Scaphander interruptus Dall, 1890b

Siegwald, Justine & Malaquias, Manuel António E., 2025, Bringing light into deep-sea biodiversity: a systematic revision and molecular phylogeny of the genus Scaphander Montfort, 1810 (Gastropoda: Cephalaspidea), with a focus on the Indo-Pacific, Zoological Journal of the Linnean Society 203, pp. 1-60 : 18-21

Scaphander interruptus Dall, 1890b

( Figs 6−8 ; Table 2)

Scaphander interruptus Dall, 1890b: 297 , pl. 12, fig. 12; Pilsbry 1893: 250–251, pl. 31, fig. 26; Kobelt 1896: 9–10, pl. 7, fig. 12; Dall 1908: 239; Finet 1991: 273; Gosliner 1991: 302; Finet et al. 2011: 119; Valdés and McLean 2015 (in part): 119–120, figs 1, 6–8; Valdés 2019: 276–277, fig. 18A, B.

Scaphander cf. otagoensis 2— Siegwald et al. 2022.

Taxonomic history: Dall (1890b, 1908) described S. interruptus based on shells collected offshore of Chile and the Galapagos during the Albatross expedition and remarked on their resemblance to the European species S. lignarius . Valdés and McLean (2015) redescribed the species based on samples available at the LACM from the Northeastern Pacific (between Oregon and Chile), including anatomical data. However, examination of the material used in that paper revealed that the specimens used were a mix of species and that the specimens dissected present a visible spire and rounder shells and belong to the species S. grandis , also occurring in the Northeastern Pacific (see S. grandis section). The anatomy of S. interruptus presented here is therefore based on novel material.

Type material: Scaphander interruptus Dall, 1890b — Chile: west coast of Chile , Albatross Expedition , station 2788, 45°35'00"S, 75°55'00"W, 1920 m, three syntypes, USNM97075 , H = 33 mm, images seen ( Fig. 6A ) .

Other material examined: Chile: Laguna San Rafael National Park, one sh., SCBUCN-2206, H = 14.3 mm; west of Chiloé Island, one spc., dissected, ZMBN 127896, H = 22.7 mm; three sh., ZMBN 127897, H = 14.5–16.3 mm; south of Concepción, one spc., dissected and sequenced, SCBUCN-2837, H = 41.7 mm; west of Concepción, one spc., ZMBN 127898, H = 17.1 mm. Peru: west of Isla Lobos de Tierra, one sh., LACM 1974-18.4, H = 14 mm. Panama: off Azuero Peninsula, west of Punta Mala, one sh., MCZ 27921, H = 11 mm, images seen. Costa Rica: southwest of Punta Guiones, one sh., LACM 1973-109.5, H = 22 mm. Australia: Bass Strait, one spc., dissected and sequenced, AM C.590961, H = 23 mm; Victoria, East Gippsland Commonwealth Marine Reserve, one spc., dissected and sequenced, AM C.563068, H = 20 mm. New Zealand: Tasman Sea, 400 km west of the North Island, two sh. and 13 spcs, one sequenced, NIWA 30427, H = 10–18 mm.

Diagnosis: Shell pyramidal to elongate, covered by thick brown to thin dirty white periostracum. Spiral sculpture composed of ovoid punctations, mostly distinct but can be interconnected. Spire concealed. Posterior edge of outer lip rising slightly above apex. Rachidian teeth sub-rectangular. Prostate short, club-shaped. Penial papilla absent. Penial chamber lined with soft longitudinal ridges.

Shell ( Fig. 6 ): Maximum H observed = 41.7 mm. Shell pyramidal to elongate, only one whorl visible. Aperture as long as shell, narrowing posteriorly. Spire concealed. Posterior edge of outer lip rounded, rising slightly above apex. Parietal wall covered with thick, smooth white callus, thinner in juvenile forms. Spiral sculpture composed of punctuated striations, alternating wider and narrower rows. Punctations ovoid or rectangular, distinct or interconnected. Periostracum transparent to pale yellow or light brown. Shell dirty white.

