Multiple mechanisms of phenotype development in the bluehead wrasse

Despite having detailed information on mechanisms mediating sex-typical behavior in many species, we have little understanding of whether the same mechanisms regulate these behaviors when they are performed in the same species under different social contexts. In the five field experiments of this study of bluehead wrasses (Thalassoma bifasciatum), a sex-changing fish, we examined the roles of arginine vasotocin (AVT) and the potent teleost androgen 11-ketotestosterone (11KT) in mediating sexual and aggressive behaviors typical of dominant males. We demonstrated that AVT appears necessary for the assumption of dominant territorial status in males and females, but is sufficient only in the socially dominant terminal phase (TP) male phenotype. Specifically, an AVP V(1) receptor antagonist prevented both TP males and females from gaining dominance over recently vacated territories. However, unlike TP males in a previous study, neither females nor initial phase males responded to AVT treatment with increases in display of TP male typical behaviors when under social conditions that inhibit sex change. Treating females with 11KT did not alter responsiveness to AVT, but did induce male coloration and courtship behavior that was not observed in oil-treated females. Combined with the results of a previous study, these results indicate that the ability of AVT to induce male-typical behavior differs among sexual phenotypes and that this differential responsiveness appears to be dependent on social context and not directly on exposure to 11KT. Furthermore, since 11KT can induce courtship behavior in females that is not affected by AVT, there may be different hormonal mechanisms mediating courtship behavior under different social contexts.     

Territorial behaviour of beaugregory damselfish (Stegastes leucostictus) in response to egg predators

To test the hypothesis that territorial male beaugregory damselfish (Stegastes leucostictus) can assess the degree of threat from egg predators, the aggressive behaviour of both males guarding eggs and males without eggs was recorded when they were presented with either one or five individuals of the wrasse egg predator Thalassoma bifasciatum. Presentations were made in a clear plastic bottle 0.5 m from artificial beaugregory breeding sites in the field. Two measures of aggressive behaviour (downhead threats and time spent within 10 cm of the presentation bottle) were significantly greater for multiple wrasse presentations than for single wrasse presentations, while a third measure (chase attempts) was not. In contrast, chase attempts were significantly greater for males guarding eggs than for males without eggs, but there was no significant difference in the level of downhead threats or bottle proximity time for this comparison. Levels of the three aggressive measures were not correlated with either the amount of eggs or the number of egg clutches present. These results indicate that territorial male beaugregories respond to an increase in the number of intruding egg predators by increasing the levels of low-cost threat behaviour, while the presence (but not the amount) of eggs results in an increase in the amount of higher cost attack behaviour. These experiments, therefore, support the hypothesis that male beaugregories can assess the degree of threat from egg predators, and indicate that they use this assessment to alter the strategies used in territorial defence.     

Components of fertilization success in the bluehead wrasse, Thalassoma bifasciatum

In many species of marine organisms, males and females releasegametes directly into the water column. Although free-spawningmarine invertebrates appear to have highly variable fertilizationsuccess, in tropical reef fishes the average fertilizationsuccess is quite high, typically over 90%; nevertheless, substantialvariation has been reported, and fertilization has a directeffect on fitness. We investigated the factors affecting fertilization success in natural spawnings of the bluehead wrasse, Thalassoma bifasciatum. During a two-year study at a site in St. Croix,we found extensive and predictable variation in fertilizationsuccess in pair spawns of this reef fish. Fertilization successaveraged 95%, but was affected by the amount of sperm released,the water velocity at a site, the mating success of the male,and the size of the female. As sperm released in a spawn increases, and as water velocity at a site decreases, sperm concentrationsshould remain higher in the vicinity of eggs for a longer periodof time, and both of these factors are correlated with increasingfertilization success. The recent history of individuals withpartners or sites did not affect the fertilization successof their spawn. In an evolutionary context, the real and predictable variance in fertilization success in this species may influencethe mating choices of males and females. However, there iscurrently no evidence that females use differences in fertilizationsuccess among males or sites in their reproductive decisions.     

