Leucandra caribea, Cóndor-Luján & Louzada & Hajdu & Klautau, 2018

Cóndor-Luján, Báslavi, Louzada, Taynara, Hajdu, Eduardo & Klautau, Michelle, 2018, Morphological and molecular taxonomy of calcareous sponges (Porifera: Calcarea) from Curaçao, Caribbean Sea, Zoological Journal of the Linnean Society 183 (3), pp. 459-525 : 493-497

LEUCANDRA CARIBEA SP. NOV.

( FIGS 18–20; TABLE 13)

Etymology: Named after its distribution in the Caribbean Sea.

Type locality: Tug Boat , Caracasbaai, Willemstadt, Curaçao .

Material examined: Holotype. UFRJPOR 6754, Tug Boat , Caracasbaai, Willemstadt, Curaçao ( 12°04′08.20″N, 68°51′44.40″W), 13.9 m depth, coll. B. Cóndor-Luján, 23 August 2011.

Diagnosis: Leucandra with a sac-shaped body and leuconoid aquiferous system. The skeleton is mostly formed by triactines with some tetractines lining the choanosomal canals and atrial cavity. The choanosomal skeleton is composed of one category of triactines. Cortical trichoxeas are also present.

Colour: White in life ( Fig. 18A) and beige in ethanol ( Fig. 18B).

Morphology and anatomy: This species has a sac-shaped external morphology: it is wide at the base and becomes narrower near the osculum ( Fig. 18A). It measures 0.7 × 0.3 × 0.1 cm ( Fig. 18B). This sponge is quite smooth and compressible. Near the suboscular region there are short trichoxeas protruding through the surface ( Fig. 18C). The osculum is apical. It is supported by triactines, tetractines and has a discrete crown of trichoxeas ( Fig. 18D, E). The aquiferous system is leuconoid with subspherical choanocyte chambers ranging from 28.0 to 34.0 µm in diameter ( Fig. 18F). The diameter of the exhalant canals varies from 140.0 to 300.0 µm.

Skeleton: The skeleton is typical of the genus ( Fig. 19A). As mentioned before, the oscular margin has a differentiated skeleton. It is composed of T-shaped triactines and tetractines tangentially positioned and short trichoxeas perpendicular to the surface. The cortical skeleton is composed of tangential triactines ( Fig. 19B). The choanosomal skeleton does not have any special organization and it is formed by triactines of variable sizes (as shown in Figs 18F, 19A). Several exhalant choanosomal canals were observed within this region. They are surrounded by tetractines with the apical actine projected inside them ( Fig. 19C). Some triactines lining the canals were also found ( Fig. 19D). No subatrial skeleton was observed. The atrial skeleton is formed by triactines ( Fig.19E) and rare tetractines ( Fig. 19F). The apical actine of the tetractines protrudes into the atrial cavity (arrow in Fig. 19F).

Spicules: Cortical triactines. Subregular or parasagittal. Actines are slightly conical with sharp tips. The paired actines are frequently curved and slightly longer than the unpaired one, which is always straight ( Fig. 20A). Size: 110.0–340.0/7.5– 16.3 µm (paired actine) and 105.0–325.0/7.5–16.3 µm (unpaired actine). Choanosomal triactines. Regular or subregular. Actines are conical with sharp tips ( Fig. 20B). They are the largest spicules in L. caribea sp. nov. Highly variable size: 370–960/25–75 µm. Triactines and tetractines of the canals. Sagittal. Actines are conical with sharp tips. The paired actines are curved, following the shape of the canals ( Fig. 20C, D). The apical actine of the tetractines is smooth and it is thinner than the basal actines (as shown in Fig. 19C). The size of the triactines is similar to that of the tetractines. Size of tetractines: 112.5–220/7.5– 12.5 µm (paired actine), 62.5–210.0/7.5–12.5 µm (unpaired actine) and 45.0–110.0/5.0–10 µm (apical actine). Atrial triactines (shown in Fig. 19E): Sagittal. Actines are conical with sharp tips. Compared to the cortical triactines, the atrial triactines are thinner and the angle formed by the paired actines is more open. Size: 132.3–253.8/8.1–13.5 µm (paired actine) and 164.7–253.8/5.4–13.5 µm (unpaired actine). Atrial tetractines. Sagittal. Actines are conical with sharp tips ( Fig. 20D). The apical actine is smooth. Size: 150.0–262.5/7.5–15.0 µm (paired actine), 162.0–297.0/8.1–16.2 µm (unpaired actine) and 35.0–132.5/7.5–12.5 µm (apical actine).

Ecology: This species was found underneath a coral boulder at 13.9 m depth. The basal region was attached to an algae (as shown in Fig. 18A, B).

Geographical distribution: Southern Caribbean (provisionally endemic to Curaçao, present study).

Taxonomic remarks: Among the species of Leucandra reported from the Caribbean Sea, namely L. crustacea ( Haeckel, 1872) , L. barbata ( Duchassaing & Michelotti, 1864) , L. curva ( Schuffner, 1877) , L. multiformis Poléjaeff, 1883 , L. rudifera Poléjaeff, 1883 , and L. typica ( Poléjaeff, 1883) ( Van Soest et al., 2017) , only L. typica possesses a similar skeletal composition as that of L. caribea sp. nov. The skeletons of the other Caribbean species include cortical tetractines ( L. crustacea and L. curva ), diactines ( L. barbata , L. multiformis and L. rudifera ) and atrial grapnel spicules (also in L. rudifera ), which are spicule categories absent in L. caribea sp. nov.

Leucandra caribea sp. nov. can be differentiated from L. typica as the former species possesses an atrial skeleton mainly composed of triactines and few tetractines, whereas in the latter species, triactines and tetractines are in the same proportion (or at least, Poléjaeff did not indicate the opposite). Besides, in the new species, the choanosomal canals are lined by tetractines and triactines and in L. typica they are only lined by tetractines. In L. typica , trichoxeas (<300.0/1.0 µm) are scattered in the choanosome and spindle-shaped microdiactines (100.0/4.0 µm) are concentrated in the suboscular region, while in L. caribea sp. nov., trichoxeas (>100.0/1.2 µm) were found only in the suboscular region.

Among the other species of Leucandra with skeletal composition and external morphology comparable to that of L. caribea sp. nov, L. falakra Klautau, ImeŠek, Azevedo, PleŠe, Nikolić & Ćetković, 2016 from the Adriactic Sea is the one that most resembles the new species. Nonetheless, they have some important differences. The choanosomal skeleton of the Curaçaoan species is composed of one single type of triactine (370.0–960.0/25.0–75.0 µm) while in the Adriatic species, it is composed of small (paired actine: 94.5–180.9/8.1–13.5 µm and unpaired actine: 70.0–143.1/8.1–16.2 µm) and giant triactines (342.0– 1047.6/48.6–118.8 µm). Additionally, although almost all the spicule categories have similar dimensions ( Table 13), the unpaired actine of the atrial tetractines is shorter in L. falakra (59.4–126.9 µm) than in the new species (162.0–297.0 µm).

GENUS LEUCANDRILLA BOROJEVIC, BOURY-ESNAULT & VACELET, 2000

Type species: Leucilla wasinensis Jenkin, 1908 .

Diagnosis: ‘ Grantiidae with leuconoid organization. In addition to triactines the cortex contains tetractines, with the apical actines turned into the choanoderm. The articulated choanoskeleton is supported by subatrial triactine spicules, and numerous rows of choanosomal triactines and/or tetractines, with apical actines of cortical tetractines in the distal region’ ( Borojevic et al., 2000).