TRPA5 encodes a thermosensitive ankyrin ion channel receptor in a triatomine insect

As ectotherms, insects need heat-sensitive receptors to monitor environmental temperatures and facilitate thermoregulation. We show that TRPA5, a class of ankyrin transient receptor potential (TRP) channels absent in dipteran genomes, may function as insect heat receptors. In the triatomine bug Rhodnius prolixus (order: Hemiptera), a vector of Chagas disease, the channel RpTRPA5B displays a uniquely high thermosensitivity, with biophysical determinants including a large channel activation enthalpy change (72 kcal/mol), a high temperature coefficient (Q10 = 25), and in vitro temperature-induced currents from 53°C to 68°C (T0.5 = 58.6°C), similar to noxious TRPV receptors in mammals. Monomeric and tetrameric ion channel structure predictions show reliable parallels with fruit fly dTRPA1, with structural uniqueness in ankyrin repeat domains, the channel selectivity filter, and potential TRP functional modulator regions. Overall, the finding of a member of TRPA5 as a temperature-activated receptor illustrates the diversity of insect molecular heat detectors.

Sensory evolution: A dazzling hack to cope with bright light in owls and whales

When exposed to sudden changes in light intensity, rod-dominated retinas of animals with highly sensitive dim-vision risk critical damage. A new study finds that owls and deep-diving whales have evolved an identical photoprotection mechanism to delay toxic all-trans retinal release, a discovery with potential medical implications.

A hypothesis for robust polarization vision: An example from the Australian Imperial Blue butterfly, Jalmenus evagoras

The Australian lycaenid butterfly, Jalmenus evagoras, has iridescent wings that are sexually dimorphic, spectrally and in their degree of polarization, suggesting that these properties are likely to be important in mate recognition. We first describe the results of a field experiment showing that free-flying individuals of J. evagoras discriminate between visual stimuli that vary in polarization content in blue wavelengths but not in others. We then present detailed reflectance spectrophotometry measurements of the polarization content of male and female wings, showing that female wings exhibit blue-shifted reflectance, with a lower degree of polarization relative to male wings. Finally, we describe a novel method for measuring alignment of ommatidial arrays: By measuring variation of depolarized eyeshine intensity from patches of ommatidia as a function of eye rotation, we show that a) individual rhabdoms contain mutually perpendicular microvilli; b) many rhabdoms in the array have their microvilli misaligned with respect to neighboring rhabdoms by as much as 45°; c) the misaligned ommatidia are useful for robust polarization detection. By mapping the distribution of the ommatidial misalignments in eye patches of J. evagoras, we show that males and females exhibit differences in the extent to which ommatidia are aligned. Both the number of misaligned ommatidia suitable for robust polarization-detection, and the number of aligned ommatidia suitable for edge-detection, vary with respect to both sex and eye-patch elevation. Thus, J. evagoras exhibits finely-tuned ommatidial arrays suitable for perception of polarized signals, likely to match sex-specific life history differences in the utility of polarized signals.

Molecular advances to study the function, evolution and spectral tuning of arthropod visual opsins

Visual opsins of vertebrates and invertebrates diversified independently and converged to detect ultraviolet to long wavelengths (LW) of green or red light. In both groups, colour vision largely derives from opsin number, expression patterns and changes in amino acids interacting with the chromophore. Functional insights regarding invertebrate opsin evolution have lagged behind those for vertebrates because of the disparity in genomic resources and the lack of robust in vitro systems to characterize spectral sensitivities. Here, we review bioinformatic approaches to identify and model functional variation in opsins as well as recently developed assays to measure spectral phenotypes. In particular, we discuss how transgenic lines, cAMP-spectroscopy and sensitive heterologous expression platforms are starting to decouple genotype–phenotype relationships of LW opsins to complement the classical physiological-behavioural-phylogenetic toolbox of invertebrate visual sensory studies. We illustrate the use of one heterologous method by characterizing novel LW Gq opsins from 10 species, including diurnal and nocturnal Lepidoptera, a terrestrial dragonfly and an aquatic crustacean, expressing them in HEK293T cells, and showing that their maximum absorbance spectra (λ_max) range from 518 to 611 nm. We discuss the advantages of molecular approaches for arthropods with complications such as restricted availability, lateral filters, specialized photochemistry and/or electrophysiological constraints.

