scholarly journals Arm Deflation in the Rare Thorny Sea Star, Poraniopsis inflatus (Asteroidea: Poraniidae), A Defensive Response to other Sea Stars?

2010 ◽  
Vol 124 (3) ◽  
pp. 199
Author(s):  
Roland C. Anderson ◽  
Ronald L. Shimek
Keyword(s):  
Coelomic Fluid ◽  
Defensive Response ◽  
Sea Star ◽  
Sea Stars ◽  
Defensive Reaction ◽  
Northeastern Pacific

The Thorny Sea Star, Poraniopsis inflatus, is rare in the Northeastern Pacific. It lacks pedicellariae or other overt defenses for protection against other predatory sea stars. During an earlier study, a P. inflatus confronted by an asteroid-eating sea star was observed to exhibit a possible defensive reaction: "arm deflation." It was 15 years before another P. inflatus specimen could be obtained and that hypothesis confirmed by testing with individuals of 18 other sea-star species. Contact with individuals of four predatory sea-stars, Asterina miniata, Crossaster papposus, Solaster dawsoni, and Pycnopodia helianthoides, elicited the reaction in the P. inflatus. The specimen collapsed ("deflated") an arm closest to the predatory star, possibly by expelling coelomic fluid, exposing more of its embedded thorns (hence its common name) which may discourage other sea stars from attempting to eat it.

Bathymetric Distribution of Sea Stars (Asteroidea) off the Northern Oregon Coast

1966 ◽  
Vol 23 (11) ◽  
pp. 1673-1714 ◽  
Author(s):  
Miles S. Alton
Keyword(s):  
Atomic Energy Commission ◽  
Abundant Species ◽  
Sea Star ◽  
Sea Stars ◽  
Faunal Assemblages ◽  
Number Of Species ◽  
Northeastern Pacific ◽  
Abyssal Zone ◽  
Abyssal Fauna ◽  
Shallow Water Species

During U.S. Bureau of Commercial Fisheries' Atomic Energy Commission trawling investigations in waters adjacent to the mouth of the Columbia River, a total of 54 species and one subspecies of sea stars was collected from bottom depths of 50–1050 fath. The sea stars in the area of study can be divided into four faunal assemblages by benthic zones: (1) an outer sublittoral fauna (50–108 fath) consisting of several shallow-water species, some of which have their apparent maximum depth of occurrence in this zone. The number of species and the availability of sea stars per hour of trawling is much lower in this zone compared to the other benthic zones in the study area; (2) an upper bathyal fauna (122–258 fath) consisting of several species having either a continuous or discontinuous circumboreal distribution; (3) a lower bathyal fauna (275–500 fath) characterized by a large number of species and a high availability of sea stars in terms of numbers and weight per hour of trawling. Several of the more frequently occurring and abundant species in this zone belong to genera endemic to the northeastern Pacific; and (4) an abyssal fauna (900–1050 fath) consisting almost entirely of species belonging to cosmopolitan genera.The bathyal-abyssal zone (585–850 fath) is considered a zone of transition because of the intrusion into this zone of elements of the sea star fauna from both the lower bathyal and the abyssal.

Empathy Does Not Amplify Vicarious Threat Learning

2019 ◽  
Author(s):  
Alexander Lane Williams ◽  
Christopher C Conway
Keyword(s):  
Individual Differences ◽  
Skin Conductance ◽  
Defensive Response ◽  
Conditioned Stimuli ◽  
Defensive Reaction ◽  
Direct Exposure ◽  
Conditioned Responses ◽  
Clinically Significant ◽  
Stimulus Materials ◽  
Dispositional Empathy

Clinically significant fears and phobias can be acquired vicariously. Witnessing a demonstrator’s defensive reaction to potentially dangerous objects and situations can instill conditioned threat responses in the observer. The present study concentrates on individual differences in this social learning process. Specifically, we hypothesized that dispositional empathy modulates vicarious threat conditioning. We examined university students’ (N = 150) conditioned threat responding after they observed strangers undergo Pavlovian threat conditioning. There was evidence of a substantial conditioned defensive response (Cohen’s d = 0.66), as indexed by elevated skin conductance reactions during participants’ direct exposure to the vicariously conditioned stimuli. Contrary to expectations, indices of dispositional empathy were weakly related to the size of conditioned responses (median r = .04). Our results confirm that vicarious threat learning can be evaluated experimentally, but they do not support the hypothesis that empathy amplifies this process. The preregistration, stimulus materials, data, and analysis code for this study are available at https://osf.io/h6hm2.

