Star-fishes.
(OPHIURIDAE AND ASTERIADAE.)
'As there are stars in the sky, so there are stars in the sea.'--LINK.
XVIII.
There are not a few persons still to be met with, who believe that
man and the lower animals appeared simultaneously upon the face of
the earth. Geology most forcibly proves the error of such an idea,
for although the fossilized remains of every other class of organized
beings have been discovered, human bones have nowhere been found.
This fact, though deeply interesting, is perhaps not more so than
many others which this wonderful science has unfolded. What can be
more startling to the student for instance, than the information that
for a long period, it may be thousands of years, no species of fish
whatever inhabited the primeval seas? True it is that certain creatures
occupied the shallows and depths of ocean, but these were of the lowest
type. The most conspicuous were the coral polypes, which even then as
now were ever industriously building up lasting monuments of their
existence, as the Trilobites, a group of Crustacea, and the Crinoids,
or Lily-stars.
The last-mentioned group of animals were analogous to the present tribe
of Star-fishes, and are now nearly extinct. The body of the Lily-star,
which resembled some beautiful radiate flower, was affixed to a long,
slender stalk, composed of a series of solid plates superposed upon
one another, bound together by a fleshy coat, and made to undulate
to and fro in any direction at the will of the animal. The stalk
was firmly attached to some foreign substance, and consequently the
Crinoid Star-fish, unlike its modern representative, could not rove
about in search of prey, but only capture such objects as came within
reach of its widely expanded arms. 'Scarcely a dozen kinds of these
beautiful creatures,' observes Professor Forbes, 'now live in the seas
of our globe, and individuals of these kinds are comparatively rarely
to be met with; formerly they were among the most numerous of the
ocean's inhabitants,--so numerous that the remains of their skeletons
constitute great tracts of the dry land as it now appears. For miles
and miles we may walk over the stony fragments of the Crinoidae,
fragments which were once built up in animated forms, encased in
living flesh, and obeying the will of creatures among the loveliest
of the inhabitants of the ocean. Even in their present disjointed and
petrified state, they excite the admiration not only of the naturalist,
but of the common gazer; and the name of stone lily, popularly applied
to them, indicates a popular appreciation of their beauty.' Each
wheel-like joint of the fossil Encrinite being generally perforated
in the centre, facility is thus afforded for stringing a number of
these objects together like beads, and in this form the monks of old,
according to tradition, used the broken fragments of the lily-stars as
rosaries. Hence the common appellation of St Cuthbert's Beads, to which
Sir Walter Scott alludes,--
'On a rock by Lindisfarn
St. Cuthbert sits, and toils to frame
The sea-born beads that bear his name.'
One solitary species of the Crinoid Star-fishes has of late years been
found to flourish in our own seas; it is, however, affixed to a stalk
(pedunculated) only in the early periods of its existence.
When first discovered by Mr. Thompson in its infant state, the
_Pentacrinus Europæus_ was believed to be a distinct animal. It was
taken attached to the stems of zoophytes of different orders, and
measured about three-fourths of an inch in height. In form it resembled
a minute comatula mounted on the stalk of a Pentacrinus. Subsequent
research has proved that the little stranger was merely the young state
of the feather star _Comatula rosacea_, and that although for a certain
period attached to a slender waving stem, the Pentacrinus, when arrived
at a certain stage of development, feels fully able to start life on
its own accord, and hence takes opportunity to break off its early
ties, and become a free animal, dependent upon its own exertions for
subsistence.
It is no uncommon thing, as a late writer forcibly remarks, in the
inferior classes of the animal kingdom, to find animals permanently
attached from the period of their birth, and during all their
existence. Familiar examples of this occur in the oyster, and various
other bivalve shell-fish, as well as in numerous compound zoophytes. We
likewise meet with races which are free and locomotive in their first
stages, and afterwards become permanently fixed; but an animal growing
for a period in the similitude of a flower on a stem, and then dropping
from its pedicle, and becoming during the remainder of its life free
and peripatetic, is not only new, but without any parellel in the whole
range of the organized creation.
The Comatula, or as it is commonly called, the Rosy Feather-star, is
allowed to be without exception the most lively of all the star-fishes.