This article is part of the theme issue ‘Understanding colour vision: molecular, physiological, neuronal and behavioural studies in arthropods’.

Evolutionary trade-offs between male secondary sexual traits revealed by a phylogeny of the hyperdiverse tribe Eumaeini (Lepidoptera: Lycaenidae)

Male butterflies in the hyperdiverse tribe Eumaeini possess an unusually complex and diverse repertoire of secondary sexual characteristics involved in pheromone production and dissemination. Maintaining multiple sexually selected traits is likely to be metabolically costly, potentially resulting in trade-offs in the evolution of male signals. However, a phylogenetic framework to test hypotheses regarding the evolution and maintenance of male sexual traits in Eumaeini has been lacking. Here, we infer a comprehensive, time-calibrated phylogeny from 379 loci for 187 species representing 91% of the 87 described genera. Eumaeini is a monophyletic group that originated in the late Oligocene and underwent rapid radiation in the Neotropics. We examined specimens of 818 of the 1096 described species (75%) and found that secondary sexual traits are present in males of 91% of the surveyed species. Scent pads and scent patches on the wings and brush organs associated with the genitalia were probably present in the common ancestor of Eumaeini and are widespread throughout the tribe. Brush organs and scent pads are negatively correlated across the phylogeny, exhibiting a trade-off in which lineages with brush organs are unlikely to regain scent pads and vice versa. In contrast, scent patches seem to facilitate the evolution of scent pads, although they are readily lost once scent pads have evolved. Our results illustrate the complex interplay between natural and sexual selection in the origin and maintenance of multiple male secondary sexual characteristics and highlight the potential role of sexual selection spurring diversification in this lineage.

The evolution of red color vision is linked to coordinated rhodopsin tuning in lycaenid butterflies

Color vision has evolved multiple times in both vertebrates and invertebrates and is largely determined by the number and variation in spectral sensitivities of distinct opsin subclasses. However, because of the difficulty of expressing long-wavelength (LW) invertebrate opsins in vitro, our understanding of the molecular basis of functional shifts in opsin spectral sensitivities has been biased toward research primarily in vertebrates. This has restricted our ability to address whether invertebrate Gq protein-coupled opsins function in a novel or convergent way compared to vertebrate Gt opsins. Here we develop a robust heterologous expression system to purify invertebrate rhodopsins, identify specific amino acid changes responsible for adaptive spectral tuning, and pinpoint how molecular variation in invertebrate opsins underlie wavelength sensitivity shifts that enhance visual perception. By combining functional and optophysiological approaches, we disentangle the relative contributions of lateral filtering pigments from red-shifted LW and blue short-wavelength opsins expressed in distinct photoreceptor cells of individual ommatidia. We use in situ hybridization to visualize six ommatidial classes in the compound eye of a lycaenid butterfly with a four-opsin visual system. We show experimentally that certain key tuning residues underlying green spectral shifts in blue opsin paralogs have evolved repeatedly among short-wavelength opsin lineages. Taken together, our results demonstrate the interplay between regulatory and adaptive evolution at multiple Gq opsin loci, as well as how coordinated spectral shifts in LW and blue opsins can act together to enhance insect spectral sensitivity at blue and red wavelengths for visual performance adaptation.

A moth pheromone brewery: production of (Z)-11-hexadecenol by heterologous co-expression of two biosynthetic genes from a noctuid moth in a yeast cell factory

BACKGROUND

Moths (Lepidoptera) are highly dependent on chemical communication to find a mate. Compared to conventional unselective insecticides, synthetic pheromones have successfully served to lure male moths as a specific and environmentally friendly way to control important pest species. However, the chemical synthesis and purification of the sex pheromone components in large amounts is a difficult and costly task. The repertoire of enzymes involved in moth pheromone biosynthesis in insecta can be seen as a library of specific catalysts that can be used to facilitate the synthesis of a particular chemical component. In this study, we present a novel approach to effectively aid in the preparation of semi-synthetic pheromone components using an engineered vector co-expressing two key biosynthetic enzymes in a simple yeast cell factory.

