Exploration of the functional properties of red cuticle patch of redclaw crayfish (Cherax quadricarinatus) by histological and transcriptomic analysis

The redclaw crayfish (Cherax quadricarinatus) is being farmed on an increasing scale in various tropical and subtropical regions. The most distinctive feature of the adult male redclaw crayfish is the red cuticle patch on the lateral cuticle of the chelae. It is an important indicator of the health status, reproduction, and resistance to predators of this species, but little is known about its functional properties. In this study, we used redclaw crayfish (45.35 +/- 16.74 g) as experimental subjects. Histological comparison of the red cuticle patch on male redclaw crayfish chelae with the cuticle on female redclaw crayfish chelae revealed that the red cuticle patch lacked exocuticle. High performance liquid chromatography analysis demonstrated that the concentration of free astaxanthin in the red cuticle patch was much higher than that in the chelae of female redclaw crayfish. Further analysis of transcriptome data from epithelial tissue of the chelae revealed that genes related to chela structure were highly expressed in the red cuticle patch of males. Immunity-related genes were not specifically expressed in the red cuticle patch, and immune-and growth-related genes that require calcium ion for activation were down-regulated in the patch. Our results indicated that regulation of genes related to astaxanthin binding was not a single up-or down-regulation mode. This study demonstrated structural differences in the chela cuticle between male and female redclaw crayfish and revealed the molecular basis for the functional properties of the red cuticle patch.

Automated summary

This study revealed structural differences in the chela cuticle between male and female redclaw crayfish, and identified the high expression of genes related to chela structure in the red cuticle patch. Immunity-related genes were not specifically expressed in the red cuticle patch.