Life History Information
Lampreys are divided into different categories based on their species-specific life cycles; species are either parasitic or nonparasitic (but see Beamish 1987 for sympatric parasitic and non-parasitic Lampetra richardsoni). Parasitic species include both anadromous species and those restricted to streams and rivers. The nonparasitic life-cycle is similar to the parasitic life cycle except that adults do not feed. These species are diagnosable, endemic to freshwaters and hypothesized to have evolved from extant parasitic ancestors (See Fig. 1).
A generalized lamprey life cycle is illustrated in Figure 2. All lamprey species have a protracted, sedentary larval phase (ammocete, Fig. 3) that filter feeds in freshwater (Potter, 1980a). This phase may last 3-7 years, after which they metamorphose into an adult with gonads, definitive eyes, tooth-bearing suctorial disc and enlarged dorsal fins (Hardisty & Potter 1971, Potter et al. 1982). Young adults of parasitic species move to large rivers, lakes or the sea where they feed on teleosts (Hardisty & Potter 1971). Parasitic individuals attach to hosts by means of the suctorial disc and destroy host tissue through the action of a multicuspid tongue-like piston and the secretion of cytolytic enzymes from buccal glands (Cook et al. 1990, Potter et al. 1995). The adult lamprey then extracts either blood and/or muscle from its host (Potter & Hilliard 1987) (Fig. 4).When fully grown, the adult ceases feeding and migrates upstream where nesting and spawning ensue, then death. Non-parasitic adults do not feed; after a short adult stage relative to parasitic species, they ascend streams, construct nests (Fig. 5), spawn and die. Given the morphological similarities between some parasitic and non-parasitic species it has been proposed that the non-parasitic species are directly derived from extant parasitic species, and that this has occurred multiple times (See Fig. 1 for paired or satellite species hypothesis; Hubbs & Trautman 1937, Zanandrea 1959, 1961, Hardisty & Potter 1971, Hubbs & Potter 1971).
Fish illustrations by
Joseph R. Tomelleri
and used with permission.
|Figure 1. Hypothesized "paired or satellite species" concept in lamprey evolution remaining to be tested within a phylogenetic context.|
|Figure 3. Ammocete - lateral view and filter feeding.|
|Figure 2. Generalized lifecycles of parasitic and nonparasitic lampreys. Note that the nonparasitic life cycle is an abbreviated cycle of the parasitic cycle as the adults mature and spawn and then die without feeding. Ammocetes is a filter-feeding "larval" stage found burried in sand and debris of streams and creeks for multiple years prior to transformation..|
|Figure 4. Oral disk of parasitic lamprey and photo of lampreys parasitizing fish.|
|Figure 5. Lampreys constructing nest.|
Tanks holding about 50,000 larvae producing migratory pheromone .
holding water is pumped into the tanks and then through the resin
The columns are eluted and evaporated down to a concentrate
Dentition of Lampreys
As one would surmise, the dentition of the oral disk varies between species and is often useful in the identification of species. The type of dentition possessed by a species is highly correlated with their phylogenetic relationships and their general diet. Some species are flesh eaters, some are fluid and flesh eaters, and some feed on fluids.
Describe the main types of teeth and illustrate.