Terrestrial gastropods as Fragaria x ananassa pests in southern Brazil : morphological identification

Considering the damage caused by terrestrial gastropods in strawberry producing areas in southern Brazil, this study aimed to i) identify the species associated with Fragaria x ananassa in rural properties in municipalities of Paraná State, Brazil; ii) describe and illustrate the diagnostic morphological and conchology features of the mollusk species; iii) construct an illustrated key based on these morphological and conchology features; iv) analyze two species collected in March 2017 to investigate the possible occurrence of parasitic nematodes of medical importance. Taxonomic determination of the mollusks was performed through morphological analysis of samples, and parasitological analysis was carried out using artificial digestion. The following gastropod species were identified: Bradybaena similaris (Bradybaenidae), Rumina decollata (Subulinidae), Deroceras leave (Agriolimacidae), Limacus flavus (Limacidae), and Meghimatium pictum (Philomycidae). Rumina decollata, L. flavus,and M. pictum were recorded for the first time as damaging strawberries in Brazil. No larvae of medical or veterinary importance, associated with samples, were reported. The main diagnostic features are described and illustrated. Besides, the potential of the gastropods as crop pests and vectors of nematodes associated with zoonotic diseases are discussed. Results can facilitate identification of gastropod species in strawberry crops and provide background information for future studies on bioecology and pest control.


INTRODUCTION
Gastropoda is the largest class concerning diversity within the phylum Mollusca, with over 100 thousand species described, representing about 80% of all known mollusk species (HASZPRUNAR et al., 2008).Besides acting as intermediate hosts of helminths that can affect human health, their natural and mainly anthropogenic dispersal causes some species to affect the economy, society, environment, and agriculture (GRISOTTI & ÁVILA-PIRES, 2011).

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Duch) crops are one of the most affected by pests, where one of the main problems has been the diversity of species that can affect production.In recent years, an increase in mollusk infestation has been observed in strawberries from crops in southern Brazil (ZAWADNEAK et al., 2014).Use of mulching techniques and drip irrigation create favorable conditions for the survival of the mollusks since these organisms prefer dark and humid environments, in addition to the constant food availability.Mollusks can attack not only leaves, which compromises plant development but also fruits, by opening galleries that can serve as a doorway to other pests and diseases (ZAWADNEAK et al., 2014;SOUZA & ZAWADNEAK, 2018).Another critical damage; although indirect, is caused by the presence of slime (mucus), which depreciates the fruits by affecting market value.Consequently, income generation for strawberry farmers in the Paraná State and other regions infested by mollusks has been jeopardized (SOUZA & ZAWADNEAK, 2018).
Mollusks presence in crops may also raise public health issues since several species can be naturally infected with helminths causing human diseases, such as Angiostrongylus costaricensis (Moreira & Céspedes, 1971), which causes abdominal angiostrongyliasis, and Angiostrongylus cantonensis (Chen, 1935), which is the etiological agent of eosinophilic meningitis (OHLWEILER et al., 2010).Human beings are accidental hosts in the life cycle of these helminths, and contamination usually occurs due to ingestion of raw mollusks or unwashed foods contaminated with third-stage larvae, which are present in the mollusk slime (BONETTI & GRAEFF-TEIXEIRA, 1998).
In this context, this study aimed to i) identify the species associated with Fragaria x ananassa in rural properties in municipalities of Paraná State, Brazil; ii) describe and illustrate the diagnostic morphological and conchology features of mollusk species; iii) construct an illustrated key based on these morphological and conchological features; and iv) analyze two species collected in March 2017 to investigate the possible occurrence of parasitic nematodes of medical importance.

