Transcriptome Effects of High CO2 and Low O2 Conditions on the California Market Squid, Doryteuthis opalescens

Embryos of the market squid, D. opalescens, may be vulnerable to two aspects of climate change: expansion of oxygen minimum zones (OMZs) and ocean acidification. In order to investigate how D. opalescens will respond to these conditions, squid embryos were harvested in La Jolla, CA and placed in replicate flow-through seawater tanks of four treatments: ambient seawater (control), high-CO₂/low-pH (hypercapnia), low-O₂ (hypoxia), and high-CO₂/low-pH, low-O₂ (hypHOxia). Embryos from five capsules per tank (2 tanks/treatment, eight samples total) were harvested after 25 days and flash-frozen; total RNA was extracted and submitted for genome-wide gene expression analysis (RNA-seq). These sequences will form a transcriptome reference database for this species. Slowed development under hypoxia observed by Navarro et al. suggests this condition represents a major physiological stress for the embryos. Based on previous work, we predict gene expression changes in metabolic (e.g. octopine dehydrogenase), ion regulatory (e.g. Na+/K+-ATPase), and statolith calcification genes (e.g. carbonic anhydrase). Gene expression response will be important in determining the sustainability of this lucrative fishery, particularly since D. opalescens is an semelparous species where next year’s catch depends entirely on survival of the previous year’s embryos. In addition, observed gene expression changes in response to pH, pCO₂, and pO₂ may help elucidate how other marine organisms (and ultimately marine ecosystems) will respond to future oceanographic conditions.