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(Bowerbank, 1866)

Species Overview

Haliclona (Rhizoniera) indistincta (Bowerbank, 1866) is a flat, thickly encrusting greenish brown soft sponge. Oscules are mostly flush with the surface and small, but occasionally are elevated and larger. The surface is slightly sticky, and coarsely punctate. It may be quite common under intertidal stones, where it may form extensive patches.

Taxonomic Description

Colour: Greenish-brown.
Shape, size, surface and consistency: The sponge is always thickly encrusting, forming patches from a few cm to 20-25 cm in diameter. Oscules are few, irregularly scattered, not or only slightly elevated, circular, 1.5-3 mm in diameter. Surface strongly punctate, slightly irregular and shaggy; with clearly visible exhalant canals radiating to the oscules (Haliclona indistincta V). Consistency softly friable. When touched the surface is sticky, slimy.
Spicules: Rather slender and fusiform oxeas: 110-150 x 3-7.5 µm.
Skeleton: (Haliclona indistincta skdrw) Ectosomal skeleton absent. Choanosomal skeleton close meshed, with pauci-multispicular primary and unispicular secondary lines. Many spicules in confusion. Spongin: very little, confined to the nodes of the spicules.
Reproduction: Larvae are pink-violet (with white apical pole), 250-500 µm in size, apparently uniformly ciliated (Lévi, 1956; Wapstra and Van Soest, 1987).
Ecology: Mainly found at the undersides of intertidal and shallow subtidal rocks.
Distribution: British Isles, Atlantic coasts of France, ?Amphi-Atlantic.
Etymology: The name was given because of the variability of the form and the general lack of distinctive characters.
Type specimen information: Lectotype (per Burton, 1947: 369): BMNH 1930:7:3:366, labeled Isodictya indistincta, Norman Collection, Diamond Ground, Hastings, England.

Remarks

Unfortunately the lectotype of Isodictya indistincta is an atypical representation of the species, and it is very difficult to trace the morphological characteristics from this specimen. It is figured in Bowerbank, 1874, pl. LI fig. 1, (Isodictya indistincta) and when it is compared with the specimen of fig. 2 of the same plate it is difficult to believe that the two specimens belong to the same species. The sponge of fig. 2 reminds strongly of Haliclona (Rhizoniera) viscosa. This specimen (BMNH 1930:7:3:363) is also cushion-shaped, 3 x 4 x 1.2 cm, but densely covered with seven volcano-shaped elevations which have a small osculum at their summit. The oscules are obviously placed in series. The specimen is far less fragile than the lectotype, and the surfacc is covered with a thin transparant film which reminds strongly of dried mucous. However, the skeletal architecture of the two specimens is similar, as well as the size and shape of the oxeas (146.7 x 5.9 µm in the lectotype, 143.3 x 5.0 µm in the other specimen) The sponge of fig. 2 is furthermore obtained from a dredge haul at Guernsey; H. (R.) viscosa is typically a species which is easily collected by swab dredging since it prefers bare rock faces. Another thing to be mentioned here is the conspicuous absence of a species description by Bowerbank which conforms to H. (R.) viscosa. The species is not uncommon in the British Isles and the Channel Islands. It is most likely that Bowerbank's collection of Isodictya indistincta is a mixture of H. (R.) indistincta and H. (R.) viscosa.
H. (R.) indistincta is probably conspecific with the North American species Haliclona (Rhizoniera) canaliculata Hartman, 1958a, described from Branford, New England and Connecticut. H. (R.) canaliculata is described as a thickly encrusting, brownish sponge, with oscules flush with the surface and with exhalant canals radiating to the oscules. The oxeas are fusiform and measure 74-148 x 3.3-8.2 µm; they form vertical, multispicular tracts, held together by small quantities of spongin, with unispicular secondary lines, and with many spicules in confusion (partly literally cited from Hartman). The species reminds strongly of H. (R.) indistincta. Maybe H. (R.) indistincta has been imported from Europe to North America.
Source: De Weerdt, 1986

Haliclona indistincta