Reproduction of the large fruit-eating bat Artibeus lituratus (Chiroptera: Phyllostomidae) in a Brazilian Atlantic forest area

In this study we investigated the male testicular activity and the reproductive condition of females in relation to their external reproductive characteristics (pregnant, lactating, post-lactating) in the phyllostomid bat Artibeus lituratus (Olfers, 1818). Five hundred and twenty six individuals were examined (197 males and 329 females) in the period December 2001 to May 2003. Throughout the study most males displayed large scrotal testes. Thirty-three males were randomly selected for histological examination at various times throughout the year and were found to have spermatogenic testes. The reproductive characteristics of the females indicated that they were reproductively active mainly during the wet season. Pregnancy occurs at the end of the dry season and parturition in the wet season. Most individuals captured after this season, mainly the females, were sexually immature. Our results suggest a seasonal monoestrous reproductive pattern for the species; however, adult males being fertile throughout the year could suggest polyoestry. Seasonal polyoestry is a possibility. There was, however, no evidence that females had more than one pregnancy per year.     

Interannual fluctuations in recruitment and growth of the sardine,Sardinops melanostictus,in the sea of Japan and adjacent waters

Recruitment and growth of the sardineSardinops melanostictus fluctuated markedly in the Sea of Japan and adjacent waters between 1978 and 1993. Stock size was calculated using Virtual Population Analysis and average body length in each age class was determined by the number of annual rings on the scales. There is an inverse correlation between average water temperature at a depth of 50 m in the coastal area of the mainland of Japan in winter (January to March) and recruitmentR defined as the number of individuals at 1 year old. There is also an inverse correlation between spawning stock sizeE and reproductive success in (R/E). A multiple regression model using spawning stock size and water temperature in winter as independent variables can explain 73% of variance in reproductive success. It suggests that both density-dependent and density-independent factors perform important roles determining reproductive success. There is an inverse correlation between body length and stock size and this suggests that there is a density-dependent effect on the growth of the sardine.     

Testicular and spermatozoan parameters in the pukeko (Porphyrio porphyrio melanotus)

The pukeko (Porphyrio porphyrio melanotus) is widespread in New Zealand, and is the closest living relative to the endangered takahe (Porphyrio mantelli), which has a relatively high rate of infertility. In this study, sperm collected from a number of pukeko was analysed in order to model the reproductive physiology of the male takahe. In addition, testicular parameters were measured. To ascertain the best method of sperm collection five techniques for harvesting sperm were used on two occasions during the breeding season. All five techniques resulted in the successful recovery of sperm. However, the float-out technique produced the best quality samples. Following collection, the morphometry of unstained sperm was assessed. Our findings suggest that pukeko sperm is non-motile in the male reproductive tract. We found the mean sperm head length in the pukeko is 16.9mum, but sperm head length varied significantly between birds. Testicular weight and length was significantly correlated with bird weight (P<0.05). Within each bird, testes weights were asymmetric. However, testes length was significantly correlated (P<0.05). There was a significant difference (P<0.05) in testes length between birds. The methodologies presented for obtaining and analysing pukeko sperm morphometry can be used to assist opportunistic studies of the reproductive biology of other New Zealand native birds.     

Fruit production and floral traits: correlated evolution in <Emphasis Type="Italic">Govenia</Emphasis> (Orchidaceae)

The most common estimate of reproductive success in orchids is usually fruit set. Factors such as resource limitation and certain floral traits may influence reproductive success in animal-pollinated plants. Correlated evolution of reproductive success vs. seven floral traits (inflorescence length, flower number, flower distribution along inflorescence, dorsal sepal length, lateral sepal length, flower color, and column position) was studied in eight species of Govenia. Taxa represented three lineages in the genus. Independent contrasts were calculated on a phylogeny inferred from chloroplast (trnL-F IGS) DNA sequences, and a correlation test and multiple regression were then performed. Two data sets were evaluated, one including all eight species and another excluding G. utriculata, which is autogamous. The historical analyses showed that there is a correlation between reproductive success and dorsal sepal length, column position, and flower number, these correlations suggest that changes in these floral traits usually accompany evolutionary shifts in reproductive success. Multiple regression tests suggest that changes in reproductive success can be explained by shifts in flower number, inflorescence length, column position and by dorsal sepal length. When phylogeny is taken into account, our analyses showed that evolutionary shifts in these floral traits were correlated with changes in reproductive success. Evolutionary correlation between reproductive success and floral traits might be explained by the natural selection of certain floral phenotypes by pollinators.     

