Hyalinothrix enoki, Mah & Fujita, 2020

Mah, Christopher L. & Fujita, Toshihiko, 2020, New species and occurrence records of Japanese Solasteridae and Ganeriidae including a new species of Paralophaster from the North Pacific with an overview of Hyalinothrix, Zootaxa 4750 (1), pp. 67-100 : 86-89

Hyalinothrix enoki n. sp.

Figure 6 A–D

Etymology: The species epithet, enoki refers to a specific type of Japanese mushroom which bears a similar appearance to the clavate paxillar spines observed in this species. Noun held in apposition.

Diagnosis. Hyalinothrix species distinguished by paxillae bearing non-glassine, spinelets with clavate or macelike tips.

Comments. This species possesses non-glassine, clavate shaped spinelets present on the abactinal and body surface, which makes it the most morphologically divergent of Hyalinothrix species relative to the type species, Hyalinothrix millespina as described by Fisher (1911), which possess glassine spinelets on its abactinal and other body surface paxillae.

Occurrence: Izu Islands, Japan, 160– 171 m.

Description. Body stellate (R/r=3.5–3.6), arms round in cross-section, interradial arcs acute ( Fig. 6A ).

Abactinal surface composed of cruciform-shaped basal plates each with four rounded imbricating lobes forming fenestrate network. Lobes short, each of four plates forming the boundary for papular region, each region most spread out proximally becoming more tightly arranged distally on arm.Abactinal plates arranged in distinctly linear, widely spaced rows along arms. Linear rows most complete along arm, becoming incomplete proximally along arm, more irregular on disk. Single papular pores regularly along body surface, larger proximally but becoming absent distally as those distalmost plates become most closely articulated. Each plate with cruciform-shaped base, tip with a tuft of blunt, non-glassine spines with clavate tips, four to 30, mostly five to 20 ( Fig. 6B ).

Superomarginal and inferomarginal series track from interradial region to arm terminus (sensu Blake 1978). Spinelets finger-like rather than clavate on abactinal plates. Marginal plates otherwise similar to abactinals, with cruciform base, papular pores absent between marginal rows.

Actinal plates present on disk and midway along arm, each with two to 20, mostly four to 10 blunt, finger-like (non-clavate) spines ( Fig. 6C, D ). Papular pores absent.

Adambulacral plates crescentic, with curve facing distally ( Fig. 6D ). Each plate with three to 10 blunt, fingerlike spines, mostly three to eight, present in pairs along each plate with two facing into the tube foot furrow. Each adambulacral plate separated by tissue from the next. Oral plates, each with 10 finger-like spines, totaling 20 per interradius. Papular pores absent from actinal field.

Color in life was white.

Material Examined. Holotype. NSMT E-7115A, Northeast of Hachijyo-jima Island , Izu Islands, Japan, R / V Shin’yo-maru St. 29, 33˚31.5′N, 140˚15.5′E–33˚31.3′N, 140˚15.4′E, 160–161 m, 23 October 2003, 1 wet spec., R =1.4 r=0.4.

Paratypes: Japan, NSMT-E-7115B, Northeast of Hachijyo-jima Island , Izu Islands, R / V Shin’yo-maru St. 29, 33˚31.5′N, 140˚15.5′E–33˚31.3′N, 140˚15.4′E, 160–161 m, 23 October 2003, 1 wet spec., R =0.6 r=0.2. NSMT E- 7149, Northeast of Hachijyo-jima Island , Izu Islands, R / V Shin’yo-maru St. 29, 33˚32.9′N, 140˚16.0′E–33˚32.8′N, 140˚15.9′E, 170–171 m, 23 October 2003, 1 wet spec., R =1.8 r=0.5.

