Phenotypic features of Helicina variabilis (Gastropoda: Neritimorpha) from Minas Gerais, Brazil Luiz Ricardo L. Simone¹ ¹ Universidade de São Paulo (USP), Museu de Zoologia (MZUSP). São Paulo, SP, Brasil. ORCID: 0000-0002-1397-9823. E-mail: [email protected] Abstract. Helicina variabilis Wagner, 1827 (Neritimorpha, Helicinidae) is redescribed based on a sample collected in Nanuque, northern Minas Gerais, Brazil. The species description, previously based only on the shell, is expanded to the phenotypic fea- tures. The study revealed absorption of the internal shell whorls; a diaphragm muscle connected to the floor of the pallial cav- ity; a monoaulic pallial oviduct, with the female genital aperture inside the anal aperture, and the lack of a seminal receptacle and provaginal sac; and the pleural ganglia of the nerve ring connected with each other. The significance of these findings is discussed in the light of current taxonomic and phylogenetic knowledge. Key-Words. Atlantic Rainforest; Helicinidae; Anatomy; Morphology; Phenotype. INTRODUCTION on comparative anatomical information will be compared to those inferred using molecular ap- With the main goal of filling a gap in knowl- proaches (e.g., Uribe et al., 2016). edge of neritimorph phenotypic features, a more The Helicinidae constitute a terrestrial branch complete anatomical description of Helicina vari‑ of the Neritimorpha (Richling & Glaubrecht, 2008), abilis Wagner, 1827 is provided herein. Specimens a taxon with ~2,000 species in four superfami- of this species were collected during an expedition lies, Neritopsoidea, Hydrocenoidea, Helicinoidea by the naturalist and conchologist José Coltro Jr. (which includes the family Helicinidae), and and his team to the region of Nanuque in north- Neritoidea (Uribe et al., 2016), most of the species ern Minas Gerais state, which recovered many in the last two taxa. The helicinids are easily dis- land snails, most of them reported by Simone & tinguished from the more common Pulmonata Salvador (2016). This is another example of how snails in having a well-developed, normally cal- much remains to be discovered in a region of Brazil careous operculum, and the eyes placed at the that is historically the most explored and exploited, base of a single pair of cephalic tentacles. Their and in which the natural areas, mainly remnants of shells are discoid to globose, with a suture plane, the Atlantic Rainforest, are highly threatened, lack- sometimes carinate at the periphery, and an um- ing information that allows their preservation. bilicus absent. These features easily distinguish Knowledge of the helicinids as a whole is them from the other operculate land snails be- slight, although it is a relatively speciose group longing to Cyclophoroidea, which is basal to the (up to 750 species; Richling & Glaubrecht, 2008), Caenogastropoda (Simone, 2011). particularly in the Americas (Richling, 2004, 2014). Focusing on the Caenogastropoda, Simone Anatomical features in particular have been very (2011) included only a few neritimorph species as useful in comparative analyses, such as taxonomy outgroups; none of these were terrestrial, a gap and phylogeny, at all levels, from closely related filled by the present study. As in most branches species (e.g., Richling, 2009; Richling & Bouchet, of Mollusca, the anatomical features of helicinids 2013) to wider systematic studies, specifically in have been considered uniform and of limited use helicinids (Richling, 2004) and in gastropods in in comparative analyses (e.g., Bourne, 1911; Boss general (Simone, 2011). However, anatomical fea- & Jacobson, 1974). For this reason, most studies tures have been barely used in neritimorphs. As of helicinid systematics have focused on the shell part of a larger project on phenotypic features and and radula (e.g., Wagner, 1907-1911; Baker, 1922, phylogeny of the Neritimorpha (= Neritopsina), 1923). Only more recently have some anatomical Helicina variabilis was selected as one of the ter- characters, primarily from the reproductive sys- restrial representatives of the group, as it appears tem, been used as an additional tool to resolve to be a typical member of the family. Eventually, the systematics of the group (e.g., Richling, 2004, the estimated systematic relationships based 2009), mainly focused on the reproductive system. Pap. Avulsos Zool., 2018; v.58: e20185832 ISSN On-Line: 1807-0205 http://doi.org/10.11606/1807-0205/2018.58.32 ISSN Printed: 0031-1049 ISNI: 0000-0004-0384-1825 www.revistas.usp.br/paz www.scielo.br/paz Pap. Avulsos Zool., 2018; v.58: e20185832 Simone, L.R.L.: Phenotypy of Helicina variabilis from Brazil 2/9 The helicinids share some important neritimorph Systematics features, such as the absorption of the inner whorls of the shell, producing a sac-like, coil-less visceral mass Helicina variabilis Wagner, 1827 (Bourne, 1911). The type of radula, the shape of the col- (Figs. 1‑35) umellar muscles, and the calcareous operculum are ad- ditional synapomorphies (Simone, 2011). On the other Helicina variabilis Wagner, 1827: 25 (pl. 16, figs. 3-5) [see hand, using the