Monday, December 29, 2008

i BRAKE for Gasterosteus aculeatus

My study species is Gasterosteus aculeatus -- more commonly known as the threespine stickleback fish. While this fish is small in size (an average of 6 cm standard length), observing stickleback up close in their underwater habitats (marine harbors. sloughs, and lagoons or freshwater streams and lakes) reveals biologically relevant information regarding social behaviors, sensory systems, life history strategies, and antipredator morphology. On a more practical note, stickleback are amenable to laboratory conditions whether wild-caught or lab-reared -- they occupy little space and, under the appropriate conditions, readily perform many of the behaviors observed in the field. Although the ability to study stickleback under laboratory conditions has its perks (controlled abiotic and social environment, drier, fewer mosquitoes...), observing stickleback in the wild is an entertaining and rewarding experience both in terms of the opportunity to enjoy the great outdoors and the ecologically/evolutionarily relevant data to be uncovered. My own interests in stickleback regards variation in mating behavior and reproductive tactics within and among populations -- more on this at a later date...

3 threespine facts:

  • Threespine sticklebacks have three dorsal spines (hence the name "threespine sticklebacks") PLUS many populations also have two pelvic spines. All of these spines can be held erect or collapsed down flat against the body and are utilized in antipredator defense and to signal aggression between individuals.

  • Threespine stickleback have a holarctic distribution (only two subspecies range south of northern North American, northern Asia, and northern Europe). They like the cold water -- which means snorkeling in a drysuit and several layers of warm clothing is usually a prerequisite to observe stickleback in their natural habitats.

  • Anadromous stickleback include those populations that live in a marine environment the majority of their 1-3 year lives, only entering freshwater during the spring and summer to breed. Anadromous populations are very similar both behaviorally and morphologically across the Baltic, Atlantic and Pacific. Freshwater populations include those populations restricted to freshwater environments -- streams, rivers, lakes. These populations are most likely descendants of anadromous stock that became restricted to freshwater environments via changes in physiology and/or geographic barriers over long periods of time. In comparison to anadromous populations, behavioral repertoires, life histories, and morphologies vary greatly among freshwater populations -- so much so that biologists and taxonomists had described many freshwater populations as different subspecies until it was decided that the vast majority of stickleback populations were too closely related (in terms of time since geographic isolation) to rank as subspecies. Now the vast majority of threespine populations fall under the subspecies Gasterosteus aculeatus aculeatus.

more threespine facts, biology and musings to come...