Altered pairing behaviour and reproductive success in white ibises exposed to environmentally relevant concentrations of methylmercury

Methylmercury (MeHg) is the most biologically available and toxic form of mercury, and can act as a powerful teratogen, neurotoxin and endocrine disruptor in vertebrates. However, mechanisms of endocrine impairment and net effects on demography of biota are poorly understood. Here, we report that experimental exposure of an aquatic bird over 3 years to environmentally relevant dietary MeHg concentrations (0.05-0.3 ppm wet weight) resulted in dose-related increases in male-male pairing behaviour (to 55% of males), and decreases in egg productivity (to 30%). Dosed males showed decreased rates of key courtship behaviours, and were approached less by courting females in comparison to control males. Within dosed groups, homosexual males showed a similar reduction when compared with dosed heterosexual males. We found an average 35 per cent decrease in fledgling production in high-dose birds over the study duration. These results are of interest because (i) MeHg exposure is experimentally tied to demographically important reproductive deficits, (ii) these effects were found at low, chronic exposure levels commonly experienced by wildlife, and (iii) effects on reproductive behaviour and sexual preference mediated by endocrine disruption represent a novel and probably under-reported mechanism by which contaminants may influence wild populations of birds.     

Influence of ambient and thoracic temperatures upon sexual behaviour of the gypsy moth, Lymantria dispar

ABSTRACT. In an ambient temperature ( T _a) range of 18–28°C, thoracic temperatures ( T _th) of individual male Lymantria dispar (L.), caught at flight in the field, ranged from 21 to 36.5°C, with a correlation coefficient of 0.63 between T _th and ambient temperature ( T _a). Ambient temperature (and insolation) altered the insect's body temperature and the probabilities, latencies, and durations of preflight responses to pheromone. In a wind tunnel at 16 and 20°C, quiescent males exposed to pheromone raised their T _th by sustained wing fanning from 17 and 21°C, respectively, to c. 24°C before takeoff. At 24 and 28°C ambient, T _th rose by takeoff to 28 and 31°C, respectively. The latencies of male wing fanning in response to pheromone decreased from 1.44 min at 16°C ambient, to 0.58 min at 20°C, to 0.26 min at 24°C, and to 0.16min at 28°C. The components of behaviour (antennal twitch, body jerk, step and wing tremor) that occurred between quiescence and wing fanning were more frequent at ambients of 16 and 20°C than at 24 and 28°C.     

The chemical basis for sex recognition in Drosophila melanogaster

Chemical cues were recognized to play a predominant role in initiating male courtship behaviour in Drosophila melanogaster as measured by the number and duration of wing-vibration responses elicited in test males. The effect was associated with compounds specific to the female cuticle, for which we describe a simple extraction procedure. Female active extracts were compared with behaviourally non-active extracts from males, using gas-liquid and thin-layer chromatography. Using these preparative methods, long-chain hydrocarbons were isolated and activity was found only among unsaturated molecules. One, heptacosadiene, inducing the highest level of courtship, appears to be the main aphrodisiac pheromone of the female D. melanogaster. This compound is specific to females of the species and is the most abundant of their cuticular hydrocarbons.     

Male sexual behaviour and ethanol consumption from an evolutionary perspective: A comment on “Sexual Deprivation Increases Ethanol Intake in Drosophila”

Shohat-Ophir et al.¹ demonstrate a connection between sexual behaviour and ethanol consumption in male Drosophila flies, and how the neuropeptide F system regulates ethanol preference. Their results are rightly discussed only in a physiological context, but this has facilitated erroneous anthropomorphic interpretations by the media. Here we discuss the link between male sexual behaviour and ethanol consumption from an evolutionary perspective, providing a broader context to interpret their results.     

Are female guppies more likely to flee when approached by two males?

Female guppies Poecilia reticulata often flee when approached by a single courting male but observations show fleeing is more likely when two males approach simultaneously. This may represent a response to a greater cost of being courted by two males.     

