In Lepidoptera, it is known that larval and pupal testes enlarge in volume and then decrease in size over various phases of the pupal stage. After adult emergence, testis shrinkage continues. In the present study, the effects of temperature, age and stage on testis development were investigated in the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae). Laboratory experiments indicated that in the adult stage, testis shrank markedly with age and with increasing temperatures, when males were reared at 15, 20, 25 or 30 °C during the larval and pupal stages and then transferred to other temperatures. When kept at 15, 20, 25 or 30 °C throughout their entire life (larva, pupa and adult), the higher the temperature, the smaller the testis volume at any given adult age, indicating that larval and/or pupal rearing temperatures also affected testis development. Field experiments carried out in Tokyo showed that testis volume in wild adult males of diamondback moth was quite varied, suggesting that this population had both young and old males at each survey time. The lower the larval and pupal rearing temperature, the larger the adult, as measured by forewing length. Since larger adults tended to have larger testis at adult emergence, adult testis volume should be compensated based on the forewing length. Mating reduced the testis size. Our results suggest that adult age of diamondback moths in wild populations can be estimated roughly from the data on testis volume, temperature and forewing length.

中文翻译：

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温度、年龄和阶段对小菜蛾 Plutella xylostella (L.) 睾丸发育的影响（鳞翅目：小菜蛾科）

在鳞翅目中，已知幼虫和蛹的睾丸在蛹期的各个阶段体积增大，然后尺寸减小。成年后睾丸继续萎缩。在本研究中，研究了温度、年龄和阶段对小菜蛾Plutella xylostella睾丸发育的影响。（鳞翅目：Plutellidae）。实验室实验表明，在成虫阶段，当雄性在幼虫和蛹阶段分别在 15、20、25 或 30°C 饲养，然后转移到其他温度时，睾丸随着年龄的增长和温度的升高而显着收缩。当整个生命周期（幼虫、蛹和成虫）保持在 15、20、25 或 30°C 时，温度越高，在任何给定的成年年龄睾丸体积越小，这表明幼虫和/或蛹的饲养温度也影响睾丸发育。在东京进行的田间实验表明，野生成年雄性小菜蛾的睾丸体积差异很大，这表明该种群在每个调查时间都有年轻和年老的雄性。根据前翅长度测量，幼虫和蛹的饲养温度越低，成虫越大。由于较大的成虫在成虫出现时往往有较大的睾丸，因此应根据前翅长度来补偿成虫的睾丸体积。交配减小了睾丸的大小。我们的研究结果表明，可以根据睾丸体积、温度和前翅长度的数据粗略估计野生种群中小菜蛾的成年年龄。