WARNING: GRAPHIC (but educational) – A throwback to our research on Spotted Gar (Lepisosteus oculatus) ecology in 2011, here’s an impromptu video on sex determination of the species.
In order to better understand species’ population and life history characteristics (and inform conservation and management), we need to know its size and age structure, as well as variation of that structure between males and females. In general, the sex of gars cannot be determined externally, therefore a population sample is dissected for internal examination. We used other structures of the fish (otoliths, rays, bones, etc) for additional analyses.
Ferrara & Irwin 2001
A Standardized Procedure for Internal Sex Identification in Lepisosteidae http://bit.ly/1AhB4Et
Life history, growth, and genetic diversity of the spotted gar (Lepisosteus oculatus) from peripheral and core populations http://bit.ly/1DdgomL
Illinois Department of Natural Resources (IDNR) biologist Frank Jakubicek holds up the Spotted Gar (Lepisosteus oculatus) specimen found in the North Branch Channel of the Chicago River in September 2014. Photo by IDNR (used with permission).
Earlier this fall (September 2014) during a routine survey on the lookout for Asian carp (Bighead and Silver Carps), Illinois Department of Natural Resources fisheries biologists instead found a Spotted Gar (Lepisosteus oculatus) in the North Branch Channel of the Chicago River. This marked the first finding of the species in the Chicago Area Waterways System (CAWS), and northwestern-most occurrence of the species in Illinois (and the Great Lakes region).
As you can imagine, we were quite excited to get involved and expound upon the implications of this find! In preparation for an upcoming more detailed commentary and new entries (finally!), we are posting some links to the media accounts of the find, as well as the National Geographic blog by Primitive Fishes author Solomon David. More to come!
Here’s a quick shot of one of the gar specimens we donated to Shedd Aquarium; this specimen is on exhibit (along with a Shortnose Gar Lepisosteus platostomus) in the recently renovated “At Home on the Great Lakes” Gallery!
After a long hiatus due to our first field season (studying migratory northern pike populations in northern Wisconsin), we will be picking back up with updates in the near future! Updates will be coming from various research and other media sources, as well as our base of operations in both Chicago, IL and Detroit, MI. Lots of exciting things on the horizon, so please keep checking back!
Until next time, here is a photo of a tropical gar (Atractosteus tropicus) which is now on exhibit at Shedd Aquarium in Chicago. The tropical gar is one of two tropical members of the family Lepisosteidae (gars), and ranges from Mexico to Costa Rica. These fish are aquacultured in much of their range both as food fish and to restock dwindling wild populations. You can see these fish on exhibit in the “Islands & Lakes” gallery of Shedd Aquarium as well as at the Belle Isle Aquarium in Detroit, MI. These particular fish were also part of gar research by PrimitiveFishes.com co-authors Solomon David and Richard Kik IV.
-COELACANTH! Great article on a recently published study on the coelacanth! The genome of this “living fossil” was recently sequenced and analyzed to investigate questions about the vertebrate water-land transition (adaptations from water-to-land) and comparative rates of genome evolution. The coelacanth was shown to have extremely slow rates of change in its genome, and comparative analysis of the lungfish showed that the lungfish is the closest ancestor of the tetrapods.–
Apologies for the lack of updates on this project and many others, things have been quite hectic over the past couple months with new research projects, a job transition, and more. Here is the semi-final stage of the alligator gar head project, and it will remain at this stage for a while until some other pieces of the final project can be brought together. After defrosting the gar and prying the jaws open, it was preserved in a bucket of formalin for several days. Once formalin preservation was complete, the head was removed and soaked in water for approximately 24 hours (to reduce amount of formalin). Finally, the head was dried by sitting in the sun/air-dried for several days. The final product is what you see here; the photo was taken with Instagram, which I have been experimenting with with several primitive fishes as subjects…album coming soon; and you can see some other photos on our facebook page.–
-In continuation of the alligator gar head/skull project, here are some photos of phase 2. The head has completely thawed, which causes the muscles and joints to relax and allows for the jaws to be opened (not without some prying however). The following series of photos shows various shots of the thawed alligator gar head before entering phase 3.
Here is a shot of the fully thawed head:
A posterior shot of the head, showing muscle, nerve, and bone detail:
Dorsal shot of the head; note the distinct bony plates comprising the skull:
A shot of the head with jaws pried open; note the prominent secondary row of teeth in the upper jaw, which is characteristic of the genus Atractosteus:
Straight into the mouth of the beast. Note the rounded forked tongue; the indentation allows for adjustment of prey fishes to go down head first:
For scale (no pun intended!) you can compare to the size of my hand:
-Following the recent buzz over the giant alligator gar caught in Texas (see previous post) and finally having a small portion of free time while preparing the lab for more gar work, I decided to begin a small project I’ve had on the table (or in the freezer) for a couple years now. Phase 1 is defrosting a ~14″-long alligator gar (Atractosteus spatula) head which I acquired from colleagues while visiting Nicholls State in Lousiana back in 2010. I’ll do my best to keep an ongoing update on the project…for now I’m hoping this head will defrost properly over the next couple days before Phase 2!–