How do starfishes eat?
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The common starfish feeds on a variety of benthic organisms. These include bivalve molluscs, polychaete worms, barnacles, gastropod molluscs, other echinoderms and carrion. When feeding on a mollusc such as a mussel, it attaches its tube feet to each shell valve and exerts force to separate them slightly. Even a gap of only is sufficient for the starfish to insert a fold of its stomach, secrete enzymes and start digesting the mollusc body. When the contents is sufficiently liquid, it brings its stomach back to its rightful position with the food inside. The common starfish has a well-developed sense of smell and can detect the odour of prey species such as the common mussel ("Mytilus edulis") and crawl towards it. It can also detect the odour of the predatory common sunstar ("Crossaster papposus"), which eats other starfish, and take evasive action.
The common starfish is dioecious, which means that each individual is either male or female. In the spring, the females release their eggs into the sea. A moderate sized starfish is estimated to be able to produce 2.5 million eggs. The males shed their sperm and fertilisation takes place in the water column. The larvae are planktonic and drift for about 87 days before settling on the seabed and undergoing metamorphosis into juveniles. Common starfish are believed to live for about seven to eight years. When well fed, the juveniles can increase their radius at the rate of slightly more than per month during the summer and autumn and slightly less than per month in the winter. An adult common starfish can survive starvation for several months although it loses weight in the process. One specimen shrank from a radius of to a radius of after starvation for five months.
Common starfish
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Starfish are marine invertebrates. They typically have a central disc and five arms, though some species have a larger number of arms. The aboral or upper surface may be smooth, granular or spiny, and is covered with overlapping plates. Many species are brightly coloured in various shades of red or orange, while others are blue, grey or brown. Starfish have tube feet operated by a hydraulic system and a mouth at the centre of the oral or lower surface. They are opportunistic feeders and are mostly predators on benthic invertebrates. Several species have specialized feeding behaviours including eversion of their stomachs and suspension feeding. They have complex life cycles and can reproduce both sexually and asexually. Most can regenerate damaged parts or lost arms and they can shed arms as a means of defence. The Asteroidea occupy several significant ecological roles. Starfish, such as the ochre sea star ("Pisaster ochraceus") and the reef sea star ("Stichaster australis"), have become widely known as examples of the keystone species concept in ecology. The tropical crown-of-thorns starfish ("Acanthaster planci") is a voracious predator of coral throughout the Indo-Pacific region, and the northern Pacific sea star is considered to be one of the world's 100 worst invasive species.
Starfish
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The starfishes "Acodontaster conspicuus", "Acodontaster hodgsoni", "Odontaster meridionalis" and "Perknaster fuscus" feed on the sponges, while "Odontaster validus" mostly scavenges, and "D. brucei" and the gastropod "Trophonella longstaffi" both feed on the bivalve "L. hodgsoni". "D. brucei" primarily feeds on molluscs, but does not seem to eat sponges as do many other starfish. It is sometimes preyed on by the sea anemone "Urticinopsis antarctica". Developing embryos of this species are brooded by the female until they have developed into juvenile starfish.
Diplasterias brucei
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Harlequin shrimp's only source of nutrition comes from starfish. They are very skilled at flipping over the slow starfish on its back, and eating the tube feet and soft tissues until it reaches the central disk. They, usually one female and one male, use their claws to pierce the tough skin and feeding legs to help them maneuver the starfish. Sometimes the starfish will shed the arm that the shrimp attacked and regrow (the shrimp can then re eat it), but it is usually too wounded to regrow. They may also feed on sea urchins, because they have tube feet as well, but that is rare and only if they're very hungry.
Hymenocera
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Atlantic wolffish use their strong jaws to eat hardshell molluscs, crustaceans, and echinoderms. They do not eat other fish. They are known to frequently eat large whelks ("Buccinum"), cockles ("Polynices", "Chrysodomus" and "Sipho"), sea clams ("Mactra"), large hermit crabs, starfish, sea urchins. They are an important predator of sea urchins and green crabs, whose populations escalate rapidly and can negatively affect the health of a marine system.
