The stickleback fish, Gasterosteus aculeatus, is one of the most thoroughly studied organisms in the wild, and has been a particularly useful model for understanding variation in physiology, behavior, life history and morphology caused by different ecological situations in the wild.
On biological levels from molecular and genetic to developmental and morphological, and finally ending with the population level, it has proven far more complex than even imagined.
Studies of stickleback have provided us with a much better understanding of how organisms cope with new environmental conditions, first through acclimation over an individual's lifespan, and subsequently through adaptation of population via changes in gene form (allele) frequencies.
Given the rapidly changing global environment, this research not only provides insight into evolutionary processes, but is of practical importance in understanding how organisms will adapt to a changing world.
There are two forms of the stickleback: the oceanic and the freshwater type. The oceanic form lives in the ocean and comes into shallow estuarine or freshwater rivers and streams to breed, and has repeatedly given rise to a freshwater form that lives its entire life isolated in freshwater habitats.
Oceanic stickleback are protected by a complete set of bony lateral plates along the sides and dorsal and pelvic spines on the top and bottom of the fish. These structures help the fish survive attacks by birds and other fish-eating predators. The lateral plates develop first at the front of the fish, near the spines, and then are gradually added towards the tail until the entire side of the stickleback is covered.
Freshwater stickleback almost always evolve the loss of lateral plates, and sometimes the spines, as shown in the figure. This evolutionary change can occur very rapidly, sometimes in only dozens of years. An explanation for the loss of the bony plat
|Contact: Lily Whiteman|
National Science Foundation