Corematal function in <Emphasis Type="Italic">Utetheisa ornatrix</Emphasis> (Lepidoptera: Arctiidae): Hydroxydanaidal is devoid of intrinsic defensive potency

Summary. Hydroxydanaidal, the pyrrolizidine alkaloid-derived male corematal pheromone active in the close-range precopulatory interactions of the moth Utetheisa ornatrix, appears not to contribute to the chemical defense of this moth. The compound failed to manifest feeding deterrency as an additive to mealworms, in assays with a lycosid spider (Lycosa ceratiola). Moreover, contact with the male’s coremata, such as appears to occur inevitably in consequence of courtship in Utetheisa, does not in itself reduce the palatability of the female moth.     

Birth sex ratios in sheep over nine lambing seasons: years 7–9 and the effects of ageing

The birth sex ratio of a commercial flock of Suffolk cross sheep, Ovis aries, was studied over nine consecutive lambing seasons. In all data from 2704 lambs were recorded and analysed. The overall (1985–1993) birth sex ratio was 49.96% male lambs. Ewes with single lambs produced significantly more males (53.04%) than ewes with triplets (45.54% male). A significant positive correlation was found between the flock age and the birth sex ratio (1985–1992). As the flock aged the birth sex ratio changed from female biased to male biased, remained male biased for a number of years, and then became female biased again. This pattern is evident first in single, then in twin and later in triplet births. Among like sex twins (males and females) (1985–1993) more males (53.88%) were born in the first half and more females (45.57% males) in the second half of the lambing season. The difference between the two halves is significant.     

Measurement of Odor-Plume Structure in a Wind Tunnel Using a Photoionization Detector and a Tracer Gas

The patterns of stimulus available to moths flying along pheromone plumes in a 3-m-long wind tunnel were characterized using a high frequency photoionization detector in conjunction with an inert tracer gas. Four contrasting flow regimes and source conditions were produced: odor released in pulses from a vertical and horizontal array of four sources, odor released continuously from a point source, and odor released continuously from a point source into an oscillatory wake. Although the four flow regimes produced plumes of intermittent and fluctuating concentration, there were considerable differences in the structure of the signal presented to the sensor. Pulses of tracer gas released at 10 Hz retained most of their longitudinal and lateral separation. The plume growing in the disturbed flow (`oscillatory'), was broader in its lateral extent than the plume growing in an undisturbed flow (`continuous'), and the concentrations in the former were lower at each downstream position. The signal recorded in the disturbed flow had higher intermittency, but the ratio between the peak concentration and the signal mean was lower than in the continuous plume. Time scales were typically longer in the tunnel than in a field setting, but length scales and the main features of intermittency and fluctuation were similar. Moths flying along plumes of pheromone in this and similar wind tunnels typically slow their velocity and narrow the lateral excursions of their flight track as they approach a pheromone source. Which features of the plumes measured in this study account for these behavioral reactions remains to be determined.     

Aggregation pheromone ofCarpophilus freemani (Coleoptera: Nitidulidae): A blend of conjugated triene and tetraene hydrocarbons

Summary Males ofCarpophilus freemani Dobson (Coleoptera: Nitidulidae) produce an aggregation pheromone to which both sexes fly in a wind-tunnel bioassay. The major pheromone component (ca. 30 ng per male per day in volatile collections) was identified as (2E,4E,6E)-5-ethyl-3-methyl-2,4,6-nonatriene. A minor component, (2E,4E,6E,8E)-7-ethyl-3,5-dimethyl-2,4,6,8-undecatetraene, was 3–10% as abundant as the major triene and was 5–20% as active when compared at relative doses ranging from natural proportions to 1:1. These compounds act synergistically: a mixture of major and minor components in natural proportions attracted more than twice as many beetles as the major component alone, and the mixture fully accounted for the activity of male-derived volatile collections. Six other male-derived conjugated hydrocarbons, ranging from 2% down to 0.04% as abundant as the major component, were also identified. These are (in order of decreasing bioassay activity when compared on an equal-weight basis): (3E,5E,7E)-6-ethyl-4-methyl-3,5,7-decatriene, (2E,4E,6E)-5-ethyl-3-me-thyl-2,4,6-octatriene, (3E,5E,7E,9E)-8-ethyl-4,6-dimethyl-3, 5,7,9-dodecatetraene, (2E,4E,6E,8E)-3,5,7-trimethyl-2,4,6, 8-undecatetraene, (3E,5E,7E)-5-ethyl-7-methyl-3,5,7-undecatriene, and (2E,4E,6E)-3,5-dimethyl-2,4,6-nonatriene. All structure identifications were confirmed by synthesis. In the wind tunnel, the pheromone acted synergistically with host-type volatiles such as propyl acetate, valeric acid, and ethanol. This concept was verified by fields tests in California, in which there was dramatic synergism between the pheromone and fermenting host materials. Pheromone biosynthesis is discussed.     

Effects of elevated yolk testosterone levels on survival, growth and immunity of male and female yellow-legged gull chicks

Androgen hormones of maternal origin contained in the eggs of avian species are considered to have positive effects on offspring characteristics and performance. However, negative consequences have also been reported, suggesting that mothers may experience a trade-off between beneficial and detrimental effects of egg androgens to offspring fitness. We studied the effects of elevated yolk testosterone (T) concentration on survival, development and phenotype of male and female yellow-legged gull (Larus michahellis) chicks by injecting egg yolks with physiological doses of the hormone. Elevated yolk T resulted in a male-biased post-hatching sex ratio, T-treated clutches producing a greater proportion of males compared to control ones at day 4 post-hatching, likely resulting from a reduction of female embryonic survival, whereas no effect of hormone treatment on hatching success or short-term chick survival was observed. In addition, T depressed post-hatching body mass in both sexes but had no effects on the intensity of the cell-mediated immune response or skeletal growth. No sex differences in egg characteristics or chick phenotype were detected. Time to hatching was not affected by T, but females originating from first laid eggs hatched earlier than males of the same laying order, independently of hormone treatment. However, the implications of sex differences in hatching times are unclear in the study species. Taken together, our results suggest that female yellow-legged gulls may be constrained in transferring androgens to their eggs by negative consequences on the viability of female offspring and growth of chicks of the two sexes.     

