The Southern Brook Lamprey Ichthyomyzon gagei Abstract The Southern Brook Lamprey Ichthyomyzon gagei is an elongated, eel-like fish that rarely exceeds six inches. Southern Brook Lamprey are non -parasitic filter feeders that prefer flowing water with a sandy substrate. They have two major life stages: ammocoete and adult with the majority of their life is spent as an ammocoete. Environmental factors can play a heavy role in determining the larval sex. South Brook Lamprey are believed to have evolved from the parasitic Chesnut Lamprey. The two species are morphologically similar but can be distinguished from each other, as the width of the buccal funnel never exceeds the width of the head in Southern Brook Lamprey. Context & Content The Southern Brook Lamprey Ichthyomyzon gagei belongs to the family Petromyzontidae, the sole extant family in Petromyzontiformes and one of only two jawless families of fishes. Petromyzontidae includes eight genera of lampreys: Caspiomyzon, Entosphenua, Eudontonmyzon, Ichthyomyzon, Lampetra, Lethenteron, Petromyzon, Tetrapleurodon. The Southern Brook Lamprey belongs to the Icthyomyzon genus which also includes five other species: Ichthyomyzon bdellium, Ichthyomyzon castaneus, Ichthyomyzon fossor, Ichthyomyzon greeleyi, and Ichthyomyzon unicuspis. (ITIS) General Characteristics Ammocoete, Black Creek System, August 1989 (Ross 2001) All lampreys have a line of seven circular gill openings and well welldeveloped eyes in their adult stage. The Southern Brook Lamprey can easily be distinguished from other lampreys, however, by the diameter of the buccal funnel, which never exceeds the head width, and the lack of well-developed teeth. In addition, the Southern Brook Lamprey have a shallow, continuous dorsal fin. The trunk myomeres number between 50 and 52, supraoral cusps number 3, and there are between 5 and 12 infraoral cusps. (Ross 2001) The Southern Brook Lamprey rarely exceeds 6 inches, and the females are typically slightly larger than the males (Moshin and Gallaway 1977; Beamish 1982). They are grey to brown dorsally becoming lighter tan or white on the sides. The
midsection is generally lighter than the head or tail. There are usually conspicuous spots or rims present near the lateral line that is actually the lamprey s organs (Ross 2001). The larval form of the Southern Brook Lamprey along with other Ichthyomyzon species have a poorly developed oral disk with no teeth and a horseshoe shaped mouth surrounded by a fleshy hood. They also have rudimentary eyes. The ammocoetes of the lamprey species are extremely difficult to identify as they only differ by subtle and variable differences in color (Ross 2001). Distribution IUNC Ichthyomyzon gagei distribution 2013 As shown in the IUNC distribution map above, the Southern Brook Lamprey is well represented in the Mississippi River Basin, particularly in coastal rivers and in the drainages of the Gulf of Mexico. The species can be found in Texas, Louisiana, Alabama, Mississippi, Florida, Georgia, and less readily in Oklahoma, Missouri, and Arkansas (Rhode and Lanteigne-Courchene 1980; Bemish et al. 1994). The abundance of the species declines significantly as you move north into Missouri; however, Cochran (1987) reported an isolated population in the upper Mississippi River in Minnesota and Wisconsin. Form & Function All lampreys have an eel-like, elongated, flexible, and cylindrical body. They also have somewhat of a continuous dorsal-caudal-anal fin similar to the eels, though they lack paired fins and a jaw. In addition, they use anguilliform swimming which is characteristic of eel-like fishes. They use whole body flexion to make lateral waves for propulsion (Moyle and Cech 2004). It also allows them to easily burrow into the beds of streams and rivers. Ontogeny & Reproduction
Southern Brook Lamprey spawning occurs in the spring at temperatures of 14-24 C. Males initiate the nest building process in a shallow, gravel bottomed riffle but are quickly joined by females (Moyle and Cech 2004). Groups of up to twenty adults help hollow out shallow nests where spawning will occur for two to four weeks (Dendy and Scott 1953). The females produce on average about 1,500 small eggs with a maximum size of 0.92mm (Beamish 1994). In acidic waters, the fecundity is negatively related to the number of males, but this trend in reversed when waters are more basic (Beamish 1993, Beamish 1983). Southern Brook Lamprey mature at 3-4 years of age and are semelparous, meaning they die shortly after spawning. The adults die within three weeks after spawning, around the same time the eggs begin hatching (Beamish 1993). The newly hatched ammocoetes are 11-14mm long and drift downstream following hatching, where they embed in fine sediment with their oral hood just above the surface and filter feed on phytoplankton and organic detritus (Moshin and Gallaway 1977, Moyle and Cech 2004). They remain in the ammocoete, meaning sand-bed, phase for the majority of their life. At three to four years of age in the early fall, large ammocoetes undergo rapid metamorphosis to the adult stage. Southern Brook Lamprey do not feed during their adult stage so it is relatively short. (Ross 2001). Ammocoetes do not have a predetermined sex; instead, they all rapidly produce eggs until about 17 months of age. Sex is determined by environmental factors including stream temperature, population density, average growth rate, and ph. Males then re-absorb the eggs, though it is not