In contrast to mammals and birds,fish display an amazing diversity of genetic sex determination systems,with frequent changes during evolution possibly associated with the emergence of new sex chromosomes and sex-dete...In contrast to mammals and birds,fish display an amazing diversity of genetic sex determination systems,with frequent changes during evolution possibly associated with the emergence of new sex chromosomes and sex-determining genes.To better understand the molecular and evolutionary mechanisms driving this diversity,several fish models are studied in parallel.Besides the medaka(Oryzias latipes Temminck and Schlegel,1846)for which the master sex-determination gene has been identified,one of the most advanced models for studying sex determination is the Southern platyfish(Xiphophorus maculatus,Günther 1966).Xiphophorus maculatus belongs to the Poeciliids,a family of live-bearing freshwater fish,including platyfish,swordtails and guppies that perfectly illustrates the diversity of genetic sex-determination mechanisms observed in teleosts.For X.maculatus,bacterial artificial chro-mosome contigs covering the sex-determination region of the X and Y sex chromosomes have been constructed.Initial molecular analysis demonstrated that the sex-determination region is very unstable and frequently undergoes duplications,deletions,inversions and other rearrangements.Eleven gene candidates linked to the master sex-determining gene have been identified,some of them corresponding to pseudogenes.All putative genes are present on both the X and the Y chromosomes,suggesting a poor degree of differentiation and a young evolutionary age for platyfish sex chromosomes.When compared with other fish and tetrapod genomes,syntenies were detected only with autosomes.This observation supports an independent origin of sex chromosomes,not only in different vertebrate lineages but also between different fish species.展开更多
We present a compilation of all myxomycetes recorded from Papua New Guinea(PNG)and New Caledonia(NC).Specimens were collected during field trips in September 1983–January 1984 to both territories and in August 1991,O...We present a compilation of all myxomycetes recorded from Papua New Guinea(PNG)and New Caledonia(NC).Specimens were collected during field trips in September 1983–January 1984 to both territories and in August 1991,October 2007,and April 2009 to NC.Bark and dung samples for moist chamber cultures were collected during the field trips in September 1983–January 1984(PNG and NC)and in August 1991 and October 2007(NC).In addition,information from previous publications and unpublished specimens in the herbarium at the Plant Protection Instituted in Port Moresby,PNG,are included.A total of 180 species are reported.Of the 63 species from PNG 51 are new to the country,and 123 of the 149 species from NC are new to the territory.展开更多
文摘In contrast to mammals and birds,fish display an amazing diversity of genetic sex determination systems,with frequent changes during evolution possibly associated with the emergence of new sex chromosomes and sex-determining genes.To better understand the molecular and evolutionary mechanisms driving this diversity,several fish models are studied in parallel.Besides the medaka(Oryzias latipes Temminck and Schlegel,1846)for which the master sex-determination gene has been identified,one of the most advanced models for studying sex determination is the Southern platyfish(Xiphophorus maculatus,Günther 1966).Xiphophorus maculatus belongs to the Poeciliids,a family of live-bearing freshwater fish,including platyfish,swordtails and guppies that perfectly illustrates the diversity of genetic sex-determination mechanisms observed in teleosts.For X.maculatus,bacterial artificial chro-mosome contigs covering the sex-determination region of the X and Y sex chromosomes have been constructed.Initial molecular analysis demonstrated that the sex-determination region is very unstable and frequently undergoes duplications,deletions,inversions and other rearrangements.Eleven gene candidates linked to the master sex-determining gene have been identified,some of them corresponding to pseudogenes.All putative genes are present on both the X and the Y chromosomes,suggesting a poor degree of differentiation and a young evolutionary age for platyfish sex chromosomes.When compared with other fish and tetrapod genomes,syntenies were detected only with autosomes.This observation supports an independent origin of sex chromosomes,not only in different vertebrate lineages but also between different fish species.
基金funding was provided to H.Kylin by the Botanical Society of Lund(the Svante Murbeck Fund)the Natural Science Society at Stockholm University。
文摘We present a compilation of all myxomycetes recorded from Papua New Guinea(PNG)and New Caledonia(NC).Specimens were collected during field trips in September 1983–January 1984 to both territories and in August 1991,October 2007,and April 2009 to NC.Bark and dung samples for moist chamber cultures were collected during the field trips in September 1983–January 1984(PNG and NC)and in August 1991 and October 2007(NC).In addition,information from previous publications and unpublished specimens in the herbarium at the Plant Protection Instituted in Port Moresby,PNG,are included.A total of 180 species are reported.Of the 63 species from PNG 51 are new to the country,and 123 of the 149 species from NC are new to the territory.