Reproductive condition of Akodon montensis Thomas and Bolomys lasiurus (Lund) (Rodentia, Muridae) based on histological and histometric analyses of testes and external characteristics of gonads

The reproductive activity of two species of wild rodents was studied in the Serra do Rola‐Moça State Park (PERM), in the state of Minas Gerais, Brazil. From October 1998 to October 1999 specimens of Akodon montensis (Thomas 1913) were captured in an area of seasonal semi‐deciduous forest, while specimens of Bolomys lasiurus (Lund 1840) were captured in a cerrado area (a savannah‐like grassland). The determination of the reproductive condition was based on histological and histometric analyses of testes and external characteristics of gonads. The volume of the testes, diameter of the seminiferous tubules and depth of the seminiferous epithelium were measured. Akodon montensis showed a seasonal annual reproductive cycle divided into four stages (recrudescence, activity or proliferation, regression and rest) with the reproductive activity mainly occurring during the rainy season. In contrast, B. lasiurus presented reproductive activity during almost the whole year. For both species the volume of the testes was an effective indicator of their reproductive condition. We suggest that the histological and histometric analysis of the gonads of males, together with the observations of external characteristics of gonads of males and females, may assist in identifying the reproductive condition of these animals.     

On noninvasive assessment of the reproductive status of male Campbell’s dwarf hamsters (<Emphasis Type="Italic">Phodopus campbelli</Emphasis>) using digital images

The possibility of estimating the reproductive status of males using computer analysis of the contours of testes and midventral gland (MVG) in digital images was tested in Campbell’s dwarf hamsters (Phodopus campbelli). Relationships between the anogenital distance (AGD) and the diameters of testes and MVG were analyzed. The Pearson coefficient of correlation between the actual size of testes and that estimated from their visible contours proved to depend on the amount of white fat and varied from 0.9 in low-fat to 0.67 in high-fat hamsters. A strong correlation was revealed between the AGD and the diameter of testes in digital images. Both these parameters proved to be significantly greater in the reproductive period than in the non-reproductive (winter) period, while the diameter of MVG remained unchanged. These results agree with data on the winter ecology of Campbell dwarf hamsters and confirm that the above method can be used for assessing seasonal changes in the reproductive status of males.     

Effects of parental body condition and size on reproductive success in a tenebrionid beetle with biparental care

Abstract. 1. The beetle Parastizopus armaticeps (Coleoptera: Tenebrionidae) inhabits the Kalahari desert of southern Africa, constructs breeding burrows after rainfall, and shows extensive biparental care. Previous work has shown that it is predominantly male size, not female size, that determines breeding success; however, in the field these beetles show size assortative mating. This might obscure or override effects of female size on reproduction. Moreover, the inaccessibility of the breeding burrows makes it impossible to test effects of female and male size on offspring development and survival before adulthood. 2. To disentangle the effects of male and female length, body mass, and body condition on reproductive success, males and females were paired randomly in small breeding cages in the laboratory (n = 887 breeding pairs). The construction of the breeding cages allowed a clear view of the brood chamber contents at each stage in offspring development. Larva, pupa, and imago numbers and development were monitored daily, and imago mass at hatching from the pupa (hatchlings), offspring mass, and offspring body length at complete exoskeleton melanisation (juveniles) were determined. 3. There was a weak positive correlation between body condition and body length for females only. Breeding chronology was related to male body condition: males in better condition were fast to start and finish a breeding bout. Males in better condition produced heavier hatchlings and juveniles, and larger‐sized males produced larger‐sized juveniles. In contrast, numbers of larvae and juveniles produced were determined mainly by female length and body condition: larger females in better condition hatched more larvae and produced more offspring. 4. The results suggest that male size and condition will be the most important determinant of reproductive success under relatively dry conditions, when burrow length is critical for reproductive success. Female size might be more important for the pair's reproductive success under wet breeding conditions, when burrow length is less critical for successful reproduction.     

