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Article

Cuticular Hydrocarbon Profiling of Australian Gonipterini Weevils

School of Health, Medical and Applied Sciences, Central Queensland University, North Rockhampton, QLD 4701, Australia
Submission received: 23 March 2023 / Revised: 24 July 2023 / Accepted: 11 August 2023 / Published: 17 August 2023

Abstract

:
Cuticular hydrocarbon (CHC) profiling shows promise as a chemotaxonomic tool for identifying and discriminating between closely related insect species. However, there have been limited studies using CHC profiling to differentiate between weevil species (Coleoptera: Curculionidae). This proof-of-concept study investigated the use of CHC and volatile profiling to discriminate between five weevil species from three genera in the Gonipterini tribe. A total of 56 CHCs and 41 other volatile compounds were found across the five species, with 83 of the compounds being identified through their mass fragmentation patterns. The number of CHCs from each species ranged from 20 to 43, while the proportion of CHCs unique to each species varied between 0% and 19%. The most abundant CHCs were nonacosane, 7-methylheptacosane, heptacosane, and hexacosane. Principal component analysis of the centred log-ratio transformed data revealed broad differences in CHC profiles between the two Oxyops species, with Bryachus squamicollis demonstrating the greatest divergence from the other Gonipterini species. The results suggest that CHC analysis could be used to support established taxonomic methods, including morphological features and genetic sequencing results.

1. Introduction

Traditionally, insect taxonomy has been based on morphological features [1,2]. In the last few decades, genetic techniques such as DNA sequencing and barcoding have emerged as significant taxonomic tools [3,4]. Another complementary taxonomic technique is chemotaxonomy—the use of differences in biochemical composition between species to classify and/or identify them [5,6]. Originally used for the classification of plant species [7], the technique was subsequently extended to other organisms, such as insects. The major focus has been on cuticular hydrocarbons (CHCs) [8], which are found on the cuticles of virtually all insects, act to prevent desiccation, and serve as signalling molecules for communicating with other insects. CHCs are synthesised by the insect through a number of inter-linked anabolic pathways; hence, they are reflective of the genetic diversity and metabolic pathways of the species [9,10]. For several decades, CHC profiling has been used to classify various insect species [11,12]; however, it should be noted that this method is not without its drawbacks. These include high levels of intra-specific variation in some cases, environmental variation, and the challenges of defining CHC boundaries between species [11].
There have been a limited number of studies performed on the cuticular hydrocarbon profiles of weevils (Coleoptera: Curculionidae), despite the extensive diversity and ecological significance of this family. One early study by Baker and Nelson [13] investigated the cowpea weevil (Callosobruchus maculatus), finding that mono- and dimethyl branched-chain alkanes comprised the majority of CHCs in this species, with no difference in CHC profiles between sexes. Similarly, Lapointe et al. [14] investigated the Diaprepes root weevil (Diaprepes abbreviatus) and found no significant differences by sex or maturity stage. However, observations by Martins et al. [15] suggested that males of the rice water weevil (Oryzophagus oryzae) recognise females from their CHC profiles, indicating that some differentiation must be possible.
Finally, Souza et al. [16] recently demonstrated that the cuticular hydrocarbon profiles of several species of Gonipterus weevil agreed well with molecular sequencing data, suggesting that CHC profiling could be used for the accurate classification of species from this genus. These species are from the Gonipterini tribe, which encompasses the genera Bryachus (Pascoe 1870), Gonipterus (Schoenherr 1833), Iptergonus (Lea 1908), Oxyops (Schoenherr 1826), Pantoreites (Pascoe 1870), Prophaesia (Pascoe 1870), and Syarbis (Pascoe 1865). This tribe is native to the Australo-Pacific region, although some species (particularly Gonipterus spp.) have been accidentally translocated to various locations worldwide [17]. Both adults and larvae feed on Eucalyptus leaves. Outside of their native range, several species of Gonipterus have become significantly destructive pests of commercial Eucalyptus plantations [18] due to the absence of its natural parasitoids—principally, Anaphes nitens [19]. The Gonipterus genus in particular contains a number of cryptic species [17], which has posed significant barriers to the success of biocontrol programs [18]. Identification of such species typically requires molecular analysis and dissection of male genitalia [17].
If successful, rapid CHC profiling could provide an alternative to costly and time-consuming molecular sequencing and/or dissection techniques for the identification of morphologically cryptic species from this economically important tribe. Hence, this proof-of-concept study aimed to extend the CHC profiling method of Souza et al. [16] to discriminate between different Gonipterini genera, as well as between different species in specific genera (Gonipterus and Oxyops).

