Abstract
IN viviparous toothcarps parthenogenesis has been described in Lebistes reticulatus 1,2 and Xiphophorus helleri 2, while in this species also some cases of development of ovarial teratomas, caused by pathological parthenogenesis, are known3. In addition to these cases we observed a new one, namely in Heterandria formosa. It concerns a female isolated immediately after birth and consequently free from any contact with the male sex. After reaching a length of 27 mm. the virginal animal dropped 4 young fishes, all female. After this the animal became pregnant twice again, resulting in the birth of 6 and 10 young fishes, respectively, also exclusively female. For microscopic confirmation of the virginity the ovarial sperm chambers were examined, no spermia being observed. This finding ruled out self-fertilization, a phenomenon incidentally found in viviparous Cyprinodonts and explained by the presence of a bisexual gonad producing oocytes as well as spermia. As in the cases already described2,3, an infection process caused by the Phycomycete Ichthyophonus hoferi was present in the cranial part of the ovary and in the adjacent regions. If an extensive process had been localized in the caudal parts of the ovary and near the junction between ovary and oviduct, birth would undoubtedly have been prevented. The young females appeared without an exception to be haploid.
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References
Spurway, H., Nature, 171, 437 (1953).
Stolk, A., Nature, 181, 1660 (1958).
Stolk, A., thesis, Utrecht (1950); Proc. Kon. Ned. Akad. Wet. Amsterdam, C 56, 28 (1953); Nature, 183, 763 (1959).
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STOLK, A. Pathological Parthenogenesis in a Viviparous Toothcarp. Nature 191, 507 (1961). https://doi.org/10.1038/191507a0
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DOI: https://doi.org/10.1038/191507a0
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