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.     

Body Size and Morph as Drivers of Copulation Duration in a Male Dimorphic Damselfly

Copulation duration is often highly variable within and among species. Here, we explore the roles of body size, male morph, morph frequency, and alternative reproductive tactics to explain copulation duration in the damselfly Paraphlebia zoe. P. zoe has two male morphs (pigmented or hyaline wings) which differ in reproductive tactics (territorial or non‐territorial behaviors). We also analyze the effects of season as the frequencies of both morphs tend to vary along the reproductive season. In the first non‐experimental year, we found that the relationship between body size and copulation duration depended on the time of year. Early in the season, body size positively correlated with copulation duration, while late in the year, body size negatively correlated with copulation duration. In the second experimental year (when we reversed the frequency of male morphs in the middle of the season: making pigmented males less frequent than hyaline males), size influenced copulation duration as well as morph – body size positively correlated with copulation duration, and hyaline males mated for longer than pigmented males. Contrary to our prediction, changes to the relative abundances of morphs did not influence copulation duration. Hyaline males may be under selection for longer copulation durations to compensate for their reduced access to females, as long copulations potentially lead to more rival sperm to be removed from the female sperm storage organs and/or increased mate guarding. We do not discard, however, other explanations that drive variation in copulation duration such as cryptic female choice and/or predation.     

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.     

Evolution of Multiple Additive Loci Caused Divergence between Drosophila yakuba and D. santomea in Wing Rowing during Male Courtship

In Drosophila, male flies perform innate, stereotyped courtship behavior. This innate behavior evolves rapidly between fly species, and is likely to have contributed to reproductive isolation and species divergence. We currently understand little about the neurobiological and genetic mechanisms that contributed to the evolution of courtship behavior. Here we describe a novel behavioral difference between the two closely related species D. yakuba and D. santomea: the frequency of wing rowing during courtship. During courtship, D. santomea males repeatedly rotate their wing blades to face forward and then back (rowing), while D. yakuba males rarely row their wings. We found little intraspecific variation in the frequency of wing rowing for both species. We exploited multiplexed shotgun genotyping (MSG) to genotype two backcross populations with a single lane of Illumina sequencing. We performed quantitative trait locus (QTL) mapping using the ancestry information estimated by MSG and found that the species difference in wing rowing mapped to four or five genetically separable regions. We found no evidence that these loci display epistasis. The identified loci all act in the same direction and can account for most of the species difference.     

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.     

Vesical Hemorrhages in Male Aleutian Mink Caused by Hypersensitivity to Sulphadimidine

During an outbreak of Salmonella abortion in mink farms receiving food from a central feed plant, sulphamezathine (a 16 % solution of sulphadimidine sodium) was added to the food to combat the infection. After 3 days of medication, some males of the Aleutian type developed severe urinary bleedings. The serum concentration of the drug was not above the recommended value in 2 severely affected animals (1.5 and 1.7 mg/100 ml, respectively). Screening tests for the extrinsic (Thrombotest and Normotest) and intrinsic (cephalin time) coagulation mechanism, fibrinogen assay, fibrinolysis (plasma clot lysis time), and platelet count were not much different from normal. Coagulation or platelet defects did not therefore seem to be the cause of the bleedings. Some of the diseased animals died, and the only necropsy finding was a greatly distended urinary bladder filled with clotted blood. Histologically, hemorrhages and necrotic changes of varying severity were found in the vesical wall. In several cases, the arteries were the structures most evidently affected, indicating that the hemorrhages were due to vascular injury (Fig. 1). The damaged vessels were sporadically occluded by thrombi. The lesions were often most evident in subserosal arteries and in the relatively large arteries situated between the inner circular and the outer longitudinal muscular layer, whereas the submucosal structures were obscured by massive extravasations of red blood cells. Occasionally, the necrotic arteries were surrounded by incipient circumferential cellular accumulations, predominantly mononuclear cells, but some eosinophils were also present (Fig. 2). Thus, in these cases the vascular damage was similar to vascular lesions frequently accompanying viral plasmacytosis (periarteritis nodosa). The possibility exists that the animals were in an early developmental stage of plasmacytosis, but no extravesical changes suggesting plasmacytosis were discovered during the microscopic examination. Although other sulphonamides have occasionally shown toxic properties when administered to mink, this preparation has not, to the authors’knowledge, previously been recorded as injurious to this species. The following experiment was performed to elucidate the toxicity of sulphadimidine sodium to male Aleutian mink.     

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.     

Sympatric shift in a male sexual ornament in the damselfly Calopteryx splendens

Character displacement is a process by which interactions between two species that exhibit similar traits, results in geographical patterns of trait divergence in one or both species. These traits evolve to reduce costs of interspecific interactions in sympatry and thus differ from their condition in allopatry. In male damselflies Calopteryx splendens, large wing spots are sexually selected. However, in sympatric populations with Calopteryx virgo, wing spot size decreases as C. virgo abundance increases. The stability of this pattern is unclear, because previous studies have focused on sympatric populations with potentially fluctuating relative abundances. We studied the wing spot sizes of C. splendens in both sympatric and allopatric populations. Our data show that male C. splendens’ wing spots are larger in allopatry than in sympatry with C. virgo. We suggest that both interspecific aggression and avoidance of interspecific reproductive interactions may result in this pattern, although their relative importance remains unclear.     

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.     

Facilitation of Male Sexual Behavior in Syrian Hamsters by the Combined Action of Dihydrotestosterone and Testosterone

Background

Testosterone (T) controls male Syrian hamster sexual behavior, however, neither of T''s primary metabolites, dihydrotestosterone (DHT) and estradiol (E₂), even in highly supraphysiological doses, fully restores sexual behavior in castrated hamsters. DHT and T apparently interact with androgen receptors differentially to control male sexual behavior (MSB), but whether these two hormones act synergistically or antagonistically to control MSB has received scant experimental attention and is addressed in the present study.

Methodology/Principal Findings

Sexually experienced male Syrian hamsters were gonadectomized and monitored 5 weeks later to confirm elimination of the ejaculatory reflex (week 0), at which time they received subcutaneous DHT-filled or empty capsules that remained in situ for the duration of the experiment. Daily injections of a physiological dose of 25 µg T or vehicle commenced two weeks after capsule implantation. MSB was tested 2, 4 and 5 weeks after T treatment began. DHT capsules were no more effective than control treatment for long-term restoration of ejaculation. Combined DHT + T treatment, however, restored the ejaculatory reflex more effectively than T alone, as evidenced by more rapid recovery of ejaculatory behavior, shorter ejaculation latencies, and a greater number of ejaculations in 30 minute tests.

Conclusions/Significance

DHT and T administered together restored sexual behavior to pre-castration levels more rapidly than did T alone, whereas DHT and vehicle were largely ineffective. The additive actions of DHT and T on MSB are discussed in relation to different effects of these androgens on androgen receptors in the male hamster brain mating circuit.