The developmental biology of annual fishes. III. Pre-embryonic and embryonic diapause of variable duration in the eggs of annual fishes

摘要: Annual fishes can maintain permanent populations in temporary aquatic habitats since the population survives dry seasons form of diapausing eggs. Populations persist even though subject to erratic environmental cycles and recurrent ecological catastrophes. Developmental arrest occurs at one or all following stages: Diapause I (Dispersed cell phase); II (Long somite embryo); III (Prehatching). In Austrofundulus, is facultative. are obligate, long variable (105 ± 20 days each). Subpopulations (about 10%) “escape eggs” bypass and/or III. Pterolebias Rachovia eggs behave much like those Austrofundulus. Rachovia, duration 80 33 least 61 23 days. present. Cynolebias Nothobranchius undergo facultative enter obligate species Aphyosemion II, an A few may also experience II. short term phenomenon, “retarded hatching,” sometimes encountered among non-annual Aphyosemions other cyprinodonts. Survival strategy based on “multiplier effect”; i.e., interposition into developmental pathway three branch points containing diapause stages prolonged, generates eight different distributions total time. Thus, a single egg identical age generate several subpopulations, which develop according schedules. program established permits repeated loss individual under conditions initiate hatching but do not allow for maturation successful reproduction. The effect” augmented by adaptations guarantees that some portion will survive reproduce.