Elevated CO2 affects reproduction and embryonic development in the pygmy squid, Idiosepius pygmaeus

This is a study on the effects parental exposure of elevated CO2 on the reproduction and embryonic development of the two-toned pygmy squid (Idiosepius pygmaeus). Adult squid were exposed to either control or elevated CO2 conditions for 14 days prior to being paired together to breed. After eggs were spawned, they were counted and photographed under microscope. The development of the embryos was then recorded with photographs (every 24 hours) until all embryos had hatched. From the photographs and count data, variables of development and reproduction were collected including number of eggs per clutch, percent of eggs that were fertile, percent of embryos that were deformed, number of embryos to hatch, time it took them to hatch from spawning, as well as size of the egg cases and embryos during distinct stages of embryonic development. These variables were compared to determine if there was an effect of elevated CO2. Abstract [Related Publication]: The oceans continue to absorb atmospheric carbon dioxide (CO2) and projected future CO2 levels could have negative implications for many marine organisms, especially during early life stages. Cephalopods are ecologically important in marine ecosystems, yet the potential effects of elevated CO2 on cephalopod reproduction and embryonic development are little studied. We allowed adult two-toned pygmy squid (Idiosepius pygmaeus) to breed in ambient control (~445 µatm) or elevated CO2 conditions (~940 µatm) and compared reproductive traits in adults and developmental characteristics of their eggs between treatments. Breeding pairs at elevated CO2 produced clutches with 40% fewer eggs, embryos that were 14% smaller directly after spawning and 5% smaller upon hatching, and an 8% increase in late-stage egg swelling compared with pairs at control conditions. Elevated CO2 did not affect fertility, time to hatch, or hatching success. Eggs were laid 40% closer together in elevated CO2 compared with control conditions, indicating a possible effect of elevated CO2 on reproductive behaviour. These results show that elevated CO2 can adversely affect reproduction and embryonic development of the two-toned pygmy squid. As the potential for adaptation is influenced by reproductive success, testing the capacity for squid to adapt to future ocean conditions should be a priority for future research.

本研究探讨了亲本暴露于升高浓度二氧化碳（CO₂）环境对双斑矮枪乌贼（Idiosepius pygmaeus）繁殖与胚胎发育的影响。实验中，成年枪乌贼先在对照或升高CO₂浓度条件下暴露14天，随后配对进行繁殖。产卵完成后，研究人员对卵粒进行计数，并在显微镜下拍摄照片。后续每隔24小时记录一次胚胎发育的照片，直至所有胚胎完成孵化。基于拍摄的图像与计数数据，研究人员收集了多项繁殖与发育相关变量，包括每窝卵的数量、受精卵占比、畸形胚胎占比、成功孵化的胚胎数、从产卵至孵化的时长，以及胚胎发育不同阶段的卵囊与胚胎尺寸。通过对比分析这些变量，以明确升高CO₂浓度是否对该物种产生影响。

【相关出版物摘要】海洋持续吸收大气中的二氧化碳（CO₂），未来预估的CO₂浓度水平可能对众多海洋生物造成负面影响，尤其在生命早期发育阶段。头足类（Cephalopods）动物在海洋生态系统中具有重要的生态功能，但目前针对升高CO₂浓度对头足类繁殖与胚胎发育潜在影响的研究仍较为匮乏。本研究让成年双斑矮枪乌贼在环境对照（约445 μatm）或升高CO₂浓度（约940 μatm）条件下进行繁殖，并对比了不同处理组中成体的繁殖特征以及其卵的发育特性。结果显示，与对照组相比，处于升高CO₂浓度环境中的繁殖配对个体所产卵窝的卵数减少40%，产卵后即刻的胚胎尺寸小14%，孵化时的胚胎尺寸小5%，且晚期卵的膨胀程度较对照组提升8%。升高CO₂浓度未对受精率、孵化时长或孵化成功率产生显著影响。与对照条件相比，升高CO₂浓度环境下的产卵间距缩短40%，这表明升高CO₂浓度可能对繁殖行为产生影响。本研究结果表明，升高CO₂浓度可对双斑矮枪乌贼的繁殖与胚胎发育产生不利影响。由于物种的适应潜力受繁殖成功率的影响，未来研究应优先探索枪乌贼适应未来海洋环境的能力。