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Assigning sex to pre-adult stalk-eyed flies using genital disc morphology and X chromosome zygosity

BACKGROUND: In stalk-eyed flies (Diopsidae) the eyes and antennae are laterally displaced at the ends of elongated eyestalks. Eyespan and the degree of sexual dimorphism in eyespan vary considerably between species and several sexually dimorphic species show sexual selection through female mate pref...

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Autores principales: Carr, Martin, Cotton, Samuel, Rogers, David W, Pomiankowski, Andrew, Smith, Hazel, Fowler, Kevin
Formato: Texto
Lenguaje:English
Publicado: BioMed Central 2006
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1524940/
https://www.ncbi.nlm.nih.gov/pubmed/16780578
http://dx.doi.org/10.1186/1471-213X-6-29
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author Carr, Martin
Cotton, Samuel
Rogers, David W
Pomiankowski, Andrew
Smith, Hazel
Fowler, Kevin
author_facet Carr, Martin
Cotton, Samuel
Rogers, David W
Pomiankowski, Andrew
Smith, Hazel
Fowler, Kevin
author_sort Carr, Martin
collection PubMed
description BACKGROUND: In stalk-eyed flies (Diopsidae) the eyes and antennae are laterally displaced at the ends of elongated eyestalks. Eyespan and the degree of sexual dimorphism in eyespan vary considerably between species and several sexually dimorphic species show sexual selection through female mate preference for males with exaggerated eyespan. The genes on which selection acts to regulate eyespan remain to be identified. This could be achieved by comparing gene expression during eyestalk development in males and females if the sex of pre-adult flies could be reliably assigned. Here we describe two techniques, one morphological and one microsatellite-based, that identify the sex of stalk-eyed fly larvae and pupae. RESULTS: We showed that genital discs of the stalk-eyed fly Teleopsis dalmanni have two highly distinct morphologies, compact ("C") and lobed ("L"). Segment composition (revealed by Engrailed expression) was consistent with C morphology being typical of males and L morphology of females. We confirmed the proposed association between disc morphology and sex by evaluating the combined heterozygosity of four X-linked microsatellite markers. We demonstrated that individuals with C genital discs had hemizygous (male) genotypes while those with L discs were heterozygous (female) genotypes. Similar dimorphism in genital disc morphology was observed in eight other species spanning three representative Diopsid genera. In every case the segment composition supported C morphology being male and L morphology female. We assigned larval sex by C or L morphology and compared cell division frequencies in male and female eye-antennal discs in two species (T. dalmanni and Diasemopsis meigenii) sexually dimorphic for eyespan. The number of mitotic (anti-H3-labelled) cells did not differ between the sexes in either species. CONCLUSION: We have made novel use of two complementary techniques for identifying the sex of pre-adult stalk-eyed flies. These procedures will facilitate studies of the evolution of sexually dimorphic development in a variety of other species. Morphology and En expression in male and female genital discs are highly conserved within each genus of Diopsidae. Finally, sexual dimorphism for eyespan in two Diopsid species is unlikely to be due to an increased rate of cell division at the third larval instar in males.
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spelling pubmed-15249402006-08-01 Assigning sex to pre-adult stalk-eyed flies using genital disc morphology and X chromosome zygosity Carr, Martin Cotton, Samuel Rogers, David W Pomiankowski, Andrew Smith, Hazel Fowler, Kevin BMC Dev Biol Methodology Article BACKGROUND: In stalk-eyed flies (Diopsidae) the eyes and antennae are laterally displaced at the ends of elongated eyestalks. Eyespan and the degree of sexual dimorphism in eyespan vary considerably between species and several sexually dimorphic species show sexual selection through female mate preference for males with exaggerated eyespan. The genes on which selection acts to regulate eyespan remain to be identified. This could be achieved by comparing gene expression during eyestalk development in males and females if the sex of pre-adult flies could be reliably assigned. Here we describe two techniques, one morphological and one microsatellite-based, that identify the sex of stalk-eyed fly larvae and pupae. RESULTS: We showed that genital discs of the stalk-eyed fly Teleopsis dalmanni have two highly distinct morphologies, compact ("C") and lobed ("L"). Segment composition (revealed by Engrailed expression) was consistent with C morphology being typical of males and L morphology of females. We confirmed the proposed association between disc morphology and sex by evaluating the combined heterozygosity of four X-linked microsatellite markers. We demonstrated that individuals with C genital discs had hemizygous (male) genotypes while those with L discs were heterozygous (female) genotypes. Similar dimorphism in genital disc morphology was observed in eight other species spanning three representative Diopsid genera. In every case the segment composition supported C morphology being male and L morphology female. We assigned larval sex by C or L morphology and compared cell division frequencies in male and female eye-antennal discs in two species (T. dalmanni and Diasemopsis meigenii) sexually dimorphic for eyespan. The number of mitotic (anti-H3-labelled) cells did not differ between the sexes in either species. CONCLUSION: We have made novel use of two complementary techniques for identifying the sex of pre-adult stalk-eyed flies. These procedures will facilitate studies of the evolution of sexually dimorphic development in a variety of other species. Morphology and En expression in male and female genital discs are highly conserved within each genus of Diopsidae. Finally, sexual dimorphism for eyespan in two Diopsid species is unlikely to be due to an increased rate of cell division at the third larval instar in males. BioMed Central 2006-06-16 /pmc/articles/PMC1524940/ /pubmed/16780578 http://dx.doi.org/10.1186/1471-213X-6-29 Text en Copyright © 2006 Carr et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( (http://creativecommons.org/licenses/by/2.0) ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Methodology Article
Carr, Martin
Cotton, Samuel
Rogers, David W
Pomiankowski, Andrew
Smith, Hazel
Fowler, Kevin
Assigning sex to pre-adult stalk-eyed flies using genital disc morphology and X chromosome zygosity
title Assigning sex to pre-adult stalk-eyed flies using genital disc morphology and X chromosome zygosity
title_full Assigning sex to pre-adult stalk-eyed flies using genital disc morphology and X chromosome zygosity
title_fullStr Assigning sex to pre-adult stalk-eyed flies using genital disc morphology and X chromosome zygosity
title_full_unstemmed Assigning sex to pre-adult stalk-eyed flies using genital disc morphology and X chromosome zygosity
title_short Assigning sex to pre-adult stalk-eyed flies using genital disc morphology and X chromosome zygosity
title_sort assigning sex to pre-adult stalk-eyed flies using genital disc morphology and x chromosome zygosity
topic Methodology Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1524940/
https://www.ncbi.nlm.nih.gov/pubmed/16780578
http://dx.doi.org/10.1186/1471-213X-6-29
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