Origin, structure and functional transition of sex pheromone components in a false widow spider

Abstract

Female web-building spiders disseminate pheromone from their webs that attracts mate-seeking males and deposit contact pheromone on their webs that induces courtship by males upon arrival. The source of contact and mate attractant pheromone components, and the potential ability of females to adjust their web’s attractiveness, have remained elusive. Here, we report three new contact pheromone components produced by female false black widow spiders, Steatoda grossa: N-4-methylvaleroyl-O-butyroyl-L-serine, N-4-methylvaleroyl-O-isobutyroyl-L-serine and N-4-methylvaleroyl-O-hexanoyl-L-serine. The compounds originate from the posterior aggregate silk gland, induce courtship by males, and web pH-dependently hydrolyse at the carboxylic-ester bond, giving rise to three corresponding carboxylic acids that attract males. A carboxyl ester hydrolase (CEH) is present on webs and likely mediates the functional transition of contact sex pheromone components to the carboxylic acid mate attractant pheromone components. As CEH activity is pH-dependent, and female spiders can manipulate their silk’s pH, they might also actively adjust their webs’ attractiveness.

Non-targeted metabolomics aids in sex pheromone identification: a proof-of-concept study with the triangulate cobweb spider, Steatoda triangulosa

“…Virgin females and naïve adult males were randomly chosen for web-building and bioassays, respectively. As female spiders produce little silk per day, we extended the web-building period, allowing each female to build her web for seven days, instead of three days 34 , on a triangular prism (10 × 10 × 10 cm) of bamboo skewers (Goodcook, USA) 36 . Webs were collected using a methanol-cleaned glass rod and were extracted overnight in 25 µL/web of acetonitrile (ACN, 99%, Sigma-Aldrich, USA).…”

“…During courtship, males cut and bundle up sections of the female’s web, adding their own silk in the process 36 . Contact sex pheromone components have been identified for females of the redback spider, Latrodectus hasselti [ N -3-methylbutyroyl- O -( S )-2-methylbutyroyl- l -serine methyl ester ( 1 )] 18 , the western black widow spider, L. hesperus [ N -3-methylbutanoyl- O -isobutyroyl- l -serine methyl ester ( 2 )] 33 , the brown widow, L. geometricus [ N -3-methylbutyroyl- O -propionyl- l -serine-methyl ester ( 3 )] 35 , and the false black widow spider, Steatoda grossa [ N -4-methylvaleroyl- O -butyroyl- l -serine ( 4 ), N -4-methylvaleroyl- O -isobutyroyl- l -serine ( 5 ) and N -4-methylvaleroyl- O -hexanoyl- l -serine ( 6 )] 34 (Fig. 2 a).…”

“…In S. grossa, contact pheromone components—web pH-dependently—hydrolyse at the ester bond and give rise to airborne mate-attractant pheromone components: butyric acid ( 7 ), isobutyric acid ( 8 ), and hexanoic acid ( 9 ) (Fig. 2 a) 34 . N -4-Methylvaleroyl- l -serine ( 10 ), as another hydrolysis breakdown product, accumulates on webs and has no pheromonal activity 34 .…”

“…2 a) 34 . N -4-Methylvaleroyl- l -serine ( 10 ), as another hydrolysis breakdown product, accumulates on webs and has no pheromonal activity 34 .

Figure 2 Phylogeny and comparison of pheromone components (contact & airborne) in widow spiders (Latrodectinae).

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Figure 2 Phylogeny and comparison of pheromone components (contact & airborne) in widow spiders (Latrodectinae). ( a ) Previously known pheromone components of Latrodectus hasselti 18 , L. hesperus 33 , L. geometricus 35 , and Steatoda grossa 34 : N -3-methylbutyroyl- O -( S )-2-methylbutyroyl- l -serine methyl ester ( 1 ), N -3-methylbutanoyl- O -isobutyroyl- l -serine methyl ester ( 2 ), N -3-methylbutyroyl- O -isobutyroyl- l -serine-methyl ester ( 3 ), N -4-methylvaleroyl- O -butyroyl- l -serine ( 4 ), N -4-methylvaleroyl- O -isobutyroyl- l -serine ( 5 ), and N -4-methylvaleroyl- O -hexanoyl- l -serine ( 6 ). The contact pheromone components 4–6 of S. grossa hydrolyse at the ester bond and give to three airborne mate-attractant pheromone components [butyric acid ( 7 ), isobutyric acid ( 8 ), and hexanoic acid ( 9 )], whereas the amide N -4-methylvaleroyl- l -serine ( 10 ), as another hydrolysis breakdown product, remains on webs and has no behavioural activity.

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