in wild populations, underscoring links between immune activation and microbial shifts with the onset of SSW disease.

Outbreaks of crown-of-thorns sea stars (CoTS) threaten coral reef integrity and biodiversity, yet local dynamics and short-term responses to control remain insufficiently described. This study characterised an outbreaking Acanthaster population in two specific sites of the coast of Khor Fakkan (Gulf of Oman, United Arab Emirates) to resolve species identity, population composition, prey selection and the effects of targeted removals. All sequenced individuals clustered in two related haplotypes belonging to the species Acanthaster planci. Benthic surveys showed moderate live-coral cover, dominated by massive Porites sp. colonies. Moreover, the observations of 139 preyed colonies revealed pronounced genus-level selectivity, with branching and complex morphologies suffering disproportionately and massive forms largely avoided. However, the selection of massive Plesiastrea and Favites genera as preferred coral prey might suggest a shift towards less preferred coral in the CoTS diet, posing a severe threat to coral reefs’ integrity. Intensive removal reduced the local density, up to 86%, and provided substantial short-term relief, but continued monitoring is required to secure long-term reef resilience.

This paper develops an intelligent Enhanced Starfish Optimization (ESFO) algorithm for optimizing a secure wireless communication infrastructure. The Starfish Optimization (SFO) algorithm is inspired by starfish biology, using the integrated modeling of the arm-based exploration, preying, and regeneration behaviors of starfish. To further enhance the exploitation capability of the standard Starfish Optimization (SFO), the proposed Enhanced Starfish Optimization (ESFO) integrates a fitness-based interacting mechanism within the exploitation phase. This innovative modification improves local search accuracy, preserves population diversity, and mitigates premature convergence without introducing additional control parameters. Moreover, the proposed Enhanced Starfish Optimization (ESFO) is designed for secure wireless transmission, which is considered one of the main topics in next-generation wireless network infrastructure. The investigated network addresses the use of Simultaneously Transmitting and Reflecting RIS (STAR-RIS) in the security of the physical layer. This implemented STAR-RIS has a coupled phase shift to create reflected and transmission links, unlike traditional Reconfigurable Intelligent Surface (RIS). In this regard, we create a safe beamforming architecture that optimizes both Base Station (BS) precoding vectors and STAR-RIS transmission/reflection coefficients. In order to validate the efficiency of the proposed Enhanced Starfish Optimization (ESFO) algorithm, it is compared to several benchmark optimizers such as standard Starfish Optimization (SFO), Dhole Optimizer (DO), Neural Network Algorithm (NNA), Crocodile Ambush Optimization Algorithm (CAOA), and white shark Optimizer (WSO). These comparisons include several scenarios based on the transmitted power threshold which is varied in the range of 20 to 70 dBm with step of 5 dBm. The simulation results show that the proposed Enhanced Star Fish Optimization (ESFO) algorithm consistently outperforms existing benchmark approaches. This study supports future intelligent communication infrastructures in terms of secrecy and achievable rates over a range of transmit power levels. In particular, ESFO improves performance by up to 20-25% while converging 40-50% faster than traditional optimization algorithms, demonstrating its usefulness and resilience in STAR-RIS-assisted secure communication systems. The suggested ESFO-enabled architecture outperforms standard RIS-based systems in terms of secrecy capacity, according to numerical studies, and low-resolution STAR-RIS phase-shifters are sufficient to ensure robust secrecy performance.

Post traumatic response of coelomocytes in the common sea star Echinastersepositus.

The structure and functioning of Arctic marine food webs are shaped by the origin (ice- or pelagic-derived), quantity, and quality of primary production, which are influenced by environmental factors. While pan-Arctic variability has been widely studied, spatial differences at smaller scales (~10-500 km) remain poorly understood. In this study, we examined north-south spatial variability around Southampton Island in the Hudson Bay (Nunavut) focusing on (i) vertical trophic structure, (ii) the relative contributions of ice algae and phytoplankton-derived carbon to the food web and (iii) benthic functional diversity. We measured bulk stable carbon and nitrogen isotopes as well as highly branched isoprenoids in samples belonging to 149 species, including invertebrates, fishes, and marine mammals. We found marked contrasts between the northern and southern food webs, reflecting different environmental conditions. The north was characterized by deeper depths (mean of 132.0 m), with relatively lower ice algae production relative to phytoplankton, a narrow δ13C range, low sympagic carbon (mean of 13.5% ± 10.7%), and dominance of filter feeders. As a result, the northern benthic sub-web relied mainly on phytoplankton and occupied four trophic levels, including top predator sea stars. In contrast, the south was shallower (mean 60.7 m), with higher ice algae input, a broader δ13C range, higher sympagic carbon (35.1% ± 19.7%), a benthic sub-web occupying only three trophic levels, and a dominance of deposit feeders. Here, trophic truncation among benthic species likely represents relatively stronger top-down control by walruses, a benthivorous predator that specializes on large bivalves, facilitated by a shallower bathymetry and is considered prime walrus habitat. However, this selective pressure fosters benthic functional trait richness by releasing non-target species, in conjunction with a diversified food supply from both ice algae and phytoplankton. These results demonstrate how small-scale spatial variation in depth and primary production sources can restructure Arctic food webs, with implications for ecosystem functioning under changing ice conditions.