scholarly journals Sea stars generate downforce to stay attached to surfaces

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mark Hermes ◽  
Mitul Luhar
Keyword(s):  
Body Shape ◽  
Control Volume ◽  
Water Channel ◽  
Morphological Plasticity ◽  
The Body ◽  
Sea Star ◽  
Sea Stars ◽  
Hydrodynamic Loads ◽  
Spherical Dome ◽  
Star Models

AbstractIntertidal sea stars often function in environments with extreme hydrodynamic loads that can compromise their ability to remain attached to surfaces. While behavioral responses such as burrowing into sand or sheltering in rock crevices can help minimize hydrodynamic loads, previous work shows that sea stars also alter body shape in response to flow conditions. This morphological plasticity suggests that sea star body shape may play an important hydrodynamic role. In this study, we measured the fluid forces acting on surface-mounted sea star and spherical dome models in water channel tests. All sea star models created downforce, i.e., the fluid pushed the body towards the surface. In contrast, the spherical dome generated lift. We also used Particle Image Velocimetry (PIV) to measure the midplane flow field around the models. Control volume analyses based on the PIV data show that downforce arises because the sea star bodies serve as ramps that divert fluid away from the surface. These observations are further rationalized using force predictions and flow visualizations from numerical simulations. The discovery of downforce generation could explain why sea stars are shaped as they are: the pentaradial geometry aids attachment to surfaces in the presence of high hydrodynamic loads.

Purification and partial characterization of AIP1: A novel protein from sea-star (Astropecten indicus) coelomic fluid

Toxicon ◽  
2019 ◽  
Vol 159 ◽  
pp. S10-S11
Author(s):  
Mansi Baveja ◽  
Angshuman Sarkar ◽  
Sukanta Mondal ◽  
Dibakar Chakrabarty
Keyword(s):  
Partial Characterization ◽  
Coelomic Fluid ◽  
Sea Star ◽  
Novel Protein

?Tethyaster albertensis, a Late Cretaceous (Turonian) sea star from the Cardium Formation, Alberta, Canada

1990 ◽  
Vol 64 (6) ◽  
pp. 1045-1049 ◽  
Author(s):  
Russell L. Hall ◽  
Suzan Moore
Keyword(s):  
North America ◽  
Late Cretaceous ◽  
Sea Star ◽  
Sea Stars ◽  
Peace River ◽  
The North ◽  
The Family ◽  
Cardium Formation ◽  
Northern Alberta ◽  
Limited Change

Although many of the surviving lineages of sea stars appeared during an early Mesozoic radiation of the class and have undergone limited change since then, they have left a very poor fossil record, particularly in the Mesozoic of North America (Blake, 1981). This record from the Late Cretaceous of Alberta is made more significant by the fact that it is apparently only the second occurrence of a member of the family Astropectinidae in the Cretaceous of North America; Lophidiaster silentiensis was described by McLearn (1944) from the Lower Cretaceous (Albian) Hasler Formation, from a now-submerged locality on the Peace River in northern Alberta. All previously recorded fossil sea stars from the North American Cretaceous are representatives of the family Goniasteridae.

Behavioral interactions between the actinian Tealia piscivora (Anthozoa: Actiniaria) and the asteroid Dermasterias imbricata

1985 ◽  
Vol 63 (8) ◽  
pp. 1921-1929 ◽  
Author(s):  
Joel Elliott ◽  
James Dalby Jr. ◽  
R. Cohen ◽  
D. M. Ross
Keyword(s):  
Sea Anemone ◽  
Sea Star ◽  
Sea Stars ◽  
Behavioral Interactions ◽  
Size Dependent ◽  
Intermediate Size

