Feminization of Male Brown Treesnake Methyl Ketone Expression via Steroid Hormone Manipulation

Abstract

Pheromones are useful tools for the management of invasive invertebrates, but have proven less successful in field applications for invasive vertebrates. The brown treesnake, Boiga irregularis, is an invasive predator that has fundamentally altered the ecology of Guam. The development of control tools to manage Boiga remains ongoing. Skin-based, lipophilic pheromone components facilitate mating in brown treesnakes, with females producing the same long-chain, saturated and monounsaturated (ketomonoene) methyl ketones known to function as pheromones in garter snakes, Thamnophis sirtalis. Boiga also express novel, diunsaturated methyl ketones (ketodienes) with a purported function as a sex pheromone. In our study, we implanted 17 β-estradiol in adult male brown treesnakes in order to manipulate methyl ketone expression as sex attractants, an effect that would mirror findings with garter snakes. Specifically, estrogen promoted production of two ketomonoenes, pentatriaconten-2-one and hexatriaconten-2-one, and suppressed production of one ketodiene, heptatriacontadien-2-one. In bioassays, estrogen-implanted males elicited tongue-flicking and chin rubbing behavior from unmanipulated males, though the responses were weaker than those elicited by females. On Guam, wild males exhibited greatest responses to whole female skin lipid extracts and only weak responses to the methyl ketone fractions from females and implanted males. Our results suggest that sex identity in brown treesnakes may be conferred by the ratio of ketomonoenes (female) to ketodienes (male) from skin lipids and may be augmented by a sex-specific endocrine signal (estradiol). However, a blend of long-chain methyl ketones alone is not sufficient to elicit maximal reproductive behaviors in male Boiga.

Cancer-associated fibroblasts promote prostate tumor growth and progression through upregulation of cholesterol and steroid biosynthesis

“…This enzyme regulates the production of ketone bodies in the mitochondria [19]. Ketone bodies can be used by cells as compensatory energy sources during fast tumor growth [36] and converted to acetyl CoA and transduced to Krebs cycle (reviewed by [37]) or further used for cholesterol synthesis [38,39]. Saraon and colleagues showed that HMGCS2 was about 9-fold higher in LNCaPabl compared to parental LNCaP cells, suggesting a link between elevated expression of HMGCS2 and CRPC [40].…”

Genomic pedigree reconstruction identifies predictors of mating and reproductive success in an invasive vertebrate

“…Trappability is also related to the ability of an individual to detect chemical stimuli from baited traps. BTS use olfactory cues to find prey in baited traps (Shivik, 1998), and male BTS also use olfactory cues (i.e., female pheromones) to find mates (Greene et al, 2001;Parker, Patel, Zachry, & Kimball, 2018) and elicit courtship (Greene & Mason, 1998). Therefore, it is likely that males with better chemosensory abilities will not only find baited traps more frequently but also have greater success in finding and acquiring mates.…”

Chemical Isolation, Quantification, and Separation of Skin Lipids from Reptiles

“…The isolation of these skin lipids has utility in research focused on evolutionary patterns and mechanisms of chemical communication, in addition to understanding the waterproofing role of lipids in the evolution of terrestrial life 2,3,4 . Further, many reptiles, especially squamates (lizards, snakes), are invasive species of concern in sensitive ecosystems, and the development of pheromone-based lures to improve trapping and removal is ongoing 5,6 . The impermeability of reptile skin facilitates the extraction of the lipids present to obtain relatively pure extractions of a potentially robust source of chemical signals.…”

“…The impermeability of reptile skin facilitates the extraction of the lipids present to obtain relatively pure extractions of a potentially robust source of chemical signals. The principle steps for quantifying reptile skin lipids in the described protocol include extraction, total lipid determination, and fractionation via column chromatography 1,6,7 . The methods have been used routinely as they yield bioactive isolates that explain much about mate choice and selection, especially in snakes 2 .…”

“…In lipid chromatography, the fractions progress in polarity at some standardized sequence by increasing the relative amount of polar solvent (e.g., diethyl ether) in nonpolar solvent (typically expressed as a percentage: 0%, 2%, 4% ether, etc.) 6,7,8 . Though methods like thin-layer chromatography (TLC) can be used to separate lipids in a mixture and are simpler, column chromatography is preferred because it uses a closed system, is easy to control, can separate more concentrated mixtures, and is compatible with multiplexing for efficiency.…”