An unexpected fertilization has occurred in a fish nursery, resulting in a hybrid fish breed comprising two species which are further apart on the evolutionary tree than humans and mice.
An American paddlefish was able to fertilize eggs from a Russian sturgeon and the fascinating results were posted in the Genes journal.
Russian sturgeons are famous for their eggs or caviar, a delicacy found in expensive restaurants around the world.
They can get up two meters long and 100kg in weight and are bottom dwellers which prey on crustaceans and smaller fish. Their snouts are unusually short and rounded compared to other variations of sturgeon. Their backs are covered with an array of scutes – scale-like protrusions.
American paddlefish are filter feeders – they sustain themselves by sucking up zooplankton.
Shark-like in its body appearance, the paddlefish has a strange and overly big snout which makes up a third of its total length.
In summary, both fish are pretty strange looking species. And so it’s not surprising that their offspring, the sturddlefish, are also rather prehistoric looking.
Comprising of the gametes (a gamete is a reproductive cell containing only one set of dissimilar chromosomes, or half the genetic material needed to make up a complete organism) from seven individual fish, the offspring exhibited survival rates of 62% to 74% beyond the initial 30-day period.
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Around about 100 of the baby sturddlefish were produced, with a range of different features – some looked more like sturgeon, some more like paddlefish, and others exhibited various different traits from both species.
Two endangered fish species
Both sturgeon and paddlefish are threatened by overfishing, pollution and habitat loss. The original aim of the scientists at the Research Institute for Fisheries and Aquaculture in Hungary was to see if they could boost the species numbers by introducing asexual reproduction.
Due to the great evolutionary distance between the two fish, the researchers certainly never expected a hybrid to materialize – despite the relative similarities in looks of the fish.
These similarities include their large size and that they are both among the longest-living fish species on our planet.
However, they exist in different parts of the world and last shared a common ancestor in Jurassic times — which made them unlikely candidates for cross-breeding.
Hybrid species are not encouraged by science and the current offspring are sterile, so no further breeding is planned and the sturddlefish may end up being relegated to the history books rather than appearing in nature in the future.
IMAGE FEATURED: Flórián Tóth