Hyalinothrix sp. cf. gracilis Aziz & Jangoux, 1985

Figure 7 A–D

Comments. The specimen described herein appears in accord with the description of Hyalinothrix gracilis as outlined by Aziz & Jangoux (1985) differing in having a less stellate body form (R/r=4.75–5.0) versus R/r= 5.4 in in the holotype, having slightly more spinelets per paxilla (up to 50 versus 40 on the holotype), and the oral plates displaying 10 rather than seven to eight furrow spines. However, the current specimens were collected from the Izu Islands in Japanese waters at 160–168 meter depth versus the holotype which was apparently collected from Indonesian waters at 5684 meter depth. The collection depth is drastically different not only from these specimens but other known Hyalinothrix species, which are only known to occur in <300 m depths.

Hyalinothrix are not frequently encountered and explanations for these inconsistencies include the possible that this is simply a widely occurring species, a closely related cryptic species, or simply an error in reporting of the locality.

Occurrence. Izu Islands, Japan. 260– 268 m.

Description. Body strongly stellate (R/r=4.75–5.0), arms round in cross-section, interradial arcs acute ( Fig. 7A ).

Abactinal surface composed of well-developed cruciform plates with stout bases, forming fenestrate network ( Fig. 7B ). Lobes forming around a single papular pore, most spread out proximally becoming more tightly arranged distally on arm. Abactinal plates arranged in distinctly linear widely spaced rows. Linear rows most complete along arm. Each abactinal base with a tuft of fine spinelets with jagged, hyaline tips, four to 50, mostly 20 to 40. Single, or less abundantly, double papular pores regularly along body surface, larger proximally but becoming absent distally as those distalmost plates become most closely articulated.

Marginal plates similar if not identical to abactinals, but both superomarginal and inferomarginal series track from interradial region to arm terminus (sensu Blake 1978). Spinelets finger-like rather than clavate on abactinal plates.Marginal plates otherwise identical to abactinals, with cruciform basal outline, papular pores absent.

Actinal region very small. ( Fig. 7C ) Actinal plates present on disk and midway along arm, each with two to 20, mostly four to 10 blunt, finger-like (non-clavate) spines. Papular pores absent.

Adambulacral plates rectangular to weakly curved, with curve facing distally ( Fig. 7D ). Each plate with four to six, mostly four or five, fine, glassine furrow spines, with hyaline tips that are webbed in a weakly curved fan. Furrow spines separated from subambulacral spine cluster by a discrete open space, subambulacral area covered by 10–30, mostly 20–25 fine glassine spinelets each with one to three serrate tips ( Fig. 7D ). Each adambulacral plate separated by tissue from the next. Oral plates, each with 10 finger-like spines, totaling 20 per interradius.

Color in life was a dark orange/brown with light yellow to tan mottling on the abactinal side. Oral side was white to cream.

Material Examined. NSMT E-7101, Northeast of Hachijyojima Island , Izu Islands, Japan, 33˚31.2′N, 140˚16.6′E–33˚31.4′N, 140˚16.7′E, 166–168 m, Coll . R / V Shin’yo-maru, St. 28, 23 October 2003, 1 wet spec ., R =3.5 r=0.7; NSMT E-7147, Northeast of Hachijyojima Island , Izu Islands, Japan, 33˚31.5′N, 140˚15.5′E–33˚31.3′N, 140˚15.4′,161– 160 m, Coll . R / V Shin’yo-maru., St. 29, 23 October 2003, 1 wet spec ., R =3.8 r=0.8.

Figures

FIGURE 6. Hyalinothrix enoki n. sp. Holotype, NSMT E-7115A. A. Abactinal surface. Scale bar=0.5 cm. B. Close-up of abactinal surface. Scale bar=2.0 mm. C. Oral surface. Scale bar=0.5 cm. D. Close-up of oral and furrow region. Scale bar=0.5 cm.

FIGURE 7. Hyalinothrix gracilis NSMT E-7101. A. Abactinal surface. Scale bar=1.0 cm. B. Close-up of abactinal paxillae. Scale bar=2.0 mm. C. Oral surface. Scale bar=1.0 cm. D. Close-up of actinal intermediate area and tube foot region showing adambulacral plates and furrow spination. Scale bar=0.5 cm.