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Mature Males (mature + male)
Selected AbstractsSurvival rates in a natural population of the damselfly Ceriagrion tenellum: effects of sex and female phenotypeECOLOGICAL ENTOMOLOGY, Issue 4 2001Jose A. Andrés Summary 1. Ceriagrion tenellum females show genetic colour polymorphism. Androchrome (erythrogastrum) females are brightly (male-like) coloured while gynochrome females (typica and melanogastrum) show cryptic colouration. 2. Several hypotheses have been proposed to explain the existence of more than one female morph in damselfly populations. The reproductive isolation and intraspecific mimicry hypotheses predict greater survival of gynochrome females, while the density dependent hypothesis predicts no differential survival between morphs. 3. Mature males had greater recapture probability than females while the survival probability was similar for both sexes. Survival and recapture rates were similar for androchrome and gynochrome females. 4. Gynochrome females showed greater mortality or migration rate than androchrome females during the pre-reproductive period. This result is not predicted by the above hypotheses or by the null hypothesis that colour polymorphism is only maintained by random factors: founder effects, genetic drift, and migration. [source] Pheromones in relation to aggregation and reproduction in desert locustsPHYSIOLOGICAL ENTOMOLOGY, Issue 1 2003Hans-Jörg Ferenz Abstract. Desert locusts, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae), exhibit a population density-dependent phase polymorphism which includes the gradual change of many morphological, physiological and behavioural characteristics. Many volatiles associated with desert locusts have been identified recently and it is assumed that they are involved in pheromonal control of behaviour and development of locusts. Ovipositing females deposit with their egg pods several volatiles that appear to be attractive to other females resulting , possibly in combination with environmental factors , in an aggregated oviposition. Mature males release several volatiles, among them phenylacetonitrile, which are reported to accelerate sexual maturation in young males. Also, aggregation pheromone systems for hoppers and adults have been described. However, recent studies and publications shed a new light on the postulated effects of some of these volatiles. Gregarious behaviour can undoubtedly be induced by mechanical stimuli. Furthermore, the main component of the adult aggregation pheromone system, phenylacetonitrile, is found to be a repellent obviously not involved in aggregation. Comprehensive studies have demonstrated that phenylacetonitrile is used by mature gregarious males as a courtship inhibition pheromone to enhance mate guarding. Recent progress, contradictory results and perspectives in desert locust pheromone research related to reproduction are summarized and discussed in this paper. [source] Factors affecting density-independent survival of an island population of tsetse flies in ZimbabweENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2001J.W. Hargrove Abstract Analysis is presented of the factors affecting survival probability in populations of tsetse flies Glossina morsitans morsitans Westwood and G. pallidipes Austen (Diptera: Glossinidae) on Antelope Island, Lake Kariba, Zimbabwe. For mature male and female adult G. m. morsitans mean temperature (Tbar) accounted for 70 and 50%, respectively, of the variance in mark-recapture estimates of survival when the flies were not subjected to trapping. Saturation deficit (SD) only accounted for 36 and 33%, respectively. Maximum temperature (Tmax) and SD accounted for 36,42% of the variance in male and female G. pallidipes. For the corresponding Moran curve estimates of the survival over all developmental stages, SD lagged by three weeks accounted for 61 and 41% of the variance for male and female G. m. morsitans, respectively, and 64 and 56% for G. pallidipes. The corresponding figures for plots against Tmax were 44, 23, 23, and 21%, respectively. The same patterns were seen in the whole data set once allowance was made for the effect of trapping on survival and for an effect of season, correlated with an index of photosynthetic activity. For male G. m. morsitans there was a significant effect of saturation deficit, but not temperature, on immature survival. Decreased adult survival at high temperatures results from the need to feed more frequently and hence to take more risks per unit time. High saturation deficits result directly in reduced emergence of healthy flies from pupae. [source] Acute oral toxicity of colchicine in rats: effects of gender, vehicle matrix and pre-exposure to lipopolysaccharideJOURNAL OF APPLIED TOXICOLOGY, Issue 5 2007Paddy L. Wiesenfeld Abstract The oral toxicity of a single administration by gavage (10, 20 or 30 mg kg,1 body weight) of colchicine (COL) was determined in young, mature male and female Sprague-Dawley rats. The effect of COL was evaluated in the presence or absence of additional treatment variables that included vehicle and lipopolysaccharide (LPS) pre-exposure. The vehicle for COL was either Half