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(Pallas, 1766)

Species Overview

Haliclona (Haliclona) oculata (Pallas, 1766) is an elegantly branching, soft sponge with a rose-brown or yellow-brown colour. The height may be up to 30 cm. The branches are somewhat flattened. The surface is velvety. Oscules are small and arranged in rows along the branches. It occurs in shallow subtidal, occasionally intertidal habitats, often associated with rather silted water. It is a northern species occurring all over the North Atlantic (including North America), reaching its southern limits along the Atlantic coasts of Portugal.

Taxonomic Description

Colour: Light brown, dark-yellow, often with a greenish tinge, sometimes reddish.
Shape, size, surface and consistency: Basically the sponge consist of solid branches growing from a short stalk which is attached to the substratum with a pedicel (Spongia oculata). There is a considerable variation in the number and the degree of fusing of the branches. The branches may remain isolated along their entire length (Haliclona oculata Zeeland), or fuse to such a degree that the sponge becomes flabelliform (Chalina oculata). Commonly the diameter of the branches decreases towards the blind ends, but there is also variation in this feature. There is a strong tendency of the branches to be laterally compressed. The oscules are always small, 1-3 mm, and mainly arranged on the narrower sides of the compressed branches. They are not or only slightly elevated. When the sponge is flabelliform, the oscules are mainly situated on the margins of the blade; it happens quite frequently that the oscules are then situated at the summit of small mammiform elevations, making the margins of the blades undulating. The sponge may reach a considerable size, commonly it is between ca. 10 cm and 30 cm in height. Surface very smooth and velvety to the touch, slightly hispid. Consistency rather soft but elastic, not fragile; towards the base the sponge becomes firmer; the stalk is very firm and incompressible.
Kaandorp (1991, 1994) modelled growth forms of this species using fractal geometry methods.
Spicules: Short, fat cigar-shaped oxeas with short and sharp points; stylote and strongylote modifications are very common: ca. 80-145 x 4.5-12 µm.
Skeleton: (Haliclona oculata skeldraw) Ectosomal skeleton mostly absent, but occasionally some dermal spicules are arranged into a vague tangential isodictyal network. Choanosomal skeleton very regular, with uni-to paucispicular primary and unispicular secondary lines. Spongin commonly abundant, clearly visible; towards the base it forms the main part of the skeleton.
Reproduction: Larvae (parenchymella) are produced in summer and fall (July till November), they are elongate (260-470 µm), white, and have a bare posterior pole (Wapstra and Van Soest, 1987).
Gemmules of ca. 500-1000 µm in diameter, dark orange, are normally present in dense clusters at the base of the stalk. The gemmules are probably not functional, because the sponges survive during the winter; however, it happens sometimes that a new sponge is growing out of these gemmules (this was observed in a number of unregistered specimens in the BMNH collection, collected by F. Rowe at Portsmouth, Great Britain).
Ecology: In the infralittoral, to ca. 100 m, on rocky and sandy bottom, attached to stones, Mytilus etc. It can tolerate low salinity and turbid water with suspended silt.
Distribution: Atlantic coast of Canada and North America, from the Gulf of St. Lawrence to North Carolina, west coast Portugal, France, the Netherlands, British Isles, Shetland, Faroe, Denmark, west coast Sweden, north coast Norway, Spitsbergen, Bear Island, White Sea, Kara Sea. Probably occurring in the entire arctic and subarctic area (Koltun, 1959, and others).
Etymology: oculata (Latin) = with eyes, referring to the rows of oscules.
Type specimen information: Holotype probably lost. In BMNH two dried specimens (BMNH 1841:1:13:46 and 1873.7.24.4 as Chalina).

