Insights into Eyestalk Ablation Mechanism to Induce Ovarian Maturation in the Black Tiger Shrimp

Abstract

Eyestalk ablation is commonly practiced in crustacean to induce ovarian maturation in captivity. The molecular mechanism of the ablation has not been well understood, preventing a search for alternative measures to induce ovarian maturation in aquaculture. This is the first study to employ cDNA microarray to examine effects of eyestalk ablation at the transcriptomic level and pathway mapping analysis to identify potentially affected biological pathways in the black tiger shrimp (Penaeus monodon). Microarray analysis comparing between gene expression levels of ovaries from eyestalk-intact and eyestalk-ablated brooders revealed 682 differentially expressed transcripts. Based on Hierarchical clustering of gene expression patterns, Gene Ontology annotation, and relevant functions of these differentially expressed genes, several gene groups were further examined by pathway mapping analysis. Reverse-transcriptase quantitative PCR analysis for some representative transcripts confirmed microarray data. Known reproductive genes involved in vitellogenesis were dramatically increased during the ablation. Besides these transcripts expected to be induced by the ablation, transcripts whose functions involved in electron transfer mechanism, immune responses and calcium signal transduction were significantly altered following the ablation. Pathway mapping analysis revealed that the activation of gonadotropin-releasing hormone signaling, calcium signaling, and progesterone-mediated oocyte maturation pathways were putatively crucial to ovarian maturation induced by the ablation. These findings shed light on several possible molecular mechanisms of the eyestalk ablation effect and allow more focused investigation for an ultimate goal of finding alternative methods to replace the undesirable practice of the eyestalk ablation in the future.

Reproductive performances of wild male tiger shrimp, Penaeus monodon post-injection of oocyte developer without eyestalk ablation

“…Molecular assessment indicated the change of gen expression on the metabolism pathway on ablated shrimp (Uawisetwathana et al, 2011). Total fatty acid in muscle of AB group was lower than that of oodev injected males indicating the metabolism change due to the lost of several secretion glands and nervous system after ablation.…”

“…Ablated shrimp lost the sinus gland and organ X which secrets the gonadal inhibiting hormone (GIH) (Uawisetwathana et al, 2011;Urtgam et al, 2015). Shrimp without GIH due to the ablation lead to the continuously maturation process.…”

“…Shrimp without GIH due to the ablation lead to the continuously maturation process. As the consequent of the over matured is the slow growth, depleted energy for cell regeneration and health healing, decreased gamet quality and the discarded broodstock making a short time of their usage (Uawisetwathana et al, 2011).…”

“…Wild broodstocks in general have several good attributes, however their quality vary and they are claimed to be pathogenic carrier which transmitte diseases into aquaculture system (Coman et al, 2006). Production of tiger shrimp broodstock from aquaculture still has several constrains including low number of maturing spawner, the final stage of maturation is not as good as the wild spawner, un-sincronized gonad maturation between male and female stocks, low mating rate, delayed spawning time, low hatching rate and low survival of post-larvae (Marsden et al, 2008;Uawisetwathana et al, 2011;Laining et al, 2014;Laining et al, 2015).…”

“…Ablation is a technique to cut one of the spawner's eye in order to reduce production of gonadal inhitibing hormones. Although ablation can accelerate the process of gonadal development of tiger shrimp, it has several disadvantageous such as stimulating a strong stress even mortality of the spawner, destroying physiological function, decreasing gamet quality, and against to the animal welfare (Wongprasert et al, 2006;Sainz-Hernández et al, 2008;Uawisetwathana et al, 2011). Furthemore, the use of ablated tiger shrimp generally only for 3-4 maturation cycles before being discarded.…”