and Half cream (H & H) or saline, and each group included pretreatment with either saline or a low, minimally toxic dose (83 µg kg,1 body weight) of LPS. Colchicine toxicity in both male and female age-matched rats was characterized by progressively more severe dose-related clinical signs of toxicity. These included mortality, decreased body weight and feed intake during the first several days after dosing, with recovery thereafter in surviving animals. There were differences in the severity of the toxic response to COL between male and female rats. The most notable sex-related difference was in COL lethality. Female rats were two times more susceptible to the lethal effects of COL than male rats. Saline or H & H delivery vehicles did not result in any apparent qualitative or quantitative differences in COL toxicity. LPS pretreatment significantly potentiated COL lethality in both males and females, although the potentiation in males was greater than in females. LPS pretreatment modestly increased the COL induced anorexic effect in surviving males, but not in surviving female animals. LPS did not appear to modulate either the body weights or clinical signs of COL induced toxicity in surviving males or females. Copyright © 2007 John Wiley & Sons, Ltd. [source] Androgen modulates the kinetics of the delayed rectifying K+ current in the electric organ of a weakly electric fishDEVELOPMENTAL NEUROBIOLOGY, Issue 12 2007M. Lynne McAnelly Abstract Weakly electric fish such as Sternopygus macrurus utilize a unique signal production system, the electric organ (EO), to navigate within their environment and to communicate with conspecifics. The electric organ discharge (EOD) generated by the Sternopygus electric organ is quasi-sinusoidal and sexually dimorphic; sexually mature males produce long duration EOD pulses at low frequencies, whereas mature females produce short duration EOD pulses at high frequencies. EOD frequency is set by a medullary pacemaker nucleus, while EOD pulse duration is determined by the kinetics of Na+ and K+ currents in the electric organ. The inactivation of the Na+ current and the activation of the delayed rectifying K+ current of the electric organ covary with EOD frequency such that the kinetics of both currents are faster in fish with high (female) EOD frequency than those with low (male) EOD frequencies. Dihydrotestosterone (DHT) implants masculinize the EOD centrally by decreasing frequency at the pacemaker nucleus (PMN). DHT also acts at the electric organ, broadening the EO pulse, which is at least partly due to a slowing of the inactivation kinetics of the Na+ current. Here, we show that chronic DHT treatment also slows the activation and deactivation kinetics of the electric organ's delayed rectifying K+ current. Thus, androgens coregulate the time-varying kinetics of two distinct ion currents in the EO to shape a sexually dimorphic communication signal. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007 [source] Elevated organochlorines in the brain,hypothalamic,pituitary complex of intersexual shovelnose sturgeonENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2006Brian T. Koch Abstract Organochlorine compounds (OCs), including polychlorinated biphenyls and organochlorine pesticides, were used on lands adjacent to the Middle Mississippi River (MMR; USA) from 1930 through 1988, and they continue to occur in MMR fish. These compounds are estrogenic and/or antiandrogenic, and they alter hormone production and reception within the brain and gonads of male fish, resulting in intersexuality and/or suppressed gonadal development. To assess how OCs affect reproduction of MMR fish, we quantified OC accumulation, intersexuality, and gonadal development in male shovelnose sturgeon (Scaphirhynchus platorynchus) throughout the MMR during the spring of 2003. Gonads were observed for intersexual characteristics, weighed to calculate the gonadosomatic index (GSI), and examined histologically. Tissue accumulation of OCs was quantified in gonads, brain,hypothalamic,pituitary (BHP) complex, and fillets. Four of 48 mature males were identified macroscopically as intersexuals, and a fifth was found through histology (a 10.4% incidence). Intersexuals accumulated higher concentrations of OCs in the BHP complex compared with those of mature males. In addition, GSI and OC accumulation within the BHP complex, gonads, and fillets of mature males were negatively related. Exposure to OCs before or during sexual differentiation likely induces intersexuality in MMR shovelnose sturgeon, and exposure throughout gonadal maturation inhibits gonadal development. [source] Effects of the androgenic growth promoter 17-,-trenbolone on fecundity and reproductive endocrinology of the fathead minnow,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2003Gerald T. Ankley Abstract Trenbolone acetate is a synthetic steroid that is extensively used in the United States as a growth promoter in beef cattle. The acetate is administered to livestock via slow-release implants; some is converted by the animal to 17-,-trenbolone, a relatively potent androgen receptor agonist in mammalian systems. Recent studies indicate that excreted 