Novastoa rapaitiensis, Schiaparelli & Bieler & Golding & Rawlings & Collins, 2017

Schiaparelli, Stefano, Bieler, Rüdiger, Golding, Rosemary E., Rawlings, Timothy A. & Collins, Timothy M., 2017, A new species of Novastoa Finlay, 1926 (Mollusca: Gastropoda: Vermetidae) from coral reefs of the Pacific Ocean, European Journal of Taxonomy 323, pp. 1-11 : 3-7

Novastoa rapaitiensis sp. nov.

urn:lsid:zoobank.org:act:CDFD584C-298A-4360-ADAE-09F8220E49B0

Figs 1–3

Novastoa sp. – Golding et al., 2014: 8 (table 1), 14, fig. 6 (phylogram), 82, 90, fig. 353 (cross-sectional diagram of operculum).

Etymology

This species takes the name of its type locality, Rapa Iti Island ( French Polynesia), and is dedicated to all the people from Rapa Iti that we met during the MNHN Rapa 2002 Expedition, in recognition of their kindness and hospitality.

Material Examined

Holotype

FRENCH POLYNESIA: ♂ (1 complete body and shell fragments), RAPA 2002 Expedition , st. 2, Bass Islands , Rapa Iti, off Pointe Tematapu, 27°34.4′ S, 144°19.0′ W, 29 m, 2 Nov. 2002, S. Schiaparelli leg., 95% EtOH ( MNHN IM-2000-27249 ).

Paratypes

FRENCH POLYNESIA: 1 ♀? (1 anterior body, dissected for operculum and tissue clipping), same collection data as holotype, 95% EtOH (GenBank acc. nr. KC583404.1 (28S ribosomal RNA gene, partial sequence; 12S ribosomal RNA gene, partial sequence; tRNA-Val gene, complete sequence), nr. KC583373.1 (16S ribosomal RNA gene, partial sequence)) ( MNHN IM-2000-31684); 1 ♂, 2 ♀♀ (incomplete specimens with part of viscera missing, extracted from dead coral blocks), RAPA 2002 Expedition, st. 26, Bass Islands, Rapa Iti, Baie Anatakuri Nako, 27°38.394′ S, 144°18.851′ W, 3 m, 13 Nov. 2002, S. Schiaparelli leg., formalin fixed and transferred to 95% EtOH ( MNHN IM-2000-31685).

Additional material

FRENCH POLYNESIA: 1 specimen, Society Islands, Moorea Island, E of Cook’s Bay, 17°28.434′ S, 149°49.116′ W, 11 m, fore reef in groove and under rocks, 1 Nov. 2009, G. Paulay, T. Lotufo and S. McPherson leg., 75% EtOH ( UF 436684); 1 specimen, Society Islands, Moorea Island, fore reef between Cook’s and Opunohu Bays, 17°28.632′ S, 149°49.836′ W, in coralline pavement, 0–2 m, 6 July 2006, G. Paulay leg., 75% EtOH ( UF 400881); several specimens (only photographs examined, Fig. 1 A–C, F), same collection data as preceding, 0 m, 10% formalin fixed and transferred to 75% EtOH ( UF 400847, UF 400849).

AUSTRALIA: many bodies, all without shells, Great Barrier Reef, Queensland, Yonge Reef, inner reef, 14°35.100′ S, 145°37.020′ E, on dead branching coral, 3 m, Jan. 1975, P. Hutchings and P. Weate leg., 5% formalin ( AM C.464342).

Description

TELEOCONCH. Apertural diameter to 2.3 mm, diameter of expanded ‘chamber’ behind aperture up to 4.1 mm; diameter of last whorl up to 10.4 mm. Up to 3 whorls coiled concentrically; entirely embedded in substrate (including dorsal surface of shell) with only aperture visible ( Fig. 1A ); aperture flush with or countersunk below surface. Shell very thin, delicate. External surface entirely surrounded by substrate matrix, but white when cleaned; sculpture of very low transverse lamellae ( Fig. 2M ). Interior surface white with transverse stripe of brown on columellar surface of last whorl (in ‘chamber’) ( Fig. 1 B–C).

PROTOCONCH ( Fig. 2 A–D). Hatchling protoconch height 657.27 ± 40.27 μm (mean ± SD, n = 3), diameter 561.94 ± 47.89 μm (mean ± SD, n = 4). Sculpture absent on first whorl, then consisting of up to 14 heavy axial ribs. Space between ribs about 3 times rib width. According to developmental stage, protoconchs may be yellow to brown in color ( Fig. 1M ), with latter stage approaching that of fully developed protoconch in number of whorls and development of labrum.

OPERCULUM ( Fig. 1 G–L). Diameter up to 3 mm (Rapa Iti), 2.5 mm (Moorea) or 1.9 mm (Yonge Reef). Orange cream white peripherally, with a reddish band toward external edge ( Fig. 1 D–E, G); formalin fixed material turns whitish, but some specimens retaining reddish band close to edge. Lamina on exterior surface ruffled ( Figs 1 H–L, 2G–H). Interior surface with very tall, spindle-shaped mammilla, up to 2.3 mm (Rapa Iti, Fig. 2E ), 2.9 mm (Yonge Reef) or 4 mm (Moorea) long, golden in color in freshly dissected opercula (e.g., Fig. 1G ) from Rapa Iti and Moorea. Opercula heavily encrusted with algae and debris.

