The Romance of Natural History, Second Series

by Philip Henry Gosse

In the spring we frequently see among herbage a great uncouth beetle of a dark blue-black hue, with short wing-cases and long, heavy body, which discharges drops of yellow fluid when handled, and is therefore called the Oil-beetle (Melöe proscarabæus). The early stages of this beetle have much affinity with those of the Stylops. The beetle lays a number of yellow eggs in a hole in the earth; these produce little active six-footed larvæ, resembling lice, which crawl to the summit of dandelion and other flowers in the sunshine, and await the visit of a bee. On the arrival of one, the active grub immediately clings to its body, and is carried to the nest, not, however, to introduce itself parasitically into the body of the bee-grub, but to feed on the provision which the parent bee has stored up for its own young. Thus it becomes very fat, and grows to a size much larger than that of the full-grown bee-grub, having early dropped its six long clinging legs, which, having performed their proper function in catching hold of a bee, are no longer needed. It changes to a perfect beetle in autumn, lies in the bee's nest all the winter, and emerges in the spring.

The large jelly-like Medusæ which in summer are seen floating around our coasts, driving themselves along by alternate contractions and expansions of their umbrella, are frequently infested by little creatures of widely different organisation, Crustaceans belonging to the genera Hyperia and Metoecus. On the beautiful Chrysaora of the southern coast I have seen the Metoecus medusarum, a little shrimp about half-an-inch in length, with enormous lustrous green eyes, which takes up his residence in the cavities of the sub-umbrella,—dwelling in them as in so many spacious and commodious apartments, of which he takes possession, evidently without asking leave of the landlord, or paying him even the compliment of a peppercorn rent. Here he snugly ensconces himself, and feels so much at home, that he is not afraid to leave his dwelling now and then, to take a swim in the free water, returning to his chamber after his exercise; and here he rears his numerous family, which, in the form of tiny white specks, very much unlike their parents in shape, stud the membranes of the jelly-fish.

But, what is stranger still, Mr M'Cready has recently discovered in the harbour of Charleston in North America, a Medusa which is parasitic upon another Medusa. Cunina octonaria does not swim freely in the water, but inhabits the cavity of the bell of Turritopsis nutricula. "Not only does the latter furnish a shelter and dwelling-place for the larvæ during their development; it also serves as their nurse, by allowing the parasites, whilst adhering by their tentacles, to draw nourishment out of its mouth by means of a large proboscis. In point of fact, the relation between them is of so unprecedented a nature, that the author may well be excused for having at first taken the impudent parasite for the gemmiparous progeny of the sheltering Medusa. The youngest state of this parasitic Medusa observed by the author formed a ciliated body of clavate form, adhering to the cavity of the bell by means of the slender stalk in which it terminated. The first change consists in the emission, from the thick end, of two slender flexible tentacles, and in the formation of a central cavity by liquefaction. At this stage of development, the author frequently observed gemmation taking place at the thicker end, sometimes frequently repeated. Subsequently the number of tentacles becomes doubled. These bend together over the clavate extremity, and are then employed, instead of the thin end of the body, in adhering to the cavity of the sheltering Medusa. The thin extremity then acquires a mouth, and may be recognised as a stomachal peduncle, which is employed, as above indicated, in obtaining nourishment. The morphological nature of the proboscis becomes still more distinct when, after the lapse of some little time, an annular fold makes its appearance immediately under the tentacles, which is recognisable from its form, and from the formation in it of (eight) otolithic capsules, as the first indication of the future bell. Simultaneously with the otolithic capsules, four rudimentary tentacles make their appearance between the four tentacles. The Medusa remains in this stage of development for a long time. The bell gradually becomes more freely developed, and at last, by the reduction and entire disappearance of the stomachal peduncle, becomes the most essential part of the Medusa, after it has left its previous dwelling-place in the bell of the Turritopsis. The bell nevertheless retains for some time its earlier lobed form and unequal tentacles."[231]

More remarkable even than this association is the fact that certain true Fishes habitually reside in the stomachs of star-fishes. This circumstance, which had been observed in the Oriental Archipelago by MM. Quoy and Gaimard, and by Dr Bleeker, has recently been confirmed by Dr Doleschall, who has written a very interesting Memoir on it.

This learned naturalist states that the fact of the connexion between the fish and the star-fish is well known to most of the fishermen in Amboyna, and that he was able to obtain a sufficiency of specimens for examination; but as the star-fishes (and with them the fishes) speedily died in confinement, he was unable to make continuous observations upon them in a living state. Of the results of his observations he gives the following summary:—

"The fish stands to the star-fish in a definite relation which cannot be the object of observation. Why the little fish should always seek the stomachal cavity of one and the same species of star-fish, and not that of various species, is a mystery. It is well known that Crustaceans of the genus Pagurus inhabit the empty shells of Mollusca; but we find on the shore the same species of Pagurus in the shells of the most various genera and species.

"I have never met with Oxybeles gracilis, on the contrary, in any other species of star-fish than Culcita discoidea. The fish was described by Bleeker under the above name in 'Natuurkundig Tijdschrift,' vii., p. 162. The author proceeds to state that neither he nor any one else in Amboyna has ever captured the fish under other circumstances, or while swimming freely in the sea; but upon this Dr Bleeker remarks that many of his specimens of Fierasfer Brandesii, and all those of Fierasfer (Oxybeles) gracilis and F. lumbricoides, were obtained by him along with other fishes, and were probably taken while swimming freely in the sea.

"Upon the habits of Oxybeles gracilis the author goes on to say that it is certain that this animal passes the greater part of its existence in the stomach of the star-fish, rarely shewing itself outside of this, and then probably at night. That it does come out occasionally, appears from the fact that in two cases the author observed the fish with a portion of its body outside the cavity of the star-fish, and in the act of creeping in.

"The same observations shewed that the fish, in returning to its concealment, passes along the furrow of the lower surface of one of the arms leading to the mouth of the star-fish, which is wide enough, when the tentacles are retracted, to leave room for the passage of the slender body of the Oxybeles. This fact likewise proves that the Oxybeles does not get into the stomach of the Culcita by accident.

"If a living Culcita be cut in two, the fish is seen moving freely in the cavity of its body. If it be taken out, it immediately seeks the shade. If the two halves of the Culcita (still alive) be placed in the water, the fish will soon be seen to draw towards them, in order to get into the cavity of the star-fish. When exposed to the light, it is uneasy, and its iris contracts excessively. The author never found two fishes in the same star-fish.