Sterechinus neumayeri
The shell of sea urchins is round and spiny, typically from 1.2 to 3.9 in across. They sometimes are black and dull shades of green, olive, brown, purple, blue, and red. Sea urchins move slowly, and feed on mostly algae.
The underside of a sea urchin has much shorter spines and those are easily crushed. During the breeding season the body cavity is crammed with eggs or sperms. The sexes are separate and the young are formed indirectly by the fusion of sperm and eggs released into the water. Sea urchins are external fertilizers. This is done by the males who release their sperms in water that gives a signal to the female to release millions of tiny, jelly-coated eggs. The eggs and sperms collide with each other and fertilization may take place. The sperm that reaches an egg first has to penetrate the jelly coat of the egg. Reactions take place within the egg and then the nucleus of the sperm is released into the egg. A fertilization cone is produced by the egg that surrounds the nucleus and pulls it in. Once the sperm and the eggs fuse together they form a diploid cell. Once fertilization is complete, the fertilized egg begins to divide and multiply rapidly.
The shell of sea urchins is round and spiny, typically from 1.2 to 3.9 in across. They sometimes are black and dull shades of green, olive, brown, purple, blue, and red. Sea urchins move slowly, and feed on mostly algae.
The underside of a sea urchin has much shorter spines and those are easily crushed. During the breeding season the body cavity is crammed with eggs or sperms. The sexes are separate and the young are formed indirectly by the fusion of sperm and eggs released into the water. Sea urchins are external fertilizers. This is done by the males who release their sperms in water that gives a signal to the female to release millions of tiny, jelly-coated eggs. The eggs and sperms collide with each other and fertilization may take place. The sperm that reaches an egg first has to penetrate the jelly coat of the egg. Reactions take place within the egg and then the nucleus of the sperm is released into the egg. A fertilization cone is produced by the egg that surrounds the nucleus and pulls it in. Once the sperm and the eggs fuse together they form a diploid cell. Once fertilization is complete, the fertilized egg begins to divide and multiply rapidly.