Autotomy reduces feeding, energy storage and growth of the sea star Stichaster striatus

We evaluated the effect of autotomy on feeding, energy storage and growth of juvenile Stichaster striatus kept in the laboratory for five months with a limited supply of the mussel Semimytilus algosus. Autotomy strongly decreased feeding, energy storage and growth. Intact juveniles showed a ∼ 3 fold higher feeding rate than autotomized individuals throughout the experiment. Intact juveniles also had a higher (∼ 5 fold) energy content per pyloric caeca in each arm. This was mainly due to higher lipid content, the main proximate constituent of pyloric caeca. Intact juveniles showed a greater growth rate and reached a greater size than autotomized individuals, more evident for underwater mass than radius length. The reduced capacity to feed reduced energy intake in autotomized individuals. However, low energy reserves along with low growth in autotomized sea stars, support the hypothesis that juveniles of this species allocate energy to regeneration to the detriment of growth. This was also supported by the ∼ 25% of arm length regeneration after 5 mo. Remaining small could increase risk of lethal predation, however, S. striatus may reduce predation risk by using crevices and kelp holdfasts as refuges from predators. Given the strong impact of autotomy on feeding, regeneration of arms to recover full capacity to forage and grow seems a better strategy for juvenile S. striatus, than merely growing.     

Responses of the black sea urchin Tetrapygus niger to its sea-star predators Heliaster helianthus and Meyenaster gelatinosus under field conditions

We ran field experiments to examine the responses of the black sea urchin Tetrapygus niger to predatory sea stars. Trials involving simulated attacks (one or several arms of a sea star being placed on top of half the urchin) showed that the urchin differentiated between the predatory sea stars, Heliaster helianthus and Meyenaster gelatinosus, and a non-predatory sea star, Stichaster striatus, and showed almost no response to a sea star mimic. We further compared the responses of the urchin to different threat levels presented by the two predatory sea stars. The highest threat level was a simulated attack, then mere contact, and subsequently sea stars being placed at different distances from the urchin. All urchins responded to simulated attacks and contact with both sea stars. The proportion responding decreased with distance and more rapidly in trials with H. helianthus (0% at a distance of 30 cm) than with M. gelatinosus (33% at a distance of 50 cm). At each of the threat levels where there was a response to both sea stars, the urchins responded more rapidly to M. gelatinosus than to H. helianthus. In a third experiment where a predatory sea star was added to a circular area (1-m diameter) in which either 4-8 or 11-19 undisturbed urchins were present, the urchins fled the area more rapidly when the added sea star was M. gelatinosus, but the rate of fleeing did not vary with density, as might occur if there was communication among urchins using alarm signals. Our observations suggest that M. gelatinosus presents a stronger predatory threat than H. helianthus. This corresponds to field observations showing that the urchins are more frequently consumed by M. gelatinosus. These are the first field experiments demonstrating distance chemodetection by a marine invertebrate under back-and-forth water flow from wave activity.     

The biochemical composition, energy content, and chemical antifeedant defenses of the common Antarctic Peninsular sea stars Granaster nutrix and Neosmilaster georgianus

The sea stars Granaster nutrix and Neosmilaster georgianus are conspicuous members of benthic communities along the Antarctic Peninsula. An analysis of the proximate composition of somatic body components of nonreproductive adults indicates the nutrient storage organs (pyloric caeca) are rich in both protein (60.7 and 60.6% mean dry wt, respectively) and lipid (25.4 and 29.8% mean dry wt, respectively). Body-wall tissues, while containing small inconspicuous skeletal ossicles, are also comprised of significant levels of organic matter (33.5 and 55.7% mean dry wt, respectively), attributable primarily to protein. Both the pyloric caeca and body-wall tissues are relatively rich in energy (mean energy levels=24.8 and 26.5 kJ g⁻¹ dry wt; 8.4 and 14.1 kJ g⁻¹ dry wt, respectively). Despite the availability of these nutrients and energy neither sea star is preyed upon by the sympatric omnivorous sea star Odontaster validus, a common predator of other Antarctic sea stars. Laboratory feeding bioassays indicate that O. validus rejects live intact individuals and body-wall tissues of both sea star species while readily consuming dried krill. Alginate food pellets containing a krill powder and tissue level concentrations of organic methanol extracts of body-wall tissues were also rejected by O. validus. Moreover, the copious mucus released from the body wall of N. georgianus was deterrent in O. validus food pellet bioassays. Thus, both sea stars evidently possess defensive secondary metabolites that defend against predation and are likely to play a role in mediating materials and energy transfer in the Antarctic benthos.     

