called red worms), but also eats other mayflies. They crawl over the sand like crabs as they hunt prey. Eggs are deposited in the sand and lay dormant over winter. They hatch in May to June. The larvae grow quickly, completing their life cycle in one summer and will emerge in August as adults. Unlike some mayflies for which they are famous, this species does not emerge in masses covering bridges and roadways.
Ohio Shrimp (Macrobrachium ohione)
The genus Macrobrachium is known as the “large river shrimps.” Most are marine, but four species enter freshwater. Only one species, the Ohio shrimp, is found in Missouri. This species enters freshwater rivers of the Eastern Seaboard from Virginia to Florida and of the Gulf Coast from Alabama to Texas. In the interior United States it has been found in the Mississippi and Ohio river systems from Oklahoma to Ohio. It has also been found in the lower Missouri River where it is extremely rare.
Prior to 1940, the Ohio shrimp population was so abundant it supported a commercial fishery in the Mississippi River below St. Louis. Towns along the river, such as Cape Girardeau, often had “shrimp fries.” By the late 1940s the species became rare in the Mississippi River above Cairo. The last known collection of Ohio shrimp from this reach was at Cairo in 1962.
However, they were rediscovered by MDC scientists in 1991 from the Mississippi River near Cape Girardeau. Apparently, the species persisted in the river undetected in low numbers until a Mississippi River monitoring program was established at Cape Girardeau.
Ohio shrimp can be 4 inches long as adults. They are translucent when alive and have numerous brownish-orange spots or speckles covering the body. The head has a rather distinctly serrated rostrum (a spear-like protrusion projecting forward from the head). Ohio shrimp eat a variety of foods, including vegetation, invertebrates, and fish. They can quickly swim forward or backward to capture prey or avoid being eaten.
Ohio shrimp are amphidromous meaning individuals of various life stages regularly migrate between fresh and salt water. Reproduction occurs in freshwater but the young develop in saltwater. Juveniles migrate up freshwater rivers to mature, especially females. Ovigerous females (those carrying eggs) have been found in the Mississippi River near Cape Girardeau. This poses an interesting and yet unsolved mystery: If ovigerous females reproduce in Missouri, and young need saltwater to develop,