Embryonic diapause of a freshwater crustacean Polyphemus pediculus (Cladocera, Onychopoda)
Butorina, L. G.
published: Nov 1, 2016
published online: Nov 4, 2016
manuscript accepted: Sep 23, 2016
manuscript received: Jul 1, 2016
ArtNo. ESP141018901004, Price: 29.00 €
Abstract Embryonic diapause of Polyphemus pediculus (Linnaeus, 1761) consists of five successive periods. The periods of prediapause and inhibition proceed in the body of females under the impact of an endogenous factor. The periods of rest, reactivation, formation and the emerging of young proceed in the water body under the combined impact of endogenous and exogenous factors. During the periods of prediapause and inhibition, the length of different diapause periods and the duration of the period of emerging of young are programmed in correspondence with the length of the daylight period in the environment of female habitation. External conditions and the length of the period of rest affect egg viability. The effect of the long-term cryptobiosis is less negative compared with that of the anabiosis and, especially, the unhydrocryptobiosis. Egg reactivation only occurs after occupying water at a temperature of 1 to 6 degrees above zero for a period of time sufficient for the complete elimination of inhibitors accumulated by eggs during their stay in the female body. The qualitative diversity of laid eggs depends on the frequency and diversity of the copulative contacts of females, the daylight period length and the environmental temperature at the time when eggs undergo transition to the state of rest in the body of a female. The egg layings of the long daylight period are characterized by the highest qualitative diversity, with a multi-year rhythm of development prevailing. The asynchronous emerging of the young represents an ecological adaptation, which promotes the increase of the population gene pool. Embryonic diapause of P. pediculus is more dependent on the endogenous factors and is genetically more predetermined compared with the larval and the imaginal ones.
Polyphemus pediculus • embryonic diapauses • prediapause • periods of inhibition • rest • reactivations • young formation and emerging • cryptobiosis • anabiosis • unhydrobiosis • eggs photoperiodic type