Nature and nurture in dormancy: dissolved oxygen, pH, and maternal investment impact Bythotrephes longimanus resting egg emergence and neonate condition

Abstract

Bythotrephes longimanus (Onychopoda: Cercopagidae), an invasive zooplankter in North America, requires suitable habitat to satisfy its planktonic and resting stages, which occupy the pelagia and sediment of lakes, respectively. Thousands of resting eggs from hundreds of planktonic mothers were exposed to laboratory conditions that mimicked gradients observed in lake sediment (dissolved oxygen = 1.4–11.9 mg·L–1; pH = 3–11). Eggs hatched in all treatments, which confirms the utility of dormancy and the robustness of the resting egg in B. longimanus. However, hatching success and neonate condition were greatest when dormancy conditions were maintained at near-saturated dissolved oxygen and near-neutral pH; deviations from these conditions resulted in prolonged development, smaller neonates, and the failure of many eggs to hatch. In addition to the influence of environmental conditions, heavier mothers produced larger eggs that hatched more frequently and resulted in heavier neonates. These maternal effects are likely due to greater energy investment by healthier mothers. This study suggests that nature and nurture influence dormancy success, and the results underscore that both life-cycle stages of B. longimanus need to be considered to understand its range expansion.