STAUROMEDUSAE UK
An online guide to the Stalked jellyfish (Stauromedusae) found
around the coastal waters of the United Kingdom and Ireland.
Includes notes on their identification, and where and how to find them.
On the Structure of Carduella cyathiformis. A contribution to our knowledge of the Lucernariadae. By Prof. Allman, F.R.S., &c. &c.
In the month of August last, during a short sojourn among the Orkney Isles, my attention was directed by Mr. Gilchrist of Stromness, to a little Lucernarian zoophyte, which he had discovered attached to stones near low-water mark, in the neighbourhood of that town. (Very old black and white photograph showing the shoreline at the south of the town)
The little animal proves to be identical with the Lucernaria cyathiformis of Sars; but its characters are such as to convince me that it must be separated from the true Lucernaria, and assumed as the type of a distinct genus in the family of the Lucernariadie. That I am justified in this view, will, I think, appear from the following description: -
Fam., Lucernariadie.
Gen., Carduella, mihi.
(Name. - A diminutive noun from carduus, a thistle, in allusion to its form.)
Gen. Char. - Body stalked ; tentacles capitate, not tufted, springing from within the margin of a circular disc in a single series.
C. cyathiformis, Sars. — Body urceolate; peduncle dilated at its base into a disc for attachment; tentacular circle interrupted at about eight nearly regular intervals, by the non-development of certain tentacles.
Synonym. - Lucernaria cyathiformis, Sars, in Fauna lit. Norveg.; Johnston, Brit. Zooph., 2d Ed., p.475, fig. 86.
Hab. - On stones near low-water-mark.
Localities. - Coast of Norway, Sars; Island of Arran, Scotland, Rev. D. Landsborough; Stromness, Orkney, Mr. Gilchrist and G. I. A.
Carduella cyathiformis is about half an inch in height. The body is hemispherical posteriorly, where it is seated on the summit of the peduncle; it then contracts behind the tentacular circle, and then again expands into a wide circular disc, whose margin is not produced into rays, as in the true Lucernaria, and which has the mouth in its centre. The tentacles, slightly tapering from the base, and each ending in a spherical capitulum, do not, as in Lucernaria, spring from the edge of the cup, but from a circle situated at some distance within it, and in the fully expanded state of the animal extend about as much again beyond it.
The tentacular circle is interrupted at four nearly regular intervals; but all the tentacles are situated in a single circle, and never form tufted groups as in Lucernaria.
Each of the four interruptions in the continuity of the circle of tentacles is caused by a single tentacle having that at each side of it arrested in its development, so as to present under the lens the appearance of little conical papillae (Pl. V, fig. 3, m), while the developed tentacle, situated between the two arrested ones, is invariably bent over the edge of the cup in the expanded state of the animal (figs. 1, 3,) and thus renders the interruptions in the circle still more obvious. Not unfrequently, other interruptions are observed in the tentacular circle, caused by a similar abortion of one or more tentacles; but these are less regular in position and less constant in occurrence, than those just described.
In the centre of the oral disc is a prominent four-lobed mouth, and the extremities of the four generative bands may be seen projecting from below each angle of the mouth, and distinctly visible through the disc, by the greater depth of their colour.
The peduncle is distinctly annulated both in the extended and contracted state, and terminates below in a little disc-like dilatation, by which the animal fastens itself to the rock; but I cannot find that it has the power of detaching itself when it has once become fixed.
The colour of C. cyathiformis is a brownish-red, with the stomach and generative bands conspicuous, by their deeper colour, through the semi-transparent walls of the body; while, just behind the bases of the tentacles, the body is marked by a deep-brown circle; and four paler lines, separated from one another by equal intervals, extend backwards from this circle to the summit of the peduncle.
It was a very frequent thing to meet with two individuals growing from a single basal disc; but this I believe to be a case of simple fusion from contiguity, and not an example of gemmation or other form of zooidal multiplication. (See note below)
Carduella cyathiformis is one of the most elegant members of our littoral fauna, and rarely will the wanderer along the shore at low tides have his search more amply rewarded than by the capture of this charming little zoophyte.
Anatomy. - A transverse section (fig. 4) made about the middle of the body, or a longitudinal section (fig. 3) passing through the axis, shows an outer bell or umbrella (a), traversed in its axis by a quadrilateral, elongated stomach (b). In the walls of this stomach, along each of its four angles, runs a double lobulated band (c), which projects into the cavity of the stomach, and is the seat of the ova or spermatozoa.
