Aglaona rudmani, Chaban & Ekimova & Schepetov & Chernyshev, 2022

Chaban, Elena M., Ekimova, Irina A., Schepetov, Dimitry M. & Chernyshev, Alexei V., 2022, The new genus Aglaona: the first abyssal aglajid (Heterobranchia: Cephalaspidea: Aglajidae) with a description of two new species from the north-western Pacific Ocean, Zoological Journal of the Linnean Society 196, pp. 198-214 : 206

AGLAONA RUDMANI SP. NOV.

( FIGS 1 , 4 )

Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: B4F1A566-0EBE-4A3E-A1CA-E8C5B773316E

Type specimens: Holotype, ZIN 62465, Sea of Okhotsk , Kuril Basin, SokhoBio expedition, R / V Akademik M.A. Lavrentyev, Cruise 71, station 11–6, 1 August 2015, 45˚35.3΄N 146˚24.7΄E, depth 3206 m (sequenced) . Paratypes: The same station as the holotype; two dissected specimens, ZIN 62699 (sequenced) and ZIN 62700 (sequenced) .

Type locality: Sea of Okhotsk , Kuril Basin, 45˚35.3΄N 146˚24.7΄E, depth 3206 m .

Diagnosis: Headshield with angulated posterior edge; apex with two whorls visible; spiral sculpture with chains of narrow, elongated pits of unequal height. Head copulatory system with penial papilla armed with a large, chitinous, denticulate stylet.

Description: Preserved holotype up to 5.1 mm long, c. twice as long as wide. Body white, almost completely retracted into shell. Headshield short, rounded anteriorly and angulated posteriorly, c. one-fifth of body length. Parapodia small; foot short, extending to half of shell length. Parapodia and foot strongly contracted.

Shell internal, white, semitransparent, occupying entire posterior shield, 4.8 mm in length and 3.3 mm in width. Shell oval, wider anteriorly; apex truncated, covered with callus; two whorls visible. Periphery of body whorl regularly oval. Aperture pear-shaped, upper margin slightly protruding beyond apex. Outer lip thin, fragile. Parietal wall convex, covered with a wide wing-shaped callus; columellar border of inner lip straight, covered with narrow callus. Growth lines weak, frequent; spiral sculpture consists of thin, frequent chains of shallow, narrow, elongated pits of unequal height connected with narrow grooves.

Buccal bulb muscular, with chitin lining inside and developed radular sac posteriorly; salivary glands short. Radular formula 16 × 2:1:0:1:2. Laterals large, hook-shaped, bearing small denticles on internal border; marginal small, hook-shaped, without denticles. Cephalic penial complex with large, elongated, penial sheath and a short, thick, convoluted prostate; prostate longer than penis. Penis armed with large, slightly curved, chitinous stylet; its ventral end bears c. six small denticles.

Distribution: Sea of Okhotsk, Kuril Basin, depth 3206 m.

Etymology: This species is named for Dr William (Bill) B. Rudman for his contributions to the study of heterobranch molluscs.

Figures

Figure 1. Map illustrating the collection sites of deepsea aglajids in the Sea of Okhotsk and Bussol Strait of the Kuril Islands.

Figure 4. Aglaona rudmani gen. & sp. nov. dorsal view of the holotype (A); ventral view of a paratype (B); paratype shell, ventral view, SEM the ‘wing-like’ callus is marked with an arrow (C); shell apex, SEM (E); shell spiral sculpture, SEM (D); radula, SEM (F); lateral teeth (G); copulatory system (SEM) (H); sketch, dissected penial sheath (I); chitinous stylet of penis SEM (J). Abbreviations: ej, ejaculatory duct opening; f, foot; pr, penial prostate; sh, headshield; psh, penial sheath; st, penial stylet. Scale bars: 2 mm (C), 1 mm (A, B), 500 µm (H), 400 µm (E), 200 µm (D), 100 µm (F, J), 50 µm (G).