Morphology of gonoducts and male genital papilla, in the bluehead wrasse: implications and correlates on the control of gamete release

In the coral reef fish Thalassoma bifasciatum , males vary the number of sperm they release in successive spawnings with individual females in accordance with female body and clutch size. The morphology and histological structure of the male genital papilla, sperm duct, oviduct and surrounding musculature were examined in an effort to elucidate the mechanism permitting control of the number of gametes released during mating. In males, urinary and genital ducts pass separately through a common urogenital papilla and are associated with a striated sphincter muscle and a pair of thin, smooth ligament muscles arising from the first proximal anal fin radial and passing laterally around the sperm duct and oviduct. Within the papilla, the sperm duct resembles a narrow funnel whose inner walls contain longitudinal folds or septa protruding into the lumen of the duct. Dorsal to the papilla, the sperm duct enlarges and is divided into numerous, open chambers by irregular, longitudinal trabeculae. The wall of the duct and the trabeculae contain flat epithelium, smooth muscle and loose connective tissue. In females, the oviduct contains no trabeculae and is not divided into chambers. The ligament muscles are more thoroughly embedded in the sphincter muscle of the rectum than in males. Some ways in which these structures might control gamete release are suggested.     

sGnRH-A [(d-Arg6, Pro9, NEt-)LHRH] in combination with domperidone induces gonad reversal in a protogynous fish, the bluehead wrasse, Thalassoma bifasciatum

The effects of thrice weekly injections of Ovaprim (sGnRH-A in combination with domperidone) on the ovary of Thalassoma bifasciatum , a protogynous marine fish, after 4 and 6 weeks are described. At the end of 4 weeks of treatment, 72% ( n =13) of the original females showed signs of reversal. The majority of these were deemed early stage although mid- ( n =2) and late ( n =1) stage reversals were present. At 6 weeks, 92% of the females had ovaries that were undergoing transformation. None of these, however, progressed beyond the early stage. Only 3.8% of the control fish showed signs of reversal over the same periods. The blue head colour pattern, typical of the terminal phase, did not appear in any of the fish.
To our knowledge, this is the first report investigating the hypothalamic influence on sex reversal in T. bifasciatum . These observations shed new light on the neuroendocrine control of reversal of gender in this species and hermaphroditic fishes in general.     

Microtubules in the epidermal cells of Carausius morosus (Br.). Their pattern and relation to pigment migration

The existence of one or several systems of microtubules, consisting of a central bundle that branches off towards the basal and distal ends of epidermal cells of Carausius morosus has been shown by indirect immuno-fluorescence microscopy using monospecific anti-tubulin. The pattern of microtubules coincides with the position of the ommochrome granules and their migration path during physiological colour change. The ommochrome granules stick to isolated bundles of microtubules. Small bundles of microtubules extend almost perpendicularly towards the apical cell membrane where they are attached. Distally they are covered by pore channels within the cuticle. Parallel to the basal cell membrane and in close contact with it, there are very small bundles of microtubules. These findings strongly support the idea that during physiological colour change the ommochrome granules migrate along a firmly fixed system of microtubules.     

Manipulations of the AVT system shift social status and related courtship and aggressive behavior in the bluehead wrasse

Arginine vasotocin (AVT) and its mammalian homologoue arginine vasopressin (AVP) influence male sexual and aggressive behaviors in many species. We tested the effects of AVT and an AVP-V(1a) receptor antagonist on the display of alternative male tactics in a tropical coral reef fish, the bluehead wrasse Thalassoma bifasciatum. We gave AVT injections to territorial and nonterritorial males of the large and colorful phenotype (terminal phase) and an AVP-V(1a) receptor antagonist, Manning compound, to territorial males in the field. AVT increased courtship independent of status, while its effects on territoriality and aggression were dependent upon male status. In territorial males, AVT increased courtship and tended to decrease the number of chases toward initial phase individuals. In nonterritorial males, AVT increased courtship, chases toward initial phase individuals, and territorial behavior while decreasing feeding. These are all behaviors rarely seen in nonterritorial males, so AVT made these males act like territorial TP males. The AVP-V(1a) receptor antagonist had opposite effects. It decreased courtship and territorial defense, making these males act more like nonterritorial males. Manipulations of the AVT system shifted males within a single phenotype from the nonterritorial social status to the territorial social status and vice versa. Since the entire suite of behaviors related to territoriality was affected by AVT system manipulations, our results suggest that the AVT system may play a key role in motivation of behaviors related to mating.     