The fatty acid profiles of the sea star Pycnopodia helianthoides differ by collection location

Sunflower Sea Stars Can Counteract Warming-Driven Increases in Sea Urchin Populations.

Predation of newly settled Dungeness crab by juvenile sunflower sea stars.

Marine ecotoxicological risk assessment relies on a limited range of biological models, particularly in the case of benthic environments, thereby limiting the ecological realism of toxicity evaluations. Although echinoderms are widely recognised as sensitive and ecologically relevant organisms, experimental research has predominantly focused on sea urchins, leaving other echinoderm classes insufficiently explored. This study combines a critical literature review on sea stars (class Asteroidea) and brittle stars (class Ophiuroidea) with targeted experimental evidence to evaluate their potential as models for assessing emerging contaminants in marine ecosystems. A systematic evaluation of ecotoxicological studies published over the past two decades was conducted to assess the use of sea stars and brittle stars in toxicity testing, with particular attention to experimental design, biological endpoints, and ethical considerations. The analysis reveals that research on these classes is sporadic and unevenly distributed, with a strong emphasis on bioaccumulation endpoints and a focus primarily on metal exposure, while only a limited number of studies have addressed emerging contaminants. In contrast, fewer studies have investigated functional or physiological endpoints. Moreover, the literature suggests that both sea stars and brittle stars exhibit a range of sensitive, non-lethal endpoints suitable for repeated measures testing and long-term exposure scenarios. Based on the identified knowledge gaps, targeted experimental assays were designed to explore the applicability of brittle stars as models for emerging contaminants. Two brittle star species collected from the gulf of La Spezia (Ligurian Sea, Italy) were exposed for seven days to gadolinium, a rare earth element increasingly detected in aquatic environments due to its widespread use in medical imaging and green technologies, across a concentration range of 0 to 1000 µg/L. This short-term exposure was used to establish baseline tolerance and assess sublethal physiological responsiveness. The absence of acute mortality, together with the detection of measurable oxidative stress responses, supports the suitability of brittle stars for controlled laboratory testing and potential chronic exposure studies. Overall, this work highlights the potential of sea stars and brittle stars as emerging ecotoxicological models for investigating poorly studied contaminants within echinoderm research. Incorporating these taxa more systematically into ecotoxicological bioassay frameworks could broaden taxonomic coverage and enhance the ecological relevance of marine pollution assessments.

Enzymatic hydrolysis is one of the effective methods used to obtain the bioactive peptides from marine resources. This study aimed to evaluate effect of the enzyme type (Food Pro PNL (FP), Corolase8000 (C8), and Corolase7089 (C7)) and biomass pretreatment level (whole starfish (SF), deproteinized (DPSF) as well as deproteinized and demineralized starfish (DPDMSF)) on the hydrolysate yield, degree of hydrolysis (DH), generated peptides' molecular weight (MW), and in vitro radical scavenging and antiproliferative effects. Regardless of the enzyme used, deproteinization reduced the hydrolysate yield (<8% dw/ww) and DH (<5%), but also adding demineralization, in combination with C8, resulted in an equal yield (15%) and DH (>40%) to SF. However, the protein content of hydrolysates from DPSF and DPDMSF was higher than that prepared from SF. C8 was not effective in hydrolyzing SF but was the only effective enzyme in hydrolyzing DPDMSF. The peptides' MW distribution strongly depended on the pretreatment and enzyme type, mostly ranging from 17 to 70 kDa. Glycine content was higher in hydrolysates from DPSF and DMDPSF, indicating their collagenous nature. Hydrolysates from DPSF, rich in collagenous peptides, showed medium MW but the highest radical scavenging activity. Only SF-FP hydrolysate, rich in non-collagenous peptides, showed antiproliferative activity against melanoma cancer cells. Overall, the findings demonstrate that upstream biomass pretreatment and enzyme selection directly govern the yield and bioactivity of starfish protein hydrolysates, providing a rational basis for designing starfish protein hydrolysates with targeted functional properties.

Developmental and anatomical ontologies are fundamental tools for standardizing biological data. They facilitate the reproducibility of experiments and the integration of information across laboratories and animal species. They underpin digital curation, dissemination and analysis of diverse biological data, including gene expression patterns and phenotypes associated with pharmacological, molecular and genetic perturbations. As such, ontologies are cornerstones of model organism knowledgebases. Echinoderms have been prominent developmental biology models for more than a century and are widely used to address evolutionary questions; however, no formalized ontology has been produced for any echinoderm. Here, based on direct observations of living embryos of five species, representing euechinoids, cidaroids and sea stars, we provide developmental and anatomical ontologies for the embryogenesis of indirect-developing echinoderms. Moreover, we leverage these ontologies to create a 'pan-echinoderm' developmental and anatomical ontology, which we show will support comparative analyses across the phylum. These resources will be important for the curation of data from multiple species by Echinobase and Marimba, two public knowledgebases of echinoderm genomics and invertebrate marine models, respectively. They will greatly enhance the use and value of echinoderms as model organisms for biological research.

