Tag Archives: succineidae

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”.

Schermafbeelding 2018-11-08 om 16.19.41

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).

Reference:
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.

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Taxonomy of Omalonyx

A group of Brazilian authors have made a comprehensive study on the succineid genus Omalonyx, with interesting results.

“The genus Omalonyx d’Orbigny, 1837, includes neotropical semi‐aquatic succineid slugs and comprises six recognized species to date. Field surveys across continental South America recovered five of the six recognized species. According to the morphological characters traditionally included in Omalonyx descriptions, the specimens were tentatively identified as O. matheroni, O. pattersonae, O. convexus, O. geayi and O. unguis. Employing sequences of mitochondrial cytochrome oxidase I (COI) alone or combined with the nuclear second internal transcribed spacer (ITS2) in discovery methods of species delimitation (GMYC and STACEY) led to species delimitation hypotheses that, except for unambiguously supporting O. convexus, have no correspondence to morphologically based assignments. To choose the delimitation model that best fit our data, the hypotheses recovered by GMYC, STACEY and morphology and created by merging species recovered by those methods had their marginal likelihood estimated and compared using the Bayes factors. The best‐supported hypothesis distinguished two species besides O. convexus: one widespread over most of South America and the other restricted to Rio de Janeiro State, Brazil. Furthermore, the pattern of genetic structuring supports pathways connecting the Amazonian and Atlantic forests. This pattern is similar to that observed in terrestrial taxa (e.g., forest‐dwelling small mammals) and is different from the pattern for fully aquatic taxa.”

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This is a well-executed study that uses different methods to formulate several hypotheses. The best-supported one leads the authors to conclude that there are two species to be recognised: O. convexus (Martens, 1868) and O. matheroni (Potiez & Michaud, 1835). This result is interesting, the more since this group is extremely difficult to study using the morphology alone. Such integrative studies are thus the way forward, and should be attempted also for other groups of Neotropical snails.

 

Reference:
Vidigal, T.H.D.A. et al., 2018. Integrative taxonomy of the neotropical genus Omalonyx (Elasmognatha: Succineidae). – Zoologica Scripta, 47 (2): 174-186.

Galapagos micromolluscs

An interesting paper was recently published by Miquel & Bungartz on micromolluscs found among Galapagos lichens and bryophytes, including a new species.

The new species is a carnivorous snail, Scolodonta rinae, and this family is reported for the firt time from the Galapagos. Other species that were encountered are Pupisoma galapagorum, P. dioscoricola, Tornatellides chathamensis, Helicina sp., and Succinea sp.

The new species was found on the island of Santa Cruz.

Reference:
Miquel, S.E. & Bungartz, F., 2017. Snails found among herbarium specimens of Galapagos lichens and bryophytes, with the description of Scolodonta rinae (Gastropoda: Scolodontidae), a new species of carnivorous micro-mollusk. – Archiv für Molluskenkunde, 146 (1): 173-186.

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”.

Schermafbeelding 2017-04-05 om 10.02.04

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.

Reference:
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

New records from Baja California

Baja California is an area with a rather scarce land snail fauna, and limited focussed papers in literature. Clark & Salisbury (2016) report on a small collection made during a biodiversity survey inside the Sierra La Laguna Biosphere Reserve, where a new gold mine is being planned.

The snails reported are already known from other localities on the penisula, viz. Naesiotus rimatus (Pfeiffer, 1847), N. spirifer (Gabb, 1868), and Rabdotus sufflatus (Gould in Binney, 1859). A new record is a as yet unidentified Succinea species, which was only collected as dead shell material.

Reference:
Clark, W.H. & Salisbury, R., 2016. New land snail records for Baja California Sur, Mexico. –Conchylia, 47 (3-4): 59-64.

 

A new fossil Radiodiscus

Papers on Neotropical fossils are rare, but Sergio Miquel is a regular contributor of them. Although Turazzini & Miquel (2014) was overlooked by me, I mention the paper now it came to my attention. The abstract follows after the break.

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“Numerous fossil gastropods have been recorded in an edaphic level of the middle section of the the Aisol Formation (Mendoza Province, Argentina). This stratigraphic section bears an association of fossil mammals suggesting an early Pliocene age (possible Montehermosan SALMA). Up to four taxa of gastropods have been identified, belonging in Succinea Draparnaud (Succineidae), Gastrocopta Wollaston (Vertiginidae), Bostryx Troschel (Bulimulidae), and a new species of Radiodiscus Pilsbry and Ferriss (Charopidae). The fossil record of terrestrial pulmonate mollusks in Argentina is scarce and mainly restricted to the Quaternary. Thus, the record of these taxa is of paramount importance because it constitutes the oldest record of Gastrocopta and Succinea in Argentina, the first record of Bostryx in Mendoza Province, and the first record of the family Charopidae (Radiodiscus sanrafaelensis nov. sp.) in Pliocene deposits of Argentina”.

Reference:
Turazzini, G.F. & Miquel, S.E., 2014. A terrestrial gastropod community from the Early Pliocene (Neogene) of Mendoza, Argentina, with description of a new species of Radiodiscus Pilsbry and Ferriss, 1906 (Mollusca: Pulmonata: Charopidae). – Ameghiniana, 51(5): 396-404.

Snails of Trinidade Island, Brazil

In a brief research note Salvador et al. (2014) report the find of living specimens of two species. “For four decades it has been suspected that the endemic land snails of Trindade Island, Brazil, were extinct. Here we report finding live Succinea lopesi Lanzieri, 1966 and a species of Happia Bourguignat, 1889 on top of the island’s highest peaks. Happia is a new record for the island and possibly also a new endemic species. As Trindade’s environment has suffered much degradation due to introduced feral goats, such remote places might have acted as refuges for the snails. With the ongoing recovery of the native fl ora after the eradication of the goats, the snails’ populations might re-establish themselves.”  Of the other endemic species of Trindade, namely Bulimulus brunoi  (Ihering, 1917), Naesiotus arnaldoi  (Lanzieri and Rezende, 1971) and Vegrandinia trindadensis (Breure and Coelho, 1976) it still remains to be seen if they are extant or not.

Trindade_f2

Reference:
Salvador, R.B., Silva, N.G., Cunha, C.M., Simone, L.R.L. & Alves, R.J.V. (2014): Rediscovery of living snails on Trindade Island, Brazil — American Malacological Bulletin 32: 140–142.