SEXUAL SELECTION IN THE BARN SWALLOW HIRUNDO RUSTICA. III. FEMALE TAIL ORNAMENTS

Male secondary sexual characters are often expressed in females, and the maintenance of the character in females can be due to either direct selection on females favoring the maintenance of the trait, or a correlated response to selection in males. Here I report on determinants of and phenotypic selection on tail length of female barn swallows Hirundo rustica. The homologous trait in males is under strong directional sexual selection. Female tail length was positively associated with several reproductive parameters including total seasonal reproductive success, even when controlling for year and age effects. A change in female tail length from one year to another was often associated with a change in the reproductive parameters correlated with absolute tail length. There was little evidence for an association between female tail length and the duration of the incubation period (only females incubate) and absolute and relative female provisioning rates of offspring, and subsequent size of offspring. Tail length of female barn swallows was positively correlated with that of their mates. Female tail length was a heritable trait as determined from regression of the tail trait of offspring on that of their mother and their father, and there was a positive genetic correlation between the tail trait in males and females. In conclusion, female tail length reliably reflects female reproductive potential, and the trait appears to be under directional selection, which may result in an evolutionary response to selection because of the heritability of the tail trait.     

Size delays female senescence in a medium sized marsupial: The effects of maternal traits on annual fecundity in the northern brown bandicoot (Isoodon macrourus)

The degree to which females allocate resources between current reproduction, future fecundity and survival is a central theme in life history theory. We investigated two hypotheses proposed to explain patterns of reproductive investment, terminal investment and senescence, by examining the effects of maternal traits (age and maternal mass) on annual fecundity in female northern brown bandicoots, Isoodon macrourus (Marsupialia: Peramelidae). We found that annual fecundity in females declined in their final year of reproduction, indicating reproductive senescence. Maternal mass significantly influenced the rate of senescence and, in turn, a female's lifetime reproductive output. Mass had little effect on fecundity in 1st and 2nd year females, but a positive relationship with fecundity in 3rd year females. This meant that heavy, 3rd year females did not suffer the decline in fecundity shown in light 3rd year females. For 1st year females, mass and leg length increased between their first and second reproductive seasons, indicating a temporary shift, from the allocation of resources to reproduction, to increasing condition or structural size post their first breeding event. There were no net changes to body mass in subsequent years. We suggest that this year of post‐reproductive growth has important consequences for senescent effects on reproduction. Overall, results provided support for the effects of senescence on annual fecundity. Our findings were not consistent with the terminal investment hypothesis; reproductive output did not increase in females' final reproductive season despite a rapid decline in survival. However, this notion cannot be entirely dismissed; other measures of reproductive performance not examined here (e.g. offspring mass) may have provided an indication that females did increase their effort at the end of their lifespan. This study highlights the difficulty of measuring reproductive costs and the importance of understanding the combined effects of specific characteristics of an individual when interpreting reproductive strategies in iteroparous organisms.     

Timing of reproductive behaviour in male musk turtles,Sternotherus odoratus: effects of photoperiod,temperature and testosterone

Although male turtles are usually regarded as having a post-nuptial pattern of gonadogenesis (i.e. gonadal growth dissociated from time of mating), they do mate both in the spring (when testes are regressed, plasma testosterone levels are low, epididymides are enlarged, and temperature and daylength increasing) and in the autumn (testes and epididymides are enlarged, plasma testosterone levels are elevated, and temperature and daylength are decreasing). Therefore different proximate cues may operate in mediating male reproductive behaviour at different times of year. When temperature, photoperiod and testosterone levels were altered in male Sternotherus odoratus during the year in both laboratory and semifield conditions, reproductive behaviour occurred more readily in autumn than in spring (the supposed major breeding period). Short daylength was the key environmental condition stimulating male sexual activity, while temperature changes ‘fine-tuned’ this behaviour. Testosterone was effective in stimulating male behaviour only under certain environmental conditions and males could become refractory to artificially elevated plasma testosterone levels.     

Postcopulatory sexual selection is associated with accelerated evolution of sperm morphology

Rapid diversification of sexual traits is frequently attributed to sexual selection, though explicit tests of this hypothesis remain limited. Spermatozoa exhibit remarkable variability in size and shape, and studies report a correlation between sperm morphology (sperm length and shape) and sperm competition risk or female reproductive tract morphology. However, whether postcopulatory processes (e.g., sperm competition and cryptic female choice) influence the speed of evolutionary diversification in sperm form is unknown. Using passerine birds, we quantified evolutionary rates of sperm length divergence among lineages (i.e., species pairs) and determined whether these rates varied with the level of sperm competition (estimated as relative testes mass). We found that relative testes mass was significantly and positively associated with more rapid phenotypic divergence in sperm midpiece and flagellum lengths, as well as total sperm length. In contrast, there was no association between relative testes mass and rates of evolutionary divergence in sperm head size, and models suggested that head length is evolutionarily constrained. Our results are the first to show an association between the strength of sperm competition and the speed of sperm evolution, and suggest that postcopulatory sexual selection promotes rapid evolutionary diversification of sperm morphology.     

