Contact cues

The external cuticle of insects is covered by a waxy layer composed of mixtures of hydro-phobic lipids that include long-chain alkanes, alkenes, wax esters, fatty acids, alcohols, aldehydes, and sterols. The primary purpose of this layer is to maintain water balance and prevent desiccation, as described in Chapter 6, but many of the cuticular lipid components have important secondary roles as intraspecific contact chemical signals (pheromones). These roles include species and sex recognition during reproductive interactions, and nestmate recognition and other colony organization functions in social insects. Thus, these compounds are essential mediators of insect behaviors. Cuticular compounds are also exploited by parasitoids and predators as interspecific contact cues (kairomones) to aid in host location. 

MATTIACCI, L., DICKE, M., The parasitoid Cotesia glomerata (Hymenoptera Braconidae) discriminates between first and fifth larval instars of its host Pier is brassicae, on the basis of contact cues from frass, silk, and herbivore-damaged leaf tissue., J. Insect Behav., 1995, 8, 485-498. 

Leaf surface compounds provide important information about host-plant acceptability to coleopteran insects. Although the tortoise beetle, Cassida canaliculata, is only weakly attracted to odors from host plants, it shows strong preferences for host plants when additional contact cues are provided.64 The cottonwood leaf beetle, Chrysomela scripta, which is a pest of cottonwood, poplar, and willow, is stimulated to feed by leaf surface chemicals produced by a beetle-preferred poplar clone 65 The feeding stimulants have been isolated and identified as 1-docosanol, 1-tetracosanol, 1-hexacosanol, 1-octacosanol, 1-triacontanol, and... 

In this paper we have only discussed chemical contact cues used by insects to identify ovipositional sites. In nature, olfactory, mechanical, and visual stimuli may also be important in the location, recognition, and acceptance of host plants. Much work remains to be done in this area. We believe that multidisciplinary teams are needed to work toward a more complete understanding of insect-plant interactions. With the knowledge obtained, plants can be more readily designed to naturally resist insect damage. 

Ultra-sound emissions typically occur when male rodents are exposed to female odours or altricial neonates to maternal sources (Whitney, 1974 Conely and Bell, 1978). Without the VNO, sexually inexperienced male mice do not utter emissions at ultra-high frequencies (UHF), whereas those with prior experience vocalise after VN-x, as discussed above (Chap. 5). Female mouse urine contains a unique UHF-eliciting component which is non-volatile but ephemeral (Sipos et al., 1995). The signal is degraded by oxidation and disappears within 15 to 18 hours of deposition. Direct contact with freshly voided urine must occur before males will vocalise (sexually experienced or inexperienced). At least one of the olfactory systems is needed for UHF to be elicited by fresh urine complete deafferentation abolishes the response (Sipos et al., 1993). Exposure to females permits UHF to be elicited by other than chemical cues (Labov and Wysocki, 1989). Nocturnal or cryptic species conceivably use ultrasound to advertise male presence whether this is to deter other males or assist with female location is unclear. 

Experimental data suggest that VN stimuli might also play a relevant role in prey-predator interactions by mediating affective responses to prey or predator chemical cues. For instance, one of the preferred prey for the snake Thamnophis sirtalis is earthworms. Halpern (1988) demonstrated that earthworm wash constitutes a VN stimulus that is rewarding for these snakes. On the other hand, it has been shown that rats display defensive reactions to a collar that has been worn by a cat, even if they have no previous experience with cats. For these defensive behavioral responses to occur, direct contact with the collar is needed (Dielenberg and McGregor 2001). 

A prey animal s response to a predator cue may be influenced by a variety of factors. Familiarity with a predator may be important if the two species have a long evolutionary history of contact and it might be supposed that a cue would be more recognizable than if the species have only recently come into contact, or are allopatric (Catarell and Chanel 1979 Dickman 1992 Muller-Schwarze 1972 Sullivan, Nordstrom and Sullivan 1985). The age of an animal may also influence its response, or responses may alter seasonally (Borowski 1998,2002). 

Figure 12.4A shows the interaction of the first CUE domain of Cue2 interacting with ubiquitin, which might serve as a general model for the interaction mode of other UBA-like domains. The CUE domain binds to the Ile-44 patch of ubiquitin, in accordance with the chemical shift perturbation results of the UBA ubiquitin interaction [52], On the side of the CUE domain, residues of the first and third helix participate in this interaction surface. These residues include the Phe-Pro and Leu-Leu motifs, which had been predicted to be important for ubiquitin binding, based on comparative sequence analysis of CUE-A and CUE-B domains [62]. Positions in close contact with ubiquitin are also indicated in the alignment of Figure 12.3. The two available structures of the CUE ubiquitin complexes offer little expla-...

Stimuli other than chemical cues can play an important role in puberty delay in females. In the California mouse, Peromyscus californicus, which is monogamous, physical contact with the mother, and not a urinary chemosignal per se, is necessary for delay of puberty of females (Gubernick and Nordby, 1992). 

Estradiol subsequently builds up in the blood and first (within 2 to 12 hours) reduces the levels of follicle-stimulating hormone (FSH) and the amplitude of LH pulses, then (within 12 to 48 hours) causes preovulatory surges of LH and FSH. The former promotes ovulation and development of a corpus luteum (reviewed in Martin et ah, 1986). Two compounds have been indicated in the effect of the odor of ram s fleece on LH secretion in anestrous ewes. These are 1,2-hexadecanediol and 1,2-octadecanediol. In Merino sheep at least, maximum stimulation of ovulation requires full exposure to a ram, such as fenceline contact in pastures. Olfactory cues from the ram s wool, presented in a facemask for the ewe, are ineffective by themselves visual and tactile stimuli are also important. The Merino breed does not rely as much on olfactory cues as other breeds of sheep (Pearce and Oldham, 1988). The effect is not necessarily species specific hair extract from male goats stimulates LH release in ewes. For this effect, the accessory olfactory system is not necessary (Signoret etah, 1989). 

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