Freshwater Sponges, Hydroids & Polyzoa Part 15

6. Spongilla hemephydatia*, _Annandale_.

_Spongilla hemephydatia_, Annandale, Rec. Ind. Mus. iii, p.

275 (1909).

[Ill.u.s.tration: Fig. 12.--Gemmule and spicules of _Spongilla hemephydatia_ (from type specimen).]

_Sponge_ soft, fragile, amorphous, of a dirty yellow colour, with large oscula, which are not conspicuously raised above the surface but open into very wide horizontal channels in the substance of the sponge. The oscular collars are fairly well developed, but the subepidermal s.p.a.ce is not extensive.

_Skeleton_ diffuse, consisting of very fine radiating fibres, which are crossed at wide and irregular intervals by still finer transverse ones; very little chitinoid substance present.

_Spicules._ Skeleton-spicules smooth, slender, sharply pointed at both ends, nearly straight. No true flesh-spicules. Gemmule-spicules straight or nearly so, cylindrical, or constricted in the middle, obscurely pointed or blunt, clothed with short, sharp, straight spines, which are very numerous but not markedly longer at the two ends; these spicules frequently found free in the parenchyma.

_Gemmules_ numerous, small, free, spherical, yellow, with a well-developed granular coat (in which the spicules are arranged almost horizontally) and external to it a fine membrane which in preserved specimens becomes puckered owing to unequal contraction; each gemmule with a single aperture provided with a straight, rather wide, but very delicate foraminal tubule.

_Measurements of Spicules and Gemmules._

Length of skeleton-spicule 0.313 mm.

Breadth of skeleton-spicule 0.012 "

Length of gemmule-spicule 0.062 "

Breadth of gemmule-spicule 0.004 "

Diameter of gemmule 0.313-0.365 mm.

This sponge in its general structure bears a very close resemblance to _Spongilla crateriformis_.

TYPE in the collection of the Indian Museum.

HABITAT. Growing on weeds at the edge of the Sur Lake, Orissa, October 1908. Only one specimen was taken, together with many examples of _S.

lacustris_ subsp. _reticulata_, _S. carteri_ and _S. cra.s.sissima_.

7. Spongilla crateriformis* (_Potts_).

_Meyenia crateriforma_, Potts, P. Ac. Philad. 1882, p. 12.

_Meyenia crateriformis, id., ibid._ 1887, p. 228, pl. v, fig. 6, pl. x, fig. 5.

? _Ephydatia crateriformis_, Hanitsch, Nature, ii, p. 511 (1895).

_Ephydatia crateriformis_, Weltner, Arch. Naturg. lxi (i), pp. 122, 134 (1895).

? _Ephydatia crateriformis_, Hanitsch, Irish Natural. iv, p.

125, pl. iv, fig. 5 (1895).

_Ephydatia indica_, Annandale, J. Asiat. Soc. Bengal, 1907, p. 20 (figures poor).

_Ephydatia indica, id._, Rec. Ind. Mus. i, pp. 272, 279, 388, 391 (1907).

_Ephydatia crateriformis_, Scharff, European Animals, p. 34 (1907).

_Ephydatia crateriformis_, Annandale, P. U.S. Mus. x.x.xvii, p. 402, fig. 1 (1909).

_Sponge_ very fragile, forming soft irregular ma.s.ses on the roots and stems of water-plants, between which it is sometimes stretched as a delicate film, or thin layers or cushions on flat surfaces. Oscula large, flat, circular, or of irregular shape, opening into broad horizontal ca.n.a.ls, which at their distal end are superficial and often covered by the external membrane only. Colour white, yellowish, greyish, or blackish.

_Skeleton_ very delicate; radiating fibres rarely consisting of more than two parallel spicules; transverse fibres far apart, frequently consisting of single spicules; very little spongin present.

[Ill.u.s.tration: Fig 13.--Spicules of _Spongilla crateriformis_.

A. From specimen taken in July in a tank on the Calcutta maidan. B. From type specimen of _Ephydatia indica_ taken in the Indian Museum tank in winter. Both figures 240.]

_Spicules._ Skeleton-spicules feebly curved, slender, as a rule irregular in outline, sometimes almost smooth; the ends as a rule sharply pointed, often constricted off and expanded so as to resemble spear-heads, occasionally blunt. No true flesh-spicules.

Gemmule-spicules often free in the parenchyma, cylindrical, slender, very variable in length in different sponges, straight or nearly so, as a rule with an irregular circle of strong straight or recurved spines at either end resembling a rudimentary rotule, and with shorter straight spines scattered on the shaft, sometimes without the rudimentary rotule, either truncate at the ends or terminating in a sharp spine.

_Gemmules_ small, free, each surrounded by a thick granular layer in which the spicules stand upright or nearly so, and covered externally by a delicate but very distinct chitinous membrane; no horizontal spicules; foramen situated at the base of a crater-like depression in the granular coat, which is sometimes raised round it so as to form a conspicuous rampart; a short, straight foraminal tubule.

