Effects of temperature on juvenile Dungeness crab,Metacarcinus magister(Dana): survival, moulting, and mTOR signalling and neuropeptide gene expression in eyestalk ganglia, moulting gland (Y-organ), and heart

Abstract

Mechanistic target of rapamymcin (mTOR) is a highly conserved protein kinase that controls cellular protein synthesis and energy homeostasis. We hypothesize that mTOR integrates intrinsic signals (moulting hormones) and extrinsic signals (thermal stress) to regulate moulting and growth in decapod crustaceans. The effects of temperature on survival, moulting and mRNA levels of mTOR signalling genes (, ,, and) and neuropeptides ( and ) were quantified in juvenile Crabs at different moult stages (12, 19 or 26 days postmoult) were transferred from ambient temperature (∼15°C) to temperatures between 5 and 30°C for up to 14 days. Survival was 97-100% from 5 to 20°C, but none survived at 25 or 30°C. Moult stage progression accelerated from 5 to 15°C, but did not accelerate further at 20°C. In eyestalk ganglia, , and mRNA levels decreased with increasing temperatures. and mRNA levels were lowest in the eyestalk ganglia of mid-premoult animals at 20°C. In the Y-organ, mRNA levels decreased with increasing temperature and increased during premoult, and were positively correlated with haemolymph ecdysteroid titre. In the heart, moult stage had no effect on mTOR signalling gene mRNA levels; only , and mRNA levels were higher in intermoult animals at 10°C. These data suggest that temperature compensation of neuropeptide and mTOR signalling gene expression in the eyestalk ganglia and Y-organ contributes to regulate moulting in the 10 to 20°C range. The limited warm compensation in the heart may contribute to mortality at temperatures above 20°C.

Transcriptomic response to decreased pH in adult, larval and juvenile red king crab, Paralithodes camtschaticus, and interactive effects of pH and temperature on juveniles

“…In this study we attempted to avoid including specimens in the final pre-moult stage, which is characterized by large physiological shifts in water volume, ion transport and gene expression (Lee & Mykles, 2006; Chang & Mykles, 2011; Wittmann et al ., 2018). We did not observe shifts in gene expression known to be regulated as the immediate pre-moult occurs (e.g.…”

“…We did not observe shifts in gene expression known to be regulated as the immediate pre-moult occurs (e.g. mTOR pathway genes; Wittmann et al ., 2018), even though those genes were represented in our transcriptome (Table S2). The intermoult duration for first instar crabs under ambient pH and pH 7.8 and temperature conditions of ambient, +2 and +4°C used in this study ranged from 28–42 days (times were shorter at increased temperature, but not different across pH conditions) (Swiney et al ., 2017) and survival was near or at 100% through 50 days across all conditions (Swiney et al ., 2017), with 100% of specimens undergoing the first moult except for in the combined effects of pH 7.8 and +4°C (Swiney et al ., 2017).…”

Signaling Pathways That Regulate the Crustacean Molting Gland

“…The effects of temperature on survival, molting, and mTOR signaling gene expression in YO, eyestalk ganglia, and heart were determined in juvenile Dungeness crab, Metacarcinus magister . Animals at three different molt stages (12, 19, or 26 days post-ecdysis; these intervals spanned stages C to D 2-3 ) were transferred from ambient temperature (~15°C) to 5, 10, 15, 20, 25, or 30°C for 14 days ( 187 ). None of the animals transferred to 25 and 30°C survived ( 187 ).…”

“…Animals at three different molt stages (12, 19, or 26 days post-ecdysis; these intervals spanned stages C to D 2-3 ) were transferred from ambient temperature (~15°C) to 5, 10, 15, 20, 25, or 30°C for 14 days ( 187 ). None of the animals transferred to 25 and 30°C survived ( 187 ). M. magister molt successfully at 21°C, but the growth increment is less than that at 14°C ( 188 ); see ( 187 ) for additional references).…”

“…None of the animals transferred to 25 and 30°C survived ( 187 ). M. magister molt successfully at 21°C, but the growth increment is less than that at 14°C ( 188 ); see ( 187 ) for additional references). These results indicate that the upper temperature limit for M. magister molting success is between 21°C and 25°C.…”