17-,-trenbolone is comparatively stable in animal waste, suggesting the potential for exposure to aquatic animals via direct discharge, runoff, or both. However, little is known concerning the toxicity of trenbolone to fish. Our goal was to assess the effects of 17-,-trenbolone on reproductive endocrinology of the fathead minnow (Pimephales promelas). An in vitro competitive binding study with the fathead minnow androgen receptor demonstrated that 17-,-trenbolone had a higher affinity for the receptor than that of the endogenous ligand, testosterone. Male and female fish were exposed for 21 d to nominal (target) concentrations of 17-,-trenbolone ranging from 0.005 to 50 ,g/L. Fecundity of the fish was significantly reduced by exposure to measured test concentrations , 0.027 ,g/ L. The 17-,-trenbolone was clearly androgenic in vivo at these concentrations, as evidenced by the de novo production in females of dorsal (nuptial) tubercles, structures normally present only on the heads of mature males. Plasma steroid (testosterone and ,-estradiol) and vitellogenin concentrations in the females all were significantly reduced by exposure to 17-,-trenbolone. The 17-,-trenbolone also altered reproductive physiology of male fathead minnows, albeit at concentrations much higher than those producing effects in females. Males exposed to 17-,-trenbolone at 41 ,g/L (measured) exhibited decreased plasma concentrations of 11-ketotestosterone and increased concentrations of ,-estradiol and vitellogenin. Overall, our studies indicate that 17-,-trenbolone is a potent androgen and reproductive toxicant in fish. Given the widespread use of trenbolone acetate as a growth promoter, and relative stability of its metabolites in animal wastes, further studies are warranted to assess potential ecological risk. [source] Premating Avoidance of Inbreeding Absent in Female Guppies (Poecilia reticulata)ETHOLOGY, Issue 7 2006Åslaug Viken The recognition and avoidance of kin during mating can be an important means of reducing the potential for inbreeding depression in offspring. We report here that premating mechanisms to avoid inbreeding, either innate or learnt through juvenile experience, are at best weak in female guppies (Poecilia reticulata). Guppies are small, ovoviviparous, neo-tropical freshwater fish, with a polygamous mating system where males actively court females and females are selective of their mates. In a series of mate-choice experiments, naïve, virgin females of the Quare River population in Trinidad were given a choice between a brother and a non-sib male from the same population. Initially, females were only provided olfactory cues upon which to base their choice and then subsequently both olfactory and visual cues. Despite the females displaying mate choice, we found no evidence of them discriminating between the male types in either experiment. There was thus no indication of inbreeding avoidance, suggesting that experiences after maturation or with mature males (e.g. rare male preference), dispersal and/or post-mating mechanisms may be evolutionarily more important avoidance mechanisms. [source] Unstable release strategies in reared Atlantic salmon, Salmo salar L.FISHERIES MANAGEMENT & ECOLOGY, Issue 3 2000S. M. McKinnell The effects of year, size, sexual maturity and release date on the probability of recapture of tagged Atlantic salmon, Salmo salar L., released from a Swedish hatchery in the Baltic Sea were examined. The probability of recapture varied among years for individuals which were juvenile when released (1988, 13.5%; 1989, 4.4%; 1990, 1.2%) or previously mature males (1988, 1.9%; 1989, 0.5%; 1990, 0.4%). Body size was positively associated with the probability of recapture in each release year for both life-history types. Inter-annual changes in recapture rates were similar for both large and small smolts. There was a significant effect of life-history type on recapture rates in 1988 and 1989, but not in 1990. There was a significant effect of release date on recapture rates in 1988 and 1990, but not in 1989. The maximum recapture rates were associated with different release dates in each year, i.e. 27 May 1988, 6 June 1989 and 21 June 1990. [source] Day,night changes in the spatial distribution and habitat preferences of freshwater shrimps, Gammarus pulex, in a stony streamFRESHWATER BIOLOGY, Issue 4 2005J. M. ELLIOTT Summary 1. As many invertebrates are nocturnal, their spatial distribution and habitat preferences may change from day to night. Both aspects are examined for Gammarus pulex by testing the hypotheses: (i) a power function was a suitable model for the spatial distribution of the shrimps in both day and night; (ii) diurnal and nocturnal spatial distributions were significantly different; (iii) diurnal and nocturnal habitat preferences were significantly different. Five different life-stages were treated separately. To ensure that the conclusions were consistent, large samples were taken near midday and midnight in April, June and November over 4 years at two sites about 3 km apart in a stony stream: downstream (n = 30) and upstream (n = 50). 