Minaselates paradoxa, Cuezzo & Pena, 2017

Cuezzo, Maria Gabriela & Pena, Meire Silva, 2017, Minaselates, a new genus and new species of Epiphragmophoridae from Brazil (Gastropoda: Stylommatophora: Helicoidea), Zoologia (e 13230) 34, pp. 1-12 : 3-9

Minaselates paradoxa sp. n.

http://zoobank.org/ 9AACED00-8AFB-4736-85DC-14A3399A04CB

Figs 1–26

Diagnosis. Shell globular, with three spiral continuous pigmented bands, the middle, equatorial band thinner. Protoconch granulose. Dorsal side of teleoconch with axial lines bearing triangular lamellae, ventral teleoconch with wavy, concentric, spiral grooves. Imperforate umbilicus. Jaw smooth. Kidney triangular, long and thin, of about 60 to 70% the length of the lung roof. Vas deferens insertion in lower portion of flagellar caecum. Strong, short muscular penial retractor inserting at proximal epiphallus.

Etymology. The species name derives from the Greek paradoxos meaning “strange, contrary to expectation” ( Brown 1979) as this is a species of Epiphragmophoridae that was not expected to occur in the state of Minas Gerais, Brazil.

Description. Shell ( Figs 2–13) dextral, helicoidal with 4¾ convex, solid whorls. Coloration pale brown with three spiral darker brown bands more separated from each other in the body whorl.Medial pigmented band thinner than the other bands ( Figs 2–7). Suture impressed.Protoconch of 1½ whorls, covered by oval, tightly arranged pustules ( Figs 8, 9). Dorsal side of teleoconch with slightly curved axial growth lines that, at higher magnifications, appear as axial thin lines bearing broad-base triangular lamellae. These axial lines are not continuous and are separated by narrow spaces with wrinkles. Each lamellae has an axis from the base to the upper extreme of the triangle ( Figs 10–13). The long axes of the lamellae are perpendicular to the shell sutures. This sculpture looks like granules at naked eye. Wavy spiral grooves below the periphery, and in the basal surface area. Peristome thin, reflexed, some specimens showing a basal thickening and or an incipient palatal tooth. Aperture roundish, without angulation, and rounded in the palatal zone, well reflected in the columellar zone covering the umbilicus. Shell imperforate. Shell measurements. Table 1, Fig. 1. Digestive system. Radula ( Figs 14–17) Central tooth long, unicuspid. Lateral teeth long, with incipient lateral cusps, of about 54–56 µm (n = 10). Marginal teeth bicuspid, similar to laterals in shape and size. Jaw ( Figs 18, 19) Horseshoe slightly arched, translucent, with no division.Surface almost smooth with thin, transverse grooves visible with high magnification. Pallial system ( Figs 20, 21) Kidney triangular, long and thin, of about 60 to 70% the length of the lung roof. Main pulmonary vein thick, splitting into two secondary branches before reaching mantle collar; pulmonary roof dark grey in color, furrowed by well marked, but lesser minor transverse veins. Secondary ureter runs parallel to rectum, completely closed until reaching mantle collar. Ureteric interramus triangular in shape, deeply excavated. Genital System ( Figs 22–26) Terminal genitalia with dart apparatus and two mucous glands ( Figs 22–24). Right ommatophore retractor crosses the distal genital system between penis and vagina. Vagina long. Penis and vagina entering side by side in atrium. Bursa copulatrix with a globular sac and short, thick duct. Bursa copulatrix slightly longer than free oviduct. Single dart sac muscular, with medial constriction, ending in the atrium. Upper dart sac inverted pear shaped, lower portion of dart sac bellow constriction cylindrical, thicker ( Fig.24). Two unequal mucous glands with their respective thin efferent ducts inserting independently above the dart sac constriction ( Fig. 25). One of the glands bean shaped with medial duct and the other oval with one end bulkier than the other. Vas deferens is a long, narrow duct that passes between one of the mucous glands and the dart sac, over the penial sheath, going down it adheres to penis-vagina at angle with connective tissue and then rises parallel to the penis complex to insert bellow the flagellar caecum. Vas deferens insertion marks the limit between epiphallus and flagellum. Penial complex tubular without external differentiation between penis and epiphallus. Short distal muscular penis sheath. Penial retractor muscle thick inserting in proximal epiphallus. Penial cavity occupied by several thin wavy pilasters and an oval verge sculptured with overlapping lamellae ( Fig. 26). Penis longer than epiphallus, limits differentiated through their particular inner sculpture. Penial sheath short of about 1/5 of penial length. Epiphallus inner cavity with three thick pilasters. Proximal epiphallus with a rounded caecum where the vas deferens inserts. Flagellum tubular, longer than epiphallus. Spermoviduct long with uterus zone plicated transversal to the longitudinal axis. Albumen gland bean shaped with a prominent fertilization pouch-spermathecal complex (FPSC). Atrium short.

Type locality. Brazil, Minas Gerais: Itacarambi, National Park Cavernas do Peruaçu , Vale dos Sonhos (523m, X = 0599645, Y = 8343426), M.S. Pena, A. Suhett, D.C. Souza leg., December 2010, ( MNRJ 34.580 ), Holotype (ethanol preserved specimen).