Large mating aggregations and daily long-distance spawning migrations in the bluehead wrasse,Thalassoma bifasciatum

Synopsis The mating system of the labrid fishThalassoma bifasciatum has been extensively described in the literature, and the species has formed the basis for much work in ecology and behavior. However, most work in the past on this species has concentrated in small patch reef habitats. Here I describe a different mating pattern in bluehead wrasses occurring on a large, linear barrier reef in St. Croix, U.S. Virgin Islands. On this reef, very large group-mating aggregations (> 10000 fish) form daily at a single area on the forepart of the reef. Tagging studies showed that fishes are faithful to particular feeding schools arrayed along the forereef, and that they migrate to the spawning grounds along a specific path from distances more than 1.5 km away. No mating appears to occur in other upcurrent areas of the forereef. One-way migration times averaged 52 min from the farthest site studied, and feeding does not occur en route. Despite large differences in time spent in migration, no significant differences existed in fecundity or frequency of spawning among females living at different distances from the mating aggregation. The only apparent differences was a significantlyhigher growth rate in the fishes residing farthest from the aggregation. This higher growth rate corresponded to a higher overall feeding rate in the distant location, suggesting that food intake can more than compensate for the increased costs of migration.     

Variation in aggressive behaviour in the poeciliid fish Brachyrhaphis episcopi: Population and sex differences

Aggression is often positively correlated with other behavioural traits such as boldness and activity levels. Comparisons across populations can help to determine factors that promote the evolution of such traits. We quantified these behaviours by testing the responses of wild-caught poeciliid fish, Brachyrhaphis episcopi, to mirror image stimuli. This species occurs in populations that experience either high or low levels of predation pressure. Previous studies have shown that B. episcopi from low predation environments are less bold than those that occur with many predators. We therefore predicted that fish from high predation populations would be more aggressive and more active than fish from low predation populations. However, we found the opposite - low predation fish approached a mirror and a novel object more frequently than high predation fish suggesting that ‘boldness’ and aggression were higher in low predation populations, and that population-level boldness measures may vary depending on context. When tested individually, low predation fish inspected their mirror image more frequently. Females, but not males, from low predation sites were also more aggressive towards their mirror image. Variation in female aggression may be driven by a trade-off between food availability and predation risk. This suggests that the relationship between aggression and boldness has been shaped by adaptation to environmental conditions, and not genetic constraints.     

Immunocastration reduces aggressive and sexual behaviour in male pigs

The aim of this study was to evaluate the effectiveness of a gonadotropin-releasing hormone (GnRH) vaccine, Improvac™ (Pfizer Ltd), in suppressing aggressive and sexual behaviour of male pigs. One hundred and thirty-six pigs were assigned to three treatments: entire male pigs (n = 64), immunocastration against GnRH (n = 48) and surgical castration (n = 24). Surgical castration was performed before the age of 1 week. Vaccination comprised two injections: the first injection was given 8 to 11 weeks before slaughter and the second injection 4 weeks before slaughter. After the second injection, immunocastrated pigs showed less non-violent social and aggressive behaviours than entire male pigs of the same age. Mounting was reduced to the same low level as observed in surgically castrated pigs, and more immunocastrated pigs were without skin lesions compared with entire male pigs. Pigs that received the second injection only 1 week before the observation day did not differ significantly in behaviour from those that received the injection 3 weeks before the observation day. Thus, the behaviour seems to change soon after the second injection and these changes remain until slaughter.     

