MORPHOLOGICAL, ALLOZYMIC, AND KARYOTYPIC DISTINCTIONS BETWEEN NERITINA-(DOSTIA)-VIOLACEA AND N-(D)-CORNUCOPIA (GASTROPODA, NERITOIDEA)

Two species of mangrove gastropod, Neritina (Dosria) violacea Gmelin, 1791 and N. (D.) cornucopia Benson, 1836, from Hong Kong have been com pared morphologically, allozymically, and karyotypically. The two can be identified by differences in shell pigmentation patterns, ventral s hell characters, and radular teeth characters. Allozymic variations at 15 presumptive gene loci were examined. Average heterozygosities were 0.058 in local populations of N. (D.) violacea and 0.138 in N. (D.) c ornucopia. Six enzyme encoding loci were typically diagnostic for indi viduals of each species and no hybrid patterns have been recorded. Nei 's standard genetic distance and genetic identity between the two spec ies were estimated to be 0.814 and 0.443, respectively. Karyotypic inv estigations have revealed that both species are diplonts, with two X-c hromosomes in females and one in males. Diploid numbers are 2n = 20 XX (or XO) for N. (D.) violacea and 2n = 26 + XX (or XO) for N. (D.) c ornucopia.