Remarks

Haliclona (Haliclona) oculata is well characterized morphologically by its compressed, solid branches and the linear arrangement of the small oscules on the narrower sides of the branches. The skeletal architecture is rather variable, due to the high variation in the amount of spongin, but still characteristic; the form of the oxeas is highly consistent. The species differs from the other sympatric, stalked chalinid Haliclona (Haliclona) urceolus by its solid branches, the abundant spongin and smaller spicules.
The high number of synonyms of H. oculata is not surprising because of its variable growth form and common occurrence in the study area. The number of species descriptions is an example of the tendency of earlier taxonomists to describe every growth form as a separate species. Kaandorp (1992, 1994) demonstrated that the various growth forms are the product of constant small pressures from environmental factors.
The conspecifity of Halichondria cervicornis, Spongia dichotoma, Isodictya pygmaea, Diplodemia vesicula, Chalina grantii, Isodictya varians (pars), and Chalina flemingii with H. oculata is for the greater part established on basis of study of the original specimens. Johnston's (1842) material of H. cervicornis agrees completely with Johnston's figure and leaves no doubt about their identity. Pallas' (1766) description of Spongia cervicornis, however, does not conform to H. (H.) oculata. Most probably it is an axinellid. Most conspicuous differences between S. cervicornis and H. (H.) oculata are the apparently strongly hispid surface in S. cervicornis, the rounded branches which are only slightly compressed at the base, and the greyish colour.
The specimen of Spongia dichotoma in the Copenhagen collection may very well be Linnaeus' original specimen (from Newport, Rhode Island). The label is probably in Linnaeus' handwriting, but it is partly unreadable. The sponge (dried) is completely wrinkled into a roundish bush of numerous branches; the degree of fusing of these branches is rather small. The skeleton consists mainly of spongin fibres which are 30-40 µm thick and which contain single spicules at regular distances. The oxeas are typically cigar-shaped and measure 110x7.5 µm.
The holotype of Diplodemia vesicula consists only of gemmulae on the inside of a shell, with a few spongin fibres holding them together. The gemmulae are 800-1000 µm, densely filled with oxeas of ca. 110x4.8 µm. The spongin fibres are 25-45 µm thick, enclosing a few oxeas of ca. 95-125 x 4 µm. The conspecifity of Diplodemia vesicula with H. (H.) oculata is evident and was already mentioned by Topsent (1894a: 16).
All the specimens of Isodictya varians, except for the holotype, conform to H. oculata; they are all very delicatcly branched. BMNH 1910.1.1.349 is most similar to the figured sponge of Bowerbank, 1874, pl. LXXXVIII fig. 1, although it is somewhat larger and even more branched than the figured sponge. The oxeas are short and very fat: 95 x 10 µm; the amount of spongin is moderate. The specimen designated as the holotype by Bowerbank (Bowerbank, 1874: 124) conforms to Haliclona (Reniera) cinerea. This specimen belongs to Johnston's collection of Halichondria cinerea, but it has, together with the three other specimens of this collection, been re-identified by Bowerbank. The complex history of these specimens and its bearing on later confusions concerning H. (R.) cinerea are explained to full extent in de Weerdt and Stone, 1987.
The holotype of Chalina flemingii (designated as the type by Bowerbank, 1874: 173) conforms also to H. cinerea. The only other specimen of C. flemingii (BMNH 1877.5.21.2079) is H. (H.) oculata. It is branched and stalked, and has irregularly scattered, very small oscules. The skeleton is strongly fibrous and consists of spongin fibres of 8-16 µm, partly containing oxeas of reduced size, partly containing oxea of the usual form and size (120 x 7 µm). This specimen is described by Bowerbank (1874: 357). In his description Bowerbank mentioned the similarity to Chalina oculata but because of the irregularly dispersed oscules, which have a lateral linear arrangement in C. oculata he assigned the specimen to C. flemingii.
The identity of Veluspa polymorpha var. gracilis, var. digitata and var. arctica is established on the basis of descriptions and figures. They are, therefore, only tentatively considered synonymous with H. (H.) oculata. V. polymorpha var. gracilis Miklucho-Maclay (1870: 5) is described as thin branches which fuse into bundles; oscules in rows, sometimes on papillae; the skeleton a regular network of spicula (oxeas and strongyles) which are at the nodes connected by spongin. No size of the spicules is given. The description and figures of the sponges and the skeleton evidently point to H. oculata. The same holds true for V. var. digitata and var. arctica. Miklucho-Maclay distinguished these forms from the foregoing one by their larger size and higher development of spongin. The three species are described from the Pacific coast of Russia (Sea of Okhotsk); V. polymorpha var. digitata also from Bear Island.
The identity of Pachychalina caulifera (type material not found in ZMA) is also tentatively established on Vosmaer's description and figures and on the ZMK specimens identified by Lundbeck. Vosmaer described the species, from the Barents Sea, as having an elongated, compressed, semi-ramose body, with oscules on one side. His figures of the skeleton and spicula (Vosmaer, 1882b, pl. III figs. 64-66) conform to H. (H.) oculata. The fourth ZMK specimen identified by Lundbeck as P. caulifera (from Vestmansund, Greenland) is very similar in habit to the other specimens, but it conforms to Pachychalina (= Isodictya) excelsa Schmidt (1870). This species is extremely similar in habit to sturdy forms of H. (H.) oculata, but differs from it by the thick, coarse spicule tracts and by the possession of chelae. It is probably conspecific with Isodictya palmata.
Source: De Weerdt, 1986

Haliclona oculata