|
|
Ontogeny of exaggerated structures in dung beetles (Coleoptera: Scarabaeinae)
Žídek, Radim ; Šípek, Petr (advisor) ; Hanus, Robert (referee)
E n g l i s h a b s t r a c t Horns of scarab beetles represent a secondary sexual characters present mostly in males, to whom they serve as weapons in combats over the acces to females. In many species, two discrete male forms occur, "horned" and "hornless", which employ different reproductive strategies. Adult body size and horn morphology are determined by nutritional conditions encountered by larvae during their development. Switching between developmental pathways is accomplished by circulating levels of juvenile hormone (JH) which reflect body size, and genetically determined threshold of sensitivity to it. When body size is larger then threshold, horn growth occur, whereas if it's not, a brief pulse of ecdysone reprogramme the development and hornless adult emerge. Reprogramming the development encompass modifications of the insulin receptor pathway as well as changes in exact domains of genes expression envolved in specifying the proximodistal axis of the developing horn. Development of horns is morphologically reminiscent that of other insect appendages, with which it shares the expression of genes wingless, decapentaplegic, Distal-less, dachshund, homothorax, aristaless and EGFR, parts of gene regulatory network ensuring origin of the outgrowth of the cuticle. Some of them are expressed through...
|
|
| |
|
|
Ontogeny of exaggerated structures in dung beetles (Coleoptera: Scarabaeinae)
Žídek, Radim ; Hanus, Robert (referee) ; Šípek, Petr (advisor)
E n g l i s h a b s t r a c t Horns of scarab beetles represent a secondary sexual characters present mostly in males, to whom they serve as weapons in combats over the acces to females. In many species, two discrete male forms occur, "horned" and "hornless", which employ different reproductive strategies. Adult body size and horn morphology are determined by nutritional conditions encountered by larvae during their development. Switching between developmental pathways is accomplished by circulating levels of juvenile hormone (JH) which reflect body size, and genetically determined threshold of sensitivity to it. When body size is larger then threshold, horn growth occur, whereas if it's not, a brief pulse of ecdysone reprogramme the development and hornless adult emerge. Reprogramming the development encompass modifications of the insulin receptor pathway as well as changes in exact domains of genes expression envolved in specifying the proximodistal axis of the developing horn. Development of horns is morphologically reminiscent that of other insect appendages, with which it shares the expression of genes wingless, decapentaplegic, Distal-less, dachshund, homothorax, aristaless and EGFR, parts of gene regulatory network ensuring origin of the outgrowth of the cuticle. Some of them are expressed through...
|
|
|
Novel roles for the corpus allatum hormone in the cost of sexual interactions in the linden bug Pyrrhocoris apterus
PROVAZNÍK, Jan
The decrease of lifespan by mating is a common, yet poorly understood occurrence. Juvenile hormone (JH) is widely believed to mediate shortened lifespan in insect, caused by mating. In this study we tested the role of JH in the linden bug (Pyrrhocoris apterus) by removal of the corpus allatum gland and thus the JH source. We then proceeded to study the lifespan of mated animals vs. virgin animals. Virgin animals without JH live longer as was expected. The effect on mated animals is however different between males and females. Surprisingly in females, JH seems to lower the cost of mating. In males, on the other hand, the cost of mating seems to be independent on JH levels. Another surprising conclusion is that the level of JH in females affects the lifespan of males that mate with such females.
|
|
|
Physiological mechanisms of aging in maless of model insect species
PROVAZNÍK, Jan
Trade-off between reproduction and longevity is a widely accepted fact, yet proximate mechanisms are scarcely understood. In this work I tested differences in lifespan between diapause and non-diapause males of a model insect, the linden bug Pyrrhocoris apterus. Also the role of juvenile hormone in regulation of longevity and immunity (measured by relative phenoloxidase activity) was assessed. In addition to that, I examined if juvenile hormone is the mediator of reduction in longevity induced by mating.
|
guest ::
