Observation on the composition and biosynthesis of egg wax lipids in the cattle tick,Boophilus microplus

Abstract

The biosynthesis of wax lipids by Gené's organ, the egg waxing organ in ticks, was investigated. Gené's organ, a complex dermal gland system, applies a superficial wax layer to the eggs during oviposition which prevents desiccation and is essential for egg viability. The detailed anatomy and histology of the three gland cell types are unambiguously described. Serial sectioning of ticks showed that all three gland cell types are capable of contributing to the egg wax. The wax synthetic ability of these three gland types was characterized. The composition of wax lipids extracted from the surface egg wax, and from the three types of wax gland dissected from ovipositing ticks, was analysed using thin-layer and gas-liquid chromatography. Injection of ovipositing ticks with radiolabelled acetate resulted in the incorporation of the label into wax lipids by gland cells of Gené's organ. The egg wax was a complex mixture of long-chain alkanes and fatty acid esters. The gland cells contained a greater proportion of shorter chain alkanes than were present in the egg surface wax. Some unsaturated long-chain fatty acids were present, and these were more abundant in the gland cells than in the surface wax of oviposited eggs, suggesting that oxidation occurs after oviposition. The results confirm that the tubular glands, acinar accessory glands and lobular glands of Gené's organ all contribute to the egg waxes, although the lipid components differed in relative abundance. The results are also consistent with alkane synthesis from fatty acids in Gené's organ by a chain-elongation-decarboxylation pathway.

In-vitro anticandidial efficacy of tick egg wax from Hyalomma marginatum, Rhipicephalus bursa and Dermacentor marginatus

“…It has been reported that the wax, which thickness varies between 0.5-2.0 µm (21), has an average amount of 24 mg per gram eggs mainly according to the tick species (22). The wax is known to have some vital missions for the eggs such as holding the egg mass together, protecting the eggs against drying, environmental physical, chemical or microbiological factors, and ensuring the proper gas exchange between eggs and air (20,21,23,24).…”

Antimicrobial activity in the egg wax of the African cattle tick Amblyomma hebraeum (Acari: Ixodidae)

“…The gland is composed of three defined sections: tubular, lobed and acinar; all three sections appear to contribute components of the wax (Booth 1992). Not surprisingly, the gland shows the ultrastructural hallmarks of a lipid-secreting tissue (abundance of smooth endoplasmic reticulum and prominent Golgi bodies with numerous budding membrane-bound vesicles and lipid droplets (Booth et al 1984;Booth 1989).…”

“…Booth (1992) suggested that the waxy secretion may also have other functions, including constituting a physical barrier against microorganisms. To date, most physiological studies on Gé né 's organ have focused on demonstrating waterproofing by the wax secretion (Lees and Beament 1948), on the organ's morphology, histology and ultrastructure (Booth et al 1984;Booth 1989;Schö l et al 2001), on determining the composition and general biosynthesis pathway of the lipid secretion (Booth 1989(Booth , 1992, on the ultrastructure and physiology of the retractor muscles (Booth et al 1985) and on the pharmacological control of egg wax secretion (Booth et al 1986). Kü hn et al (1996) detected a sialic acid specific lectin in various tissues of Ixodes ricinus, including the invaginations of Gé né 's organ.…”

A steroidal molecule present in the egg wax of the tick Rhipicephalus (Boophilus) microplus inhibits bacterial biofilms

“…Rhipicephalus (Boophilus) microplus eggs have a wax coating which prevents desiccation (Lees and Beament, ; Booth, ) and acts as a barrier against microorganisms (Booth, ; Arrieta et al ., ; Esteves et al ., ; Yu et al ., ). Rhipicephalus microplus lays eggs in the soil (Booth, ), an environment abundant in bacteria and prone to biofilm formation.…”

“…Rhipicephalus (Boophilus) microplus eggs have a wax coating which prevents desiccation (Lees and Beament, ; Booth, ) and acts as a barrier against microorganisms (Booth, ; Arrieta et al ., ; Esteves et al ., ; Yu et al ., ). Rhipicephalus microplus lays eggs in the soil (Booth, ), an environment abundant in bacteria and prone to biofilm formation. Accordingly, we confirmed the hypothesis that, in addition to the known antibiotic activity (Arrieta et al ., ; Esteves et al ., ; Yu et al ., ), tick eggs also possess specific mechanisms to prevent biofilm formation and we identified the molecule responsible for this activity.…”