REVIEW OF RELATED LITERATURE ON CLASS ASTEROIDEA (SEA STARS)
Mrs. Astrid Sinco
Connie Ryan V. Edpalina
Bio 6 EDA
Review of Related Literature
The sea-star was first found in Tasmania in 1986, but at the time was mis-identified as a native species. It was not until 1992 that the sea-star was identified as A. amurensis, a species which is not native to Australian waters.
The sea-star is a large voracious predator, reaching sizes 40 to 50 cm in diameter. In its native range, the sea-star prefers water temperatures between 7 and 10o C, but has adapted to warmer waters (up to 22o C) in Australia and other countries.”In one year the sea-star is capable of increasing its diameter by 8cm. It is capable of reproducing at 10 cm. In Australia spawning occurs during winter (July to October) at temperatures of 10 to 12o C when females may carry up to 20 million eggs per adult. Fertilisation is external and fertilised eggs develop into free swimming larvae that remain in the plankton for around 90 days, before settling and metamorphosing into juvenile seastars. The live-bearing sea star is restricted to the south eastern coast of Tasmania. Unlike other species whose larval young may be dispersed great distances by ocean currents, live-bearing sea stars are restricted to their parental locations. They live in rocky crevices and are often attached to the underside of rocks where they feed on microscopic algae. They prefer calmer, sheltered waterways because they are slow moving and can be easily dislodged from rock surfaces (Journal Sea Stars: Endemic to Tasmania)
“The sea star lives for up to five years and in Japan its numbers increase and reach outbreak proportions lasting two to three years. These outbreaks tend to occur in three or ten year cycles and there have been some suggestions that the outbreaks are a symptom of a degraded environment. No one is certain why outbreaks of starfish appear to have increased in recent years. One theory suggests that their populations bloom several years after a large typhoon with high rainfall, which produces abundant sediments. These sediments are thought to contain nutrients that contribute to plankton blooms, which serve as food for young starfish. Other theories point to the destruction of their major predators and the effects of pollution.
Besides starfish, many other forces play a major role in the destruction of the reefs. These include overfishing, pollution, typhoons and global warming. In Hawaii, where most of the coral reefs in the United States are found, coral is being decimated by tourists, particularly snorkelers (American Chemical Society, 2000).
Although sea stars destruct reefs they are often important in community structuring processes (PAINE 1969a, b, 1976, DAYTON 1971, PAINE et al. 1985, GAYMER et al. 2004), mainly in intertidal regions in temperate latitudes (MENGE et al. 1994, NAVARRETE & MENGE 1996). Most effects are observed in the lowest zones (subtidal) on rocky substrates, where the starfish are protected from desiccation or other abiotic influences that echinoderms, in general, do not tolerate well (STICKLE & DIEHL 1987). Starfish can be voracious predators that devastate some communities, such as Acanthaster planci (Linnaeus, 1758) on coral reefs (CAMERON et al. 1991) and Asterias sp. on mussels (GAYMER et al. 2002). Not all asteroids, however, are so voracious and some may maintain heterogeneity and biological diversity of their communities (VERLING et al. 2003). All starfish survived all water salinity treatments in the summer and the highest salinity in the winter. In the winter, however, only 57% of the starfish survived the reduced salinity (10 g kg-1) and only 36% righted themselves within 30 minutes.
Sea Stars: Nutrition
The starfish usually hunts for shelled animals like oysters and clams. Recently, there are now 2,000 species of sea star living in all the world’s oceans, from tropical habitats to the cold seafloor. The primarily carnivorous feeding habits of seastars have long been recognized (Boolootian 1966, Mauzey et al. 1968) and during the past 20 to 30 yr sea star predation has been shown to be a major factor in structuring many marine benthic communities (Menge 1982, Duggins 1983). The most detailed studies are those made in the intertidal zone. For example, Paine (1974) demonstrated that the sea star Pisaster ochraceus is the key predator in rocky intertidal communities on the Pacific coast of North America. Its removal shifts the abundance of organisms in lower trophic levels, particularly of species which monopolize space, and markedly changes community structure. One would expect predation by sea stars to be particularly important n the subtidal zone, where their activities are less limited by physiological stress. However, with the exception of the studies of seastar Acanthaster planci on coral reefs (Glynn 1976, B~rkeland 1982), relatively few studies have quantified the impact of asteroid O Inter-Research/Printed in Germany predation in the subtidal zone. A major problem in predicting the impact of seastars is the lack of understanding of the dynamics of seastar populations and in particular of factors determining recruitment intensity and juvenile survival.