Molecular evidence for mating asymmetry and female choice in a pocket gopher (Thomomys) hybrid zone

This paper presents circumstantial evidence that the mating system of the North American pocket gophers (Rodentia: Geomyidae) is a promiscuous one, with female choice at its base. A molecular marker (a length variant in the mitochondrial Control region [D-loop]) is used to show mating asymmetry in a hybrid zone between the species Thomomys bottae and Thomomys townsendii in north-eastern California. All hybrids result from a bottae mother × townsendii father cross. Because of significant differences in body size and resulting burrow diameter, bottae females must have actively sought their respective townsendii mates for the asymmetry in mating to have occurred, signalling female choice in these subterranean mammals that are otherwise characterized by exclusive-use territories, skewed adult sex ratio in favour of females, and high variance in male reproductive success.     

Testosterone and testes size in mallards ( Anas platyrhynchos )

The steroid hormone testosterone (T) mediates the expression of many secondary sexual characters, including behaviors which influence male reproductive success. Testes are one of the major sources of androgens, in particular of T. Although a positive relationship between testes size and T levels could be hypothesized, it has rarely been tested intraspecifically. We investigated this link in mallards (Anas platyrhynchos) using a double-antibody radioimmuno-assay to measure hormone levels and X-rays to determine testes size. Here, we report a positive correlation between both traits in a group of 13 drakes during the reproductive season.     

Seasonal variation in testes size in Polish Merino rams and its relationship to reproductive performance in spring

Observations relating testes size to body weight in growing and adult Polish Merino rams were performed during 3 consecutive years in a flock of 1700 pedigree ewes. October-born ram lambs were measured for testis diameter (TD), scrotal circumference (SC), and body weight (BW) at 100 (January), 150 (March), 180 (April), 240 (June), 365 (October), and 480 d (February) of age. In adult rams (n = 63 to 73 per year) BW and SC were measured in March, May (prior to breeding), August and October. Semen quality was evaluated before each breeding season, and the results of controlled reproductive performance (2 natural services to designated rams) were analyzed. Indices were applied to relate testis size to body weight: TD BW , SC BW and TW BW . Heritability estimates of testes indices in ram lambs at 100 to 240 d and at 480 d of age ranged from 0.21 to 0.36 (SE = 0.067 to 0.090). In adult rams SC measurements within months in consecutive years were repeatable (r = 0.55 to 0.68; P相似文献   

阿根廷滑柔鱼年间生长及体征变化

阿根廷滑柔鱼(Illex argentinus)的生长发育及体征变化,可表征其能量积累和生殖投入方面的生活史策略,并随之影响繁殖成效和资源补充量。为此,研究根据2012—2014年在西南大西洋索饵育肥场采集的阿根廷滑柔鱼样本,采用残差指标分析方法和广义线性混合效应模型,分析了阿根廷滑柔鱼个体的体质量-胴长关系和体征变化的差异性。结果显示,阿根廷滑柔鱼样本的总体雌雄比例为1.25﹕1;雌性和雄性个体体型均以2014年的为最大,分别为(271.7±28.3)和(244.7±17.3) mm; 2012年和2013年样本的胴长差异性不显著,前者雌性和雄性胴长分别为(207.9±31.0)和(201.1±28.9) mm,后者雌性和雄性胴长分别为(213.6±18.0)和(203.5±19.0) mm。每个年份雌性和雄性个体的体质量与胴长呈显著的幂函数关系,且每个年份幂函数关系式的b值与匀速生长b=3存在差异。雌性和雄性个体体征的年间差异明显,同年度不同月份之间的体征亦存在显著差异(2012年雌性除外)。雌性和雄性个体的体征与胴长密切相关,胴长×月份作用对不同月份个体体征的影响效应具有一致性,...     

Seasonality of Mobbing Intensity in the Pinyon Jay

In the wild, pinyon jays (Gymnorhinus cyanocephalus) mob owls at all times of year, but our observations of wild birds suggested that the mobbing response was strongest during the breeding season. To test this, we placed four groups of five wild caught adult pinyon jays in environmental chambers during late autumn when their testes were regressed. These birds received photoperiods of 12, 12, 13 and 14 h for 30 days prior to being exposed singly to a live great horned owl (Bubo virginianus). Three groups of five birds were maintained under natural photoperiods in outdoor aviaries and were tested with the owl in Aug., Sep. and Nov. Birds on long artificial photoperiods mobbed more strongly than birds exposed to shorter photoperiods. The jays under natural photoperiods showed the opposite response: those tested in November mobbed significantly more strongly than birds tested in August. Jays with the weakest mobbing responses were molting, and those with the strongest responses seemed to be closest to reproductive readiness. There was no correlation between gonad size and mobbing intensity, but our results suggest a strong relationship between reproductive readiness and mobbing intensity in pinyon jays.     