Interactions between the sea anemone Tealia piscivora and the sea star Dermasterias imbricata have been studied in the laboratory and in subtidal habitats. Dermasterias causes the release of the pedal disk of smaller T. piscivora. The response is specific. Nineteen other sea stars did not cause release; four other species of Tealia did not respond to Dermasterias. The response is size dependent; unfailing and quick in small T. piscivora, less frequent and slow in those of intermediate size, it did not occur at all in large specimens. Unrestrained T. piscivora generally survived interactions with Dermasterias but when prevented from detaching, most of the small anemones were devoured. Tealia piscivora have been observed to detach and engulf small Dermasterias. Most small anemones were found at greater depths; most large anemones were found at lesser depths where Dermasterias were most abundant. It is suggested that by releasing the pedal disk, small T. piscivora eventually end up in deeper water where there are few Dermasterias and thus the anemones escape predation.

scholarly journals Competitors as accomplices: seaweed competitors hide corals from predatory sea stars

2015 ◽  
Vol 282 (1814) ◽  
pp. 20150714 ◽  
Author(s):  
Cody S. Clements ◽  
Mark E. Hay
Keyword(s):  
Field Experiments ◽  
Coral Cover ◽  
Ecological Communities ◽  
Protective Effects ◽  
Sea Star ◽  
Sea Stars ◽  
Macroalgal Blooms ◽  
Feeding Experiments ◽  
High Preference ◽  
And Function

Indirect biotic effects arising from multispecies interactions can alter the structure and function of ecological communities—often in surprising ways that can vary in direction and magnitude. On Pacific coral reefs, predation by the crown-of-thorns sea star, Acanthaster planci , is associated with broad-scale losses of coral cover and increases of macroalgal cover. Macroalgal blooms increase coral–macroalgal competition and can generate further coral decline. However, using a combination of manipulative field experiments and observations, we demonstrate that macroalgae, such as Sargassum polycystum , produce associational refuges for corals and dramatically reduce their consumption by Acanthaster . Thus, as Acanthaster densities increase, macroalgae can become coral mutualists, despite being competitors that significantly suppress coral growth. Field feeding experiments revealed that the protective effects of macroalgae were strong enough to cause Acanthaster to consume low-preference corals instead of high-preference corals surrounded by macroalgae. This highlights the context-dependent nature of coral–algal interactions when consumers are common. Macroalgal creation of associational refuges from Acanthaster predation may have important implications for the structure, function and resilience of reef communities subject to an increasing number of biotic disturbances.

Protective refuges for seeded juvenile scallops (Placopecten magellanicus) from sea star (Asterias spp.) and crab (Cancer irroratus and Carcinus maenas) predation

2005 ◽  
Vol 62 (8) ◽  
pp. 1766-1781 ◽  
Author(s):  
Melisa C Wong ◽  
Myriam A Barbeau ◽  
Allan W Hennigar ◽  
Shawn MC Robinson
Keyword(s):  
Initial Density ◽  
Carcinus Maenas ◽  
Predation Rate ◽  
Seeding Density ◽  
Alternative Prey ◽  
Sea Star ◽  
Placopecten Magellanicus ◽  
Sea Stars ◽  
Cancer Irroratus ◽  
Mussel Density

We examined two methods to provide refuge for seeded juvenile sea scallops (Placopecten magellanicus) from sea star (Asterias spp.) and crab (Cancer irroratus and Carcinus maenas) predation by considering (i) initial density of seeded scallops and (ii) presence of an alternative prey species (blue mussel (Mytilus edulis)). In the seeding density experiment, underwater plots were seeded with different densities of scallops (1, 6, and 69·m–2). In the alternative prey experiment, plots were seeded with one density of scallops (5·m–2) and different densities of mussels (0, 5, and 30·m–2). Animal densities were monitored over time, and predation rate was estimated using tethered scallops. In the seeding density experiment, scallop density in plots initially seeded with 6 scallops·m–2 decreased at the slowest rate. Estimated predation rate of scallops in all plots tended to increase with prey density. In the alternative prey experiment, mussel density decreased immediately after seeding, while scallop density decreased after approximately 1 week. Estimated predation rate of scallops decreased with increasing mussel density. Also, sea stars aggregated in plots containing scallops and mussels. In both experiments, 17%–58% of seeded scallops were lost to dispersal, and final scallop density was approximately 1·m–2, independent of treatment.

Sign in / Sign up

Export Citation Format

Share Document