Amiiformes (Bowfins)

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Amiiformes

(Bowfins)

Class Actinopterygii

Order Amiiformes

Number of families 1

Evolution and systematics

The order Amiiformes (sensu Grande and Bemis, 1998) contains one extant family, Amiidae, and three extinct families, Caturidae, Liodesmidae, and Sinamiidae.

The family Amiidae is another of the so-called living fossil families. In other words, it is a relatively basal neopterygian group with an old history (late Jurassic to present day), a formerly diverse distribution (with numerous genera and species in the Jurassic through the Eocene), and only a single extant species. The bowfin (Amia calva) is the only living species remaining from the order Amiiformes.

The Amiidae is one of only five extant families of actinopterygian fishes outside of Teleostei. Consequently, it is a family of great interest to fish systematists and evolutionary biologists. Even its most basic relationships remain controversial (i.e., is Amiidae the living sister group to Teleostei, or to Lepisosteidae?). Although there is only a single species in the family today, a rich fossil record going back over 150 million years to the late Jurassic indicates that in the past the family contained many more species, and was morphologically diverse and geographically widespread. In their revision of the Amiidae, Grande and Bemis (1998) divided the family into four subfamilies: Amiinae, Vidalamiinae, Solnhofenamiinae, and Amiopsinae. Amiopsinae was an extinct group with five valid species (some marine, some freshwater) ranging in age from late Jurassic to late Cretaceous (about 150 million to 100 million years ago). The group is known only from fossil deposits of western Europe. Solnhofenamiinae is an extinct group containing a single valid species and is known from late Jurassic marine deposits of western Europe. Vidalamiinae is an extinct group containing five genera and eight valid species (some marine, some freshwater) ranging in age from at least the early Cretaceous to the early Eocene (about 135 million to 55 million years ago). The group is known from deposits located in western Europe, North America, eastern South America, and western Africa. Amiinae is a freshwater subfamily containing two valid genera and about 11 valid species. This subfamily ranges in age from at least the late Cretaceous (about 95 million years ago) through to the present. While the twenty-first century finds this family living only in North America, fossil members are widespread throughout the Northern Hemisphere.

Taxonomy is Amia calva Linnaeus, 1766, Charleston, South Carolina, United States.

Other common names: English: Blackfish, cottonfish, cypress trout, freshwater dogfish, grindle, grinnel, marshfish, mudfish, scaled ling, speckled cat; French: Choupique, poisson de marais.

Physical characteristics

The Amiidae are uniquely characterized by the condition of their caudal vertebral region. Most of the caudal centra are

both solidly ossified and diplospondylous; in other words, the neural and haemal arches occur only on every other centrum rather than on every centrum. Like all halecomorphs, amiids have a peculiar double jaw articulation in which the jaw suspension bones articulate with the lower jaw at two separate places rather than one.

Amia calva is characterized, among living fishes, partly by its long, bow-shaped dorsal fin; hence the common name "bowfin." There are also several fossil species of bowfin (species in the genera Amia and Cyclurus) dating back as far as the late Cretaceous (about 65 million years ago). The living species reaches a total length of approximately 35.4 in (90 cm).

Distribution

The bowfin is restricted to eastern North America, inhabiting fresh waters over most of the eastern half of the continental United States, southern Ontario, and Quebec, Canada.

Habitat

The bowfin is known only from fresh waters. As an adult it generally inhabits swampy, sluggish water of vegetated bays of warm lakes and rivers. Young individuals are rarely seen after the postlarval schools break up, suggesting that they move into deeper water or dense vegetation.

Behavior

Amia calva is a very hardy species. These fishes can withstand high temperatures and breathe air at the surface if necessary. They are even known to estivate. Specimens have been documented as being out of water for 24 hours without apparent harm.

Feeding ecology and diet

Bowfins are voracious predators. At the small postlarval stages (e.g., under 4 in/10 cm) total length) this species feeds on small animals such as insects, insect larvae, ostracods, and other zooplankton. Once the fishes start to get larger than about 4 in (10 cm), other fishes become its primary diet. Adults are also known to eat decapods. Observations of aquarium specimens indicate that the bowfin is a sluggish, clumsy, stalking predator that uses scent as much as sight in stalking food, which it captures by means of sudden intake of water. Other than humans, natural predators of adult Amia calva are unknown.

Reproductive biology

Bowfins spawn in spring. The males move into shallow waters of lakes and rivers, where they prepare a circular nest in areas of heavy vegetation or under logs. Once a female is attracted into the nest, spawning takes place, and four or five batches of eggs are laid. The eggs are adhesive and stick to the bottom of the nest. Females can lay up to 64,000 eggs. The young hatch in eight to 10 days and, like gars, have an adhesive organ on the tip of the snout by which they remain attached to vegetation (or other objects on the bottom) for seven to nine days. Then the young form a compact school which is guarded by the males for several weeks.

Conservation status

Bowfins are not on the IUCN Red List and are currently quite common in areas of the southern United States.

Significance to humans

As with gars, bowfins are often considered to be pest fishes. They have little value as food fishes, and are of little commercial or recreational use. Yet they are important predators in some regions, controlling undesirable species.

Resources

Books

Eddy, S., and J. C. Underhill. Northern Fishes, 3rd edition. Minneapolis: University of Minnesota Press, 1974.

Grande, L., and W. E. Bemis. "A Comprehensive Phylogenetic Study of Amiid Fishes (Amiidae) Based on Comparative Skeletal Anatomy: An Empirical Search for Interconnected Patterns of Natural History." Society of Vertebrate Paleontology Memoir 4; Supplement to Journal of Vertebrate Paleontology 18, no. 1 (1998).

Lee, D. S., C. R. Gilbert, C. H. Hocutt, R. E. Jenkins, D. E. McAllister, and J. R. Stauffer Jr. Atlas of North American Freshwater Fishes. Raleigh: North Carolina State Museum of Natural History, 1980.

Scott, W. B., and E. J. Crossman. Freshwater Fishes of Canada. Ottawa: Fisheries Resource Board of Canada, 1973.