Freshwater Sponges, Hydroids & Polyzoa Part 21

Ost-Ind. i. pp. 32, 46 (1890).

_Ephydatia mulleri_, Weltner (_partim_), Arch. Naturg. lxi (i), p. 125 (1895).

_Ephydatia robusta_, Annandale, J. Asiat. Soc. Bengal, 1907, p. 24, fig. 7.

_Ephydatia mulleri_ subsp. _meyeni_, _id._, Rec. Ind. Mus.

ii, p. 306 (1908).

_Sponge_ hard and firm but easily torn, usually of a clear white, sometimes tinged with green, forming irregular sheets or ma.s.ses never of great thickness, without branches but often with stout subquadrate projections, the summits of which are marked with radiating grooves; the whole surface often irregularly nodulose and deeply pitted; the oscula inconspicuous; the membrane adhering closely to the parenchyma. _The parenchyma contains numerous bubble-cells_ (see p. 31, fig. 2).

_Skeleton_ dense but by no means regular; the radiating fibres distinct and containing a considerable amount of spongin, at any rate in the outer part of the sponge; transverse fibres hardly distinguishable, single spicules and irregular bundles of spicules taking their place.

[Ill.u.s.tration: Fig. 21.--Gemmule and spicules of _Ephydatia meyeni_ (from Calcutta). _a_, Skeleton-spicules; _b_, gemmule-spicules.]

_Spicules._ Skeleton-spicules entirely smooth, moderately stout, feebly curved, sharply pointed. No flesh-spicules. Gemmule-spicules with the shaft as a rule moderately stout, much longer than the diameter of one disk, smooth or with a few stout, straight horizontal spines, which are frequently bifid or trifid; the disks flat, of considerable size, with their margins cleanly and deeply divided into a comparatively small number of deep, slender, triangular processes of different sizes; the shaft extending not at all or very little beyond the disks.

_Gemmules_ spherical, usually numerous and of rather large size; each covered by a thick layer of minute air-s.p.a.ces, among which the gemmule-spicules are arranged vertically, often in two or even three concentric series; a single short foraminal tubule; the pneumatic coat confined externally by a delicate membrane, with small funnel-shaped pits over the spicules of the outer series.

I think that the gemmules found by me in Bhim Tal and a.s.signed to Potts's _Meyenia robusta_ belong to this species, but some of the spicules are barely as long as the diameter of the disks. In any case Potts's description is so short that the status of his species is doubtful. His specimens were from N. America.

_E. meyeni_ is closely related to the two commonest Holarctic species of the genus, _E. fluviatilis_ and _E. mulleri_, which have been confused by several authors including Potts. From _E. fluviatilis_ it is distinguished by the possession of bubble-cells in the parenchyma, and from _E. mulleri_ by its invariably smooth skeleton-spicules and the relatively long shafts of its gemmule-spicules. The latter character is a marked feature of the specimens from the Malay Archipelago a.s.signed by Prof. Max Weber to _E. fluviatilis_; I am indebted to his kindness for an opportunity of examining some of them.

TYPE in the British Museum; a fragment in the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--India and Sumatra. _Localities_:--BENGAL, Calcutta and neighbourhood (_Annandale_); MADRAS PRESIDENCY, Cape Comorin, Travancore (_Trivandrum Mus._): BOMBAY PRESIDENCY, Island of Bombay (_Carter_): HIMALAYAS, Bhim Tal, k.u.maon (alt. 4,500 feet) (_Annandale_).

BIOLOGY.--My experience agrees with Carter's, that this species is never found on floating objects but always on stones or brickwork. It grows in the Calcutta "tanks" on artificial stonework at the edge of the water, together with _Spongilla carteri_, _S. alba_, _S. fragilis_ subsp.

_calcuttana_, and _Trochospongilla latouchiana_. It flourishes during the cold weather and often occupies the same position in succeeding years. In this event the sponge usually consists of a dead base, which is of a dark brownish colour and contains no cells, and a living upper layer of a whitish colour.

The larva of _Sisyra indica_ is sometimes found in the ca.n.a.ls, but the close texture of the sponge does not encourage the visits of other _incolae_.

Genus 4. DOSILIA, _Gray_.

_Dosilia_, J. E. Gray, P. Zool. Soc. London, 1867, p. 550.

TYPE, _Spongilla plumosa_, Carter.

This genus is distinguished from _Ephydatia_ by the nature of the free microscleres, the microscleres of the gemmule being similar in the two genera. The free microscleres consist as a rule of several or many shafts meeting together in several or many planes at a common centre, which is usually nodular. The free ends of these shafts often possess rudimentary rotulae. Occasionally a free microsclere may be found that is a true monaxon and sometimes such spicules are more or less distinctly birotulate. The skeleton is also characteristic. It consists mainly of radiating fibres which bifurcate frequently in such a way that a bush-like structure is produced. Transverse fibres are very feebly developed and are invisible to the naked eye. Owing to the structure of the skeleton the sponge has a feathery appearance.

Gray originally applied the name _Dosilia_ to this species and to _"Spongilla" baileyi_, Bowerbank. It is doubtful how far his generic description applies to the latter, which I have not seen; but although the position of _"Spongilla" baileyi_ need not be discussed here, I may say that I do not regard it as a congener of _Dosilia plumosa_, the free microscleres of which are of a nature rare but not unique in the family.

With _Dosilia plumosa_ we must, in any case, a.s.sociate in one genus the two forms that have been described as varieties, viz., _palmeri_*, Potts from Texas and Mexico, and _brouini_*, Kirkpatrick from the White Nile.

