The survey was an initial assessment of cave-dwelling land snails in a part of northern Brazil where the subterranean fauna remains poorly documented. The Carajás Speleological Province contains more than 1,500 registered cavities formed in iron-rich and silica-bearing rocks, commonly known locally as canga. Although Brazilian cave studies have concentrated largely on calcareous formations, Carajás offers a contrasting geological setting for gastropods, whose shells require calcium carbonate that is not necessarily abundant in these caves. The surrounding protected landscapes contain tropical forest and open vegetation on rocky substrates, but nearby areas have experienced substantial clearing associated with cattle ranching and mining.

Researchers visited caves during trips in August 2021, February and August 2022, and April 2023. At each site, they visually searched rock walls, sediments, leaf litter, decaying logs, bat-guano deposits and areas beneath rocks. Organic samples were also processed with a Winkler extractor to recover small invertebrates associated with leaf litter. No freshwater gastropods were recorded, despite the presence of small water bodies in some caves. Specimens were preserved either as empty shells or in 70–96% ethanol and deposited in collections at the Federal University of São Carlos and the University of São Paulo. The investigation combined detailed shell imaging, micro-computed tomography and DNA analysis of mitochondrial COI and 16S markers and a nuclear region containing ITS2 and part of 28S.

One of the new species, Rectobelus arsayae, is a small achatinid known from a single shell collected beneath a rock in the twilight zone of cave SB_0022 at Canaã dos Carajás. Its nearly cylindrical shell measures 10.2 millimetres high and 1.9 millimetres wide, with 10.5 whorls and a whitish-yellow to light-ochre surface. Computed tomography exposed structures that are difficult to see externally: a faint columellar fold extending along the body whorl and two internal palatal lamellae separated by about half a whorl. The authors considered accidental transport into the cave unlikely because of the shell’s fragility, but they classified the species provisionally as a troglophile because the available evidence comes from only one empty shell and does not establish a fully subterranean population.

The second new species, Scolodonta carajaensis, has a glossy, translucent tan shell and a conspicuous orange-red soft body. Its discoid shell is about 6 millimetres wide and 3 millimetres high, with approximately 4.5 whorls, a rounded D-shaped aperture, a simple peristome and a broad, deep umbilicus. Live animals occurred from entrance areas into aphotic parts of caves in both Canaã dos Carajás and Parauapebas, beneath rocks, among roots and on humid unconsolidated substrate near dripping water. The shell and body traits distinguish it from other Brazilian scolodontids, although the researchers cautioned that translucence alone does not constitute an adaptation to darkness because it also occurs in related species. No obvious troglomorphic features were observed.

Genetic results suggest that S. carajaensis also lives outside the caves. The holotype from Canaã dos Carajás and a paratype from Parauapebas had identical COI and 16S sequences, a 100% match indicating connectivity and gene flow between the sampled localities. The authors therefore considered the species likely to maintain an epigean population across Serra dos Carajás and classified it as a troglophile. This distinction matters because discovery in a cave does not by itself mean that an animal is restricted to the underground environment. Nevertheless, the new species was found in caves within a region shaped by mining, making the location of its type material relevant to efforts to protect narrowly distributed fauna.

The taxonomic work also revised the classification of Rectobelus, a genus of small, narrow-shelled achatinids. Treating Nannobeliscus as its synonym, the authors established the combination Rectobelus silvaevagus for the former type species of Nannobeliscus. They also recognized Nannobeliscus mariaisabelae as a junior synonym of Rectobelus birabeni. The two names had been based on specimens from the same Argentine province whose shells are indistinguishable in shape, size and whorl number, while the reported anatomical differences were considered subtle and known to vary within living stylommatophorans. Computed tomography showed that internal palatal lamellae visible in juveniles become enclosed within the shell as the animal grows, helping clarify why the structure had been used inconsistently in diagnoses.

Two known species also yielded significant new distribution records. Leptinaria parana, previously known from the vicinity of Belém, was found in Carajás caves approximately 550 kilometres farther south. Systrophia siolii was recorded about 630 kilometres southeast of its type locality near Monte Alegre, although the specimen was collected in epigean woodland near the caves rather than inside a cave. Both species remain endemic to Pará, which covers approximately 1.25 million square kilometres. The survey also produced the first Brazilian record of Tamayoa decolorata, a species known from French Guiana and reported in several Caribbean locations, where it is considered introduced. The Carajás snails were observed in caves and in anthropically disturbed areas near Parauapebas.

Leptinaria unilamellata and T. decolorata were the most frequently encountered gastropods in the caves, both by number of specimens and by number of occupied sites. L. unilamellata is widespread in the Neotropics and occurs in natural and disturbed habitats. Another achatinid could not be identified beyond the genus Dysopeas. Its overall shell form and ribbing did not fully match known Brazilian or Venezuelan species, and the COI sequence showed only 80.0–81.5% identity to the available sequence of Dysopeas muibum, the only recorded Brazilian member of the genus. Because all examined specimens were juveniles, the researchers could not confirm that they represented another new species. The inventory therefore combined confirmed novelties with an unresolved taxonomic candidate that requires further study.

Several live snails were collected on mixed guano from frugivorous and insectivorous bats, including specimens of Dysopeas sp., L. unilamellata and T. decolorata. Guano can provide food directly or support fungi consumed by subterranean invertebrates, but the study did not show that the snails were actively eating the deposits. The authors proposed a comparison of nitrogen-isotope signatures in snail tissues and different guano samples to investigate whether the animals obtain nutrients from guano. Overall, the baseline survey shows that Carajás caves contain a modest but taxonomically consequential land-snail fauna. Its two new species, first Brazilian records, range extensions and undescribed candidate demonstrate the value of repeated fieldwork in ferruginous caves while also leaving open questions about population structure, surface distributions and species boundaries.

Subject of Research: Terrestrial gastropod diversity and taxonomy in ferruginous caves in Serra dos Carajás, Brazil

Article Title: Terrestrial gastropods from caves in Serra dos Carajás, eastern Brazilian Amazon, with the description of two new species ( Eupulmonata , Stylommatophora )

Article References: Salvador, R. B., Ferreira-Santos, L., Cavallari, D. C., Gallão, J. E., & Bichuette, M. E. (2026). Terrestrial gastropods from caves in Serra dos Carajás, eastern Brazilian Amazon, with the description of two new species (Eupulmonata, Stylommatophora). ZooKeys, 1287, 213-237. https://doi.org/10.3897/zookeys.1287.194544

Image Credits: AI Generated

DOI: 10.3897/zookeys.1287.194544

Keywords: cave snails, new species, Serra dos Carajás, terrestrial gastropods, ferruginous caves, micro-computed tomography, DNA barcoding, biodiversity surveys, taxonomy, bat guano, Terrestrial, gastropods