2. The first and second hypotheses were supported at both sites. A power function, relating spatial variance (s2) to mean (m), was an excellent fit in all analyses (P < 0.001, r2 > 0.91), i.e. the spatial variance was density-dependent. All five life-stages were aggregated in the day. At night, the degree of aggregation increased for juveniles at higher densities but decreased for juveniles at lower densities, increased for immature females and males, but decreased slightly for mature females and especially mature males, the latter being close to a random distribution. There were no significant differences between sites, in spite of the lower numbers at the downstream site. 3. The third hypothesis was tested at only the upstream site and supported by comparisons between shrimp densities and 13 physical variables (distance from bank, water depth, water velocity, ten particle size-classes), and three non-physical variables (dry weights of bryophytes, leaf material, organic detritus). During the day, densities were strongly related to particle sizes with the following preferences: 0.5,8 mm for juveniles, 8,256 mm for the other life-stages with a weaker relationship for males. There were no significant positive relationships with the other variables, apart from bryophytes for immature shrimps and adults. At night, densities were unrelated to particle size; juveniles and immature shrimps preferred low water velocities near the banks, often where leaf material and organic detritus accumulated, females often preferred medium water velocities slightly away from the banks, and males showed no habitat preferences. 4. Day samples do not provide a complete picture of habitat preferences and probably identify refuge habitats. Day,night changes in spatial distribution and habitat preferences are an essential part of the behavioural dynamics of the shrimps and should be investigated in other species. [source] Reproduction in puyen, Galaxias maculatus (Pisces: Galaxiidae), in the southernmost extreme of distributionJOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2007C. C. Boy Summary Reproductive aspects of a peripheral population of Galaxias maculatus are described and the relationship with the physiology and handling of energetic reserves under marginal environmental conditions is investigated. The G. maculatus population of Tierra del Fuego has an extended reproductive season, with differences in timing and duration compared to other populations of continental Patagonia, New Zealand and Australia. Elevated gonadosomatic indexes (IG) were observed during this period in both sexes (maximum IG = 33.49% males; 35.94% females). The high abundance of mature males (with high IG values) on the spawning grounds during the reproductive season suggests that they were waiting for the return of the mature females. Larger females reached total maturation at the beginning of the reproductive season, whereas the size of maturing females diminished toward the end (mean TL = 96 mm, October; 70 mm, February). Both sexes showed an extremely high investment in reproduction, reaching a maximum IG of about 35% for both sexes. At the beginning of the reproductive season females reached the maximum median IH (3.37%) and males the minimum (0.96%), suggesting differences in the role of the liver in the management of energetic reserves during sexual maturation. The variation in the fat index (IF) suggests that fat reserves were used to survive winter (maximum median IF > 1%, autumn; minimum about 0.2%, spring). [source] Age and growth of the round stingray Urobatis halleri at Seal Beach, CaliforniaJOURNAL OF FISH BIOLOGY, Issue 3 2008L. F. Hale The age and growth of the round stingray Urobatis halleri was determined using vertebral sections from animals collected at Seal Beach, California from 2002 to 2005. Annual periodicity was validated from U. halleri injected with oxytetracycline and maintained in captivity over a 2 year period (n= 7). The coefficients estimated by the von Bertalanffy growth model were the disc width asymptote (WD,) (286 mm for males and 224 mm for females) and K (0·09 year,1 for males and 0·15 year,1 for females). The age structure of the population consisted of mostly older, mature males and females. Age at maturity was estimated at 3·80 years for females and 3·75 years for males, and the maximum assessed age was 14 years old. Males were more numerous than females throughout the year; however, from May to September, females outnumbered males. The U. halleri age and growth coefficients were comparable to other species in the family Urolophidae. Based on the seasonality and age structure of this population, Seal Beach offers warm-water refuge for U. halleri of reproductive maturity, and the U. halleri at Seal Beach may garner some behavioural thermoregulation benefit. [source] Leptin, body composition, adrenal and gonadal hormones among captive male baboonsJOURNAL OF MEDICAL PRIMATOLOGY, Issue 6 2003M.P. Muehlenbein Abstract:, Morphometric and hormonal measures were collected from 21 captive savanna baboons (Papio cynocephalus) maintained at the Tulane National Primate Research Center in order to determine age-related patterns in leptin levels over the life course as well as their relationships to body composition and