|Topminnows and killifishes are small, usually elongate fishes (except the diamond killifish) occurring in both freshwater and marine environments. They are extremely tolerant to a variety of temperatures and salinities. Most species exhibit sexual dimorphism. Males usually have a larger anal fin and deeper, brighter colors and markings than the females. Killifishes are usually distinguished by their flattened heads, lack of a lateral line, abdominal pelvic fins and oblique sloping mouths. Many are freshwater, but some are found in brackish and marine waters. They are popular in the aquarium industry and are also used as bait under the name "mudminnows".