Lampreys

Lampreys are primitive jawless fishes in the Family Petromyzontidae, Order Petromyzontiformes, Class Petromyzontida, and Superclass Cyclostomata. The common name “lamprey” is almost certainly derived from the Latin lampetra, which likely means “stone licker” (lambere “to lick” + petra “stone”). They are also sometimes called lamprey eels, although they are not eels. Instead, lampreys are the direct descendants of the first armored jawless fishes or ostracoderms, which first appeared over 400 million years ago during the Silurian and Devonian periods. Today, there are only two remaining groups of jawless fishes: the lampreys and the hagfishes (Order Myxiniformes, Class Myxini). Hagfishes, which resemble lampreys, are the sister taxon of lampreys based on DNA evidence. There are about forty-two living lamprey species in ten genera among three families: Geotriidae (single species), Mordaciidae (two species), and Petromyzontidae (thirty-nine species). Lampreys exhibit an antitropical distribution, with two families endemic to the Southern Hemisphere and the third restricted to the Northern Hemisphere. They are found in most temperate regions except those in Africa. There are five lamprey species in Arkansas: the chestnut lamprey, southern brook lamprey, silver lamprey, American brook lamprey, and least brook lamprey.

In North America, members of the Family Petromyzontidae are characterized by having an eel-like body, a skeleton of cartilage instead of bone, no paired fins, a single median nostril opening, seven pairs of external gill openings, and a pair of eyes developed in adults. Instead of jaws, this group has an oral disc with teeth, as well as teeth occurring on the tongue. Lampreys are sexually dimorphic, meaning that males differ from females morphologically. Males are generally smaller than females and have a long urogenital papilla versus no papilla in females. Other members of the Family Petromyzontidae include the genera Caspiomyzon, Entosphenus, Eudontomyzon, and Tetrapleurodon.

In Arkansas, lampreys are often called lamprey eels. However, lampreys are not eels at all and can be easily distinguished from true eels (Order Anguilliformes, Family Anguillidae). True eels have jaws, whereas lampreys lack them. In addition, eels have a bony skeleton, two nostrils, a scaled body, paired fins, and gills covered by an operculum.

Lampreys have been reported to be used as food for humans. They were apparently sought after by ancient Romans, and during the Middle Ages they were commonly eaten by the upper classes throughout Europe, especially during Lent.

Lampreys have two distinct life stages: a larval form and an adult form. Larval lampreys are known as ammocoetes. Typically, in the late winter and early spring, adult lampreys migrate upstream to small headwater streams where they construct shallow nests that resemble pits. In these pits, adults gather to spawn and lay eggs. After spawning, adults die, and the eggs hatch into ammocoetes. Ammocoetes generally resemble adults, but they do not have well-developed eyes, a sucking disc, or rasping teeth. Instead, a large hood covers the mouth region. Typically, the ammocoete spends the next one to six years, depending on the species, living in soft sediments at the edge of pool areas of the stream, where they feed on detrital material. After one to six years and, in the fall of the year, the ammocoete will transform into an adult lamprey.

Most lampreys inhabit freshwater environments, some in land-locked lakes; however, the most famous lamprey, Petromyzon marinus, the sea lamprey, lives in the ocean for most of its adult life but returns to fresh water to spawn. Sea lampreys have become a major pest in the Great Lakes and are considered an invasive species, as they have no natural enemies in the lakes and prey on many species of commercial value.

In Arkansas, there are five lamprey species, which are strictly freshwater. These five lampreys are the chestnut lamprey (Ichthyomyzon castaneus), southern brook lamprey (I. gagei), silver lamprey (I. unicuspis), American brook lamprey (Lethenteron appendix), and the least brook lamprey (Lampetra aepyptera). Two species are parasitic (I. castaneus and I. unicuspis), while three are non-parasitic (I. gagei, Le. appendix, and L. aepyptera). Parasitic lampreys have a rasping tongue and a large buccal funnel with many teeth. Nonparasitic lampreys have a vestigial digestive tract because they do not feed as adults and possess a less well-developed oral disc and teeth. Conversely, parasitic lampreys have a well-developed digestive tract and do feed in both stages.

Chestnut Lampreys
The chestnut lamprey (I. castaneus) was described by Charles Frédéric Girard (1822–1895) in 1858 and is a brownish lamprey with poorly developed eyes and a low, continuous dorsal fin that is not separated into two parts. Adult chestnut lampreys have been found to parasitize carp, suckers, catfishes, sunfishes, and various basses. When attached, the lamprey rasps a hole in the host while an anticoagulant (lamphedrin) secreted by buccal glands in their saliva is injected into the wound to keep the blood flowing. This lamprey has an oral disc wider than the head and well-developed bicuspid teeth in radiating rows. Trunk myomeres number 49 to 58 (usually 51 to 54). This is one of the larger lampreys in Arkansas, as adults reach 25 to 36 cm (10 to 14 in.) in length, and is the most common species found on the state’s fishes. Ammocoetes are much smaller and may reach a length of 15 cm (six in.). Chestnut lampreys live in large streams, rivers, and reservoirs in the Arkansas, White, St. Francis, Ouachita, and Red rivers.

Sometime in late winter and spring, adult lampreys migrate to smaller gravel-bottomed streams to spawn. They usually dig a depression in the gravel and congregate in the depression to spawn. Numerous individuals may spawn together over the nests. Fecundity in females has been estimated to range from 10,000 to 20,000 ova per female. Adults die soon after spawning. Larvae hatch in about two weeks and then drift downstream until they find silt-bottomed pool areas or marginal areas where they live until transforming into adults. In Oklahoma, the juvenile stage of this species was found to be less than a year to 1.5 years old, whereas adults may live another two to three years.