adrenal and gonadal steroids. Comparison of leptin levels between peri-pubertal, adolescent, young adult, and fully mature males show lower levels among adolescent as compared with young adult males (P = 0.05 by Kruskal,Wallis ANOVA). In addition, abdominal fat varied among age groups (P = 0.003 by Kruskal,Wallis ANOVA) with the peri-pubertal animals lower than the adolescents, young adults, and prime adults. However leptin was not related to any measure of body composition, including abdominal fat, or to adrenal hormones (dehydroepiandrosterone, dehydroepiandrosterone-sulfate, and cortisol) or gonadal hormones (testosterone and estradiol). Age-related changes in leptin appear similar to those reported for captive rhesus macaques, while the failure to find an association between leptin and abdominal fat is interestingly different. These results confirm elevated levels of leptin in captive baboons compared with their wild counterparts and suggest that they result from changes in fetal development. [source] Reproductive morphology of Brittanichthys axelrodi (Teleostei: Characidae), a miniature inseminating fish from South AmericaJOURNAL OF MORPHOLOGY, Issue 1 2007Robert Javonillo Abstract Light and electron microscopy were used to investigate the morphology of reproductive characters in a characid fish, Brittanichthys axelrodi. Spermatozoa were found in ovaries of females, thereby confirming insemination in this species. Bony hooks can be found on the fourth unbranched ray and branched rays 1,4 of the anal fin and the unique sigmoidally-curved ray of the caudal fin in mature males. Testes have three distinct regions: an anterior spermatogenic region, an aspermatogenic middle region lined with a simple squamous epithelium and used for storage of mature spermatozoa, and a posterior region of coiled chambers lined with a high simple cuboidal epithelium. The most posterior region appears to be instrumental in the formation and storage of spermatozeugmata, unencapsulated sperm packets. Thus far, this tripartite testis morphology is unique among characids. The mature spermatozoon has an elongate nucleus (,5 ,m in length). A striated rootlet originates at the anterior end of the distal centriole and continues to the anterior tip of the cell. The striated rootlet wraps around the entire ventral area of the anterior part of the nucleus and appears to continue around the anterior tip of the nucleus and down the dorsal side as electron-dense material. Several large, spherical mitochondria (,0.6 ,m in diameter) with lamellar cristae overlap the posterior end of the nucleus and continue beyond together with the cytoplasmic collar that contains the flagellum which lacks axonemal fins. Each spermatozeugma is lanceolate in shape when sectioned mid-sagitally, with the core staining positively for mucopolysaccharides. In both sexes, the gonopore opens posterior to the anus, with the urinary pore having a separate opening posterior to the gonopore. Bands of skeletal muscle were found in the area of the male gonopore. These morphological features are likely linked to the reproductive mode of insemination, a trait that is so far as known, relatively rare among teleost fishes, but is proving increasingly frequent among certain groups of characid fishes. J. Morphol, 2006. © 2006 Wiley-Liss, Inc. [source] Sexual selection is not the origin of long necks in giraffesJOURNAL OF ZOOLOGY, Issue 4 2009G. Mitchell Abstract The evolutionary origin of the long neck of giraffes is enigmatic. One theory (the ,sexual selection' theory) is that their shape evolved because males use their necks and heads to achieve sexual dominance. Support for this theory would be that males invest more in neck and head growth than do females. We have investigated this hypothesis in 17 male and 21 female giraffes with body masses ranging from juvenile to mature animals, by measuring head mass, neck mass, neck and leg length and the neck length to leg length ratio. We found no significant differences in any of these dimensions between males and females of the same mass, although mature males, whose body mass is significantly (50%) greater than that of mature females, do have significantly heavier (but not longer) necks and heavier heads than mature females. We conclude that morphological differences between males and females are minimal, that differences that do exist can be accounted for by the larger final mass of males and that sexual selection is not the origin of a long neck in giraffes. [source] Sexual segregation in western grey kangaroos: testing alternative evolutionary hypothesesJOURNAL OF ZOOLOGY, Issue 2 2007A. M. MacFarlane Abstract In sexually dimorphic ungulates, sexual segregation is hypothesized to have evolved because of sex-specific differences in body size and/or reproductive strategies. We tested these alternative hypotheses in kangaroos, which are ecological analogues of ungulates. Kangaroos exhibit a wide range of body sizes, particularly among mature males, and so the effects of body size and sex can be distinguished. We tested predictions derived from these hypotheses by comparing the distribution of three sex,sex size classes of western grey kangaroos Macropus