Guide of SEA STARS

Growth of a Starfish
With some patience it is possible to find the larvae of animals like the common starfish ( Asterias rubens ) in the plankton and to follow the development of these larvae into miniature sea-stars.
Larvae of other echinoderms are also present in the plankton, like those of sea urchins, sea cucumbers and brittle stars.
Larvae of sea cucumbers and starfishes don't have a skeleton, those of sea urchins and brittle stars possess an internal skeleton, consisting of skeletal spicules, supporting the more elongate "arms" of the larvae.
The microscopist, living not too far from the sea, can follow this marvellous metamorphosis.


SEA STARS

Sediment selection by juvenile sea scallops, sea stars and rock crabs Journal of Shellfisheries Research - Find Articles
In laboratory trials, groups of scallops (~30 mm shell height) were simultaneously offered four sediment types in the presence and absence of a sea star or a rock crab: (1) glass representing a homogeneous, hard bottom; (2) sand; (3) granule and (4) pebble.
However, scallop distribution was similar to the expected distribution when a sea star was present, because sea star encounters are an important trigger of scallop swimming, leading to frequent redistribution of scallops.
Sea stars spent less time than expected on glass, whereas crabs spent more time than expected on sand.
Predation of scallops by sea stars and rock crabs was not influenced by sediment type.
Also, dispersal may he higher when sea stars are present at an aquaculture site..
The bottom culture of sea scallops (Placopecten magellanicus), where juvenile scallops are released (seeded) onto the sea bottom and allowed to grow to commercial size, has gained considerable interest in the last two decades on the coast of the northwest Atlantic (Couturier et al.
The two main processes influencing loss of seeded scallops are predator-related mortality (specifically by predatory sea stars Asterias spp.
Certain sediment types may reduce a predator's searching and handling ability of prey, or provide prey with physical refuges that reduce detection by predators (Sponaugle & Lawton 1990, Arsenault & Himmelman 1996).

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Photo by www.seaview4u.com

USATODAY.com - Brainless sea stars, Earth nights average 12 hours, astronauts dodge rads
'Brainless' sea stars, Earth nights average 12 hours, astronauts dodge rads Q: How does a sea star function without a brain? How does it coordinate its arm movements and sense light with the 'eyespots' if there are no brain cells to process or use the information? (Penryn, California) .
The doughboy sea star eats corals in the Indo-Pacific Ocean.
A: A sea star (starfish) manages nicely without a control center made up of white and gray matter and housed in a head — what we think of as a brain.
In some species and individuals, one arm almost always takes the lead when the sea star walks.
This exotic creature moves by taking in seawater and channeling the water through a system of canals ringing its center.

Benefits



Alien sea-star puts our native marine life at risk : Media Releases : News : The University of Melbourne
A rapidly multiplying population of predatory Northern Pacific sea-stars in Port Phillip Bay is putting stocks of native scallops, abalone and other seabed species at risk, warn University of Melbourne marine life experts.
The local marine animals are falling prey to the invader because they do not recognise the Northern Pacific sea-star as a predator and so do not attempt to escape from it ­ as they do from similarly predatory native sea-stars.
Major scallop beds off Rye have been ravaged by the marauders, which invade sandy seabeds, rocky reefs, pier pylons and similar habitats.
Northern Pacific sea-stars, thought to have been introduced to the Bay in ships' ballast water, were not an evident menace as recently as three years ago but now ­ numbering an estimated 100 million or more ­ threaten the whole Bay.
University of Melbourne Department of Zoology Aquarium Curator, Mr John Ahern, warns that if a plan to control or eradicate the introduced sea-star is not implemented quickly the potential exists for a whole range of native marine animals to be under serious threat.
'If the introduced sea-stars spread throughout southern Australia then commercial scallop and abalone fisheries could also be damaged, ' he says.

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