Borojevia cerebrum (Haeckel, 1872)

Fig. 4; Table 4

Ascaltis cerebrum Haeckel, 1872: 54.

Auloplegma cerebrum Haeckel, 1872: 55.

Ascaltis decipiens Haeckel, 1872: 55.

Ascaltis gyrosa Haeckel, 1872: 55.

Ascetta cerebrum – Bianco 1888: 386. — Lendenfeld 1891: 206 — Bidder 1891: 628.

Clathrina cerebrum – Minchin 1896: 359. — Borojević 1967: 192. — Borojević et al. 1968: 31. — Solé- Cava et al. 1991: 382. — Klautau & Valentine 2003: 14. — Longo & Pronzato 2011: 219.

Leucosolenia cerebrum – Kirk 1896: 207. — Breitfuss 1897b: 210; 1898c: 172; 1935: 8. — Dendy & Row 1913: 724. — Burton 1933: 236; 1963: 186. — Topsent 1934: 7; 1936: 17.

Leucosolenia decipiens – Dendy & Row 1913: 725. — Ferrer 1918: 9.— Breitfuss 1935: 9. — Tanita 1943: 78.

Borojevia cerebrum – Klautau et al. 2013: 452.

non Clathrina cerebrum – Borojević 1971: 526 (non Clathrina cerebrum).

Type specimen

ADRIATIC SEA: Lesina (Croatian: Island of Hvar), Haeckel collection (PMJ-Inv. Nr. Porif. 156, syntype /ethanol).

Material examined

ADRIATIC SEA: Vrulja Cove, 43°24'01.3" N, 16°53'10.9" E, 10 m, collected by V. Nikolić, 24 Aug. 2011 (PMR-17808; IRB-CLB 33 = UFRJPOR 7539).

Colour

Light yellow in life and in ethanol.

Description

Cormus is composed of regular and tightly anastomosed tubes (Fig. 4A). Large water-collecting tubes are present. The skeleton consists of triactines, a few tetractines and tripods, which in fact are large triactines. It has no special organisation (Fig. 4B).

Spicules (Table 4)

TRIPODS. Regular (equiangular and equiradiate). The tripods of analysed specimens are more similar to large triactines than to true tripods with an elevated centre. Actines are conical, straight, with sharp tips (Fig. 4C). Size: 91.8/ 11.2 µm.

TRIACTINES. Regular (equiangular and equiradiate). Actines are slightly conical to conical, straight, with sharp tips. Sometimes they are slightly undulated near the tips (Fig. 4D). Size: 84.6/ 8.9 µm.

TETRACTINES. Regular (equiangular and equiradiate). Actines are slightly conical to conical, straight, with sharp tips. Sometimes they are slightly undulated near the tips. It is possible to recognise two types of tetractines: small (Fig. 4E) and large (Fig. 4F). Large tetractines are the same size as tripods. The apical actine of the tetractines is shorter than the basal ones, slightly conical, sharp and frequently curved only at the tip. It is ornamented with few (ca. six) spines, which are large, conical and cover only the actine).

last third of the apical actine. (Fig. 4G). Size: 81.9/ 8.5 µm (basal actine); 46.8/ 5.4 µm (apical

Ecology

The specimen was collected on a semi-vertical hard limestone bottom.

Remarks

Similar to other species of Borojevia, B. cerebrum has thin, regular and tightly anastomosed tubes forming the cormus. The oscula are present at the end of water-collecting tubes. The skeleton is composed of tripods (with the characteristic elevated centre or similar to large triactines), triactines and tetractines. Individuals of B. cerebrum always have spines on the apical actine of their tetractines; however, in the same individual some tetractines may be smooth. In B. cerebrum, the spines are not very abundant; they are large and scattered, only near the tip of the apical actine. The Adriatic and Mediterranean specimens of B. cerebrum formed a well supported clade in the ITS tree (Fig. 16), separated from the clade comprising B. brasiliensis (Solé-Cava, Klautau, Boury-Esnault, Borojević & Thorpe, 1991).

Borojevia cerebrum is the type species of the genus. Its type locality is Lesina (Island of Hvar) and it commonly occurs in the Mediterranean and the Adriatic Sea. The type specimen of B. cerebrum (PMJ-Inv. Nr. Porif. 156) is not very well preserved (Klautau & Valentine 2003); thus, we got a great opportunity to redescribe this species from near its type locality.

Analyses of other individuals of B. cerebrum from several sites in the Adriatic and Mediterranean Seas verify that the shape of the tripods is very variable. It varies from the characteristic shape of tripods, with stout actines and elevated centre, to only large triactines. This kind of variability may be assigned to polymorphism or plasticity. Indeed, Haeckel (1872) proposed two varieties of B. cerebrum (as Ascaltis cerebrum), based on the presence of either characteristic tripods or large triactines. The first variety he called B. cerebrum var. gyrosa, while the other one he considered B. cerebrum var. decipiens. Dendy & Row (1913) elevated B. cerebrum var. decipiens to species level (as Leucosolenia decipiens) and kept B. cerebrum (as L. cerebrum) as a valid species. The variety gyrosa had not been oficially elevated to the status of species; however, it was mentioned as Ascaltis gyrosa in a synonym list of B. cerebrum made by Burton (1963: 186).

Considering that both varieties were proposed only to differentiate specimens with characteristic tripods from those with only large triactines and that we found this morphological variation inside individuals and among specimens placed within the same species, we propose here the synonymisation of B. decipiens with B. cerebrum.