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The purple sea urchin, along with sea otters and abalones, is a prominent member of the kelp forest community. [18] The purple sea urchin also plays a key role in the disappearance of kelp forests that is currently occurring due to climate change; [19] when urchins completely eliminate kelp from an area, an urchin barren results.
An urchin barren is commonly defined as an urchin-dominated area with little or no kelp. Urchin grazing pressure on kelp is a direct and observable cause of a "barren" area. However, determining which factors contribute to shifting a kelp bed to an urchin barren is a complex problem and remains a matter of debate among scientists.
In Alaskan kelp forest ecosystems, sea otters are the keystone species that mediates this trophic cascade. In Southern California, kelp forests persist without sea otters and the control of herbivorous urchins is instead mediated by a suite of predators including lobsters and large fishes, such as the California sheephead.
Some believe the only way to restore kelp is to reduce the purple urchins, which can go dormant for years only to remerge and eat new kelp growth. Chefs have started serving purple urchins to ...
The purple sea urchin is spiny but not dangerous, and it can be held in hand with some care. Paracentrotus lividus is usually found just below low water mark at depths down to twenty metres and sometimes also in rock pools. It is found on rocks and boulders, and in seagrass meadows of Zostera marina and Posidonia oceanica.
Kelp forests provide important habitats for many fish species, sea otters and sea urchins. Directly and indirectly, marine coastal ecosystems provide vast arrays of ecosystem services for humans, such as cycling nutrients and elements , and purifying water by filtering pollutants.
The California sheephead lives in kelp forests and rocky reefs, where it feeds on sea urchins, molluscs, lobsters, and crabs. Fertilized eggs are released into the water column and hatch, resulting in planktonic larva. [5] Like many wrasse species, sheephead are protogynous. All are born female, and the largest individuals become male due to ...
Sea urchin eggs are transparent and can be manipulated easily in the research laboratory. Their eggs can be easily fertilized and then develop rapidly and synchronously. [6] [7] For decades, the sea urchin embryo has been used to establish the chromosome theory of heredity, the description of centrosomes, parthenogenesis, and fertilization.