Leucilla micropilosa, Cóndor-Luján & Louzada & Hajdu & Klautau, 2018

LEUCILLA MICROPILOSA View in CoL SP. NOV.

( FIGS 16 View Figure 16 , 17 View Figure 17 ; TABLE 12)

Etymology: From the Latin pilosus (=hairy), for the presence of microdiactines crossing the cortex.

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

Material examined: Holotype. UFRJPOR 6755, Tug Boat , Caracasbaai, Willemstadt, Curaçao (1 2°0 4′ 0 8.2 0″N, 6 8°5 1′4 4.4 0″W), 8.6 m depth, coll. B. Cóndor-Luján, 23 August 2011 . Paratypes. UFRJPOR 6739, Sunset Waters , Soto, Curaçao (12°16′01.58″N, 69°07′44.85″W), 13.1 m depth, coll. B. Cóndor-Luján, 22 August 2011 GoogleMaps . UFRJPOR 6756, Tug Boat , Caracasbaai, Willemstadt, Curaçao (12°04′08.20″N, 68°51′44.40″W), 8.6 m depth, coll. B. Cóndor-Luján, 23 August 2011 GoogleMaps .

Diagnosis: Leucilla with a skeleton composed of cortical microdiactines, triactines and tetractines, subatrial triactines and atrial tetractines. The mean width of the cortical triactines varies from 12.0 to 14.4 µm. The mean length of the apical actine of the atrial tetractines varies from 49.7 to 78.8 µm. The aquiferous system is sylleibid.

Colour: White to light blue in life ( Fig. 16A–C View Figure 16 ) and white in ethanol ( Fig. 16D–F View Figure 16 ). Transparent and bright.

Morphology and anatomy: This sponge has a variable external morphology ( Fig. 16A–F View Figure 16 ), which can be tubular ( Fig. 16A, D View Figure 16 ) to flattened sac-shaped ( Fig. 16C, F View Figure 16 ) but always with an apical osculum. The surface is smooth, although (thin) microdiactines protrude through the surface. The consistency is rough. The holotype (UFRJPOR 6755) measures 1.2 × 0.5 × 0.2 cm. The osculum has a margin sustained by T-shaped triactines and it is surrounded by short trichoxeas. The aquiferous system is sylleibid ( Fig. 16G View Figure 16 ) with subspherical to elongated choanocyte chambers ranging from 62.2/54.1 to 135.1/81.1 µm. The aquiferous system is sylleibid.

Skeleton: The skeleton is typical of the genus ( Fig.16G View Figure 16 ). The cortical skeleton is composed of microdiactines perpendicularly positioned on the surface ( Fig. 16H View Figure 16 ) or organized in tufts (only in UFRJPOR 6739, Fig. 16I View Figure 16 ), triactines and the basal actines of the tetractines. The triactines are distributed tangentially to the surface ( Fig. 16J View Figure 16 , arrow). The choanosomal skeleton is inarticulated, composed of the apical actines of the cortical tetractines and by rare subatrial triactines. The apical actine of the tetractines crosses the choanosome and occasionally reaches the atrium ( Fig. 16J, K View Figure 16 , white arrows). The unpaired actine of the subatrial triactines points toward the cortex ( Fig. 16K View Figure 16 , black arrow). The atrial skeleton is exclusively composed of tetractines with their apical actine protruding into the atrial cavity ( Fig. 16K View Figure 16 , asterisk).

