Starfish Research Articles

Intra- and Interspecific Foraging and Feeding Interactions in Three Sea Stars and a Gastropod from the Deep Sea.

Competitive interactions come in a variety of forms and may be modulated by the size and number of individuals involved, and/or the resources available. Here, intra- and interspecific competitive behaviours for food (i.e., foraging/food search and feeding/food ingestion) were experimentally characterized and quantified in four co-existing deep-sea benthic species. Three sea stars (Ceramaster granularis, Hippasteria phrygiana, and Henricia lisa) and one gastropod (Buccinum scalariforme) from the bathyal Northwest Atlantic were investigated using video trials in darkened laboratory conditions. A range of competitive or cooperative behaviours occurred, depending on species (conspecific or heterospecific), comparative body size, and the number of individuals involved. Contrary to expectations, small individuals (or smaller species) were not always outcompeted by larger individuals (or larger species) when foraging and feeding. Moreover, faster species did not always outcompete slower ones while scavenging. Overall, this study sheds new light on scavenging strategies of co-existing deep-sea benthic species in food-limited bathyal environments, based on complex behavioural inter- and intraspecific relationships.

Comprehensive Lipid Profile of Eight Echinoderm Species by RPLC-Triple TOF-MS/MS.

Echinoderms are of broad interest for abundant bioactive lipids. The comprehensive lipid profiles in eight echinoderm species were obtained by UPLC-Triple TOF-MS/MS with characterization and semi-quantitative analysis of 961 lipid molecular species in 14 subclasses of 4 classes. Phospholipids (38.78-76.83%) and glycerolipids (6.85-42.82%) were the main classes in all investigated echinoderm species, with abundant ether phospholipids, whereas the proportion of sphingolipids was higher in sea cucumbers. Two sulfated lipid subclasses were detected in echinoderms for the first time; sterol sulfate was rich in sea cucumbers, whereas sulfoquinovosyldiacylglycerol existed in the sea star and sea urchins. Furthermore, PC(18:1/24:2), PE(16:0/14:0), and TAG(50:1e) could be used as lipid markers to distinguish eight echinoderm species. In this study, the differentiation of eight echinoderms was achieved by lipidomics and revealed the uniqueness of the natural biochemical fingerprints of echinoderms. The findings will help evaluate the nutritional value in the future.

Genetic diversity and population structure of the sea star Asterias amurensis in the northern coast of China

Genetic diversity and population structure of the sea star Asterias amurensis in the northern coast of China

Molecular mechanisms of tubulogenesis revealed in the sea star hydro-vascular organ

A fundamental goal in the organogenesis field is to understand how cells organize into tubular shapes. Toward this aim, we have established the hydro-vascular organ in the sea star Patiria miniata as a model for tubulogenesis. In this animal, bilateral tubes grow out from the tip of the developing gut, and precisely extend to specific sites in the larva. This growth involves cell migration coupled with mitosis in distinct zones. Cell proliferation requires FGF signaling, whereas the three-dimensional orientation of the organ depends on Wnt signaling. Specification and maintenance of tube cell fate requires Delta/Notch signaling. Moreover, we identify target genes of the FGF pathway that contribute to tube morphology, revealing molecular mechanisms for tube outgrowth. Finally, we report that FGF activates the Six1/2 transcription factor, which serves as an evolutionarily ancient regulator of branching morphogenesis. This study uncovers distinct mechanisms of tubulogenesis in vivo and we propose that cellular dynamics in the sea star hydro-vascular organ represents a key comparison for understanding the evolution of vertebrate organs.

Sea Star Wasting Disease in captive common sea stars (Asterias rubens): Examinations, therapy attempts and course of disease

Sea Star Wasting Disease (SSWD) affects several wild and captive starfish species. It is generally thought to be infectious, with environmental conditions favouring its progression. Captive Asterias rubens with varying degrees of epidermal ulceration, limb autotomy and eversion of viscera were examined. Antibiotic treatments by injections and baths did not reduce mortality.