RESULTS

We first identified and functionally characterized a ∆11 Fatty-Acyl Desaturase and a Fatty-Acyl Reductase from the Turnip moth, Agrotis segetum. The ∆11-desaturase produced predominantly Z11-16:acyl, a common pheromone component precursor, from the abundant yeast palmitic acid and the FAR transformed a series of saturated and unsaturated fatty acids into their corresponding alcohols which may serve as pheromone components in many moth species. Secondly, when we co-expressed the genes in the Brewer's yeast Saccharomyces cerevisiae, a set of long-chain fatty acids and alcohols that are not naturally occurring in yeast were produced from inherent yeast fatty acids, and the presence of (Z)-11-hexadecenol (Z11-16:OH), demonstrated that both heterologous enzymes were active in concert. A 100 ml batch yeast culture produced on average 19.5 μg Z11-16:OH. Finally, we demonstrated that oxidized extracts from the yeast cells containing (Z)-11-hexadecenal and other aldehyde pheromone compounds elicited specific electrophysiological activity from male antennae of the Tobacco budworm, Heliothis virescens, supporting the idea that genes from different species can be used as a molecular toolbox to produce pheromone components or pheromone component precursors of potential use for control of a variety of moths.

CONCLUSIONS

This study is a first proof-of-principle that it is possible to "brew" biologically active moth pheromone components through in vitro co-expression of pheromone biosynthetic enzymes, without having to provide supplementary precursors. Substrates present in the yeast alone appear to be sufficient.

Functional consequences of sequence variation in the pheromone biosynthetic gene pgFAR for Ostrinia moths

Pheromones are central to the mating systems of a wide range of organisms, and reproductive isolation between closely related species is often achieved by subtle differences in pheromone composition. In insects and moths in particular, the use of structurally similar components in different blend ratios is usually sufficient to impede gene flow between taxa. To date, the genetic changes associated with variation and divergence in pheromone signals remain largely unknown. Using the emerging model system Ostrinia, we show the functional consequences of mutations in the protein-coding region of the pheromone biosynthetic fatty-acyl reductase gene pgFAR. Heterologous expression confirmed that pgFAR orthologs encode enzymes exhibiting different substrate specificities that are the direct consequences of extensive nonsynonymous substitutions. When taking natural ratios of pheromone precursors into account, our data reveal that pgFAR substrate preference provides a good explanation of how species-specific ratios of pheromone components are obtained among Ostrinia species. Moreover, our data indicate that positive selection may have promoted the observed accumulation of nonsynonymous amino acid substitutions. Site-directed mutagenesis experiments substantiate the idea that amino acid polymorphisms underlie subtle or drastic changes in pgFAR substrate preference. Altogether, this study identifies the reduction step as a potential source of variation in pheromone signals in the moth genus Ostrinia and suggests that selection acting on particular mutations provides a mechanism allowing pheromone reductases to evolve new functional properties that may contribute to variation in the composition of pheromone signals.

Sex pheromone evolution is associated with differential regulation of the same desaturase gene in two genera of leafroller moths

Chemical signals are prevalent in sexual communication systems. Mate recognition has been extensively studied within the Lepidoptera, where the production and recognition of species-specific sex pheromone signals are typically the defining character. While the specific blend of compounds that makes up the sex pheromones of many species has been characterized, the molecular mechanisms underpinning the evolution of pheromone-based mate recognition systems remain largely unknown. We have focused on two sets of sibling species within the leafroller moth genera Ctenopseustis and Planotortrix that have rapidly evolved the use of distinct sex pheromone blends. The compounds within these blends differ almost exclusively in the relative position of double bonds that are introduced by desaturase enzymes. Of the six desaturase orthologs isolated from all four species, functional analyses in yeast and gene expression in pheromone glands implicate three in pheromone biosynthesis, two Δ9-desaturases, and a Δ10-desaturase, while the remaining three desaturases include a Δ6-desaturase, a terminal desaturase, and a non-functional desaturase. Comparative quantitative real-time PCR reveals that the Δ10-desaturase is differentially expressed in the pheromone glands of the two sets of sibling species, consistent with differences in the pheromone blend in both species pairs. In the pheromone glands of species that utilize (Z)-8-tetradecenyl acetate as sex pheromone component (Ctenopseustis obliquana and Planotortrix octo), the expression levels of the Δ10-desaturase are significantly higher than in the pheromone glands of their respective sibling species (C. herana and P. excessana). Our results demonstrate that interspecific sex pheromone differences are associated with differential regulation of the same desaturase gene in two genera of moths. We suggest that differential gene regulation among members of a multigene family may be an important mechanism of molecular innovation in sex pheromone evolution and speciation.

