Trikentrion africanum, Soest, Rob van, Carballo, Jose Luis & Hooper, John, 2012

Soest, Rob van, Carballo, Jose Luis & Hooper, John, 2012, Polyaxone monaxonids: revision of raspailiid sponges with polyactine megascleres (Cyamon and Trikentrion), ZooKeys 239, pp. 1-70 : 46-48

Trikentrion africanum sp. n. Figs 26 A–E

Trikentrion laeve ; Burton 1948: 757 (Congo); Burton 1956: 142.

Not: Trikentrion laeve Carter 1879.

Material examined.

Type specimen: Holotype BMNH 1939.2.20.9, preserved in alcohol.

Type locality: République du Congo, Pointe Noire, approximately at 4.7667°S, 11.8333°E, coll. E. Darteville, June 1938.

Description.

Upright flattened branch with two or three short side projections (Fig. 26A), with wider base and a cut-off upper ending, possibly the specimen is only a fragment as base and apex look damaged. Length of holotype 6.5 cm, diameter 1.5 cm at the base, 1 cm higher up. Side projections only on one side of the branch, less than 1 cm long and 0.5 cm thick, with rounded apex. Surface uneven, somewhat hispid. No apparent oscules. Consistency firm. Colour (alcohol) red-brown.

Skeleton: a dense mass of polyactines, towards the periphery surrounding long thin styles and short thin styles, which are embedded in the skeleton more so than in other Trikentrion species. No oxeas present, but T-shaped polyactines with very short basal clade appear to have taken the position of oxeas.

Spicules: long thin styles, short thin styles, polyactines, trichodragmas.

Long thin styles (Fig. 26B), smooth, straight, usually broken, so only a small number (five) were available for length measurements, 295 –870.4– 1394 × 9 –14.6– 24 µm.

Short thin styles (Fig. 26C, C1), straight or gradually curved, 192 –241.1– 358 × 2 –2.3– 3 µm.

Polyactines (Fig. 26D), basically three-claded, with the basal clade provided with strong conical spines near the apex. Two major morphological types appear dominant, those with almost equiangular outline (Fig. 26D1), and T-shaped forms with very short basal clade (Fig. 26D2), which is occasionally entirely smooth; basal cladi 27 –51.3– 96 × 11 –13.7– 21 µm, lateral cladi 33 –96.3– 121 × 9 –13.9– 19 µm.

Trichodragmas (Figs 26E, E1), straight or sometimes curved sinuously, up to 50 or more individual raphides with apical spines, 49 –54.4– 61 × 5 –7.7– 11 µm.

Etymology.

The name is anadjective referring to the type locality.

Distribution.

République du Congo.

Ecology.

Shallow water

Discussion.

Burton (1948, 1956) assigned this material to the relatively unknown species Trikentrion laeve Carter without any morphological information. This is obviously wrong, a.o. because that species has abundant oxea megascleres, lacking in the present material. Carter’s Trikentrion laeve was expressly differentiated from Trikentrion muricatum in its possession of long thin styles, which are indeed absent in Trikentrion muricatum . Both Trikentrion muricatum and Trikentrion laeve were described and illustrated by Carter to have a strong complement of oxeas (see also above). Their function appears to have been entirely taken over by the polyactine spicules in the present material.

The lack of choanosomal genuine oxeas is shared with Californian Trikentrion catalina and Trikentrion helium , but these species have flabelliform or bladed shape and much larger polyactine spicules.