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

LEUCILLA ANTILLANA View in CoL SP. NOV.

( FIGS 13 View Figure 13 , 14 View Figure 14 ; TABLE 11)

Etymology: From its presence in Curaçao, which is an island of the Leeward Antilles.

Type locality: Water Factory , Willemstadt, Curaçao .

Material examined: Holotype. UFRJPOR 6768, Water Factory , Willemstadt, Curaçao (12°06′30.88″N, 68°57′13.53″W), 9.9 m depth, coll. B. Cóndor-Luján, 23 August 2011. GoogleMaps

Diagnosis: Leucilla with a skeleton composed of cortical tetractines, subatrial triactines and atrial tetractines, and leuconoid aquiferous system.

Colour: White to light blue in life ( Fig. 13A View Figure 13 ) and white in ethanol ( Fig. 13B View Figure 13 ).

Morphology and anatomy: This species has an irregular tubular shape being wider at the base ( Fig. 13A View Figure 13 ). It measures 1.0 × 0.8 × 0.2 cm. The surface is slightly hispid due to some protruding spicules. The osculum is apical and has a delicate crown of trichoxeas (arrow in Fig. 13B View Figure 13 ). The aquiferous system is leuconoid with subspherical to elongated choanocyte chambers ranging from 97.2 to 162.0 µm of diameter.

Skeleton: The skeleton is characteristic of the genus ( Fig. 13C View Figure 13 ). The cortical skeleton is exclusively formed by tetractines ( Fig. 13D View Figure 13 ) with the basal actines tangentially positioned on the surface. The choanosomal skeleton is inarticulated, composed of the apical actine of the cortical tetractines ( Fig. 13E View Figure 13 , arrow), which occasionally crosses the atrial skeleton, and of the unpaired actine of the subatrial triactines ( Fig. 13F View Figure 13 , white arrow). The subatrial triactines do not form a continuous layer, instead, they are irregularly scattered in this region. The atrial skeleton is composed of tetractines with the apical actine projected into the atrium ( Fig. 13F View Figure 13 , black arrow).

Spicules: Cortical tetractines. Sagittal. Actines are conical with sharp tips. The paired actines are frequently curved. The apical actine is straight and it is the longest actine ( Fig. 14A View Figure 1 View Figure 2 View Figure 3 View Figure 4 ). Some undulated apical actines were also observed. Size: 350.0–485.0/35.0–60.0 µm (paired actine), 75.0–200.0/35.0–60.0 µm (unpaired actine) and 285.0–550.0/35.0–55.0 µm (apical actine). Subatrial triactines. Sagittal. Actines are conical with sharp tips. The paired actines are straight and smaller than the unpaired one ( Fig. 14B, C View Figure 14 ). Some slightly curved paired actines were also observed. Highly variable size: 175.0–460.0/15.0–60.0 µm (paired actine) and 225.0–490.0/15.0–55.0 µm (unpaired actine). Atrial tetractines. Sagittal. Actines are conical with very sharp tips. The unpaired actine is slightly longer than the paired ones ( Fig. 14D View Figure 14 ). The apical actine is the thinnest and shortest actine. Size: 120.0–270.0/10.0– 12.5 µm (paired actine), 185.0–355.0/10.0–12.5 µm (unpaired actine) and 15.0–50.0/5.0–10.0 µm (apical actine).

Ecology: This species was found underneath coral boulders at 9.9 m depth. No organisms were found associated with this species.

Molecular analysis: We provide the first C-LSU sequence of a Leucilla species, L. antillana sp. nov. In both phylogenetic reconstructions (ML and BI), Leucilla was not recovered as a monophyletic genus as the two Leucilla species used in this study, L. antillana sp. nov. and L. micropilosa sp. nov. (see below), appeared in different clades ( Fig. 15 View Figure 15 ).

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

Taxonomic remarks: The species that most resemble L. antillana sp. nov. are L. amphora (type locality: Puerto Rico or Barbados, Haeckel did not specify this), L. capsula Haeckel, 1872 (type locality: Agulhas Bank, South Africa), L. uter Poléjaeff, 1883 (type locality: Bermudas or Philippines, Poléjaeff did not specify this) and L. sacculata Carter, 1890 (type locality: Fernando de Noronha Archipelago, Brazil).

Leucilla antillana sp. nov. can be easily differentiated from L. amphora and L. capsula because the skeleton of the two latter species ( L. amphora and L. capsula ) is exclusively composed of tetractines (as described and illustrated by Haeckel, 1872), whereas the new species has subatrial triactines.

Different to L. sacculata and L. uter , the skeletons of which comprise cortical microdiactines and subatrial tetractines (these latter can be found scattered in the choanosome of those species), L. antillana sp. nov. does not have any microdiactines nor subatrial tetractines in its skeleton. Considering the spicule dimensions of the other spicule categories of L. sacculata and L. uter provided in their original descriptions, the size ranges do not match the new species. Leucilla antillana sp. nov. has thinner spicules (15.0–60.0 µm) compared to L. sacculata (84.7 µm). The apical actine of the cortical tetractines of L. uter is almost twice as long (400.0–1200.0 µm) as that of L. antillana sp. nov. (285.0–550.0 µm) and the atrial tetractines are thicker (20.0 µm vs. 10.0–12.5 µm).

Leucilla antillana sp. nov. is the second species of the genus Leucilla recorded from Curaçao. Leucilla amphora was also reported from that island by Arndt (1927). That author mentioned that Breitfuss was responsible for the identification and did not give a description of the samples. Therefore, as we did not analyse those specimens, we can neither confirm nor invalidate that record.