MATERIALS AND METHODS
Mollusks analyzed in this study were obtained from the collection of the Laboratório de Entomologia Prof. Costa Lima, Curitiba, Brazil.The collection was created to receive specimens of qualitative sampling of the "Produção Integrada do Morango PR" project, from commercial strawberry crops in rural properties located in the municipalities of Pinhalão, São José dos Pinhais, and Quatro Barras in Paraná State, southern Brazil.Specimens were collected during three years (2015)(2016)(2017).
Fixation of specimens followed the distension technique described by THOMÉ (1975).Individuals were submerged in water in a closed container and kept refrigerated at 6°C for 24 hours and subsequently transferred to 70% ethanol.Species identification was based on dissection of five specimens per each morphotype found.They were dissected under a stereomicroscope for analyzing the external morphological features and genitalia, which were further compared with specialized literature (GODAN, 1983;ARAÚJO, 1989;THOMÉ et al., 1996;BARKER, 1999;SCHILEYKO, 1999;OHLWEILER et al., 2010).The family names follow BOUCHET et al. (2005).
Twelve specimens were collected in March 2017 in the strawberry crops.They were analyzed for parasites using the artificial digestion method modified from WALLACE & ROSEN (1969), with six specimens of L. flavus from Quatro Barras (n=3) and São José dos Pinhais (n=3), and six specimens of M. pictum from São José dos Pinhais.Artificial digestion was carried out at the Laboratório de Referência Nacional para Esquistossomose-Malacologia (LRNEM), Instituto Oswaldo Cruz (IOC), Brazil.
Meghimatium pictum (Figure 1A) -body up to 6cm long and 1.5cm wide (GOMES et al., 2011).Mantle whole, body tapering posteriorly; keel absent.Shell sac present but shell absent.In dorsal view, body with a brown, medial longitudinal stripe and two stripes along the dorsum, on a light beige background.Small, oval gray spots present dorsally between stripes and laterally on the body.The respiratory pore is a short slit near anterior right mantle edge.Pale-colored foot covers the entire length of the body.Upper tentacles grayish.
Meghimatium pictum has been reported as causing damage to vines (Vitis labrusca) in southern Brazil (BARONIO et al., 2014) The species has also recently been associated with the transmission of abdominal angiostrongyliasis in humans in the Rio Grande do Sul State (RODRIGUEZ et al., 2018).These authors also associated the risk of infection with grape consumption in areas where the M. pictum is a pest, showing the importance of its appropriate management in the field to reduce the contamination risk of strawberry farmers.According to BARONIO et al. (2014), this species is not able to perforate the surface of grapes but takes advantage of existing damage to reach and feed on grape pulp.This is not true for strawberries since there is no protective exocarp skin; and therefore, it is easier for the mollusks to feed on them.
Bradybaena similaris (Figure 1B) -small snail, the shell up to 1.5cm in diameter.Body light to dark beige.Tentacles darkened.Dorsal surface of upper tentacles usually with a dark stripe that extends through the head.Heliciform shell with five to six whorls and, opened and not deep umbilicus, with a semilunar aperture (ARAÚJO, 1989), partially covered by the extremity of the columella.Color varying from yellowish to brown, sometimes with a reddish-brown band along sutures and the last whorl through the aperture.The reproductive system in this species present a single dart sac with two multifidus glands connected to it, an oval bursa copulatrix with a very long and narrow duct, and a cylindric, muscular and smooth phallus involved by a muscular sheath with an epiphallus (THOMÉ et al., 1996).