2. Materials and Methods

2.1. Specimen Collection

Fifteen weevils were hand collected from Eucalyptus populnea Muell. saplings in Central Queensland (23°46′ S, 150°21′ E) on 14 February 2021. They comprised five specimens of Oxyops fasciculatus Redtenbacher, three of an undescribed Oxyops sp. only known from this location (designated throughout this manuscript as Oxyops sp. 1), one specimen tentatively identified as Gonipterus sp. n. 2, three of Gonipterus cinnamomeus Pascoe, and three of Bryachus squamicollis Pascoe. Due to the limited number of Gonipterini weevils found during the fieldwork, a larger sample size was not possible for some species. Species delineations were confirmed by Dr Rolf Oberprieler (CSIRO, Canberra, Australia).

2.2. Extraction of CHCs

The CHC extraction methods followed those of Souza et al. [16]. After being killed in a freezer (−20 °C), each weevil was placed in a 2.0 mL GC-MS vial along with 300 μL of hexane. After 4 min, they were agitated for one minute by using a vortex mixer, and the hexane extract was collected. The weevil specimens were subsequently preserved in 100% ethanol.

2.3. Analysis of CHCs

The hexane extracts were analysed via gas chromatography-mass spectrometry (GC-MS) while following the methods of Souza et al. [16]. Analysis was performed on a single-quadrupole Shimadzu QP2010 Plus system (Shimadzu, Kyoto, Japan) fitted with an autoinjector/autosampler (AOC-20i/s) and Shimadzu SH-Rxi-5Sil MS column (29 m × 0.25 mm i.d. × 0.25 µm thickness). The following conditions were used: carrier gas—helium at 1.93 mL min−1, injection temperature—250 °C, injection volume—1 µL, split ratio 5:1, ion source temperature—230 °C, interface temperature—230 °C, MS mass range—35–600 m/z, and scan rate—3.3 scans/sec. During the run, the column temperature was initially held at 40 °C for 2 min before ramping linearly at 10 °C/min to reach 260 °C, where it was held for a further 6 min. The total run time was 30 min. Higher temperatures were not used in this study, as the main focus was on low- to moderate-weight CHCs, as studied by Souza et al. [16].
Chromatogram peaks were integrated if they had a peak area of >10,000 units and slope of >1000 units/min. Linear retention indices (LRIs) were calculated from the retention times of alkane standards (C8–C40) run under the same conditions [20]. Compound identities were established through the comparison of their mass spectra and LRIs with the NIST14 and NIST14s libraries and the relevant literature [14,21,22,23].

2.4. Chemometric Analysis

Data analysis of the volatile compound abundance was conducted in R Studio running R 4.0.5. [24]. Where applicable, the results are presented as the mean ± 1 standard deviation. The CHC dataset was transformed by using the centred log-ratio (clr) method prior to principal component analysis (PCA).

3. Results

3.1. Cuticular Hydrocarbon Profiles

Typical GC-MS chromatograms obtained for each species are provided in Figure 1, while Table 1 shows the compounds identified across all Gonipterini species. A total of 97 peaks were found across all species, with 59 compounds being able to be positively identified from their mass fragmentation patterns and LRIs. A further 24 compounds were tentatively identified, with 14 compounds (10 alkanes, 3 ketones, and 1 aldehyde) being unable to be precisely identified. Some of the compounds identified (e.g., eucalyptol and globulol) appeared to be derived from the host plants (E. populnea), rather than being synthesised by the weevils. However, the majority of the compounds (56) could be classified as CHCs (Table 1). While all compounds are discussed in this section, only the CHC data were used in the subsequent chemometric analysis.
A total of 56 of the volatile compounds had some pheromone-type activity in one or more insect species (Table 2), with 43 being documented as having pheromone-type activity in Coleoptera [22]. Several of the compounds (aromadendrene and exo-2-hydroxycineole) have been previously identified as attractants for Gonipterus platensis [25]. Eucalyptol (1,8-cineole) is reportedly used as a defensive agent by Oxyops vitiosa larvae [26], in addition to acting as a potential attractant in adults of this species [27]. A number of 1,8-cineole metabolites have also been identified as pheromones in Gonipterus platensis [28]. No previous work was found on attractants for Bryachus.
Table 2 details the concentrations of the non-CHC volatile compounds found in each of the five Gonipterini species, while Table 3 compares the CHC contents among the species. The most abundant CHCs across all five species were nonacosane and 7-methylheptacosane. B. squamicollis also contained high levels of heptacosane, while both Gonipterus species showed high levels of hexacosane. Oxyops sp. 1 notably contained quite high concentrations (8.28 ± 6.05%) of 2-methyloctacosane, as well as a lower 7-methylheptacosane concentration than that of any other species.
The most abundant compound class was methyl alkanes (with a total of 18 compounds present), followed by aldehydes (16), n-alkanes (10), ketones (8), and dimethyl alkanes (8) (Table 2). As shown in Table 4, the greatest number of total compounds were found in B. squamicollis (71), and the greatest number of unique compounds was found only in this species (20, comprising 28.2% of the total volatile compounds found in this species). Gonipterus sp. n. 2 contained the lowest number of compounds (35), in addition to possessing only two unique compounds (henicosanal and an unidentified ketone). A total of 23 compounds were identified as being present across all five species.