Since sea stars have been the top most predator, the hard clam Mercenaria mercenaria burrows deeper into the sediment when the predaceous sea star, Asterias forbesi is present. The supposition that this increase in burial depth represents an escape response designed to reduce predation was tested experimentally by regulating clam burial depth through manipulation of the amount of sediment available for burial. Mercenaria maintained at zero depth were eaten by Asterias at greater rates than those held at ordinary burial depths (2.5-3.0 cm). These clams in turn were eaten at greater rates than those maintained at escape depths (4.0-4.5 cm). The results unambiguously establish an anti-predator function for the burrowing response, as well as underscoring the protective function of the fossorial habit. They are not confounded by behavioral predator food preferences, inherent differences between prey species, or debilitating side effects of preventing prey from escaping. Mechanisms by which the burrowing response may reduce predation are discussed and observations on the unreported clam-digging behavior of Asterias forbesi are presented (Doering: 5: 2010)
“We performed field and laboratory studies to investigate how large adult Leptasterias polaris detect and locate their major prey, large infaunal bivalves, in the sediment bottom community. A field survey using SCUBA diving showed that 95% of the locations where L. polaris dug into the sediment bottom were over bivalves and this success rate was much greater than if digging was done at random (22%). Furthermore, when sea stars were provided with a low density of randomly distributed prey in a laboratory arena, they dug exclusively in locations where a clam had been buried. These observations indicated that L. polaris locates infaunal prey prior to investing energy into digging. Studies in a laboratory flow tank showed that L. polaris readily detected and moved towards its preferred prey Ensis directus whereas its responses to less preferred prey Mya truncata and Spisula polynyma were much weaker. The degree to which it oriented towards these three common prey seemed to reflect potential energy intake relative to foraging costs (which likely increase with the depth of the different prey) and risks from interactions with other carnivores (which are greatest when feeding on large prey). This is the first study to clearly demonstrate that sea stars use prey odours to locate infaunal prey (Thompson et. al.). Furthermore, some sea stars live on the reef, and the sea star is actually a predator of coral polyps, which means that too many sea stars can damage the reef and leave behind only calcium carbonate. This breakdown in the food chain, affects the population of deep-sea fish in the area, and will reduce the amount of large fish and game.
Other Features of Sea Stars
Sea stars as part of the Phylum Echinodermata, captures around 0.1 gigatonnes of carbon per year1. This is less than the global capture resulting from pelagic organisms – a figure that ranges from 0.4 to 1.8 gigatonnes depending on the sources considered – but still represents a sizeable carbon pump. By comparison, human activities lead to around 5.5 gigatonnes of carbon being pumped into the air every year ( Lebrato, 2010) “Echinoderms are found in all ecosystems at all depths worldwide and have bodies that can be composed of more than 80% calcium carbonate. A new study published in Nature credits these abundant invertebrates with sequestering 100 million tons of carbon in their tissues each year.
Also, the starfish is sensitive to reduced salinity (10g kg1), especially during winter. Echinoderms are typically osmoconformers and stenohaline, and very permeable to water and ions (review in STICKLE & DIEHL 1987) and so it is expected that they not be active predators when exposed during low tide. Indeed, no starfish was ever seen consuming prey while exposed during low tide. However, physiological limitation does not completely explain the apparent lack of predatory influence on the community, since predation could certainly increase during high tides.
A new study finds that a species of sea star stays cool using a strategy never before seen in the animal kingdom. The sea stars soak up cold sea water into their bodies during high tide as buffer against potentially damaging temperatures brought about by direct sunlight at low tide.
According to Pincebourde of François Rabelais University in Tours, France, sea stars were assumed to be at the mercy of the sun during low tide “This work shows that some sea stars have an unexpected back-up strategy.” Sea stars need to endure rapid changes in temperature. During high tide, they are fully submerged in cool sea water. But when tides receded, the stars are often left on rocky shorelines, baking in the sun.