Its movements in swimming are said to resemble exactly the alternating
strokes given by the medusa to the liquid element, and have the same
effect, causing the animal to raise itself from the bottom, and to
advance back foremost even more rapidly than the medusa. It has ten
very slender rays with numbers of long beards on the sides. The body,
which is of a deep rose colour, is small and surrounded with ten little
filiform rays. The extremities of these organs are shaped like claws,
by means of which the animal attaches itself to various kinds of
sea-weed, and other submarine objects.
The adult Comatula generally measures about five inches across its
fully expanded rays.
Before treating of what are termed the _true_ Star-fishes, we require
to dwell briefly upon an intermediate family named by Professor Forbes
the _Ophiuridæ_, 'from the long serpent or worm-like arms, which are
appended to their round, depressed, urchin like bodies.... They hold
the same relation to the Crinoidea that the true Star-fishes hold to
the Sea-Urchins. They are spinigrade animals, and have no true suckers
by which to walk, their progression being effected (and with great
facility) by means of five long flexible-jointed processes placed at
regular distances around their body, and furnished with spines on the
sides and membraneous tentacula. These processes are very different
from the arms of the true Star-fishes, which are lobes of the animal's
body, whereas the arms of the Ophiuridæ are super-added to the body,
and there is no excavation in them for any longation of the digestive
organs.'[16]
[16] British Star-fishes.
The British Ophiuridæ are now classed under two genera; of the Ophiuræ,
or Sand-stars only two species (_O. texturata_ and _O. albida_) are
found on our shores; and the Ophicomæ, or Brittle-stars, of which there
are ten.
An extraordinary feature, characteristic of all the above-mentioned
animals, is the great tendency which they have to mutilate themselves,
and throw their limbs about in fragments on the slightest provocation.
If a specimen be handled, a certain number of fragments will assuredly
be cast off. If the rays become entangled in sea-weed, or even if the
water in which the animal resides happens to become impure, the same
disastrous result follows, until nothing but the little circular disc
remains. As a set off against this weakness, both the Ophiuræ and the
Brittle-stars possess reproductive powers of a high order. Hence it not
unfrequently happens that if each and all the rays of a specimen be
rejected, the animal will live on, and eventually, perhaps, become a
complete and perfect star-fish.
The best means of preserving an Ophiura is to let the devoted animal
remain for a time expanded in sea-water, then with a small pair of
forceps lift it carefully up, and plump it into a bath of cold 'fresh'
water, letting it lie there for about an hour. The animal speedily
dies, as if poisoned, in the fresh liquid, in a state of rigid
expansion. Some writers recommend that, at this stage, the specimen
should be dipped for a moment into boiling water, and then dried in a
current of air; but I have never been able to detect any great benefit
arising from the adoption of the process.
When examining any of the Brittle-stars, I have always found it an
excellent plan to raise them up by aid of the forceps applied to the
disc. By this means a specimen may be moved about without any fear
of mutilation; whereas if the fingers be used as forceps, an unhappy
result will assuredly follow.
The _Ophiocoma rosula_, figured on Plate 9, will serve to convey to
the reader a general idea of this class of animals. Its popular title
is the Common Brittle-star, indicative of the inherent fragility of the
species, as also of their prevalent appearance at the sea-shore; but,
though so exceedingly 'common,' we must at the same time in justice
add, that the _O. rosula_ exceeds in beauty many other species which
are rare, and consequently more highly prized by the collector.
It is very abundant on all parts of the British coast, and is often
found in clusters upon the stems of _L. digitata_, and as frequently
upon the under side of boulders. In dredging, the Brittle-star is an
unfailing prize. It is a marvellous sight when the scrapings of the
ocean bed are spread out upon the dredging-board for examination,
to see hundreds of these singularly delicate creatures twisting and
twining about in all directions,--over each other's bodies, through the
weed, sand, shells, and mud, and strewing fragments of their snake-like
arms upon every surrounding object.
At the mere mention of 'Star-fishes,' the most uninitiated reader will
at once realize in his mind's eye a tolerably correct notion of the
form of these curious productions of the marine animal kingdom, even
although he had never seen a living or dead specimen.
The body of the animal is divided into rays, like the pictured form of
one of the heavenly stars, and the fancied resemblance is most apparent
in the Asteridæ, or true Star-fishes, of which we are now about to
speak.
This wonderful race of animals, for their beauty of colour, elegance
of shape, and peculiarity of structure, possess a great degree of
interest, not only to the naturalist, but also to the casual observer
by the sea-side.
