Читать книгу Glimpses of Ocean Life; Or, Rock-Pools and the Lessons they Teach - John Harper - Страница 10
III.
ОглавлениеNo marine objects have become more universally popular of late years than Sea Anemones. Certainly none better deserve the attention which has been, and is daily bestowed upon them by thousands of amateur naturalists, who cannot but be delighted with the wondrous variety of form, and the beauteous colouring which these zoophytes possess.
A stranger could scarcely believe, on looking into an aquarium, that the lovely object before him, seated motionless at the base of the vessel, with tentacula expanded in all directions, was not a simple daisy newly plucked from the mountain side, or it may be a blooming marigold or Anemone from some rich parterre—instead of being, in reality, a living, moving, animal-flower.
One great advantage which the Actiniæ possess over certain other inhabitants of the sea-shore, at least to the eye of the naturalist, is the facility with which specimens may be procured for observation and study. Scarcely any rock-pool near low water mark but will be found to encompass a certain number of these curious creatures, while some rocky excavations of moderate size will at times contain as many as fifty. Should the tide be far advanced, the young zoologist need not despair of success, for, by carefully examining the under part of the boulders totally uncovered by the sea, he will frequently find specimens of the smooth anemone, contracted and hanging listlessly from the surface of the stone, like masses of green, marone, or crimson jelly.
The Actiniæ, and especially examples of the above mentioned species, are extremely hardy and tenacious of life, as the following interesting narrative will prove.
The late Sir John Dalyell writing in 1851, says, 'I took a specimen of A. mesembryanthemum (smooth anemone) in August 1828, at North Berwick, where the species is very abundant among the crevices of the rocks, and in the pools remaining still replenished after the recess of the tide. It was originally very fine, though not of the largest size, and I computed from comparison with those bred in my possession, that it must have been then at least seven years old.'
Through the kindness of Dr. M'Bain, R.N., the writer has been permitted to enjoy the extreme pleasure of inspecting the venerable zoophyte above alluded to, which cannot now be much under thirty-eight years of age!
In the studio of the above accomplished naturalist, 'Granny' (as she has been amusingly christened) still dwells, her wants being attended to with all that tenderness and care which her great age demands.
Sir J. Dalyell informs us that during a period of twenty years this creature produced no less than 344 young ones. But, strange to say, nearly the fortieth part of this large progeny consisted of monstrous animals, the monstrosity being rather by redundance than defect. One, for instance, was distinguished by two mouths of unequal dimensions in the same disc, environed by a profusion of tentacula. Each mouth fed independently of its fellow, and the whole system seemed to derive benefit from the repast of either. In three years this monster became a fine specimen, its numerous tentacula were disposed in four rows, whereas only three characterize the species, and the tubercles of vivid purple, regular and prominent, at that time amounted to twenty-eight.
From the foregoing statement we learn that this extraordinary animal produced about 300 young during a period of twenty years, but, 'wonder of wonders!' I have now to publish the still more surprising fact, that in the spring of the year 1857, after being unproductive for many years, it unexpectedly gave birth, during a single night, to no less than 240 living models of its illustrious self!
This circumstance excited the greatest surprise and pleasure in the mind of the late Professor Fleming, in whose possession this famous Actinia then was.
Up to this date (January 1860) there has been no fresh instance of fertility on the part of Granny, whose health, notwithstanding her great reproductive labours and advanced age, appears to be all that her warmest friends and admirers could desire. Nor does her digestive powers exhibit any signs of weakness or decay; on the contrary, that her appetite is still exquisitely keen, I had ample opportunity of judging. The half of a newly opened mussel being laid gently upon the outer row of tentacula, these organs were rapidly set in motion, and the devoted mollusc engulphed in the course of a few seconds.
The colour of this interesting pet is pale brown. Its size, when fully expanded, no larger than a half-crown piece. It is not allowed to suffer any annoyance by being placed in companionship with the usual occupants of an aquarium, but dwells alone in a small tank, the water of which is changed regularly once a week. This being the plan adopted by the original owner of Granny, is the one still followed by Dr. M'Bain, whose anxiety is too great to allow him to pursue any other course, for fear of accident thereby occurring to his protegée.
