Aglaona valdesi, 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 : 206-208

AGLAONA VALDESI SP. NOV.

( FIGS 1 , 5 )

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: 076EBBFA-C017-46B1-8C19-505F60E9CAE3

Type specimens: Holotype: ZIN 62696, Kuril Islands , Pacific slope of the Kuril Islands near the Bussol Strait, SokhoBio expedition, R / V Akademik M.A. Lavrentyev, Cruise 71, station 9–7, 26 July 2015, 46˚16.2΄N 152˚03.1΄E, depth 3374 m (sequenced) . Paratypes: ZIN 62463, SokhoBio, station 9–7, one specimen (dissected, sequenced) ; ZIN 42464, SokhoBio, station 9–7, one specimen (sequenced) ; ZIN 62697, SokhoBio, station 9–7, two specimens ; ZIN 62698, SokhoBio, station 9–9, 27 July 2015, 46˚15.7΄N 152˚03.1΄E, depth 3580 m, one specimen .

Type locality: Kuril Islands, Pacific slope of the Kuril Islands near the Bussol Strait, 46˚16.2΄N 152˚03.1΄E, depth 3374 m.

Diagnosis: Headshield truncated at its posterior end; apex with one whorl visible; spiral sculpture with chains of narrow elongated pits of equal height. Head copulatory system with large conical penial papilla armed with a small triangular chitinous plate.

Description: Preserved specimens up to 5.3 mm long, c. twice as long as wide. Body white, almost completely retracted into shell. Headshield short, rectangular, rounded anteriorly and truncated posteriorly, c. onefifth 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 mm long and c. 3 mm wide in the largest paratype. Spire consisting of a body whorl, covered with callus. Shell oval, wider anteriorly, widest in the middle of body whorl, apex obtuse. Periphery of body whorl regularly oval. Aperture not 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 equal height connected with narrow grooves.

Buccal bulb muscular, with chitin lining inside and developed radular sac posteriorly; salivary glands short. Radular formula 13 × 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 almost equal in length with penial sheath; penis consisting of large, conical papilla and small, triangular chitinous plate.

Comparison: Aglaona valdesi differs from A. rudmani in the head shape (truncated at its posterior end in A. valdesi vs. triangular in A. rudmani ) and penial armature (a microscopic triangular plate in A. valdesi vs. a large stylet with additional cusps in A. rudmani ) ( Table 4 ).

Distribution: Kuril Islands, Pacific slope of the Kuril Islands near the Bussol Strait, at 3374 m depth.

Etymology: This species is named for Dr Ángel Valdés for his contributions to malacology in general and to cephalaspidean research in particular.

Figures

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

Figure 5. Aglaona valdesi gen. & sp. nov. dorsal view of the paratype (A); ventral view of a paratype (B); ventral view of paratype shell, SEM: the ‘wing-like’ callus is marked with an arrow (C); shell spiral sculpture (D); shell apex, SEM (E); buccal bulb, frontal view, SEM (F); anterior part of digestive system, lateral view (G); jaw elements, enlarged SEM (H); radula, SEM (I); cephalic copulatory system, photo (J); penial papilla, SEM (K); sketch, penial sheath dissected (L). Abbreviations: c, parietal callus; es, oesophagus; f, foot; pl, chitinous plate at the end of the penial papilla; pp, penial papilla; pr, penial prostate; psh, penial sheath; rad, radular sac; sgl, salivary gland; sh, headshield. Scale bars: 1 mm (A, B, C, G), 500 µm (E, J), 200 µm (D, F), 50 µm (I, K), 10 µm (H).