Influence of reproductive history of parents on meristic variation in offspring in the cyprinodont fish Rivulus marmoratus

Parent fish from one clone of the self-fertilizing cyprinodont fish Rivulus marmoratus were held under constant conditions, and their offspring were examined for meristic variation associated with their position in the oviposition sequence of parents. In all meristic series counted (vertebrae, and anal, dorsal, pectoral, and caudal fin rays) those offspring produced soon after their parents had begun to lay eggs tended to have fewer parts than did those produced longer after the onset of oviposition. Most meristic differences were due to the low counts produced in embryos laid within 8 days of first oviposition; counts differed little among embryos laid at averages of 22, 86, and 158 days after first oviposition. Differences were most significant for dorsal and anal rays and not significant for caudal rays.