MATURATION OF THE REPRODUCTIVE TRACT OF NEOHELIX MAJOR (BINNEY) (GASTROPODA: POLYGYRIDAE) MARIA GABRIELA CUEZZO FACULTADDE CIENCIAS NATURALES E INSTITUTO MIGUEL LlLLO , UNIVERSIDAD NACIONAL DE TUCUMAN, MIGUEL LlLLO 205 , (4000) SAN MIGUEL DE TUCUMAN, ARGENTINA ABSTRACT Maturation of the reproductive system of Neohelix major (Binney), from post-hatching through sexual maturity, was examined. Laboratory reared snails were used throughout this study so that ages of animals were known. Snails were sampled every 30 days starting at one month and continuing through 14 months of age. The ovotestis, hermaphroditic duct, albumen gland, spermoviduct and terminal genitalia (free oviduct, vas deferens, vagina, penis and bursa copulatrix) were examined histologically. Considerable intraspecific variation exists in the structural development of the reproductive tract of Neohelix major even among animals of the same age. Within the same adult age class, animals with shells in good condition showed uniformity in development but individuals with damaged shells were variable and always immature.There is a relationship between st)ell diameter and degree of maturity reached by the reproductive tract. Snails four months old contained spermatogonia and spermatocytes, but mature spermatozoa did not appear until the snails were nine months old. Oocytes were present from the first month although the largest appeared at 12 months of age. Until eight months of age the reproductive tract appeared immature and male organs were more evident. At nine months old, all organs, especially those of the female, increased in size and became more voluminous. The male system completed maturation slightly earlier than did the femalé system. Maturity is reached for most of the animals between 10 to 12 months of age when the ovotestis already contains spermatozoa. The reproductive anatomy of several Triodopsinae has been studied by Simpson (1901), Pilsbry (1940) and Ember- ton (1988). Although the biology of Neohelix major (Binney) has been studied by Vail (1978) during two consecutive reproductive seasons, details of the changes in the reproduc- tive system from hatching to sexual maturation are not yet available for this species. In contrast, detailed descriptions are available for Arion ater rufus Linné based on material reared in the laboratory (Lusis, 1961) and collected from the field (Smith, 1966), and also for Agriolimax reticulatus (Muller) (Runham and Laryea, 1968; Runham, 1978). Other authors have described various aspects of maturation of the reproductive tract and suggested the possibility of controlling.factors. Laviolette (1954) described the role of the gonad in the maturation of the reproduetive tract in the Arionidae suggesting hormonal control. Smith (1966) found a close relationship between maturation and seasons, and later (1967) investigated the relationship between neurosecretory activity and maturation. This paper describes diHerent stages in the matura- tion of the reproductive tract of the polygyrid gastropod Neohelix major, from recently hatched snails to maturity. MATERIALS AND METHODS This study was based upon snails reared in the laboratory by Dr. Virginia Vail. The parental stock comprising 21 mature specimens came from Greenwood Plantation, near Thomasville, Thomas County, Georgia, U.S.A. Snails were maintained under laboratory conditions over two consecutive reproductive seasons. Vail made observations on the eggs and young (Vail, 1978), and fixed snails of known ages dur- ing the summer season (June-July) so it was possible to com- pare not only animals of different ages but also individuals of the same age. Following a baseline study of these pre- served snails, animals of known ages were sampled every 30 days, starting at one month and continuing until14 months of age. Generally, each sample consisted of five to seven snails but some critical ages necessitated analysis of more snails. Individuals of each age-class belonged to the same clutch of eggs. Before dissecting the animals, shell diameter and shell height were measured. Snails of each sample were dissected and ovotestis, hermaphroditic duet, albumen gland, spermoviduct, free American Malacological Bulletin, Vol. 8(1) (1990):19-24 19