Abstract
During pond culture of Eriocheir sinensis, a high limb-impairment rate restricts the industry development and quality. Therefore, research on limb autotomy and regeneration has important practical significance for the industrial development and basic biology of E. sinensis. This study evaluated the changes in bud morphology, growth-related gene expression and nutritional status during cheliped regeneration in E. sinensis. The study found that the new cheliped was pre-formed in the bud and then regenerated with the completion of molting of E. sinensis. The new cheliped was similar in morphology to the normal cheliped after the first molting but smaller in size. The qRT-PCR results of growth-related genes showed that the expression levels of EcR-mRNA (ecdysteroid receptor) and Chi-mRNA (chitinase) were significantly up-regulated, whereas the expression of MIH-mRNA (molt-inhibiting hormone) was significantly down-regulated (P < 0.05). The nutritional status during the regeneration process showed that the hepatopancreas total lipid content decreased significantly within 28 days and was significantly lower in the autotomy group than in the control group at 14 d and 21 d (P < 0.05). The hepatopancreas fatty acid composition results showed that saturated fatty acids (SFA), highly unsaturated fatty acids (HUFA) and n-3/n-6 were significantly higher in the autotomy group than in the control group at 21 d (P < 0.05), whereas the ∑ n-6 PUFA and ∑ n-3 PUFA at 1 d and 7 d, and the monounsaturated fatty acid (MUFA) at 28 d in the autotomy group were significantly lower than in the control group (P < 0.05). Moreover, the levels of eicosatetraenoic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) showed that DHA was significantly lower at 7 d and significantly higher at 21 d in the autotomy group than in the control group (P < 0.05), whereas ARA and EPA were not significantly different between the two groups. Muscle L-tryptophan content was significantly lower at 1 d and significantly higher at 7 d in the autotomy group than in the control group (P < 0.05). These results indicate that during the cheliped regeneration process, crabs could accelerate molting and regeneration by regulating growth-related gene expression (e.g., EcR-mRNA and MIH-mRNA) and nutrient metabolism (e.g., lipid metabolism).
Highlights
In the face of threats from other animals or environmental stress, many animals take active measures to respond positively in the natural environment
A few days later, transparent hemisphere-like crystalline encrustations broke out of the dark brown biofilm at the autotomy site (Fig 1C), followed by rod-like growth and prolongation, and the surface was fully covered with black material (Fig 1D, 1E and 1F)
The results showed that the expression of EcR-mRNA in the tissues was significantly higher in the autotomy group than that in the control group, whereas the expression of MIHmRNA was significantly lower in the autotomy group
Summary
In the face of threats from other animals or environmental stress, many animals take active measures to respond positively in the natural environment. As a congenital, highly effective reflexive response, is very useful in the process of escaping from danger and avoiding threats[1,2]. Autotomy can let animals escape from danger temporarily, when the autonomous animals are threatened again, it is generally difficult to escape again. Autotomy brings many negative effects on organisms, such as long-term loss of energy [3], immunity and antibacterial response [4]. The best way to compensate for autotomy costs is limb regeneration. Animals with limb autotomy generally achieve limb regeneration after a period of time. Study on the autotomy and regeneration of crustaceans have been widely studied, such as feeding rate [9], growth rate [10], and immune function [4,11]
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