The shape of the spicules is extremely variable, and sponges in which they are very different occur in the same localities and even in the same ponds. It is possible that the differences are directly due to slight changes in the environment, for in one pond in Calcutta a form with _Spongilla_-like gemmule-spicules appears to replace the typical form, which is common in winter, during the hot weather and "rains." I have not, however, found this to be the case in other ponds. Perhaps _S.

hemephydatia_ will ultimately prove to be a variety of this very variable species, but its smooth and regular skeleton-spicules and short-spined gemmule-spicules afford a ready method of distinguishing it from _S. crateriformis_. The two sponges are easily distinguished from all others in the subgenus _Euspongilla_ by the upright and regular arrangement of their gemmule-spicules, for although in _S. proliferens_ and _S. travancorica_ some of the gemmule-spicules are nearly vertical, their arrangement is always irregular, a large proportion of the spicules make an acute angle with the inner coat of the gemmule and a few as a rule lie parallel to it. The systematic position of _S.

crateriformis_ is almost exactly intermediate between _Euspongilla_ and _Ephydatia_, to which genus it has. .h.i.therto been a.s.signed. I think, however, that taking into consideration its close relationship to _S.

hemephydatia_, it is best to a.s.sign it to _Spongilla_, as its rudimentary rotules never form distinct disks. I have examined some of Potts's original specimens from different American localities and can detect no constant difference between them and Indian specimens.

TYPES in the United States National Museum; co-types in Calcutta.

GEOGRAPHICAL DISTRIBUTION.--This sponge was originally described from North America (in which continent it is widely distributed) and has been recorded from the west of Ireland with some doubt. In India and Burma it is widely distributed. BENGAL, Calcutta and neighbourhood (_Annandale_); Sonarpur, Gangetic delta (_Annandale_); BOMBAY PRESIDENCY, Igatpuri Lake, W. Ghats (alt.i.tude _ca._ 2,000 feet) (_Annandale_); MADRAS PRESIDENCY, neighbourhood of Madras town (_J. R. Henderson_); Museum compound, Egmore (Madras town) (_Annandale_); near Bangalore (alt. _ca._ 3,000 ft.), Mysore State (Annandale); Ernakulam, Cochin (_G. Mathai_): BURMA, k.a.w.kareik, interior of Amherst district, Tena.s.serim, and the Moulmein waterworks in the same district (_Annandale_).[AB]

[Footnote AB: Mr. C. A. Paiva, a.s.sistant in the Indian Museum, has lately (March 31st, 1911) obtained specimens of _S. crateriformis_ in a small pond of fresh water on Ross Island in the Andaman group. The existence of this widely distributed species on an oceanic island is noteworthy.]

BIOLOGY.--_S. crateriformis_ flourishes in Calcutta throughout the year.

Here it is usually found adhering to the roots of water-plants, especially _Pistia_ and _Limnanthemum_. In the case of the former it occurs at the surface, in that of the latter at the bottom. When growing near the surface or even if attached to a stone at the bottom in clear water, it is invariably of a pale yellowish or greyish colour. When growing on the roots of _Limnanthemum_ in the mud of the Gangetic alluvium, however, it is almost black, and when growing in the reddish muddy waters of the tanks round Bangalore of a reddish-brown colour.

This appears to be due entirely to the absorption of minute particles of inorganic matter by the cells of the parenchyma. If black sponges of the species are kept alive in clean water, they turn pure white in less than a week, apparently because these particles are eliminated. When growing on stones the sponge, as found in India, often conforms exactly with Potts's description: "a filmy grey sponge, branching off here and there ... yet with a curious lack of continuity...."

The wide efferent ca.n.a.ls of this sponge afford a convenient shelter to small crustacea, and the isopod _Tachaea spongillicola_, Stebbing (see p.

94), is found in them more abundantly than in those of any other sponge.

This is especially the case when the sponge is growing at the bottom. On the surface of the sponge I have found a peculiar protozoon which resembles the European _Trichodina spongillae_ in general structure but belongs, I think, to a distinct species, if not to a distinct genus.

Subgenus B. EUNAPIUS, _J. E. Gray_.

_Eunapius_, J. E. Gray (_partim_), P. Zool. Soc. London, 1867, p. 552.

_Spongilla_ (_s. str._), Vejdovsky, in Potts's "Fresh-Water Sponges," P. Ac. Philad. 1887, p. 172.

_Spongilla_ (_s. str._), Weltner, in Zacharias's Tier- und Pflanzenwelt des Susswa.s.sers, i, p. 214 (1891).

_Spongilla_ (_s. str._), Annandale, Zool. Jahrb., Syst.

xxvii, p. 559 (1909).

TYPE, _Spongilla carteri_, Carter.

Spongillae in which the gemmules are covered with layers of distinct polygonal air-s.p.a.ces with chitinous walls.