3.2. Chemometric Analysis

To investigate the natural groupings in the CHC data, an unsupervised exploratory analysis was conducted on the CHC data only. Prior to the analysis, the volatile data were subjected to a centred log-ratio (clr) transformation, as recommended by Brückner and Heethoff [29] for similar datasets.
The principal component analysis (PCA) revealed a broad separation between B. squamicollis and the remaining species across the first principal component (PC 1), which explained 18.7% of the variation in the CHC dataset. The remaining species were largely separated across PC 2, which explained a further 12.9% of the variation (Figure 2). Most species were well separated across the first two PCs, although the single specimen of Gonipterus sp. n. 2 was quite close to the Oxyops sp. 1 cluster.
Examination of the PCA loadings plot (Figure 3) was used to investigate the compounds that were most strongly associated with particular Gonipterini species. For example, nonacosane was strongly associated with Oxyops sp. 1, while the large number of compounds loaded in the same direction as B. squamicollis supported previous observations about the large number of unique compounds found in this species (Table 3).

4. Discussion

Souza et al. [16] previously reported the CHC profile of Gonipterus sp. n. 2, with the major compounds present including n-heptacosane, 2-methylhexacosane, n-hexacosane, n-pentacosane, and n-octacosane. Somewhat contrasting results were found in this study, with the major compounds from this species being identified as 7-methylheptacosane, nonacosane, octacosane, hexacosane, 3-methylheptacosane, triacontane, heptacosane, and pentacosane. However, it should be noted that only one specimen from this species was analysed, so the results here may not necessarily be representative of the species as a whole. Another potential reason may be the difference in geographic locations. The present study used a specimen from central Queensland, while Souza et al. [16] collected Gonipterini specimens from a much wider region across Australia (Qld, NSW, ACT, Vic, WA). Studies have shown that CHC profiles can vary significantly with geographic location [16,30,31]. Finally, the species is part of a cryptic complex [17], so there is the possibility of misidentification, as genetic analysis was not performed in this study.
The major CHCs from G. cinnamomeus were found to be 7-methylheptacosane, nonacosane, hexacosane, and triacontane in this study, quite similarly to Gonipterus sp. n. 2. The CHC profile of this species does not appear to have been previously reported.
Souza et al. [16] also studied the CHC profiles of ten Oxyops specimens (not identified to species), reporting the major constituents as n-heptacosane, n-pentacosane, two unidentified compounds, and n-nonacosane. This largely concurred with the predominant CHCs found from O. fasciculatus in this study: nonacosane, 7-methylheptacosane, hexacosane, pentacosane, and octacosane. The CHC profile of Oxyops sp. 1 was somewhat less similar to the general Oxyops profile reported by Souza et al. [16]. The major constituents included nonacosane, 7-methylheptacosane, and hexacosane; however, it was unique in having a particularly high concentration of 2-methyloctacosane (8.28%) and the lowest concentration of pentacosane (0.97%) out of all species studied. This species (Oxyops sp. 1) has not yet been formally described yet; hence, its status in the Oxyops genus remains to be confirmed by a thorough morphological investigation and genetic study.
The results of the PCA supported B. squamicollis as the outgroup taxon. Within the remaining species, the Oxyops and Gonipterus species were loosely clustered together, but with some overlap.
Although CHC composition is primarily regulated through genetic means [9], it can be impacted by a range of factors, including diet [32,33], population age structure [34,35], locality, and climate [36,37]. However, a number of studies have found that CHC profiles are reasonably stable among different locations and ecological factors [16,38,39]. Furthermore, any impact of most of these variables would be expected to be minimal in this study, given that all specimens were collected on the same day from the same vicinity and were all collected from the same host plant species (E. populnea).
The overall results of this work support the prospect of using CHC profiles as a (relatively) rapid method of discriminating between Gonipterini genera and species. Such an approach has previously been applied across a range of insect orders to date, although the bulk of studies have been performed on Hymenoptera or Diptera [40,41,42]. CHC profiling shows particular promise when combined with other taxonomic techniques, including DNA barcoding and morphological analysis [40,43,44]. Such rapid analytical tools for discriminating between Gonipterini species could find use in a variety of applications, including identifying large numbers of specimens from field surveys or supporting the description of new species alongside DNA barcoding or morphological studies.

5. Conclusions

This study presented the cuticular hydrocarbon profiles of several Gonipterini species for the first time, including Bryachus squamicollis, Gonipterus cinnamomeus, and Oxyops fasciculatus. Principal component analysis revealed broadly differing CHC profiles between most species investigated, with B. squamicollis demonstrating the greatest divergence from the other Gonipterini genera/species. The results suggest that CHC analysis could be used to support established taxonomic methods, including the use of morphological features and genetic sequencing results.

Funding

Funding for this research was supported by a 2022 Research Grant from the Australian Entomological Society.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The full datasets supporting the findings of this research are available from the corresponding author upon request.

Conflicts of Interest

The author declares no conflict of interest.

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Figure 1. GG-MS chromatogram of the hexane extracts from each Gonipterini species. The major peaks are marked; the compound numbers correspond to those provided in Table 1 and Table 2.
Figure 1. GG-MS chromatogram of the hexane extracts from each Gonipterini species. The major peaks are marked; the compound numbers correspond to those provided in Table 1 and Table 2.
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Figure 2. Score plot showing the results of the principal component analysis performed on the clr-transformed CHC data.
Figure 2. Score plot showing the results of the principal component analysis performed on the clr-transformed CHC data.
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Figure 3. PCA loadings plot showing the influence of individual CHCs on the principal component analysis performed on the clr-transformed CHC data.
Figure 3. PCA loadings plot showing the influence of individual CHCs on the principal component analysis performed on the clr-transformed CHC data.
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Table 1. Identification details for the compounds found in the Gonipterini hexane extracts. Compounds classified as CHCs are highlighted in bold.
Table 1. Identification details for the compounds found in the Gonipterini hexane extracts. Compounds classified as CHCs are highlighted in bold.
No.CompoundClassLRI
Rxi-5Sil
Lit. LRIM+ (m/z)Other Confirmatory MS Peaks (m/z)Ident. ^Roles # (Coleoptera)Roles # (Other Insects)
13-hexanoneKetone78778910043, 57, 71MS, LRI--
22-hexanoneKetone79179310043, 58, 85, 71MS, LRI--
32,4-dimethylheptaneDimethyl alkane82082212843, 85, 57, 71MS, LRI--
4HeptanalAldehyde90290211470, 44, 55, 57, 81, 86, 96MS, LRIA, AlA, Al, K, P
5OctanalAldehyde1002100112857, 56, 84, 69, 95, 100, 110MS, LRIA, AlA, Al, K, P
6EucalyptolMonoterpenoid1033103315481, 108, 139, 93MS, LRIA, Al, PA, K, P
73,6-dimethyldecaneDimethyl alkane1055108617057, 71, 85, 113, 127MS, LRI--
82,6,8-trimethyldecaneTrimethyl alkane1099110418485, 99, 127, 113, 155MS, LRI--
9NonanalAldehyde1104110814257, 70, 82, 98, 95, 96, 114MS, LRIA, Al, PA, Al, K, P
10DecanalAldehyde1205120415657, 70, 82, 95, 112, 128MS, LRIA, Al, K, PA, K, P
11Exo-2-hydroxycineole 12281228170108, 126, 93MS, LRI-P
122,6,10-trimethylundecane Trimethyl alkane1275127519857, 71, 85, 99, 127, 113, 155MS, LRI--
1310-undecenalAlkene aldehyde1282127716855, 67, 81, 97, 111, 135MS, LRI--
14Carvacrol Monoterpenoid1297129815081, 93, 135, 121MS, LRI-P
15Isoascaridole 1312130316895, 110, 81, 139MS, LRI--
164a-methyldecahydro-1-naphthalenol 1319136316895, 67, 97, 135, 121MS, LRI--
174,6-dimethyldodecaneDimethyl alkane1321132519885, 99, 113, 127, 155MS, LRI--
18cis-p-menth-1-en-3,8-diol 1358136217084, 71, 109, 138MS, LRI--
19(+)-cis,trans-nepetalactoneIridoid1364136516681, 95, 123, 109, 138MS, LRIAlA, Al
20DodecanalAldehyde1408140718457, 82, 96, 110, 140, 123MS, LRIAlK, P
21AromadendreneSesquiterpenoid14441440204161, 105, 133, 189MS, LRI-A
22Unidentified hydrocarbon 1-1488--57, 71, 85, 99, 113, 127, 141, 155, 169MS--
23BicyclogermacreneSesquiterpenoid15011494204121, 161, 136, 189MS, LRI-A, P
242,6,10-trimethyltridecane Trimethyl alkane1534154022699, 113, 127, 155, 141, 169MS, LRI--
25GlobulolSesquiterpenoid15921604222107, 109, 161, 189, 204MS, LRI-A
26TetradecanalAldehyde1612161121257, 82, 96, 124, 168MS, LRIAlA, Al, P
27Heptadecanen-alkane16991700240169, 183, 197MS, LRIA, Al, PA, Al, P
28PhytaneBranched alkane17431753282127, 155, 169, 197, 211MS, LRI--
29cis-9-hexadecenal Alkene aldehyde1795180023855, 69, 81, 93, 111, 121, 135, 149MS, LRI-A, P
30HexadecanalAldehyde1816181924057, 82, 96, 110, 124, 138, 165, 194, 222MS, LRIAl, PA, Al, P
316,10,14-trimethyl-2-pentadecanoneBranched ketone1840184226858, 71, 85, 95, 109, 124, 137, 165, 250MS, LRI--
322-heptadecanoneKetone1899188625458, 71, 96, 127, 166MS, LRI--
332,2-dimethyloctadecane Dimethyl alkane19101917282127, 155, 141, 169, 183, 197, 211, 239MS, LRI--
34HeptadecanalAldehyde19181920254138, 152, 166, 180, 194, 210, 226, 236MS, LRI-Al, P
353-ethyl-3-methylheptadecane Branched alkane19531956282127, 141, 155, 169, 183, 197, 223MS, LRI--
369-octadecanoneKetone1990198026871, 95, 141, 156, 169, 211, 254MS, LRI--
37cis-13-octadecenalAlkene aldehyde1995198526669, 81, 83, 95, 98, 111, 121, 135, 166, 248MS, LRI-A, P
38cis-9-octadecenal Alkene aldehyde2014200726655, 69, 96, 121MS, LRIPP
39OctadecanalAldehyde20192021268124, 138, 152, 166, 180, 194, 222, 250MS, LRIAl, PP
40cis-2-octadecen-1-ol acetateEster2074208631055, 69, 81, 97, 136MS, LRI--
412-nonadecanoneKetone2098210128258, 71, 85, 96, 100, 127, 138, 152, 267, 282MS, LRI--
42NonadecanalAldehyde2117210528282, 96, 109, 124, 138, 152, 166, 180MS, LRI-P
43Unidentified hydrocarbon 2-2128--211, 225, 239, 253, 267, 281, 295MS--
44Unidentified hydrocarbon 3-2139--127, 155, 183, 211, 239, 267MS--
45Unidentified hydrocarbon 4-2148--225, 238, 252, 267, 295MS--
46Unidentified hydrocarbon 5-2160--155, 169, 183, 253, 197MS--
47Unidentified hydrocarbon 6-2168--99, 127, 155, 183MS--
48Docosanen-alkane21972200310155, 169, 183, 196, 211, 239, 267MS, LRIPA, Al, P
49EicosanalAldehyde22222224296278, 250, 152, 124MS, LRIAlP
50Unidentified hydrocarbon 7 a-2260--127, 141, 155, 169, 183, 197, 211, 225, 239, 253, 267, 281MS--
51Tricosanen-alkane22972300324225, 239, 253, 267, 281, 295MS, LRIA, Al, PA, Al, K, P
52Unidentified ketone 1Ketone2304--58, 59, 71, 85, 96, 127MS--
53HenicosanalAldehyde2326232931082, 96, 110, 124, 209MS, LRI--
5411-methyltricosaneMethyl alkane2331233033899, 113, 127, 141, 155, 169, 196, 211, 239MS, LRI-P
55Unidentified aldehydeAldehyde2367--82, 97, 109, 125, 139, 180MS--
563-methyltricosaneMethyl alkane2374237533857, 71, 85, 96, 141, 183, 239MS, LRIPP
57Tetracosanen-alkane24002400338267, 281, 295, 309MS, LRIPA, Al, P
58DocosanalAldehyde2430243032482, 96, 152, 166, 250, 278, 306MS, LRIPP
599-methyltetracosane Methyl alkane2437243335299, 113, 127, 141, 155, 169, 183, 197MS, LRIPP
602-methyltetracosaneMethyl alkane24732465352309, 267, 281, 295, 337MS, LRIPP
61x-pentacosene Alkene24792477350168, 181, 197, 211, 225, 239, 253, 267MS, LRI--
62Pentacosanen-alkane24992500352267, 281, 295, 309, 323MS, LRIA, Al, PA, Al, K, P
63Unidentified ketone 2 bKetone2509--58, 59, 71, 85, 96, 239MS--
647-methylpentacosane Methyl alkane25222530362113, 127, 141, 155, 169, 183, 197, 224, 239, 253, 267, 281, 295, 309MS, LRIP-
6511-methylpentacosane Methyl alkane25302530366168, 169, 196, 224, 225MS, LRIPP
6613-methylpentacosane Methyl alkane25692530366127, 139, 141, 169, 183, 197, 225, 229, 254MS, LRIPP
673-methylpentacosaneMethyl alkane25742574366337, 336, 253, 267, 281, 309MS, LRIPAl, P
6811,15-dimethylpentacosane Dimethyl alkane25842550380168, 169, 239MS, LRIPP
69Hexacosanen-alkane26002600366281, 295, 309, 323, 337, 351MS, LRIPA, Al, P
70TetracosanalAldehyde26372632352334, 306, 278, 264, 250MS, LRIPP
712-methylhexacosaneMethyl alkane26632664380280, 337, 364, 365MS, LRIPP
72Unidentified hydrocarbon 8-2672--337, 211, 225, 253, 351MS--
7313-methylhexacosane Methyl alkane26822633380196, 197, 308, 309, 211, 280MS, LRIPP
74Unidentified hydrocarbon 9-2690--99, 97, 113, 127, 169, 225, 280MS--
75Heptacosanen-alkane27042700380323, 337, 351, 365MS, LRIPAl, P
767-methylheptacosane Methyl alkane2712273039499, 97, 113, 127, 141, 155, (224), 225, 309, 337MS, LRIP-
77Unidentified ketone 3Ketone2723--59, 58, 96, 111, 125, 137, 250MS--
7813-methylheptacosaneMethyl alkane27372733394168, 196, 197, 224, 253MS, LRIPP
79Unidentified hydrocarbon 10-2755--267, 295, 195, 197, 224MS--
8011-methylheptacosane Methyl alkane27592734394127, 141, 155, 168, 169, 239, 252, 253MS, LRIPP
812-methylheptacosaneMethyl alkane27642760394141, 183, 351MS, LRIPP
82Docosyl pentyl etherEther2770277539671, 83, 97, 111, 125, 139, 153, 167MS, LRI--
833-methylheptacosaneMethyl alkane27742773394365, 267, 281, 295, 309, 337MS, LRIPP
845,15- or 5,17-dimethylheptacosane Dimethyl alkane27772778408168, 127, 155, 211, 239MS, LRI--
855,11-dimethylheptacosane Dimethyl alkane2784278340899, 113, 127, 141, 155, 168, 169, 239MS, LRI-P
86Octacosanen-alkane28002800394337, 351, 365, 379MS, LRIA, PA, P
87SqualeneTriterpenoid2811279041069, 81, 95, 121, 136, 137, 149MS, LRIPA, P
8812-methyloctacosane Methyl alkane28302829408224, 210, 211, 182, 183, 197MS, LRIPP
89HexacosanalAldehyde2837283438057, 71, 82, 96, 111, 124, 180, 362MS, LRI-P
90x-methyloctacosane Methyl alkane28582864408365, 253, 281, 295MS, LRI--
912-methyloctacosaneMethyl alkane28652864408365, 253, 267, 281, 295, 309MS, LRIPP
92NonacoseneAlkene2881288840697, 83, 125, 167, 195MS, LRI--
931-hexacosanolFatty alcohol2890286538257, 97, 83, 69, 71, 111, 125, 153, 167, 181, 195, 209MS, LRI-P
94Nonacosanen-alkane29182900408337, 351, 365, 379, 393MS, LRIPA, Al, P
95Triacontanen-alkane29823000422168, 169, 224, 197MS, LRIPA, P
96x,12-dimethylnonacosane Dimethyl alkane30023000437112, 113, 169, 182, 183, 336, 337MS, LRI--
972-methyltriacontane Methyl alkane30393058437239, 224, 337, 365MS, LRIPP
^ Identification methods: LRI = linear retention index; MS = mass spectra, # identified roles from El-Sayed [22]: A = attractant; Al = allomone; K = kairomone; P = pheromone, tentative identification, a “Undetermined B” from Souza et al. [16], b may be “Undetermined G” from Souza et al. [16].
Table 2. Non-CHC volatile compounds identified in the Gonipterini hexane extracts by using GC-MS. Compounds were quantified as relative percentages of the total peak areas in the total ion chromatogram (TIC).
Table 2. Non-CHC volatile compounds identified in the Gonipterini hexane extracts by using GC-MS. Compounds were quantified as relative percentages of the total peak areas in the total ion chromatogram (TIC).
No.CompoundB. squamicollis
(n = 3)
G. cinnamomeus
(n = 3)
G. sp. n. 2
(n = 1)
O. fasciculatus
(n = 5)
Oxyops sp. 1
(n = 3)
p Value
13-hexanone0.03 ± 0.010.06 ± 0.010.080.05 ± 0.040.04 ± 0.00NS
22-hexanone0.02 ± 0.020.07 ± 0.010.070.06 ± 0.040.04 ± 0.01NS
4Heptanal0.03 ± 0.010.03 ± 0.02000*
5Octanal0.01 ± 0.010000NS
6Eucalyptol000.100.01 ± 0.020***
9Nonanal0.13 ± 0.050000***
10Decanal0.01 ± 0.010.02 ± 0.04000NS
11Exo-2-hydroxycineole0.04 ± 0.020.08 ± 0.0400.02 ± 0.020*
1310-undecenal0.14 ± 0.170000NS
14Tentative: carvacrol2.42 ± 3.830.04 ± 0.0700.02 ± 0.040NS
15Tentative: isoascaridole0.01 ± 0.010000NS
16Tentative: 4a-methyldecahydro-1-naphthalenol0.21 ± 0.230000NS
18Tentative: cis-p-menth-1-en-3,8-diol0.02 ± 0.030000NS
19(+)-cis,trans-nepetalactone0.02 ± 0.030000NS
20Dodecanal00.02 ± 0.0300.01 ± 0.010.01 ± 0.02NS
21Aromadendrene0000.01 ± 0.030NS
23Bicyclogermacrene0.03 ± 0.05000.02 ± 0.020NS
25Globulol000.070.01 ± 0.030NS
26Tetradecanal0.04 ± 0.0200.050.01 ± 0.020.02 ± 0.03NS
29cis-9-hexadecenal0.05 ± 0.010000***
30Hexadecanal0.17 ± 0.050.09 ± 0.040.100.16 ± 0.130.13 ± 0.08NS
316,10,14-trimethyl-2-pentadecanone00000.01 ± 0.02NS
322-heptadecanone0.09 ± 0.020.07 ± 0.030.140.04 ± 0.050.06 ± 0.02NS
369-octadecanone0000.1 ± 0.10NS
37cis-13-octadecenal0.12 ± 0.030000***
38Tentative: cis-9-octadecenal0000.03 ± 0.070NS
39Octadecanal0.61 ± 0.140.07 ± 0.040.130.19 ± 0.180.16 ± 0.13**
40cis-2-octadecen-1-ol acetate0000.01 ± 0.010NS
412-nonadecanone0.09 ± 0.020.04 ± 0.040.180.02 ± 0.050.08 ± 0.05NS
42Nonadecanal0.06 ± 0.010000***
49Eicosanal0.09 ± 0.0400.710.03 ± 0.070***
52Unidentified ketone 1000.0900***
53Henicosanal000.5000***
55Unidentified aldehyde0.02 ± 0.010000*
58Docosanal0.01 ± 0.010.58 ± 0.311.1200***
63Unidentified ketone 200.05 ± 0.090.1300NS
70Tetracosanal1.95 ± 2.564.22 ± 0.91000.16 ± 0.27**
77Unidentified ketone 300.75 ± 0.31000***
82Docosyl pentyl ether00000.27 ± 0.47NS
87Squalene0.38 ± 0.650.36 ± 0.370.710.43 ± 0.200.27 ± 0.08NS
89Hexacosanal0.94 ± 0.240.94 ± 0.3000***
NS = not significant (p > 0.05), * p < 0.05, ** p < 0.01, *** p < 0.001.
Table 3. Cuticular hydrocarbons (CHCs) identified in the Gonipterini hexane extracts by using GC-MS. Compounds were quantified as relative percentages of the total peak areas in the total ion chromatogram (TIC).
Table 3. Cuticular hydrocarbons (CHCs) identified in the Gonipterini hexane extracts by using GC-MS. Compounds were quantified as relative percentages of the total peak areas in the total ion chromatogram (TIC).
No.CompoundB. squamicollis
(n = 3)
G. cinnamomeus
(n = 3)
G. sp. n. 2
(n = 1)
O. fasciculatus
(n = 5)
Oxyops sp. 1
(n = 3)
p Value
32,4-dimethylheptane0.02 ± 0.010.02 ± 0.020.050.03 ± 0.020.02 ± 0.00NS
73,6-dimethyldecane0.03 ± 0.010.06 ± 0.020.060.05 ± 0.030.03 ± 0.01NS
82,6,8-trimethyldecane0.02 ± 0.020.02 ± 0.0300.01 ± 0.030.01 ± 0.01NS
12Tentative: 2,6,10-trimethylundecane0.03 ± 0.010.06 ± 0.010.050.06 ± 0.030.03 ± 0.00NS
174,6-dimethyldodecane0.03 ± 0.010.02 ± 0.0300.03 ± 0.030.01 ± 0.02NS
22Unidentified hydrocarbon 10.01 ± 0.010.01 ± 0.020.060.05 ± 0.020.03 ± 0.00NS
24Tentative: 2,6,10-trimethyltridecane0.01 ± 0.010.01 ± 0.02000NS
27Heptadecane0.03 ± 0.010.05 ± 0.010.050.04 ± 0.030.02 ± 0.02NS
28Phytane0.01 ± 0.020000NS
33Tentative: 2,2-dimethyloctadecane0.04 ± 0.020.06 ± 0.060.090.03 ± 0.030.02 ± 0.03NS
34Heptadecanal0.05 ± 0.010000***
35Tentative: 3-ethyl-3-methylheptadecane0.03 ± 0.020.06 ± 0.020.050.06 ± 0.030.03 ± 0.00NS
43Unidentified hydrocarbon 20.23 ± 0.210.25 ± 0.4300.03 ± 0.070.12 ± 0.22NS
44Unidentified hydrocarbon 300.35 ± 0.60000.23 ± 0.40NS
45Unidentified hydrocarbon 40.48 ± 0.460.42 ± 0.7300.06 ± 0.140.28 ± 0.48NS
46Unidentified hydrocarbon 50.10 ± 0.080.14 ± 0.240.070.04 ± 0.020.01 ± 0.02NS
47Unidentified hydrocarbon 60.08 ± 0.080.09 ± 0.15000.28 ± 0.49NS
