First record of the invasive snail Sinotaia quadrata in an isolated lake in Buenos Aires City, Argentina

Abstract

The Asian freshwater snail Sinotaia quadrata is here reported for the first time in an isolated urban lake of Buenos Aires City (Argentina). By considering molecular information, the identity of the species is confirmed, and the Chinese / Japanese origin of the Argentine population is proposed. Furthermore, the risk of an imminent regional dispersion of this species is highlighted.

Key words
Alien species; Exotic; Snail; Introduction; Mollusca; Viviparidae

INTRODUCTION

The lake Lago de Regatas (34.56°S, 58.43°W) is located in the Parque Tres de Febrero (also known as “Bosques de Palermo”), in northeastern Buenos Aires City, Argentina. With approximately 98,000 m² and depths of up to 4 m (Rodríguez-Flores et al. 2019), it is the largest freshwater body in the area, and the habitat of numerous species of invertebrates and vertebrates (Zelaya & Pérez 1998, Gallotti & Gómez 2025). Since 1995 one of the authors (DZ) has periodically visited the lake, documenting its biological diversity. As part of these visits a total of 11 species of freshwater molluscs have been identified in the area. In early 2026, a gastropod species not registered during previous surveys, was found in this lake at high densities. The aim of this contribution is to report this finding and determine the identity and possible origin of the specimens.

MATERIALS AND METHODS

During two visits on January 4 and 9, 2026, the perimeter of Lago de Regatas was surveyed along the shoreline. Specimens of the “new” gastropod were hand-collected, its presence/absence in different areas of the lake (within 1 m of the shoreline) assessed, and densities evaluated from counts in random 30 × 50 cm quadrats. In addition, Genomic DNA was extracted from three specimens by using a CTAB–pKA protocol (Dayrat et al. 2011). The mitochondrial cytochrome oxidase I (COI) gene marker was amplified using universal primers (Folmer et al. 1994), cleaned through enzymatic reactions (Exo-FastAP) and sent out for bidirectional sequencing (Macrogen Inc., South Korea). Sequences were edited in MEGA 11 (Tamura et al. 2021) and compared with reference databases using BLASTn (Altschul et al. 1990) and the BOLD identification engine (accessed 6 February 2026). Closely matching sequences were retrieved from GenBank and BOLD and aligned with the newly generated sequences using ClustalW in MEGA 11. A 655 bp including 493 sequences was built; missing ends were completed with Ns. Haplotypes were collapsed using the DNAcollapser tool in FaBox (Villesen 2007); degenerate or unknown (N) sites were treated as a fifth state. Phylogenetic relationships were inferred using Maximum Likelihood in IQ-TREE (Trifinopoulos et al. 2016) with automatic model selection (K3Pu+F+R3) and 1,000 ultrafast bootstrap replicates (Hoang et al. 2017). Bayesian inference was performed in MrBayes v3.1.2 (Ronquist & Huelsenbeck 2003) with two independent runs of four chains for 10 million generations, sampling every 100 generations, until the average standard deviation of split frequencies reached ≤ 0.001. Convergence was assessed in TRACER v1.7.1 (Rambaut et al. 2018), discarding the first 10% of trees as burn-in. Anularya mansuyi (GenBank MN997901), was used for tree-rooting following O’Leary et al. (2021) and Miranda et al. (2022); sequences of “Mekongia lithophaga” by Hirano et al. (2019) (LC505788-90) were also included. After trimming ends and excluding short sequences, an alignment of 243 sequences 593 bp long was used to construct a haplotype network using the median-joining algorithm in PopArt v1.7 (Bandelt et al. 1999); degenerate or unknown (N) sites were here treated as matching any base, thus haplotypes were further collapsed. Sequence data are given in Supplementary Materials (Table SI).

RESULTS

Shell morphology and external anatomy supported a preliminary identification of this “unusual” gastropod as Sinotaia sp., from which males, females and juveniles were recognized (Fig. 1d–h). BLASTn showed 100% identity with sequences of “Sinotaia quadrata” and “S. aeruginosa”, while BOLD returned 100% match to Sinotaia / Bellamya (including “S./B. quadrata”, “B. angularis” and “B. dispiralis”). Bayesian and Maximum Likelihood analyses were congruent, recovering a well-supported clade, in which the specimens from Lago de Regatas (Argentina) clusters with specimens of S. quadrata (sensu Ye et al. 2021) from China, Japan, Taiwan, the Philippines, South Africa, Spain, France, and Italy (Fig. 2a, b). The haplotype from Argentina matched the most frequent haplotype, also occurring in China, Japan, and South Africa (Fig. 2c).

Figure 1
Sinotaia quadrata in Lago de Regatas, Buenos Aires, Argentina. a. General view of the lakeshore in which the species was found. b, c. Specimen occurrence in sites with high (b) and low (c) densities. d-h. Living specimens: d. Young specimen with pilose periostracum; e. Large specimen with smooth periostracum; f, g. Males; h. Female. Scale bars: b = 2 cm; c = 5 cm; d–f = 1 cm; g, h = 2 mm.

Figure 2
Molecular analyses. a. Phylogenetic tree obtained by Bayesian Inference. b. Collapsed clade of figure a, here expanded. Only posterior probabilities and ML ultrafast bootstrap supports above 0.80/80%, respectively, are shown. c. Median-joining network of COI haplotypes from specimens of S. quadrata. Node sizes are proportional to the number of sequences representing each haplotype. Lines indicate the number of mutations between haplotypes and black dots represent hypothetical nodes. Colours refer to the locality where the haplotypes have been found (see legend). Haplotypes below the curved dashed line belong to the clade expanded in figure b.

