Insect Biochemistry and Molecular Biology 30 2000 601–608 www.elsevier.comlocateibmb
Production, regeneration and biochemical precursors of the major components of the defensive secretion of Eurycotis floridana
Dictyoptera, Polyzosteriinae
Jean-Pierre Farine , Claude Everaerts, Dehbia Abed, Remy Brossut
Universite´ de Bourgogne, C.N.R.S, U.M.R. 5548, 6 Bd Gabriel, 21000 Dijon, France Received 2 June 1999; received in revised form 15 February 2000; accepted 25 February 2000
Abstract
The defensive secretion of the cockroach Eurycotis floridana contains three main components, E-2-hexenal, E-2-hexenol and E-2-hexenoic acid, which represented about 98 of the organic phase. The quantity of the aldehyde, alcohol, and acid present
in the defensive secretion increased rapidly for 60 days from the imaginal moult. Following artificial discharge, the males were able to regenerate their initial volume of secretion over a 30 day period. To investigate the possible routes of biosynthesis of the
three components, E. floridana was injected with 14C-labeled fatty acids and acetate, and the incorporation of 14C into the three components were quantified 1, 6, and 24 h after milking. Our results revealed that oleic, linoleic, linolenic and palmitic acids,
which constitute part of the fat body of the insect, were incorporated to the same degree into the three main components, but very slowly compared to acetate. Although it has not been possible to identify the exact route of aldehyde, alcohol and acid biosynthesis,
our findings suggests that E-2-hexenal, E-2-hexenol and E-2-hexenoic acid are preferentially biosynthesized de novo from acetate.
2000 Elsevier Science Ltd. All rights reserved.
Keywords: Eurycotis floridana ; Dictyoptera; Exocrine glands; Pheromones; Defence; Biosynthesis
1. Introduction
When alarmed, adults of the large wingless cockroach Eurycotis floridana
emit a defensive secretion from the sternal gland, which opens medially on the intersegmen-
tal membrane between the 6th and 7th abdominal ster- nites Stay, 1957. The secretion is a mixture of an
organic and aqueous phase Roth et al., 1956; Dateo and Roth, 1967a,b; Brossut, 1983. While the aqueous phase
contains gluconic acid, gluconolactone and glucose Dateo and Roth, 1967a; Brossut, 1983, the organic
phase is a mixture of about 40 constituents of which E- 2-hexenal, E-2-hexenol and E-2-hexenoic acid are the
main components Farine et al., 1997. Fifteen-day-old males contained about 20 to 30
µ l of secretion with 15
mg E-2-hexenal, 687 µ
g E-2-hexenol and 31 µ
g E- 2-hexenoic acid, making up about 93, 5 and 0.3 of the
Corresponding author. Tel: +
33-03-80-39-62-95; fax: +
33-03-80- 39-62-89.
E-mail address: jean-pierre.farineu-bourgogne.fr J.-P. Farine.
0965-174800 - see front matter
2000 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 5 - 1 7 4 8 0 0 0 0 0 6 5 - 5
organic phase of the secretion, respectively Farine et al., 1997.
Following discharge, the defensive secretion must be quickly resynthesized. The metabolic origin of most
defensive compounds is unknown. It appears that the majority of them are synthesized de novo rather than
incorporated from food sources Blum 1981, 1987. Many biosynthetic pathways of semiochemicals have
been shown to be correlated to the biosynthesis of fatty acids. All of these biosynthetic pathways consist of a
combination of three processes. The first, synthesis of the precursor fatty acid from acetate, has been observed
in almost all species studied. The second process, func- tionalization of the fatty acid, consists of the introduction
of a second functionality such as a double bond or a hydroxyl group. In many cases, the chain length of the
precursor fatty acid does not correspond to that of the final product, because the precursor fatty acid is chain
shortened or elongated before or after functionalization. The last process in the biosynthesis of fatty acid-derived
semiochemicals is the modification of the carboxyl group.
602 J.-P. Farine et al. Insect Biochemistry and Molecular Biology 30 2000 601–608
Like other insects, some cockroaches are able to syn- thesize de novo all their linear fatty acids with 14, 16
or 18 carbon atoms Cripps et al., 1986; Jurenka et al., 1987; de Renobales et al., 1987. In the fat body of males
and females of E. floridana, palmitic C16:0, oleic C18:1 and linoleic C18:2 acids are the most abundant
fatty acids respectively, 185618 whereas linolenic C18:3 and stearic C18:0 acids represent only a few
percent respectively, traces4 Bade, 1964. After ingestion of [1-
14
C] acetate, both sexes are able to biosynthesize by condensation of C
2
units all the fatty acids encountered Bade, 1964.
In the first part of this study, the defensive secretion of males of E. floridana was investigated qualitatively
and quantitatively over a two-month period. In the second part, the rate of refilling of the defensive glands
after artificial discharge was quantified. Comparatively to many insect species where the sex pheromones are
derived to fatty acids Tillman et al., 1999, the possible role of the five linear fatty acids encountered in the fat
body of E. floridana, and that of acetate as possible pre- cursors of the major components of the defensive
secretion, were also investigated.
2. Materials and methods
