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Embryonic Diapause (embryonic + diapause)
Selected AbstractsMaternal control of cold and desiccation tolerance in eggs of the band-legged ground cricket Dianemobius nigrofasciatus in relation to embryonic diapauseENTOMOLOGICAL RESEARCH, Issue 1 2008Shin G. GOTO Abstract Cold and desiccation tolerance was investigated in the eggs of the band-legged ground cricket Dianemobius nigrofasciatus in relation to embryonic diapause. Diapause eggs were more tolerant to both desiccation and cold than non-diapause eggs. In addition, diapause-destined eggs on day zero (0,12 h after being laid) already showed high tolerance to these stresses before entering diapause. This clearly indicates that stress tolerance, like diapause, is controlled by photoperiod, but is not directly associated with diapause itself. Because the acquisition of stress tolerance predates the onset of diapause, it is plausible that diapause programming during some period before the onset of diapause is involved in the acquisition of stress tolerance. Weights and sizes were nearly identical in short-day and long-day eggs until day five. Sorbitol, a major sugar alcohol in eggs of D. nigrofasciatus, was accumulated at the same level in short-day and long-day eggs on days zero and five. These results indicate that the surface-to-volume ratio as well as the accumulation of sugar alcohol is not involved in the acquisition of stress tolerance. Maternal factors are clearly involved in the acquisition of stress tolerance in D. nigrofasciatus eggs, but the physiological mechanisms underlying the tolerance are still unclear. [source] Effects of temperature of adults and eggs on the induction of embryonic diapause in the band-legged ground cricket, Dianemobius nigrofasciatusPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2006EIJI FUKUMOTO Abstract Eggs laid by adult female Dianemobius nigrofasciatus, reared under long-day (LD 16 : 8 h, 25 °C) or short-day (LD 12 : 12 h, 25 °C) conditions from the nymphal stage, are kept at several constant temperatures. At 22.5,30.0 °C, eggs laid by long-day adults show lower incidences of diapause than those laid by short-day adults. In both eggs laid by adults under long-day conditions and those under short-day conditions, the higher the temperature at which the eggs are kept, the lower the incidence of diapause. When eggs of long-day adults are exposed to a low-temperature pulse (10 °C, 24 h) on the day of deposition (day 0), the incidence of diapause increases. The low-temperature pulse on day 1 does not increase the incidence of diapause. By contrast, when the eggs of short-day adults are exposed to a high-temperature pulse (35 °C, 24 h) on day 0 or day 1, the incidence of diapause decreases. The temperature pulses on day 0 are more effective at diapause prevention. Staining of diapause eggs by the Feulgen,Rossenbeck method shows that the eggs enter diapause at the blastoderm stage, which is on day 1 or day 2 at 25 °C. The exposure of adults to long days and higher temperatures prevents the eggs from entering diapause. In D. nigrofasciatus, embryonic diapause is controlled by maternal effects, adult photoperiod and temperature, and egg temperature before or at diapause. [source] Evolutionary innovations of squamate reproductive and developmental biology in the family ChamaeleonidaeBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010ROBIN M. ANDREWS The availability of molecular phylogenies has greatly accelerated our understanding of evolutionary innovations in the context of their origin and rate of evolution. Here, we assess the evolution of reproductive mode, developmental rate and body size in a group of squamate reptiles: the chameleons. Oviparity is ancestral and viviparity has evolved at least twice: Bradypodion and members of the Trioceros bitaeniatus clade are viviparous. Viviparous species are medium-sized as a result of convergence from either small-sized ancestors or large-sized ancestors, respectively, but do not differ from oviparous species in clutch size, hatchling size or the trade-off between clutch and hatchling size. Basal chameleons (Brookesia, Rhampholeon and Rieppeleon) are small-sized and have developmental rates comparable with those of other lizards. Derived chameleons (Calumma, Chamaeleo, Trioceros and Furcifer) are mostly large-sized and all have relatively slow developmental rates. Several clades of derived chameleons also exhibit developmental arrest (embryonic diapause or embryonic diapause plus cold torpor) and incubation periods extend to 6,10 months or more. Developmental arrest is associated with dry, highly seasonal climates in which the period favourable for oviposition and hatching is short. Long incubation periods thus ensure that hatching occurs during the favourable season following egg laying. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 656,668. [source] | ||||||||||