The sheepshead minnow (''Cyprinodon variegatus''), also known as sheepshead pupfish, is a species of

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

in the family

Cyprinodontidae Pupfish are a group of small killifish belonging to ten genus, genera of the family Cyprinodontidae of ray-finned fish. Pupfish are especially noted for being found in extreme and isolated situations. They are primarily found in North America, S ...

, the pupfishes. It is found in

salt marsh A salt marsh, saltmarsh or salting, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. I ...

and

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime enviro ...

environments and is native to the eastern coasts of North and Central America.

Description

The sheepshead minnow is a deep-bodied fish growing up to a length of up to through . It is nearly half as deep as it is long, excluding its tail. It is laterally compressed with flat sides, an arched back and a small head with a flattened top. The small mouth is at the end of the snout and the teeth are large and wedge-shaped with three cusps. The pectoral fins are large and extend past the origins of the small pelvic fins. The origin of the anal fin hardly overlaps the trailing edge of the dorsal fin. The caudal peduncle is thick and the caudal fin is truncated and square-ended. The arrangement of the fins, the deep body and the tri-cuspid teeth help to distinguish this fish from the mummichog (''Fundulus heteroclitus''), which is found in the same habitats. The body is covered by large, circular scales, the ones on the cheeks and the top of the head and a single scale just above the pectoral fin being the largest. The male is generally larger and more deep-bodied than the female, with larger dorsal, pelvic and anal fins. The color of the sheepshead minnow is olive green above and yellowish below. Juveniles have irregular transverse dark bars and the females keep these as they mature, while the males lose theirs. The dorsal fin is dark while the pectoral, pelvic and anal fins are orange. During the breeding season the male becomes very colorful with steel blue upper parts in front of the dorsal fin, lustrous green upper parts behind and deep salmon-pink underparts.

Distribution and habitat

The sheepshead minnow is native to the eastern coast of the United States. Its range extends from

Cape Cod Cape Cod is a peninsula extending into the Atlantic Ocean from the southeastern corner of Massachusetts, in the northeastern United States. Its historic, maritime character and ample beaches attract heavy tourism during the summer months. The ...

southwards to the Yucatan peninsula in Mexico, also the West Indies. It is found in brackish water in bays, inlets, lagoons,

saltmarsh A salt marsh, saltmarsh or salting, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It ...

es and similar locations with little wave action and sandy or muddy bottoms. It is tolerant of wide variations in

salinity Salinity () is the saltiness or amount of salt (chemistry), salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensio ...

and is also found in hypersaline conditions.

Behavior

The sheepshead minnow is an

omnivore An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize t ...

, eating both animal and vegetable matter. Its diet mainly consists of detritus, microalgae, crustacean larvae and other small invertebrates. Males are aggressive and will attack fish larger than itself, slashing its prey with its sharp teeth and devouring it when it is subdued. Breeding takes place in shallow water between April and September, the males competing fiercely for the females. A few eggs are spawned at a time, and these are fertilised by the males which grasp the females with their fins. The eggs clump together and sink to the seabed, connected by sticky threads. They hatch after five or six days. During the winter, this fish burrows into the soft

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...

and remains dormant.

Uses

The sheepshead minnow is commonly kept as an aquarium fish. It is easy to breed in captivity and is used as a

forage fish Forage fish, also called prey fish or bait fish, are small pelagic fish that feed on planktons (i.e. planktivores) and other small aquatic organisms (e.g. krill). They are in turn preyed upon by various predators including larger fish, seabirds ...

mariculture Mariculture, sometimes called marine farming or marine aquaculture, is a branch of aquaculture involving the cultivation of marine organisms for food and other animal products, in seawater. Subsets of it include ( offshore mariculture), fish fa ...

Status

The sheepshead minnow has a wide range and a large total population, divided up into a number of subpopulations. The total number of individuals seems stable and no particular threats to the fish have been identified, so the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

has listed it as being of "

Least concern A least-concern species is a species that has been evaluated and categorized by the International Union for Conservation of Nature (IUCN) as not being a focus of wildlife conservation because the specific species is still plentiful in the wil ...

". The sheepshead minnow is a eurytolerant fish able to withstand extreme temperatures and live in a wide range of environments. This species acclimates to different temperatures partly by altering the activity of enzymatic antioxidants in the body such as

catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting ...

superoxide dismutase Superoxide dismutase (SOD, ) is an enzyme that alternately catalyzes the dismutation (or partitioning) of the superoxide () anion radical into normal molecular oxygen (O2) and hydrogen peroxide (). Superoxide is produced as a by-product of oxy ...

, and

glutathione peroxidase Glutathione peroxidase (GPx) () is the general name of an enzyme family with peroxidase activity whose main biological role is to protect the organism from oxidative damage. The biochemical function of glutathione peroxidase is to reduce lipid ...

. All of these enzyme antioxidants were altered within the fish’s white muscle at extreme hot or cold temperatures in the lab, which may be one reason the fish showed no increase in

lipid peroxidation Lipid peroxidation, or lipid oxidation, is a complex chemical process that leads to oxidative degradation of lipids, resulting in the formation of peroxide and hydroperoxide derivatives.{{Cite journal , last1=Ayala , first1=Antonio , last2=Muñoz ...

damage. Although sheepshead minnows appear able to deal with

oxidative stress Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system's ability to readily detoxify the reactive intermediates or to repair the resulting damage. Disturbances in the normal ...

caused by temperature extremes, they may be less adapted to cope with

microplastics Microplastics are "synthetic solid particles or polymeric matrices, with regular or irregular shape and with size ranging from 1 μm to 5 mm, of either primary or secondary manufacturing origin, which are insoluble in water." Microplastics a ...

in their environment. Researchers found that when microplastics were ingested by the sheepshead minnow they decreased the fish’s swimming behavior and caused changes in the expression of genes related to oxidative stress, immune responses, and

apoptosis Apoptosis (from ) is a form of programmed cell death that occurs in multicellular organisms and in some eukaryotic, single-celled microorganisms such as yeast. Biochemistry, Biochemical events lead to characteristic cell changes (Morphology (biol ...

References

{{Authority control

sheepshead minnow The sheepshead minnow (''Cyprinodon variegatus''), also known as sheepshead pupfish, is a species of ray-finned fish in the family Cyprinodontidae, the pupfishes. It is found in salt marsh and estuary environments and is native to the eastern co ...

Fish of the Caribbean Fish of the Gulf of Mexico Fish of the Eastern United States Fauna of the Southeastern United States Endangered fish Endangered biota of Mexico Endangered fauna of the United States Endangered fauna of North America Taxa named by Bernard Germain de Lacépède

Fish of Aruba