This study interrogated factors which affect the appearance of secondary sexual characteristics, namely, fin spinelets (rigid dimorphic structure empirically associated with male sexual maturity in characids), in Astyanax altiparanae. Many variables such as the season of the year and several biotic components, including organism length, sex, phase of maturation, and the presence of gonads, were investigated. These factors were then associated with the physiological development of fin spinelets. The development of this trait is related to reproductive strategies but demonstrates considerable population variability as it is found throughout the year in some species but only during specific periods in others. Seventy-five specimens obtained from spontaneous spawn of farmed fish were arbitrarily grouped into small-, medium-, and large-sized groups in both summer and winter. Gonadal histology was performed to confirm each animal’s sex and phase of maturation. Diaphanization of the fish was performed to visualize, count, and measure the fin spinelets. Finally, gonadectomization of some males was utilized to investigate the gonadal effect on the presence of fin spinelets. The present results show that the presence of fin spinelets is a secondary sexual characteristic of males which occurs independently of the season and is always present in males longer than 48 mm. However, in the summer, male specimens presented more rays with fin spinelets than during the winter. Furthermore, since fin spinelets were observed on immature males as well as spawning capable males, their presence cannot be directly associated with sexual maturity in male A. altiparanae, as previously supposed. Finally, gonadectomization resulted in an initial reduction in the length of fin spinelets. However, this trend was eventually normalized with time.

该研究询问了影响Astyanax altiparanae中第二性征外观的因素，即鳍尖刺（根据经验与男性性成熟相关的硬质二形结构）。研究了许多变量，例如一年中的季节和几种生物成分，包括生物体长度、性别、成熟阶段和性腺的存在。这些因素随后与鳍尖刺的生理发育有关。这种性状的发展与繁殖策略有关，但表现出相当大的种群变异性，因为它在某些物种中全年都有发现，而在其他物种中仅在特定时期发现。从养殖鱼类的自然产卵中获得的 75 个标本在夏季和冬季被任意分为小型、中型和大型组。进行性腺组织学以确认每只动物的性别和成熟阶段。对鱼进行透明化以观察、计数和测量鳍尖刺。最后，一些雄性的性腺切除术被用来研究性腺对鳍尖刺存在的影响。目前的结果表明，鳍尖刺的存在是雄性的第二性征，其发生与季节无关，并且总是存在于长度超过 48 毫米的雄性身上。然而，在夏季，与冬季相比，雄性标本呈现出更多的带有鳍尖刺的射线。此外，由于在未成熟的雄性和能产卵的雄性身上都观察到了鳍尖刺，它们的存在不能直接与雄性的性成熟有关。目前的结果表明，鳍尖刺的存在是雄性的第二性征，其发生与季节无关，并且总是存在于长度超过 48 毫米的雄性身上。然而，在夏季，与冬季相比，雄性标本呈现出更多的带有鳍尖刺的射线。此外，由于在未成熟的雄性和有产卵能力的雄性身上都观察到了鳍尖刺，它们的存在不能与雄性的性成熟直接相关。目前的结果表明，鳍尖刺的存在是雄性的第二性征，其发生与季节无关，并且总是存在于长度超过 48 毫米的雄性身上。然而，在夏季，与冬季相比，雄性标本呈现出更多的带有鳍尖刺的射线。此外，由于在未成熟的雄性和有产卵能力的雄性身上都观察到了鳍尖刺，它们的存在不能与雄性的性成熟直接相关。A. altiparanae，如先前所假设的。最后，性腺切除导致鳍尖刺长度的初始减少。然而，这种趋势最终随着时间的推移而正常化。