Regenerative capacity and biochemical composition of the sea star Luidia clathrata (Say) (Echinodermata: Asteroidea) under conditions of near-future ocean acidification

The present study examines sublethal effects of near-future (year 2100) ocean acidification (OA) on regenerative capacity, biochemical composition, and behavior of the sea star Luidia clathrata, a predominant predator in sub-tropical soft-bottom habitats. Two groups of sea stars, each with two arms excised, were maintained on a formulated diet in seawater bubbled with air alone (pH 8.2, approximating a pCO₂ of 380 μatm) or with a controlled mixture of air/C0₂ (pH 7.8, approximating a pCO₂ of 780 μatm). Arm length, total body wet weight, and righting responses were measured weekly. After 97 days, a period of time sufficient for 80% arm regeneration, pyloric caecal indices, and protein, carbohydrate, lipid, and ash levels were determined for body wall and pyloric caecal tissues of intact and regenerating arms of individuals held in both seawater pH treatments. The present study indicates that predicted near-term levels of ocean acidification (seawater pH 7.8) do not significantly impact whole animal growth, arm regeneration rates, biochemical composition, or righting behavior in this common soft bottom sea star.     

Allocation of pyloric caecum reserves in FED and starved sea stars, Pisaster giganteus (Stimpson): somatic maintenance comes before reproduction

Pyloric caeca were removed through the raytips of sea stars, Pisaster giganteus (Stimpson), beginning their seasonal period of gonad growth. Four months later their feeding rate, gonad growth, and gametogenic activity were lower than those of intact animals, while body growth rate remained the same. Removal of only the raytips also depressed feeding rate and gonad growth. When sea stars were starved, gonad growth and gametogenic activity were lower in animals without pyloric caeca, but body weight loss was the same as in intact animals. We conclude that when food is abundant, materials are utilized to enhance somatic and gonad growth. With decreasing reserves, due either to reduced food intake and/or pyloric caecum removal, somatic maintenance and growth have priority over gonad growth in material and energy allocation. Such a pattern of resource allocation is appropriate for long-lived iteroparous animals, such as these sea stars.     

Ontogeny of gene expression of group IB phospholipase A₂ isoforms in the red sea bream, Pagrus (Chrysophrys) major

The red sea bream (Pagrus major) was previously found to express mRNAs for two group IB phospholipase A₂ (PLA₂) isoforms, DE-1 and DE-2, in the digestive organs, including the hepatopancreas, pyloric caeca, and intestine. To characterize the ontogeny of the digestive function of these PLA₂s, the present study investigated the localization and expression of DE-1 and DE-2 PLA₂ genes in red sea bream larvae/juveniles and immature adults, by in situ hybridization. In the adults, DE-1 PLA₂ mRNA was expressed in pancreatic acinar cells. By contrast, DE-2 PLA₂ mRNA was detected not only in digestive tissues, such as pancreatic acinar cells, gastric glands of the stomach, epithelial cells of the pyloric caeca, and intestinal epithelial cells, but also in non-digestive ones, including cardiac and lateral muscle fibers and the cytoplasm of the oocytes. In the larvae, both DE-1 and DE-2 PLA₂ mRNAs first appeared in pancreatic tissues at 3 days post-hatching (dph) and in intestinal tissue at 1 dph, and expression levels for both gradually increased after this point. In the juvenile stage at 32 dph, DE-1 PLA₂ mRNA was highly expressed in pancreatic tissue, and DE-2 PLA₂ mRNA was detected in almost all digestive tissues, including pancreatic tissue, gastric glands, pyloric caeca, and intestine, including the myomere of the lateral muscles. In conclusion, both DE-1 and DE-2 PLA₂ mRNAs are already expressed in the digestive organs of red sea bream larvae before first feeding, and larvae will synthesize both DE-1 and DE-2 PLA₂ proteins.     

