Jared M. Fine

Evidence that petromyzontid lampreys employ a common migratory pheromone that is partially comprised of bile acids.

This study examined whether the larval pheromone employed by adult sea lamprey (Petromyzon marinus) to locate spawning streams and known to be at least partially comprised of bile acids is also employed by other lamprey species. Both production and release of lamprey-specific bile acids, and sensitivity to them were examined in a wide variety of species. High pressure liquid chromatography and electrospray ionization/mass spectrometry (ESI-MS) found gallbladders from 10 species of European and North American lamprey to contain large quantities of petromyzonol sulfate (PS) together with much smaller quantities of allocholic acid (ACA) and petromyzonol (P). Evaluation of holding waters from three of these species using ESI-MS found all to contain large quantities of PS and lesser quantities of ACA in similar ratios. Electro-olfactogram recording from the olfactory systems of three parasitic lamprey species found all to detect PS and ACA with high sensitivity. Behavioral studies using migratory adult sea lamprey found them to be attracted to the odors of heterospecific larvae as well as conspecific larvae, both of which contained similar amounts of PS and ACA. Finally, adult silver lampreys (Ichthyomyzon unicuspis) were also found to be attracted to the odor of larval sea lamprey. Together, these results demonstrate that PS and ACA are commonly produced and released by larval petromyzontid lampreys and likely used as part of a common evolutionarily conserved pheromone. This scenario is reasonable because lampreys share similar larval and spawning habitat requirements, and their larvae derive no apparent benefit from producing compounds that serve as an attractant for adults.

Conspecific cueing in the sea lamprey: do reproductive migrations consistently follow the most intense larval odour?

Conspecific cueing occurs when an organism receives information about habitat quality from the distribution of conspecifics. Consequently, animals should prefer to settle in habitats with high occupancy when conspecific cueing is used. Unlike salmonid fishes, which often acquire chemical recognition of natal streams in early life, sea lamprey, Petromyzon marinus , larvae produce a remarkably potent pheromone that migrating adults use to locate spawning streams. The size of the spawning migration in tributaries to the Great Lakes is correlated with the number of larvae resident to the stream, and therefore the amount of pheromone discharging into the lake. By releasing controlled amounts of larval odour into a lamprey-less stream, we tested the hypotheses that migrating sea lampreys (1) avoid swimming in waters that lack larval odour and (2) actively choose to swim in waters activated with the highest concentration of larval odour. Migrating sea lamprey clearly showed fine-scale movements (

A Sterol-Like Odorant in the Urine of Mozambique Tilapia Males Likely Signals Social Dominance to Females

Many species of freshwater fish with relatively simple mating strategies release hormonally derived sex pheromones in urine. However, it is not known whether species with more complex reproductive strategies use specialized urinary chemical signals. We addressed this by using the Mozambique tilapia (Oreochromis mossambicus Peters 1852), a lek-breeding species in which males establish dominance hierarchies and visiting females mate preferentially with territorial/dominant males. We measured urination frequency of territorial males in social isolation and in the presence of females that were either ready to spawn or had finished spawning. In groups of fish, we monitored the volume of urine stored in subordinate and dominant males to determine if urine volume and olfactory potency (by recording electro-olfactograms, EOG, in females) are related to the male’s social rank. Dominant, territorial males stored more urine than subordinates and released it in short pulses, the frequency of which increased in the presence of females ready to spawn but not in the presence of post-spawn females. Urine from subordinate and dominant males was fractionated by liquid chromatography and fractions tested for olfactory potency by using the EOG, with the most potent fraction analyzed by mass spectrometry (MS). The olfactory system of females was sensitive to a urinary compound that was more abundant in the urine of dominant males than in that of subordinates. MS analysis suggested the compound is a sulfated aminosterol-like compound with a formula of C29H40N2O10S. Therefore, we suggest that dominant/territorial tilapia males dramatically increase urination frequency in the presence of females ready to spawn and that the urinary odorant acts as a pheromonal signal of dominance, thereby influencing female spawning.

Biologically Relevant Concentrations of Petromyzonol Sulfate, a Component of the Sea Lamprey Migratory Pheromone, Measured in Stream Water

Adult sea lampreys locate spawning streams in the Great Lakes by using a migratory pheromone that is released by stream-resident larval conspecifics. Behavioral, electrophysiological, and biochemical analyses of larval release water have suggested that this pheromone is composed of several components, one of which is petromyzonol sulfate (PS), a known lamprey-specific bile acid. Its precursor, allocholic acid (ACA), has also been implicated. In this study, we employed high-performance liquid chromatography and mass spectrometry to look for both bile acids in various stream waters, thereby testing whether they might have a role in natural pheromone function. Although PS was measured at picomolar concentrations in streams known to contain larval lampreys and attract migratory adults, ACA was not. Neither compound was measured in streams lacking larvae. This finding indicates that PS is a component of the natural pheromone, and it suggests that ACA has little relevance.

A multi-component migratory pheromone in the sea lamprey

Stream finding by the anadromous sea lamprey is mediated by a pheromone released by stream-resident larvae which functions as an instinctively recognized indicator of habitat suitability. This cue is comprised of multiple components including the bile acid, petromyzonol sulfate, and at least one other as yet unidentified compound with a molecular weight of 704 daltons. These compounds are detected at picomolar concentrations and are released in large quantities; laboratory experiments demonstrate that each stream-resident larva activates at least 400L of water an hour. The actions of this pheromone are synergized by other compounds found in natural stream waters. Field studies demonstrate that the migratory pheromone plays a key role determining adult lamprey distribution in the Great Lakes. The cue does not appear to be species-specific or specialized, but rather a composite of biologically-relevant compounds that migratory adults have evolved the ability to recognize.

A practical method for obtaining useful quantities of pheromones from sea lamprey and other fishes for identification and control

ABSTRACT Pheromonally-mediated trapping is currently being developed for use in sea lamprey control in the Laurentian Great Lakes. To identify and test lamprey pheromones a practical procedure was needed to isolate relatively large quantities of pheromone from lamprey holding water. The present study developed such a technique. It employs Amberlite XAD7HP, an adsorbent resin which we found can extract over 80% of the sea lamprey migratory pheromone from larval holding water at low cost and with relative ease. This technique allowed us to collect tens of milligrams of all three components of the sea lamprey migratory pheromone, eventually permitting both identification and successful field testing. This technique might also be used to collect pheromones released by other species of fish.