There are fourteen British species of Asteriadæ, which are arranged
under four families, namely--the Urasteriæ, the Solasteriæ, the
Gonasteriæ, and the Asteriæ. This group contains no less than eight
generic types, clearly distinguished from each other by certain
characters, 'derived from the outline of the body, the number of rows
of suckers in the avenues, and the structure and arrangement of the
spines covering the surface and bordering the avenues.'
There are four species of Star-fishes belonging to the genus Uraster,
the most common of which is the _Uraster rubens_, or Common Cross-fish.
No person in the habit of visiting the sea-shore can be unfamiliar with
the likeness of this creature, which is generally seen lying wedged
in some rocky crevice, or among the Fuci, there patiently waiting the
return of the tide.
At such a time, the Devil's-hand (as the Irish people term it), does
not appear by any means attractive. If placed in water, however, its
appearance becomes wonderfully improved.
Here is a small specimen, just brought from the sea-shore at
Cockburnspath (a most romantic and delightful locality, situated on
the coast of Berwickshire). It is neatly wrapped up in a mantle of
sea-weed. Freed of its verdant envelope, I deposit the youthful Rubens
upon his back--'willy-nilly'--in a tumbler partly filled with clear
sea-water, and then proceed to watch its movements through a magnifier.
At a glance we perceive that each of its five rays is grooved on its
lower surface, and filled with minute perforations, through which is
gradually protruded a multitude of fleshy suckers, knobbed at the end.
It is by aid of these organs that the animal grasps its food, and
changes its position, as we shall presently see. One of the rays is now
slowly lifted up and moved about in various directions, while from its
extreme point the suckers are extended to the utmost limit. No sooner
do they touch the side of the vessel than they are firmly fixed and
contracted. A _point d'appui_ being thus gained, the animal is enabled
by degrees to draw its body round, so as to get another regiment of
suckers into play, and, by such plan of operations being repeated,
the animal is eventually enabled to 'right itself,' and crawl up the
polished surface of the glass.
Generally, when the Star-fish is disturbed, or placed on a dry piece
of stone, the suckers are withdrawn into the body, leaving no signs
of their previous existence except a series of minute tubercles. In
fact, the Asterias, although enabled to adhere with great tenacity to
any foreign object when immersed in water, possesses but little power
to retain its hold if the fluid be removed. Hence the young zoologist,
keeping this peculiarity in mind, should not too hurriedly return a
verdict of 'Found dead,' when he meets with a helpless specimen upon
the beach, for in all likelihood, were the creature to be laid for a
few minutes in a rock-pool, it would soon exhibit signs of returning
animation.
A simpler, though not so sure a test for ascertaining whether a
Star-fish be living or not, is to handle the specimen. If it feels soft
and flabby, it is dead; but if tolerably firm to the touch, it may be
'recalled to life,' by the means pointed out.
It may not be out of place to chronicle here a singular circumstance
which the writer has often verified in connection with the true
Star-fishes. It is this. When any captured specimens have been placed
in confinement, no matter how large or small such might be, they never
moved through the liquid element with a tithe of the rapidity that I
well knew they were capable of. At the sea-side, I have seen a specimen
of the Cross-fish glide through the water so nimbly, yet withal so
gracefully, that I have felt inclined to rank natation among the few
other acomplishments of which the species can boast.
The _Uraster rubens_ is also popularly known as 'Five Fingers.' For
ages past it has been subject to the bitter denunciation of fishermen
and others, for the injury which it is said to inflict upon oysters.
At one time, according to Bishop Spratt, the Admiralty Court laid
penalties upon those engaged in the oyster-fishing who did not
tread under their feet, or throw upon the shore, a fish they call a
Five-Finger, resembling a spur-rowel, because that fish gets into the
oysters when they gape, and sucks them out. Poets have also endeavoured
to perpetuate the vulgar opinion:--
'The prickly Star-fish creeps with fell deceit,
To force the Oyster from his close retreat,
Whose gaping lids their widened void display;
The watchful Star thrusts in a pointed ray--
Of all its treasures robs the rifled case,
And empty shells the sandy hillock grace.'