The reproductive cycle of the asteroid Coscinasterias muricata in Port Phillip Bay, Victoria, Australia

The reproductive cycles of two populations of Coscinasterias muricata from Port Phillip Bay, Victoria, Australia are described in terms of organ indices, oocyte development and progesterone levels. Both Governor's Reef and South Channel Fort populations exhibited clearly defined reproductive cycles with two spawning periods, during summer and during spring. In both populations, the pyloric caecal index and gonadal index showed inverse cycles suggesting nutrient translocation from the pyloric caeca to the gonads for gametogenesis. Physiological changes, such as decreases in pyloric caecal index, and increases in gonadal index and oocyte diameter were observed following the months of increased progesterone concentrations in the female pyloric caeca. These results indicate a role for this steroid in the reproductive cycle. The results from the Governor's Reef population suggest that the influence of progesterone on the reproductive cycle of female C. muricata is regulated by photoperiod. Results also provide evidence of a role for seawater temperature in the reproductive process of this species.     

Nature and role of newly described symbiotic associations between a sea anemone and gastropods at bathyal depths in the NW Atlantic

The hormathiid sea anemone Allantactis parasitica was found living as an epibiont on numerous species of gastropods at depths of 725-1100 m along the continental slope of eastern Canada. The proportion of bathyal gastropods hosting 1-6 sea anemones reached 72.5% in a single trawl. Although A. parasitica was occasionally found on other substrata (i.e. empty shells, pebbles), laboratory trials confirmed that they preferably associate with living gastropods. Settlement of planula larvae occurred significantly more often on the shells of live bathyal gastropods than on all other substrata present in the tanks. Juvenile sea anemones (∼ 1 mm diameter) readily moved from the mud or other inert substrata onto shells of burrowed bathyal gastropods. Conversely, larvae, juveniles and adults of A. parasitica never associated with any shallow-water gastropods when given the opportunity. Trials exposing predatory sea stars (Leptasterias polaris) from shallow and bathyal depths to bathyal gastropods (Buccinum undatum) with epibiotic A. parasitica, and to asymbiotic bathyal and shallow-water B. undatum, revealed adaptive behaviours in both prey and predator. Shallow-water gastropods (devoid of epibionts) reacted defensively to L. polaris, whereas bathyal gastropods relied mostly on their epibionts to protect them, thus falling prey to L. polaris when the epibionts were removed. L. polaris from bathyal depths typically ignored symbiotic gastropods, but they consistently preyed on asymbiotic ones, while L. polaris from shallow areas initially attempted to prey on all gastropods, but learned to avoid those harbouring sea anemones. Furthermore, living as epibionts afforded sea anemones a means to escape one of their own predators, the sea star Crossaster papposus. The mutualistic relationship between hormathiid sea anemones and bathyal gastropods from the NW Atlantic may have evolved in response to predation pressure.     

