Pagodula concepcionensis, Houart, Roland & Sellanes, Javier, 2006

Houart, Roland & Sellanes, Javier, 2006, New data on recently described Chilean trophonines (Gastropoda: Muricidae), description of a new species and notes of their occurrence at a cold seep site, Zootaxa 1222, pp. 53-68 : 59-61

Pagodula concepcionensis new species

( Figs 15–19 , 34–35 )

Type material

Holotype (MNHNCL­201648) (19mm); paratype ( IRSNB IG 30559/565) R/V AGOR Vidal Gormáz, off Concepción, Chile, (Sta. AGT 1, 11/30/2003), 36°21.46’S, 73°44.08’W, 930m, lv (19.5mm).

Type locality

East Pacific Ocean, south­central Chile, R/V AGOR Vidal Gormáz, (Sta. AGT 6 10/ 11/2004), northwest of the Bay of Concepción, 36°21.75’S, 73°43.55’W, 726–865m, dd.

Description

Shell up to 19.5 mm in length at maturity (paratype), slender, weakly spinose, lightly built, strongly shouldered. Spire high with 1.5 protoconch whorls and up to 5.5 convex, strongly shouldered teleoconch whorls. Suture impressed. Protoconch broad, rounded; terminal lip eroded.

Axial sculpture of teleoconch whorls consisting of low, narrow, weakly lamellose varices. First whorl with eroded varices, second with 11–13 varices, third with 10–12, fourth and last with 10–13. Spiral sculpture of weak, narrow, smooth, primary and secondary cords. First and second whorls partly eroded, third and fourth with P1–P3 visible. Last whorl with P1, s1, P2, (s2), P3, P4, P5. P1 broadest, P2, P3, P4 weakly narrower, all three of same strength, P5 low, shallow, s1 shallow, s2 only weakly apparent in holotype. Spiral cords more obvious on varices. Short, broad, open spinelets present where spiral cords cross varices; more obvious on P1.

Aperture small, roundly­ovate; columellar lip narrow, smooth, rim completely adherent; anal notch shallow, broad; outer lip thin, smooth. Siphonal canal long, about 32% of total shell length, broadly open, straight, smooth, except terminations of previous canals as low axial lamellae.

Shell white. Operculum elliptical with terminal nucleus, light brown.

Radula with rachidian bearing long, broad, central cusp; single short narrow denticle, weakly pressed against to long, very broad, lateral cusp. Lateral teeth sickle­shaped, broad.

Remarks

Pagodula concepcionensis n.sp. resembles T. veronicae Pastorino, 1999 from southern Chile and other subantarctic localities ( Figs 22–24 ). However, P. concepcionensis differs in having a comparatively smaller shell, with the spiral cords closer to each other on the last teleoconch whorl, and chiefly, in having a different protoconch morphology, denoting a lecithotrophic larval development, probably of intracapsular nature, having a large, broad, irregularly shaped protoconch of 1.5 whorls, compared to the multispiral, smooth, conical protoconch of T. veronicae , consisting of 3 whorls, probably indicating a planktotrophic larval development.

Pagodula concepcionensis n.sp. also superficially resembles T. coulmanensis E. A. Smith, 1907 from the Kerguelen Islands, but P. concepcionensis is comparatively smaller, possesses more numerous axial lamellae on the last teleoconch whorl (9–11 vs. 7 or 8) and is spirally ornamented with narrow cords compared to the smooth shell of T. coulmanensis .

Pagodula concepcionensis also bears a general resemblance to the Western Atlantic Pagodula aculeata (Watson, 1882) , having an almost identical morphology of the teleoconch whorls. However, both species differ in having distinct protoconch morphology. The protoconch of P. concepcionensis is almost twice as broad, more flattened and irregularly shaped, while P. aculeata has a small, glossy, more conical protoconch ( Fig. 25 ). The radula of P. concepcionensis differs slightly from P. aculeata ( Fig. 37 ) in having broader and shorter lateral cusps, and in having the lateral denticle weakly pressed against the lateral cusp. In P. a c u l e a t a the denticle is more distant from the lateral cusp while being broader and longer than in P. concepcionensis . However these differences may also be due to intraspecific variation or sexual dimorphism in P. concepcionensis .

