File:American malacological bulletin (1988) (18130015146).jpg

Title: American malacological bulletin
Identifier: americanmal6719881990amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
8 AMER. MALAC. BULL. 7(1) (1989) determine the extent of genetic substructure as well as the effects of possible self-fertilization on heterozygosity, allozymic variation, and phenotypic variation of shells. MATERIALS AND METHODS ELECTROPHORETIC METHODS Standard procedures of horizontal starch gel elec- trophoresis were followed (Selander era/., 1971; Hillis, 1985). Digestive glands of Liguus fasciatus were ground and diluted 1:1 in 0.01 M tris-0.001 M EDTA-.001 M 2-mercaptoethanol, pH 7.5. Homogenates were centrifuged at 7,000 g for 5 min, after which the supernatants were refrozen at -85°C. A buffer system of 175 mM tris-17.5 mM boric acid-2.75 mM EDTA, pH 9.1 was used. Gels were prepared from 50% Sigma starch (lot 85F-0010) and 50% Otto Hitler electrostarch (lot 392). Gels were electrophoresed for 12 hr at 12.5 V/cm. Histochemical staining for glucose-phosphate isomerase (E.C. 5.3.1.9; GPI) followed Harris and Hopkinson (1976). This enzyme was the only variable locus of the 24 allozyme loci surveyed in L. fasciatus by Hillis ef al. (1987). BREEDING STUDY Between 18 January and 5 July 1986, 60 specimens of Liguus fasciatus were collected from hammocks in the Pinecrest region, Big Cypress National Preserve, and near Long Pine Key, Everglades National Park, Florida, for cap- tive breeding experiments. Mating in this species begins in late July or early August in these regions (Jones, 1954). Pairs of L. fasciatus remain together for several days after mating, so the beginning of the breeding season can be easily ascer- tained. In summer 1986, the study populations were observed at least twice weekly, and the first mated pairs were found during the first week of August. Therefore, all of the specimens used in the captive breeding study were collected at least one month prior to the breeding season. Specimens from single populations were paired at random and kept in isolation in plastic boxes (10 cm x 20 cm x 30 cm) with 3-4 cm of decayed leaves and hammock soil. Snails were fed with lichen-covered branches supplemented with a mixture of cornstarch, oatmeal, spinach, vitamins, and calcium carbonate. Snails were main- tained at approximately 25°C, and were sprayed with water 5 times per week until eggs were deposited (24 Sept - 5 Oct). During egg deposition, the egg-producing individuals were marked. After eggs had been deposited, cages were sprayed with water at approximately two week intervals until hatching occurred (Jan - Feb 1987). Parental snails and offspring were then examined for variation at the glucose-phosphate isomerase locus as described above. FIELD STUDY The study site was located near Pinecrest, Big Cypress National Preserve, Monroe County, Florida. Pinecrest ham- mocks (PC) 16 and 16a (numbering system follows Pilsbry, 1946) were separated by a narrow channel of water until the 1960's or 1970's (Hillis ef al., 1987; Fig. 1). Prior to connec- tion of these hammocks, Liguus fasciatus in PC 16 were of PC I6 PC l6o
Text Appearing After Image:
0 40 80 I20 I60 200 240 Meiers along transect Fig. 1. A. Map of Pinecrest hammocks 16 and 16a, showing loca- tion of transect. The shading around the hammocks represents the approximate extent of recent woody growth that is seasonally flood- ed. This growth provides a connection between the hammocks for movement of Liguus fasciatus. B. Shell phenotypes of L. fasciatus collected in corresponding sections of the transect shown in A. The darkly shaded portion of the histogram represents the percentage of the barbouri phenotype, the lightly shaded portion the aurantius phenotype, and the white portion the walkeri phenotype. C. GPI allelic frequencies of L. fasciatus collected in corresponding sections of the transect shown in A. The darkly shaded portion of the histogram represents the percentage of the F allele in the sample, and the white portion the percentage of the S allele. the walkeri phenotype (banded shells with pink tips), whereas L. fasciatus in PC 16a were of the barbouri phenotype (dark snails with white tips); a third phenotype, aurantius (orange snails), was uncommon in both hammocks (Hillis ef al., 1987). Fire prevention in the Pinecrest area over the past several decades has resulted in increased woody growth around many hammocks, and by the 1960's or early 1970's tree growth (primary willows) had joined the two hammocks suffi- ciently for movement of Liguus between PC 16 and PC 16a (Fig. 1A). Because the two populations are also strongly dif- ferentiated at the glucose-phosphate isomerase locus, this site provided an opportunity to study the effects of self- fertilization on the interaction of differentiated populations of L. fasciastus. A transect was constructed perpendicular to the axis of the contact through the two hammocks (Fig. 1). Fourteen

Note About Images