Tag Archives: anatomy

Omalonyx unguis in Argentina

Recently, Guzmán et al. reported on this species with the following abstract: “Omalonyx unguis (d’Orbigny, 1837) is a semi-slug inhabiting the Paraná river basin. This species belongs to Succineidae, a family comprising a few representatives in South America. In this work, we provide the first record for the species from Misiones Province, Argentina. Previous records available for Omalonyx in Misiones were identified to the genus level. We examined morphological characteristics of the reproductive system and used DNA sequences from cytochrome oxidase subunit I (COI) gene for species-specific identification. These new distributional data contribute to consolidate the knowledge of the molluscan fauna in northeastern Argentina”.

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In the paper also figures of the shell and the genitalia are presented. The authors were likely unknown of the revisionary work of Vidigal et al. (2018), who showed that the correct name of this species is Omalonyx matheroni (Potiez & Michaud, 1835).

Guzmán, L.B. et al., 2018. First record of the semi-slug Omalonyx unguis (d’Orbigny, 1837) (Gastropoda, Succineidae) in the Misiones Province, Argentina. – CheckList 14 (5): 705-712.


Brazilian Solaropsis

A recent paper by Cuezzo et al. discusses the position of Solaropsis brasiliana (Deshayes, 1832) and its relatives. Their abstract reads: “A detailed anatomical revision on Solaropsis brasiliana (Deshayes 1832) has been carried out. New characters on shell, anatomy of soft parts, and a review of the genus distribution in South America, as well as clarification on S. brasiliana distributional area are provided in the present study. Solaropsis brasiliana is diagnosed by its globose, solid, and hirsute shell, with periphery obsoletely angular, bursa copulatrix with a thick, long diverticulum, a thick, long flagellum and a penis retractor muscle forked, with the vas deferens passing through it. This compiled information was used to test the phylogenetic position of S. brasiliana within South American Pleurodontidae through a cladistics analysis. In the phylogenetic hypothesis obtained, S. brasiliana is sister group of S. gibboni (Pfeiffer 1846) and the monophyly of thegenus Solaropsis Beck is also supported. Here, we sustain that the distribution of S. brasiliana is restricted to Brazil, inhabiting the States of Rio de Janeiro, Espírito Santo, Bahia and Minas Gerais”.

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This study, which carries a somewhat misleading title, deals *not* with the phylogenetics of this group in the sense of molecular studies. The authors have made a cladistic analysis using morphological characters, a method that has some support in a restricted group of authors and had better be indicated as such to avoid confusion with the more generally used terminology.

The authors have included in their dataset the monotypic genus Olympus, described from the Pantepui region on the Brazilian-Venezuelan border. They suggest there are but slight differences with Solaropsis undata (Lightfoot, 1786) in their anatomy, and therefore “the validity of Olympus as a separate genus from Solaropsis, should be carefully considered until more information is available”. I would suggest that molecular studies might be able to clear this issue.

Cuezzo, M.G. et al., 2018. Solaropsis brasiliana, anatomy, range extension and its phylogenetic position within Pleurodontidae (Mollusca, Gastropoda, Stylommatophora). – Anais da Academia Brasileira de Ciencias, 90 (3): 2753-2765.

Ventania from Argentina

Pizá et al. just published a paper in which they redescribed the single Ventania species known from Argentina.

