Abstract
Red king crab (Paralithodes camtschaticus) and snow crab (Chionoecetes opilio) are deep-sea crustaceans widely distributed in the North Pacific and Northwest Atlantic Oceans. These giant predators have invaded the Barents Sea over the past decades, and climate-driven temperature changes may influence their distribution and abundance in the sub-Arctic region. Molting and growth in crustaceans are strongly affected by temperature, but the underlying molecular mechanisms are little known, particularly in cold-water species. Here, we describe multiple regulatory factors in the two high-latitude crabs by developing de novo transcriptomes from the molting gland (Y-organ or YO) and eye stalk ganglia (ESG), in addition to the hepatopancreas and claw muscle of red king crab. The Halloween genes encoding the ecdysteroidogenic enzymes were expressed in YO, and the ESG contained multiple neuropeptides, including molt-inhibiting hormone (MIH), crustacean hyperglycemic hormone (CHH), and ion-transport peptide (ITP). Both crabs expressed a diversity of growth-related factors, such as mTOR, AKT, Rheb and AMPKα, and stress-responsive factors, including multiple heat shock proteins (HSPs). Temperature effects on the expression of key regulatory genes were quantified by qPCR in adult red king crab males kept at 4°C or 10°C for two weeks during intermolt. The Halloween genes tended to be upregulated in YO at high temperature, while the ecdysteroid receptor and several growth regulators showed tissue-specific responses to elevated temperature. Constitutive and heat-inducible HSPs were expressed in an inverse temperature-dependent manner, suggesting that adult red king crabs can acclimate to increased water temperatures.
Highlights
Red king crab and snow crab are giant deep-sea predators in the benthic ecosystems of sub-Arctic regions in the North Pacific and North Atlantic Oceans
Temperature effects on the expression of key regulatory genes were quantified by quantitative polymerase chain reaction (qPCR) in adult red king crab males kept at 4 ◦C or 10 ◦C for two weeks during intermolt
Among the many stress-response genes expressed by the two crab species, we identified multiple high- and low-molecular heat shock proteins (HSPs), heat shock factor 1 (HSF-1), hypoxia inducible factor 1 (HIF1) α and β sub units, HIF1α inhibitor (HIF1AN), HIF-prolyl hydroxylase and hypoxia up-regulated protein 1 (HYOU1)
Summary
Red king crab is among the world’s largest arthropods attaining weights up to 11 kg and with legs spanning 1.8 m, while snow crab is slightly smaller (Stevens, 2014). They are highly important commercial fisheries resources, and both species have established nonnative populations in the Barents Sea. Snow crabs inhabit depths down to 1400 m at temperatures from − 1.5 ◦C to 4 ◦C year-round (Squires, 1990; Dawe and Colbourne, 2002), while red king crabs occur at depths down to 400 m in the Barents Sea with temperatures ranging from below freezing to about 8 ◦С (Stiansen et al, 2009). Juvenile red king crabs showed increased growth up to 15 ◦C and an inverse exponential relationship between intermolt period and temperature up to 12 ◦C (Stoner et al, 2010; Long and Daly, 2017). Intermolt period was shorter at 8 ◦C than at 3 ◦C in juvenile snow crabs (Yamamoto et al, 2015)
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