Chemical signals are prevalent in sexual communication systems, especially within the Lepidoptera where sex pheromones are typically one of the defining characteristics of species. We have isolated six desaturases from two groups of sibling species of leafroller moths belonging to the genera Ctenopseustis and Planotortrix. Functional analyses in yeast and quantitative RT–PCR indicate that three of the desaturases are involved in the biosynthesis of sex pheromone components in these species. One of three enzymes is a Δ10-desaturase that is differentially expressed in the pheromone glands of the two sets of sibling species, consistent with differences in the pheromone blend in both species pairs. In the pheromone glands of species that utilize (Z)-8-tetradecenyl acetate as sex pheromone component (C. obliquana and P. octo), the expression levels of the Δ10-desaturase are significantly higher than pheromone gland expression levels in their sibling species (C. herana and P. excessana). Our results demonstrate that interspecific sex pheromone differences are associated with differential regulation of the same desaturase gene in these two genera of moths. Based on these findings differential gene regulation among members of a multigene family may be an important mechanism of molecular innovation in sex pheromone evolution and speciation.

Terminal fatty-acyl-CoA desaturase involved in sex pheromone biosynthesis in the winter moth (Operophtera brumata)

The winter moth (Operophtera brumata L., Lepidoptera: Geometridae) utilizes a single hydrocarbon, 1,Z3,Z6,Z9-nonadecatetraene, as its sex pheromone. We tested the hypothesis that a fatty acid precursor, Z11,Z14,Z17,19-nonadecanoic acid, is biosynthesized from α-linolenic acid, through chain elongation by one 2-carbon unit, and subsequent methyl-terminus desaturation. Our results show that labeled α-linolenic acid is indeed incorporated into the pheromone component in vivo. A fatty-acyl-CoA desaturase gene that we found to be expressed in the abdominal epidermal tissue, the presumed site of biosynthesis for type II pheromones, was characterized and expressed heterologously in a yeast system. The transgenic yeast expressing this insect derived gene could convert Z11,Z14,Z17-eicosatrienoic acid into Z11,Z14,Z17,19-eicosatetraenoic acid. These results provide evidence that a terminal desaturation step is involved in the winter moth pheromone biosynthesis, prior to the decarboxylation.

Functional flexibility as a prelude to signal diversity?: Role of a fatty acyl reductase in moth pheromone evolution

Sex pheromones are the hallmark of reproductive behavior in moths. Mature females perform the task of mate signaling and release bouquets of odors that attract conspecific males at long range. The pheromone chemistry follows a relatively minimal design but still the combinatorial action of a handful of specialized pheromone production enzymes has resulted in remarkably diverse sexual signals that subtly vary in structure and in number and ratio of components. In a recent article,1 we showed that a single reductase gene (pgFAR) enables the conversion of key biosynthetic fatty-acyl precursors into fatty alcohols, the immediate precursors of the multi-component pheromone in small ermine moths (Lepidoptera: Yponomeutidae). In the light of the widespread usage of multi-component pheromone blends across Lepidoptera, it is likely that the pgFAR biochemical flexibility is a regular feature of the moth pheromone machinery and polyvalent reductase genes are emerging as pivots to promote phenotypic transitions in moth mating signals. In addition, the small ermine moth pgFAR nevertheless contributes to regulating the ratio among components. Here we show that the pgFAR substrate specificity is actually counterbalancing the inherent chain-length preference of an upstream desaturase with Δ11-activity and that the enzymes together modulate the final blend ratio between the Z11-16:OH, Z11-14:OH and E11-14:OH compounds before the final acetylation.

Neofunctionalization in an ancestral insect desaturase lineage led to rare Δ6 pheromone signals in the Chinese tussah silkworm

