Quantitative analysis of hypertrophy and hyperactivity in the androgenic gland of eyestalk-ablated male Pacific white shrimp Litopenaeus vannamei during molt stages

Abstract

Quantitative analysis of hypertrophy and hyperactivity in tissue of the androgenic gland of eyestalk-ablated male Pacific white shrimp Litopenaeus vannamei was made during the molt cycle by measuring the area of androgenic gland cells located in the subterminal region of the terminal ampoule and measuring the expression of the insulin-like androgenic gland hormone precursor gene (Lv-IAG) in the distal vas deferens and terminal ampoule, respectively. Data were compared to intact shrimp at the same molt stages. In eyestalk-ablated shrimp, the lack of negative control from the X-organ–sinus gland complex produced hypertrophy in androgenic gland cells, because the area of the cells folded approximately 1.5 times up to the intermolt stage, when compared to the intact group. It also produced hyperactivity because the relative expression of Lv-IAG was significantly higher than the intact group at all molt stages. After gathering data from the vas deferens and terminal ampoule, the relative expression of Lv-IAG was maintained at higher levels, without a significant difference during the molt stages. However, after each tissue was analyzed independently, a bell-shape curve pattern occurred, according to the molt cycle, as also occurred in intact shrimp. This suggests that in the absence of eyestalks, the brain and nervous system are operating secondarily to synchronize Lv-IAG expression into the molt cycle. The relative expression of Lv-IAG was significantly greater in the terminal ampoule than in the distal vas deferens. In summary, these findings support a reproductive endocrine axis in L. vannamei, as an eyestalk–androgenic gland linkage concomitant with the molt cycle.