First empirical evidence of naturally occurring androgenesis in vertebrates.

Librarian's Comment : he transmission of maternal chromosomes to the offspring is generally considered an essential aspect in the reproduction of all vertebrate species. More recently, offspring consisting only of paternal chromosomes (androgenesis) has been artificially generated. Although conceptually important, such androgenetic organisms were the result of experimental manipulation of oocytes or embryos, and it was widely believed that they did not occur under natural circumstances. That has changed, with the first report of a naturally occurring androgenetic vertebrate.
In this paper, the authors describe the identification of a naturally-occurring fish (Squalius alburnoides) that only contains chromosomes inherited from the father. In this organism, the maternal genetic contribution is restricted to the mitochondrial DNA. Exactly how this remarkable event took place is still unknown. We can consider two main possibilities: either the fertilized oocyte had no maternal chromosomes, or the paternal chromosomes managed to exclude their maternal counterparts from contributing to the embryo. Although a rare event (1 out of 261 sampled fish), this first report of natural vertebrate androgenesis opens new fundamental questions on the role of male genetic contribution during embryogenesis.
Published in : Royal Society open science
Authors : Morgado-Santos M, Carona S, Vicente L, Collares-Pereira MJ

Abstract : Androgenesis among vertebrates is considered a rare phenomenon, with some cases reported so far, but linked to experiments involving gamete manipulation (artificial androgenesis). Herein, we report the first empirical evidence of the natural occurrence of spontaneous androgenesis in a vertebrate, the Squalius alburnoides allopolyploid complex. A genetically screened random sample of a natural population was allowed to reproduce in an isolated pond without any human interference, and the viable offspring obtained was later analysed for paternity. Both nuclear and mitochondrial markers showed that the only allodiploid fish found among all the allotriploid offspring was androgenetically produced by an allodiploid male. This specimen had no female nuclear genomic input, and the sequence of the mitochondrial fragment examined differed from that of the male progenitor, matching one of the parental females available in the pond, probably the mother. The possible role of androgenesis in the reproductive dynamics of this highly successful vertebrate complex is discussed.

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