fuliginosus, in different habitats, and the composition of groups of kangaroos, across seasons. In accordance with the predation risk-reproductive strategy hypothesis, during the non-breeding season, females, which were more susceptible to predation than larger males, and were accompanied by vulnerable young-at-foot, were over-represented in secure habitats. Large males, which were essentially immune to predation, occurred more often than expected in nutrient-rich habitat, and small males, which faced competing demands of predator avoidance and feeding, were intermediate between females and large males in their distribution across habitats. During the breeding season, females continued to be over-represented in secure habitats when their newly emerged pouch young were most vulnerable to predation. All males occupied these same habitats to maximize their chances of securing mates. Consistent with the social hypotheses, groups composed of individuals of the same sex, irrespective of body size, were over-represented in the population during the non-breeding season, while during the breeding season all males sought females so that mixed-sex groups predominated. These results indicate that body size and reproductive strategies are both important, yet independent, factors influencing segregation in western grey kangaroos. [source] Life on a limb: ecology of the tree agama (Acanthocercus a. atricollis) in southern AfricaJOURNAL OF ZOOLOGY, Issue 4 2002Leeann T. Reaney Abstract One hundred and sixty-four museum specimens of the tree agama Acanthocercus a. atricollis were measured and dissected to examine sexual size dimorphism, reproduction and diet. Foraging mode and behaviour were also quantified in a wild population to obtain a broader picture of their foraging ecology and to test the hypothesis that tree agamas are ambush foragers. Males and females did not differ significantly in snout,vent length (SVL) or tail length; however, mature males had larger heads than females of the same body size. The smallest female showing sexual maturity was 96 mm SVL and the smallest male was 82 mm SVL. Mean clutch size was 11.3 and was positively correlated with female body size. Reproduction was seasonal and male and female reproductive cycles were synchronous. Testicular volume was greatest during August,September and females contained enlarged follicles during August,December and showed no evidence of multiple clutching. Tree agamas fed on a broad spectrum of arthropods (10 orders), including millipedes, which other lizard taxa have been reported to avoid. Gut contents were dominated numerically by ants (92%), followed by beetles (4%). Volumetrically, orthopterans (26.8%) were most important, followed by beetles (26.3%) and ants (17.9%). Compared to adults, juvenile diet by volume was dominated by ants and consisted of fewer large prey items (e.g. beetles and orthopterans). Seasonal effects in both prey diversity and volume were evident. Tree agamas are classic ambush foragers. They spent only 4% of their time moving and made few movements per minute (mean = 0.4). When stationary, adult tree agamas positioned themselves on tree trunks (34.7%), on lateral branches (41.8%) and occasionally, on the ground (23.4%). No evidence of trophic partitioning (intraspecific niche divergence hypothesis) was found and field observations revealed that males defend territories and engage in combat. This supports the idea that selection may be favouring larger head size in males, as an outcome of male contest competition. [source] Blubber testosterone: A potential marker of male reproductive status in short-beaked common dolphinsMARINE MAMMAL SCIENCE, Issue 3 2009Nicholas M. Kellar Abstract A novel molecular technique was used to measure blubber testosterone (BT) in 114 male short-beaked common dolphins, Delphinus delphis, collected from incidental fishery bycatch and strandings. When these concentrations were compared across maturity states, the mean (± SEM) BT levels of mature D. delphis (14.3 ± 3.0 ng/g) were significantly higher than those of pubertal (2.5 ± 0.5 ng/g, P= 0.006) and immature animals (2.2 ± 0.3 ng/g, P < 0.0001). BT concentrations in mature males were significantly higher in summer months (53.9 ± 2.0 ng/g) than during the rest of the year (7.9 ± 0.69 ng/g, P < 0.0001), indicating reproductive seasonality. An analysis of BT in different anatomical locations showed that hormone concentrations were not homogenous throughout the body; the levels in the dorsal fin were significantly lower than in most other areas (F= 5.39, P= 0.043). Conversely, we found no significant differences in BT concentration with respect to subepidermal depth (F= 2.09, P= 0.146). Finally, testosterone levels in biopsies from 138 free-swimming male D. delphis, of unknown maturity state, sampled off California were found to be of concentrations similar to those from the fishery bycatch and stranding samples and revealed an analogous trend with respect to ordinal date. [source] Relatedness in wild chimpanzees: Influence of paternity, male philopatry, and demographic factorsAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2008Eiji Inoue Abstract In chimpanzees (Pan