First Report of Giant African Snail (Lissachatina fulica) in a Protected Area of the Cottian Alps, Northwest Italy

Abstract

The Giant African snail (Lissachatina fulica) is listed among the top 100 worst invasive alien species. Native to East Africa, it has been introduced voluntarily or accidentally into more than 50 countries, where it impacts negatively on biodiversity, ecosystems, agriculture, and public health. Here we describe for the first time the finding of a specimen of L. fulica in a protected area of the Cottian Alps (Avigliana Lakes Nature Park, northwest Italy). The snail underwent morphometric analysis and species identification. Given its reproductive characteristics (i.e., hermaphroditism with self-fertilization), it poses a potential threat to the biodiversity of the area and is a vector of zoonotic parasites for humans and animals. Health monitoring of specimens found in the wild and those kept as pets is of crucial importance, as is the establishment of monitoring plans in these areas.

1. Introduction

Human activities have profoundly altered ecosystems and reduced their biodiversity. Globalization has relied on the movement of people and goods for international trade but has also brought with it invasive alien animal and plant species. When established outside their native areas, such species can have a negative impact on native communities, habitats, socioeconomic activities, and public health [1,2,3,4].

The Giant African snail (Lissachatina fulica), a terrestrial gastropod native to East Africa, is listed among the top 100 worst invasive alien species in the world [1,5,6]. It reduces biodiversity and causes serious economic and environmental loss (i.e., it feeds on the native plants, etc.) [7,8]. Beyond the threats it poses to ecosystems and agriculture, L. fulica is a public health risk because it acts as an intermediate host for parasites that can cause zoonotic diseases [9,10].

A member of the family Achatinidae, it was initially classified within the genus Achatina but has recently been relocated by molecular analysis to the genus Lissachatina [11]. Lissachatina fulica is used by humans for food, cosmetic purposes, and religious rituals [12].

The spread of L. fulica outside its native range by intentional (e.g., food, pets, etc.) or accidental (e.g., freight, etc.) transport began in the 1800s, when it was first introduced to Madagascar and Mauritius. It later arrived in India and spread from there to Asia and the Pacific Islands. In the 1900s, it was introduced to South America and the United States. It is now found in more than 50 countries throughout Africa, America, South and East Asia, and Oceania. It has occasionally been reported in the wild in Europe [5,9]. One specimen was found in July 2009 in Ve’ký Krtíš, Slovakia [13]. In October 2018, one live, one dead specimen, and shell fragments from a third specimen were found in Ferrara, Emilia-Romagna. Further surveys retrieved no other specimens [14]. In Spain, L. fulica is found in Andalusia, where its population evolution is being monitored [15].

Lissachatina fulica has been able to colonize the world by virtue of its biological and ecological characteristics: rapid population growth, hermaphroditism with self-fertilization, sexual maturity at 6 months of age, up to 400 eggs laid several times a year, polyphagous nature, resistance to drought conditions, adaptability to natural or urbanized environments, and absence of natural predators outside its native range [4,9,15]. Especially, the hermaphroditism of this animal, combined with its ability to reproduce without the presence of another individual (self-fertilization), greatly increases its ability to invade new areas [16]. Once this species is established, its containment and eradication are both complex and costly [17]. Its biological and ecological characteristics, together with its simplicity of rearing and low maintenance care, have made it a popular pet [18,19].

With this study, we report for the first time the finding of a specimen of L. fulica in a protected area of Piedmont (Avigliana Lakes Nature Park), northwest Italy.

2. Materials and Methods

2.1. Study Site

The Avigliana Lakes Nature Park (about 409 hectares in area), located at the entrance to the Susa Valley (northwest Italy; Figure 1a), is distinguished by a remarkable variety of landscapes: three different yet interconnected biotopes consisting of two lake basins, hills, and the Mareschi wetland. Both lakes (the Great Lake and the Small Lake) are of glacial origin (Figure 1).

