Identification of a female sex pheromone in Carcinus maenas

Jd Hardege,Ct Müller,M Harley,M Lorch,R Bublitz,N Fletcher,K Welham,Hd Bartels-Hardege,T Walther,Ma Smith,Ja Terschak,L Davidson,D Hayden

doi:10.3354/meps09226

Abstract

Despite major progress in our understanding of animal signaling systems, the identification of chemical signals in aquatic organisms is still in its infancy. Exemplary for this is the lack of structural knowledge of crustacean sex pheromones despite their initial description in crabs almost 40 yr ago. We hypothesized that species in which the reproductive event is linked to a short window of mating opportunities centered around the time of ecdysis would be ideal to purify and identify such a cue. Here we present the first identification of a crustacean sex pheromone, the female signal produced by the green crab Carcinus maenas from both conditioned seawater and female urine. We used a bioassay-driven purification scheme combined with a candidate approach focusing on excreted compounds that changed through the course of the female molt cycle. Uridine diphosphate (UDP), a nucleotide accumulated from UDP-N-acetylglucosamine during chitin biosynthesis, is the major component of the female crab pheromone and induced all key characteristics of male sexual behavior in bioassays (i.e. pre- and post-copulatory guarding of the female and initiation of mating) at a threshold of 10–5 M UDP in seawater. The identification of a nucleotide pheromone in crustaceans will enable future studies on signal specificity, biological function, biosynthesis, reception, and evolution as well as focus its potential use in pest control and aquaculture, thus allowing for a major expansion of crustacean chemical and behavioral ecology research that was hindered by the lack of structural knowledge.

Highlights

Ryan (1966) demonstrated in an elegant series of experiments conducted more than 40 yr ago that female sex pheromones influence reproductive behavior in malacostracan crabs, the chemical nature of these cues remains unknown (Hardege et al 2002)
Since our initial hypothesis was that the female sex pheromone production is linked to the female molt and potentially even the biochemical/ physiological changes during the molting process such as increased chitin biosynthesis, we examined whether male urine during their epidemic molt in spring contains Uridine diphosphate (UDP)
Zhang et al (2011) recently reported the identity of cuticle-bound contact sex pheromones in the simultaneously hermaphroditic shrimp Lysmata bogessi. These cuticluar hydrocarbons, of which (Z)-9octadeceneamide is the key compound within a pheromone bouquet, induced shrimp mating behavior after the sexual partners initially met through the attractiveness of a yet unknown distance pheromone

Summary

Introduction

Ryan (1966) demonstrated in an elegant series of experiments conducted more than 40 yr ago that female sex pheromones influence reproductive behavior in malacostracan crabs, the chemical nature of these cues remains unknown (Hardege et al 2002). This has been attributed to 2 problems: the biological assays are not able to effectively discriminate between signals derived from the opposite sex and other cues such as food (Dunham 1978, 1988), and the analytical methods to purify pheromones from an aqueous environment are challenging (Hardege et al 2002, Hayden et al 2007). This species, known as the shore crab, has recently been introduced to Australia, the USA, and South America (Grosholz & Ruiz 1995), resulting in ecological and economic damage to native ecosystems and local aquaculture industries

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