The Chinese tussah silkworm, Antheraea pernyi (Lepidoptera: Saturniidae) produces a rare dienoic sex pheromone composed of (E,Z)-6,11-hexadecadienal, (E,Z)-6,11-hexadecadienyl acetate and (E,Z)-4,9-tetradecadienyl acetate, and for which the biosynthetic routes are yet unresolved. By means of gland composition analyses and in vivo labeling we evidenced that pheromone biosynthesis towards the immediate dienoic gland precursor, the (E,Z)-6,11-hexadecadienoic acid, involves desaturation steps with Δ(6) and Δ(11) regioselectivity. cDNA cloning of pheromone gland desaturases and heterologous expression in yeast demonstrated that the 6,11-dienoic pheromone is generated from two biosynthetic routes implicating a Δ(6) and Δ(11) desaturase duo albeit with an inverted reaction order. The two desaturases first catalyze the formation of the (E)-6-hexadecenoic acid or (Z)-11-hexadecenoic acid, key mono-unsaturated biosynthetic intermediates. Subsequently, each enzyme is able to produce the (E,Z)-6,11-hexadecadienoic acid by accommodating its non-respective mono-unsaturated product. Besides elucidating an unusually flexible pheromone biosynthetic pathway, our data provide the first identification of a biosynthetic Δ(6) desaturase involved in insect mate communication. The occurrence of this novel Δ(6) desaturase function is consistent with an evolutionary scenario involving neo-functionalization of an ancestral desaturase belonging to a gene lineage different from the Δ(11) desaturases commonly involved in moth pheromone biosynthesis.

Allelic variation in a fatty-acyl reductase gene causes divergence in moth sex pheromones

Pheromone-based behaviours are crucial in animals from insects to mammals, and reproductive isolation is often based on pheromone differences. However, the genetic mechanisms by which pheromone signals change during the evolution of new species are largely unknown. In the sexual communication system of moths (Insecta: Lepidoptera), females emit a species-specific pheromone blend that attracts males over long distances. The European corn borer, Ostrinia nubilalis, consists of two sex pheromone races, Z and E, that use different ratios of the cis and trans isomers of acetate pheromone components. This subtle difference leads to strong reproductive isolation in the field between the two races, which could represent a first step in speciation. Female sex pheromone production and male behavioural response are under the control of different major genes, but the identity of these genes is unknown. Here we show that allelic variation in a fatty-acyl reductase gene essential for pheromone biosynthesis accounts for the phenotypic variation in female pheromone production, leading to race-specific signals. Both the cis and trans isomers of the pheromone precursors are produced by both races, but the precursors are differentially reduced to yield opposite ratios in the final pheromone blend as a result of the substrate specificity of the enzymes encoded by the Z and E alleles. This is the first functional characterization of a gene contributing to intraspecific behavioural reproductive isolation in moths, highlighting the importance of evolutionary diversification in a lepidopteran-specific family of reductases. Accumulation of substitutions in the coding region of a single biosynthetic enzyme can produce pheromone differences resulting in reproductive isolation, with speciation as a potential end result.

Elucidation of the sex-pheromone biosynthesis producing 5,7-dodecadienes in Dendrolimus punctatus (Lepidoptera: Lasiocampidae) reveals Delta 11- and Delta 9-desaturases with unusual catalytic properties

Sex pheromones produced by female moths of the Lasiocampidae family include conjugated 5,7-dodecadiene components with various oxygenated terminal groups. Here we describe the molecular cloning, heterologous expression and functional characterization of desaturases associated with the biosynthesis of these unusual chemicals. By homology-based PCR screening we characterized five cDNAs from the female moth pheromone gland that were related to other moth desaturases, and investigated their role in the production of the (Z)-5-dodecenol and (Z5,E7)-dodecadienol, major pheromone constituents of the pine caterpillar moth, Dendrolimus punctatus. Functional expression of two desaturase cDNAs belonging to the Delta 11-subfamily, Dpu-Delta 11(1)-APSQ and Dpu-Delta 11(2)-LPAE, showed that they catalysed the formation of unsaturated fatty acyls (UFAs) that can be chain-shortened by beta-oxidation and subsequently reduced to the alcohol components. A first (Z)-11-desaturation step is performed by Dpu-Delta 11(2)-LPAE on stearic acid that leads to (Z)-11-octadecenoic acyl, which is subsequently chain shortened to the (Z)-5-dodecenoic acyl precursor. The Dpu-Delta 11(1)-APSQ desaturase had the unusual property of producing Delta 8 mono-UFA of various chain lengths, but not when transformed yeast were grown in presence of (Z)-9-hexadecenoic acyl, in which case the biosynthetic intermediate (Z9,E11)-hexadecadienoic UFA was produced. In addition to a typical Z9 activity, a third transcript, Dpu-Delta 9-KPSE produced E9 mono-UFAs of various chain lengths. When provided with the (Z)-7-tetradecenoic acyl, it formed the (Z7,E9)-tetradecadienoic UFA, another biosynthetic intermediate that can be chain-shortened to (Z5,E7)-dodecadienoic acyl. Both Dpu-Delta 11(1)-APSQ and Dpu-Delta 9-KPSE thus exhibited desaturase activities consistent with the biosynthesis of the dienoic precursor. The combined action of three desaturases in generating a dienoic sex-pheromone component emphasizes the diversity and complexity of chemical reactions that can be catalysed by pheromone biosynthetic fatty-acyl-CoA desaturases in moths.

