Sexual Dichromatism and Temporary Color Changes in the Reproduction of Fishes

SYNOPSIS. Studies on color patterns of fishes have focused onrelationships between bright, relatively permanent colors, suchas those of fishes inhabiting coral reef and tropical freshwaterhabitats, and ecological factors, such as competitors, predators,and the visual background. By comparison, the functions of,and hence the selective pressures acting on, temporary changesin nuptial coloration have received much less attention. Temporarycolor changes associated with reproduction occur in many freshwaterand marine groups. Nuptial coloration in fishes functions bothin agonistic interactions among males and courtship of females,so that it is subject to both intrasexual and intersexual selectionas well as natural selection. Temporal variation in nuptialcolor patterns is sensitive to temporal changes in the male'sphysical condition, motivation, and social status. Physiologicalprocesses, such as neuronal and endocrine changes, play importantroles in the expression of breeding colors, including rapidresponses to changes in social conditions. The importance ofproximal mechanisms and ultimate selective processes in mediatingrapid changes in the blue, melanin—based breeding colorsof pupfish, and the red, carotenoid—based color patternsin guppies are discussed in the context of signal function andevolution.     

The Role of Wing Pigmentation, UV and Fluorescence as Signals in a Neotropical Damselfly

Pigmentation patterns, ultraviolet reflection and fluorescent emission are often involved in mate recognition and mate quality functions in many animal taxa. We investigated the role of wing ultra-violet reflection, fluorescence emission, and pigmentation on age and sexual signals in the damselfly Mnesarete pudica. In this species, wings are sexually dimorphic in colour and exhibit age dependency: males and females show a smoky black colouration when young, turning red in mature males while it turns brown in females. First, we investigated wing UV patterns through reflectance and emission spectra. Second, behavioural experiments were undertaken to show male and female responses to manipulated wing pigmentation and experimentally reduced UV (UV-). Reflectance spectra of the wings of juvenile and mature males and females were used to show the differences between controls and individuals with manipulated colouration used in the behavioural experiment. UV-reduced, females with wings painted red, and control males and females were tethered and presented to conspecific males and females, and their behavioral responses were recorded. The male red wing pigmentation and females with red wings elicited an aggressive response in territorial males and a sexual response in females. Both males and females showed neutral responses towards individuals with reduced UV. Wing signals of juvenile individuals also provoked neutral responses. These results suggest that UV, together with pigmentation, plays a role during mate recognition in males and females. Other than butterflies and spiders, it seems that fluorescence signals and UV reflectance can also be part of communication in odonates.     

Forced Copulations and Female Contact Guarding at a High Male Density in a Calopterygid Damselfly

Territorial males of Calopteryx damselflies court females on territories that contain oviposition substrates. Nonterritorial males try to mate without courtship but very rarely obtain matings because females fail to bring up their abdomen to engage genitalia. Here I report the results of observations made on a very high-density population of Calopteryx haemorrhoidalis in central Italy. Mating activity was intense, and during 40 h of observation in an 8-m section of the stream, 209 matings were recorded (a maximum of 17 matings h ^–1 ). Males were continuously disturbing ovipositing females and tried to achieve tandem forcibly. Of 84 cases, males achieved forced tandem in 53, and 49 ended with copulation. Forced tandems were the most common method to obtain a mating in this population (55% of 65 matings). Males guarded females after forced or courtship copulations and, in some cases, maintained physical contact with their mate, by perching on her wings. Confusion was common and males guarded nonmates frequently, which suggests that they were unable to recognize their mate individually.     

The Pattern of Distribution of Defects of Wing Venation in the Banded Agrion (Calopteryx splendens)

The distribution of morphological structures was studied in wings of the banded agrion (Calopteryx splendens Harr.) from different intrapopulation groups. Dragon flies of odd years of emergence are characterized by a more stable pattern of ontogenetic processes according to the mean total number of venation defects. The sharply increased level of radiation in summer 1986, which coincided with the flight of dragon-flies, could have caused hereditary defects expressed in a sequence of generations of even years of emergence. Apparently, most alternative features of wing venation in dragon-flies can be considered as markers of stability of the ontogenetic processes, which reflect, to a great extent, genotypic features of the organisms in a population. A possible mechanism has been described, which explains the proposed topological model of formation of the venation defects of different types. The increase in mean frequencies of defects can suggest an enhanced development over the aberrant epigenetic trajectories, which may lead to the elimination of these organisms under the influence of various agents, i.e., to the stabilizing selection in a population. The results obtained suggest that defects of venation arise on the stochastic basis and their frequency increases upon destabilization of ontogenetic processes not only by the environmental factors, but also by genetic stress. Venation defects can be successfully used in population biomonitoring.     

