Rubyspira elongata, Souza & Passos & Shimabukuro & Sumida, 2021

Souza, Bruno H. M., Passos, Flávio D., Shimabukuro, Maurício & Sumida, Paulo Y. G., 2021, An integrative approach distinguishes three new species of Abyssochrysoidea (Mollusca: Caenogastropoda) associated with organic falls of the deep south-west Atlantic, Zoological Journal of the Linnean Society 191 : -

RUBYSPIRA ELONGATA SP. NOV.

( FIG. 8)

LSID: zoobank.org:act: 049F3075-E8A5-4E39-AECE- C7640BBE9DC4.

Type locality: Off Espírito Santo, Brazil, 21º27’S, 39º54’W 1491 m, on and around organic falls (whale bones and wood parcels) .

Holotype: ZUEC-GAS 7918 ( Fig. 8A, F, K), sta. ES1500 (21°27’00.5”S, 39°53’47.4”W) off Espírito Santo State, Brazil – ‘BioSuOr Project’ coll., 20 May 2015, depth 1491 m. Measurements: shell height: 16.5 mm; shell width: 6.9 mm.

Paratypes: #1 ZUEC-GAS 7919 , sta. same as holotype (total of 11 specimens, three of them in Fig. 8B, C, E, G, H); #2 MZUSP 151715, sta. same as holotype (four specimens); # 3 MNRJ 23582 , sta. same as holotype (two specimens) .

Other materials examined: c. 50 specimens stored at ColBIO (Coleção Biológica Prof. Edmundo F. Nonato) at IOUSP. Collected in the same site and date as holotype .

Etymology: From elongatus (Latin), elongate. Due to the slender aspect of the shell. Used as a feminine adjective.

Diagnosis: Shell tall, multispiral, with a straight profile, almost plane suture; surface white, smooth; periostracum thin, translucent, forming fine spiral lines; body whorl slightly shouldered in its middle portion. Protoconch whitish, with 2.5 whorls, with a cancellate sculpture. Radula taenioglossate (formula 2 + 1 + C + 1 + 2), with central, lateral and marginal stout teeth, all with rounded denticles on cusps.

Shell: Adult shell of medium size, thick, tall, width about 45% of height; up to 16.5 mm in height and 6.9 mm in width, i.e. width about half shell height. Multispiral, with teleoconch formed by up to about seven smooth whorls, each one with a straight profile and delimited by a simple, not marked and almost plane suture; body whorl about half of shell height, slightly shouldered in its middle portion ( Fig. 8A, B, E–H, K, N). Umbilicus closed. Surface translucent white, smooth. Periostracum thin, translucent, forming fine spiral lines ( Fig. 8D). Aperture orthocline, nearly one-third of shell height in fully developed individuals ( Fig. 8A, B, E, H, K) (a half in smaller ones: Fig. 8C, I), teardrop-shaped, with smooth lips, the outer thin, with a straight profile in its upper, almost vertical half, shouldered in the confluence with the lower, straight half; inner lip formed by two straight upper and lower parts, the latter one vertical. Siphonal and anal canal absent. Apex often eroded, without the protoconch and first teleoconch whorls, sealed with a calcareous plug ( Fig. 8N). Protoconch whitish ( Fig. 8C, I), with 2.5 whorls ( Fig. 8L), maximum diameter 0.53 mm, with a cancellate sculpture composed by both distinct, welldefined spiral and axial cords ( Fig. 8I, J, L, M), the former ones absent in the upper-fourth of each whorl ( Fig. 8M); transition between the proto- and teleoconch well defined ( Fig. 8J, L, M). Operculum horny, thin, yellowish brown, paucispiral, with distinct growth lines and nucleus 35–40% height, width two-thirds the height; small relative to the size of the aperture.

Radula: About 0.5 mm long; length 5.5 times as broad in adult specimens ( Fig. 8O). Taenioglossan, formula 2 + 1 + C + 1 + 2 ( Fig. 8O, P). Central, lateral and marginal stout teeth, all with rounded denticles on cusps, larger in middle, decreasing in periphery ( Fig. 8P). Central tooth with quadrate base and triangular; lateral narrower. Both marginal teeth with same size and shape, longer and narrower than the lateral tooth.

Soft parts: Ventro-apical mouth, flat and small snout. Cephalic tentacles without eye lobes. Males aphalic. One large, pallial tentacle on the right and a smaller one on the left corner of the pallial margin near the end of the mantle.

Remarks: The shell of Rubyspira elongata resembles that of R. pescaprae and R. osteovora , but it is much more slender, bearing a more plane suture and smooth surface. This tall shell is easily distinguishable from the more globose ones of R. brasiliensis and R. goffredie . The juveniles resemble those of R. pescaprae , and the same traits that differentiate adult shell morphology is the best way to sort them. Rubyspira elongata radula markedly differs from other species of Rubyspira , mainly regarding its rounded denticles, which are present in all teeth. The larval shell morphology, with many whorls and a well-marked axial and spiral sculpture, suggest a planktotrophic development. Only few supposed fully grown specimens of R. elongata . were found, most collected specimens were juveniles.

The intraspecific divergence of R. elongata is lower than 0.5% for COI and 16S. Considering other Rubyspira species , R. elongata was least distant from R. osteovora (lower than 6%) and R. pescaprae (3%), for COI and 16S, respectively, while the most divergent species was R. goffrediae for both genes (COI: 14.5%; 16S: 10%) (Table 2).

Distribution: Only known from the studied area, off the south-eastern coast of Brazil (south-west Atlantic); at 1491 m deep. Most collected specimens were juveniles and all the animals came from the same site, found both on whale bones (~50%) and wood parcels (~50%).