2016-04-24 11.11.14 Mummichogs.jpg

The female mummichog in the foreground is larger but the male behind her is presently in breeding colors that make him a bit more colorful.

(Clay Wollney)

Mummichogs, also known as killifish or simply as "killies," are easily the most common fish found in the estuaries and marshes on Staten Island's shoreline.

While other members of the killifish family, especially the tropical species, are kept in aquaria for their beautiful colors, the mummichog serves much more practical purposes. From its use as bait for summer flounder and bluefish to its uses in research, the rather non-descript mummichog is much more than just an average fish.

The name mummichog comes from the language of the Narragansett people, a branch of the Algonquians. The name means "going in large groups" a reference to their schooling behavior.

Their scientific name is Fundulus heteroclitus. Fundulus means bottom, referring to the way they stay near the muddy bottoms of creeks.

A tough little fish

The mummichog is one tough little fish. Unlike many other species that can only survive in a narrow range of environmental conditions, the mummichog can tolerate a wide range of salinities, extreme temperature fluctuations, low oxygen levels and high levels of pollution. This makes it capable of surviving in a wide range of environments and hence it is more likely to endure through tough times than other fish. Indeed, mummichogs were even around in the Arthur Kill River back in the 1960s when it was one of the 10 most polluted waterways in the country.

First fish in space

Their overall hardiness make the mummichog useful in research, especially since they are also abundant in the wild and can be transported easily. They have been used in studying embryology, physiology and toxicology.

In 1973, mummichogs were the first fish to go into space as part of an experiment done on the Skylab. In this experiment, the mummichogs successful proved that fish could learn to swim in zero gravity.

Can survive in freshwater and extremely salty water

Most fish are adapted to either freshwater or saltwater and cannot survive if place in the other. Nonetheless, there are some species that can live in both fresh and saltwater. These fish are described as euryhaline and the mummichog is an excellent example.

In the open ocean, the water contains 35 parts per thousand (ppt) of salt. Mummichogs can live in anything from freshwater to a salinity as high as 110 ppt salinity, which is three times as saline as the ocean.

I've observed mummichogs in essentially freshwater streams at Snug Harbor, Arbutus Avenue and alongside the Richmond Valley train station. In some cases, they were even living alongside sunfish, which are a freshwater only species.

To discover the physiological mechanism that gives the mummichog its ability to survive in different salinities, researchers at Louisiana State University kept six wild-caught mummichogs in salt water for three months. These fish were then put in freshwater and a variety of blood and molecular samples were taken. Although the first 24 hours were a bit rough, the fish had fully recovered and had adapted to the freshwater by the end of the third day.

The researchers discovered that mummichogs produced proteins known as aquaporins that became part of the cell membranes in the gills to help pump excess water out of the cells. To accomplish this, the aquaporin-3 gene increased its activity 16 times over during the first six hours in freshwater. This is a key factor, since the major problem when fish move from salt to fresh water is that their cells will swell up with water and burst.

Similar changes throughout the body help prevent cellular damage to adapt and redesign the outer surfaces of cells for the proper water balance. In all, 498 genes were turned on or off to make the adjustment to freshwater.

Resistant to pollution

The same team from Louisiana State University also studied the effects of pollution on mummichogs at three different locations. Newark Bay was one of the locations they studied, due to high dioxin levels there. New Bedford Harbor in Massachusetts with high polychlorinated biphenyls and the Elizabeth River in Virginia with its creosote were the other two locations.

In each case, about a fifth of the fish's genes had been modified, however different sets of genes were affected in each case.

Diet includes mosquitoes

The mummichog is an omnivorous species that eats small invertebrates, as well as algae and plants. Mosquitoes are part of their diet and attempts have been made to use mummichogs to control the bugs. Back in the 1930s, the Civilian Conservation Corps dug parallel ditches in many marshlands to drain the water and provide a place for mummichogs and other fish to feed on them.