Caecum dakuwaqa Pizzini, Raines & Vannozzi, 2013

Walter, Angelo Vannozzi & Renda, Walter, 2024, Sampling the depth: New data on the Caecidae (Mollusca, Gastropoda) from northeastern Papua New Guinea, Zoosystema 46 (14), pp. 327-347 : 336-338

Caecum dakuwaqa Pizzini, Raines & Vannozzi, 2013

( Fig. 6 A-E)

Caecum dakuwaqa Pizzini et al. 2013: 19 , fig. 10K-O.

TYPE MATERIAL. — Holotype. Fiji • sh; SE of Viti Levu ; 18°18.5’S, 178°05.8’E; MNHN-IM-2000-24843 .

Paratypes. Fiji • 8 sh; same data for holotype; MNHN-IM-2000-24844 • 2 sh; Bligh Water, MUSORSTOM 10 Stn DW1314; 17°16’9”N, 178°14’51”E; 656-670 m depth; 5.VIII.1988; MNHN-IM-2000-24847 • 8 sh; Bligh Water, MUSORSTOM 10 Stn DW1333; 16°50’21”N, 178°12’33”E; 200-215 m depth; 8.VIII.1988; MNHN-IM-2000-24848 • 2 sh; Bligh Water, MUSORSTOM 10 Stn DW1334; 16°51’22”N, 178°13’56”E; 251-257 m depth; 9.VIII.1988; MNHN-IM-2000-24849 • 3 sh; S Viti Levu , MUSORSTOM 10 Stn DW1365; 18°12’43”N, 178°32’22”E; 295- 302 m depth; 15.VIII.1988; MNHN-IM-2000-24850 • 1 sh; S Viti Levu , MUSORSTOM 10 Stn DW1376; 18°18’40”N, 178°9’4”E; 497-504 m depth; 17.VIII.1988; MNHN-IM-2000-24851 • 2 sh; S Viti Levu , MUSORSTOM 10 Stn DW1381; 18°17’46”N, 177°54’25”E; 275-430 m depth; 18.VIII.1988; MNHN-IM-2000-24852 • 2 sh; SE Viti Levu , MUSORSTOM 10 Stn CP1354; 17°42’36”N, 178°54’58”E; 959-963 m depth; 12.VIII.1988; MNHN-IM-2000-24853 • 4 sh; S Viti Levu , MUSORSTOM 10 Stn CP1363; 18°12’23”N, 178°33’0”E; 144-150 m depth; 15.VIII.1988; MNHN-IM-2000-24854 • 9 sh; S Viti Levu , MUSORSTOM 10 Stn CP1366; 18°12’21”N, 178°33’3”E; 149- 168 m depth; 15.VIII.1988; MNHN-IM-2000-24855 • 14 sh; S Viti Levu , MUSORSTOM 10 Stn CP1369; 18°11’7”N, 178°23’26”E; 392-433 m depth; 16.VIII.1988; MNHN-IM-2000-24856 .

Vanuatu • 1 sh; S-SE Santo , MUSORSTOM 8 Stn DW1072; 15°39’53”N, 167°19’36”E; 622-625 m depth; 4.X.1994; MNHN-IM-2000-24845 • 15 sh; E Santo , MUSORSTOM 8 Stn DW1105; 15°2’35”N, 167°7’29”E; 154-179 m depth; 7.X.1994; MNHN-IM-2000-24846 .

TYPE LOCALITY. — Pacific Ocean, Fiji, southeast of Viti Levu, 18°18.5’S, 178°05.8’E, 260-305 m depth.

MATERIAL EXAMINED. — Papua New Guinea • 1 sh; New Ireland; 2°44’S, 150°35’E; 240-305 m depth; 3.IX.2014; KAVIENG 2014 Stn DW4463; MNHN • 2 sh (1 juv); New Ireland; 2°45’S, 150°37’E; 163- 358 m depth; 3.IX.2014; KAVIENG 2014 Stn DW4470; MNHN .

DISTRIBUTION. — Northeastern PNG (new record), Vanuatu, Fiji ( Pizzini et al. 2013; Vannozzi 2019b).

DIAGNOSIS. — Shell small for the genus, colourless, transparent, with several brownish annular bands separated by three-four times as-wide interspaces. Protoconch unknown. Teleoconch tubular, slightly arched, dextrally twisted, with very fine rings. Early teleoconch conical. Adult shell slender, subcylindrical, flaring toward the aperture, then contracting and ending with a reflected lip. Septum almost flat without mucro, recessed below the cutting plane. Operculum and soft parts unknown. Adult shell length 1.8 mm.

REMARKS

This species is distinctive due to the subcylindrical twisted tube with bell-shaped aperture. The specimens recorded from PNG are very fresh and allowed to recognise the presence of a colour pattern in this species, never reported so far. In fact, this species is characterised by a colourless transparent shell with narrow brown annular bands separated by three or four times as-wide interspaces. Further knowledge on this species came from a juvenile specimen ( Fig. 6C, D ), showing a more twisted and more tapering tube. This species occurs in several IWP localities but was recorded always below 100 m depth, suggesting that its habitat occurs in the mesophotic-aphotic zone.

Figures

FIG. 6. — Caecum Fleming, 1813 species from deep-water stations from northeastern PNG: A-D, C. dakuwaqa Pizzini, Raines & Vannozzi, 2013 from Stn DW4470 (C, D: juvenile); E, C. dakuwaqa from Stn DW4463; F, C. cf. succineum from Stn DW4495; G, C. neocaledonicum de Folin, 1868 from Stn DW4470; H, C. neocaledonicum from Stn DW4464; I, C. frugi Vannozzi, 2019 from Stn DW4412; J, C. frugi juv. from Stn CP4418; K, C. neoguineanum Vannozzi, 2019 from Stn DW4495; L, C. sp. from Stn DW4465 MNHN-IM-2022-2399. Scale bars: A-H, K, L, 1 mm; I, J, 0.5 mm.