Abstract
Embryo–environment interactions are of paramount importance during the development of all organisms, and impacts during this period can echo far into later stages of ontogeny. African annual fish of the genus Nothobranchius live in temporary pools and their eggs survive the dry season in the dry bottom substrate of the pools by entering a facultative developmental arrest termed diapause. Uniquely among animals, the embryos (encased in eggs) may enter diapause at three different developmental stages. Such a system allows for the potential to employ different regulation mechanisms for each diapause. We sampled multiple Nothobranchius embryo banks across the progressing season, species, and populations. We present important baseline field data and examine the role of environmental regulation in the embryonic development of this unique system. We describe the course of embryo development in the wild and find it to be very different from the typical development under laboratory conditions. Development across the embryo banks was synchronized within and across the sampled populations with all embryos entering diapause I during the rainy season and diapause II during the dry season. Asynchrony occurred at transient phases of the habitat, during the process of habitat desiccation, and at the end of the dry season. Our findings reveal the significance of environmental conditions in the serial character of the annual fish diapauses.
Highlights
Embryos often passively depend on their environment and can be extremely sensitive to environmental shifts
Diapause is a specific form of this dormancy which is under the control of an endogenous program
Fish hatched from embryos with short development grew faster, matured earlier, and died sooner than the phenotypes originating from the embryos with long development
Summary
Embryos often passively depend on their environment and can be extremely sensitive to environmental shifts. One strategy to overcome a lack of environmental predictability is to have high levels of intrinsic variability within the embryo bank to spread risk and preclude reproductive failure Existence of such an endogenously controlled developmental variation is strongly supported by data from the laboratory, where annual fish embryos incubated under the same conditions display great variability in their development (Furness, Lee, et al, 2015; Hu et al, 2020; Pinceel et al, 2015; Polačik et al, 2017; Wourms, 1972c). We examined the applicability of laboratory-based experimental findings to the natural incubation conditions of Nothobranchius spp. (Furness, Lee, et al, 2015; Pinceel et al, 2015; Podrabsky et al, 2007; Polačik et al, 2017; Wourms, 1972c)
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