One of the most common objects found along our New England sea coast is
the star fish, called by the seamen “Five-fingered Jack.” The fact of
its being common does not at all imply that its habits are commonly
known. The great difficulty of watching it in its native haunts has been
a drawback to getting better acquainted with it, but when taken to an
aquarium it has been found to be an exceedingly interesting little star.
At low tide you may find hundreds of them clinging to the rocks, sea
moss or on the sandy bottom, but they prefer deep water. Their color
varies from a dark rich brown to a reddish, and often a chocolate shade,
sometimes lighter; but no matter the shade, they are always attractive.
The upper side is slightly convex, rough and tuberculous; the under side
is soft and contains all the vital and locomotory organs. Immediately
upon being taken from the water the soft under parts seem to shrink away
and nothing substantial remains but the upper surface. This is
perforated with pores, through which the water enters to all parts of
the body by channels. Very near the center is a small opening through
which the water is admitted to a strong, rather elastic, tube, which is
encircled by a series of rings. Now turn the star fish over and you can
see that this tube opens into a ring about the mouth, while similar
tubes stretch out to the arms. From these cross tubes little fibers
extend, terminating in discs. These are the true organs of locomotion,
and are called ambulacra. They move very slowly and are not at all
clumsy, but have even been called graceful by some naturalists.
A portion of these ambulacra are made fast by suction while the rest of
the body is drawn forward; then the first are relaxed and the process
repeated, thus they travel in the deep waters.
It is quite evident that the five bright red eyes at the tip of each ray
are of some use in helping them on their journeys; but just how much
they can see is not quite known. When a large object appears before them
they prepare to surmount it, often going up very steep sides and down
again as easily as though on a level stretch, often standing on the tip
of one ray and sometimes on the five, thus resembling a five-legged
stool.
The heart, situated near the opening on the back, is supplied with a set
of blood vessels. They also have respiratory organs and a nervous
system, but, judging from the manner they endure vivisection, their
nervous system must be of a very low order, for if they are broken in
pieces the missing parts will soon grow again—in fact, they do not seem
to be disturbed in the least no more than if it were a cast-off garment,
and evidently go about as happy with the remaining rays as with the
complete body, and, what is still more strange, the broken ray will grow
a complete set of arms and a new body. This is one way of reproduction,
so if you wish to kill a star fish don’t break it in pieces. The only
sure way of making an end to their lives is to drop them in fresh water,
when they immediately die.
It is very interesting to watch them care for their eggs. These are kept
in pouches at the base of the rays, and when emitted through an opening
there provided, are actually brooded as a hen her chicks, by arching the
central part of the body and bending the rays down, and if the eggs are
scattered they take great pains to collect them again, often traveling
long distances for them.
The star fish consumes a large amount of food; you would hardly think
one stomach could care for so much, but each ray has an additional
stomach, and all need food. Their favorite food is the whelk, a small
black-shelled, snail-like mollusk. Indeed, they eat many varieties of
the mollusk.
They are also very fond of oysters. You would be interested to watch the
star fish as he slowly works his way along until directly over the
oyster, then folds his five arms around it, holding it firmly in place,
then pushing out his stomach, through his mouth, he wraps it around the
unfortunate oyster, and by the power of suction the oyster is drawn from
the shell and digested and the shell cast away. You can easily see what
a nuisance they must be in an oyster bed.
They are known as the opossum of the sea, as they often appear to be
quite dead when they are very much alive. If you wish to be sure, put
him on his back, and if alive you will soon see a number of
semitransparent globular objects beginning to move, reaching this way
and that. These are the ambulacra seeking to regain their normal
position. If you see no motion, you may safely conclude that he is an
extinguished star.
Rest H. Metcalf.