Masayuki Sakuma

Aggregation arrestant pheromone of the German cockroach,Blattella germanica (L.) (Dictyoptera: Blattellidae): Isolation and structure elucidation of blattellastanoside-A and -B

The aggregation pheromone of the German cockroach,Blattella germanica, consists of attractant and arrestant, which can be detected by olfactometer and choice-chamber assay, respectively. Both were extracted from the frass-contaminated filter paper being used as a shelter. They were separated by solvent partition withn-butanol and water. The arrestant from then-butanol phase was purified by open column chromatography and then successive HPLC isolated two major arrestant components. Spectral evidence from SI-MS, HR-EI-MS, and NMR experiments with pulse techniques provided possible structures as 1-(6α-chloro-4β,5β-epoxy-5β-stigmast-3β-yl)-β-d-glucopyranoside and 1-(6α-chloro-5β-hydroxy-5β-stigmast-3β-yl)-β-d-glu-copyranoside, denoted as blattellastanoside-A and blattellastanoside-B, respectively. They represented arrestant activity as median effective doses (ED50) at 0.044 (A) and 3.2 (B) nmol on 1.0 cm2 of Whatman No. 1 filter paper.

A Glandular Gift in the German Cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae): The Courtship Feeding of a Female on Secretions from Male Tergal Glands

In the courtship behavior of the German cockroach, the male presents tergal glands to the female and feeds her with glandular secretions to place her in the appropriate precopulatory position. The phagostimulant activity of the secretions was quantitatively examined using the polyethylene glycol film method. The methanol extract of the glands on the eighth tergite induced a potent feeding response in 6-day-old virgin females (EC50= 0.0037 male equivalent/40 μg PEG spot). However, there was no temporal relation between the feeding response and the sexual receptivity of the females. Moreover, besides virgin females, the extract induced a feeding response in gravid or mated females, males, and the last-instar nymphs. These results strongly suggest that the secretions function as a dietary feeding stimulant in principle but as a courtship pheromone in the context of courtship behavior where the stimulants are offered as a nuptial gift.

Virtual reality experiments on a digital servosphere: guiding male silkworm moths to a virtual odour source

Abstract A digital ‘servosphere’ locomotion-compensation apparatus has been developed for use in experiments on the mechanisms of spatial orientation in ambulatory animals. The sphere is driven by a pair of digital AC-servo motors, which provide a negative feedback response to any displacements of the test animal. A high-speed video tracker continually reports the position of the animal to a computer, which controls the servo-motors via a motor-control board and also logs the position of the motor axes. Movements of the servos define the path of the test animal on a virtual plane. The computer also generates odour cues in real time via a relay-control board and an airflow system. Odour presentation is programmed to occur in response to the animals movements on the virtual plane, and can result in the animal being led to a virtual source. The servosphere was first used to investigate orientation of a walking male silkworm moth (Bombyx mori) towards a female in still air. When a calling female moth was placed beside the sphere, the male moth beat its wings and walked straight towards the female. Unilaterally dewinged males also walked in a straight line, though slightly to one side of the direction of the female, but bilaterally dewinged moths remained stationary. This indicates that in still air the male moths orientate to pheromone sources by fanning air from in front of them over their antennae with their wings. If a moth continually reverses its turning movements when it encounters a train of pheromone concentration peaks, it will maintain a course towards the source and eventually arrive there. This idea was demonstrated on the servosphere by incorporating a computer-controlled solenoid valve which releases pheromone when a moth points towards a virtual odour source. In this sensory field, both intact and bilaterally dewinged males reached the source irrespective of the wind direction. This result supports the proposed orientation mechanism and also demonstrates the applicability of the servosphere virtual-reality environment to the experimental investigation of insect orientation mechanisms.

Novel steroid glycosides as aggregation pheromone of the German cockroach

Abstract Novel steroid glycosides, blattellastanoside A ( 1 ) and blattellastanoside B ( 2 ) were isolated from the frass-contaminated paper used as a shelter. Both 1 and 2 were unique in that they contained a chlorine atom. Both exerted arrestant activity on the German cockroach, Blattella germanica (L.).

Phospholipid composition and pheromonal activity of nuptial secretion of the male German cockroach, Blattella germanica

As a part of the sequential courtship behavior of the German cockroach, Blattella germanica, females feed on the nuptial secretion from the male tergal glands. The pheromonal secretion, consisting mainly of oligosaccharides and phospholipids, strongly elicits a feeding response in virgin females. The phospholipids were composed of phosphatidylethanolamine and phosphatidylcholine. Their fatty acid compositions were determined by chromatographic and enzymatic methods. Although an authentic blend of phospholipids (1,2‐dioleoylphosphatidylethanolamine and 1,2‐dioleoylphosphatidylcholine) showed a marginal phagostimulant activity, addition of the blend to an authentic blend of oligosaccharides (maltose and maltotriose) strongly enhanced the activity to nearly the level of the crude extract. These results indicate that the nuptial feeding behavior is elicited by a synergistic action between phospholipids and oligosaccharides.

Oligosaccharide Composition and Pheromonal Activity of Male Tergal Gland Secretions of the German Cockroach, Blattella germanica (L.)