Scales of detection and escape of the sea urchin Tetrapygus niger in interactions with the predatory sun star Heliaster helianthus

Predators can simultaneously have lethal (consumption) and non-lethal (modification of traits) effects on their prey. Prey escape or fleeing from potential predators is a common form of a non-lethal predator effect. The efficiency of this response depends on the prey's ability to detect and correctly identify its predator far enough to increase the probability of successful escape, yet short enough to allow it to allocate time to other activities (e.g. foraging). In this study, we characterized the non-lethal effect of the sun star Heliaster helianthus on the black sea urchin Tetrapygus niger by assessing the nature of predator detection and the spatial scale involved both in predator detection and in the escape response. Through field and laboratory experiments we demonstrate that T. niger detects chemical cues released by H. helianthus. In the laboratory, these chemical signals can be detected at distances of up to about 50 cm. In the field, the distance traveled by urchins when escaping, after recognition of the predation risk, was also restricted to about 40 cm. Thus, considering the sizes of the predator and prey, the spatial scale of both detection and escape is comparatively small suggesting that non-lethal effects of H. helianthus (e.g. how it modifies the behavior of T. niger) should be important at local spatial scales and highly variable at the landscape scale.     

Level,content, and caloric equivalents of the lipid,carbohydrate, and protein in the body components of Luidia clathrata (echinodermata: asteroidea: platyasterida) in Tampa bay

The body components of the primitive platyasterid starfish, Luidia clathrata (Say) have been characterized according to season, reproductive, and nutritional condition. The animal has been ‘reconstructed’ in terms of the wet and dry weights, the weight of organic matter, and the caloric equivalents of the body components in early summer (when there are no gonads and the pyloric caeca are small), in autumn (just prior to initiation of gonadal development and at maximal caeca size), and in early spring (at maximal gonad size). The body wall is always the most significant component in terms of wet and dry weights. In terms of organic matter and calories, the pyloric caeca are the most significant compartment in the fall and, together with the gonads, in the spring. On starvation for one month, the decrease in the size of the pyloric caeca is calculated to have produced 2.048 kcal. The energy requirement over the period, calculated from Q_o2 values, is 2.112 kcal. There was no change in biochemical composition of the pyloric caeca with starvation, suggesting that energy production came about through cell destruction rather than preferential utilization of cellular nutrient stores. Lack of extreme change in the composition of the pyloric caeca with size through the year also suggests that energy deposition in the organ is primarily by change in cell number and not by cell size.     

Biochemical content, energy composition and reproductive effort in the broadcasting sea star Asterias vulgaris over the spawning period

To assess sex differences in reproductive effort, we examined the biochemical composition and energetic content of the principal body components of the broadcast spawning sea star Asterias vulgaris in the Mingan Islands in the northern Gulf of St. Lawrence, eastern Canada. The body wall was the most stable body component, showing no variations in mass or in lipid and protein content (and total energetic content) between sexes or during spawning. Patterns in the gonads differed between sexes and with spawning. The lipid, protein and carbohydrate content of the ovary dropped during spawning, while only the protein content of the testis decreased significantly. Reproductive effort, expressed as loss of energy in the gonads during spawning for an individual weighing 10 g in underwater mass (8.2 cm in radius), was six times greater in females (49.5 kJ) than males (7.9 kJ). The energetic content of the pyloric caeca also decreased during spawning, by 17.7 kJ in females and 21.5 kJ in males, mainly due to a decrease in lipids. If this decrease is included as reproductive effort, it lessens the gender difference. The caecum decrease possibly represented expenditures due to formation of aggregations or the expulsion of gametes during spawning. Effectively, we observed aggregations during a massive spawning in this population. The sex ratio did not differ from 1:1 in all size classes sampled. This suggests that, unless males suffer higher mortality, females manage to allocate as much energy to somatic growth as males, possibly by feeding at higher rates to compensate for their higher reproductive effort. Stomach protein content tended to be higher in females than males and may indicate greater muscular development to facilitate digestion.     