troglodytes), high-ranking males are expected to have high reproductive success and females typically emigrate upon reaching maturity. Although high average relatedness among males in the same social groups has been assumed, previous reports have indicated that relatedness among males is not necessarily significantly higher than that among females. The paternity of 11 offspring and the relatedness of 50 individuals in the M group of chimpanzees at Mahale Mountains National Park, Tanzania, were investigated using DNA analyses. We determined the fathers of 10 offspring. Two different alpha males sired a total of five offspring, whereas the other males had low reproductive success. The proportion of paternal half-sibling pairs among the 10 offspring was 15.6%. The average relatedness among mature males was significantly higher than that among mature females. The existence of an old male and the long tenure of one alpha male may have contributed to this significant difference. The average dyadic relatedness among mature natal individuals was significantly higher than that in natal-immigrant pairs in which the individuals came from different groups. The average relatedness among immigrant females was similar to that in pairs of natal and immigrant females, suggesting that the immigrants came from various groups. Thus, female transfer acts to maintain low average relatedness within the group. A comparison of our results to those from other study sites suggests that although the average relatedness among adult males does not reach the level of half-siblings, under some circumstances it can exceed the relatedness of females. Am J Phys Anthropol, 2008. © 2008 Wiley-Liss, Inc. [source] Male mating tactics in spider monkeys: sneaking to competeAMERICAN JOURNAL OF PRIMATOLOGY, Issue 9 2010K. Nicole Gibson Abstract I investigated the mating system and male mating tactics for a population of wild spider monkeys (Ateles belzebuth chamek), to identify the behaviors males used to achieve and maintain access to sexually receptive females, and to examine if some males used more tactics than other males and/or had differential access to females. Results show that the mating system mostly involved scramble competition polygyny and that males used a range of mating tactics and behaviors, previously unreported for spider monkeys. The most unusual feature of spider monkey mating behavior was the secretive nature of copulations,nearly all copulations were clandestine, but a few were in the presence of other group members. Fifteen sexually mature males were observed to copulate 43 times. These data provide the first opportunity to evaluate how female availability influences male,male competition. First, the operational sex ratio was highly skewed toward males because usually only one female was receptive in each community per month. Second, females only mated with a few males in their community in any one mating period, but some females mated over the course of multiple consecutive mating periods, eventually mating with most or all of the males in their community. Across all communities, 9 (21%) of the 43 copulations involved a single male,female partner, 20 (47%) involved four males mating with the same female, and males mated with from one to four different females. Fourteen of the 16 total adult males and 1 subadult male (10 total) copulated. One or two males in each community were successful in monopolizing access to receptive females, and these males did not usually have the highest rates of copulation. In this system, clandestine copulations are one behavioral solution to the complex problem of gaining mating exclusivity and, probably, exercising mate choice. Am. J. Primatol. 72:794,804, 2010. © 2010 Wiley-Liss, Inc. [source] Reduced sexual maturation in male post-smolt 1+ Atlantic salmon (Salmo salar L.) by dietary tetradecylthioacetic acidAQUACULTURE RESEARCH, Issue 5 2009Henriette Alne Abstract In the present study, the possible effect of dietary treatment on early sexual maturation in post-smolt Atlantic salmon, without any negative effect regarding growth, was investigated. The experiment was performed using 4400 individually marked (Pit tag) 1+ salmon, fed either a control diet or a diet supplemented with 0.5% tetradecylthioacetic acid (TTA) in duplicates for 3, 6 or 12 weeks after sea transfer. Compared with the control, dietary supplementation of TTA resulted in a threefold reduction in incidence of sexual mature males (0.6% vs. 1.8%). A curve-linear relationship between relative reduction in maturation and weeks of feeding TTA was found, indicating that the effect is most marked as a result of the first weeks of feeding and then levelling off. No negative dietary impact on growth was observed. As the level of fat in the muscle was reduced by dietary TTA, it seems that post-smolt supplemented dietary TTA do not accumulate high enough energy stores to start the maturation process, whereas the energy-enhancing effect of TTA due to increased fatty acid oxidation capacity may maintain the growth potential. Compared with immature salmon, sexually maturing fish revealed increased spring growth before the onset of maturation. [source] | ||||||||||||||||