Small, Live-bearing Fish

     When I was about 12 years old, I bought a half dozen guppies, three males and three females.  I put them in a one-gallon jar with some algae as a natural green in that jar.  I fed them the usual dried tropical fish food and changed their water every so often.  And, in spite of their small container, the females gave live birth, though most of the babies were eaten by the adult guppies.  At night, I would light the light over the guppy jar and watch those small fish go about their daily lives.  The most interesting part of their lives was the males courting and inseminating the females.  Each male swam back and forth in front of a female with jerky motions to show off the iridescent colors of his flanks.  Then he would quickly rush in to inseminate her. 
     There are three kinds of small, live-bearing fish that are abundant in the wild, related to each other, that I find to be interesting, and bred for the fresh water aquarium trade.  They are common guppies, mosquito fish and dwarf live-bearers.  Each male of these species has an anal fin that is curled into a tiny tube that directs sperm toward the dark spot at each female's anal fin.  That also is where the tiny, free-swimming young exit their mothers' bodies.  Larger females of each species can deliver up to 40 young in a brood, and each female averages about one brood a month.  The young mature in about two months. 
     All three of these species are much alike in size, shape, and habits.  They all have body colors that allow them to blend into their habitats so they are not so easily seen by predators.  Each species has large eyes to find their food items of small invertebrates in sometimes murky water.  Individuals of all three live a couple of years, if they're lucky; many kinds of fish and other animals in the wild eat them.  All species swim in noticeable schools of themselves alone.  And all species are fresh water fish that don't tolerate cold weather.
     Guppies are the most popular of tropical fish in aquariums because they are hardy, adaptable and entertaining, and the males have bright colors on their sides, though females are plain beige all over.  Therefore, they are the best known of these three fish species.  Female guppies can be an inch and a half long, while males are about an inch. 
     Guppies are originally from the backwaters of small, shallow waterways in northeastern South America where it is always warm, hence this fish's intolerance to cold.  Today guppies are in aquariums all over the world and many fancy, even more colorful, breeds of them have been developed over the years.  And today guppies have been introduced into the wild in many tropical places throughout the world.  They are quite successful as a species because of their ability to adapt to varied habitats and conditions.
     Male and female mosquito fish are both plain beige or olive.  Females can be close to two inches in length while males are about an inch long.  Their original range is the Atlantic Coastal Plain between the Appalachian Mountains and the Atlantic Ocean from Delaware to Florida and west south of the Appalachians to the southern part of the Mississippi River and its southern tributaries.
     Mosquito fish live in the shallows of warm, quiet waters of springs, waterways with slow currents and impoundments.  This species specializes in consuming mosquito larvae, hence their common name and the reason they have been introduced all over the world; to control mosquito populations.  They don't make good aquarium fish because they are aggressive and can be destructive to other kinds of small fish in an aquarium.
     Male and female dwarf live-bearers are light-gray all over with a horizontal, black line on each flank.  This is the smallest native fish species, in fact, the smallest vertebrate species, in North America.  Females may reach an inch long while their mates reach about a half inch.  They live in shallows with much aquatic vegetation in wetlands, ponds and slow-moving waterways from South Carolina to Florida and along the Gulf Coast to Louisiana.  They are shy, inoffensive little fish that do well in aquariums with other types of small fish.
     Whether the reader has seen these small fish in the wild or in aquariums or not, it's neat to know they exist in the wild and have been domesticated for aquariums and to be introduced in warmer areas around the world.  They are handsome, little fish with interesting life histories, fish well-worth knowing in the wild or in aquariums.