Clearly the stars had some way of beating the heat, but scientists were unsure how they did it. Pincebourde and his team thought it might have something to do with fluid-filled cavities found in the arms of sea stars. So he set up an experiment to test it. The researchers placed sea stars in aquariums and varied the water level to simulate tidal patterns. Heat lamps were used to control temperature, with some stars experiencing hotter temperatures than others. The researchers found that stars exposed to higher temperatures at low tide had higher body mass after the high tide that followed. Since the stars were not allowed to eat, the increased mass must be from soaking up water. “This reservoir of cool water keeps the sea star from overheating when the tide recedes again the next day, a process called ‘thermal inertia,'” Pincebourde said. What appears to be happening, the researchers say, is that a hot low tide serves as a cue telling the star to soak up more water during the next high tide. And the amount of water the stars can hold is remarkable. “It would be as if humans were able to look at a weather forecast, decide it was going to be hot tomorrow, and then in preparation suck up 15 or more pounds of water into our bodies,” said co-author Brian Helmuth of the University of South Carolina in Columbia (University of Chicago Press Journals: Sea Stars bulk up to beat the heat)
Not only that, according to the study conducted by Scottish Association for Marine Science (SAMS), a non-stick slime made by starfish may lead to new treatments for asthma, athritis, hay fever and other inflammatory conditions, say marine biologists in Scotland. The scientists, from the (SAMS) in Oban, Argyll, have been studying the slime produced by the spiny starfish, Marthasterias glacialis, commonly found in the waters around Scotland and other parts of the British Isles, and say it could be vital for treating human infections. Lead researcher Dr Charlie Bavington, founder and managing director of Glycomar, a marine biotechnology company based at SAMS, has been talking to the media about their work. In an interview with the BBC aired on Thursday 9 December, he demonstrated how the starfish produced the slime: he took a starfish with a span of about 30 cm or 12 in out of a tank, held it, after a few seconds the slime began visibly to ooze from the creature’s spiny body. The slime is a defence mechanism and also prevents debris from sticking to the starfish.
Furthermore, researchers have discovered a chemical in sea urchins that might be used to lure starfish away from coral reefs, an endangered ecosystem they are devouring at an alarming rate. The finding was presented here today during the 2000 International Chemical Congress of Pacific Basin Societies. According to the American Chemical Society, The poisonous crown-of-thorns starfish, which feasts on coral and whose population is believed to be expanding, is a major source of destruction of valued habitats in the tropical zones of the Indian and Pacific oceans, including Hawaii. The problem is acute in Japan, where extensive, costly efforts to control the creature have met with little success.
In 1984 Janssen, Orosco, Largo, Ayson and Uy, students of University of San Carlos conducated a study in the unique mating behaviour of Archaster typicus (Muller et Troschel, 1840) they were able to find that there is no macroscopic feature that allows a definite determination of sex. Male Archaster typicus are able to recognize the sex of another individual by crawling over the center of another species on its center within a few seconds. The sex indicator is located at the center of the female.
It was reported by Choi that the Class Asteroidea was found in sandy substrate in the upper zone that was 20- 40 meters from above.
Similar study by (Antinero, 2001) conducted in the intertidal zone of Pangyawan, Gitagum, Misamis Oriental. Sea stars were located on rocky coralline substrate.
Another similar study was conducted in the intertidal zone of Tagcatong, Carmen, Agusan del Norte. Archaster typicus was the most abundant that had 42 individuals recorded (David, 1999).
(Paculba, 1995) conducted a study on the species diversity of sea stars in Bolo bolo, El Salvador, Misamis Oriental. Archaster typicus, Archaster angulatus, Oreaster nodosus and Linkia laevigata were the species found in the area. In the computations on Shannon’s Index of general diversity, the diversity was 0.528, which indicated that the area was diversified with respect to the presence of sea stars. Archaster typicus was the most abundant, followed by Archaster angulatus (33%0, then by Oreaster nodosus (12%) and finally by Linkia laevigata which comprised only 11% of the collected species.
“Study: Sea stars bulk up to beat the heat”, January 3, 2011: by Kevin Stacey
“Carbon-Slurping Sea Stars”, January 2, 2011: by Sea Notes, Monterey Bay Aquarium
“Sea Stars endemic to Tasmania”, January 3, 2011: by Marine and Coastal Research Tasmania
“Starfish Slime Could Hold Key To New Treatment For Asthma, Arthritis”, January 3, 2011: by Apex Global
“Reduction of sea star predation by the burrowing response of the hard clam Mercenaria mercenaria (Mollusca: Bivalvia)”, January 3, 2011: by Peter H. Doering
“Chemical May Deter Starfish From Devouring Endangered Coral Reefs”, January 2, 2011: by Science Daily
“Importance of Coral Reef Ecosystems”, January 3, 2011: by Karen Jennings
“The role of Asterina Stellifera (Echinodermata: Asteroidea) as a predator in a rocky intertidal community in Southern Brazil”, January 3, 2011: Zoologia( Curitiba Impresso)
Acenas, Ron Dreyfus L., “Species Duversity on Echinoderms in the Intertidal Zone of Barangay Mabini, Binuangan, Misamis Oriental” Biology Department Research; Xavier University, Cagayan de Oro City, 2009.
Yrag, Cherryl, “Species Diversity on Echinoderms in the Intertidal Zone of Domo, Villanueva, Misamis Oriental” Biology Department Research; Xavier University, Cagayan de Oro City