“Although the presence of apertural folds and lamellae is the most recognizable character of the Odontostomidae, some species lack them, mostly in Anctus Martens, 1860, Bahiensis Jousseaume, 1877 and Moricandia Pilsbry & Vanatta, 1898. Eudioptus avellanedae Doering, 1881 – a slender odontostomid species that lacks even the slightest trace of folds or lamellae in its shell aperture – was however transferred to Odontostomus by Pilsbry in 1902 on the basis of its building forward of the aperture-margins. It is currently placed in its own monotypic subgenus, Cyclodontina (Ventania) Parodiz, 1940, on the basis of about the same argument. In this paper we redescribe its shell morphology and, for the first time, describe the internal anatomy of the pallial complex and the reproductive and digestive systems. The presence of a spongy gland in the pallial complex; of a short penis sheath with no retractor muscle; of a bursa copulatrix duct longer than spermoviduct, and of an epiphallic gland strongly support the inclusion of this unusual species in Odontostomidae. The species is diagnosable by the sculpture of the protoconch, which is not smooth as previously described, but has waved axial ribs crossed by spiral lines in young specimens; the distinctive external and internal shape of the bursa copulatrix duct; the internal penis wall divided in three regions of different sculpture; the smooth inner wall of the vagina; the long and cylindrical epiphallus with a distal widening indicating the presence of an epiphallic gland, and the penis retractor muscle inserted in the distal end of a short flagellum. These characters support the validity of Ventania Parodiz, 1940, different from Cyclodontina Beck, 1837”.

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The first two authors are known to have published already a series of thorough papers on Odontotomidae of Argentina. This paper follows in this line and gives convincing arguments why Ventania should be considered a separate, monotypic genus.

Pizá, J., Cazzaniga, N.J. & Ghezzi, N.S., 2018. Redescription of Ventania avellanedae (Stylommatophora: Odontostomidae), a land snail endemic to the Ventania Mountain System, Argentina. – Zoologia, 35: e17786 (11 pp.). DOI: 10.3897/zoologia.35.e17786

Helicina: anatomical data

Luiz Simone just published a paper on the anatomy of Helicina variabilis, a typical member of the family Helicinidae, which occurs in Brazil.

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 features. The study revealed absorption of the internal shell whorls; a diaphragm muscle connected to the floor of the pallial cavity; 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”.

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In the discussion of the paper Simone highlights the features that are interesting for the taxonomy of the group. The bursa copulatrix has a branched structure which may be useful in distinguishing different species. Comparisons are being made to related groups such as the Neritidae and to recent studies on the higher systematics of these groups. All in all an excellent paper, especially by the nicely detailed anatomical figures.

Simone, L.R.L., 2018. Phenotypic features of Helicina variabilis (Gastropoda: Neritimorpha) from Minas Gerais, Brazil. – Papéis Avulsos de Zoologia, 58: e20185832 (9 pp.). http://doi.org/10.11606/1807-0202/2018.58.32

An Omalonyx revisited

Arruda et al. (2016) recently published a revaluation of an Omalonyx species from Brazil. Species from this group are notoriously difficult to discern. “Omalonyx geayi Tillier, 1980 was originally described on the basis of specimens from Kaw swamp, French Guiana. This species distinguished from other of Omalonyx d’Orbigny, 1837: (i) by hermaphrodite duct twice as long and sacculate, without radial ducts but a funnel-shaped insertion on the ovariotestis, and (ii) by longitudinal wrinkled folds on the phallus inner wall. Two recent collections – from Trinidad and Carauari (Amazonas, Brazil) included specimens with ovariotestis and hermaphrodite duct morphologies similar to that originally described for O. geayi, but with phallus morphology not consistent with identification as O. geayi. A further eight lots, from Suriname, Ecuador, Brazil (Amazonas and Alagoas States), Bolivia and Cayenne-Kourou Road in French Guiana comprised specimens with phallus morphology analogous to O. geayi and ovariotestis and hermaphrodite duct similar to that of other Omalonyx species. Based on histological examination, and earlier phylogenetic analyses of morphological characters, we conclude that the ovariotestis and hermaphrodite duct conditions previously described for O. geayi were based on parasitized specimens. Accordingly, O. geayi is redescribed, and new information presented on the species’ wide distribution in South America”.

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Based on histological and anatomical research, the authors conclude that the original description was based on parasitised specimens in which the ovariotestis and proximal hermaphrodite duct were deformed. O. geayi as currently understood is occurring more broadly in South America than previously thought. The study was based on specimens from Trinidad, Suriname, French Guiana, Ecuador, and Brazil.