Even yet the oyster fishermen at certain localities wreak all
possible vengeance upon the 'submarine Dando's,' for their supposed
gourmandizing propensities. I say _supposed_, for although so
many naturalists have studied the question, it is not, up to the
present time, satisfactorily settled. Some deny the alleged tendency
altogether, while less sceptical observers are unable to understand
the mode in which the Star-fish could injure an animal apparently so
capable of self-defence as the oyster. According to certain authors,
the Star-fish encircles the oyster with its five fingers, and by some
clever process of suction destroys the unfortunate mollusc. Others,
again, maintain that the first step of the attack is the injection
of some marine chloroform between the shells of the oyster, and that
during the insensibility that follows, the Star-fish effects an
entrance.
As this is an interesting subject, perhaps the reader would like to
have the exact words which are used by two celebrated naturalists, one
of whom attempts to vindicate the character of the Asteridæ, the other
to blacken it.
Sir John Dalyell--a high authority upon all matters of marine
zoology--shrewdly remarks: 'I have not heard it suggested that the
Star-fish possesses any kind of solvent compelling the bivalves
to sunder. Neither can its hostility be very deadly to the larger
univalves, from the distance to which they are enabled to retreat
within their portable dwellings. Their general habits are, to force the
shells of smaller bivalves asunder, and to devour the contents; they
likewise consume the substance of ordinary fishes entire; nevertheless,
as far as I am yet aware, their destruction of oysters is destitute of
evidence. The Star-fish sometimes shows an eversion of stomach, or of
some membrane of it. Whether this may be the means of affecting their
prey, merits investigation.'
Professor Jones, who affirms that in the latter suggestion Sir J.
Dalyell has nearly hit upon the true solution of the problem, thus
gives what _he_ considers to be the correct mode of procedure on the
part of the Star-fish: 'Grasping its shell-clad prey between its rays,
and firmly fixing it by means of its prehensile suckers, it proceeds
deliberately to turn its stomach inside out, embracing in its ample
folds the helpless bivalve, and perhaps at the same time instilling
some torpifying fluid, for the shells of the poor victim seized soon
open, and it then becomes an easy prey.'
Now, many fishermen with whom I have conversed hold the same opinion as
Bishop Spratt, and believe that when the oyster is gaping the Star-fish
insinuates a finger, and hastily scrapes out the delicious mouthful;
nay, further maintain that the Star-fish is far from being successful
at all times, very often, especially when there has only been one ray
inserted, the frightened oyster grasps it with all his might, and
obliges his discomfited opponent to retire minus a limb.
If the writer might venture to suggest an opinion, he would express
his belief that the following is the correct account of the state of
matters. He believes with the fishermen that frequently the star-fish
begins his attack by inserting an arm, but he does not believe that the
oyster under such circumstances escapes with life. Let us suppose the
star-fish to have succeeded in insidiously introducing a ray within the
shell of the apathetic oyster, and that the oyster immediately resented
such intrusion by closing his shell with all the force he can exert.
The opposite argument at this stage is, that the intruder is obliged
from _pain_ to abandon his hold, and even pay for his audacity by the
forfeit of a limb. But against this we advance the notorious fact, that
the star-fish, like so many marine creatures of a similar organization,
is remarkably indifferent to pain. I therefore believe the true
explanation to be, that the oyster being unable to sustain such
continued muscular exertion for nearly so long a time as the star-fish
can tolerate the pressure upon its ray, the latter is consequently, in
the long run, successful.
The number of rays in the several genera of the true Star-fishes is
extremely various. In the genus _Uraster_, as we have seen, five is
the predominant number. If we turn to the two species which comprise
the genus _Cribella_, we still find the quintuple arrangement adhered
to. In _Solaster endeca_, on the contrary, the rays vary from nine
to eleven, and even reach as high as twelve or fifteen in _Solaster
papposa_.
In the genus _Palmipes_ we have the pentagonal form, it is true, but
the space between each ray is filled up, so as to resemble the webbed
foot of a bird, hence the popular title of this solitary species,
'The Bird's-foot Sea-star.' 'It is the flattest of all its class, and
when alive it is flexible like a piece of leather.' Passing by the
'Cushion-stars' (which have five _angles_--it seems a misnomer to call
them rays), which connect the true Star-fishes with the Sea-Urchins,
we come lastly to the 'Lingthorn,' _Luidia fragillisima_, with its
seven rays. This is the animal of which Professor Forbes discourses so
pleasantly about its winking derisively at his despairing endeavours
to preserve even a small portion of what at that time was his maiden
specimen. The Luidia is even more brittle--more regardless of its
wholeness, than the _Ophiuræ_, which renders the capture of a perfect
specimen a most difficult task.