Lethal and sublethal implications of low temperature exposure for three intertidal predators

Benthic invertebrate predators play a key role in top-down trophic regulation in intertidal ecosystems. While the physiological and ecological consequences of predator exposure to high temperatures during summer low tides are increasingly well-studied, the effects of cold exposure during winter low tides remain poorly understood. To address this knowledge gap, we measured the supercooling points, survival, and feeding rates of three intertidal predator species in British Columbia, Canada — the sea stars Pisaster ochraceus and Evasterias troschelii and the dogwhelk Nucella lamellosa — in response to exposure to sub-zero air temperatures. Overall, we found that all three predators exhibited evidence of internal freezing at relatively mild sub-zero temperatures, with sea stars exhibiting an average supercooling point of −2.50 °C, and the dogwhelk averaging approximately −3.99 °C. None of the tested species are strongly freeze tolerant, as evidenced by moderate-to-low survival rates after exposure to −8 °C air. All three predators exhibited significantly reduced feeding rates over a two-week period following a single 3-h sublethal (−0.5 °C) exposure event. We also quantified variation in predator body temperature among thermal microhabitats during winter low tides. Predators that were found at the base of large boulders, on the sediment, and within crevices had higher body temperatures during winter low tides, as compared to those situated in other microhabitats. However, we did not find evidence of behavioural thermoregulation via selective microhabitat use during cold weather. Since these intertidal predators are less freeze tolerant than their preferred prey, winter low temperature exposures can have important implications for organism survival and predator-prey dynamics across thermal gradients at both local (habitat-driven) and geographic (climate-driven) scales.

Nonconsumptive Effects of Crustaceans and an Echinoderm on Spat of the Eastern Oyster Crassostrea virginica (Gmelin, 1791)

Predation by crustaceans and echinoderms is a significant driver of mortality for sessile invertebrates in near-shore marine ecosystems. As a response, shellfish growers use predator exclusion cages to grow their product. Oysters grown in these cages and clams in and under nets have been observed to exhibit thinner, brittle shells, which is not optimal for market, nor for those being grown for restoration purposes. Here, the nonconsumptive predator effects of several native and nonnative predators on shell morphology of Crassostrea virginica oyster spat. Juvenile (1–3 mm) seed oysters were exposed separately to chemical cues of five different predators and one nonpredator crab were investigated and compared with control (no exposure) spat. Significant effects of predator presence on the total wet weight (g) of the spat was demonstrated, with the highest increase for spat exposed to black-fingered mud crabs (Panopeus, 1.70 mg d–1) and the biggest decreases for spat exposed to the European green crabs (Carcinus maenas—1.34 mg d–1) and the sea stars (Asterias rubens—1.47 mg d–1). Changes to oyster length (mm) and shell density (crushing resistance) were not significant. Implications for aquaculturists and wild bivalve populations are that growth could be negatively affected by the lack of predators on these important organisms.

Community-managed coral reef restoration in southern Kenya initiates reef recovery using various artificial reef designs

Monitoring of reef restoration efforts and artificial reefs (ARs) has typically been limited to coral fragment survival, hampering evaluation of broader objectives such as ecosystem recovery. This study aimed to determine to what extent AR design influences the ecological recovery of restored reefs by monitoring outplanted coral fragments, benthic cover, coral recruitment and fish and invertebrate communities for two years. Four AR designs (16 m2), unrestored controls and natural reef patches as reference (n = 10) were established in Mkwiro, Kenya. ARs consisted either of concrete disks with bottles, layered concrete disks, metal cages or a combination thereof. A mixture of 18 branching coral species (mainly Acropora spp.) was outplanted on ARs at a density of 7 corals m-2. After two years, 60% of all outplanted fragments had survived, already resulting in coral cover on most ARs comparable (though Acropora-dominated) to reference patches. Coral survival differed between ARs, with highest survival on cages due to the absence of crown-of-thorns sea star predation on this design. In total, 32 coral genera recruited on ARs and recruit densities were highest on reference patches, moderate on concrete ARs and low on cages. ARs and reference patches featured nearly twice the fish species richness and around an order of magnitude higher fish abundance and biomass compared to control patches. Fish abundance and biomass strongly correlated with coral cover on ARs. AR, reference and control patches all had distinct fish species compositions, but AR and reference patches were similar in terms of trophic structure of their fish communities. Motile invertebrates including gastropods, sea urchins, sea cucumbers and sea stars were present at ARs, but generally more abundant and diverse at natural reference patches. Taken together, all studied ecological parameters progressed towards reef ecosystem recovery, with varying influences of AR design and material. We recommend a combination of metal cages and layered concrete ARs to promote high fragment survival as well as natural coral recruitment. Ultimately, a longer period of monitoring is needed to fully determine the effectiveness reef restoration as conservation tool to support coral reef ecosystem recovery.