Specimens of Sinotaia quadrata, ranging from a few millimeters to ~4 cm shell length, were found along the entire western shore of Lago de Regatas, with lowest densities at the northern and southwestern heads (≈1 m⁻²; Fig. 1c), and highest densities in the middle shoreline (up to ≈1,000 m⁻²; Fig. 1b). It was always found in hard bottoms, with most of the specimens aggregated in the interstices between paving stones (Fig. 1b). Curiously, no individuals were detected during this study along the eastern shore of the Lago de Regatas, nor in the other three lakes present in the Parque Tres de Febrero.

DISCUSSION AND CONCLUSIONS

Sinotaia quadrata is a freshwater gastropod native to East Asia, where it occurs in China, Japan, Korea, Taiwan, Vietnam, Thailand and the Philippines (Lee 2009, Hirano et al. 2015). The species has also been introduced in Africa (South Africa: Miranda et al. 2022), Europe (Italy: Cianfanelli et al. 2017, Pastorino et al. 2021; Spain: Arias et al. 2020, Quiñonero-Salgado et al. 2022, Sánchez et al. 2023; and France: Arias et al. 2020), and America. In North America, although previously mentioned, records proved to correspond to a different clade (“S. cf. quadrata”: O’Leary et al. 2021; and Fig. 2a herein). In Central America there are unpublished records from Panamá and El Salvador (https://www.inaturalist.org/observations?subview=map&taxon_id=151151, accessed April 17, 2026). In South America, S. quadrata is currently only known from central Argentina, where it has been known since 2009 from streams in Córdoba Province (Ovando & Cuezzo 2012, Martin 2017, Reyna et al. 2018). In 2015 it was reported from near La Plata city, in Buenos Aires Province (Ferreira et al. 2017), and more recently from the adjacencies of the Río de la Plata and from Entre Ríos Province (Gutiérrez Gregoric et al. 2024). These areas of occurrence are not connected to each other, suggesting independent events of introduction or, eventually, local translocations of the species. The present finding provides the first record of the species in Buenos Aires City, in a lake isolated from the few other sites in Argentina where the species has been reported. The molecular studies performed herein reveal that these specimens most probably come from Asian populations, in particular from China or Japan. The high density of specimens documented in this lake as part of this study indicates that the species is established in this area; a fact also supported by the finding of numerous small specimens, which suggest a recent event of local reproduction. The fact that S. quadrata has not been recorded before in Lago de Regatas, an area periodically visited and sampled, leads us to infer its recent arrival (likely in the last year). How these specimens arrived at this lake is uncertain. The lake is supplied with semi-treated water from the Río de la Plata and receives rainfall runoff. Consequently, an introduction through Río de la Plata seems improbable. An alternative pathway may be found in the passive dispersal by birds. There are several documented cases worldwide of molluscs being translocated by birds (Green & Figuerola 2005 and references therein, Maciorowski et al. 2012, Saito et al. 2023). Some aquatic birds, like the Great Egret (Ardea alba), the Snowy Egret (Egretta thula) and the Neotropic Cormorant (Nannopterum brasilianum), which are resident in the area, move daily between Lago de Regatas and the Río de la Plata. However, none of these species cover in these movements the nearly 50 km that separate Lago de Regatas from Punta Lara, the only site where this species has been reported in the Río de la Plata so far. The presence of S. quadrata in Lago de Regatas seems to be a consequence of an independent, intentional (or accidental?) human introduction / translocation. In this regard, it is worth to say that specimens of this species were personally observed in 2025 being sold alive in the Barrio Chino district (Belgrano), located only 1.3 km from Lago de Regatas. Although impossible to confirm, this market may also be linked to the introduction of three other mollusc species in Lago de Regatas: Corbicula fluminea, Anodontites trapesialis and Diplodon sp. These species were detected in the lake in 2017, only a few months after they had been observed being sold in the Barrio Chino markets. All other mollusc species currently found in Lago de Regatas have been observed in this lake for more than 30 years, and also occur in the Río de la Plata, an area to which this lake was connected in the past.

The present finding of S. quadrata in Lago de Regatas highlights the risk of an imminent expansion of this species, particularly considering that the water level of this lake is regulated by a discharge gate that drains to the Río de la Plata (Rodríguez-Flores et al. 2019, Osvaldo Guerrica Echevarría, pers. comm.), and the daily movements of several bird species between these two areas. Once this happens, it is expected that the species will be rapidly regionally dispersed, upstream and downstream favored by the Río de la Plata tides, reaching the Paraná and Uruguay Rivers, as occurred previously with the bivalves Corbicula fluminea and Limnoperna fortunei (Darrigran 2004).

SUPPLEMENTARY MATERIAL

Table SI.

Table SI.

Acknowledgements

MG and DZ are members of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). The authors declare no conflict of interest.

• Data availability
  Voucher specimens have been deposited in the Invertebrates Collection of the Museo Argentino de Ciencias Naturales (MACN-In 45269); newly obtained sequences are available in GenBank (PZ498516). All other data are available upon request.

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Edited by

• Handling editor
  Renato Martins

Data availability

Voucher specimens have been deposited in the Invertebrates Collection of the Museo Argentino de Ciencias Naturales (MACN-In 45269); newly obtained sequences are available in GenBank (PZ498516). All other data are available upon request.

Publication Dates

• Publication in this collection
  17 Aug 2026
• Date of issue
  2026

History

• Received
  22 Apr 2026
• Accepted
  01 June 2026