Leucascus albus, Cavalcanti, Fernanda F., Rapp, Hans Tore & Klautau, Michelle, 2013

Cavalcanti, Fernanda F., Rapp, Hans Tore & Klautau, Michelle, 2013, Taxonomic revision of Leucascus Dendy, 1892 (Porifera: Calcarea) with revalidation of Ascoleucetta Dendy & Frederick, 1924 and description of three new species, Zootaxa 3619 (3), pp. 275-314 : 294-297

Leucascus albus sp. nov.

Etymology: Latin albus : white. Describing the colour alive.

Diagnosis: Colour alive is white. Microdiactines are present in the skeleton. Atrial skeleton composed of the same proportion of triactines and tetractines.

Synonym: Leucascus simplex : Muricy et al. 1991: 1187.

Type material: UFRJPOR 5252 (holotype; Enseada, Arraial do Cabo, Rio de Janeiro, Brazil; coll. G. Muricy; 06/XII/1986; colour in vivo: white), UFRJPOR 3126 (paratype; Ponta do Anequim, Arraial do Cabo, Rio de Janeiro, Brazil; coll. E. Hajdu; 26/XII/1988; depth: 12 m; colour in vivo: white), and UFRJPOR 5089 (paratype; Ponta do Anequim, Arraial do Cabo, Rio de Janeiro, Brazil; coll. E. Hajdu; 26/XII/1988; depth: 12 m; colour in vivo: white).

Type locality: Arraial do Cabo, Rio de Janeiro, Brazil.

Additional analysed material: UFRJPOR 5055 (Gruta Azul, Arraial do Cabo, Rio de Janeiro, Brazil; coll. N. Boury-Esnault; 13/VI/1987; colour in vivo: white), UFRJPOR 5061 (Gruta Azul, Arraial do Cabo, Rio de Janeiro, Brazil; coll. N. Boury-Esnault; 13/VI/1987; colour in vivo: white), UFRJPOR 5092 (Enseadinha, Ilha de Cabo Frio, Arraial do Cabo, Rio de Janeiro, Brazil; coll. E. Hajdu; 07/III/1988; colour in vivo: white), and UFRJPOR 5117 (Racha de Nossa Senhora, Arraial do Cabo, Rio de Janeiro, Brazil; coll. E. Hajdu; 17/III/1988; colour in vivo: white).

Description: Colour in both alive and preserved specimens is white. The cormus is lobate and covered by a thin membrane ( Figure 12 A). Below this membrane there is a mesh of tightly anastomosed tubes. The surface is smooth. Oscula are numerous and surrounded by the same membrane that covers the cormus. The atrial cavity is wide and covered by a membrane. The holotype measures 3 x 1 cm (base x height), but there are some other fragments together with the largest one. It is attached to the calcareous algae Jania ungulata and J. adhaerens .

Skeleton composed of triactines, tetractines, and microdiactines. All these spicule types can be found in any region of the sponge, but they vary in abundance. Microdiactines are extremely rare. They were found protruding from the cortex ( Figure 12 B), inserted in the tubes, and also in some atrial sections. In the cortical skeleton, the triactines are the most abundant spicules ( Figure 12 C). This category is also the main component of the skeleton of the tubes, although tetractines are also present, pointing their apical actines into the lumen ( Figure 12 D). In the atrium, both triactines and tetractines are present, and none of them appear to be more abundant ( Figure 12 E). Small triactines and tetractines can be found all along the sponge body. These spicules were considered as juveniles, but as they were abundant, measurements were taken ( Table 8).