Spicules: Microdiactines. Straight with sharp tips. Size: 27.0–94.5/1.1–1.4 µm. Cortical triactines. Sagittal. Actines are smooth, conical, with sharp tips ( Fig. 17A View Figure 17 ). Sometimes the paired actines are curved. Size: 102.6–310.5/8.1–18.9 µm (paired actine), 89.1– 310.5/6.7–18.9 µm (unpaired actine). Subcortical tetractin es. Sagittal. Actines are straight, smooth, conical, with sharp tips ( Fig. 17B View Figure 17 ). The apical actine is very large. These are the largest spicules in this species. Size: 172.8–572.4/21.6–64.8 µm (paired actine), 183.6–540.0/30.0–64.8 µm (unpaired actine), 162.0–1036.8/21.6–64.8 µm (apical actine). Subatrial triactines. Sagittal.Actines are conical, smooth, straight, with sharp tips ( Fig. 17C View Figure 17 ). The paired actines are shorter than the unpaired one and some are slightly curved. Sometimes, one paired actine is longer than the other. Size: 81.0–240.3/8.1–21.6 µm (paired actine), 91.8– 610/8.1–18.9 µm (unpaired actine). Atrial tetractines. Sagittal. Actines are conical, straight, smooth and have sharp tips. The unpaired actine is slightly longer than the paired ones ( Fig. 17D View Figure 17 ). The apical actine is the shortest actine. Size: 100.0–264.6/10.0–24.3 µm (paired actine), 83.7–297.0/10–21.6 µm (unpaired actine), 27.0–115.0/8.1–13.5 µm (apical).

Ecology: Specimens from Curaçao were found underneath broken coral boulders between 8 and 13 m depth. No associated organisms were found. Some balls of sediment were found inside the atrial cavity of one of the specimens (UFRJPOR 6739).

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

Molecular analysis: We provide the second DNA sequence for Leucilla , L. micropilosa sp. nov. In the C-LSU tree of Calcaronea ( Fig. 15 View Figure 15 ), none of the new Leucilla species, L. antillana sp. nov. or L. micropilosa sp. nov., clustered together with the other sequences of the Amphoriscidae family, namely, Paraleucilla dalmatica Klautau, ImeŠek, Azevedo, PleŠe, Nikolić & Ćetković, 2016 and P. magna Klautau, Monteiro & Borojevic, 2004 , supporting the non-monophyly of this family.

Taxonomic remarks: Although the sequence of L. micropilosa sp. nov. did not group with L. antillana sp. nov., we rather maintain this species as Leucilla following the current classification of the subclass Calcaronea ( Borojevic, Boury-Esnault & Vacelet, 2000), which is based on morphological characters. However, a revision of the calcaronean genera, including Leucilla , is urgent. The descriptions and sequences of L. antillana sp. nov. and L. micropilosa sp. nov. provided herein will certainly contribute to an integrated revision of this genus.

Leucilla View in CoL now comprises 15 valid species and among them, the species that resemble the most Leucilla micropilosa View in CoL sp. nov. are L. antillana View in CoL sp. nov. (described in the previous section) and L. amphora sensu Borojevic & Boury-Esnault (1987) View in CoL .

Leucilla micropilosa View in CoL sp. nov. can be easily distinguished from L. antillana View in CoL sp. nov. because the skeleton of the former has cortical triactines and microdiactines, whereas in the latter, those spicule categories are absent.

Leucilla amphora View in CoL was originally described by Haeckel (1872), who analysed specimens from Puerto Rico and Barbados. Haeckel (1872) characterized the skeleton of L. amphora View in CoL as being exclusively composed of tetractines. However, in the redescription of this species ( Borojevic & Boury-Esnault, 1987), based on the examination of several specimens from Dakar ( Senegal) and on Haeckel’s slides, they mentioned the presence of cortical and subatrial triactines as well as some microdiactines (‘microxeas’).

We compared L.micropilosa View in CoL sp. nov. with L.amphora sensu Borojevic & Boury-Esnault (1987) View in CoL as they have similar external morphology and skeletal composition but they have slightly different spicule size and aquiferous system. Regarding spicule dimensions, L. micropilosa View in CoL sp. nov. has thinner cortical triactines (holotype: paired actine = 14.4 ± 2.8 µm and unpaired actine = 14.1 ± 3.0 µm) and atrial tetractines with longer apical actines (holotype: 65.1 ± 11.4 µm) compared to L. amphora sensu Borojevic & BouryEsnault (1987) View in CoL (16.0–25.0 and 23.0–32.0 µm, respectively). In L. amphora sensu Borojevic & Boury-Esnault (1987) View in CoL , choanocyte chambers are positioned between the inhalant and exhalant system, whereas in L. micropilosa View in CoL sp. nov. it is not possible to observe this arrangement.