By the kindness of the authorities of the Smithsonian Inst.i.tution and the British Museum I have been able to examine specimens of all three forms, in each case identified by the author of the name, and I am inclined to regard them as three very closely allied but distinct species. Species with free microscleres similar to those of these three forms but with heterogeneous or tubelliform gemmule-spicules will probably need the creation of a new genus or new genera for their reception.

GEOGRAPHICAL DISTRIBUTION.--The typical species occurs in Bombay and Madras; _D. palmeri_ has probably an extensive range in the drier parts of Mexico and the neighbouring States, while _D. brouini_ has only been found on the banks of the White Nile above Khartoum, in Tropical Africa.

17. Dosilia plumosa* (_Carter_).

_Spongilla plumosa_, Carter, J. Bomb. Asiat. Soc. iii, p.

34, pl. i, fig. 2, & Ann. Nat. Hist. (2) iv, p. 85, pl. iii, fig. 2 (1849).

_Spongilla plumosa_, Bowerbank, P. Zool. Soc. London, 1863, p. 449, pl. x.x.xviii, fig. 5.

_Dosilia plumosa_, J. E. Gray, _ibid._ 1867, p. 551.

_Meyenia plumosa_, Carter, Ann. Nat. Hist. (5) vii, p. 94, pl. v, fig. 6 (1881).

_Meyenia plumosa_, Potts, P. Ac. Philad. 1887, p. 233.

_Ephydatia plumosa_, Weltner, Arch. Naturg. lxi (i), p. 126 (1895).

_Ephydatia plumosa_, Petr, Rozp. Ceske Ak. Praze, Trida ii, pl. ii, figs. 29, 30 (text in Czech) (1899).

_Sponge_ forming soft irregular ma.s.ses which are sometimes as much as 14 cm. in diameter, of a pale brown or brilliant green colour; no branches developed but the surface covered with irregular projections usually of a lobe-like nature.

_Skeleton_ delicate, with the branches diverging widely, exhibiting the characteristic structure of the genus in a marked degree, containing a considerable amount of chitin, which renders it resistant in spite of its delicacy.

_Spicules._ Skeleton-spicules smooth, sharply pointed, nearly straight, moderately slender, about twenty times as long as their greatest transverse diameter. Flesh-spicules occasionally amphioxous or birotulate and with a single shaft, more frequently consisting of many shafts meeting in a distinct central nodule, which is itself smooth; the shafts irregularly spiny, usually more or less nodular at the tip, which often bears a distinct circle of recurved spines that give it a rotulate appearance. Gemmule-spicules with long, slender, straight shafts, which bear short, slender, straight, horizontal spines spa.r.s.ely and irregularly scattered over their surface; the rotulae distinctly convex when seen in profile; their edge irregularly and by no means deeply notched; the shafts not extending beyond their surface but clearly seen from above as circular umbones.

[Ill.u.s.tration: Fig. 22.--_Dosilia plumosa._

A=microscleres, 240; B=gemmule as seen in optical section from below, 75. (From Rambha.)]

_Gemmules._ Somewhat depressed, covered with a thick granular pneumatic coat, in which the spicules stand erect; the single aperture depressed.

Each gemmule surrounded more or less distinctly by a circle or several circles of flesh-spicules.

TYPE in the British Museum; some fragments in the Indian Museum.

GEOGRAPHICAL DISTRIBUTION.--Bombay and Madras. Carter's specimens were taken in the island of Bombay, mine at Rambha in the north-east of the Madras Presidency. I have been unable to discover this species in the neighbourhood of Calcutta, but it is apparently rare wherever it occurs.

BIOLOGY.--Carter writes as regards this species:--"This is the coa.r.s.est and most resistant of all the species. As yet I have only found three or four specimens of it, and these only in two tanks. I have never seen it fixed on any solid body, but always floating on the surface of the water, about a month after the first heavy rains of the S.W. monsoon have fallen. Having made its appearance in that position, and having remained there for upwards of a month, it then sinks to the bottom. That it grows like the rest, adherent to the sides of the tank, must be inferred from the first specimen which I found (which exceeds two feet in circ.u.mference) having had a free and a fixed surface, the latter coloured by the red gravel on which it had grown. I have noticed it growing, for two successive years in the month of July, on the surface of the water of one of the two tanks in which I have found it, and would account for its temporary appearance in that position, in the following way, viz., that soon after the first rains have fallen, and the tanks have become filled, all the sponges in them appear to undergo a partial state of putrescency, during which gas is generated in them, and acc.u.mulates in globules in their structure, through which it must burst, or tear them from their attachments and force them to the surface of the water. Since then the coa.r.s.e structure of _plumosa_ would appear to offer greater resistance to the escape of this air, than that of any of the other species, it is probable that this is the reason of my having hitherto only found it in the position mentioned."

It seems to me more probable that the sponges are actually broken away from their supports by the violence of the rain and retain air mechanically in their cavities. The only specimens of _D. plumosa_ that I have seen alive were attached very loosely to their support. In writing of the "coa.r.s.e structure" of this species, Carter evidently alludes to the wide inters.p.a.ces between the component branches of the skeleton.

My specimens were attached to the stem of a water-lily growing in a pool of slightly brackish water and were of a brilliant green colour. I mistook them at first for specimens of _S. lacustris_ subsp.

_reticulata_ in which the branches had not developed normally. They were taken in March and were full of gemmules. The pool in which they were growing had already begun to dry up.

Genus 5. TROCHOSPONGILLA, _Vejdovsky_.

_Trochospongilla_, Vejdovsky, Abh. K. Bohm. Ges. Wiss. xii, p. 31 (1883).

_Trochospongilla_, Wierzejski, Arch. Slaves de Biologie, i, p. 44 (1886).

_Trochospongilla_, Vejdovsky, P. Ac. Philad. 1887, p. 176.

_Meyenia_, Potts (_partim_), _ibid._ p. 210.