Gymnobela frielei ( Verrill, 1885 )

Criscione, Francesco & Hallan, Anders, 2024, Integrative taxonomy of Gymnobela and Pontiothauma (Conoidea: Raphitomidae) from Australian waters provides more evidence of transoceanic distribution in deep-sea gastropods, Journal of Natural History 58 (37 - 40), pp. 1429-1459 : 1450-1451

Gymnobela frielei ( Verrill, 1885) (PSH G4)

( Figures 4 A-F, 6E)

Pleurotomella frielei Verrill, 1885 – Verrill 1885, p. 413, pl. 44, fig. 5

Pleurotoma polysarca Dautzenberg and Fischer, 1896 – Dautzenberg and Fischer 1896: 422, pl. 17, figs 11–12

Bela polysarca var. minor , ventricosa, major Locard, 1897 – Locard 1897: 246

Material examined

Australia, New South Wales, Jervis CMR (− 35.333°S, 151.258°E), IN2017_ V03 _056, 2650– 2636 m, 1 wet ( AMS C.482314), 1 wet ( AMS C.571677), 1 wet ( AMS C.571702), 1 wet ( AMS C.571666), 1 wet ( AMS C.571812) .

Distribution

South Atlantic Ocean (off Cape Region), Tasman Sea (off NSW south coast) .

Remarks

The shell attributed to G. frielei by Bouchet and Warén (1980, fig. 124) exhibits a markedly less convex spire than that of the holotype. We are therefore uncertain as to whether this shell is conspecific with the holotype of G. frielei ( Figure 4A ). The material examined herein also possesses the convex spire characteristic of the holotype ( Figure 4A–F ). The radula figured for this species by Bouchet and Warén (1980, fig. 27) appears quite distinct from the Gymnobela radulae examined by us ( Figure 6A–E ). The source specimen is not available for examination, so we cannot assess the shell from which it was extracted. The radula figured there appears to have a distinct barb, and there is no evidence of a ventral blade; in contrast, their depiction of the radula of G. engonia in that same study (fig. 26) is consistent with our understanding of the genus, in that it exhibits no distinct barb, but a prominent ventral blade. All we can say in this regard is that the radula provided there attributed to G. frielei possibly represents additional characters in Gymnobela radulae, or that it indeed belongs to another, yet to be determined genus. The shell of this species is similar to that of G. glaucocreas , known only from the shell of its holotype ( Figure 4G ), which differs in being more elevated and possessing more numerous ribs.

Internal and external anatomy is here observed for the first time and described as follows: animal (based on AMS C.482314) pale blue (in life, then fading to white); cephalic tentacles medium long, thick, cylindrical, eyes very small; penis large, rather long, coiling clockwise, blunt tip except for small distal papilla-like appendage; proboscis club-shaped; venom gland moderately large, coiled; muscular bulb elongated, pearlescent. Radula (based on AMS C.571702) of relatively straight, tightly rolled hypodermic teeth attaining approximately 100 µm in length; no distinct ventral barb; ventral blade distinctly elevated, approximately 1/5 of length of tooth, somewhat sagittate in appearance in some teeth; adapical opening elongated, about 1/7 of length of tooth; base wide, angular, with distinct but shallow lateral process; exterior texture somewhat coarse; basal opening large, subcircular. Ligament rather long, broad.

The transoceanic distribution inferred here for this species follows the same rationale as that of G. engonia (see Remarks herein for that species).

Figures

Figure 4. Shells of Gymnobela primary species hypotheses (PSHs)/species studied herein. (A) G. frielei (Verril, 1885), holotype Smithsonian National Museum of Natural History (USNM) 44653; (B) G4/ G. frielei Australian Museum (AMS) C.571666; (C) G4/G. frielei AMS C.571702; (D) G4/G. frielei AMS C.482314; (E) G4/G. frielei AMS C.571812; (F) G4/G. frielei AMS C.571677;(G) G4/G. glaucocreas (Barnard, 1963), holotype Iziko South African Museum (ISAM) A9821; (H) G3/G. angulosa Sysoev, 1988, holotype Zoological Museum of Moscow University (ZMMU) Lc-22363 (I) G3/G. angulosa AMS C.571649; (J) G3/ G. angulosa AMS C.571648; (K) G3/G. angulosa, Bavarian State Collection of Zoology (ZSM) mol 20070770. Scale bar = 10 mm.

Figure 6. Hypodermic teeth of primary species hypotheses (PSHs)/species studied herein. (A) G1/ Gymnobela agassizi (Verrill and Smith, 1880), Australian Museum (AMS) C.519355; (B) G2/Gymnobela engonia, AMS C.482287; (C) G3/Gymnobela angulosa Sysoev, 1988, Bavarian State Collection of Zoology (ZSM) mol 20070770; (D) G3/Gymnobela angulosa Sysoev, 1988 AMS C.571648; (E) G4/ Gymnobela frielei (Barnard, 1963) AMS C.482314; (F) P1/Pontiothauma sp. AMS C.482298; (G) P2/ Pontiothauma transregna sp. n. paratype AMS C.519398. Scale bar: A–E = 50 µm; F–G = 100 µm.