Key biosynthetic gene subfamily recruited for pheromone production prior to the extensive radiation of Lepidoptera

Background

Moths have evolved highly successful mating systems, relying on species-specific mixtures of sex pheromone components for long-distance mate communication. Acyl-CoA desaturases are key enzymes in the biosynthesis of these compounds and to a large extent they account for the great diversity of pheromone structures in Lepidoptera. A novel desaturase gene subfamily that displays Δ11 catalytic activities has been highlighted to account for most of the unique pheromone signatures of the taxonomically advanced ditrysian species. To assess the mechanisms driving pheromone evolution, information is needed about the signalling machinery of primitive moths. The currant shoot borer, Lampronia capitella, is the sole reported primitive non-ditrysian moth known to use unsaturated fatty-acid derivatives as sex-pheromone. By combining biochemical and molecular approaches we elucidated the biosynthesis paths of its main pheromone component, the (Z,Z)-9,11-tetradecadien-1-ol and bring new insights into the time point of the recruitment of the key Δ11-desaturase gene subfamily in moth pheromone biosynthesis.

Results

The reconstructed evolutionary tree of desaturases evidenced two ditrysian-specific lineages (the Δ11 and Δ9 (18C>16C)) to have orthologs in the primitive moth L. capitella despite being absent in Diptera and other insect genomes. Four acyl-CoA desaturase cDNAs were isolated from the pheromone gland, three of which are related to Δ9-desaturases whereas the fourth cDNA clusters with Δ11-desaturases. We demonstrated that this transcript (Lca-KPVQ) exclusively accounts for both steps of desaturation involved in pheromone biosynthesis. This enzyme possesses a Z11-desaturase activity that allows transforming the palmitate precursor (C16:0) into (Z)-11-hexadecenoic acid and the (Z)-9-tetradecenoic acid into the conjugated intermediate (Z,Z)-9,11-tetradecadienoic acid.

Conclusion

The involvement of a single Z11-desaturase in pheromone biosynthesis of a non-ditrysian moth species, supports that the duplication event leading to the origin of the Lepidoptera-specific Δ11-desaturase gene subfamily took place before radiation of ditrysian moths and their divergence from other heteroneuran lineages. Our findings uncover that this novel class of enzymes affords complex combinations of unique unsaturated fatty acyl-moieties of variable chain-lengths, regio- and stereo-specificities since early in moth history and contributes a notable innovation in the early evolution of moth-pheromones.

Differential expression of cytochrome c oxidase subunit III gene in castes of the termite Reticulitermes santonensis

Social insects such as termites live in colonies in which cooperation is assumed by all individuals developing into castes to which specific tasks are allocated. Little has been reported about molecular aspects underlying termite caste-specific gene expression. Genetic regulation has recently been hypothesized to govern caste-specific traits and physiology in social insects. Cytochrome c oxidase (COX) has been shown to be an interesting candidate for expression study in insects. We used the cytochrome c oxidase subunit III gene (COXIII) that was cloned from mRNA in a lower termite, Reticulitermes santonensis De Feytaud (Isoptera; Rhinotermitidae). The full-length cDNA encodes a protein of 262 amino acids that shows high degree of homology with other insects COXIIIs. Reverse transcriptase-PCR and real-time PCR were performed to compare gene expression between larvae, workers, nymphs and soldiers. Analyses performed on head cDNAs revealed that COXIII is differentially expressed between castes. The level of COXIII is caste-regulated with an increase in workers (approximately 1.9-fold) and nymphs (approximately 2.8-fold) and a decrease in soldiers (0.8-fold) compared to the expression level in larvae (1.0-fold). These results may emphasize the physiological importance of COX in the termite brain at different developmental stages.