芋果蝇卵丝季节性多型及其环境预示信号探究

多型是指同一基因型响应环境预示信号诱导而产生两个或更多间断表型的现象。预示信号对未来环境的准确预测是多型维持的关键。多型生物基于环境诱导产生的表型在功能、解剖和行为上的变化远超仅由遗传引起的差异。基于多型生物的生态发育生物学研究对于发育生物学的思想和实践均具有重要意义。我们通过前期研究发现，在云南保山，海林芋果蝇在寄主植物爬树龙上进化出了卵丝的多型（这是昆虫卵期多型首次被发现）：该虫将卵产于寄主花序内，其夏季世代卵丝短，一龄幼虫直接孵化取食佛焰苞；秋季世代（越冬世代）卵丝长，一龄幼虫在卵壳内于果序上越冬至翌年果实成熟后孵化，取食果肉。本项目基于寄主调查和卵形态比较推测其它几种芋果蝇是否转主寄生并采用卵多型策略，对确定为多型的物种，通过多因子实验确定其环境预示因子。果蝇卵丝是上皮图式和形态建成研究的重要模式系统，芋果蝇卵丝多型将为基于相同遗传背景解析图式和形态发生间的关联提供理想的研究模式。

Polymorphism is phenomenon that the same genotype produces two or more discrete phenotypes in response to environmental cues. Accurate prediction of future environment by factors acting as cues is critical for maintenance of polyphenism. Environmentally induced alterations in phenotypes of polyphenic organisms exhibit profoundly important functional, anatomical, and behavioral differences going far beyond superficial modifications of an otherwise genetically determined form. Ecological developmental studies with polyphenic organisms have important implications for the philosophy and practice of developmental biology. We found in our previous field investigation in Baoshan, Yunnan Province, that the drosophilid species, Colocasiomyia hailini, evolved a seasonally polyphenic egg filaments (dorsal appendages of egg shell) on its host plant, Rhaphidophora decursiva (this is for the first time that polyphenism during egg stage is found in insects): The female adults of C. hailini lays their eggs into the host inflorescences. Eggs of the summer generation(s) of this species are characterized by short filaments, and the 1st instar larvae hatched soon after oviposition and feed on the spathe of the host plant; however, eggs of the autumn (i.e., overwintering) generation of the same species are characterized by long filaments, with the 1st instar larvae dose not hatch until the dehiscence of the host infructescences – they then hatched and feed on mature pulp of the host. This project is proposed to determine whether several other Colocasiomyia species are heteroxenous and polyphenic in light of egg filaments, via filed investigation and morphological comparisons. For all species proved to be polyphenic in egg filaments, environmental cues triggering the developmental switch will be determined via multiple factor experiment. As Drosophila egg filaments (i.e., the dorsal eggshell structures) has emerged as an outstanding model for tubulogenesis, the egg filament polyphenims found in Colocasiomyia species are expected to provide an excellent system for studying the link between patterning and morphogenesis.