Arturia vansoesti Condor-Lujan, Louzada, Hajdu & Klautau 2018, sp. nov.

Arturia vansoesti Cóndor-Luján, Louzada, Hajdu & Klautau, 2018

Synonyms. Arthuria sp. nov.: Pérez et al. 2017: 13. Arturia vansoesti sp. nov.: Cóndor-Luján et al. 2018: 0 7.

Material examined. (Two specimens) UFRJPOR 7425 and UFRJPOR 7431, Pointe Burgos, Anses d'Arlet, Martinique (1429.787' N–615.351' W), collected by M. Klautau & T. Pérez, 0 6 December 2013.

Material for comparison. Holotype (UFRJPOR 6720).

Colour. Yellow in life and beige to yellowish in ethanol.

Description. The analysed specimens have a delicate, soft but massive cormus formed by irregular and loosely anastomosed tubes (Figure 3A). The largest specimen (UFRJPOR 7425) measures 1.8 x 1.0 x 0.2 cm. In both specimens, water-collecting tubes were not observed (they were probably contracted). No granular cells were observed. Aquiferous system asconoid.

Skeleton. The skeleton is disorganised (Figure 3B) and composed of one category of triactines and one of rare tetractines.

Spicules (Table 3)

* From Condór-Luján et al. 2018 Triactine. Regular to subregular. Actines are cylindrical, slightly undulated at the distal part, with rounded tips (Figures 3 C–D). Actines with blunt tips were also found. The triactines are the most abundant spicules. Size: 65.0– 95.0/2.5–5.0 µm.

Tetractine. Regular. Basal actines are straight, cylindrical, with rounded to blunt tips (Figure 3E). The apical actine is the shortest actine. It is straight and smooth with sharp or blunt tips. Size: 65.0–95.0/2.5–5.0 µm (basal actine) and 32.5–52.5 µm (apical actine).

Ecology. The specimens were collected in habitats protected from light. Sediment was found on the surface of the cormus. A polychaete was found associated with UFRJPOR 7425.

Remarks. Arturia vansoesti is the second species of this genus to be known in the Caribbean Sea. As already discussed by Cóndor-Luján et al. (2018), the Atlantic species that most ressembles A. vansoesti is A. canariensis, however, A. canariensis is white alive, while A. vansoesti is yellow. Besides, A. canariensis has less cylindrical and less undulated spicules and they have blunt tips whilst in A. alcatraziensis tips are mostly rounded.

Arturia tubuloreticulosa Van Soest & De Voogd, 2015 from Indonesia is also morphologically similar to A. vansoesti, however, they can also be differentiated by their colour, orange in A. tubuloreticulosa and yellow in A. vansoesti, by the presence of water-collecting tubes in A. vansoesti and by the tips of the spicules, sharp or blunt in A. tubuloreticulosa and mostly rounded in A. vansoesti.

Geographical distribution. Curaçao (Cóndor-Luján et al. 2018) and Pointe Burgos, Anses d'Arlet, Martinique.