U.S. researchers John F. Switzer* and Robert M. Wood** have described a new species of darter from the Meramec River drainage of Missouri, USA. The new species has been named Etheostoma erythrozonum and is the first known fish species endemic to the Meramec River drainage. Its common name is Meramec Saddled Darter.

Etheostoma erythrozonum is a sister species of the Missouri Saddled Darter, Etheostoma tetrazonum, an inhabitant of the Gasconade River, Osage River, and Moreau River drainages. The Missouri Saddled Darter is one of several darter species endemic to the northern Ozark region of Missouri. When E. tetrazonum was first described, it was only known to exist in the

Osage and Gasconade River systems. However, within a year of its description, individuals of E. tetrazonum were identified from the Meramec River system, a tributary of the Mississippi River. Since then the distribution of E. tetrazonum has been considered to include the Meramec, Gasconade, Osage, and MoreauRiver systems.

In 1984, the first sign of E. tetrazonum actually being more than one species was found when an electrophoretic analysis unveiled considerable genetic divergence between populations of E. tetrazonum from the Meramec and Osage River drainages. This notion has now been supported by a recent molecular phylogenetic analysis of 13 populations of E. tetrazonum,

As a result, the specimens living in the Meramec River drainage have now been recognized as a separate species and the name E. tetrazonum will from now on only pertain to the specimens native to the Moreau, Osage, and Gasconade River drainages. As mentioned above, the Meramec River drainage species has been given the name Etheostoma erythrozonum.

E. erythrozonum is very similar to E. tetrazonum but without the prominent blue-green colouration. Some male E. erythrozonum darters do have a blue spinous dorsal fin base, but the blue colour is inconspicuous and never as outstanding as in E. tetrazon. (The anal fin of E. erythrozonum is also blue-green.)

Male E. erythrozonum darters sport a horizontal red-orange stripe that runs along the lower sides of the body from the pelvic fins to the anal fin with an irregular dorsal margin, while the male E. tetrazonum darter has a dorsal stripe with a well-defined dorsal margin in. Another notable difference between the two species is how E. erythrozonum has a series of irregularly shaped red-orange blotches instead of the well defined vertical bars seen on male E. tetrazonum darters.

The paper has been published here in the journal Zootaxa. Picture is Available in the online publication.

* John F. Switzer, U.S. Geological Survey, Leetown Science Center, Aquatic Ecology Branch, Kearneysville, West Virginia

E-mail: jswitzer@usgs.gov

** Robert M. Wood, Department of Biology, Saint Louis University, St. Louis, Missouri

E-mail: wood2@slu.edu