The researchers saw the giant danio as the physiological model and began a series of experiments on differences in muscle growth between the fish. In this two-phased experiment, they discovered that the giant danio can keep growing even into adulthood, but the zebrafish stops growing. The giant danio can get bigger because it exhibits a type of muscle growth that is different from the zebrafish.
“One of these species either lost or gained the ability to continuously grow, but most likely, the zebrafish lost it?Biga explained. Because genes are the key, the zebrafish’s mapped genome will be invaluable in finding what is different about the danio’s genetic pathways that allow it to keep growing.
Study: Phase I - First four weeks of life
In the first phase of the study, the researchers tracked the size of the fish from the time they hatched through the first four weeks of their larval stage. They found that the two species were the same size at hatch. By the end of week one, the giant danio was significantly larger and remained so. This result was not surprising, since the giant danio is so much larger at adulthood, about twice as large. But the study was the first to report the early larval growth of these species, the authors said.
The researchers also documented muscle changes over the first four weeks in the fleshy portion of the fish’s midsection, known as the myotome. They measured growth in length and width and tracked the number and size of muscle fibers, and found that the fish employ different methods of growth.
“Muscle growth in vertebrates is defined as being either determinate or indeterminate,?the authors wrote. “Animals such as mammals exhibit determinate growth, in which there is a finite size. In contrast, many fish species growth is indeterminate, in which there i
Source:American Physiological Society