Distribution of Deroceras reticulatum ( Müller , 1774 ) ( Pulmonata Stylommatophora ) in Argentina with first record of the Reserva de Usos Múltiples

Deroceras reticulatum is a misanthropic European species spread widely throughout South America. At the moment this species is considered a ‘pest’ in direct sowing such as maize, soybean, sunflower, wheat, alfalfa and clovers, among others. The aim of this paper is to report the first record of D. reticulatum in the Reserva de Usos Multiples Isla Martín García, Buenos Aires province and to provide information about this species distribution in five Argentina provinces.


Description of D. reticulatum (Figure 1)
Terrestrial gastropod with an internal shell.General body coloration is whitish gray.The pneumostom, with whitish border, is at the mantle anterior section.In the ventral region of the body, the whitish foot is observed.Mucus is aqueous and clear.The dorsal surface of the mantle presents protuberances giving the surface a wrinkled appearance.The penis sack is conspicuously developed in the anterior body region (Total length: 3 mm).The intestinal caecum: (Total length:1.25 mm).
Total length of examined specimens ranged from 20 to 60 mm.According to Vera-Ardilla and Linares (2005), juvenile specimens are 16 to 17 mm and adults are 35 to 40 mm in size.1998).Rambo et al. (1997) and Maurer et al. (2002) reported cases of abdominal angiostrongylosis in southern Brazil (Santa Catarina).Several records of this disease were reported from Brazilian localities along the Uruguay river basin, which borders with the Argentinean province of Corrientes, though all the cases correspond to transmitter gastropods from the Veronicellidae family (Rea and Borda, 2001;2002;Fleitas et al., 2005).The nematode A. cantonensis causes eosinophilic meningoencephalitis in humans and the first reported case in the Western Hemisphere was in Cuba (Aguiar et al., 1981).Nowadays the disease has expanded to other tropical and subtropical countries of America (Dorta Contreras, 2007).These introduced mollusks are also responsible for economic damage to agriculture and are disseminated inadvertently by seeds, harvest, fruits and farm machinery.Hausdorf (2002) considers the species from the Agriolimacidae family a "pest" to commercial field crops.The aim of this paper is to report the first record of D. reticulatum in the Reserva de Usos Multiples Isla Martín García, province of Buenos Aires and to provide information on the distribution of this species in Argentina.

Sampling site
Martín García Island is located in the Upper Rio de la Plata, south of the mouth of the Uruguay river (34° 11' 25" S and 58° 15' 38 W).This island is an outcrop of the crystalline basement, unconformably overlain by Pleistocene and Holocene sediments (Ravizza, 1984).The particular geographical location of this multiple-use Nature Reserve and the possibility of exploitation for touristic purposes make the island an important study object.

Material
Sampling was conducted in August of 2006 and in December of 2007.Fourteen specimens were collected under rocks, four were captured along the quarry side of Cantera Grande, a pond near the island harbour (MLP Nº12536) and ten were collected in the surrounding gardens (MLP Nº 12821).
The geographical distribution of D. reticulatum in Argentina was based on the author's collections which were deposited in La Plata Museum of Natural Science (MLP), from the MLP Molluscan Collection and literature references.
The specimens were relaxed in the laboratory with menthol and then fixed in Carnoy.Total length of specimens was measured from the cephalic region to the posterior region of the body using a Vernier caliper (0.02 mm).Dissections were done under binocular stereomicroscope PZO at 10 × using the Wiktor (2000) technique.several biological parameters that favour the presence of D. reticulatum and other species of slugs and insects.Direct sowing modifies the population dynamics of pests and their natural enemies, selecting populations of organisms that adapt themselves to the new management conditions (Aragón, 1997).According to Hammond (1998), stubble causes an increase in moisture retention in soil and a decrease in the soil temperature, giving appropriate conditions for the development of gastropod populations.Among these gastropods, D. reticulatum is considered the most damaging species.
In recent years, the presence of other invading pulmonates has been reported in diverse geographical points of South America, as is the case of two slugs of European origin, Arion intermedius Normand, 1852 and Tandonia sowerbyi (Férussac, 1823) in Chile (Cádiz and Gallardo, 2008), which are considered nowadays to be agricultural plagues.
Another case is that of Achatina fulica Bowdich, 1822, which is a terrestrial-invading gastropod, native to Africa and a potential rival of native mollusks, an agricultural pest and intermediary host of A. cantonenesis, which causes eosinophilic meningoencephalitis, a disease that has already been registered in human populations in Brazil (Colley, 2008;Lima-Caldeira et al., 2008).
While no records of D. reticulatum are currently available for Isla Martín García, it is likely that the species introduction dates back to the end of the nineteenth century and the beginning of the twentieth concomitant to the settlement of the stable population (Kropfl, 2006).Since then, this process has continued due to the arrival of vegetables for both the stable and tourist population consumption.
To date, no studies have been carried out on the impact caused by D. reticulatum on the native flora of the Reserve, where different biological types occur: herbs, bushes, trees, climbing plants, ferns and lianas (Lahitte et al., 1996).
As mentioned above, species of Agriolimacidae such as D. reticulatum and D. laeve are intermediate hosts of the nematodes A. costaricensis and A. cantonensis which have Sigmodontinae rodents as definitive hosts, and humans, particularly infants, as accidental hosts.To date, no helminthological prospection has been performed on slugs from the Reserva Isla Martín García.Future research should be done on this subject since, simultaneously, the presence of a sigmodontine species has been detected, Oligoryzomys delticola (Thomas, 1917) (Udrizar-Sauthier et al., 2005), which would enter the life cycle of these parasites.From this, it could be inferred that if these slugs were infected, both the adult and infant population would be at risk of infection, given that the spread of these gastropods around the scarce 185 ha of the island is highly feasible.

Discussion and Conclusion
The presence of D. reticulatum in Argentina dates back to 1875.It has been widely distributed throughout the national territory for 133 years.A slow increase in the number of this species and other slugs was observed in direct sowing plots of Cordoba and Santa Fe provinces and to the southeast of Buenos Aires province.In general, slugs damage several crops such as maize, soybean, sunflower, wheat, alfalfa and clover in the early vegetative stages (Aragón, 1997;Clemente, 2003).Direct sowing is a management practice which has spread throughout the main agricultural areas of Argentina due to its multiple benefits and advantages compared with other cropping systems.This method is widely used because the presence of plant residues and soil stability change the physico-chemical characteristics of the soil and of 2) Sierras de Córdoba; 3) Cantera Grande and sourrounding gardens; 4) Balcarce; 5) Sauce Corto; 6) Coronel Gómez, 7) Isla Victoria; 8) El Bolsón; 9) Potrero Cerrado and Arroyo Aguanda; 10) Cancha Carrera; 11) Río Turbio; 12) Lago Morales.