Discorhabdella ruetzleri, 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 : 232-234

Discorhabdella ruetzleri n. sp.

( Figure 2 )

Material collected: Holotype HBOM 003:02021 (sample 10 – V – 15 – 2 – 021). Type locality: Gulf of Mexico, north Pulley Ridge, 80 m deep, on a ledge. Mohawk ROV dive 149. Collected by John Reed. Coordinates: latitude 25 0 16.8990 N, longitude 83 0 37.7850 W.

Etymology: the species is named in honor of Dr. Klaus Rützler, our mentor and an important contributor to the knowledge of sponges from the Caribbean and world-wide.

External morphology: thinly encrusting (1–3 mm) with amorphous, bulgy protuberances ( Fig. 2A ). Surface prominently hispid microscopically. Orange reddish color alive; white in spirit.

Spicules: long principal tylostyles to subtylostyles with predominantly smooth tyles, and less abundant slightly tuberose tyles in a ratio of 7:1 ( Fig. 2B ); principal subtylostyles measure 470– 598 –810 x 5 –10.5–13 µm in length and width; small ectosomal substylostyles with smooth elongated tyles (260– 300 –340 x 3–4 –7.55 µm), sigmas (12–18 x <1 µm), pseudoastrose acanthostyles, with elongated terminal or apical spine, measuring 17 – 29.6 – 40 x 2.5 – 5 – 7.5 µm, with spiny heads 7.5 – 15 – 20 µm wide ( Fig. 2C, D ); some pseudoastrose acanthostyles with a smoothly elongated apical spine, others with spiny areas distal from the terminal end of the apical spine ( Fig. 2C, E ); several smaller smooth forms of the acanthostyles are considered early growth forms of this spicule category. Extremely thin microspined oxea (15–18 µm <1 µm) ( Fig. 2F ). Rare anchorate isochela (20–25 x 1.5 µm), not seen in the spicule preparations, but observed on a section of the skeleton.

Skeleton: The skeletal arrangement consists of a hymedesmoid arrangement of a single layer of large principal tylostyles to subtylostyles, which pierce the sponge surface. The tyles of the principal megascleres are embedded in a spongin layer that is also echinated by densely packed pseudoastrose acanthostyles; ectosomal smooth subtylostyles are around and between the principal choanosomal subtylostyles. Sigmas and microxea are abundant in the ectosome. Two isochelae observed in the choanosme in one transversal section.

Remarks: Pseudoastrose acanthostyles typical of genus, and with the apical spine described for D. hindei Boury-Esnault, Pansini & Uriz, 1992 and D. urizae Maldonado, Carmona, Van Soest, & Pomponi 2001 are abundant in this species ( Fig. 2C ). The species presents skeletal similarities to D. urizae and D. littoralis , the two species described from the eastern Pacific side of Panama. D. ruetzleri n. sp. is very similar in skeletal composition to D. urizae Maldonado et al. 2001 , a dark red thin crust originally collected on a boulder between 53 – 75 m deep in the Gulf of Chiriqui, off the Pacific coast of Panama, and later collected from the Gulf of California at 344 m ( Aguilar-Camacho et al. 2012). The main difference between D. ruetzleri n. sp. and D. urizae is the predominance of smooth tylostyles (both ectosomal and choanosomal) in D. ruetzleri n. sp. versus the predominant and strongly tuberose tyles of D. urizae principal choanosomal tylostyles. The species are futher distinguished by the thickness of the principal tylostyles and the considerably smaller microoxea in D. ruetzleri n. sp. ( Table 1). The discretely spined microxea of D. urizae and the shape and size of the pseudoastrose acanthostyles, with the spinose bulgy tyle and shortened spined base are very similar to D. ruetzleri n. sp., suggesting a potential common origin of these two species. D. littoralis Maldonado et al. 2001 from the eastern Pacific lacks isochela, while in D. ruetzleri n. sp. they are very rare but observed in one skeletal section. The smooth subtylostyles of D. littoralis share similarity with the subtylostyles of D. ruetzleri n. sp. The color in D. urizae is described as dark red, and D. littoralis is bright red orange, while for D. ruetzleri n. sp. the color is orange reddish that in spirit becomes completely white.

Figures

FIGURE 2. Discorhabdella ruetzleri n.sp. A. habitus (scale 1 cm), B. principal choanosomal subtylostyle with smooth tyle (scale 70 µm), C. pseudoastrose echinating acanthostyles with sub-terminal supination on apical spine, and sigma (scale 15µm), D. shorter choanosomal subtylostyles with smooth tyle (scale 100µm), E. pseudoastrose echinating acanthostyles with smooth apical spine (scale 10 µm), F. spined microrhabd (scale 10µm).