On Sexual Apathy in the Male

Ever since World War II, there has been a noticeable change in the sexual behavior and responses in men and women. Women, in general, are becoming sexually more assertive and demanding and men more indifferent and lethargic. In patients of middle age, sexual boredom is particularly pronounced in men, whereas the post-menopausal female becomes more interested in sexual pleasure.In the youth of the “cool” generation, both boys and girls are quite open about sex, but their sexual activities precede emotional involvement. The similarities in dress and behavior of both sexes indicate a wish for a twin rather than a search for a lover. In the age group between 25 and 45, women demand equal orgasms since they have become economically independent and are relatively free of the fear of pregnancy. This seems to have mobilized a deep-seated unconscious fear and hatred of women in the male, making him sexually apathetic. In both sexes there is a growing alienation between romantic love and sex.     

No Correlation Between Ectoparasitism and Male Mating Success in a Damselfly: Why Parasite Behavior Matters

The mating success of individually marked male damselflies parasitized by water mites was closely followed. The number of ectoparasites could be determined exactly from knowledge of the parasite's life cycle. In contrast to previous studies, no correlation between water mite infestation and male mating success was revealed. The reasons for this discrepancy may be explained by the inclusion of the parasite's behavior. The body fat content of the males was negatively correlated with the mite load, indicating that parasitism reduces host's condition. It is hypothesised that the water mites damselfly system is not valuable for testing the Hamilton and Zuk hypothesis. Furthermore, selection exerted or mediated by parasites should act during the teneral phase.     

Sexual Signals of the Male American Goldfinch

Male American goldfinches (Carduelis tristis) exhibit conspicuous yellow plumage, orange bills, and black caps during the breeding season. These secondary sexual characteristics may serve as criteria by which females evaluate males as potential mates because the traits vary among individuals and are likely to be costly. We quantified plumage and bill color and cap characteristics of wild, free‐ranging American goldfinches during the breeding season and tested for relationships between those features, body condition and individual genetic diversity in males. Overall, male and female goldfinches were highly sexually dichromatic, with plumage saturation and brightness and bill brightness contributing strongly to the dimorphism. Body condition decreased significantly with Julian date, even over the 2‐wk period immediately prior to the onset of nesting during which we collected our color and cap measurements. Principal components describing color of the back and the bill significantly predicted date‐corrected body condition based on quadratic regressions, suggesting that there is reliable information in back and bill color that females could use when choosing mates. In a subset of captive males, we found that bill hue faded from orange to yellow within 24 h of capture, suggesting that bill color may reflect short‐term changes in health status or carotenoid availability. Individual genetic diversity based on a panel of eight microsatellite loci was correlated with back brightness and perhaps with cap symmetry. Based on the results of this field study, ornamentation of male American goldfinches appears to signal both long‐ and short‐term aspects of phenotypic quality.     

鲁中山区东亚三角头涡虫有性生殖过程研究初报

于2005年3-5月、9～11月对生活于鲁中山区的东亚三角头涡虫（Dugesia japonica）的有性生殖过程进行了研究,发现鲁中山区东亚三角头涡虫1年只有1次有性生殖过程。卵囊产出的高峰在4月,卵囊孵化与种群密度最高峰在5月,其有性生殖过程与温度、食物、虫体大小密切相关。经实验观察1个卵囊最多能孵出涡虫幼体10条,最少3条。     

Regulation of Male Sexual Behavior by Progesterone Receptor, Sexual Experience, and Androgen

Recent studies have demonstrated that physiological doses of progesterone may facilitate the androgen-dependent display of male sexual behavior in laboratory rats and three species of lizard. We used mice with a targeted disruption of the progesterone receptor to investigate whether such interactions exist in male mice and whether they may be modified by sexual experience. We found that naive intact male progesterone receptor knockout (PRKO) mice exhibit reduced mount frequencies compared to wild-type (WT) mice. Also unlike WT mice, sexually experienced PRKO males show profound losses in many measures of sexual behavior following castration. In a second experiment, we tested whether male mice heterozygous for a null mutation at the progesterone receptor locus were responsive to testosterone and progesterone treatment. We found that heterozygous males showed a reduced response to testosterone. The data are consistent with experiments indicating that the progesterone receptor is able to facilitate male-typical sex behaviors in other species and suggest novel mechanisms underlying the interaction of androgens and experience.     

Sexual difference in color sense in a lycaenid butterfly, Narathura japonica

The spectral sensitivity of a lycaenid butterfly, Narathura japonica, was investigated by electroretinography using an integrating sphere that could illuminate the compound eye from almost all directions. Samples were collected from three locations. Butterflies from different locations showed a similar pattern; the first, second, and third peaks (or a shoulder) were located at about 380, 460, and 560 nm, respectively. Males clearly showed the highest sensitivity at the first peak point. In contrast, females showed a higher relative sensitivity than males at the second and third peak points in all samples, and showed broad spectral sensitivity. This male-specific UV-sensitivity is discussed in terms of ecological factors.     

Neuropharmacological Modification of Male Sexual Behavior in Rats

We studied the dynamics of gaining sexual experience and the parameters of sexual behavior in sexually mature albino rat males subjected to pharmacological modifications of the intensity of catecholamine catabolism or the state of dopamine receptors. A monoamine oxidase inhibitor, nialamide, slowed down gaining of sexual experience and noticeably inhibited all components of the copulative act. A blocker of dopamine receptors, haloperidol, increased the variability of manifestations of the sexual activity, suppressed the motivational component of mating, but accelerated one of the components of copulative behavior (intromission). Possible mechanisms of the influence exerted by modulation of the activity of the monoaminergic systems on male sexual behavior are discussed.     