Arruda, J.O., Barker, G.M. & Thomé, J.W., 2016. Revaluation of the taxonomic characters and distribution of Omalonyx gaeyi (Gastropoda, Succineidae). – Iheringia, Zoologia, 106: e2016019 (6 pp.). DOI: 10.1590/1678-4766e2016019

More on Argentinian Bostryx

María José Miranda has recently published a new study on several Bostryx species from central western Argentina. As always, this is a thorough paper with lots of anatomical data.


The abstract reads: “The genus Bostryx Troschel, 1847 is endemic to South America, extending from Ecuador to Chile and Argentina. The southernmost Argentinian species of the genus that inhabit San Luis, San Juan and Mendoza provinces, specially the pre-Andes, Andes and Sierras Pampeanas mountain ranges, were examined. This is the first time the anatomy of Bostryx pastorei (Holmberg, 1912), Bostryx reedi (Parodiz, 1947) and Bostryx strobeli (Parodiz, 1956) has been described. Bostryx cordillerae (Strobel, 1874) is re-described regarding shell and anatomy due to new morphological data. The main differences among the species examined are based on shell characters. The distribution of Bostryx mendozanus (Strobel, 1874) and Bostryx cuyanus (Pfeiffer, 1867), other species found in this region, was also discussed”.

As she cited my publication about the subfamily Bostrycinae (Breure, 2012), I feel entitled to correct a possible misinterpretation. From her text it gives the impression that I have a very restricted view of this subfamily, leaving out all species not listed in my 2012 paper. The contrary is true. Page 3 of my paper explicitly stated that the list presented is incomplete, and further research should show which other species belong to this monophyletic clade. As the shell shape may be very misleading, which is corroborated in Miranda’s paper, I invited further research using anatomical and molecular data. Miranda’s paper is a welcome contribution to this end, although she has not presented phylogenetic data which could supplement the available data in GenBank. Hence there is room for further additions…

Breure, A.S.H., 2012. The status of the genus Bostryx Troschel, 1847, with description of a new subfamily (Mollusca, Gastropoda, Bulimulidae). – ZooKeys 216: 1-3.
Miranda, M.J., 2015. The genus Bosoryx in central western Argentina: anatomical and distributional description of four of its southernmost species (Gastropoda, Bulimulidae). – Iheringia, Zoologia 105: 484–498.

New Brazilian species (1)

Two papers were just published by Simone and Salvador, of which today the one about species from Minas Gerais. As usual these authors are keen to show the need for conservation of habitats which may house endemic or new species.


“A sample of land snails was recently collected in a fragment of Atlantic rainforest, in the vicinities of the city of Nanuque (north of Minas Gerais state, Brazil), totaling 15 species. The following new species are herein described: Leiostracus carnavalescus n. sp. and Rhinus botocudus n. sp. (Bulimulidae), and Obeliscus boitata n. sp. (Subulinidae), the first two accompanied by anatomical descriptions. Moreover, the geographical ranges of some species are extended to Minas Gerais: Auris bilabiata, Bahiensis cf. bahiensis, Cyclopomops moricandi, Dysopeas muibum, Helicina boettgeri, Helicina variabilis, Prohappia besckei, and Rectartemon piquetensis. The discovery of new species in such a small forest fragment is a clear reminder of how little the Brazilian terrestrial snail fauna is known. It also points to the fact that these few remaining forest fragments may house many new and possibly endemic species and should, therefore, be properly preserved”.


It may be noted that this paper was available on ResearchGate on the 19th April 2016, while the header states as publication date “30.IV.2016”.

Simone, L.R.L. & Salvador, R.B., 2016. Taxonomical study on a sample of land snails from Nanuque (Minas Gerais, Brazil), with descriptions of three new species. – Stuttgart Beiträge our Naturkunde A, Neue Serie 9: 9–30.