The blue spiny starfish or Coscinasterias tenuispina belongs to the Echinodermata phylum, and within this to the Asteroidea class, Forcipulatida order and Asteriidae family. It is a starfish native to the shallow waters of the eastern and western Atlantic Ocean, as well as the Mediterranean Sea. The habitat in which we will find this species are the hard rocky substrates, although occasionally we can observe them on sandbanks or in decomposing algae deposits. As for the bathymetric range, it is common to find specimens from 5 to 30 meters deep, although there are descriptions of specimens up to 150 meters deep.
The body of Coscinasterias tenuispina can reach up to 15-20 cm in diameter, and is formed by a small central disk from which a series of arms arise. It usually has more than 5 arms, with 7 arms being the most common, although it is possible to see specimens with between 4 and 11 arms. It is common that the length of the different arms of the specimen are different from each other. The body has a very rough texture, this is due to numerous warts in the center of which there is a very apparent spine whitish in color. These spines and warts are aligned in each of the arms forming 5 longitudinal rows, this being a peculiarity that will allow us to differentiate the specimens of Coscinasterias tenuispina from those of the species Marhasterias glacialis, the latter of larger size and whose spines or barbs form only 3 longitudinal rows instead of the 5 of Coscinasterias tenuispina. As for coloration, this is very variable, with specimens of homogeneous coloration or specimens with different colors such as gray, blue, brown, reddish, orange, white, lilac and yellow forming different spots.
Coscinasterias tenuispina is an active predator, feeding mainly on bivalves and other echinoderms, although it will not hesitate to feed opportunistically on any organic debris it can find.
During the summer months, Coscinasterias tenuispina reproduces mainly asexually by bipartition of the central disc. The two split halves will regenerate the missing arms to give rise to two specimens genetically identical to each other. As a curiosity, it is worth mentioning that on the Atlantic coast of Brazil, where this species is also present, all the specimens reported are male, reproducing asexually throughout the year in the absence of females. On the contrary, during the winter months, the specimens resort to sexual reproduction through the release into the water column of the gametes of male and female specimens, resulting in fertilization and the formation of a planktonic larva.
In the section of curiosities of Coscinasterias tenuispina, from specimens of this species has been isolated the compound asterinic acid, which has been shown to have antitumor activity.
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