Biological aspect of Deroceras reticulatum (Müllcr, 1774)(Pulmonata: Stylommatophora) in experimental conditions.

Abstract

Crop managcment practiccs  can have a deep influence on the biological community of agricultura! systcms. Conservation-tillage practices disturb thc soil only cnough to insert thc secds, and a variety of studies  documcnted that conservation-tillage results in more substancial lcaf littcr and large wced community, and tend to host more diverse comrnunities of soil  organisms. However,  most dangerous species of slugs, as Deroceras  reticulatum, are epigea! herbivores that inhabit the soil surface, and have been cited causing  damages on severa) crops. Since 1997, it was found in southeast Buenos Aires province,  Argentina,  on sunflower  under not tillage systems.  An assumption of our experiment is that Deroceras populations in South America may be genetically  distinct  because of ditferences in climate or colonization histories. The objective of this study was to determine the growth  curve, reproduction, longevity, and survival of D. reticulatum, under controlled laboratory conditions at  12 ºC and 18 ºC. The  experience was initiated at each temperature with 20 recently bom slugs. lndividuals were kept in 385 cm3 plastic boxes each and  food  consisted of leaves  of lettuce  Lactuca saliva L.). The  length  of each slug, mortality, egg-laying, and food ea ten by each individual on the leaf of lettuce were registered weekly. Three  phases  of development were identified: the 1 SI one was of fast growth, the 2"d one of slower growth, and the 3'd one with absence of growth at 18ºC and scarce growth at 12 ºC. Second phase was longer at 12 ºC. At 12 ºC, eggs were observed from 3rd phase  of development whereas no egg-laying was  recorded  at  18 ºC.  Although  average longevity  was  not  significantly   different  in both  temperatures, longevity  was greater  at  12 ºC  with 221,2  days  than at  18 ºC  with 192,8 days. The  survival  was not significantly ditferent with  both temperatures and the relanon between  total longevity and average longevity  was 1,48: 1 (at  12ºC)  and  1,81: 1 (at  18 ºC). Considering both temperatures studied, 12ºC resulted the most  appropriate temperature for development of the population. The size of D. reticulatum was related  with the diameter of the perforations in .ne Jettuce leaf;  individuals  smaller  than I   cm caused a frayed  on the  leaves, those  specimens  of 1 to 3 cm long made perforations between 2 and 6 mm diameter, and those ones  longer than 3 cm have done great  rPrforations  on the leaves.