The protected area is part of the European Natura 2000 network and is listed as a Site of Community Importance (SCI, IT1110007) according to the Habitats Directive (92/43/EEC) and as a Special Protection Area (SPA) according to the Directive on the Conservation of Wild Birds (2009/147/EC) [20,21,22]. Since 2012, it has been part of a network of protected areas in the Cottian Alps. The flora and fauna are typical of wetlands. The two lakes are Small Lake (60 hectares, 356 m.a.s.l.; Figure 1(b2,c2)) which empties into Great Lake (90 hectares, 352 m.a.s.l.; Figure 1(b1,c1)) and has preserved a natural forest environment, meadows, and reed beds.

The average annual temperature is about 10 °C, with maximum temperatures of 28 °C (July) and minimums of −1 °C (January). The area is characterized by a typical pre-alpine rainfall regime with peaks in late spring and late autumn. Overall, average annual precipitation ranges between 800 and 1200 mm (200–300 mm in summer).

2.2. Species Detection

One adult specimen of Lissachatina fulica was captured live by a park ranger in Avigliana on 9 September 2022, near the shore of the Great Lake (45°04′15.3″ N, 7°23′24.3″ E) (Figure 1 and Figure 2). The specimen was placed in a box and brought to the Regional Reference Center for the Biodiversity of Aquatic Environments (BioAqua) of the Veterinary Medical Research Institute for Piedmont, Liguria, and the Aosta Valley (IZSplv) for species identification, where it was photographed and measured for total length (mm) and total weight (g). The morphometric characteristics were recorded using a slide caliper (10 mm graduation), and the weight was measured using a precision balance (Figure 2). After the discovery, a systematic survey was organized on September 13 and 20 to identify any other individuals and/or signs of their presence (e.g., broken shells, etc.). Overall, the perimeter of Great Lake (about 4 km) was walked, and a linear transect (5 × 1 m) was made every 50 m, modifying O’Loughlin and Green’s method [23]. However, no other specimens and/or signs of their presence were found.

2.3. Molecular Analysis

A portion of the snail’s foot was sampled and preserved in ethanol for molecular species identification and confirmation of morphology. Genomic DNA was extracted using a commercial kit based on a silica gel column (ReliaPrep™ gDNA Tissue Miniprep System—Promega), according to the manufacturer’s instructions, and a part of the cytochrome oxidase subunit I (COI) gene was used as a mitochondrial genetic marker [25]. A fragment of ~650 bp was amplified using universal primers HC02198: 5′-TAAACTTCAGGGTGACCAAAAAATCA-3′ and LC01490: 5′-GGTCAACAAATCATAAAGATATTGG-3′ [25]. The PCR reaction was carried out in a final volume of 25 µL containing 12.5 µL FastStart™ PCR Master—Roche (2x), 0.375 µL of both primers (20 µM), and 1 µL of extracted DNA (~50 ng/µL). The PCR cycling conditions were as follows: initial denaturation step at 96 °C for 10′, 40 cycles of 94 °C for 30″, 49 °C for 30″, and 72 °C for 1′, and final extension at 72 °C for 5′. The fragment was sequenced on both strands using the same PCR oligonucleotides as sequencing primers on the ABI Prism 3130XL Genetic Analyzer (Applied Biosystems^TM, Waltham, MA, USA), and the consensus sequence was BLAST against the sequences in GenBank. Based on the validation of the method, only sequences with a similarity ≥98% were considered significant. Molecular Evolutionary Genetics Analysis software (MEGA; Version 7.0, Pennsylvania State University, University Park, PA, USA) with evolutionary distances was used via the maximum composite likelihood method. A bootstrap test of 1000 replicates was performed to test the result. The rosy wolfsnail (Euglandina rosea) sequence was used as the output group.

3. Results and Discussion

The classification of gastropods based on morphological and anatomical features is not always reliable [26]. The family Achatinidae is easily identifiable (i.e., wide and tall shells), although it presents classification problems due to major intraspecific morphological variation. Therefore, the subfamilies and genera have been extensively revised. Thus, the sample was subjected to molecular analysis [25].

Molecular analysis confirmed that the specimen belonged to the species Lissachatina fulica, with a similarity of 98.61% in GenBank, as we had hypothesized by morphological classification. The sample clustered in the phylogenetic tree with sequences belonging to L. fulica, separate from the other species of the same genus (Figure 3). Table 1 presents weight and morphometric parameters and a comparison with other findings.

