Effects of temperature, age, and stage on testis development in diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae)

Authors: HIROYOSHI, SATOSHI - TOKYO UNIVERSITY OF AGRICULTURE & TECHNOLOGY; MITSUNAGA, TAKAYUKI - NATIONAL AGRICULTURE AND FOOD RESEARCH ORGANIZATION (NARO), AGRICULTRUAL RESEARCH CENTER; Reddy, Gadi V.P.

Submitted to: Physiological Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2021
Publication Date: 3/27/2021
Citation: Hiroyoshi, S., Mitsunaga, T., Reddy, G.V. 2021. Effects of temperature, age, and stage on testis development in diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae). Physiological Entomology. 46:1-10. https://doi.org/10.1111/phen.12359.
DOI: https://doi.org/10.1111/phen.12359

Interpretive Summary: Recent studies suggest that extreme high temperatures for several hours or several days seriously reduce the male reproductive value, leading to infertility or sterility. The present study was undertaken in the laboratory to clarify the effects of temperature, age and stage on testis volume in diamondback moth. The results from the present study indicated that testis volume appears to be a good indicator for estimating age roughly (young, middle or old) in wild adult diamondback moth males. This relationship may be applied to other lepidopteran insects, except for species with very short adult longevity, because testis shrinkage appears to be common among many moths, and testis shrinkage is often initiated at the pupal stage. This novel technique will provide detailed information on the age and seasonal occurrence of wild diamondback moth populations, improving our understanding of their ecology, physiology and control.

Technical Abstract: 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 (Linnaeus) (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 P. xylostella 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 P. xylostella in wild populations can be estimated roughly from the data on testis volume, temperature, and forewing length.