''Ammocrypta'' is a genus of freshwater

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 ...

, commonly known as the sand darters, which is classified in the

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

Etheostomatinae Etheostomatinae is a species-rich subfamily of freshwater ray-finned fish, the members of which are commonly known as the darters. The subfamily is part of the family Percidae which also includes the perches, ruffes and pikeperches. The family ...

, part of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Percidae The Percidae are a family of ray-finned fish, part of the order Perciformes, which are found in fresh and brackish waters of the Northern Hemisphere. The majority are Nearctic, but there are also Palearctic species. The family contains nearly 250 ...

which also includes the

perch Perch is a common name for freshwater fish from the genus ''Perca'', which belongs to the family Percidae of the large order Perciformes. The name comes from , meaning the type species of this genus, the European perch (''P. fluviatilis'') ...

es, ruffes and pikeperches. The species in the genus occur in eastern North America in

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

and the

continental United States The contiguous United States, also known as the U.S. mainland, officially referred to as the conterminous United States, consists of the 48 adjoining U.S. states and the District of Columbia of the United States in central North America. The te ...

Characteristics

''Ammocrypta'' species are characterised by having rather elongate and slender bodies. Their bodies are translucent and there is only a single spine in the

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

. They also have Spreitzer

vertebrae Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

, that is that the first three vertebrae of the backbone, counting from the head, have an open

haemal arch A haemal arch, also known as a chevron, is a bony arch on the ventral side of a tail vertebra of a vertebrate. The canal formed by the space between the arch and the vertebral body is the haemal canal. A spinous ventral process emerging from the ha ...

which allows for the fish's

kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

to expand. They have the habit of burying into the sand or gravel bed of streams, only their eyes being visible. The translucence of their bodies and their habit of burying themselves gives them some protection against predation. The shared morphological characteristics of ''Ammocrypta'' with its sister taxon ''Crystallaria'' include the possession of complete

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelia ...

s and unbroken canal on the head. They also share high meristic counts which are thought to be indications of basal morphology, referred to as plesiomorphies.

Distribution

''Ammocrypta'' is found in eastern North America where thy are found across the central part of the coastal plain of the

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

, the whole of the drainage basin of the

Mississippi River The Mississippi River is the main stem, primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri River, Missouri. From its traditional source of Lake Ita ...

and of the

Ohio River The Ohio River () is a river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing in a southwesterly direction from Pittsburgh, Pennsylvania, to its river mouth, mouth on the Mississippi Riv ...

, the Lake St Clair system as well as the lower drainage basins of

Lake Huron Lake Huron ( ) is one of the five Great Lakes of North America. It is shared on the north and east by the Canadian province of Ontario and on the south and west by the U.S. state of Michigan. The name of the lake is derived from early French ex ...

and

Lake Superior Lake Superior is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. Lake Michigan–Huron has a larger combined surface area than Superior, but is normally considered tw ...

Species

The currently recognized species in this genus are: * '' Ammocrypta beanii'' D. S. Jordan, 1877 (Naked sand darter) * '' Ammocrypta bifascia'' J. D. Williams, 1975 (Florida sand darter) * '' Ammocrypta clara'' D. S. Jordan & Meek, 1885 (Western sand darter) * '' Ammocrypta meridiana'' J. D. Williams, 1975 (Southern sand darter) * '' Ammocrypta pellucida'' Putnam, 1863 (Eastern sand darter) * '' Ammocrypta vivax'' O. P. Hay, 1882 (Scaly sand darter)

Taxonomy

''Ammocrypta'' is the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

of the genus '' Crystallaria'' and together these genera are the sister taxon of the

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

consisting of the speciose genus ''

Etheostoma ''Etheostoma'' is a genus of small freshwater fish in the family (biology), family Percidae, and within the sub-family ''Etheostomatinae'', native to North America. Most are restricted to the United States, but species are also found in Canada and ...

'' and ''

Nothonotus ''Nothonotus'' is a genus or subgenus of freshwater ray-finned fish, a darter from the subfamily Etheostomatinae, part of the family Percidae, which also contains the perches, ruffes and pikeperches. It is endemic to the southeastern United Sta ...

''. Some authorities regard ''Crystallaria'' as a

subgenus In biology, a subgenus ( subgenera) is a taxonomic rank directly below genus. In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the ge ...

of ''Ammocrypta''.

References

{{Authority control Etheostomatinae Taxa named by David Starr Jordan