Hymedesmia (Hymedesmia) vaceleti, Díaz & Pomponi, 2018

Díaz, M. Cristina & Pomponi, Shirley A., 2018, New Poecilosclerida from mesophotic coral reefs and the deep-sea escarpment in the Pulley Ridge region, eastern Gulf of Mexico: Discorhabdella ruetzleri n. sp. (Crambeidae) and Hymedesmia (Hymedesmia) vaceleti n. sp. (Hymedesmiidae), Zootaxa 4466 (1), pp. 229-237 : 234

Hymedesmia (Hymedesmia) vaceleti n. sp.

( Figure 3 )

Material collected: Holotype HBOM 0 0 3:0 2020 (sample 19 – IX – 11 – 1 – 007).

Type locality: Gulf of Mexico, south of Pulley Ridge, 773 m deep, escarpment, on sediment. Collected by John Reed and Shirley Pomponi. Coordinates: latitude 24 0 39.600 N, longitude 83o55.0420 W.

Etymology: The species is named in honor of Dr. Jean Vacelet, our mentor and an important contributor to the knowledge of sponge systematics and ecology from the Mediterranean, the Indian Ocean and the Caribbean.

External morphology: Blue, with irregular whitish spots, thin crust (1 mm thick), forming small patches (1 – 4 cm 2), growing over snails, sides of solitary corals, and calcareous tubes ( Fig. 3A ). Surface smooth and shiny. Discretely microhispid microscopically.

Spicules: Large acanthostyles (280 –– 345 – 400 x 10 – 10.3 – 12.5 µm), with inflated head and large tuberculated spines (30 – 35 µm diameter) ( Fig. 3C ); smaller acanthostyles (100 – 137 – 150 x 7.5 – 9 – 10 µm) with spiny heads (12.5 – 15 µm in diameter) microspined all along ( Fig. 3D ); tornotes with stongyloid to styloid morphology (370 – 461 – 540 x 7.5 – 8 – 10 µm) ( Fig. 3B ); abundant arcuate isochela 45 – 60 µm long, and a thick flattened shaft 5 – 10 µm thick ( Fig. 3E – F ).

Skeleton: An hymedesmioid arrangement of large and small acanthostyles, that stand singly erect on a strong spongin basal layer, and tornotes that are strewn in the choanosome and in the ectosome ( Fig. 3C ).

Remarks: The combination of an intense blue color, large tornotes (> 400 µm in length), and the size of the acanthostyles differentiate H. (H.) vaceleti n.sp. from other Hymedesmia spp. from the western Atlantic ( Table 2). The closest species among the previously described Hymedesmia ( Table 2) is H. (H.) nummota De Laubenfels 1936 , a thin pale gray crust (0.5 – 2 mm thick), with an irregularly lumpy surface growing on a piece of dead coral, collected in deep water (1047 m) off the coast of Florida (between Dry Tortugas and Cuba). The other seven species of Hymedesmia currently described from the western Atlantic have considerably smaller and thinner tornotes (<255 µm in length, and <4 µm in width). The three categories of megascleres in H. (H). nummota differ in size ranges from those in H. (H.) vaceleti n. sp. The size of the two types of acanthotylostyles of H. (H.) nummota are triple the length of those in H. (H.) vaceleti n. sp., while the tornote strongyloids of H. (H.)vaceleti n. sp. can be 100 µm smaller than those in H. (H.) nummota . The size range of tornotes is very conserved and a significant character that distinguishes the different species of Hymedesmia from the western Atlantic ( Van Soest, 2009). Therefore, taking into account the tremendous disparity in the size of acanthotylostyles and the distinct blue color of H. (H.) vaceleti , we consider these differences sufficient evidence to classify the Pulley Ridge specimen as a different species from H.(H.) nummota .

Figures

FIGURE 3. Hymedesmia (Hymedesmia) vaceleti n.sp. A. habitus, thinly encrusting on Lophelia rubble and snails (scale 1 cm), B. ectosomal smooth tornote (scale 40 µm), C. hymedesmoid arrangement of megascleres observed in fragment that had been previously treated with nitric acid for spicule dissociation (scale 100 µm), D. smaller category of acanthostyles (scale 37.5 µm), E. arcuate isochela, side view (scale 22 µm), F. arcuate isochela, back view showing flattened shaft (scale 27.5µm).