Excess of counterclockwise scalp hair-whorl rotation in homosexual men

While most men prefer women as their sexual partners, some are bisexual and others are homosexuals. It has been debated for a long time whether a person’s sexual preference is innate, learned, or due to a combination of both causes. It was recently discovered that the human right-versus-left-hand use preference and the direction of scalp hair-whorl rotation develop from a common genetic mechanism. Such a mechanism controls functional specialization of brain hemispheres. Whether the same mechanism specifying mental makeup influences sexual preference was determined here by comparing hair-whorl rotation in groups enriched with homosexual men with that in males at large. Only a minority of 8.2% (n = 207) unselected ‘control’ group of males had counterclockwise rotation. In contrast, all three samples enriched with homosexual men exhibited highly significant (P< 0.0001), 3.6-fold excess (29.8%,n = 272) counterclockwise rotation. These results suggest that sexual preference may be influenced in a significant proportion of homosexual men by a biological/genetic factor that also controls direction of hair-whorl rotation.     

Pheromone-mediated behaviour of male lightbrown apple moth, Epiphyas postvittana, correlated with adaptation of pheromone receptors

ABSTRACT. Two pheromone components are required to elicit close-range precopulatory behaviour in male lightbrown apple moths, Epiphyas postvittana (Walker) (Lepidoptera). The receptor cells which respond to the major component (I) ( E )-11-tetradecen-1-yl acetate, have a fast disadaptation rate with recovery occurring within 5 s after stimulation, while the cells responding to the second component (II), ( E, E )-9, 11-tetradecadien-1-yl acetate, recover after approximately 300 s.
Studies on the behaviour of males in the laboratory show a close correlation between the duration of a memory effect, during which males will respond to compound I alone after receiving an initial exposure to I and II, and the time-course for disadaptation of component II-responding cells. These results suggest several possibilities for mechanisms of integration of sensory input by the CNS.     

The energetic cost of mating in a promiscuous cephalopod

Costs that individuals incur through mating can play an important role in understanding the evolution of life histories and senescence, particularly in promiscuous species. Copulation costs, ranging from energy expenditure to reduced longevity, are widely studied in insects but have received substantially less attention in other taxa. One cost of mating, the energetic cost, is poorly studied across all taxa despite its potential importance for the many species where copulation is physically demanding and/or frequent. Here, we investigated the energetic cost of mating in both male and female dumpling squid (Euprymna tasmanica). In this species, copulation can last up to 3 h and requires that the male physically restrains the female. We report that the act of copulation halves the swimming endurance of both sexes, and that they take up to 30 min to recover. Such a reduction in post-copulatory performance may have important implications for predator avoidance, foraging ability and energy allocation. Therefore, quantifying this cost is essential to understand the evolution of reproductive strategies and behaviours such as female receptivity and male and female mating frequency.     

Evolution and function of multimodal courtship displays

Courtship displays are behaviours aimed to facilitate attraction and mating with the opposite sex and are very common across the animal kingdom. Most courtship displays are multimodal, meaning that they are composed of concomitant signals occurring in different sensory modalities. Although courtship often strongly influences reproductive success, the question of why and how males use multimodal courtship to increase their fitness has not yet received much attention. Very little is known about the role of different components of male courtship and their relative importance for females. Indeed, most of the work on courtship displays have focused on effects on female choice, often neglecting other possible roles. Additionally, a number of scientists have recently stressed the importance of considering the complexity of a display and the interactions between its different components in order to grasp all the information contained in those multimodal signals. Unfortunately, these methods have not yet been extensively adapted in courtship studies. The aim of this study was to review what is currently known about the functional significance of courtship displays, particularly about the role of multimodality in the courtship communication context. Emphasis is placed on those cases where a complete picture of the communication system can only be assessed by taking complexity and interaction between different modalities into account.     

