Nitrogenous compounds characterized in the deterrent skin extract of migratory adult sea lamprey from the Great Lakes region.

The sea lamprey (Petromzons marinus) is a devastating invasive species that represents a significant impediment to restoration of the Laurentian Great Lakes. There is substantial interest in developing environmentally benign control strategies for sea lamprey, and many other aquatic invasive species, that employ the manipulation of semiochemical information (pheromones and chemical cues) to guide the movements of invaders into control opportunities (e.g. traps, locations for safe pesticide application, etc.). A necessary precursor to the use of semiochemicals in conservation activities is the identification of the chemical constituents that compose the odors. Here, we characterize the major nitrogenous substances from the water-soluble fraction of a skin extract that contains the sea lamprey alarm cue, a powerful repellent that has proven effective in guiding the movements of migrating sea lamprey in rivers. Nitrogenous compounds are suspected components of fish alarm cues as the olfactory sensory neurons that mediate alarm responses transduce amino acids and related compounds. A laboratory assay confirmed the behavioral activity contained in the alarm cue resides in the water-soluble fraction of the skin extract. This water-soluble fraction consisted primarily of creatine (70%), heterocyclic nitrogenous compounds (4.3%) and free amino acids (18.4%), respectively. Among the free amino acids characterized in our study, essential amino acids constituted 13% of the water-soluble fraction. Free amino acids isolated from the water-soluble fraction composed of arginine, phenylalanine, threonine, and asparagine 3.9, 2.7, 2.6 and 2.4% of the water-soluble fraction, respectively. We discuss the implications of these findings for understanding the nature and use of the sea lamprey alarm cue in conservation activities

The effect of putrescine on space use and activity in sea lamprey (Petromyzon marinus).

Fish use odor to avoid exposure to predation and disease. Harnessing these odors as repellents is proving useful for management initiatives that conserve native species or control invasive populations. Here, we evaluated the behavioral response of invasive sea lamprey to putrescine, a decay molecule that many prey organisms avoid. Putrescine is found in tissue extracts that contain sea lamprey alarm cue, and human saliva, two mixtures known to elicit flight and avoidance responses in migratory sea lamprey. We used two behavioral assays to evaluate metrics of repellency: behavioral preference (space use) and change in activity rates and found context-dependent results. In smaller assays with individual fish, we found that putrescine had no effect on sea lamprey activity but did induce avoidance. In larger assays with multiple animals, sea lamprey did not avoid putrescine. Our results also showed consistent changes in activity and avoidance behavior in sea lamprey exposed to alarm cue in the smaller assay, concluding that this design could prove useful as a high-throughput screening tool. We also investigated a novel odor identified in sea lamprey skin, petromyzonacil, and found no behavioral effects to this odor on its own or in synergy with putrescine. Our results show limited evidence that putrescine acts as robust repellent for sea lamprey and highlight the importance of environmental context when interpreting avoidance behavior in laboratory settings

Chemical Characterization of Lipophilic Constituents in the Skin of Migratory Adult Sea Lamprey from the Great Lakes Region

<div><p>The sea lamprey (<i>Petromzons marinus</i>) is an invasive ectoparasite of large-bodied fishes that adversely affects the fishing industry and ecology of the Laurentian Great Lakes. Lipid content in the whole sea lamprey and muscles, liver and kidney of metamorphosing larval stages has been reported. Similarly, the fatty acid profile of the rope tissues of sexually-mature male sea lampreys has also been reported. The average body weight of a sub-adult migratory sea lamprey is 250 g, which includes 14.4% skin (36 g). Our preliminary extraction data of an adult sea lamprey skin revealed that it contained approximately 8.5% of lipophilic compounds. Lamprey skin is home to a naturally aversive compound (an alarm cue) that is being developed into a repellent for use in pest management. As part of an ongoing investigation to identify the chemical structure of the sea lamprey alarm cue, we extracted the skin with water and methanol, respectively. The methanolic extract (1.55%) contained exclusively lipophilic compounds and did not include the alarm cue. We chemically characterized all compounds present in the methanolic extract as cholesterol esters (CE), tri- and di-glycerides (TG and DG), cholesterol, free fatty acids (FFA) and minor amounts of plasticizers. The free fatty acids fraction was composed of saturated (41.8%), monounsaturated (40.7%) and polyunsaturated (17.4%) fatty acids, respectively. The plasticizers characterized were phthalate and benzoate and found to be 0.95 mg and 2.54 mg, respectively, per adult sea lamprey skin. This is the first report of the chemical characterization of all the lipophilic constituents in the skin of sub-adult migratory sea lamprey. The CEs isolated and characterized from sea lamprey skin are also for the first time.</p></div

Lipid Peroxidation and Cyclooxygenase Enzyme Inhibitory Compounds from <i>Prangos haussknechtii</i>

Purification of extracts from <i>Prangos haussknechtii</i> Bioss afforded prenylated coumarins <b>1</b> and <b>2</b>, monoterpenoid <b>3</b>, amino acid derivative <b>4</b>, and seven known compounds. Spectroscopic methods permitted establishment of the structures and relative configuration of these compounds. The pure isolates were tested for antioxidant and anti-inflammatory activities using lipid peroxidation (LPO), 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and cyclooxygenase (COX-1 and -2) enzyme inhibitory assays. Compounds <b>1</b>–<b>4</b> inhibited LPO with IC₅₀ values between 43 and 114 μM and reduced MTT to formazan blue between 48 and 128 μM. In anti-inflammatory assays using cyclooxygenase enzymes, COX-1 and -2, these compounds showed inhibition, with IC₅₀ values ranging from 34 to 56 μM

Chemical structures of free fatty acids (FFA) characterized in sea lamprey skin.

<p>Chemical structures of free fatty acids (FFA) characterized in sea lamprey skin.</p

Relative abundance of free fatty acids in sea lamprey skin.

<p>Relative abundance of free fatty acids in sea lamprey skin.</p

¹H and ¹³C NMR spectral data of cholesterol esters (CE) 1–4^a^,^b.

<p>¹H and ¹³C NMR spectral data of cholesterol esters (CE) 1–4<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0168609#t001fn001" target="_blank">^a</a>^,<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0168609#t001fn002" target="_blank">^b</a>.</p

Chemical structures of isolates from methanolic extract: Compund 5 ((1,3-Di(cis-9-hexadecenoyl)-2-hexadecanoyl-glycerol), compound 6 (bis-(2-ethylhexyl) terephthalate), compound 7 (diethylene glycol dibenzoate), compound 8 (1,3-di(cis-9-octadecenoyl)glycerol), compound 9 (1,2-di(cis-9-octadecenoyl)glycerol), compound 10 (cholesterol).

<p>Chemical structures of isolates from methanolic extract: Compund 5 ((1,3-Di(cis-9-hexadecenoyl)-2-hexadecanoyl-glycerol), compound 6 (bis-(2-ethylhexyl) terephthalate), compound 7 (diethylene glycol dibenzoate), compound 8 (1,3-di(cis-9-octadecenoyl)glycerol), compound 9 (1,2-di(cis-9-octadecenoyl)glycerol), compound 10 (cholesterol).</p