study of Helicina variabilis as an exam- authority designation in Cowie et al., 2004]; Wagner, ple, together with literature data, it is possible to suggest 1906: 226 (pl. 13, figs. 2a-c.); Salgado & Coelho, some features that distinguish the helicinids at least from 2003: 152 (pl. 1, fig. 1); Simone, 2006: 41 (fig. 32); the marine Neritidae, as discussed below. Simone & Salvador, 2016: 10, 11, 29 (figs. 84-89). Type locality: Pará state, Brazil. MATERIAL AND METHODS Material analyzed: BRAZIL. Minas Gerais: Nanuque: The list of material examined follows the species de- MZSP 106171 (1 specimen), 106172 (4 specimens), scription. The specimens studied were collected in the vi- 106173 (1 shell). Bahia: NE Ilhéus; MZSP 128202 cinity of the city of Nanuque (~17°51’S 40°23’W, ~120 m (~2000 shells) (Femorale team col. xii/1994). elevation) in northern Minas Gerais state, very close to the border with the states of Bahia and Espírito Santo. Description The locality is a tiny fragment of Atlantic Rainforest close to the Mucuri River, surrounded by tomato fields and Shell (Figs. 1‑10): diameter ~12 mm, lenticular; diame- thus highly subject to anthropogenic impacts and deg- ter ~5/4 shell length. Base color white, with broad spiral radation. See Simone & Salvador (2016) for more details. band running along median upper portion of whorls; The snails were collected alive and preserved in 70% varying in thickness, sometimes covering all of upper ethanol. For dissection, each specimen was extracted portion of whorls, and changing from orange to light from its shell through an artificial window made in the brown or reddish purple; second, narrow colored band penultimate whorl with a metal file. The specimens were (of same color as other band and also varying in thick- dissected by standard techniques, under a stereomicro- ness, although less so) sometimes present on lower scope, with the specimen immersed in ethanol. Digital surface of whorls, closer to median portion. Both bands photographs were obtained for most dissection steps, stopping few millimeters before reaching peristome. as well as drawings with the aid of a camera lucida. The Peristome white. Spire angle ~90°. Protoconch of 1.5 radulae were mounted on stubs, coated with a gold-pal- whorls, acuminate, first 0.75 whorl smooth, rest sculp- ladium alloy, and examined by scanning electron micros- tured by axial parallel sinuous striae; transition to teleo- copy (SEM) in the Laboratório de Microscopia Eletrônica conch distinct. Teleoconch sculptured with weak axial of MZSP. parallel sinuous striae and with stronger spiral parallel striae. Whorl profiles slightly convex. Suture well marked. Anatomical abbreviations: aa, anterior aorta; ag, albu- Very weak carina on body whorl. Aperture medium-sized, men gland; an, anus; ap, genital aperture; ar, adrectal si- prosocline, triangular, about as broad as high; ~2/3 shell nus; au, auricle; bc, bursa copulatrix; bg, buccal ganglia; length, ~3/5 shell width. Peristome reflected, with shal- cc, cerebral commissure; ce, cerebral ganglion; cg, cap- low furrow on median upper portion (following colored sule gland; cl, right columellar muscle; cr, left columellar band) and slight angle at junction of basal and columel- muscle; cv, pulmonary (efferent) vein; cy, statocyst; dd, lar regions. Body whorl ~3/4 shell length. Umbilicus im- duct to digestive gland; di, diaphragm or pallial floor; perforate. Internal visceral cavity ample, separated from dm, diaphragm muscle; dv, posterior diverticulum of head-foot cavity by thin septum (Figs. 9-10); occupying albumen gland; ec, esophageal crop surrounding odon- ~2/3 of shell volume; intra-sutural fold (vestigial internal tophore; ep, esophageal pouch; es, esophagus; ey, eye; coiling) low, but visible (Fig. 10). fp, female pore; fs, foot sole; ft, foot; go, gonad; gp, ped- al ganglion; il, intestinal haemocoelic loop; in, intestine; Head‑foot (Figs. 8, 30‑22): Color of exposed regions ki, kidney chamber; kl, kidney lobe; m1‑m13, extrinsic brown; snout pale beige (Fig. 8). Length ~3/4 whorl and intrinsic odontophore muscles; mb, mantle border; when retracted. Head protruded, occupying ~1/2 foot mj, jaw and peribuccal muscles; mo, mouth; mt, mantle; width. Tentacles stubby, simple, ca. four times longer ne, nephrostome; nr, nerve ring; oa, opercular pad; oc, than wide; tip blunt (Figs. 20, 26: te). Ommatophore odontophore cartilage; od, odontophore; om, ommato- (om) ~1/3 tentacle length, tip rounded; located close phore; op, calcareous operculum; ov, pallial oviduct; oy, to outer side of tentacle base. Eye (ey) located on ovary; pc, pericardium; pg, pedal gland; pl, pleural gan- ommatophore tip. Foot simple, thick, subtriangular glion; po, posterior odontophore cartilage; pu, pulmo- (Figs. 20-22: ft); anterior edge bilabiate, aperture of ped- nary cavity; ra, radula; rn, radular nucleus; rs, radular sac; al glands median, relatively deep (Fig. 20: pg). Distance rt, rectum; sc, subradular cartilage; sn, snout; st, stom- between anterior edge of foot and snout base ~1/10 ach; sy, statocyst; te, cephalic tentacle; tg, integument; whorl.