Sexual reproduction in the invasive species Fallopia japonica (Polygonaceae)

Fallopia japonica (Polygonaceae) is an invasive perennial plant, well known in North America for its ability to spread aggressively via vegetative reproduction. The contribution of sexual reproduction to the distribution of this species is not well documented, and as a result, F. japonica is treated solely as a clonal species. To investigate the role of sexual reproduction in this species, germination experiments were conducted using seed collected from 29 parents from field sites in Massachusetts and from four greenhouse-grown cultivars. Results showed that wild F. japonica produce large quantities of seed that typically have high germinability. This seed is viable whether sown immediately after collection or subjected to various conditions during the winter season and germinated the following spring. Cultivars of F. japonica also produce viable seed and can thus contribute to the invasiveness of this species. In addition, wild F. japonica seedlings were observed at several field sites, with several of these seedlings surviving the winter and resprouting the following spring. That sexual reproduction and seedling survival occur in the wild has strong implications for the development of management strategies for this species.     

Androgen Induction of Male Sexual Behaviors in Female Goldfish

The effectiveness of testosterone (T) and 11-ketotestosterone (K) in inducing male-typical sex behaviors in goldfish was examined by implanting intact adult females with one empty (blank) Silastic implant (B females), one implant containing T or K, or one T and one K implant (T + K females). Behavior of the four female groups was compared to that of untreated males and males containing a blank implant. Male-typical behaviors (coutship, spawning) and associated behavioral changes (increased activity, reduced spontaneous feeding) were assessed 3.5 and 4.5 months after implant in 30-min tests in which the test female or male was allowed to interact with a stimulus female in which sexual receptivity and attractivity had been induced by acute prostaglandin F_2αinjection. Prostaglandin-induced female-typical spawning behavior in the test females and males was also assessed 4.5 months after implant in a 60-min test for female-typical behavior in which the test fish was injected with prostaglandin and placed immediately with a sexually active male. Blood samples 5 months postimplant showed that implants generated physiological levels of T and K. In both tests for male-typical behaviors, K and T + K females exhibited the full suite of behaviors shown by spawning males, e.g., male-typical courtship and spawning, increased swimming activity, and reduced spontaneous feeding. Although behaviors of K and T + K females did not differ, those of T + K females were more often equivalent to those of males and significantly different from those of B females. T females exhibited marginal male-typical behaviors which never differed significantly from those of B females. Androgen-treated females exhibited female-typical; spawning behaviors equivalent to that of males and B females. The results show that adult female goldfish can be behaviorally masculinzed without behavioral defeminization, and suggest that male-typical sex behaviors in goldfish are dependent on K, although other steroids also may be required. The inducible behavioral bisexuality of goldfish, a gonochoristic species, is discussed in terms of the prevalence of hermaphroditism in teleosts.     

On the respiratory mechanism during underwater oviposition in a damselfly Calopteryx cornelia Selys

Calopteryx cornelia females oviposit almost exclusively underwater in forest streams. Field observation showed that the duration of uninterrupted submerged oviposition ranged between 20 and 120 min and the number of eggs laid was linearly related to the time spent underwater. By holding a damselfly under water in a small jar, we measured the maximum 'submergence potential', which was defined as the time elapsed between placing the insect underwater and asphyxiation. A series of experiments showed that there was no gender difference in the submergence potential. This was about 120 min if a damselfly was allowed to change its position while under water. The submergence potential was shorter if the damselflies were kept motionless, if air bubbles trapped on the wing surfaces were removed by coating with Vaseline or if the water was hypoxic. By contrast, submergence potential was longer if a part of the wings were kept above the water surface, or if the water was agitated using a magnetic stirrer. These results suggest that ovipositing C. cornelia females depend for oxygen on the physical-gill action of the thin air layer trapped on the body and wing surfaces. Respiration capacity under water is not likely to be a limiting factor for ovipositing females during the production of a single clutch.     

Improvement of Artificial Foldable Wing Models by Mimicking the Unfolding/Folding Mechanism of a Beetle Hind Wing

<正> In an attempt to realize a flapping wing micro-air vehicle with morphing wings, we report on improvements to our previousfoldable artificial hind wing.Multiple hinges, which were implemented to mimic the bending zone of a beetle hind wing, weremade of small composite hinge plates and tiny aluminum rivets.The buck-tails of rivets were flared after the hinge plates wereassembled with the rivets so that the folding/unfolding motions could be completed in less time, and the straight shape of theartificial hind wing could be maintained after fabrication.Folding and unfolding actions were triggered by electrically-activatedShape Memory Alloy (SMA) wires.For wing folding, the actuation characteristics of the SMA wire actuator were modifiedthrough heat treatment.Through a series of flapping tests, we confirmed that the artificial wings did not fold back and arbitrarilyfluctuate during the flapping motion.