A non‐lethal method for estimation of gonad and pyloric caecum indices in sea stars

Abstract. Gonad and pyloric caecum indices are widely used indicators of reproductive effort and nutritional condition in asteroids. Current methods of quantification generally require sacrificing multiple animals and the resulting reduction in local sea star density could have an unintended impact on benthic communities. Using the intertidal sea star Pisaster ochraceus, we developed and tested a method for estimating organ indices through the non‐lethal sampling of single arms. Indices estimated via dissections of single arms accurately predicted the values obtained by sacrificing whole animals. In laboratory and field trials, we compared two methods of sampling single arms: (1) arm removal, and (2) organ extraction through an incision (without arm removal). Two years after these treatments, organs had regenerated in the affected arms of most sea stars, but were small relative to those in unmanipulated arms. The extent of organ recovery did not differ between the two treatments, but sea stars in the arm removal group were relocated in the field more frequently than those in the arm incision group. Our results suggest that sampling via the removal of single arms can be an effective, non‐lethal method for estimating gonad and pyloric caecum indices in asteroids.     

Effects of substrate on interactions between juvenile sea scallops (Placopecten magellanicus Gmelin) and predatory sea stars (Asterias vulgaris Verrill) and rock crabs (Cancer irroratus Say)

We investigated the effect of substrate (glass bottom, sand, granule, pebble) on predation of juvenile sea scallops (Placopecten magellanicus) by sea stars (Asterias vulgaris) and rock crabs (Cancer irroratus) at two prey sizes (11-15 mm and 24-28 mm shell height), and two prey densities (10 and 30 scallops per aquarium) in laboratory experiments. Specifically, we quantified predation rate and underlying behaviours (proportion of time a predator spent searching for and handling prey, encounter rate between predators and prey, and various outcomes of encounters). We detected a significant gradual effect of particle size of natural substrates on sea star predation: specifically, predation rate on and encounter rate with small scallops tended to decrease with increasing particle size (being highest for sand, intermediate for granule, and lowest for pebble). Substrate type did not significantly affect predation rates or behaviours of sea stars preying on large scallops or of rock crabs preying on either scallop size classes. Other factors, such as prey size and density, were important in the scallop-sea star and scallop-rock crab systems. For example, predation rate by sea stars and crabs and certain sea star behaviours (e.g. probability of consuming scallops upon capture) were significantly higher with small scallops than with large scallops. As well, in interactions between small scallops and sea stars, predation rate and encounter rate increased with prey density, and the proportion of time sea stars spent searching was higher at low prey density than high prey density. Thus, substrate type may be a minor factor determining predation risk of seeded scallops during enhancement operations; prey size and prey density may play a more important role. However, substrate type still needs to be considered when choosing a site for scallop enhancement, as it may affect other scallop behaviours (such as movement).     

The feeding, growth, and energetics of two rocky intertidal predators (Pisaster ochraceus and Nucella canaliculata) under water temperatures simulating episodic upwelling

Although most upwelling regions are marked by strong fluctuations in water temperature, few studies have examined how episodic cold-water events affect the physiology and ecology of benthic marine invertebrates. I tested the hypothesis that upwelling-related variation in water temperature regulates the feeding, growth, and energetics of two rocky intertidal predators, the sea star Pisaster ochraceus (Brandt, 1835) and the whelk Nucella canaliculata (Duclos, 1832). Sea stars and whelks were maintained in laboratory tanks at a constant 9 °C, a constant 12 °C, and a treatment that simulated the Oregon coast upwelling regime by cycling between 14-day periods of 12 and 9 °C. Early in the experiments, sea stars and whelks held at 9 °C consumed about 30% fewer mussels (Mytilus trossulus) than those in warmer tanks. Despite lower consumption by whelks in colder tanks, 9 and 12 °C individuals attained the same final size. Similarly, sea stars in 9 °C tanks showed greater growth per gram of mussel tissue consumed than individuals held at 12 °C. These results suggest that reduced consumption under colder conditions was balanced by reduced metabolic costs. Moreover, there appeared to be an energetic advantage to living in the temperature regime characteristic of intermittent upwelling. Sea stars alternately exposed to 12 and 9 °C had a significantly higher growth rate, conversion efficiency, and storage of reserves in the pyloric caeca than individuals in the constant 12 °C tanks. Whelks maintained under fluctuating temperatures tended to grow faster than those held at constant 12 or 9 °C, although this trend was not statistically significant (p=0.069). These results suggest that benthic consumers experiencing cyclic temperatures may feed intensely during periods of warmer water while benefiting from reduced metabolic costs during cold-water intrusions. Because the fecundity of Pisaster and Nucella is a function of energy stored during the upwelling season, interannual variability in upwelling patterns could alter the reproductive output of these species.     