Colour perception of single and mixed monochromatic lights in the blowfly Lucilia cuprina

Colour perception of spectral lights and mixtures of two monochromatic lights of blue and yellow wavelengths was studied in the blowfly Lucilia cuprina by using a generalization test in which the fly had to compare these lights in memory with coloured papers (blue, green, yellow and red) represented in the test array. Flies trained to a monochromatic light in the wavelength range of 429–491 nm responded to blue; those trained to 502–511 nm to green; and those trained to 522–582 nm to yellow. The maximal generalization for blue was found at 429 nm and that for yellow at 543 nm. Flies trained to the mixtures responded neither to blue, green nor yellow, when the blue component was mixed with the yellow component in a ratio of approximately 1 3. It seems that the fly perceives the mixtures as a neutral or an achromatic light. Colour loci of coloured papers, spectral lights and mixtures of two monochromatic lights used formed blue, yellow and neutral clusters in a colour triangle with respect to generalization responses to test colours.     

Reproductive parameters in relation to food supply in the whiskered tern ( Chlidonias hybrida )

It is generally accepted that breeding terns are sensitive to food supply and that their reproductive effort could be substantially affected by the availability and access to resources. In this study we examined reproductive parameters in the whiskered tern Chlidonias hybrida in relation to food supply during the courtship feeding period (food brought by males to females) over a 2-year period (2004–2005). We also studied whether the condition of the nestlings [body condition index (BCI)] was related to a proxy of the reproductive investment of the adults (the clutch size) during a season of food shortage. Behavioural observations showed a decrease in the intensity of male courtship feeding between years (2004 > 2005), and a strong shift in the relative abundance of the two prey groups (invertebrates/fish; invertebrate prey dropped from 88.0 to 49.3%) brought by males. This change in food delivery rates did not result in a delay in laying, but there was a significant difference in mean clutch size between years (2.71 ± 0.49 eggs in 2004 and 2.05 ± 0.78 eggs in 2005) without any within-year variation in relation to the laying dates. The egg size (volume and length) was related to the year (2004 < 2005), suggesting a trade-off in the quantity and the quality of eggs between the two seasons. We also found no evidence that the investment in a large clutch affected nestling BCI in the course of the food shortage season. Since many pairs (about 60%) interrupted breeding during the incubation stage, we assumed that parents that succeeded in rearing nestlings in these conditions were probably ‘high-quality’ individuals. Our results therefore showed that whiskered terns are sensitive to the varying food conditions they experienced throughout the courtship period. The diversity of prey types could be a key factor in the reproductive investment of this tern species.     

星豹蛛求偶和交配行为

以星豹蛛(Pardosa astrigera)为研究对象,在室内对其求偶和交配行为进行了描述。雄蛛"俯卧撑"式动作(push-up)在求偶中具重要作用。交配初期,两侧触肢交替插入;随交配进行,单侧触肢连续插入3~5次后才换另一侧触肢插入,触肢每插入一次,基血囊膨大多次。完整交配一次雄蛛触肢器平均插入次数为29·625。交配前求偶时间、交配持续时间和有效交配时间分别平均为6min、32min25s和11min11s。星豹蛛雄蛛可进行多次交配,而雌蛛一般为单次交配。雌蛛交配状态(是否已经交配)影响其同类相食行为,已交配雌蛛对雄蛛同类相食率显著高于未交配雌蛛对雄蛛同类相食率。     

Cortisol administration to pregnant sows affects novelty-induced locomotion, aggressive behaviour, and blunts gender differences in their offspring

Several behavioural effects of prenatal stress are reported in literature, and these seem to depend, among other factors, on the gender studied and the period of gestation in which prenatal stress is applied. In the present study, oral administration of hydrocortisone-acetate (HCA) to 41 pregnant sows was used as a model for prenatal stress, since corticosteroids are considered a key mediator in the effects of prenatal stress. HCA was orally administered to pregnant sows during three periods of gestation: 21-50 (period 1, P1, n = 10), 51-80 (period 2, P2, n = 10) and 81-110 (period 3, P3, n = 10) days after insemination (term 115 days). Control sows (n = 11) received vehicle from 21 to 110 days after insemination. Between days 9 and 48 after birth, treatment effects on male and female piglet behaviour were determined in the home pen and in four different behavioural tests. During the backtest, no gender differences were observed in vocalisations in HCA-piglets, while control males vocalised more than control females. In the home pen at 14 days of age, HCA-piglets spent less time in social interactions than control piglets. During the novel environment test, P1- and P3-piglets walked more than control piglets, but this was not observed during the novel object test, four days later. At weaning, P2- and P3-piglets performed less individual play. Prior to mixing with an unfamiliar piglet (male piglets only), HCA-piglets had lower salivary cortisol concentrations than control piglets, but no difference was observed after mixing. P1-, P2-, and P3- piglets had fewer non-aggressive encounters, and P2-piglets continued fighting longer than control piglets. The present study demonstrates that elevated maternal cortisol concentrations during gestation affect piglet behaviour, and effects do differ between male and female piglets. In addition, effects depend on the period of cortisol administration.     

