Did You Know? (Starfish)

starfish in tidal pool at cambridge beach in annisquam

Photo by E.J. Lefavour

That Starfish or sea stars are echinoderms belonging to the class Asteroidea?  The names “starfish” and “sea star” essentially refer to members of the Class Asteroidea. There are 2,000 living species of starfish that occur in all the world’s oceans, including the Atlantic, Pacific, Indian as well as in the Arctic and the Southern Ocean (i.e., Antarctic) regions. Starfish occur across a broad depth range from the intertidal to abyssal depths (>6000 m).

Starfish are among the most familiar of marine animals and possess a number of widely known traits, such as regeneration and feeding on mussels. Starfish possess a wide diversity of body forms and feeding methods. The extent that Asteroidea can regenerate varies with individual species. Broadly speaking, starfish are opportunistic feeders, with several species having specialized feeding behavior, including suspension feeding and specialized predation on specific prey.

Starfish are capable of both sexual and asexual reproduction. Most species are dioecious, with separate male and female individuals, but some are hermaphrodites. For example, the common species Asterina gibbosa is protandric, with individuals being born male, but later changing into females.

Male and female sea stars are not distinguishable from the outside; one needs to see the gonads or be lucky enough to catch them spawning. Each arm contains two gonads, which release gametes (a cell that fuses with another cell during fertilization) through openings called gonoducts, located on the central body between the arms.  (excerpt from Wikipedia)

As a lifelong avid tidal pool explorer, I love coming across a starfish.  This is the first one I had found since moving to Cape Ann, and it remained in this same spot for a couple of weeks.  I didn’t check for gonads, so don’t know if it is a he or a she, or both.

E.J. Lefavour

www.khanstudiointernational.com

One comment

  • The rocks right in front of the lighthouse were always famous for the starfish, and then in summer you will find lots of sand dollars. If I was there I would give you a tour of my favorite tidal pools, my screensaver right now is a great shot of the rocks at Lighthouse Beach, and I think of those pools all the time. Great work, again!!

    Like

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