Predators regulate the taxonomic structure of mixed Mytilus edulis L. and M.trossulus Gould settlements in the shallow waters of the White Sea

Cryptic mussel species Mytilus edulis (Me) and M.trossulus (Mt) form mixed settlements in shallow waters of the White Sea. The proportion of Mt and Me in local settlements varies in broad limits but the factors regulating taxonomic composition of mixed populations are poorly understood. Present study focuses on the assessment of the sea star (Asterias rubens) predation influence on the Mt-Me ratio in natural habitats. For this purpose, we’ve conducted a series of field experiments. For mussels placed on experimental units (ceramic plates submerged in starfish-infested habitats), we’ve estimated a probability of being eaten by starfish. We’ve constructed a linear model that includes several predictors which may influence the probability of being eaten (starfish biomass, mussel size, mussel species, prey abundance, Mt-Me ratio on experimental units and abundance of conspecifics). The analysis has revealed that the probability of being eaten expectedly increases with sea stars’ biomass increasing, but it is higher for Mt in comparison with Me. This indicates Mt as a preferable prey. Negative correlations between the probability of being eaten and shell size, number of conspecifics and mussel abundance were also revealed. No significant dependence on Mt-Me ratio was found. Additionally, we’ve taken field samples which revealed a significant decrease in the proportion of Mt in mussel patches after a massive starfish attack. This indicates that starfish ate out Mt as its preferable prey. These results show that predators can contribute to the regulation of taxonomic composition of mixed Mt-Me settlements in the White Sea.

Microbial dysbiosis precedes signs of sea star wasting disease in wild populations of Pycnopodia helianthoides

Sea star wasting (SSW) disease, a massive and ongoing epidemic with unknown cause(s), has led to the rapid death and decimation of sea star populations with cascading ecological consequences. Changes in microbial community structure have been previously associated with SSW, however, it remains unknown if SSW-associated dysbiosis is a mechanism or artifact of disease progression, particularly in wild populations. Here, we compare the microbiomes of the sunflower sea star, Pycnopodia helianthoides, before (Naïve) and during (Exposed and Wasting) the initial outbreak in Southeast Alaska to identify changes and interactions in the microbial communities associated with sea star health and disease exposure. We found an increase in microbial diversity (both alpha and beta diversity) preceding signs of disease and an increase in abundance of facultative and obligate anaerobes (most notably Vibrio) in both Exposed (apparently healthy) and Wasting animals. Complementing these changes in microbial composition was the initial gain of metabolic functions upon disease exposure, and loss of function with signs of wasting. Using Bayesian network clustering, we found evidence of dysbiosis in the form of co-colonization of taxa appearing in large numbers among Exposed and Wasting individuals, in addition to the loss of communities associated with Naïve sea stars. These changes in community structure suggest a shared set of colonizing microbes that may be important in the initial stages of SSW. Together, these results provide several complementary perspectives in support of an early dysbiotic event preceding visible signs of SSW.

Exploring the Effects of Varying Retinol Vitamin A Concentrations on Tissue Regeneration in the Species Asterina coronata

The following study will look at the relationship between tissue and regeneration rate in the sea star species Asterina and retinol vitamin A. The overall purpose of the study is to evaluate whether concentrations of retinol vitamin A will produce a positive, negative, or null effect on the tissue regeneration in Asterina coronata. After amputation of the ray, 48 sea stars were subjected to four different retinol vitamin A concentration levels for sixteen hours and observed over a thirty-to-forty-day time period. The results show that the second highest concentration group produced the most consistent and noticeable growth. Moreover, the highest concentration group showed the second highest rate compared with the lowest concentration group and the control. Through these results, it can be concluded that retinol vitamin A does support tissue regeneration in Asterina coronata to a limit before it begins a negative feedback. The findings in this study add to an understanding of the mechanisms behind cell differentiation and whether stem cells involving tissue regeneration can be activated with the treatment of vitamin A. Hopefully the connections made in this paper can impact current research on human stem cell therapy itself, and the topic of whether sea stars can be made into viable stem cell therapy models.

