The evolution of the sex chromosomes
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1. The majority of the Mantoidea have anXO : XX sex-determining mechanism like that found in the other Orthopteroid groups. TheX seems to be without exception a mediocentric chromosome.
2. In one group of genera (subfamily Mantinaesensu stricto) anX 1 X 2 Y :X 1 X 1 X 2 X 2 mechanism has been developed. It may reasonably be assumed that this mechanism arose in the first place by a mutual translocation as a result of which a pair of autosomes became involved in the sex-determining mechanism.
3. The diploid chromosome numbers of the Mantids vary from 15 to 29 in the fifteen species which have been investigated. All theX 1 X 2 Y species studied (with the exception ofSphodromantis viridis) have 27 chromosomes.S. viridis has only 23.
4. In all the species studied meiosis seems to be of an anomalous type which differs in important respects from the process found in the Orthoptera Saltatoria. It seems impossible to determine by purely cytological means whether crossing-over occurs, since chiasmata are not seen.
KeywordsMeiotic Division Polar View Thin Thread Autosomal Bivalents Milk Bottle
- Asana, J. J. (1934). Studies on the chromosomes of Indian Orthoptera. IV. The idiochromosomes ofHierodula sp.Curr. Sci. 2, 244–5.Google Scholar
- Asana, J. J., Makino, S. &Niiyama, H. (1938). A chromosomal survey of some Indian insects. I. Morphology of the chromosomes in eight species of the Locustidae.J. Fact. Sci. Hokkaido Univ. Ser.VI,3, 211–34.Google Scholar
- Giglio-Tos, E. (1927). Mantidae (Das Tierreich,50).Google Scholar
- —— (1931). Chromosomes of three species of Mantidae.J. Morph. 52, 523–33.Google Scholar
- Klingstedt, H. (1933). Chromosomenstudien an Neuropteren. I. Ein Fall von heteromorphen Chromosomenpaaren als Beispiel vom Mendeln der Chromosomen.Mem. Soc. Fauna Flora Fenn. 10, 2–11.Google Scholar
- Morse, M. (1909). The nuclear components of the sex-cells of four species of cock-roaches.Arch. Zellforsch. 3, 483–520.Google Scholar
- Muller, H. J. (1940). Bearings of the Drosophila work on systematics. (Article inThe New Systematics, edited by Julian Huxley, Oxford Univ. Press.)Google Scholar
- Oguma, K. (1921). The idiochromosomes of the mantis.J. Coll. Agric. Sapporo,10, 1–27.Google Scholar
- Wenrich, D. H. (1916). The spermatogenesis ofPhrynotettix magnus with special reference to synapsis and the individuality of the chromosomes.Bull. Mus. comp. Zool. Harv. 60, 57–135.Google Scholar
- White, M. J. D. (1933). Tetraploid spermatocytes in a locust,Schistocerca gregaria.Cytologia, Tokyo,5, 135–9.Google Scholar
- —— (1938). A new and anomalous type of meiosis in a Mantid,Callimantis antillarum Saussure.Proc. Roy. Soc. B,125, 516–23.Google Scholar
- —— (1940a). The heteropycnosis of sex chromosomes and its interpretation in terms of spiral structure.J. Genet. 40, 67–82.Google Scholar
- —— (1940b). The origin and evolution of multiple sex chromosome mechanisms.J. Genet. 40, 303–36.Google Scholar
- Zeuner, F. E. (1939).Fossil Orthoptera Ensifera. London: British Museum, Natural History.Google Scholar