Olfactory responses of Epiphyas postvittana larvae to apple leaf extracts a new behavioural bioassay technique

Epiphyas postvittana (lightbrown apple moth LBAM) is a polyphagous pest of horticulture native to Australia and introduced into New Zealand New Caledonia the British Isles Hawaii and California Olfactory responses of LBAM have been well studied but this has mostly been confined to adult moths In this study olfactory responses of LBAM larvae to apple leaf extracts were measured using a new laboratory bioassay technique for choice tests Apple leaf extracts were prepared using four different extraction methods methanol soak near boiling water dip chloroform soak and 70 ethanol blended The choice of larvae between an apple leaf extract and solvent control was examined and the bioassays were videorecorded in timelapse mode with an infraredenabled camera LBAM larvae were significantly attracted to some of the apple leaf extracts The results indicate that the new bioassay method can be used as a reliable tool for evaluating the olfactory attraction of LBAM larvae and most likely also of many other species Based on these findings an attempt will be made to identify the active compounds present in the apple leaves that are responsible for the larval attraction

Chemical communication in horse-chestnut leafminer Cameraria ohridella Deschka & Dimić.

Females of the horse-chestnut leafminer Cameraria ohridella Deschka & Dimić (Lepidoptera: Gracillariidae) produce a highly attractive sex pheromone in the early photophase. The pheromone, luring conspecific males into Delta traps baited with females, is produced in the female abdominal tip (ca 10–50 pg per calling female) and the active components can be extracted with hexane. Both dissected tips and their hexane extracts show high attractiveness for C. ohridella males in a wind tunnel behavioural bioassay. According to electrophysiologic recordings the male antennae are notably sensitive to both dissected female abdomens and extracts from them. The strong attractiveness of the pheromone may be useful in control of this pest.

Chemical Communication and Behavioural Interaction Between Sexually Mature Male and Female Shore Crabs (Carcinus Maenas)

A new behavioural bioassay system has been used to examine chemical communication in the crab Carcinus maenas (Crustacea: Brachyura) and has demonstrated the sexually and temporally specific nature of a putative sex pheromone. Mature premoult and postmoult females evoked sexual behavioural responses from receptive male crabs. No response was obtained when intermoult female and premoult and postmoult male crabs were tested. Postmoult females continued to be chemically attractive to male crabs with a similar intensity to that of late premoult females for >8 d following moulting, and then with a reduced intensity for >14 d. Male C. maenas successfully entered copula with females >13 d after the female moult.

Partial characterisation of a spawning pheromone in the herring Clupea harengus pallasi

The production of a pheromone-like spawning substance by male herring is confirmed and biochemical properties of the substance are characterised. A behavioural bioassay is described in which 0.25–0.5 mL of test solution was added to 46 L of water containing a single male herring. The effect of the solution was judged by the degree of extension of the herring gonadal papilla and release of milt. Treatment with fresh milt, extracts of milt, or extracts of mature testes resulted in papilla extension, often with milt release; extracts of ovaries or immature testes were not effective. The milt and testicular extracts retained their bioactivity during purification, including removal of substances soluble in petroleum ether, elution from C-18 Sep-Pak cartridges, and elution from C-18 high-performance liquid chromatography (HPLC) columns. The bioactive substances do not appear to be proteins or peptides, because (i) bioactivity was retained in milt and testicular extracts after the large proteins were precipitated by acetone−HCl solution and discarded, and (ii) bioactivity was present after the remaining soluble peptides were degraded by incubation with pronase E, proteinase K, or protease type VI enzymes. The pheromone is also not a neutral lipid or nonpolar fatty acid, as bioactivity remained in the aqueous phase after extraction with petroleum ether. Rather, the proposed pheromone(s) eluted from Sep-Pak C-18 cartridges with 30% acetonitrile and subsequently from the reverse-phase HPLC column in fractions 33–48 with a gradient of acetonitrile. Several polar steroids, conjugated steroids, and prostaglandin F2α were also shown to elute in this region, whereas a variety of other less polar compounds eluted later. Finally, after the post-Sep-Pak material was extracted with dichloromethane, bioactivity was shown to be present to a lesser extent in the dichloromethane fraction (containing free steroids) and to a greater extent in the water phase (containing conjugated steroids). The bioactivity of the water phase was reduced by incubation with glucuronidase but was eliminated by a combination of glucuronidase and sulfatase treatment. Various synthetic free steroids, conjugated steroids, prostaglandins, and amino acids were tested in the bioassay, but none mimicked the effect of the crude or semipurified testicular and milt extracts. We conclude that at least one substance is active as a pheromone-like spawning substance in males. These substances show hydrophobic properties similar to those of polar steroids, prostaglandins, or their conjugated forms, and at least one form likely contains a sulfate or glucuronide group. The role of a male pheromone may be synchronisation of spawning in schools of herring.