Reference : Biol Bull., 142: 36-48. (February, 1972) REGIONAL SURVEY OF GENE FREQUENCIES IN THE MUD SNAIL NASSARIUS OBSOLETUS JAMES L. GOOCH 1 , B. S. SMITH AND DONNA KNUPP Department of Biology, Juniata College, Huntingdon, Pennsylvania 16652, and Department of Zoology, University of Reading, Reading, England One of the most abundant species of the littoral and estuarine environments of the Atlantic coast of the United States is the mud snail, Nassarius obsolctus. Adult snails are deposit feeders and scavengers occurring in large numbers on organic-rich intertidal flats from the Gulf of St. Lawrence in Canada to northern Florida (Scheltema, 1964). Nassarius obsoletus is an active species with a keen olfactory sense (Carr, 1967; Schaefer, 1969) and a tendency toward aggregative and schooling behavior (Jenner, 1956, 1957, 1958, 1959; Crisp. 1969). Dispersal is primarily by means of a planktonic larva (Scheltema, 1961, 1962). Recently techniques combining zone electrophoresis and staining for specific proteins that are distinguishable as the products of individual gene loci have be-gun to contribute to the understanding of genetic systems of marine invertebrates (Manwell and Baker, 1970; Milkman and Beaty, 1970; Selander, Yang, Lewontin, and Johnson, 1970; Gooch and Schopf, 1970, 1971; Schopf and Gooch, 1971). Electrophoresis and chromatography have had prior application in the genus Nassarius. Interspecific differences occur in protein patterns of chromatograms of British Nassarius (Collyer, 1961). Isozyme patterns of malate dehydrogenase in adult snails were studied by Meizel and Markert (1967), and electrophoretic activities of several enzymes in embryos and larvae were reported by Goldberg and Gather (1963) and" Merrill and Norris (1965). We report here the results of a study of the electrophoresis genetics of N. obsolctus which was begun with a twofold goal: (1) to discover and char-acterize gene loci from the pattern of their protein products on gels, and (2) to survey populations along a long coastal transect for geographic variation in the sampled portion of the genome. MATERIALS AND METHODS Eleven collections of N. obsoletus, of 30 to 184 snails each, were made from January, 1969 to August, 1970 along a 1000 km Atlantic coast transect (Fig. 1). The transect ranges from Cape Cod Bay, Massachusetts, to near Beaufort, North Carolina, and embraces part or all of 3 zoogeographic provinces, the Acadian (1 collection), the Virginian (8), and the Carolinian (2). Sampled populations represent a diversity of habitats : the sandy sublittoral (Cape Henlopen, Delaware), a salt marsh tidal creek (Canary Creek Marsh, 1 Present address : Department of Biology, University of Chicago, Chicago, Illinois 60637. 36
BioStor
