Arturia alcatraziensis (Lanna, Rossi, Cavalcanti, Hajdu & Klautau, 2007)

(Figure 2, Table 2)

Synonyms. Clathrina alcatraziensis: Lanna et al. 2007: 1556 . Arthuria hirsuta: Klautau et al. 2013: 458, Pérez et al. 2017: 13. Arturia hirsuta: Azevedo et al. 2017: 306 .

Material examined. (One specimen) UFRJPOR 7442, Pointe Burgos, Anses d'Arlet, Martinique (14°29.787' N – 61°5.351' W), collected by M. Klautau, 0 3 December 2013, 11 m depth.

Material for comparison. Holotype (MNRJ 5859) and samples from Cape Verde (ZMAPOR 0 7103 and ZMAPOR 07061).

Colour. White in life and in ethanol.

Description. The specimen has a massive globular shape (Figure 2A). The cormus is composed of regular and tightly anastomosed tubes with a central water-collecting tube. No cells with granules were found. Aquiferous system asconoid.

Skeleton. The skeleton is disorganised (Figure 2B) and composed of triactines, tetractines and diactines (Figures 2C–E). Diactines protrude through the surface, giving it a very hispid appearance.

Spicules (Table 2)

Triactine: Regular (equiangular and equiradiate). Actines are conical with blunt tips (Figure 2D). Size: 87.5– 125.0/10.0–12.5 µm. Sagittal triactines were also found.

Tetractine: Regular. Actines are conical with blunt tips (Figure 2E). Size: 82.5–137.5/10.0–12.5 µm. The apical actine is slender and smooth (Figure 2F). Size: 82.5–87.5/7.5 µm.

Diactines: Fusiform with one sharp tip and the other thicker and blunt (Figure 2C). Size: 227.5–860.0/10.0– 150.0 µm.

Ecology. The specimen was found in a crevice.

Remarks. Currently the genus Arturia is composed of 13 species. Among these species, Arturia hirsuta (Klautau & Valentine, 2003) is the most similar to A. alcatraziensis . In fact, the specimen from Martinique was previously identified as A. hirsuta (Pérez et al. 2017) . Although both species have some similarities, they differ mainly by the anastomosis of the cormus and shape of the diactines. In A. alcatraziensis, the cormus is spherical, the anastomosis is dense and regular, and the diactines are fusiform or have one tip almost arrow shaped, while in A. hirsuta, the cormus does not seem to be spherical (although the holotype is fragmented), the anastomosis is loose and irregular and the diactines are only fusiform (Klautau & Valentine 2003). Therefore, the specimen from Martinique matches the description of A. alcatraziensis . It has a spherical cormus composed of regular and tightly anastomosed tubes and its diactines vary from fusiform to arrow shaped. The only difference is in the size of the diactines, which is larger in the Martinique specimen (Table 2).

We compared our specimen from Martinique with another one from Cape Verde (ZMAPOR 07061) previously identified by Klautau et al. (2013) as A. hirsuta (see also Cóndor-Luján et al. 2018). Our specimen grouped with the specimen from Cape Verde with 100% bootstrap and presented 0% of p-distance (Figure 16), however, based on the cormus and shape of the diactines, we think that the specimen from Cape Verde was wrongly identified. Therefore, we correct here its identification to A. alcatraziensis and identify the specimen from Martinique as A. alcatraziensis as well. The ITS sequence published as A. hirsuta by Klautau et al. (2013) has then to be corrected to A. alcatraziensis .

Geographical distribution. Alcatrazes Archipelago—São Sebastião, São Paulo, Brazil (Lanna et al. 2007), Cape Verde (Klautau et al. 2013; Azevedo et al. 2017) and Martinique (Pérez et al. 2017).

*From Lanna et al. (2007). **From Klautau & Valentine (2003).