RADULA ( Fig. 2 I–L). Length of ribbon up to 1.5 mm, width up to 200 µm; up to 35 rows. Central tooth with large central cusp, flanked on each side by 3 smaller cusps. Lateral tooth with interlocking grooves for central and marginal teeth; main cusp flanked on outer side by 3 cusps, on inside by 1 cusp. Inner marginal tooth slender, elongate main cusp flanked on outer side by 2 cusps, on inner side by 1 cusp; outer marginal tooth with 1 cusp on inner side, smooth on outside; base straight and simple.

BODY EXTERNAL MORPHOLOGY AND COLORATION ( Fig. 1 B–F). Body length up to 13 mm (Rapa Iti and Moorea populations) or up to 7 mm (Yonge Reef population), occupying last whorl of shell. Columellar muscle very short, extending <0.5 whorl. Food groove with convoluted flap on outer margin. Adult female mantle divided by pallial notch extending <0.3 times mantle length. Color in life (Rapa Iti population): head-foot translucent white overlaid with mottled white, black and orange pigment patches, with black pigment more concentrated in center of head and around lips ( Fig. 1D ); sides of head behind cephalic tentacles showing large, almost fused, white patches forming a band in continuity with cephalic tentacles, with few orange speckles; side of foot with large orange and white pigment patches ( Fig. 1E ); cephalic tentacles with yellowish white small patches; mantle edge with a large external band of black pigment. Color in life (Moorea population): head-foot color translucent white overlaid with mottled pale yellow pigment patches around anterior surface of opercular lobe; sides of head with diffuse patches of opaque white pigment; dorsal surface of head around base of tentacles and lips with scattered black and white speckles; cephalic tentacles white; mantle margin opaque white. Color of specimens after preservation in 75–95% ethanol or formalin: entirely cream with scattered black speckles on dorsal surface of head and mantle margin.

PALLIAL AND REPRODUCTIVE ANATOMY ( Fig. 3 A–F). Gill 0.2× mantle width; gill leaflets tall, breadth half height; 16 leaflets per mm. Osphradium 3.5 mm long; margins smooth; anterior tip bent 180° around columellar muscle. Anus protruding from mantle cavity; fecal pellets cigar-shaped. Hypobranchial gland not discerned. Seminal receptacle attached to tip of proximal diverticulum from pallial oviduct. Male reproductive system not observed.

EGG CAPSULE. A single stalked egg capsule was found attached to the internal side of the shell of a female ( Fig. 1M ), containing seven embryos close to hatching. In another female a free embryo was found in the mantle cavity. Four of the seven embryos of this egg capsule were prepared for SEM observation ( Fig. 2 A–D).

Development and ecology

Adults are common on the reef crest in the wave zone, gregarious but not growing in contact with each other. Some of the specimens collected on Rapa Iti were found on a large dead Acropora coral head at a depth of 30 m, which was not apparently displaced from shallower reef: given these findings the known depth range is 0– 30 m. Specimens from Rapa Iti (MNHN IM-2000-31685) and Moorea (UF 400847, Fig. 1A ) appear to have grown on dead coral substrates in association with an unidentified species of coralline algae.

Distribution

Known from the southern central and west Pacific, specifically Rapa Iti Island and Moorea ( French Polynesia), and the Great Barrier Reef in Australia.

Figures

Fig. 1. Novastoa rapaitiensissp. nov.A. Living specimens embedded in coralsubstrate with only apertures and heavily encrusted opercula visible (UF 400847, Moorea Island, French Polynesia, photographs by G. Paulay). B–C. Preserved specimen fractured in plane perpendicular to surface, showing both halves of broken shell and animal embedded in coral (UF 436684, Moorea Island, French Polynesia). D–E. Living specimen from Rapa Iti (MNHN IM-2000-31685) just after extraction from the shell. F. Living specimen embedded in coral that has been fractured in plane perpendicular to surface (UF 400849). – G–L. Lateral views of opercula. G. Operculum from Rapa Iti as photographed in the field just after dissection (not from the type series). H. Operculum from the Moorea Island population, French Polynesia (UF 436684). I. Operculum from the Rapa Iti Island population, French Polynesia (MNHN IM-2000-31684). L. Operculum from the Yonge Reef population, Australia (AM C.464342). – M. Egg capsule after removal from interior shell wall (more developed embryos shown in Fig. 2A–D).

Fig. 2. Novastoa rapaitiensis sp. nov. A–D. Pre-hatching larval shells from egg mass of Fig. 1M. E–F. Operculum of specimen from Rapa Iti (not from the type series). G. SEM image of lateral view of operculum, with lamina stripped away to expose underlying structure (MNHN IM-2000-31684, Rapa Iti Island, French Polynesia). H. SEM image of exterior surface of operculum (MNHN IM-2000-31684, Rapa Iti Island, French Polynesia). I. Radula of specimen from Rapa Iti. L. Central section of radula (MNHN IM-2000-31684, Rapa Iti Island, French Polynesia). M. SEM image of teleoconch sculpture after removal of surrounding substrate (UF 436684, Moorea Island, French Polynesia).

Fig. 3. Anatomy of Novastoa rapaitiensis sp. nov. A–B. Male specimen (holotype, MNHN IM-2000- 27249, Rapa Iti Island, French Polynesia). A. Right view. B. Dorsal view of anterior body. – C. Female specimen, right view (UF 436684, Moorea Island, French Polynesia). – D–E. Female specimen (AM C.464342, Yonge Reef, Australia). D. Dorsal view of anterior body. E. Mantle cavity. – F. Leaflet from mid-section of gill (UF 436684, Moorea Island, French Polynesia).