Rumina decollata (Figure 1C) -has a shell is turriculated, longitudinally striated with irregular elevated lines and wrinkles.It is a decollated shell, which is a shell with a broken apex.Commonly with four whorls and three cm in height, although variations are also known (BATTS, 1957;PRÉVOT et al., 2015).Penis elongate, with characteristic internal coiling folds.It is also possible to notice the slit-like opening of the vas deferens, which is delimited by denser tissue.Opposite to this opening, there is a conspicuous glandular area.Vagina wide and short.Bursa copulatrix with short, narrow duct and welldeveloped sac (SCHILEYKO, 1999).Rumina decollata has an omnivorous feeding habit (plants, eggs, worms) (REYNA & GORDILLO, 2018) and may be cannibalistic or prey on other mollusks (CARDILLO et al., 2016).This predatory habit led to its introduction to California (USA) as a biological control agent against Cornu aspersum (Müller, 1774) (FISHER, 1966;COWIE, 2001;CARDILLO, et al., 2014) and later to Argentina, in 1988, with the same purpose (DE FRANCESCO & LAGIGLIA, 2007;CARDILLO et , 2013).This is the first report of R. decollata damaging strawberry plants on the Paraná state.Considering its ability to rapidly spread and deleteriously impact the native biota, commerce, and health of pets and humans, monitoring its distribution and implementing early control efforts is warranted (REYNA & GORDILLO, 2018).Deroceras laeve (Figure 1D) -small slug, body length about 2.5cm, anterior part of the mantle delimiting the area where the vestigial internal shell is located.This area reaches approximately the medial part of the body.The specimens observed were medium brown, with the foot pale brown; although, color can vary to light brown or grayish.Short keel in the dorsal posterior portion of the body.Mucus secretion transparent.Pneumostome in the postmedial region.Penis long, sinuous, with an appendage, proximal area with several small papillae more or less differentiated, the phallus glands, distally with a small internal stimulator which can be hemispheric or conical (BARKER, 1999;FORSYTH, 2004).Bursa copulatrix oval to globular, with a duct slightly longer than the bursa itself.
Deroceras laeve has been recorded in vegetable gardens, home gardens, and crops, and is often reported on horticultural products like spinach, beet, broccoli, kale, cabbage, mustard, arugula, and lettuce (MAURER et al., 2002;BRUSCHI-FIGUEIRÓ & VEITENHEUIMER-MENDES, 2002).An epidemiologic study in Nova Itaberaba, Santa Catarina State, Brazil, reported D. leave for the first time as host of A. costaricensis (MAURER et al., 2002).Those authors mentioned that this small slug is frequently reported on folds of leafy vegetables and thus could transmit the parasite to human beings if ingested accidentally.
Limacus flavus (Figure 1E) -slug up to 12cm in length (BARKER, 1999), with yellowish body with green spots.Spots can be sparse or cover most part of the body, giving a more uniform greenish color to the body.The first third is marked by the mantle shield, which delimits the area where the reduced internal nail-shaped shell.A white medial line starting on the second third of the body is present.Head pale, without spots, upper tentacles grayish blue.Foot is yellowish white.Mucus secretion yellowish.Bursa copulatrix constituted by a short duct and a small and oval sac.Atrium and vagina are very short.Penis is long, narrow, cylindrical, variably coiled or folded.Vas deferens is short and penetrates the phallus adjacent to phallus retractor muscle.Prostatic gland is very slender and not connected to oviduct at its begining.
The information about mollusk species associated with crops and terrestrial mollusks, in general, is scarce in Brazil (SANTOS et al., 2009).We identified here five species associated with strawberry crops.Further studies on morphology, biology, and physiology are necessary to develop adequate management methods for controlling these pests (THOMÉ et al., 2006).

CONCLUSION
Terrestrial gastropods M. pictum, L. flavus and R. decolata were recorded for the first time damaging Fragaria x ananassa in rural properties in Paraná State, Brazil.Species identification can be performed using morphological and conchology features.Although, no larvae of medical or veterinary importance were detected in the analyzed samples, the consumption of fresh strawberries in natura and the presence of these gastropods in crops may increase the transmission risk of zoonoses.
(CARDILLO et al., 2014)es in Argentina indicated that R. decollata is host to several parasitic nematodes like Toxocara cati Schrank, 1788, which may parasitize human beings(CARDILLO et al., 2016), as well as Aelurostrongylus abstrusus (Railliet, 1898), which affects the respiratory system of cats(CARDILLO et al., 2014).Besides, this species is considered pest of crops and horticulture (REYNA & GORDILLO, 2018).In Brazil, R. decollata has been recorded on states of São Paulo, Santa Catarina, Rio Grande do Sul and recently also on the Minas Gerais (OLIVEIRA & ABREU