The annual pyloric cycle of Asterias rubens L. (echinodermata: Asteroidea)

Observations of biochemical changes in the pyloric caeca of Asterias rubens L. in different nutritional states and at different stages of the reproductive cycle show the existence of an annual cycle in the pyloric caeca. This pyloric cycle is closely related to that of the gonads. During the gonadal rest (May to September, when the gonads are barely visible) the pyloric caeca grow and store glycogen. During gonadal activity (October to April), they progressively autolyse and first accumulate, then liberate, lipid reserves. This winter pyloric autolysis provides the gonads with the structural material necessary for their annual growth. The summer pyloric growth must be interpreted as the accumulation of the structural material. Under normal conditions, during gonadal rest, the pyloric glycogen reserves ensure the survival of the animal. Pyloric lipid reserves appear only at the beginning of gonadal activity. Their synthesis is intimately related to the start of the gonadal activity of which they are the principal energy source. We believe that the pyloric cycle is under control of hormones that could be transported through the haemal system.The pyloric caeca are the only reserve organs of starfish. Neither the other digestive organs nor the body wall accumulate energy reserves. During starvation of medium duration (2 to 4 weeks) the pyloric caeca suffice to ensure the survival of the animal by liberating their reserve material and simultaneously starting to autolyse. During prolonged starvation, general autolysis occurs and the size of the starfish diminishes.     

Prey productivity effects on the impact of predators of the mussel, Mytilus californianus (Conrad)

The relationship of increasing prey productivity, a measure incorporating prey settlement and body growth, to changes in the relative impact of two predator groups, birds and the sea star, Pisaster ochraceus (Brandt) on a competitively dominant mussel, Mytilus californianus were examined. The purpose of this experiment was twofold, 1) to determine if the separate effects of each predator group on prey abundance increased as prey productivity increased and 2) to determine if the relative impacts of the two predator groups diverged as prey productivity increased. In this experiment, the separate impact of each predator group increased with increasing prey productivity. However, the relative impact of each predator group did not diverge with increasing prey productivity. Unlike previous studies that suggested with increasing prey productivity the relative effect of two predator groups should diverge, this experiment suggested that communities can have more redundant predator groups than originally thought. The results of an analysis using a proportional hazards model suggested that despite increasing prey productivity, birds and the sea star were equal in their ability to curb population increases by M. californianus. These results highlight the need to carefully consider what type of species to species comparisons to make when attempting to discern the relative roles of different predator groups in a community.     

The relation between feeding and reproduction in Anasterias minuta (Asteroidea: Forcipulata)

Anasterias minuta is an oral-brooding sea star and one of the main predators of intertidal benthos in Patagonia, Argentina. The aims of this study were to: (1) assess the temporal pattern of feeding and brooding, (2) evaluate the effect of body size, tidal height and temperature on feeding and brooding, (3) evaluate temporary changes in digestive and sexual organs and (4) investigate the relationships between the predatory and brooding activities. Females do not feed during the brooding period. Spawning proceeded during March. The brooding period was from March to November, with a maximum in May. The population feeding rate varied seasonally, with a maximum in December and a minimum in May. The feeding rate was positively related to water temperature and sea star size; but not with tidal height. An annual cycle exists for pyloric caeca weight in both sexes; lowest values were found during winter, due to brooding female starvation, and a possible decrease in feeding rate of non-brooding females and males. No inverse relationship was found between the pyloric caeca and gonad weights in females, but a lag of 1 month was observed in males, being the maximal pyloric caeca development before the maximum gonad weight, suggesting nutrient translocation.     

