Scaphander mundus Watson, 1883

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 674-676

Scaphander mundus Watson, 1883

Figs 40B, 42, 43

Scaphander mundus Watson, 1883: 342-343 .

Synonym:

Scaphander alatus Dall, 1895: 676 , pl. 27, fig. 2.

TYPE MATERIAL. — S. mundus : 2 syntypes BMNH 1887.2.9.2181-2181a . — S. alatus : holotype USNM 107161 (not examined) .

TYPE LOCALITY. — S. mundus : west of Papua, off Aore (= Aru) Islands, Indonesia, 15°41’S, 134°4.30’E, 1460 m [Challenger: stn 19] . — S. alatus : Hawaii , 545 m.

FIG. 42. Shell morphology and anatomy of Scaphander mundus Watson, 1883 . A, large shell,(23 mm), ventral view, New Caledonia, BIOGEOCAL stn CP 336; B, same shell,posterior view; C, (22 mm),ventral view, New Caledonia,BIOCAL stn CP 05; D, juvenile shell,(17 mm),ventral view, Fiji, BORDAU 1 stn CP 1458; E, gizzard plates, New Caledonia, BIOGEOCAL stn CP 336, scale bar = 2 mm; F, same specimen, radula, scale bar = 200 Μm.

MATERIAL EXAMINED. — Philippines. ESTASE 2: stn CP 4, 1920-2040 m, 1 dd, 1 lv; stn CP 317, 20°48’S, 166°53’E, 1620- 06°08’N, 125°58’E, 2800 m, 3 dd . — MUSORSTOM 2: stn CP 1630 m, 8 dd, 1 lv; stn CP 327, 21°12’S, 166°44’E, 2290 m, 1 dd 69, 14°05’N, 120°02’E, 1800 m, 1 dd. ( LACM 153245 ); stn CP 329, 21°09’S, 166°40’E, 2310-2315 m ,

Indonesia. The type material of S. mundus . 3 dd; stn CP 336, 21°12’S, 166°22’E, 2370-2380 m, 1 dd (Figs Coral Sea. MUSORSTOM 5: stn 323, 21°19’S, 157°58’E, 970 m, 40B, 42A, B, E, F); stn CP 341, 21°30’S, 166°47’E, 2334 m, 1 dd, 2 dd. 2 lv.

Loyalty Ridge. BIOCAL: stn CP 05, 21°16’S, 166°44’E, 2340 m, Vanuatu. MUSORSTOM 8: stn CP 1109, 14°52’S, 167°18’E, 2 dd & 1 lv (Fig. 42C); stn CP 23, 22°46’S, 166°20’E, 2040 m, 2 1550-1620 m, 1 lv.

lv; stn CP 72, 22°10’S, 167°33’E, 2100-2110 m, 1 lv; stn KG 96, Fiji. MUSORSTOM 10: stn CP 1354, SE of Viti Levu , 17°43’S, 21°23’S, 166°30’E, 2377 m, 1 dd . — BIOGEOCAL: stn CP 260, 178°55’E, 959-963 m, 2 dd; stn CP 1361, 18°00’S, 178°54’E, 21°00’S, 166°58’E, 1820-1980 m, 5 dd; stn CP 272, 21°00’S, 1058-1091 m, 12 dd. — BORDAU 1 : stn CP 1458, 17°22’S, 166°57’E, 1615-1710 m, 5 dd, 1 lv; stn CP 273, 21°02’S, 166°57’E, 179°28’W, 1216-1226 m, 2 dd (Fig. 42D) .

DISTRIBUTION. — Originally described from New Guinea, in 1460 m (Watson 1883). Subsequently reported from Hawaii, in 545 m (Dall 1895). Material herein collected from several localities in the Coral Sea, Fiji, Indonesia, New Caledonia, the Philippines and Vanuatu (Fig. 43), in 963-2800 m, live in 1620-2340 m.

DESCRIPTION. — Shell morphology. Length 29 mm, width 12 mm (largest specimen examined). Shell fragile, oval, with convex sides (Fig. 42A). Location of the widest region of the shell varies among specimens. In larger shells (c. 25 mm or longer) it is near the posterior end (Figs 42A), whereas in smaller shells (c. 25 mm or shorter) it is near the centre (Figs 42C) or the anterior end (Fig. 42D). Only 1 whorl visible, forming nearly the entire shell. Apex variable, rounded, slightly depressed, not umbilicate (Fig. 42B), with the aperture lip rising from the left side, forming a wing. The wing is wider in larger specimens (Fig. 42A), shorter and narrower in smaller specimens (Figs 38C, D). Anterior end of the shell rounded. Aperture as long as the shell, wider anteriorly and narrowing abruptly near the middle of the shell in larger specimens, and more gradually in smaller specimens. Columellar margin thickened, more conspicuously in smaller specimens, with no callus. Sculpture of a number of punctuated spiral grooves. The punctuations are small, oval, almost rectangular, and situated next to each other within each groove. The grooves are separated by gaps narrower than the grooves themselves, and occasionally narrower grooves are intercalated. Colour uniform snowy white.

Anatomy. The digestive system contains 3 smooth gizzard plates, of which 2 are large and oval, whereas the third is elongate (Fig. 42E). The radular formula is 18 x 1.0. 1 in a specimen from New Caledonia (BIOGEOCAL stn CP 336). The lateral teeth are short and hook-shaped, with a strong, short, curved cusp (Fig. 42F).

The reproductive system is monaulic (Fig. 40B). The ampulla is long and convoluted. It connects to the long and wide post-ampullary duct. The seminal receptacle enters the long post-ampullary duct, which continues distally to the common general atrium. Another duct leads from the base of the seminal receptacle and enters the female glands. The bursa copulatrix also enters the common atrium. From the gonopore an open seminal groove runs anteriorly to the protrusible cephalic penis and the prostate. The prostate is oval to elongate.

REMARKS. — Watson (1883) described Scaphander mundus based on several shells collected from off Aru Island (= Arrou Island), west of New Guinea in 1460 m. The shells were described as thin, ivory-white, with small spiral punctuations. Later, Dall (1895) described Scaphander alatus from Hawaii (545 m depth) as a pure white shell with fine spiral rows of punctuations. Examination of the syntypes of S. mundus and the original description of S. alatus revealed that these species are indistinguishable and therefore they are here regarded as synonyms.

The material here examined from the Coral Sea, Fiji, Indonesia, New Caledonia, the Philippines and Vanuatu is also similar to the type material of S. mundus and is referred to this species.

Scaphander mundus is distinct from S. japonicus (A. Adams, 1862) in shell morphology and anatomy. The shells of S. mundus are larger, whitish and more oval than those of the latter species, which are more conical and pigmented. Anatomically the central gizzard plate of S. mundus is narrower and longer that that of S. japonicus and the radula has wider and much shorter teeth. Additionally, the reproductive system of S. mundus is very different from that of S. japonicus , having a much shorter and wider prostate.