Influence of temperature
Inviato: lun feb 26, 2007 5:52 pm
tratto da "incubation of reptile eggs" gunther kohler
The incubation temperature determines not only the speed of the development, and thus the duration of the incubation, but for many species of reptiles it also influences sex determination,pigmentation, as well as postembryonic growt, shedding cycles, thermoregulation, ands sexual behaviour of young animal. The temperature influences the cells and tissues of the embryo during development. Since the influence of temperature extends to postembryonic processes, it can be assumed that it also has irreversible effect on the developing embryo. A probable target organ for temperature during embryogenesis is the hypotalamus, which by means of so-called releasing hormones controls the activity of the pituitary gland. The pituitary gland produces numerous hormones that regulate important physiological processes, as for example growth, shedding cycles, pigmentation, mating behaviour, and maturity of follicles, just to name the important ones. All effects that result from incubation temperatire relate to process that - direclty or indirectly - are under the control of the hypothalamus. The hypothalamus develops during the incubation phase where it is also shown that the temperature influences the processes described in the folloing sections.
The temperature of an egg primarily depends on the environmental temperature. However, the metabolic process of the growing embryo also produce some heat of their own. This metabolic heat is minimal right after egg deposition, but rises considerably until hantching. For large clutches the metabolic heat can cause the temperature of the clutch to ne higher than the environmental temperature by several degree (Carr and Hirth, 1961; Burger, 1976). A well insulating substrate (vermiculite) can have the effect that the embryos produce more metabolic heat than can be radiated off. In these cases, the egg temperature can be considerably higher than the environmental temperature.
The incubation temperature determines not only the speed of the development, and thus the duration of the incubation, but for many species of reptiles it also influences sex determination,pigmentation, as well as postembryonic growt, shedding cycles, thermoregulation, ands sexual behaviour of young animal. The temperature influences the cells and tissues of the embryo during development. Since the influence of temperature extends to postembryonic processes, it can be assumed that it also has irreversible effect on the developing embryo. A probable target organ for temperature during embryogenesis is the hypotalamus, which by means of so-called releasing hormones controls the activity of the pituitary gland. The pituitary gland produces numerous hormones that regulate important physiological processes, as for example growth, shedding cycles, pigmentation, mating behaviour, and maturity of follicles, just to name the important ones. All effects that result from incubation temperatire relate to process that - direclty or indirectly - are under the control of the hypothalamus. The hypothalamus develops during the incubation phase where it is also shown that the temperature influences the processes described in the folloing sections.
The temperature of an egg primarily depends on the environmental temperature. However, the metabolic process of the growing embryo also produce some heat of their own. This metabolic heat is minimal right after egg deposition, but rises considerably until hantching. For large clutches the metabolic heat can cause the temperature of the clutch to ne higher than the environmental temperature by several degree (Carr and Hirth, 1961; Burger, 1976). A well insulating substrate (vermiculite) can have the effect that the embryos produce more metabolic heat than can be radiated off. In these cases, the egg temperature can be considerably higher than the environmental temperature.