Asexual reproduction and somatic growth of the fissiparous sea star Allostichaster polyplax in New Zealand

Allostichaster polyplax is a fissiparous (capable of reproducing asexually by fission) sea star found in intertidal and shallow subtidal habitats in New Zealand and Australia. A localized population of A. polyplax occurred at a density of 2.7?individuals?m^?2 in an intertidal boulder field at Otago Harbour, South Island, New Zealand. The percentage of sea stars undergoing fission, recorded from January 2010 to March 2011, peaked in January (midsummer) in both years. The frequency of fission decreased for larger sea stars (mean arm length, R?>?25?mm), suggesting an ontogenic shift from asexual to sexual reproduction. Effects of fission (i.e. arm regeneration) and food availability (small gastropods) on growth, storage and sexual reproduction were examined in a factorial laboratory experiment. There was no effect of arm regeneration or food on total arm growth. Storage capacity, measured as pyloric caeca index (PCI), was greater in full-armed than regenerating sea stars, and greater in fed than starved individuals. Fed individuals had a similar PCI as field-collected ones. Gonads were observed in two individuals (males) in the full-armed and fed treatment. Fission did not occur during the experiment. Feeding rate on snails was greater for full-armed than regenerating sea stars. Water temperature had a weak positive effect on the feeding rate of regenerating sea stars. Our findings suggest that fission and subsequent growth of ramets can sustain demographically stable and geographically isolated populations of A. polyplax. The role of sexual reproduction in population dynamics and connectivity of this species (and fissiparous sea stars in general) remains equivocal and requires further research on genetic differentiation within and among populations.     

Allocation of nutrients during the reproductive cycle of Ophidiaster ophidianus (Echinodermata: Asteroidea)

The reproductive cycle of Ophidiaster ophidianus (strictly protected status) from São Miguel Island, in the Azorean Archipelago was studied. The reproductive strategy; the energy allocation of each sex during the reproductive cycle and the nutritional condition of the population were analyzed. Gonadal index (GI) showed a clear seasonal pattern with spawning between August and October but histological examination revealed that gamete release can occur throughout the entire year. The pyloric caeca index (PCI) showed little annual variation but with an inverse relationship with the GI. Allocation of energy to the gonads and to the pyloric caeca reflected the seasonal reproductive strategy of this species. Individuals were able to simultaneously develop gonads, pyloric caeca, and quickly regenerate lost arms. There was a major expenditure of energy by females compared to males but, sexual size dimorphism was not observed. The reproductive pattern observed in O. ophidianus combining rich food availability and seawater temperatures characteristic of a temperate zone may be the key to the success of this species in the Azorean oceanic Island.     

Ochre star mortality during the 2014 wasting disease epizootic: role of population size structure and temperature

Over 20 species of asteroids were devastated by a sea star wasting disease (SSWD) epizootic, linked to a densovirus, from Mexico to Alaska in 2013 and 2014. For Pisaster ochraceus from the San Juan Islands, South Puget Sound and Washington outer coast, time-series monitoring showed rapid disease spread, high mortality rates in 2014, and continuing levels of wasting in the survivors in 2015. Peak prevalence of disease at 16 sites ranged to 100%, with an overall mean of 61%. Analysis of longitudinal data showed disease risk was correlated with both size and temperature and resulted in shifts in population size structure; adult populations fell to one quarter of pre-outbreak abundances. In laboratory experiments, time between development of disease signs and death was influenced by temperature in adults but not juveniles and adult mortality was 18% higher in the 19°C treatment compared to the lower temperature treatments. While larger ochre stars developed disease signs sooner than juveniles, diseased juveniles died more quickly than diseased adults. Unusual 2–3°C warm temperature anomalies were coincident with the summer 2014 mortalities. We suggest these warm waters could have increased the disease progression and mortality rates of SSWD in Washington State.