Atlantic wolffish
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The Crown-of-Thorns Starfish is a coral reef predator which preys on coral polyps by climbing onto them, extruding its stomach over them, and releasing digestive enzymes to absorb the liquefied tissue. An individual adult of this species can eat up to six square meters of living reef in a single year. Geological evidence suggests that the Crown-of-Thorns Starfish has been part of the Great Barrier Reef's ecology for "at least several thousand years", but there is no geological evidence for Crown of Thorns outbreaks. The first known outbreak occurred during the 1960s. Large outbreaks of these starfish can devastate reefs. In 2000, an outbreak contributed to a loss of 66% of live coral cover on sampled reefs in a study by the CRC Reefs Research Centre. Although large outbreaks of these starfish are believed to occur in natural cycles, human activity in and around the Great Barrier Reef can worsen the effects. Reduction of water quality associated with agriculture can cause the crown-of-thorns starfish larvae to thrive. Fertilizer runoff from farming increases the amount of phytoplankton available for the Crown of Thorns Starfish larvae to consume. A study by the Australian Institute of Marine Science showed that a doubling of the chlorophyll in the water leads to a tenfold increase in the crown-of-thorns starfish larvae's survival rate. Overfishing of its natural predators, such as the Giant Triton, is also considered to contribute to an increase in the number of Crown of Thorns Starfish. The CRC Reef Research Centre defines an outbreak as when there are more than 30 adult starfish in an area of one hectare. There have been three large outbreaks of COTS on the reef since observation began, between 1962 and 1976; 1978 and 1991; 1993 and 2005, and a fourth began in 2009. Investigation is being undertaken into mimicking a chemical scent released by the COTS' natural predator, the giant triton snail.
Environmental threats to the Great Barrier Reef
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Most species are generalist predators, eating microalgae, sponges, bivalves, snails and other small animals. The crown-of-thorns starfish consumes coral polyps, while other species are detritivores, feeding on decomposing organic material and faecal matter. A few are suspension feeders, gathering in phytoplankton; "Henricia" and "Echinaster" often occur in association with sponges, benefiting from the water current they produce. Various species have been shown to be able to absorb organic nutrients from the surrounding water, and this may form a significant portion of their diet.
Starfish
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Campaigns and Community Support
The supporter base of Starfish Greathearts Foundation is based on widespread support from individuals through donations and income generated through successful campaigns. The Dinners of Hope Campaign is the most popular ongoing campaign that Starfish has developed. It is simple in the fact that everyone has to eat and therefore everyone can participate in the campaign. The emphasis of this campaign brings to the table the chance to educate, communicate and fundraise with minimal input and optimal results. The concept is simple in that supporters are asked to host a meal for family, friends or colleagues and then ask guests for a doantion rather than a contribution to the meal. The campaign also works as a powerful tool in promoting HIV/AIDS awareness and education at all levels. The campaign has mobilised more than 20,000 individuals and 120 corporations worldwide to participate.
Starfish Greathearts Foundation
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Crown-of-thorns starfish ("Acanthaster planci") is the major predator of the reefs, as it preys upon coral polyps by climbing onto them, extruding its stomach over them, and releasing digestive enzymes to absorb the liquefied tissue. An individual adult can eat up to 6 m of reef per year. In 2000, an outbreak of crown-of-thorns starfish contributed to a loss of 66% of live coral cover on sampled reefs. Changes in water quality and overfishing of natural predators, such as the Giant Triton, may have contributed to an increase in the number of crown-of-thorns starfish.
Coral Sea
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Although starfish do not have many well-defined sense organs, they are sensitive to touch, light, temperature, orientation and the status of the water around them. The tube feet, spines and pedicellariae are sensitive to touch. The tube feet, especially those at the tips of the rays, are also sensitive to chemicals, enabling the starfish to detect odour sources such as food. There are eyespots at the ends of the arms, each one made of 80–200 simple ocelli. These are composed of pigmented epithelial cells that respond to light and are covered by a thick, transparent cuticle that both protects the ocelli and acts to focus light. Many starfish also possess individual photoreceptor cells in other parts of their bodies and respond to light even when their eyespots are covered. Whether they advance or retreat depends on the species.
Starfish
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This starfish feeds on various small sea cucumbers, such as "Cucumaria miniata", "Cucumaria curata", "Eupentacta quinquesemita", "Eupentacta pseudoquinquesemita", and "Psolus chitonoides". It also eats brachiopods, ascidians, or sea pens.
Solaster stimpsoni