From the outer side of the walls of the stomach there extend to the umbrella eight membranous vertical lamellae (figs. 3, 4, d). These are so arranged, that from each of the angles along which one of the four generative bands runs two lamellae are given off, and thence diverging at a wide angle, are attached by their outer edges to the inner surface of the umbrella along a longitudinal ridge (e), which also gives attachment to one of the lamellae of the neighbouring pair. There are thus four of these ridges, each giving attachment to two lamellae, and situated alternately with the four angles of the stomach to which the opposite edges of the lamellae are attached.
The result of this arrangement is the formation of eight spaces, four of which (f) are situated externally, while the other four (g) alternate with these and lie internally.
The four outer spaces are closed above, and their roof thus forms the oral disc (h) of the animal; while the four inner spaces are open, and allow a needle to be passed down along the side of the stomach the whole way as far as the peduncle.
Each of the four ridges, along which the vertical laminae are attached to the inner edge of the umbrella, seems to be traversed through its entire length by a canal. They are visible in the living animal through the walls of the umbrella, where they appear as four pale-coloured lines, extending symmetrically from the summit of the peduncle as far as the tentacular circle.
Running along the bases of the tentacles, so as to form a continuous circle at some distance within the margin of the disc, is a deep reddish-brown line (i), which I have no hesitation in viewing as a circular canal, into which the tubular tentacles all open.
Upon the inner surface of the stomach are eight longitudinal rows of tubular appendages (k), two rows being situated in each of the four intervals between the generative bands. They are finely ciliated on their surface, and have their walls loaded with large thread-cells.
I have not satisfactorily made out the structure of the peduncle; but it seems to present the principal parts demonstrable in the body, namely, the umbrella, stomach, and generative bands, compressed into a smaller space and less distinguishable from one another.
Round the margin of the umbrella runs a band of circular muscular fibres (l), which performs the office of a sphincter in closing the mouth of the umbrella during the contracted state of the animal; while other fibres radiate in the oral disc, where they may be seen converging from the circular canal at the base of the tentacles towards the central stomach.
In the ova (fig. 5), the germinal vesicle and germinal spot are distinct; and the spermatozoa (fig. 6) present a characteristic hydrozoal form, consisting of conical corpuscles, with the caudal filament attached to the broad end of the cone.
Homologies. - As to the true import of the structure now described; it will be easily seen that we have in it a genuine hydrozoal type, notwithstanding a certain superficial resemblance to the structure of the Actinozoa. The point which at first sight seems to remove it most widely from the Hydrozoa, and approximate it to the Actinozoa, will be found in the presence of the vertical lamellae which connect the stomach with the outer wall of the animal. A little attention, however, will show that these must on no account be confounded with the radiating lamellae of an Actinia from which they differ entirely in their arrangement and relations.
The axile stomach of Carduella is exactly the manubrium of a Medusa, while the external body-walls correspond to the umbrella; and if I am correct in my interpretation of the appearances which lead me to believe in the existence of longitudinal and circular canals, we have in them the exact representatives of the radiating and circular canals of the gastro-vascular system of a Medusa.
As to the homology of the oral disc, I cannot help seeing in this muscular membrane the representative of the muscular velum of a gymnophthalmic Medusa, which, instead of being, as in the Medusa, free towards the axis of the animal, is here united to the stomach, while it is at the same time extended and so folded into plaits, as to form by the union of these plaits alternately to the stomach within, and to the umbrella without, the four pairs of vertical lamellae; and although what we know of the development of the velum in the Medusa, can scarcely be said to give any direct support to this view, it certainly is not inconsistent with it.
It will now be seen that it is with the gymnophthalmic, rather than with the steganophthalmic Medusa, that the affinities of Carduella are to be sought. We have, indeed, only to conceive of a gymnophthalmic Medusa, with its stomach (manubrium) united to the umbrella along four equidistant longitudinal lines through the medium of a peculiarly plaited velum, in order to convert it, so far as regards the most important points of its structure, into a Carduella.
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Prof. Allman reports "It was a very frequent thing to meet with two individuals growing from a single basal disc"; see article "On the occurrence of twin-headed specimens of stauromedusae". By David Fenwick (updated 13.05.14.).
