|American brook lamprey|
|American brook lamprey late stage transformer (ammocoete metamorphosing into the adult).|
The American brook lamprey (Lethenteron appendix), is non-parasitic lamprey. In adults their disc-like mouths contain poorly developed teeth, useless for attaching to a host.
The eggs of the American brook lamprey (ABL) are small ~1mm white and sticky. When they hatch the embryo's are small <5mm white and wormlike. Within a month they take on the larval appearance. Larval of all lamprey are called ammocoetes and when small ABL ammocoetes have a dark band running longitudinally along the body, with a dark head region. The rest of the body is clear. As they increase in size the body becomes increasing darker, reaching a dark brown by the time the ammocoetes reach maximum size. The dark band on the body begins to lighten during this is as well and is not distinct in more mature ammocoetes. There are likely numerous races of ABL which may have location specific coloration. In Ohio older ammocoetes have a dark yellow band which runs the entire dorsal surface, as well as pigmentation in the caudal fin. During metamorphoses into the adult this coloration change drastically. Adults in the fall and winter are silver, but can become more black or brownish by the spring when breeding begins. Adults have a dark back, pale belly, yellowish fins and a dark blotch at the end of the tail, and their skin is smooth and leathery and without scales. Adults are usually around 8 inches long, although sizes of adults is often variable. Brook lamprey are generally found in clear, cold brooks and small streams.
Spawning takes place in spring. The males (aided by females) construct small nests by picking up pebbles with their mouths and moving them to form the rims of shallow depressions. The sticky eggs are deposited in the nest and adhere to the sand and gravel. As with all lamprey adults die after spawning.
When they first hatch, young lamprey are called ammocoetes. Ammocoetes burrow into the sand and silt where they live for 3–7 years, feeding on microscopic plant and animal life and detritus. Shortly before spawning, ammocoetes metamorphose into sexually mature adult fish. Adult brook lamprey cannot eat, since they have a nonfunctional intestine, and only live for four to six months.