The total shell length (102.5 mm) of our specimen was similar to that reported by Albuquerque and co-authors (102.5 mm; Brazil) [27] and Patiño-Montoya and co-authors (110.5 mm; Colombia) [28], whereas the weight (98.82 g) was greater compared to the weight of specimens that Okon and co-authors (59.58 ± 2.33 g) collected from a snail farm in Nigeria [29]. Previous studies reported that specimens did not vary in size, whether collected from small or large urbanized areas [30].

Table 1. Morphometric characteristics of the Giant African snail (Lissachatina fulica).

References	Present Study	[30] 1	[27]	[29] 2	[28]
Country	Italy	Thailand; Malaysia	Brazil	Nigeria	Colombia
Specimens	1	215	1460	100	106
Weight	98.82	-	-	59.58 ± 2.33	-
SL	102.5	78.34 ± 9.37	42.18 ± 69.08	67.86 ± 0.13	71.70 ± 17.90
SW	42.30	38.57 ± 3.71	-	26.61 ± 0.05	-
AL	53.00	38.15 ± 3.69	-	32.43 ± 0.08	-
AW	36.00	22.52 ± 1.86	-	10.61 ± 0.04	-
BWL	63.50	-	-	-	-
PWL	16.00	-	-	-	-
PWW	24.50	-	-	-	-
SpL	39.00	42.96 ± 6.42	-	-	-

The data are expressed in millimeters (morphometric characteristics) and grams (weight). SL denotes shell length; SW shell width; AL aperture length; AW aperture width; BWL body whorl length; PWL penultimate whorl length; PWW maximum penultimate whorl width; SpL spire height. ^1,2 Data are expressed as mean ± SE.

Table 1. Morphometric characteristics of the Giant African snail (Lissachatina fulica).

References	Present Study	[30] 1	[27]	[29] 2	[28]
Country	Italy	Thailand; Malaysia	Brazil	Nigeria	Colombia
Specimens	1	215	1460	100	106
Weight	98.82	-	-	59.58 ± 2.33	-
SL	102.5	78.34 ± 9.37	42.18 ± 69.08	67.86 ± 0.13	71.70 ± 17.90
SW	42.30	38.57 ± 3.71	-	26.61 ± 0.05	-
AL	53.00	38.15 ± 3.69	-	32.43 ± 0.08	-
AW	36.00	22.52 ± 1.86	-	10.61 ± 0.04	-
BWL	63.50	-	-	-	-
PWL	16.00	-	-	-	-
PWW	24.50	-	-	-	-
SpL	39.00	42.96 ± 6.42	-	-	-

The data are expressed in millimeters (morphometric characteristics) and grams (weight). SL denotes shell length; SW shell width; AL aperture length; AW aperture width; BWL body whorl length; PWL penultimate whorl length; PWW maximum penultimate whorl width; SpL spire height. ^1,2 Data are expressed as mean ± SE.

Human proximity seems beneficial to L. fulica, particularly the abundance of food in crop fields and/or garbage [4,9]. Albuquerque and co-authors reported that the size of L. fulica is influenced most by humidity and can support periods of drought by slowing growth and metabolic activity [28]. Lissachatina fulica can survive at temperatures between 0 °C and 45 °C due to aestivation and hibernation mechanisms. The ideal temperature for reproduction is in the range of 22 °C to 32 °C [31,32], which corresponds to typical summer temperatures in our study area. The specimen in the present study was found near the shore of the Great Lakes, not far (about 300 m) from an urban area with favorable characteristics for its establishment. Gutiérrez-Gregoric and co-authors [33] found a population of Giant African snails in the Argentinean Paranense rainforest, characterized by small settlements and protected areas, where the density of L. fulica was 107.6 snails/m² compared to 6 snails/m² of native gastropods. Such a high density poses a threat to both fauna and native flora. Lissachatina fulica has an extremely diverse diet, feeding on over 500 plant species, reducing the availability of food resources for native fauna and agriculture [9]. Rasal and co-authors studied the invasion of L. fulica in a protected forest with a semi-arid climate in western India (Ranthambhore National Park) and found that the population spread from hotel gardens and private homes starting in 2010, going on to invade the forest, although it was considered an unsuitable habitat [34].

