The results of the study show that the ability to form finite-like structures
Zebrafish belong to the teleost lineray-finned fish. The teleosts include about 30,000 species, in particular goldfish, salmon, eels, flounder, clown fish, puffer, and catfish. There are more types of teleosts than all birds, mammals, reptiles and amphibians combined. Nevertheless, despite the large number of species and a wide range of shapes, sizes, and habitats, the pectoral fin of teleosts hardly changes.
The transition from fin to limb involvesdevelopment of the ancestral fin, many bones appear in it, which articulate with each other. From the same ancestral initial state, the fins of the body were reduced and simplified, so that the articulation disappeared.
This structure allowed the researchers to determine which aspects of development are unique limbs and which features are common to the fins and limbs of teleosts and tetrapods.
Study co-author Katrin Henkefrom Boston Children's Hospital performed direct genetic screenings for random DNA mutations and for genes that control the formation of the fin skeleton.
When the mutation caused interesting changes inthe skeleton of a zebrafish, researchers genetically mirrored it to determine which genes were affected. So they discovered that mutations in the waslb and vav2 genes cause the fin phenotype. This was an amazing discovery, as it was previously known that these genes do not play a role in the formation of body structure.
Histological analysis showed that the new bones had a muscular attachment that is widely found in limb bones but not in the fin.
Body fishes have no muscles attached to their bones.Instead, bones provide intermediate support in the fin, and muscles run directly from the shoulder to the bony rays of the fin. The new bones are fully integrated into the fin, complete with joints for articulation and attachment to the fin muscles.
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