Tosapusia isaoi, (KURODA & SAKURAI, 1959)

TOSAPUSIA ISAOI (KURODA & SAKURAI, 1959) View in CoL

FIGURE 6A, B View Figure 6

Mitropifex isaoi Kuroda & Sakurai View in CoL , in Kuroda, 1959: 324 – 326, fig. 1.

Type data

Holotype: NSMN-H323, 50.0 mm, off Tosa , Kochi prefecture, Shikoku, Japan, il in Higo, Callomon & Goto (2001).

Paratypes: NSMT-Mo 76260, including one, 50.0 mm, illustrated by Hasegawa & Saito (1995).

Material examined

Papua New Guinea: PAPUA NIUGINI, station CP3985, 05 ° 09 0 S, 147 ° 02 0 E, 805 – 865 m, 2 lv (MNHN IM-2013-40636, 43.4 mm, Fig. 6A View Figure 6 ; MNHN IM-2013- 19746, 30.0 mm) GoogleMaps ; PAPUA NIUGINI, station CP4009, 06 ° 04 0 S, 148 ° 12 0 E, 550 – 575 m, 1 lv (MNHN IM-2013- 19926, 41.9 mm) GoogleMaps .

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Philippines Sea : AURORA 2007, CP2709, 15 ° 12 0 N, 121 ° 34 0 E, 244 – 296 m, 1 lv (MNHN IM-2007-34557, 57.1 mm, Fig. 6B View Figure 6 ) GoogleMaps .

Diagnosis

Shell medium sized, attaining 57.1 mm, elongate fusiform (w / h 0.28 – 0.31; a / h 0.44), with stout, moderately long, siphonal canal and high spire. Protoconch unknown because of errosion. Suture distinctly canaliculated, giving spire a stepped, telescopic appearance. Teleoconch whorls slightly convex, subcylindric in profile, sometimes with indistinct shoul- der. Sculpture of dense and low, rounded, axial ribs, intersected by feeble spiral cords. Aperture elongate, with outer lip drawn towards tip of siphonal canal. Inner lip with four strong columellar folds. Shell colour tan, with lighter spiral bands on last adult whorl.

Anatomy

External morphology ( Fig. 7A View Figure 7 ): Body pale yellowish, lacking pigmentation, operculum absent. Siphon simple, moderately long, notably protruding beyond the edge of mantle. Mantle cavity rather long, spanning around one whorl; mantle thin with mantle cavity organs clearly visible. Head bearing rather long eye tentacles with small distinct eyes situated at their bases. Ctenidium very long, narrow, spanning throughout the posterior two-thirds of the mantle cavity. Osphradium large, exceeding half of ctenidium length. Anal gland present, indistinctly seen through the mantle as a narrow dark strip.

Anterior alimentary canal: Proboscis white, in contracted state occupying about two-thirds of rhynchocoel length. Anterior rhynchodaeum thick, pigmented violet. Paired retractors attached ventrolaterally to anterior rhynchodaeum ( Fig. 7B View Figure 7 ). Buccal tube very thin walled, strongly convoluted, connecting mouth with buccal mass. Buccal mass very long, occupying basal two-thirds of proboscis, with odontophore notably retracted backwards inside radular diverticulum ( Fig. 7C View Figure 7 ). Posterior to buccal mass, oesophagus forming broad loop followed by distinct bulbous valve of Leiblein. Salivary glands large, white, bulky, fused together without visible boundary. Salivary ducts adjoining the oesophagus loop anterior to valve of Leiblein. Accessory salivary glands (not shown in figure) distinct, translucent, situated ventrally, anterior to circum-oesophageal nerve ring. Mid-oesophagus just posterior to circum-oesophageal nerve ring, widened to form a glandular compartment. Posterior oesophagus adjoined by very large brown bulky gland of Leiblein that covers oesophagus dorsally.

Radula : MNHN IM-2013-40636 ( Fig. 7D View Figure 7 ) and MNHN IM-2007-34557 ( Fig. 7E View Figure 7 ), about 1.2 mm long and 0.23 mm wide, consisting of about 65 rows. Rachidian tricuspidate with relatively wide base (about one-third of radular width) and short blunt cusps, situated on short and flat projection of the rachidian medial portion. Laterals unicuspidate, triangular, massive in appearance, with drawn pointed cusp.

Male reproductive system: Male with long penis, slightly flattened on the sides ( Fig. 7A View Figure 7 ), without distinct papilla. Open seminal groove running along the inner edge of penis throughout its length, from base to tip.

Distribution and habitat

Japan, Philippines, Papua New Guinea (Bismarck Sea and Solomon Sea), Western Australia (off Port Hedland) (present material; M. Marrow pers. commun.); depth range 296 – 805 m.

Remarks

Tosapusia isaoi is characterized by a strongly canaliculated suture combined with only slightly convex teleoconch whorls that give the spire a distinctive telescopic outline, and a comparatively faint axial sculpture, distinguishing it from congeners.

Our specimens show some variation in shell morphology: the specimen from the Philippines (by far the largest) has notably coarser sculpture, slightly more convex whorls, and liration inside the outer lip. This may represent geographical variation or be attributed to gerontic condition. Molecular data confirm its conspecificity with specimens from Papua New Guinea.