Southern Brook Lampreys
The southern brook lamprey (I. gagei) was described in 1937 by Carl L. Hubbs (1894–1979) and Milton B. Trautman. It ranges from the Gulf Slope drainages from Galveston Bay, Texas, to Florida and the Mississippi River basin of southern Missouri, eastern Oklahoma, Arkansas, Mississippi, and Louisiana to the Tennessee River drainage, western Kentucky, and northern Alabama; disjunct populations occur in the upper Mississippi River (St. Croix River system) of Wisconsin and Minnesota. Within the state, this lamprey occurs widely in the Arkansas River, Petit Jean River, White River, Ouachita River, and Little River systems. This lamprey is believed to be a dwarf, non-parasitic derivative of the parasitic species, I. castaneus. Little variation has been found in Arkansas populations of I. gagei. Adults have been found in clear, small-to-medium-sized streams over gravel and rock bottoms. Adult I. gagei migrate to tributary streams in March and May where they construct nests in sand and gravel and die within two to twenty-six days after spawning 800 to 2,500 eggs. Ammocoetes live from three to four years. Adults may reach 13 to 18 cm (5 to 7 in.) in total length.

Silver Lampreys
The parasitic silver lamprey (I. unicuspis) was described in 1937 by Hubbs and Trautman. It ranges from the St. Lawrence–Great Lakes basin from Quebec to southwestern Ontario, south through the upper Mississippi and Ohio river basins to central Tennessee, Hudson Bay basin, Manitoba, and Missouri River (Nebraska), and Mississippi River in northeastern Arkansas. This lamprey is the most recently discovered lamprey species in Arkansas and has been captured only from paddlefish (Polydon spatula) hosts in the White and Buffalo rivers. Adult silver lampreys can measure 36 to 38 cm (14 to 15 in.), whereas ammocoetes are only half that size. This parasitic lamprey also has a shallow notched dorsal fin that is not divided into two distinct parts and is connected to a round caudal fin. The mouth disc is wider than the head. Disc teeth are well developed and unicuspid. Lateral myomeres generally number 49 to 52. Silver lampreys have been known to feed on a number of other fish species including paddlefish, common carp, catfishes, and suckers. On average, about 11,000 eggs are produced by each female in spring, and the ammocoetes stage lasts from four to seven years, with adults living up to a year. This lamprey is considered a Species of Special Concern in Arkansas.

American Brook Lampreys
The American brook lamprey (Le. appendix) was described by James E. DeKay (1792–1851) in 1842 and is a nonparasitic lamprey once thought to be confined to the White River system of northern portion of the state until a disjunct population was found in L’Eau Frais Creek (Ouachita River system) in Clark and Hot Spring counties. This lamprey tends to inhabit cool, clear, small-to-medium-sized streams, where it lives in gravelly raceways and riffles. The oral disc is wider than the head when expanded and contains well-developed teeth in radiating rows. The circumoral teeth are bicuspid and number four on each side of the mouth. Lateral myomeres for this lamprey typically range from 63 to 73 (usually 66 to 70). This lamprey can be confused with L. aepyptera, but higher myomere counts in Le. appendix will serve to separate them. The ammocoetes of Le. appendix feed on algae and detritus for three to seven years before they metamorphose into sexually mature adult fish. They spawn in the spring (March–April) by constructing a nest by removing pebbles from the gravel, with each female depositing an average of 2,800 eggs. This lamprey may reach sizes of 25 to 50 cm (10 to 20 in.). This lamprey appears to be sensitive to pollution and turbidity.

Least Brook Lampreys
The least brook lamprey (L. aepyptera) was described by Charles C. Abbott (1843–1919) in 1860 and ranges from the North American Atlantic Slope from southeastern Pennsylvania to Virginia and North Carolina and the Mississippi River basin from western Pennsylvania to south-central Missouri and northern Arkansas south to southern Mississippi and east to Georgia. This lamprey is uncommon in Arkansas, as only about forty specimens have been collected to date, all of which were taken in northern Arkansas in the White and Black river systems. Specimens have been previously reported from Fulton, Izard, Lawrence, Marion, Randolph, Sharp, and Stone counties; however, populations from four of these counties (Fulton, Izard, Marion, and Stone) are considered possibly extirpated.

The least brook lamprey is the smallest lamprey in the state, with adults usually measuring 8.9 to 12.7 cm (3.5 to 5.0 in.) in length. This brownish, nonparasitic lamprey has conspicuous eyes and a deeply notched dorsal fin that is divided into two separate parts. The oral disc is distinctly narrower than the head when expanded. In general, teeth in the oral disc are poorly developed except for a pair of prominent, widely separated supraoral teeth. Lateral myomeres number 50 to 61 (usually 54 to 56). The least brook lamprey is herbivorous in its immature stages and feeds on minute drifting microscopic organic material; the adult does not feed. This lamprey typically lives in riffles and raceways in small clear streams. Both sexes take part in nest building, and spawning is usually in the spring. Interestingly, in some populations where spawning occurs at a small size, females produce comparatively fewer but larger eggs. Because of the small number of specimens known for the state, the least brook lamprey is considered imperiled (S2) by NatureServe.

Concerning lamprey parasites, only one of the five lampreys in the state (Le. appendix) has been reported to harbor a single larval tapeworm and two species of nematodes. It is thought that these lampreys obtained infections while they were filter-feeding ammocoetes.

For additional information:
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Henry W. Robison
Sherwood, Arkansas

Chris T. McAllister
Eastern Oklahoma State College