A portrait of Granny, drawn from nature, will be found on Plate 2.
A. troglodytes[2] (cave-dweller) is a very common, but interesting object. The members of this species are especial favourites with the writer, from their great suitableness for the aquarium. They vary considerably in their appearance from each other. Some are red, violet, purple, or fawn colour; others exhibit a mixture of these tints, while not a few are almost entirely white. There are certain specimens which disclose tentacula, that in colour and character look, at a little distance, like a mass of eider-down spread out in a circular form. A better comparison, perhaps, presents itself in the smallest plumage of a bird beautifully stippled, and radiating from a centre. The centre is the mouth of the zoophyte, and is generally a light buff or yellow colour. From each corner, in certain specimens, there branches out a white horn that tapers to a very delicate point, and is oft times gracefully curled like an Ionic volute, or rather like the tendril of a vine.
In addition to the pair of horns alluded to, may sometimes be seen a series of light-coloured rays, occurring at regular intervals around the circumference of the deep tinted tentacula, and thereby producing to the eye of the beholder a most pleasing effect.
As a general rule, never attempt to capture an anemone unless it be fully expanded, before commencing operations. By this means you will be able to form a pretty accurate estimate of its appearance in the tanks. This condition of being seen necessitates, of course, its being covered with water, and, consequently, increases the difficulty of capturing your prize, especially when the creature happens to have taken up a position upon a combination of stone and solid rock, or in a crevice, or in a muddy pool, which when disturbed seems as if it would never come clear again.
It is, in consequence, advisable to search for those situated in shallow water, the bottom of which is covered with clean sand. When such a favourable spot is found, take hammer and chisel and commence operations. Several strokes may be given before any alarm is caused to the anemone, provided it be not actually touched. No sooner, however, does the creature feel a palpable vibration, and suspect the object of such disturbance, than, spurting up a stream of water, it infolds its blossom, and shrinks to its smallest possible compass. At same time apparently tightens its hold of the rock, and is, indeed, often enabled successfully to defy the utmost efforts to dislodge it.
After a little experience, the zoologist will be able to guess whether he is likely to succeed in getting his prize perfect and entire; if not, let me beg of him not to persevere, but immediately try some other place, and hope for better fortune.
Although apparently sedentary creatures, the Actiniæ often prove themselves to be capable of moving about at will over any portion of their subaqueous domain. Having selected a particular spot, they will ofttimes remain stationary there many consecutive months. A smooth anemone that had been domesticated for a whole year in my aquarium thought fit to change its station and adopt a roving life, but at last 'settled down,' much to my surprise, upon a large mussel suspended from the surface of the glass. Across both valves of the mytilus the 'mess.' attached by its fleshy disc, remained seated for a considerable length of time. It was my opinion that the mussel would eventually be sacrificed. Such, however, was not the case, for on the zoophyte again starting off on a new journey, the mollusc showed no palpable signs of having suffered from the confinement to which it had so unceremoniously been subjected.
The appearance of this anemone situated several inches from the base of the vessel, branching out from such an unusual resting-place, and being swayed to and fro, as it frequently was, by the contact of a passing fish, afforded a most pleasing sight to my eye. Indeed, it was considered for a while one of the 'lions' of the tank, and often became an object of admiration not only to my juvenile visitors, but also to many 'children of larger growth.'
There is a curious fact in connection with the Actiniæ which deserves to be chronicled here. I allude to the apparent instinct which they possess. This power I have seen exercised at various times. The following is a somewhat remarkable instance of the peculiarity in question.
In a small glass vase was deposited a choice A. dianthus, about an inch in diameter. The water in the vessel was at least five inches in depth. Having several specimens of the Aplysiæ, I placed one in companionship with the anemone, and was often amused to observe the former floating head downward upon the surface of the water. After a while it took up a position at the base of the vase, and remained there for nearly a week. Knowing the natural sluggishness of the animal, its passiveness did not cause me any anxiety. I was rather annoyed, however, at observing that the fluid was becoming somewhat opaque, and that the Dianthus remained entirely closed, and intended to find out the cause of the phenomena, but from some reason or other failed to carry out this laudable purpose at the time. After the lapse of a few days, on looking into the tank, I was delighted to perceive the lace-like tentacula of the actinia spread out on the surface of the water, which had become more muddy-looking than before.