Radula ( Fig.7A–C ): Radular formula 21 × 1.1.1 (H = 41.7 mm). Lateral teeth curved, with weak denticulation on inner edge. Rachidian teeth sub-rectangular, cusps slightly curved inward.

Digestive tract ( Fig. 7D, E ): Salivary glands short, thin, surface uneven. Gizzard plates kidney-shaped to sub-triangular.

Male reproductive system ( Fig. 7F, G ): Penial chamber cylindrical, lined with soft longitudinal ridges. Muscular papilla absent. Penial chamber separated from prostate by prostatic duct. Prostate short, club-shaped.

Ecology: Found between 497 and 2760 m depth ( Dall 1890b, 1908; present study). Feeds on foraminifera (present study).

Distribution ( Fig. 8 ): Southern Pacific, from Chile to Costa Rica ( Dall 1890b, Valdés and McLean 2015; present study), Southern Australia to Northwestern New Zealand (present study).

Remarks: Scaphander interruptus is, with S. grandis and Scaphander willetti Dall, 1919 , one of the only three known Scaphander species in the Eastern Pacific. However, the distribution ranges of the two species do not seem to overlap, with S. willetti known only from Southern Alaska, S. grandis known to occupy the Northern Pacific downwards to California, and S. interruptus present in southern latitudes between Chile and Costa Rica. Furthermore, the presence of a visible spire in S. grandis makes it unmistakable with S. interruptus .

Our study revealed the presence of S. interruptus in the Tasman Sea, between Southeastern Australia and New Zealand. Scaphander interruptus can be differentiated from congenerics S. otagoensis and Scaphander amygdalus that also inhabit Trans-Tasman waters by its narrower, more elongate shell shape, a translucent periostracum rather than cream or yellow-brown in colour, in addition to a parietal callus significantly less marked than in the other two species. The rachidian teeth in S. interruptus have straighter edges that do not bend outwards at the upper cusps as in S. otagoensis and lack the acute corners and wider shape of the rachidian in S. amygdalus . The male reproductive system in S. interruptus is also distinct, because no warts line the deeper part of the penial chamber (see S. otagoensis and S. amygdalus sections). Furthermore, the three species are genetically distinct, with high uncorrected p -distances for COI between them: 10.14%–11.76% between S. interruptus and S. amygdalus , 9.01%–10.03% between S. interruptus and S. otagoensis , and 11.91%–13.39% between S. otagoensis and S. amygdalus (Supporting Information, Table S2).

Figures

Figure 6. Shells and SEM images of the shell sculpture of Scaphander interroptos. A, Chile, west coast (syntype, UNSM 97075, H = 33 mm; image adapted from Valdés and McLean 2015). B, Chile, south of Concepción (SCBUCN-2837, H = 41.7 mm). C, Costa Rica (Pacific side), southwest of Punta Guiones (LACM 1973-109.5, H = 22 mm). D, Chile, west of Chiloé Island (ZMBN 127896, H = 22.7 mm). E, Australia, Bass Strait (AM C.590961, H = 23 mm). F, Australia, Victoria, East Gippsland Commonwealth Marine Reserve (AM C.563068, H = 20 mm). G, Chile, south of Concepción (SCBUCN-2837, H = 41.7 mm). H, I, Australia, Victoria, East Gippsland Commonwealth Marine Reserve (AM C.563068, H = 20 mm). J, Costa Rica (Pacific side), southwest of Punta Guiones (LACM 1973-109.5, H = 22 mm). Scale bars: I, J = 200 µm.

Figure 7. Anatomical details of Scaphander interroptos, Chile, south of Concepción (SCBUCN-2837, H = 41.7 mm).A, radula. B, rachidian teeth. C, detail of lateral teeth.D, anterior part of digestive tract. E, gizzard plates. F, male reproductive system. G, lining of penial chamber. Scale bars:A, G = 200 µm; B, C = 20 µm; D, F = 1 mm; E = 2 mm.

Figure 8. Geographical distribution of Scaphander amygdalus, Scaphander interroptos, and Scaphander otagoensis. Geographical records are based on studied material and reliable literature records.