In the sequential courtship behavior of the German cockroach, Blattella germanica (Dictyoptera: Blattellidae), females feed on the tergal gland secretions from the male tergites. The phagostimulative components in the male secretions were composed of a complex mixture of oligosaccharides and phospholipids. Besides seven oligosaccharides previously identified, two new trisaccharides, O-α-D-glucopyranosyl-(1→6)-α-D-glucopyranosyl α-D-glucopyranoside and O-α-glucopyranosyl-(1→4)-O-α-glucopyranosyl- (1→1)-myo-inositol, were characterized as the sugar components of the secretions. The activity of the sugar components was compared in combination with the lipid fraction. Individual oligosaccharides exhibited the activity either alone or synergistically with the phospholipids. A complex mixture of these primary substances in the tergal gland secretions, thus, serves as a pheromonal phagostimulant in the precopulatory behavior, strongly eliciting feeding response in the female cockroach.

Nutritional phagostimulants function as male courtship pheromone in the German cockroach, Blattella germanica

Summary. Males of the German cockroach, Blattella germanica, secrete a pheromonal substance from the abdominal tergal glands, which elicits a feeding response in females during the sequential courtship behavior. The nuptial secretion consists predominantly of a synergistic mixture of sugars and phospholipids. Cholesterol and a series of amino acids, which are also components of the male’s glandular secretion, significantly enhanced the phagostimulant activity of the sugar components. The nuptial feeding behavior of the female cockroach is therefore elicited by a complex assortment of nutritive components in the male tergal secretion, including sugars, phospholipids, cholesterol, and amino acids. These results indicate that a mixture of primary metabolites, and not of specific secondary metabolites, serves as a pheromonal cue that appeals to the female’s gustatory sense and effectively brings her to the precopulatory position. Although the male secretion consists of nutrients, we suggest that these compounds probably do not represent a significant nutrient investment in females and their progeny but rather function as a signal in the mating sequence of B. germanica.

Synthesis of some analogues of blattellastanoside A, the steroidal aggregation pheromone of the German cockroach

Blattellastanoside A, the aggregation pheromone of the German cockroach, is a chlorinated steroid glucoside with the 5 beta-stigmastane skeleton. Its analogues were synthesized in order to clarify the structure-activity relationship. They are 1a with the 5 beta-cholestane skeleton, 1b with the 5 beta-androstane skeleton, 1c with a fluorine substituent instead of the chlorine and 1d with a beta-D-galactopyranose instead of the beta-D-glucopyranose of the original pheromone. Their bioassay shows that 1a and 1c are active, while 1b and 1d are totally devoid of pheromone activity. The aglycone of blattellastanosides A and B were active.

Adaptive Traits of Riptortus pedestris Nymphs (Heteroptera: Alydidae) for Locating Host Plants

ABSTRACT Riptortus pedestris (F.) (Heteroptera: Alydidae) females oviposit not only on host plants but also on nonhosts, which may impose high costs on nymphs in terms of locomotion energy and time searching for host plants. Therefore, we hypothesized that second-instar nymphs have developed adaptive traits that help them access host plants, because the first feeding stage occurs during the second instar in this bug. We compared responses to the aggregation pheromone, relative leg lengths, and locomotion performance using a servosphere locomotion compensator as tests of physiological, morphometric, and behavioral traits, respectively, among the instars. We also investigated the effects of delayed feeding in the second instar on subsequent survival and development. Our results indicated that second-instar nymphs might have responded more sensitively to synthetic aggregation pheromone than other instars. Morphological measurements showed that second-instar nymphs had the longest relative leg length compared with other instars. The experiment using the servosphere revealed that second-instar nymphs had higher locomotion performance than did older nymphs, which may allow second-instar nymphs to walk a distance comparable to older nymphs, although their body size is much smaller. However, we did find that more than a 48-h delay in feeding after the first-instar molt decreased subsequent survival rates and that a later first-feeding led to a longer developmental period during the second instar. We concluded that R. pedestris nymphs have evolved various adaptive traits to enhance the probability of accessing host plants in response to the costly oviposition habit of adult females that lay eggs on nonhosts.

Olfactory conditioning with single chemicals in the German Cockroach, Blattella germanica (Dictyoptera: Blattellidae)

Many insects find resources by means of the olfactory cues of general odors after learning. To evaluate behavioral responses to the odor of a particular chemical after learning with reward or punishment quantitatively, we developed a standardized odor-training method in the German cockroach, Blattella germanica (Linnaeus), an important urban pest species. A classical olfactory conditioning procedure for a preference test was modified to become applicable to a single odor, by which a (−)-menthol or vanillin odor was independently associated with sucrose (reward) or sodium chloride solution (punishment). The strength of the association with the odor was evaluated with the increase or decrease in visit frequencies to the odor source after olfactory conditioning. The frequency increased after (−)-menthol was presented with a reward, while it did not change with the rewarded vanillin odor. With both odors, the frequency decreased significantly after training with a punishment. These results indicate that cockroaches learn a single compound odor presented as a conditioned stimulus, although the association of the odor with a reward or punishment depends on the chemical. This olfactory conditioning method can not only facilitate the analysis of cockroach behavior elicited by a learned single chemical odor, but also quantify the potential attractiveness or repellency of the chemical after learning.