Other material examined. Brazil, Minas Gerais: Itacarambi, National Park Cavernas do Peruaçu , Nossa Senhora Aparecida Farm (532 m, X = 0589284, Y = 8328970), M.S. Pena, A. Suhett, D.C. Souza leg., December 2010, ( IBN 21 -S, MLP-Ma 14216), dry shells, ( IBN 861 ), ethanol preserved specimens . Paratypes. Brazil, Minas Gerais: Itacarambi, National Park Cavernas do Peruaçu, Brejal , Peruaçu River side (663 m, X = 0579404, Y = 8332170), ( MCN 192 ), dry shells . Brazil, Minas Gerais: Itacarambi, Natiomal Park Cavernas do Peruaçu, Janelão Cave (714 m, X = 0581514, Y = 8329046) M.S. Pena, A. Suhett, D.C. Souza leg., December 2010, ( MCN 208 ) .

Distribution. Thus far known only from National Park Cavernas do Peruaçu, northern region of Minas Gerais, Brazil.

Remarks. Minaselates differs from all known species of Epiphragmophora by having a granulose protoconch, the shell spire with a blunt apex, and by the wavy, spiral grooves in the ventral region of the shell. The fused, imperforate umbilicus on the shells of this new species is not typical of Epiphragmophora . Most of species of the genus present an open, perspective umbilicus. The exceptions are E. argentina (Holmberg, 1909) and some specimens of E. variegata Hylton Scott, 1962 . The presence of wavy spiral grooves at the base of the shell of M. paradoxa sp. n. is noteworthy, sharply contrasting with the condition found in all other species of Epiphragmophora , where it is absent, except for E. (Pylsbrya) farrisi (Pfeiffer, 1859) , which has shallow spiral lines. Minaselates paradoxa sp. n. also differs from the species classified in Epiphragmophora in the shape and length of the kidney, and the smooth jaw. In the species of Epiphragmophora for which the anatomy has been studied, the kidney is no more than half the length of the pulmonary roof, while the jaw is ribbed. A noteworthy character present in Minaselates paradoxa sp. n. is the presence of a flagellar caecum, a structure not found in Epiphragmophora . In this new species, the vas deferens inserts in the lower portion of the caecum. The penial retractor muscle in Epiphragmophora is mostly long and thin, inserting in the epiphallus, while in Minaselates paradoxa sp. n. this muscle is stronger, inserting in the caecum. M. paradoxa sp. n. is isolated from the area of distribution of Epiphragmophora , whose area of highest species richness is in the western portion of South America.

Minaselates paradoxa sp. n. resembles some species of Pleurodontidae by the presence of complex structures in the terminal genitalia of the male, such as the flagellar caecum. It is also similar to some Pleurodontidae in its long and thin kidney, the crowded granules in the surface of the shell protoconch, the globular general shape of the shell, the complex microsculpture on the teleoconch and in its smooth jaw. The presence of a flagellar caecum is noteworthy in Minaselates , this structure being absent in Epiphragmophoridae , while it is characteristic of some Pleurodontidae such as Polydontes Montfort, 1810 and Pleurodonte incerta (Férussac, 1823) ( Cuezzo 2003) .

In Minaselates , however, the vas deferens inserts in the flagellar pouch while in Polydontes the vas deferens inserts above this caecum. At first glance, the shell of this new species is very similar to some species of Pleurodonte ( Pleurodontidae ), except for the presence of concentric sculpture below the periphery, and in the basal area. It also differs in the morphology of the terminal genitalia that has a dart complex and a different flagellum shape. In Pleurodonte , the vas deferens is twisted around the epiphallus, descending to the peni-oviducal angle, while in M. paradoxa sp. n. the vas deferens runs straight, parallel to the penis complex, without looping around the epiphallus. Most of the Helicoidean families have a ribbed jaw or ‘odontognath jaw’, except for the Sagdidae with a ‘stegognath jaw’ and the Sphicterochilidae and Cepoliinae with a smooth jaw (‘oxygnath jaw’) ( Cuezzo 2003). In M. paradoxa sp. n. the jaw was found to be smooth, only having fine transverse lines visible with electron microscopy, similar to jaws in Caracolus Montfort, 1810 and Labyrinthus .

Minaselates paradoxa sp. n. is distributed within a National Park area where Cerrado and Caatinga are the dominant biomes. These are considered high diversity hotspot areas. Within these hotspots areas specimens were collected in typical deciduous or semi-deciduous forests called Seasonally Dry Tropical Forests (SDTF) ( Pennington et al. 2000, Prado 2000). These types of forest are drought-adapted, tree-dominated ecosystems with a more or less continuous canopy. Grasses are not a significant element in these forests, which are currently scattered in eastern South America. A hypothesis has been advanced predicting that SDTFs were more widespread during drier glacial climates, and that their fragmentation during the current wet interglacial period has contributed to speciation and the distribution patters of species observed today ( Pennington et al. 2000, Prado 2000). This hypothesis is for the most part based on the assessment of floristic links among species assemblages in the SDTF areas ( Sarkinen et al. 2011). Land snails inhabiting this type of dry forest, from the Cerrado and Caatinga hotspots areas, have been scarcely studied and consequently their conservation status is unknown. Most vertebrates and plants have been more extensively documented in the Cerrado and Caatinga hotspots areas ( Overbeck et al. 2015), but this is not the case with many invertebrate groups.