uncommon for male ammocoetes to still have eggs in their testes. In general, the proportion of males declines as density of larvae rises and growth rates decrease (Beamish 1993, Ross 2001). Ecology The Southern Brook Lamprey are one of three non-parasitic lamprey species termed the Brook Lampreys. The species spends the majority of its life buried in the coarse-sand substratum of small, swift rivers ammocoetes, the larval form, can be found in slower moving streams. The ammocoetes filter feed off of algae and bacteria floating in the water column or growing on vegetation. The adults, however, do not eat anything and must survive off of the energy they stored while in their larvae stage. (Ross 2001) Behavior The Southern Brook Lamprey spends the majority of its life filter feeding in lotic waters. They remain hidden in the sandy-substrate bottoms of streams, which protect them from predation. Once they mature and are ready to spawn, groups of up to twenty adults congregate and spawn in their shallow, hollowed out nests (Ross 2001). Genetics Parasitic and non-parasitic lamprey species coexist in nearly every region. The paired species are often morphologically similar and only differ in their life stages where one is parasitic and the other is non-parasitic (Salewski 2003). There is no evidence of interbreeding. Lamprey species pairs are a rare example of
worldwide sympatric evolution. It is widely accepted that the non-parasitic species in the pair evolved from the parasitic species. Vladykov and Kott (1979) coined the term satellite species to describe the evolutionary history of non-parasitic species, as there is no evidence that one non-parasitic species evolved into another nonparasitic species. Instead it is believed that one parent parasitic species gave rise to one or more daughter non-parasitic species. It is widely acknowledged the Southern Brook Lamprey is the daughter species of the Chesnut Lamprey in North America (Salewski 2003). Conservation The IUNC lists the Southern Brook Lamprey as least concern. Ross (2001) states the population is secure and stable. There is no evidence of a reduction in the size of their range; however, due to the lampreys burrowing behavioral they are sensitive to sedimentation and habitat alteration (Ross 2001). Literature Cited Beamish, F. W. H., and E. J. Thomas. 1983. Potential and Actual Fecundity of the "Paired" Lampreys, Ichthyomyzon gagei and I. castaneus. Copeia 1983(2):367 374. Beamish, F. W. H. 1993. Environmental Sex Determination in Southern Brook Lamprey, Ichthyomyzon gagei. Can. J. Fish. Aquat. Sci. Canadian Journal of Fisheries and Aquatic Sciences 50(6):1299 1307. Beamish, F. W. H., P. K. Ott, and S. L. Roe. 1994. Interpopulational Variation in Fecundity and Egg Size in Southern Brook Lamprey, Ichthyomyzon gagei. Copeia 1994(3):718-725. Cochran, P. A. 1987. The Southern Brook Lamprey (Ichthyomyzon gagei) in the St. Croix River Drainage of Wisconsin and Minnesota. Copeia 1987(2):443 446. Dendy, J. S., and D. C. Scott. 1953. Distribution, Life History, and Morphological Variations of the Southern Brook Lamprey, Ichthyomyzon gagei. Copeia 1953(3):152 162. Ichthyomyzon gagei Hubbs and Trautman, 1937. (n.d.). ITIS. Integrated Taxonomic Information System. Mallat, J., Sullivan, J., and Winchell, C. J., 2001. The relationship of lampreys to hagfishes: A spectral analysis of ribosomal DNA sequences. Pages 106-118 In P.K. Ahlberg, ed. Major events in early vertebrate evolution. London: Taylor and Francis. Moshin, A. K. M., and B. J. Gallaway. 1977. Seasonal Abundance, Distribution, Food Habitats and Condition of the Southern Brook Lamprey, Ichthyomyzon gagei
Hubbs & Trautman, in an East Texas Watershed. The Southwestern Naturalist 22(1):107 114. Moyle, P. B. 2011. Fishes: an Introduction to Ichthyology. Prentice-Hall of India Pvt. Ltd. NatureServe. 2013. Ichthyomyzon gagei. The IUCN Red List of Threatened Species 2013: e.t202619a18232784. Rohde, F. C., and J. Lanteigne-Courchene. 1980. Ichthyomyzon gagei Hubbs and Trautman, southern brook lamprey, p.18. In: Lee et al. 1980 Ross, S. T., and W. M. Brenneman. 2001. The inland fishes of Mississippi. University Press of Mississippi. Jackson. Salewski, V. 2003. Satellite species in lampreys: a worldwide trend for ecological speciation in sympatry? Journal of Fish Biology 63(2):267 279. Vladykov, V. D., and E. Kott. 1979. Satellite species among the holarctic lampreys (Petromyzonidae). Can. J. Zool. Canadian Journal of Zoology 57(4):860 867. William, F., and H. Beamish. 1982. Biology of the southern brook lamprey, Ichthyomyzon gagei. Environ Biol Fish Environmental Biology of Fishes 7(4):305 320. Order All lampreys belong to the order Petromyzontiformes, which is the most primitive order in the subphylum vertebrata. Petromyzontiformes includes nearly 40 species. Mallat et al. (2001) determined through ribosomal DNA sequencing that the lampreys are more closely related to the hagfishes than other vertebrates, which was previously thought to be sister group of lampreys. However, the study was not entirely conclusive so the exact sister groups are still undetermined (Moyle and Cech 2004) Family Petromyzontidae is the single extant family in Petromyzontiformes and includes eight lamprey genera. The lampreys are typically easily identified, as they are cylindrical, elongated, eel-like fish that lack a jaw and paired fins. The lampreys have seven oval gill openings and only two semicircular canals in the ear (Ross 2001).