Olfactory Receptor Response to the Cockroach Sexual Attractant

Morphological and genetic differences in legs of a polygamous beetle between sexes, Glenea cantor (Coleopter: Cerambycidae: Lamiinae)

The legs of insects play an important role in their daily behaviour, especially reproduction. Entomologists have performed much research on the role of the leg in different behaviours of beetles, an important group in the insect family, but relatively little has been done to study the ultrastructure and transcriptome of their legs. Hence, we systematically studied the ultrastructure and gene expression of the leg of G. cantor, a polygynous beetle, and compared its male and female diversity. In this study, we found the fore-leg, mid-leg and hind-leg of the female were significantly longer than those of the male. From the perspective of intuitive structural differences, we also compared the ultrastructures of the adhesion structure (tarsal) of males and females. The tarsal functional structure of the adult leg mainly includes sensilla and an adhesion structure. The sensilla on the tarsal joint mainly include sensilla chaetica (SCh II, SCh III) and sensilla trichodea (ST II). The adhesion structure includes disc-shaped bristles (di), lanceolate bristles (la), serrated bristles (se), spatula-shaped bristles (spl) and mushroom-shaped bristles (mus). Although there was no significant difference in sensillum distribution or type between males and females, there were significant differences in the distribution and species of adhesion structures between the fore-leg, mid-leg, and hind-leg of the same sex and between males and females. Therefore, different adhesion structures play different roles in various behaviours of beetles. On the other hand, the transcriptome results of male and female legs were screened for a subset of olfaction- and mechanics-related genes. We discovered that the male leg showed upregulation of 1 odorant binding protein (OBP), 2 Olfactory receptors (ORs) and 2 Chemosensory proteins (CSPs). Meanwhile, the female leg showed upregulation of 3 OBPs, 1 OR, 1 Gustatory receptor (GR) and 3 Mechanosensitive proteins (MSPs). An in-depth examination of the ultrastructure and molecular composition of the legs can elucidate its function in the reproductive behavior of G. cantor. Moremore, this investigation will serve as a cornerstone for subsequent research into the underlying behavioral mechanisms.

Olfactory receptor responses of the nymphal American cockroach to sex pheromones and their mimics

1. EAG responses to highly purified sex pheromones (periplanone-A and -B), sex pheromone mimics [germacrene-D, (+)-verbanyl acetate and (+)-trans-verbenyl acetate] and general odor (camphor) were recorded from both sexes of adult and three nymphal stages (7, 10 and 11th instars) of the American cockroach. 2. The M/F ratios were evaluated for each stage by stimulation with the above chemicals. 3. The ratio values indicated undeveloped sex pheromone receptor on the antennae of 7th male instar and females of all the stages. On the other hand, precursory development of the receptor was expected on the antennae of males of the old-aged nymphal instars and full development on the adult male antennae.

The nature and development of sex attractant specificity in cockroaches of the genus Periplaneta. IV. electrophysiological study of attractant specificity and its determination by juvenile hormone

The antennae of male Periplaneta americana acquire a large number of olfactory receptors at the adult stage. Electrophysiological methods (single unit and electroantennogram recording) show that a portion of the receptors added at the adult ecdysis are sex attractant receptors. Sex attractant receptors are not present in large numbers on larval and adult female antennae. The differentiation of pheromone receptors is inhibited during normal larval development by juvenile hormone. Topical application of juvenile hormone-mimic to male antennae during the terminal larval instar inhibits their development. Comparative electrophysiological studies indicate a high degree of cross-reactivity of the P. americana sex attractant among four other species within the genus Periplaneta.

Dual role for potassium in Balanus photoreceptor: antagonist of calcium and suppression of light-induced current

1. The mechanism of reduction and final abolition of the depolarizing receptor potential of Balanus eburneus photoreceptors in K+-free saline was examined with electro-physiological techniques including voltage-clamp and ion specific electrodes. 2. An extended exposure to K+-free saline reduces the transient peak and the steady phases of the depolarizing receptor potential by approximately equal amounts. The process can be reversed in normal saline although the wave form of the response is often more rectangular upon recovery. Restoration of K+ induces a transient hyperpolarization of the resting membrane for several minutes. 3. The depolarizing receptor potential can also be restored in K+-free solution by reducing the Ca2+ concentration. This saline depolarizes the resting membrane, and the wave form of the depolarizing receptor potential assumes a rectangular configuration. 4. Voltage-clamp experiments revealed that an extended exposure to K+-free saline produced an extreme reduction of the inward light-induced current (LIC), but no detectable change in the membrane potential at which the current reverses sign. Membrane conductance in darkness showed little change. Reduction of the Ca2+ concentration from 20 to 0-2 mM in K+-free restored the current and produced a negative 8-10 mV shift in the zero current potential. There was also a significant decrease in membrane conductance in darkness. 5. Current-voltage relations of the membrane in K+-free, low Ca2+, or K+-free low Ca2+ salines were somewhat dependent upon the order the salines were presented. 6. Low Ca2+ saline (0-2 mM) by itself produced a -5 mV shift in the zero-current potential. Removing K+ in low Ca2+ produced an additional shift (-5 mV) in the zero-current potential.

Ionic effects on spindle adaptation

1. Effects of changes in ionic environment on the receptor potential were studied in isolated frog spindle. Particular attention was focused on the action of potassium removal on the early adaptive decline of the response.2. Removal of potassium caused a reduction and final disappearance of the dynamic overshoot of the receptor potential. The static phase of the response was also reduced although to less extent. The repolarization phase of the response following release of phasic or maintained stretch was greatly prolonged.3. Increased potassium concentration caused a reduction of the response, but did not change its general time course. The amount of reduction was related to the potassium concentration.4. Removal of sodium caused a marked diminution of the response, the static phase being in general more affected than the dynamic phase.5. It is suggested that the effects of potassium removal are caused by a delay in sodium inactivation and a partial depolarization of the endings. It is concluded that the greater part of the early adaptation of the spindle proper may be attributed to ionic mechanisms in the transducer membrane.

The contribution of mechanical factors to the early adaptation of the spindle response

1. Adaptation in terms of the early fall of the receptor potential was studied in isolated frog spindles. The contribution of gross mechanical changes to the decline of the response was determined by comparing the responses obtained under constant length and under constant tension.2. It was found that the early adaptation under constant stretch increased with increasing lengthening of the spindle for stretches up to 25-30% of the resting length and decreased with still stronger stretches. When the spindle was stretched by 100% or more the static phase of the receptor potential reached nearly the same height as the dynamic peak and the early adaptation approached zero.3. The early adaptation decreased with decreasing velocity of linearly rising stretch and approached zero for stretches below about 0.5 mm/sec.4. For different strengths of a steplike stretch the amount of early adaptation was linearly related to the fall in tension over the same period. The relative amount of tension fall, however, was always less than the corresponding fall of the response.5. The early adaptation was 15-20% smaller under constant tension than under constant length for stretches below the level giving the maximum dynamic peak.6. The results suggest that a comparatively small amount of the early adaptation of the spindle response to constant stretch is related to gross alterations in length in different regions of the spindle. The main part of the adaptive fall of the response is probably related to functional properties of the sensory membrane and to the ionic mechanism underlying the production of the receptor potential.

Antennal Receptors: Reactions to Female Sex Attractant in Periplaneta americana

In Periplaneta americana, olfactory receptors on the antennae of male adults and nymphs respond at low threshold to the specific natural odorous attractant produced by virgin females. There are no receptors for that odor on the antennae of female adults or nymphs of any instar.