Saturday, June 16, 2012

Rainbow Darter

Rainbow darter female
Jeff Barrow of Missouri River Relief braved the waters of Bull Creek on Monday and came up with this monster of the deep, some type of darter.  My initial efforts to identify it on the web failed and I appealed to a higher power, Mike Kromrey who pointed me to rainbow and orange throat darters.

I went through lots of pictures before I found a match, the common rainbow darter, Etheostoma caeruleum.  I should have figured the problem out sooner.  I had looked at both species on the web with no matches. It so happens that most web pages show only showed the colorful males while the females get no respect, as Barb has told me for years.

Orange throat darter female
Rainbow darters are one of the most common small species in our Ozark streams.  They prefer small to middle sized flowing streams, collecting in riffles with gravel.  A previous study of Bull Creek populations showed that rainbow darters were much more common than orange throat darters.

The rainbow and orange throat females look similar with a few distinguishing features.  The rainbow has more prominent vertical bars on the rear half which extend to the top.  They also have an orange tint to their anal fin.
Rainbow darter- male
Orange throat darter- male

"Breeding takes place in riffles from mid April to mid May. Females deposit three to seven eggs in the gravel and the male fertilizes them. This can be repeated many times over several days during their breeding season. A single female can lay about 800 eggs in a single breeding season." *
This brings a question to mind.  The bright coloration of males in many species of birds and butterflies is thought to improve the males success in breeding, identifying the species and serving as an advertisement saying "Look how pretty I am.  Don't you want some of my genes?"  This tactic comes at a cost, the loss of camouflage and thus increased exposure to predators.   With the male darter seeking out and fertilizing eggs deposited in the gravel, what advantage does the bright coloration have to them?  Only the darter knows.

*  The Ohio DNR website is listed under resources as a good site for the identification of many Missouri fish species. 

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