title: Temperature-dependent regulation of reproduction in the diving beetle Dytiscus sharpi (Coleoptera: Dytiscidae).
abstract: The effects of temperature on the mating behavior, gonad development, germ cell maturation, and egg spawning of the predaceous diving beetle Dytiscus sharpi (Coleoptera; Dytiscidae), were investigated. By field observations, we found that mating behavior started in October and occurred more frequently from November to December. Under our laboratory breeding conditions, we observed almost the same seasonal variation in mating behavior. We found that temperatures lower than 20 degrees C were required to trigger mating behavior. We also found the same temperature threshold triggered gonadogenesis as well as spermatogenesis. Furthermore, for females, exposure to lower temperatures (<8 degrees C) during the winter was required for egg maturation and spawning in spring; that is, there was a second threshold for successful female reproduction. We conclude that the termination of summer reproductive diapause of D. sharpi is regulated in a temperature-dependent manner, thus effecting the adaptation of D. sharpi to southern warm habitats.
authors.affiliation: Laboratories of Rare Water Insects, Shibamata, Katsushika, Tokyo, Japan. inoda@nano.c.u-tokyo.ac.jp
authors.forename: Toshio
authors.initials: T
authors.lastname: Inoda
authors.forename: Fumitada
authors.initials: F
authors.lastname: Tajima
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Taniguchi
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Saeki
authors.forename: Kazuki
authors.initials: K
authors.lastname: Numakura
authors.forename: Masami
authors.initials: M
authors.lastname: Hasegawa
authors.forename: Shinji
authors.initials: S
authors.lastname: Kamimura
mesh_terms: D000818:Animals; D001517:Coleoptera / Q000502:physiology*; D005260:Female; D006066:Gonads / Q000502:physiology; D008297:Male; D010058:Oviposition / Q000502:physiology; D010063:Ovum / Q000254:growth & development; D012726:Sexual Behavior, Animal / Q000502:physiology; D013079:Sperm Maturation / Q000502:physiology; D013696:Temperature; D014867:Water / Q000032:analysis
chemical_list: D014867:Water