Effect of photoperiod on ovarian maturation in Cheirodon interruptus (Teleostei: Characidae)

Abstract Cheirodon interruptus is a ubiquitous small characid that inhabits the Pampean region and commonly used as bait. Its vast market is supplied from the wild population causing a significant environmental impact. In this study, we assess the effect of photoperiod on ovarian maturation in order to evaluate its potential as a tool to manipulate reproduction under artificial conditions. Four treatments in triplicate (light: dark, L: D) were tested: 24L: 0D, 12L: 12D, 0L: 24D and a progressive photoperiod corresponding to the daily photoperiod increments in wild during winter-spring transition, accelerated three times. The experiment was conducted for 45 days. Gonadosomatic index (GSI), oocyte mean diameter, vitellogenic oocyte proportions, plasma estradiol concentrations (E2), condition factor (Kn) and standard length were estimated. Values of mean GSI, oocyte diameter, vitellogenic oocyte proportions and E2 concentration were maximum in the progressive treatment indicating vitellogenesis stimulation. In turn the same parameters were minimum in the 24L: 0D, revealing the vitellogenesis inhibition. This study showed that photoperiodic regime play an important role in the onset of ovarian maturation in C. interruptus.

摘要 中断脂鲤（Cheirodon interruptus）是潘帕斯地区广布的小型脂鲤科鱼类，常被用作钓饵。其庞大的市场需求依赖野生种群供应，由此造成了显著的环境影响。本研究探究光周期（photoperiod）对卵巢成熟的调控效应，以评估其在人工条件下操控繁殖的应用潜力。实验设置4组光照周期处理，每组设置3个生物学重复（光照时长:黑暗时长，即L:D）：24L:0D、12L:12D、0L:24D，以及一种模拟冬春过渡季野外每日光周期增量并将该增量速率加速3倍的渐进式光周期处理。实验周期为45天。本研究测定了多项指标，包括性腺指数（Gonadosomatic Index，GSI）、卵母细胞平均直径、卵黄发生期卵母细胞占比、血浆雌二醇浓度（E2）、条件系数（Condition Factor，Kn）以及标准体长。结果显示，渐进式光周期处理组的性腺指数、卵母细胞直径、卵黄发生期卵母细胞占比及血浆雌二醇浓度均达到最高值，表明该处理可刺激卵黄发生；而24L:0D组的上述参数均处于最低水平，提示卵黄发生受到抑制。本研究证实，光周期制度对中断脂鲤的卵巢成熟启动具有重要调控作用。