Inhibition of female mating by male accessory gland substances in the ground beetle Leptocarabus procerulus

The ground beetle Leptocarabus procerulus (Chaudoir) possesses seminal substances that have a physical function to form mating plugs and a physiological function to induce female refractory behaviour, which act together to hinder female remating. Little is known about the physiological properties of the substances inducing female refractory behaviour, especially with respect to their secretory organ, dose‐dependency, molecular characteristics and the effect of female maturity. By injecting male‐derived substances into females, substances that induce female refractory behaviour are shown to be produced in the male accessory gland but not in the testis. Injection of extracts from the accessory gland increases the female refractory period at moderate doses but not at lower or higher doses. By contrast, injection of extracts from the testis reduces the female refractory period at high doses. The lack of an effect of accessory gland substances at higher doses could be the result of an anomalous effect of unnaturally large doses of seminal products by direct injection, the toxicity of seminal substances that deter female responses, or counteraction by injected substances that promote female receptivity. The accessory gland substances lose their activity when heated, although the testis substances do not. Females without mature eggs tend to reject mating entirely, although variation in the number of mature eggs (one or more) is not associated with the female refractory period, indicating the limited effect of female reproductive maturity. These findings may help to clarify the physiological basis of the evolution of the elaborated male mating behaviour in L. procerulus.     

Nuptial flights and calling behaviour in the antLeptothomx acervomm (Fabr.)

Summary We describe in detail a very large nuptial flight of the antLeptothorax acervorum at an open hilltop site in Britain. The mating behaviour of these ants involved not only a large mating swarm but also sexual/calling behaviour by the females. The females left the flight to land on vertical objects, where they took up a characteristic calling posture, in which females of closely related species are known to release pheromones that are sexually attractive to males. ThatLeptothorax acervorum has a complex mating behaviour involving both large nuptial flights and sexual calling has important consequences for the interpretation of the evolution of polygyny in this species and social parasitism in its close relatives.     

Shoaling and mate choice of wild-type Tanichthys albonubes in the presence of the red fluorescent transgenic conspecifics

Shoaling and sexual behaviour of wild-type male and female white cloud mountain minnow Tanichthys albonubes were measured in the presence of the red fluorescent transgenic conspecifics under laboratory conditions. Wild-type female test fish showed no significant preference, whereas wild-type male test fish preferred to be near a shoal of red transgenic fish rather than wild-type fish. When placed in a potentially reproductive context, wild-type males had a higher competitive ability over transgenic males; wild-type females spent more time with wild-type males in visually mediated experiments, but wild-type males performed more courtship displays towards transgenic females. These results suggest that the red body colouration does not appear to disturb signal communication between wild-type and transgenic T. albonubes in shoaling behaviour; transgenic males have no mating advantage over wild-type males, but the red body colouration of transgenic females may affect mate choice of wild-type males.     

Microsatellite loci for behavioural studies of Eclectus parrot (Eclectus roratus: Aves)

Ten polymorphic microsatellite loci were isolated from the cooperatively breeding and sexually dichromatic Eclectus parrot (Eclectus roratus). Nine loci were in Hardy–Weinberg equilibrium and unlinked. One locus, Ero1, was presumed to be sex‐linked since females, the heterogametic sex, were all homozygous, whereas 72% of males were heterozygous. A DNA database search revealed that Ero8 is probably an independent isolation of the microsatellite locus AgGT83 of the parrot Amozona guildingii. With high heterozygosity (0.41–0.89) and number of alleles (two to 13), these loci should prove useful for investigating the mating system of these unusual Australasian parrots.     

Social stimulation as a circadian synchronizer in Periplaneta americana

Abstract

Social stimulation is not usually considered to be a circadian synchronizer of activity in insects. We investigated whether it could have any effect on synchronization and resetting capacity in insects with cauterized eyes. Direct continuous observations were carried out in groups of Periplaneta americana composed of two operated animals and eight controls. When night fell at the same time as before surgery, sexual and locomotor activity of operated animals remained synchronized with the activity of control animals. But when nightfall was postponed by 6 h, operated animals were unable to lengthen the activity peak, as long as the activity threshold stayed at its minimum level. Social stimulation resulted in modifications of and interactions with the temporal activity distribution within the threshold limits, but was unable to reset the circadian clock; so it may be questioned whether it should be regarded as a circadian synchronizer in a strict sense. Circadian rhythm of food intake disappeared in operated animals; this unstable character which has already been mentioned by other authors, even in intact animals, is discussed.