Health Impact Evaluation of Boron in Drinking Water: A Geographical Risk Assessment in Northern France

Objective: To evaluate health impact of boron in drinking water. Methods: A regional scale geographical study in Northern France was conducted. Assessment of boron blood levels in a group of 180 healthy individuals and correlation with boron content in drinking water were followed by an assessment of health indicators such as birth rates, mortality rates, and sex ratios in zones of different boron content in drinking water. Results: After necessary adjustments, men living in municipalities with more than 0.30 mg/L of boron in drinking water had elevated but not significant boron blood levels compared with those living in municipalities with boron water levels of less than 0.30 mg/L (159.1 versus 123.0 ng/g; p > 0.05). The standardized birth ratio adjusted for the reference geographic zone and calendar time period was 1.07 and 1.28 in the low and high (>0.3 mg/L) boron content municipalities, respectively. The birth rate in municipalities with high boron content in drinking water was higher than that of the reference geographic zone and of the French general population (p < 10^-4). The standardized mortality ratio adjusted for the reference geographic zone and calendar time period was 0.94 and 0.92 in the low and high boron content municipalities, respectively. The mortality rate in municipalities with high boron content in drinking water was less than that of the reference geographic zone and of the French general population (p < 10^-3). No statistical difference was noted in the male–female sex ratios between the different municipality zones (p = 0.45). Conclusions: The results of this study do not support the idea of a deleterious effect of boron on human health, at the boron water level contents found in this specific region. In fact, there is a tendency toward a beneficial effect with low-dose environmental exposure (less than 1 mg/L of boron) in drinking water.     

Adaptation of a four-arm olfactometer for behavioural bioassays of large beetles

Summary. We adapted a four-arm olfactometer (55 × 55 × 5.5 cm) for bioassays of large insects and its usefulness was evaluated by testing the responses of three beetles, the palm weevil Rhynchophorus palmarum (L.) (Coleoptera: Curculionidea) and two Dynast scarabs Strategus aloeus (L.) and Oryctes rhinoceros (L.) (Coleoptera: Scarabaeidae) to plant odours and aggregation pheromones. This olfactometer was coupled to a volatile delivery system dispensing highly volatile semiochemicals at constant concentrations. We materialized airflows in the olfactometer by discolouring sensitive papers with acid vapours under various conditions (air straighten by stainless steel grids in inputs and output, 500 ml/min per arm) to visualize air turbulence and to test air-tightness. The volatile delivery system can be used to mix and dispense a broad range of concentrations of semiochemicals in air from diluted aqueous solutions. It was calibrated by measuring the release of the pheromone using solid phase-microextraction (SPME). Dose-response curves to synthetic pheromone were obtained for O. rhinoceros of both sexes. Coupling the volatile delivery system to the fourarm olfactometer provided a system with which the responses of R. palmarum and S. aloeus to their synthetic aggregation pheromones and to natural plant volatiles could be readily observed and studied.     

Variations in the birth sex ratio and neonatal mortality in a natural herd of horses

Variations in birth sex ratios and sex differences in juvenile mortality occur in a number of mammalian species, and in many cases have been linked to resource availability. Most of these biases in offspring sex ratios concern polygynous species with pronounced sexual dimorphism, and where females only are philopatric. Data on species with unusual life-history strategies, such as slight sexual dimorphism or dispersal by both sexes, are of particular interest. In this study of a natural herd of horses (Equus caballus) which experienced an eruptive cycle, and therefore a period of nutritional stress, male offspring had higher neonatal mortality rates in nutritionally poor years than in good ones, whereas “year quality” had no effect on the mortality of female offspring; year quality could therefore be used by mares as predictor of sex-specific offspring survival. We show that the environmental conditions that predicted lower survival of males were negatively related to their production: the birth sex ratio the following year was female-biased; and mares were less likely to produce a son when they had produced a son the preceding year. There was no significant effect of mother's parity, age or rank, or the timing of conception or birth on offspring sex ratios. The mechanism leading to biases in the birth sex ratio could have been the loss of male embryos by mares that did not foal. As there was no evidence for selective abortion of male foetuses in females that did foal the next year, it is not necessary to invoke maternal adjustment, though this remains a possibility. Finally, there was a suggestion that male offspring were more costly to raise than females, since mothers that reared a son in poor years tended to experience an increase in the interbirth interval between their two subsequent offspring. Received: 28 December 1996 / Accepted after revision: 27 July 1997     

Insect chemical communication: Pheromones and exocrine glands of ants

Summary Chemical communication plays a very important role in the lives of many social insects. Several different types of pheromones (species-specific chemical messengers) of ants have been described, particularly those involved in recruitment, recognition, territorial and alarm behaviours. Properties of pheromones include activity in minute quantities (thus requiring sensitive methods for chemical analysis) and specificity (which can have chemotaxonomic uses). Ants produce pheromones in various exocrine glands, such as the Dufour, poison, pygidial and mandibular glands. A wide range of substances have been identified from these glands.