I soon discovered that the impurity in question arose from the Aplysia (whose presence in the tank I had forgotten) having died, and its body being allowed to remain in the vessel in a decaying state. The deceased animal on being removed emitted an effluvium so intolerably bad that it seemed like the concentrated essence of vile odours. The water, of course, must have been of the most deadly character, yet had this most delicate of sea-anemones existed in it for several consecutive days.
In order further to test how long my little captive would remain alive in its uncongenial habitation, I cruelly refused to grant any succour, but must own to having felt extremely gratified at perceiving, in the course of a few days, that instead of remaining with its body elongated to such an unusual extent, the Dianthus gradually advanced along the base, then up the side of the vessel, and finally located itself in a certain spot, from which it could gain easy access to the outer atmosphere.
After this second instance of intelligence (?) I speedily transferred my pet to a more healthy situation.
Having procured a small colony of Actiniæ, you need be under no anxiety about their diet, for they will exist for years without any further subsistence than is derived from the fluid in which they live. Yet strange as the statement will appear to many persons, the Actiniæ are generally branded with the character of being extremely greedy and voracious. 'Nothing,' says Professor Jones, 'can escape their deadly touch. Every animated thing that comes in contact with them is instantly caught, retained, and mercilessly devoured. Neither strength nor size, nor the resistance of the victim, can daunt the ravenous captor. It will readily grasp an animal, which, if endowed with similar strength, advantage, and resolution, could certainly rend its body asunder. It will endeavour to gorge itself with thrice the quantity of food that its most capacious stomach is capable of receiving. Nothing is refused, provided it be of animal substance. All the varieties of the smaller fishes, the fiercest of the crustacea, the most active of the annelidans, and the soft tenants of shells among the mollusca, all fall a prey to the Actiniæ.'
This is a sweeping statement, and, although corroborated by Sir J. Dalyell and others, is one that requires to be received with a certain degree of caution. It most certainly does not apply to A. bellis, A. parisitica, A. dianthus, troglodytes, or any other members of this group; and to a very limited extent only is it applicable to A. coriacea or A. mesembryanthemum.
As may readily be conceived, the writer could not keep monster specimens, such as are often found at the sea-shore; but surely if the statement were correct that, as a general rule, the actiniæ eat living crabs, the phenomenon would occasionally occur with moderate-sized specimens, when kept in companionship with a mixed assembly of crustaceans. Yet in no single instance have I witnessed a small crab sacrificed to the gluttony of a small anemone.
With regard to A. mesembryanthemum, A. bellis, and A. dianthus, they get so accustomed to the presence of their crusty neighbours, as not to retract their expanded tentacula when a hermit crab, for instance, drags his lumbering mansion across, or a fiddler crab steps through the delicate rays, like a sky terrier prancing over a bed of tulips.
Thus much I have felt myself called upon to say in defence of certain species of Actiniæ; but with regard to A. crassicornis, I must candidly own the creature is greedy and voracious to an extreme degree.
Like many other writers, I have seen scores of this species of Actiniæ that contained the remains of crabs of large dimensions, but at one time considered that the latter were dead specimens, which had been drifted by the tide within reach of the Actiniæ, and afterwards consumed. That such, indeed, was the correct explanation in many instances I can scarcely doubt, from the disproportionate bigness of the crabs as compared with the anemones, but feel quite confident, that in other instances, the crustacea were alive when first caught by their voracious companions.
To test the power of the 'crass.,' I have frequently chosen a specimen well situated for observation, and dropped a crab upon its tentacula. Instantly the intruding animal was grasped (perhaps merely by a claw), but in spite of its struggles to escape, was slowly drawn into the mouth of its captor, and eventually consumed. In one case, after the crab had been lost to view for the space of three minutes only, I drew it out of the Actinia, but although not quite dead, it evidently did not seem likely to survive for any length of time.
In collecting Actiniæ great care should be taken in detaching them from their position. If possible, it is far the better plan not to disturb them, but to transport them to the aquarium on the piece of rock or other substance to which they may happen to be affixed. This can in general be done by a smart blow of the chisel and hammer.