Acoustical and sexual behaviour in the grasshopper Chimarocephala pacifica pacifica (Oedipodinae)

The oedipodine grasshopper Chimarocephala pacifica pacifica employs a variety of acoustic and visual signals for communication between the sexes and between members of the same sex. These signals, which are expressed in the form of stridulations and vibrations by the male or as the waving-gesture by both sexes, characterize either the premating and mating state or the state of disturbance and defence, depending on the circumstances that elicit these expressions. The occurrence and timing of copulation are dictated by the cyclic sexual receptivity and non-receptivity behaviour phases of the female. Oscillograms and spectrograms of vibration and stridulation by the male are presented. The behaviour terminology employed in grasshopper studies is critically reviewed.

---

Zusammenfassung Die Heuschrecke Chimarocephala pacifica pacifica (Oedipodinae) verwendet eine Anzahl verschiedener akustischer und visueller Signale zur Verständigung zwischen Männchen und Weibchen und zwischen gleichgeschlechtigen Artgenossen. Diese Signale, die vom Männchen in Form von Gesängen und Vibrationen erzeugt werden, und von beiden Geschlechtern als Winkgebärden, charakterisieren den Zustand entweder vor oder während der Geschlechtsreife, oder sie sind typisch für die Abwehrphase. Das zeitliche Auftreten der Paarung wird bestimmt von der zyklischen sexuellen Bereitschaft bzw. der Abwehr des Weibchens. Spektrogramme und Oszillogramme von der Vibration und Stridulation des Männchens werden gezeigt. Die bei Heuschreckenstudien verwendete Verhaltensterminologie wird kritisch überprüft.

     

Pre‐ and postcopulatory sexual selection favor aggressive,young males in polyandrous groups of red junglefowl

A challenge in evolutionary biology is to understand the operation of sexual selection on males in polyandrous groups, where sexual selection occurs before and after mating. Here, we combine fine‐grained behavioral information (>41,000 interactions) with molecular parentage data to study sexual selection in replicated, age‐structured groups of polyandrous red junglefowl, Gallus gallus. Male reproductive success was determined by the number of females mated (precopulatory sexual selection) and his paternity share, which was driven by the polyandry of his female partners (postcopulatory sexual selection). Pre‐ and postcopulatory components of male reproductive success covaried positively; males with high mating success also had high paternity share. Two male phenotypes affected male pre‐ and postcopulatory performance: average aggressiveness toward rival males and age. Aggressive males mated with more females and more often with individual females, resulting in higher sexual exclusivity. Similarly, younger males mated with more females and more often with individual females, suffering less intense sperm competition than older males. Older males had a lower paternity share even allowing for their limited sexual exclusivity, indicating they may produce less competitive ejaculates. These results show that—in these populations—postcopulatory sexual selection reinforces precopulatory sexual selection, consistently promoting younger and more aggressive males.     

The intensity of sexual selection in relation to male sexual behaviour,female choice,and sperm precedence

In this paper we define sexual selection on males as the variance in numbers of mates per male and show how the intensity of this selection is affected by male sexual behaviour, female choice, sex ratio, and modes of sperm precedence. This definition coincides with Darwin's conception of sexual selection but differs from some post-Darwinian views. For systems of single-male paternity, we show that the intensity of total selection on male reproductive success equals the intensity of natural selection on female fertility, times the sex ratio, plus the intensity of sexual selection on males. The absolute intensity of sexual selection is unaffected by the system of sperm precedence. The application of the results to field studies is discussed.