| The focus of this thesis is on the adult sea lampreys, Petromyzon marinus anadromous spawning migration. It has not been established if the journey is with a high fidelity to its stream of birth. To determine if this is the case or if selecting streams to spawn in is a random process, use was made of a mitochondrial gene to compare between two different larval stream populations. The role of larval bile acid secretion was also examined as they serve as an attractant to the adults.; Ammocoetes, the larval form of the sea lamprey appear as wormlike organisms, which live, in soft sandy beds along freshwater rivers and streams. The ammocoetes stays in the larval stage for a period of three to seven years (Mallat, 1983). Since the ammocoetes are filter feeders they need to be near flowing streams or rivers. The diets for these organisms consist of diatoms, desmids, protozoa, and any other microscopic organic matter (Yamazaki, Y. et al., 2003). These filter feeders can weigh up to five grams and be as long as twenty centimeters prior to metamorphosis (Sorenson, P. et al., 1993). The ammocoetes produce the bile acids petromyzonol sulfate (PZS), and allocholic acid (ACA), which are released into the water (Sorenson, P. et al., 1993).; The adult males are attracted to particular freshwater streams by the strong attraction to the ammocoetes bile acid odor (PZS and ACA). These bile acids have been shown to attract the adult male sea lampreys to the spawning sites (Li, W. et al., 1995). Many behavioral laboratory studies show that adult sea lampreys swim more towards water that is treated with PZS and ACA, allowing for researchers to infer that the same event occurs naturally (Polkinghorne, C. et al., 2001). The males release the oxidized form of PZS and ACA, which are 3-keto petromyzonol sulfate (3KPZS) and 3-keto allocholic acids (3KACA). These oxidized forms of the bile acid are responsible for attraction of adult female sea lamprey to fresh water streams (Li, W. et al., 2003B). It is advantageous to the males to use the ammocoetes bile acids as a cue, as this indicates that the particular stream is a suitable habitat (Sorenson, P. et al., 2000). The adult male sea lamprey arrive at the spawning site first and begin vigorously building their nests, soon after the females take over the nest building in the spawning season (Sorenson, P. et al., 2000). In generally eighteen months prior to spawning, the adult sea lampreys stop feeding and start producing bile acids; they begin to sexually mature (Sorenson, P. et al., 2000). At this stage, the adult sea lampreys begin to lose weight, while the length remains the same (Sorenson, P. et al., 2000). After spawning, the adult sea lampreys die, and their eggs hatch to yield the larval ammocoetes. After three to seven years, the larval ammocoetes metamorphosize into adults, migrate out to sea, and live as parasites. About a year later, the adult lampreys return to a fresh water stream to spawn and die, completing their life cycle (Sorenson, P. et al., 2000).; Bile acids are proposed as the migratory pheromone because it is stable chemically, and produced in great quantity (Sorenson, P. et al., 2000). However, researchers have shown that PZS and ACA are not only used as a chemical cue by sea lampreys alone, but also used by the western brook lamprey and the pacific lamprey (Li, W. et al., 2003 A). This suggests that the bile acids are not specific to one species of lamprey. In order to determine if the bile acids, PZS and ACA are present in the stream, high performance liquid chromatography (HPLC) was used to determine the concentration of the bile acids (Li, W. et al., 2003 A).; The purpose of this study is to find out if Petromyzon marinus chooses their spawning site randomly or specifically. If there is no specificity, it can be hypothesized that the bile acid is responsible for attracting the adult sea lamprey to any site that the ammocoetes' bile acids secretion occurs. However, if there i... |