Should the attempt fail, an endeavour should be made to insinuate the finger nails under the base, and so detach each specimen uninjured. This operation is a delicate one, requiring practice, much patience, and no little skill. We are told by some authors that a slight rent is of no consequence, since the anemone is represented as having the power of darning it up. It may be so, but for my part I am inclined in other instances to consider the statement more facetious than truthful. In making this remark, I allude solely to the disc of the animal, an injury to which I have never seen repaired. On the other hand, it is well known that certain other parts may be destroyed with impunity. If the tentacula, for instance, be cut away, so great are the reproductive powers of the Actiniæ, that in a comparatively short space of time the mutilated members will begin to bud anew.
'If cut transversely through the middle, the lower portion of the body will after a time produce more tentacula, pretty near as they were before the operation, while the upper portion swallows food as if nothing had happened, permitting it indeed at first to come out at the opposite end; just as if a man's head being cut off would let out at the neck the bit taken in at the mouth, but which it soon learns to retain and digest in a proper manner.'
The smooth anemone being viviparous, as already hinted, it is no uncommon circumstance for the naturalist to find himself unexpectedly in possession of a large brood of infant zoophytes, which have been ejected from the mouth of the parent.
There is often an unpleasant-looking film surrounding the body of the Actiniæ. This 'film' is the skin of the animal, and is cast off very frequently. It should be brushed away by aid of a camel-hair pencil. Should any rejected food be attached to the lips, it may be removed by the same means. When in its native haunts this process is performed daily and hourly by the action of the waves. Such attention to the wants of his little captives should not be grudgingly, but lovingly performed by the student. His labour frequently meets with ample reward, in the improved appearance which his specimens exhibit. Instead of looking sickly and weak, with mouth pouting, and tentacula withdrawn, each little pet elevates its body and gracefully spreads out its many rays, apparently for no other purpose than to please its master's eye.
A. mesembryanthemum (in colloquial parlance abbreviated to 'mess.'), is very common at the sea-shore. It is easily recognised by the row of blue torquoise-like beads, about the size of a large pin's head, that are situated around the base of the tentacula. This test is an unerring one, and can easily be put in practice by the assistance of a small piece of stick, with which to brush aside the overhanging rays.
A. crassicornis grows to a very large size. Some specimens would, when expanded, cover the crown of a man's hat, while others are no larger than a 'bachelor's button.' Unless rarely marked, I do not now introduce the 'crass.' into my tanks, from a dislike, which I cannot conquer, to the strange peculiarity which members of this species possess, of turning themselves inside out, and going through a long series of inelegant contortions. Still, to the young zoologist, this habit will doubtless be interesting to witness. One author has named these large anemones 'quilled dahlias;' and the expression is so felicitous, that if a stranger at the sea-side bear it in mind, he could hardly fail to identify the 'crass.,' were he to meet with a specimen in a rocky pool. Not the least remarkable feature in connection with these animal-flowers, is the extraordinary variety of colouring which various specimens display.
A. troglodytes, is seldom found larger than a florin. Its general size is that of a shilling. From the description previously given, the reader will be able to make the acquaintance of this anemone without any trouble whatever.
A. dianthus (Plumose anemone), is one of the most delicately beautiful of all the Actiniæ; it can, moreover, be very readily identified in its native haunts. Its colour is milky-white,—body, base, and tentacula, all present the same chaste hue. Specimens, however, are sometimes found lemon-coloured, and occasionally of a deep orange tint. Various are the forms which this zoophyte assumes, yet each one is graceful and elegant.
The most remarkable as well as the most common shape, according to my experience, is that of a lady's corset, such as may often be seen displayed in fashionable milliners' windows. Even to the slender waist, the interior filled with a mass of lace-work, the rib-like streaks, and the general contour, suggestive of the Hogarthian line of beauty, the likeness is sustained.
When entirely closed, this anemone, unlike many others, is extremely flat, being scarcely more than a quarter of an inch in thickness; indeed, so extraordinary is the peculiarity to which I allude, that a novice would have great difficulty in believing that the object before him was possessed of expansive powers at all, whereas, in point of fact, it is even more highly gifted in this respect than any other species of Actiniæ.