Both highly adaptive and invasive, L. fulica is also distinguished by hermaphroditism, self-fertilization, and the large number of eggs it can produce (200–1800 eggs/year in ideal conditions) with a 90% survival rate of eggs [17]. Dickens and co-authors [16] conducted a laboratory experiment to evaluate the growth and reproduction rates of L. fulica (360 specimens). Over a period of 930 days, each snail produced an average of 4698 eggs, with a survival rate of 49% in the first 540 days after hatching. The high reproductive rate and the capacity for self-fertilization mean that even a single individual can start a new population, posing a potential threat to the biodiversity of the Avigliana Lakes Nature Park.

Eradication is successful only where populations are isolated and small. The main techniques to remove the species are baited gastropod traps and manual collection. Where these are unsuccessful or the costs are unsustainable, pesticides are often used [19]. Eradication by pesticides would be impractical in a protected area because it would endanger the area’s biodiversity. Eradication using biological control methods (predatory snails and flatworms) has had disastrous results, however, with the extinction of several native snails [35].

In addition to posing a threat to ecosystems and biodiversity, L. fulica poses a health risk to humans and wild and domestic animals wherever it is established. It is a vector for numerous parasites, including the nematode Angiostrongylus cantonensis, which causes eosinophilic meningoencephalitis in humans and canids. This parasite is transmitted primarily through the ingestion of mollusks infected with larvae or through contaminated food and water [6,9,36]. Several other parasites can be carried by L. fulica (Table S1, Supplementary Material). It can also be a vector of viruses, fungal, and bacterial microorganisms (i.e., Escherichia coli, Campylobacter spp.). Since few studies have been conducted to date [4,37], health monitoring of specimens kept as pets and those found in the wild is critical [19].

Except for the small population in Spain, reports of L. fulica in Europe are sporadic. They were probably kept as pets before being released into the wild. We hypothesize that this is what occurred with the L. fulica specimen in the present study due to its proximity to some houses in the urban area. Although there is no current Giant African snail emergency in Europe, precautionary and preventive measures should be taken nonetheless. EU Regulation No. 1143/2014 includes measures for preventing and containing the spread of invasive alien species, including restrictions on keeping, buying, selling, and releasing them in the wild. L. fulica is not included in this regulation or in the Union List of Invasive Alien Species; it can be purchased on the European market and is gaining popularity as a pet [38].

The fact that the regulation does not include gastropods or other mollusks is a matter of debate within the scientific community. Bohatà and Patoka recently suggested that certain gastropod species, including L. fulica, should be included in the Union list [7]. This suggestion was prompted by the scarcity of data about the pet trade, taxonomic uncertainty, and increased likelihood of invasion due to climate change. Since L. fulica does not currently pose a potential risk for all European Union Member States, some authors have proposed its inclusion at least in lists of national relevance so that action can be taken by the states most at risk, such as the Mediterranean countries [39]. Indeed, Bohatà and Patoka [7] predicted the possible future establishment of L. fulica in a restricted area of Europe (i.e., the Canary Islands and Azores) through the MaxEnt program (based on the Maximum-Entropy approach for modeling species niches and distributions) in the context of climate change.

4. Conclusions

Monitoring the health situation and the distribution of Lissachatina fulica is warranted in Europe and especially in protected areas, such as the Avigliana Lakes Nature Park, in view of climate change, which could expand the distribution range of this species [7,40]. In addition, it is essential to move the discussion to legislative and regulation and to inform buyers and owners about the potential risks of releasing L. fulica, into the wild. Among the four fundamental principles for proper management of alien species (prevention, early detection, eradication, control), the most important is certainly prevention [41]. Given the ecology of the species, a single individual makes both reporting and management intervention necessary. Thus, new surveys should be planned, using Citizen Science as well, to raise awareness of invasive alien species (IAS).