Introduction Artificial reefs (ARs) have been widely used to provide ecological and fisheries benefits. Quantitative evaluation of how the numbers and spatial layout of ARs affect fish responses can provide critical insights for management. Methods We used survey data from an area in the Bohai Strait (China) that has ARs deployed and developed species distribution models (SDMs) predicting the occurrence probabilities of three commercially important species ( Charybdis japonica , Sebastes schlegelii , and Hexagrammos otakii ) and one undesirable focal species ( Asterias amurensis and Asterina pectinifera combined). Three versions of SDMs were developed: a Best-fit model based on survey data, and two modified versions (Intermediate and Extreme), that incorporated increasing levels of AR-to-AR interactions, reflecting competitive and connectivity effects. A 24×24 grid with 50-m cells was populated with bottom habitat type (mud, gravel, rubble, boulder, or AR) and key environmental variables affecting occurrence probabilities. Using simulations of 10,000 randomly-generated spatial layouts of added ARs (bottom type switched to AR), we compared predicted occurrence probabilities from the Best-fit, Intermediate, and Extreme SDMs when 5, 10, 25, and 50 ARs were added to the existing ARs. Performance was evaluated using the predicted species-specific occurrence probabilities, with occurrence of the undesirable species treated inversely (i.e., lower occurrence probability indicated higher performance). Results Increasing AR numbers increased the percentage of grid cells supporting good habitat, but saturation and interference effects caused similar values for 25-50 ARs for several species, while reducing variation across spatial layouts. The three desirable species showed similar patterns with the representative layouts categorized into good and bad performing: increasing spread of good ARs on the grid with number of ARs deployed, shift of good ARs from upper to lower triangle, and an increasingly bad-performing central area with 50 ARs. The spatial overlap between high-performing cells for desirable species and elevated occurrence of undesirable Sea star illustrated an inherent trade-off that should be considered in management objectives. Discussion We conclude with a discussion of the need for AR layout-specific evaluation, consideration of AR interaction strength, broader applicability to other systems, potential pathways to expand the analysis (e.g., add hydrodynamic models), and caveats and recommendations for further development.

Disease outbreaks in wild populations worldwide can result in widespread mortality within populations, with the recovery of individuals being rare. An example of this population is the sunflower sea star Pycnopodia helianthioides o to an unidentified disease known as sea star wasting disease. Pycnopodia down control of kelp grazers in rocky reefs across the Northeastern Pacific coast. This, combined with the massive declines in kelp coverage observed during the 2015-2016 marine heat wave observed in the Northeastern Pacific, has sparked an interest in reintroducing Pycnopodia individuals on the coast to potentially assist in the recovery of the populations. However, the epidemiological implications of reintroducing healthy sea stars into the wild populations are an under-explored question. This work explores this question using a dynamical population model of Pycnopodia. We also find. This analysis provides valuable information on timing and intensity for restoring Pycnopodia populations. This article is part of the theme issue 'Managing infectious marine diseases in wild populations'.

Marine diseases are increasing globally, posing significant threats to both marine and human populations. Establishing ecosystem health baselines, detecting emerging diseases in marine wildlife and responding in time to manage an outbreak require a plan to be in place before a disease emergency unfolds. This enables monitoring and response networks to immediately begin to identify the etiologic agent, track disease progression, assess the ecological or economic risks, and prioritize the most appropriate and effective management strategies. Here, we present a marine disease outbreak contingency plan where a suspected infectious disease has caused a sudden increase in mortality of a generic marine wildlife host species, and much of the plan is also relevant for non-pathogenic mortality events and protected or economically valuable host species. The contingency plan has three sections: Diagnostics and Disease Dynamics, Ecology and Environment, and Mitigation and Remediation. Each section describes major goals and action items at different phases of an outbreak and highlights actions taken during the sea star wasting disease outbreak as a case study in disease response. We recommend strategies for increasing the overall preparedness for disease emergencies. Given our collective dependence on coastal ocean resources and the expected increase in marine disease outbreaks with climate change, we emphasize the importance of infrastructure and a network of human communities to address disease emergencies. This article is part of the theme issue 'Managing infectious marine diseases in wild populations'.

Experiments using Raman microspectroscopy and polarized light microscopy have provided evidence that cellophane undergoes biodegradation or chemical changes not only in the digestive tracts of sea urchins and periwinkles but also when exposed to the homogenized digestive organs of sea stars and sea urchins. Sea urchins (such as Strongylocentrotus intermedius) and periwinkles (Littorina brevicula) can ingest cellophane films, which are then shredded and modified in their digestive tracts, thereby increasing the content of microplastic particles in the surrounding environment. Raman microspectroscopy has shown the changes that occur in crystallinity and the thinning of plastic as it passes down the echinoderm digestive tract. This process makes the plastic more susceptible to further degradation in the marine environment.