Hungarian ichthyologists were able to obtain viable hybrids sturgeon and Belonosov. Previously this was considered impossible, because the evolutionary line of these fish sold 184 million years ago. In the journal Genes , the researchers suggestthat the reason for this biological paradox can be doubling chromosomes in the early stages of the evolution of sturgeon and their slow evolution. However, if hybrids of sturgeon and Belonosov of any practical use is unclear.
The detachment sturgeon (Acipenseriformes) two modern family: sturgeon (Acipenseridae) and Belonosova (Polyodontidae). The first are widely known for sturgeon, and the second is the American paddlefish (Polyodon spathula), and a newly recognized extinct Chinese the Chinese paddlefish (Psephurus gladius).
Although different species of sturgeon well interbreed among themselves and produce fertile offspring, all attempts to obtain hybrids with villanosam ended in failure. This is not surprising, given that the evolutionary line of the two families diverged about 184 million years ago. In addition, differ markedly in their morphology and way of life: if the active sturgeons predators, American vislonosy are filter feeders, feeding on plankton.
The Hungarian team of ichthyologists led Jeno Khaldi (Jenő Káldy) from the Research center of fisheries and aquaculture in Szarvas used a sperm Belonosov in the experiment on reproduction ofn sturgeon (Acipenser gueldenstaedtii). The aim of the scientists was to run genagent — the process by which the sperm penetrates the egg and stimulates its division, but its genetic material is not involved in the development of the embryo.
Sperm Belonosov was used for negative control as the team members were firmly convinced that she is not able to fertilize eggs of sturgeon. However, the surprise of the scientists processed her eggs began to develop and gave rise to hybrid fry. This is the first known case of hybridization of sturgeon and Belonosov.
To confirm the results, the researchers repeated the experiment. This time they processed the eggs of females of the three sturgeon sperm of four males Belonosov. The success of fertilization amounted to 86 to 93 percent and up to thirty age lived 62-74 percent hatched fry. A year later part of the fry have reached a weight of one kilogram.
sturgeon is tetraploid, that is, it is not two sets of chromosomes, but four. The crossing of this species with diploid paddlefish has led to unusual distribution of parental genomes. Part of a hybrid species received from his mother two sets of chromosomes from the father and one (triploidy). Others got four sets of maternal chromosomes and one paternal (pentaploid). The appearance of these fish differed significantly: pentaploid was more like a sturgeon, and triploidy was something of a cross between sturgeon and paddlefish.
The hybridization of species that have independently evolved over hundreds of millions of years, it seems something incredible from a biological point of view. According to the authors, it was made possible by two factors: the doubling of the genome in the early stages of evolution of the detachment and extremely slow evolution of sturgeon. The researchers predicted that vislonosy will successfully interbreed not only with then sturgeon, but also with other types of fish. However, it is unclear what practical benefit the cultivation of such hybrids and whether they are able to reproduce.
Ecological analogues sturgeon existed about 300 million years ago. To such conclusion paleontologists carefully examining remains of a small ray-finned fish Tanyrhinichthys mcallisteri. Previously it was thought. she was a predator-type zaidziam pike, however, the new evidence indicates that she was feeding as sturgeon, patrolling the bottom of ponds in search of prey.
Sergey Knee High