Finally, P. concepcionensis differs from Pagodula verrillii Bush, 1893, another West Atlantic species, in being comparatively larger, in having apparent spiral cords compared to the smooth shell of P. verrillii, and in having a flatter, irregularly shaped protoconch compared to the high, rounded and smooth protoconch of P. verrillii ( Fig . 26).

Another specimen that may be referable to T. concepcionensis is discussed below under Pagodula cf. concepcionensis .

Biotope

Both specimens so far known have been collected within an area where methane is escaping from the seafloor. This area is characterized by the presence of massive blocks of authigenic carbonates, which provide a hard substrate for the fauna. The sediment, in which carbonate blocks lay, is typically a sticky dark grey mud, sometimes with sulphidic smell.

Etymology

Named after the type locality, 40 miles NW off the Bay of Concepción.

Discussion

Pagodula concepcionensis is similar to other species of Pagodula in having a high spired shell and shouldered teleoconch whorls, with low axial lamellae or lamellate ribs, usually ending as short, or long, spine like, shoulder projections; the spiral sculpture on abapical teleoconch whorls consists of shallow, occasionally obvious, but rarely obsolete or absent cords. These spiral cords never cross the axial lamellae like in Trophonopsis species. The siphonal canal is usually long, always spineless and broadly open ( Houart 2001). Pagodula differs from Trophon s.s. in having a relatively narrower shell with a comparatively smaller aperture and a longer siphonal canal. It also differs in having a radula with a detached (free) lateral denticle, not attached to the interior margin of the lateral cusp as in Trophon s.s. ( Pastorino 2005).

Pagodula is also known from the Mediterranean, from the western and eastern Atlantic, and from the Indo­West Pacific.

Figures

FIGURES 15 – 26. 15 – 19, Pagodula concepcionensis n. sp.; 15 – 16, Chile, off Concepción, 36 ° 21.75 ’ S, 73 ° 43.55 ’ W, 726 – 865 m, holotype MNHNCL­ 201648, 19 mm; 17 – 18, Chile, off Concepción, 36 ° 21.46 ’ S, 73 ° 44.08 ’ W, 930 m, paratype IRSNB IG 30559 / 565, 19.5 mm; 19, Protoconch (holotype) Scale bar 0.5 mm; 20 – 21, Pagodula cf. concepcionensis; Chile, off Concepción, 36 ° 21.46 ’ S, 73 ° 44.08 ’ W, 930 m, RH, 21.13 mm; 22 – 24, Trophon veronicae Pastorino, 1999, off southern Chile, 46 ° 00 ’ S, 83 ° 59 ’ W, 742 m, holotype USNM 880195, 52.2 mm (photo courtesy G. Pastorino). Scale bar: 200 µm; 25, Protoconch of Pagodula aculeata (Watson, 1882) (RH). Scale bar: 0.5 mm; 26, Protoconch of P. verrillii (Bush, 1893) (RH). Scale bar: 0.5 mm.

FIGURES 27 – 35. 27 – 29, Coronium wilhelmense (Ramírez­Bohme, 1981); 27 – 28, Chile, off Valdivia, 39 ° 50 ’ S, 74 ° 30 ’ W, 500 m, JS, 18.4 mm; 29, Protoconch. Scale bar: 0.5 mm; 30, Protoconch of Trophon acanthodes (Watson, 1882) [syntype BM (NH)] 1887.2. 9.570. Scale bar: 0.5 mm; 31 – 32, Trophon vangoethemi; 31, Operculum, Chile, off Concepción, 36 º 10.50 ’ S, 73 º 35.95 ’ W, 563 – 613 m (scale bar: 1.2 mm); 32, Radula, male, same locality (scale bar: 60 µm); 33, Radula of Trophon condei, female, off Concepción, Chile, (Sta. AGT 1, 11 / 30 / 2003), 36 ° 21.46 ’ S, 73 ° 44.08 ’ W, 930 m, (scale bar: 120 µm); 34 – 35, Radula of Pagodula concepcionensis n. sp., female, off Concepción, Chile, (Sta. AGT 1, 11 / 30 / 2003), 36 ° 21.46 ’ S, 73 ° 44.08 ’ W, 930 m, (scale bar: 60 µm).

FIGURES 36 – 37. 36, Radula of Boreotrophon cepula (Sowerby, 1880), Kuriles Islands (scale bar: 10 µm); 37, Radula of Pagodula aculeata (Watson, 1883), Brazil (scale bar: 10 µm).