Abstract
Cytogenetics, which is considered a fundamental tool to understand basic genetic and genomic issues of species, has greatly contributed to the description of polymorphisms both at inter- and intra-specific level. In fact, cytogenetics was one of the first approaches used to propose Anastrepha fraterculus (Diptera: Tephritidae) as a complex of cryptic species. Different morphological variants of sex chromosomes have been reported among Argentinean populations of Anastrepha fraterculus. However, since this high structural variability in sex chromosomes does not pose a reproductive barrier, their role in speciation is yet to be unveiled. This review provides an update on general aspects of cytogenetics in Argentinean Anastrepha fraterculus populations, focused on the prevalence of X-Y arrangements.
Highlights
Studies based on genetic differentiation, karyology, morphology, reproductive compatibilities combined with bionomic parameters, eggshell morphology and some aspects of early embryogenesis of samples from northern and southern Brazil have identified at least four entities of the A. fraterculus complex: A. sp.1 aff. fraterculus, A. sp. 2 aff. fraterculus, A. sp. 3 aff. fraterculus, and A. sp.4 aff. fraterculus
By using a specific probe designed from a region of A. fraterculus 18S rDNA (Figure 3), in our lab we have observed a pattern of signals equivalent to the one previously described by Goday et al (2006)
We have performed a simultaneous analysis of mitotic and polytene nuclei of Argentinean A. fraterculus, and observed that neither the number of polytene chromosomes nor their banding patterns differentiate males from females (Giardini et al 2009a). This suggests that in A. fraterculus, as well as in other tephritid flies (Zacharopoulou 1987, Mavragani-Tsipidou et al 1992, Zacharopoulou et al 2011a, 2011b, Garcia-Martinez et al 2009), the sex chromosomes do not form polytene chromosomes. This finding was tested by fluorescence in situ hybridization (FISH) experiments using the specific 18S rDNA probe in polytene chromosomes, which revealed a hybridization signal in a region of granular and uncondensed heterochromatin (Figure 5) that corresponded to the nonpolytene sex chromosomes (Giardini et al 2012)
Summary
Sex chromosomes in mitotic and polytene tissues of Anastrepha fraterculus (Diptera,Tephritidae) from Argentina: a review. Academic editor: M.T. Vera | Received 16 June 2015 | Accepted 2 September 2015 | Published 26 November 2015 http://zoobank.org/3A166604-2656-4743-80C8-631C2EA939E8
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