CubeSats show persistence of bull kelp refugia amidst a regional collapse in California

Bull kelp populations in northern California declined drastically in response to the 2014–2016 marine heatwave, sea star wasting disease, and subsequently large increases in herbivorous purple urchin populations. Despite the regional kelp forest collapse, there were small, remnant populations where bull kelp was able to survive. Moderate resolution satellites (i.e., Landsat) have been important for creating long-term, large-scale time series of bull kelp forests, however, these have been shown to underestimate or entirely exclude refugia due to their low densities and proximity to the coastline. While measurements from Unoccupied Aerial Vehicles (UAV) are spatially detailed, they are temporally limited and difficult to collect over regional scales. The development of CubeSat constellations has enabled a workaround for these tradeoffs, with global imagery available near-daily at meter-scale.We developed a method for mapping bull kelp canopy across the different sensor cohorts in the PlanetScope constellation. This required correcting surface reflectance measurements to account for differences in the spectral response functions among the sensors and leveraging the temporal frequency of PlanetScope data to increase the automation of classifying kelp canopy in imagery with increased noise. Using the PlanetScope derived kelp canopy extents, we identified locations where bull kelp refugia have persisted in northern California. We found that bull kelp refugia occupied about 2% of the total available habitat in the region and about 9.4% of the average canopy area observed prior to 2014. These areas may be critical to the success of kelp forest re-establishment in northern California, which increases their importance for ongoing monitoring, conservation, and restoration efforts.

High-throughput segmentation, data visualization, and analysis of sea star skeletal networks

The remarkably complex skeletal systems of the sea stars (Echinodermata, Asteroidea), consisting of hundreds to thousands of individual elements (ossicles), have intrigued investigators for more than 150 years. While the general features and structural diversity of isolated asteroid ossicles have been well documented in the literature, the task of mapping the spatial organization of these constituent skeletal elements in a whole-animal context represents an incredibly laborious process, and as such, has remained largely unexplored.To address this unmet need, particularly in the context of understanding structure–function relationships in these complex skeletal systems, we present an integrated approach that combines micro-computed tomography, automated ossicle segmentation, data visualization tools, and the production of additively manufactured tangible models to reveal biologically relevant structural data that can be rapidly analyzed in an intuitive manner.In the present study, we demonstrate this high-throughput workflow by segmenting and analyzing entire skeletal systems of the giant knobby star, Pisaster giganteus, at four different stages of growth. The in-depth analysis, presented herein, provides a fundamental understanding of the three-dimensional skeletal architecture of the sea star body wall, the process of skeletal maturation during growth, and the relationship between skeletal organization and morphological characteristics of individual ossicles.The widespread implementation of this approach for investigating other species, subspecies, and growth series has the potential to fundamentally improve our understanding of asteroid skeletal architecture and biodiversity in relation to mobility, feeding habits, and environmental specialization in this fascinating group of echinoderms.

A New Hope? Mediterranean Algae Mats Are Thriving With Life

Our oceans are full of life and home to many different species. High species diversity often concentrates in specific areas called “biodiversity hotspots” (e.g., coral reefs). These hotspots develop with the help of a few key engineering species (e.g., corals). In the Mediterranean Sea, well-known biodiversity hotspots are seagrass meadows. Macroalgae beds represent another typical habitat but usually do not provide the same diversity as seagrass meadows. High biodiversity is essential for an ecosystem’s stability and our lives: healthy coastal ecosystems provide food and shelter for fish species and stabilize the seafloor. We investigated a relatively unknown type of red macroalgae and were surprised to find it thriving with marine organisms such as sea stars, anemones, and tube worms. With the latter being an example of an extraordinary group of marine animals, we would like to take this example and show you what we learned about this new hotspot for diversity.

How to assess the absence of a species? A revision of the geographical range of the horned sea star, Protoreaster nodosus (Echinodermata; Asteroidea)

Demonstrating the absence of a species has always been a challenge for natural sciences, which are more used to documenting their presence; however, both forms of data are of equal scientific significance. The horned sea star Protoreaster nodosus is said, in the scientific literature, to be present throughout the whole Indo-Pacific region, from eastern Africa to the Pacific Ocean islands. However, a review of the scientific literature, along with a critical bibliographical study, citizen science surveys, web-based pictures analyses, and field studies suggests that the presence of this species could instead be restricted to the western Pacific Ocean, from Thailand to Samoa and from Japan to New Caledonia, with no reliable record in the Indian Ocean. Such a huge and long-running mistake on a very common and conspicuous species exemplifies the importance of a critical approach towards species distribution data, which appears too often based on layers of reproduction of never-reassessed data, turning hypotheses into commonly shared truth.

Antibacterial potential of Luidia clathrata (sea star) tissue extracts against selected pathogenic bacteria.

