Quantifying Preferences and Responsiveness of Marine Zooplankton to Changing Environmental Conditions using Microfluidics

Global environmental change significantly affects marine species composition. However, analyzing the impact of these changes on marine zooplankton communities was so far mostly limited to assessing lethal doses through mortality assays and hence did not allow a direct assessment of the preferred conditions, or preferendum. Here, we use a microfluidic device to characterize individual behavior of actively swimming zooplankton, and to quantitatively determine their ecological preferendum. For the annelid zooplankton model Platynereis dumerilii we observe a broader pH preferendum than for the copepod Euterpina acutifrons, and reveal previously unrecognized sub-populations with different pH preferenda. For Platynereis, the minimum concentration difference required to elicit a response (responsiveness) is ~1 μM for H+ and ~13.7 mM for NaCl. Furthermore, using laser ablations we show that olfactomedin-expressing sensory cells mediate chemical responsiveness in the Platynereis foregut. Taken together, our microfluidic approach allows precise assessment and functional understanding of environmental perception on planktonic behaviour.全球环境变化显著影响海洋物种组成。然而，迄今为止，探究此类变化对海洋浮游动物（zooplankton）群落的影响，大多局限于通过死亡率测定法评估致死剂量，因而无法直接评估生物的偏好条件——即偏好域（preferendum）。本研究采用微流控装置（microfluidic device），解析主动游动的浮游动物个体的行为特征，并定量测定其生态偏好域。以浮游环节动物模型物种杜氏阔沙蚕（Platynereis dumerilii）为研究对象，我们发现其pH偏好域较桡足类（copepod）Euterpina acutifrons更宽泛，并揭示了此前未被识别的、具有不同pH偏好域的亚种群。针对杜氏阔沙蚕，引发响应所需的最小浓度差（响应性，responsiveness）约为：氢离子（H+）1 μM，氯化钠（NaCl）13.7 mM。此外，通过激光消融（laser ablations）实验，我们证实表达olfactomedin的感觉细胞介导了杜氏阔沙蚕前肠的化学响应性。综上，本研究的微流控方法可实现对浮游动物行为相关环境感知的精准评估与功能解析。