Thursday, 23 February 2017
It has been a while since I shared sea urchin facts, you can see Vol. 1 and 2 here.
Sea urchins are sexually reproducing organisms. First millions of eggs are released by the females and they unite and fuse with the sperms released by the males. The unification of the jelly-coated egg and the tiny sperm usually occurs outside the female’s body; however in some rare cases the fertilization will take place within the female’s body. Once the fertilization of the gametes occurs, a larva is formed. This larva is also known as a pluteus. The sex of the larva is impossible to distinguish until it itself begins to release either eggs or sperms during its adulthood. The time that adult sea urchins start reproducing is during the ages of 2-5 years. (source: tolweb.org)
The image above shows the growth and development of the sea urchin, Lytechinus pictus. These sea urchins are found off the coast of California. After a few days the embryo will gastrulate and form a primitive digestive system (early prism stage). At this stage ciliated bands are formed that allow the larva to form feeding currents by which to concentrate particles in the water for ingestion. As the larva develops the structure becomes more complicated and larval "arms" are generated to aid in locomotion and feeding (pluteus stage larvae). Eventually this feeding larva will grow and develop enough so that it can metamorphose into a juvenile sea urchin and begin to look like the sea urchin most people are familiar with (i.e., a pin cushion). (source of text and above image: Douglaspace)
We sometimes find tiny sea urchins, through natural selection of storms and strong currents, but also eaten by other sea animals only a small portions survive to adulthood, but that is how mother nature works.
Please enjoy this magical video below: