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Thomas Sanchez
Thomas Sanchez

Noctuid TOP

Adult: Most noctuid adults have drab wings, but some subfamilies, such as Acronictinae and Agaristinae, are very colorful, especially those from tropical regions (e.g. Baorisa hieroglyphica). They are characterized by a structure in the metathorax called the nodular sclerite or epaulette, which separates the tympanum and the conjunctiva in the tympanal organ. It functions to keep parasites (Acari) out of the tympanal cavity. Another characteristic in this group is trifine hindwing venation, by reduction or absence of the second medial vein (M2).[6]


Markings present on the wings of noctuid adults can be helpful in distinguishing species. From the basal location to the outer edge (proximal to distal) on the forewing, there is a claviform (club-shaped) stigma, horizontally oriented with the thicker end closer to the wing's outer edge, located posterior to a discal (round) stigma.[7] These are followed distally by a reniform (kidney-shaped) stigma,[8] which is typically oriented with its concave side facing the wing's outer edge. It is often not possible to discern all of the stigmata on all specimens or species.[7] Crossbands or crosslines may be present, oriented longitudinally from the leading to the trailing edge of the wing.[8]

Predation and cannibalism: During the larval stage, some cutworms readily feed on other insects. One such species is the shivering pinion (Lithophane querquera), whose larvae commonly feed on other lepidopteran larvae.[20] Moreover, many noctuid larvae, such as those of the fall armyworm (Spodoptera frugiperda) and of genera such as Heliothis and Helicoverpa, aggressively eat their siblings and often other species of caterpillar.[21]

Most noctuid moths produce pheromones that attract the opposite sex. Female pheromones that attract males occur widely and have long been studied, but the study of male pheromones has further to go.[22][23][24]

This group has a wide range of both chemical and physical defenses. Among the chemical defenses three types stand out. First, the pyrrolizidine alkaloid sequestration usually present in Arctiinae is also found in a few species of noctuids, including the Spanish moth (Xanthopastis timais).[26] Another chemical defense is formic acid production, which was thought to be present only in Notodontidae, but later was found in caterpillars of Trachosea champa.[27] Finally, the last type of chemical defense is regurgitation of plant compounds, often used by many insects, but the cabbage palm caterpillar (Litoprosopus futilis) produces a toxin called toluquinone that deters predators.[28]

Noctuid moths, like other nocturnally active flying insects, have exploitedan ecological niche that is free of the predators (such as sharp-eyed birds)that are active during daylight. Unfortunately for moths, nighttime activityexposes them to another one of nature's most successful predators -- echolocatingbats. Moth "ears," or tympanal organs, are located on the thoraxand are sensitive to the ultrasonic frequencies used by bats, and thereforeallow moths to hear the approaching bat. Since most noctuid moths do notuse sound for their social interactions and since their tympanal organsare often most sensitive to frequencies of the echolocating calls used bythe local bat population, it is thought that the auditory systems in mostnoctuid moths evolved as a direct result of bat predation (Fullard , 1987).

There is a great deal of work yet to be done on the auditory system ofnoctuid moths. For example, how do moths discriminate bat from non-bat stimuli?In some tropical regions, there is continuous, intense sound produced byother chorusing insects that often has spectral components in the ultrasonicrange. Since moths do not have an array of peripheral receptors (as vertebratesdo) to analyze the spectral characteristics of sound, what temporal characteristicsdo they use to filter out this noise? This is an important problem to manyauditory neurophysiologists since temporal cues are important to all animals(including humans) for sound pattern recognition. Another problem that mothsmust solve is localizing the direction in 3-D space of the hunting bat.How are the temporal and intensity cues from the two "ears" combinedto produce an image of the location of the bat in space? Again, this isa problem that all animals with two ears have to solve. Noctuid moths providean excellent model system to answer these questions since their peripheralauditory systems are extremely simple and remove the complication of spectralcues for sound pattern recognition. Furthermore, their auditory systemsmediate a well characterized, stereotyped behavior that is important totheir survival.

Outdoor pheromone traps (sexual trapping) permit detection of flights, and with good forewarning chemical methods of control can be deployed at the best moment. These traps are available for various noctuids (Mamestra oleracea, Chrysodeixes chalcites,...), but not for the Small Mottled Willow Moth.

Bacillus thuringiensis var. kurstaki may be used for biological control of many lepidoptera, including noctuids. The bacterium contains a pro-toxin of crystalline structure. Once the caterpillar ingests plant matter where the bacterium is present, the enzymes in its gut release the toxin. The bacterium is therefore only effective on the larvae, so it is important to pick the right moment to act. Some hours after ingestion, the caterpillar stops feeding, so damage is limited; the caterpillar then starves to death (by general metabolic disturbance and paralysis of mouth parts) in 2 to 5 days.

Nocturnal insects such as moths are ideal models to study the molecular bases of olfaction that they use, among examples, for the detection of mating partners and host plants. Knowing how an odour generates a neuronal signal in insect antennae is crucial for understanding the physiological bases of olfaction, and also could lead to the identification of original targets for the development of olfactory-based control strategies against herbivorous moth pests. Here, we describe an Expressed Sequence Tag (EST) project to characterize the antennal transcriptome of the noctuid pest model, Spodoptera littoralis, and to identify candidate genes involved in odour/pheromone detection.

In view of these difficulties in identifying ORs, we combined high-throughput sequencing and normalization of a cDNA library, prepared from the antennae of the cotton leafworm Spodoptera littoralis. This polyphagous noctuid species is one of the major pests of cotton, and much is known about its olfaction, thanks to previous behavioural and electrophysiological investigations: the sex pheromone, plant volatiles activating olfactory neurons, and various functional types of olfactory sensilla have been characterized [35]. S. littoralis thus appears particularly well-suited to establish the molecular bases of olfactory and pheromone reception in a crop pest from the noctuid family, which groups some of the most aggressive herbivorous pests.

Among the 9033 unigenes, 6738 presented a coding region (74.6%, mean length: 215.14 aa, median length: 221 aa, max length: 922 aa, min length: 30 aa, table 1). Protein sequences translated from the predicted open reading frame (ORF) set were compared to the non-redundant protein database (NR) and to the D. melanogaster and B. mori complete proteomes (e-value cut off: 1e-5) (Figure 1). Most of the sequences (90%) translated from predicted ORFs, showed similarity to known proteins. 678 ORFs presented no similarity at all. The 972 protein sequences having no similarity with the B. mori proteome were further compared to the B. mori genome using TBLASTX (e-value cut off: 1e-20), since the B. mori protein prediction available in SilkDB may have missed some genes. 713 remaining S. littoralis protein sequences had no similarity with any B. mori gene. 50 were classified in a gene ontology term and were analyzed using BLAST2GO (Additional file 3). Interestingly, we found enrichment in putative proteins involved in defense response to bacteria (FDR: 7,21E-004), antifungal humoral response (2,04E-006), xenobiotic metabolism processes (8,08E-006) and interaction between organisms (1,56E-007). An enrichment in defense-related objects was recently observed by Vogel et al [36] in the transcriptome of the noctuid Heliothis virescens pheromone glands, when compared to that of B. mori.

Unigenes were identified as encoding proteins putatively involved in modulation/regulatory process, such as hormone receptors (including ecdysone receptors EcR and USP), juvenile hormone-binding proteins, Takeout-like proteins and biogenic amine receptors (additional files 1 and 2). Consistent with the present data, we have previously characterized an octopamine/tyramine receptor expressed in the olfactory sensilla of an other noctuid, Mamestra brassicae[68]. Biogenic amines act as neurohormones, neuromodulators or neurotransmitters in most invertebrate species [69], and evidence has been accumulated over the last decades that such biogenic amines participate in the modulation of olfactory reception [70, 71]. Ecdysone and juvenile hormone are key hormones involved in the maturation [72] and the plasticity [73] of the olfactory system.

We built OBP and OR neighbor-joining trees based on Lepidoptera data sets. The OBP data set contained the 43 complete amino acid sequences deduced from the genome of B. mori, together with the largest OBP repertoires characterized within noctuid moths (7 sequences from H. virescens and 5 from Spodoptera exigua) and outside noctuid moths (13 from M. sexta and 4 from Plutella xylostella) (Accession numbers available in additional file 6). Signal peptide sequences were removed following predictions of cleavage site location made by SignalP 3.0. The OR data set contained 58 amino acid sequences from B. mori (6 sequences were removed from the alignment because of their short length) and the 21 sequences characterized from H. virescens, completed with subsets of sequences characterized within noctuids (3 sequences from Mythimna separata) and outside noctuids (4 from P. xylostella, 3 from Diaphania indica and 3 from E. postvittana). Amino acid sequences were aligned using ClustalW2 [87]. Unrooted trees were constructed by the neighbour-joining method, with Poisson correction of distances, as implemented in MEGA4 software [88]. Node support was assessed using a bootstrap procedure base on 1000 replicates, and nodes supported by a bootstrap value under 70% were collapsed to an horizontal line when drawing cladograms. 041b061a72


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