Spicules/ Specimens Actine Length (µm) Width (µm) N

Min Mean SD Max Min Mean SD Max

Triactine

UFRJPOR 5252 (H) 80.6 90.1 4.3 98.8 7.8 8.8 0.7 10.4 30

UFRJPOR 3126 (P) 80.6 93.5 7.3 109.2 7.8 8.2 0.6 9.1 30

UFRJPOR 5089 (P) 78.0 90.6 6.1 109.2 7.8 8.0 0.6 10.4 30

All specimens 79.7 91.4 5.9 105.7 7.8 8.3 0.6 10.0 –

Juvenile triactine

UFRJPOR 5252 (H) 26.0 43.8 8.2 57.2 5.2 7.7 0.6 9.1 30

UFRJPOR 3126 (P) 23.4 40.1 9.2 59.8 5.2 7.2 0.8 7.8 30

UFRJPOR 5089 (P) 31.2 48.5 7.5 59.8 6.5 7.7 0.4 7.8 30

All specimens 26.9 44.1 8.3 58.9 5.6 7.5 0.6 8.2 –

Tetractine Basal

UFRJPOR 5252 (H) 78.0 89.4 5.9 98.8 7.8 8.3 0.6 9.1 30

UFRJPOR 3126 (P) 83.2 92.2 4.9 104.0 7.8 7.9 0.4 9.1 30

UFRJPOR 5089 (P) 78.0 87.3 4.4 96.2 7.8 7.8 0.0 7.8 30

All specimens 79.7 89.6 5.1 99.7 7.8 8.0 0.3 8.7 –

Apical

UFRJPOR 5252 (H) 31.2 46.5 7.0 57.2 2.6 4.2 0.7 5.2 30

UFRJPOR 3126 (P) 33.8 47.1 9.5 78.0 2.6 4.2 0.6 5.2 30

UFRJPOR 5089 (P) 33.8 45.3 6.0 59.8 3.9 3.9 0.2 5.2 30

All specimens 32.9 46.3 7.5 65.0 3.0 4.1 0.5 5.2 –

Juvenile tetractine

UFRJPOR 5252 (H) Basal 39.0 55.4 9.1 80.6 7.8 7.8 0.2 9.1 30

UFRJPOR 3126 (P) 31.2 50.4 9.2 70.2 5.2 7.7 0.9 9.1 30

UFRJPOR 5089 (P) 28.6 54.2 10.4 70.2 5.2 7.2 0.8 7.8 30

All specimens 32.9 53.3 9.6 73.7 6.1 7.6 0.6 8.7 – Spicules ( Table 8):

(i) Triactines ( Figure 12 F): Regular. Actines are cylindrical to slightly conical, straight, with blunt tips;

(ii) Tetractines ( Figure 13 A): Regular. They are similar to the triactines, but have an apical actine which is thinner and shorter than the basal ones. It is commonly curved near the tip and has small spines ( Figures 12 D, 13B);

(iii) Microdiactine ( Figure 12 B): Only fragments were found. They were jagged or smooth. The tips could not be observed.

Remarks: Leucascus albus sp. nov. is the only species of the genus Leucascus with microdiactines in its skeleton. It is the second species of the genus Leucascus described to the Brazilian coast (the first one was L. roseus ). The main differences between these species is the colour alive, which is pink in L. roseus and white in L. albus sp. nov., the surface of the tubes, which is hispidate in L. albus sp. nov. and smooth in L. roseus , and the atrial skeleton, which is composed mainly of tetractines in L. roseus and of the same proportion of triactines and tetractines in L. albus sp. nov.

In the past, specimens from Arraial do Cabo were erroneously identified as L. simplex (Muricy et al. 1991) . In fact, L. albus sp. nov. differs from L. simplex in several characters, such as the presence of a membrane surrounding the oscula, microdiactines, and skeleton with more abundant tetractines.

Distribution: South-West Atlantic Ocean. Arraial do Cabo, Rio de Janeiro, Brazil. Spalding et al. (2007) corresponding ecoregion: Southeastern Brazil.

Figures

FIGURE 12. Leucascus albus sp. nov (UFRJPOR 5252, holotype). A, Preserved specimen; B, Jagged microdiactine in the sponge surface (arrow); C, Cortical membrane; D, Apical actines with curved tips (in detail; arrow) projected into the lumen of a choanocyte tube; E, Atrial membrane; F, Triactine.

FIGURE 13. Leucascus albus sp. nov (UFRJPOR 5252, holotype). A, Tetractine; B, Apical actine of a tetractine with spines (SEM).