48Docosane0.02 ± 0.02000.06 ± 0.050NS
50Unidentified hydrocarbon 700000.03 ± 0.03*
51Tricosane0.74 ± 0.190.37 ± 0.0901.35 ± 0.540.27 ± 0.06**
5411-methyltricosane0.20 ± 0.340000.02 ± 0.04NS
563-methyltricosane0.02 ± 0.030000NS
57Tetracosane0.03 ± 0.020.07 ± 0.010.160.09 ± 0.050.02 ± 0.02*
59Tentative: 9-methyltetracosane0.01 ± 0.020000NS
602-methyltetracosane00.94 ± 1.64000.69 ± 1.19NS
61Tentative: x-pentacosene0000.03 ± 0.070NS
62Pentacosane1.67 ± 0.931.83 ± 0.371.824.26 ± 2.020.97 ± 0.88NS
64Tentative: 7-methylpentacosane00.27 ± 0.4600.48 ± 0.420NS
65Tentative: 11-methylpentacosane00.15 ± 0.2600.11 ± 0.140NS
66Tentative: 13-methylpentacosane0.03 ± 0.050000NS
673-methylpentacosane0.26 ± 0.231.09 ± 0.640.2700**
68Tentative: 11,15-dimethylpentacosane0000.70 ± 1.570NS
69Hexacosane9.04 ± 6.8713.26 ± 7.614.708.30 ± 7.1011.01 ± 8.76NS
712-methylhexacosane0000.03 ± 0.070NS
72Unidentified hydrocarbon 800.51 ± 0.46000.15 ± 0.15NS
73Tentative: 13-methylhexacosane0.65 ± 1.120.02 ± 0.0400.88 ± 1.370NS
74Unidentified hydrocarbon 90.36 ± 0.620000NS
75Heptacosane11.32 ± 2.954.3 ± 4.942.271.54 ± 3.440.36 ± 0.62*
76Tentative: 7-methylheptacosane21.49 ± 5.3328.94 ± 7.2425.4527.58 ± 6.2916.77 ± 6.68NS
7813-methylheptacosane0.32 ± 0.060.07 ± 0.1300.08 ± 0.150.73 ± 0.24**
79Unidentified hydrocarbon 101.14 ± 1.2000.01 ± 0.020.10 ± 0.17NS
80Tentative: 11-methylheptacosane04.60 ± 4.1601.18 ± 2.490.14 ± 0.23NS
812-methylheptacosane00000.08 ± 0.07*
833-methylheptacosane03.14 ± 1.612.8200***
84Tentative: 5,15- or 5,17-dimethylheptacosane1.06 ± 1.070000NS
85Tentative: 5,11-dimethylheptacosane0.36 ± 0.621.93 ± 3.3503.93 ± 7.210.79 ± 1.37NS
86Octacosane6.89 ± 2.273.55 ± 0.8919.104.16 ± 0.854.43 ± 1.34***
88Tentative: 12-methyloctacosane0.22 ± 0.140.05 ± 0.08000*
90Tentative: x-methyloctacosane0.05 ± 0.0500.1100***
912-methyloctacosane0.24 ± 0.140.93 ± 0.220.9608.28 ± 6.05**
92Nonacosene1.03 ± 0.400000*
931-hexacosanol00.21 ± 0.20000***
94Nonacosane26.54 ± 5.0517.34 ± 3.0824.9042.99 ± 14.0951.41 ± 13.58*
95Triacontane5.72 ± 0.637.31 ± 3.072.790.51 ± 0.371.38 ± 0.68***
96Tentative: x,12-dimethylnonacosane0.30 ± 0.50000.01 ± 0.020NS
97Tentative: 2-methyltriacontane1.38 ± 0.430000***
NS = not significant (p > 0.05), * p < 0.05, ** p < 0.01, *** p < 0.001.
Table 4. Summary of the numbers of compounds identified in each Gonipterini species.
Table 4. Summary of the numbers of compounds identified in each Gonipterini species.
CategoryB. squamicollisG. cinnamomeusG. sp. n. 2O. fasciculatusOxyops sp. 1
Number of identified compounds7154355245
Number of unique compounds202274
Percentage of unique compounds28.2%3.7%5.7%13.5%8.9%
Number of identified CHCs4337203433
Number of unique CHCs81032
Percent of unique CHCs18.6%2.7%0%8.8%6.1%
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Johnson, J.B. Cuticular Hydrocarbon Profiling of Australian Gonipterini Weevils. AppliedChem 2023, 3, 414-427. https://0-doi-org.brum.beds.ac.uk/10.3390/appliedchem3030026

AMA Style

Johnson JB. Cuticular Hydrocarbon Profiling of Australian Gonipterini Weevils. AppliedChem. 2023; 3(3):414-427. https://0-doi-org.brum.beds.ac.uk/10.3390/appliedchem3030026

Chicago/Turabian Style

Johnson, Joel B. 2023. "Cuticular Hydrocarbon Profiling of Australian Gonipterini Weevils" AppliedChem 3, no. 3: 414-427. https://0-doi-org.brum.beds.ac.uk/10.3390/appliedchem3030026

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