severely polluted and oxygen-deprived waterways, such as the Elizabeth River in Virginia and, in New Jersey, the Hackensack River and the Arthur Kill. A 2008 Virginia Institute of Marine Science report stated that 38% of mummichogs from Elizabeth River had cancerous lesions, and "more than half had pre-cancerous lesions. That was largely due to high levels of polycyclic aromatic hydrocarbons". Killifish eggs are used in developmental studies and when teaching embryology because the eyes, the beating heart, and the different stages of ontogenesis can be easily examined. Embryos are also extremely durable and easy to manipulate in the laboratory. Mummichogs were the first fish sent to space. In 1973 a couple of them were flown in a plastic bag aquarium aboard Skylab, during the Skylab 3 mission. In the absence of gravity the fish at first exhibited an unusual swimming behavior: they constantly pitched forward and therefore described tight circles. However, by day 22 of the mission they swam normally. Fifty eggs at an advanced stage of development had also been taken on board, and 48 of them hatched during the flight. The hatchlings swam normally. More experiments with mummichogs in space followed as part of the Apollo-Soyuz Test Project and as part of a biological package aboard the Bion 3/Kosmos 782 satellite. See also Japanese rice fish (Oryzias latipes), first fish to breed in space in 1994 References External links Fishbase entry (with image) Fundulus Fish of the Western Atlantic Fish of the Eastern United States Fish of Canada Fauna of Atlantic Canada Fauna of the Northeastern United States Least concern biota of the United States Least concern biota of North America Fish described in 1766 Taxa named by Carl Linnaeus