As resistance to traditional antibiotics has become a major issue, it is essential to explore natural sources for new antimicrobial agents. The marine environment offers a variety of natural bioactive compounds. In this study, we examined the antibacterial potential of Luidia clathrata, a tropical sea star species. The experiment was conducted against both gram-positive (Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus, Bacillus cereus and Mycobacterium smegmatis) and gram-negative (Proteus mirabilis, Salmonella typhimurium, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae) bacteria using disk diffusion method. Specifically, we extracted the body wall and gonad using methanol, ethyl acetate, and hexane. Our findings show that the body wall extract using ethyl acetate (1.78μg/ml) was particularly effective against all tested pathogens, while the gonad extract (0.107μg/ml) showed activity against six out of ten selected pathogens. This is a crucial and new discovery that suggests L. clathrata may be a useful source for discovering antibiotics and more research is required to pinpoint and comprehend the active ingredients.

Welcome Matt and farewell Ken.

Welcome Matt and farewell Ken.

Sunflower sea star predation on urchins can facilitate kelp forest recovery.

The recent collapse of predatory sunflower sea stars (Pycnopodia helianthoides) owing to sea star wasting disease (SSWD) is hypothesized to have contributed to proliferation of sea urchin barrens and losses of kelp forests on the North American west coast. We used experiments and a model to test whether restored Pycnopodia populations may help recover kelp forests through their consumption of nutritionally poor purple sea urchins (Strongylocentrotus purpuratus) typical of barrens. Pycnopodia consumed 0.68 S. purpuratus d-1, and our model and sensitivity analysis shows that the magnitude of recent Pycnopodia declines is consistent with urchin proliferation after modest sea urchin recruitment, and even small Pycnopodia recoveries could generally lead to lower densities of sea urchins that are consistent with kelp-urchin coexistence. Pycnopodia seem unable to chemically distinguish starved from fed urchins and indeed have higher predation rates on starved urchins owing to shorter handling times. These results highlight the importance of Pycnopodia in regulating purple sea urchin populations and maintaining healthy kelp forests through top-down control. The recovery of this important predator to densities commonly found prior to SSWD, whether through natural means or human-assisted reintroductions, may therefore be a key step in kelp forest restoration at ecologically significant scales.

Giant Kelp Forest Resilience to Ocean Warming; Historical and Modern Systems

Giant kelp forests of the North Pacific are iconic among cool temperate marine communities. They are also amongst the most productive marine ecosystems, harboring significant biodiversity and supporting coastal economies. The fate of these systems over the next eight decades is uncertain, given the variance of outcomes for global warming scenarios and the complexities of ecological forecasting. There is a growing consensus that giant kelp will be susceptible to warming, leading to a decline of the communities. Kelp forest dynamics, however, are also controlled by biotic interactions. In the North Pacific, the main biotic factors today are kelp herbivory, especially by grazing sea urchins, and predatory control of the urchins, particularly by sea otters and sunflower sea stars. A recent study demonstrated that as late as the 18th century, the now extinct mega herbivore Steller’s sea cow, an obligate kelp browser, had a significant impact on North Pacific kelp forest dynamics. Mathematical models comparing the historical community to modern ones indicated that the sea cow would have increased forest resilience against reductions of predation of urchins caused by multiple types of perturbation. In addition to epidemics and temperature anomalies, it is expected that global temperatures will increase 2-4 degrees Celsius by the year 2100. Here we use the mathematical models to explore forest dynamics under various warming scenarios, including the changing impacts of epidemics and the frequency and intensity of warming anomalies. Preliminary results suggest that in contrast to a stable temperature regime, warming to 4 degrees increases chaotic dynamics, extinction of both sea urchins and sunflower sea stars, and abundance of understory algae. Those results also suggest that chaos and algal increase would be lessened in the presence of the extinct herbivore. These findings bear implications for future kelp forest management, conservation, and human economic exploitation.

Diversity of Sea Stars (Asteroidea) in Baluran National Park Bilik Beach Intertidal Zone As a Source of Learning Biology

Starfish (Asteroidea) is one of the biota that make up Bilik Beach, Baluran National Park. The aim of the research was to determine the diversity of starfish species (Asteroidea) in the intertidal zone of Bilik Beach, Baluran National Park, Situbondo Regency, East Java. The research method used is survey method. Data collection was carried out by site surveys, determining research locations, sampling, observing, and identifying species. Sampling was carried out when the seawater reached its maximum ebb. The research location uses 3 stations with location points that represent the area of Bilik Beach. Sampling used transect plotting technique with a total of 3 transects at each station. Based on the research results, 2 types of starfish (Asteroidea) were found, namely Linckia laevigata and Archaster typicus. The results of the calculation of the diversity index of starfish (Asteroidea) found on Bilik Beach are 0.44 which is relatively low. The findings of sea stars are used as a learning resource in the form of popular scientific books.