内蒙古阴山北部农业区长爪沙鼠的种群动态及其调节的研究

内蒙古自治区阴山以北,通称后山地区,是重要的粮产区之一,但农业鼠害严重。如四子王旗,1961年受鼠害面积达54万6千余亩,严重减产者达25％以上。为害鼠种有长爪沙鼠(Meriones unguiculatus Milne-Edwards)和黄鼠(Citellus dauricusmongolicus Milne-Edwards),其中以长爪沙鼠为害严重。 长爪沙鼠是一种数量变幅大的群居鼠类。有关长爪沙鼠生态学及其对农业的危害,曾有过一些报道(夏武平、王文滨1956;何平均、丁建兴1957;赵肯堂1960),但系统地研究其种群动态的,尚不多见。 1964年至1969年,我们以内蒙四子王旗农区为工作点,较长期地研究了长爪沙鼠的种群动态和数量变动的调节。本文着重论述与种群变动有关的几个因素。     

SPERM COMPETITION SELECTS BEYOND RELATIVE TESTES SIZE IN BIRDS

Sperm morphology varies considerably across taxa, and postcopulatory sexual selection is thought to be one of the main forces responsible for this diversity. Several studies have investigated the effects of the variation in sperm design on sperm function, but the consequences of variation in sperm design on testis morphology have been overlooked. Testes size or architecture may determine the size of the sperm they produce, and selection for longer sperm may require concomitant adaptations in the testes. Relative testes size differs greatly between species and is often used as an index of sperm competition, but little is known about whether larger testes have more sperm-producing tissue or produce sperm at a faster rate. Using a comparative approach in New World Blackbirds (Icteridae), we found (1) a strong link between testis histology and sperm length, suggesting selection on testis architecture through selection on sperm size, and (2) that species under intense sperm competition had a greater proportion of sperm-producing tissue within their testes. These results support the prediction that sperm competition fosters adaptations in reproductive organs that extend beyond testes size, and raise questions about the trade-offs influencing reproductive investment.     

羌塘雪兔子繁殖特征及资源分配的海拔差异

植物种群的生殖特性和资源配置策略是植物生活史研究的重要内容之一,对于理解和预测植被结构和全球变化过程中的适应策略至关重要。该文以青藏高原特有风毛菊属植物羌塘雪兔子(Saussurea wellbyi)为试验材料,分析6个海拔梯度18个居群的花期繁殖特征的变化,并用异速生长模型分析资源投入及资源分配的个体大小依赖关系。结果显示:(1)个体大小、繁殖器官生物量、营养器官生物量、管状小花数目、雄蕊重量、花药长度及花粉数与海拔高度呈负相关(P<0.05),管状小花重量、雌蕊重量、花丝长度及花柱长度与海拔高度呈正相关(P<0.01);(2)营养分配与海拔高度呈负相关(P<0.01),繁殖分配与海拔高度呈正相关(P<0.01);(3)管状小花的数量与重量(P<0.05)、雌蕊重量与雄蕊重量(P<0.01)、花丝长度与花药长度(P<0.01)、花丝长度与花粉数(P<0.01)之间均存在权衡关系;(4)资源投入及资源分配在不同海拔间与个体大小都呈显著正相关(P<0.05),且截距在海拔间差异极显著(P<0.01)。综合分析认为:羌塘雪兔子在不同海拔下的繁殖特征以及大小依赖的资源投入和资源分配模式是羌塘雪兔子与其所处的高山环境长期适应和进化的结果。     

Social and seasonal influences on reproductive biology in male moustached tamarins (Saguinus mystax)

In several primate taxa there is evidence that the social and physical environment can exert a significant effect on reproductive behavior and biology. In this paper we examine social and physiological factors influencing group composition and reproduction in free-ranging moustached tamarin monkeys (Saguinus mystax mystax). This species is characterized by cooperative care of the young and a breeding system that includes both polyandrous and polygyandrous matings. Body measurements collected on adult males residing in multimale groups indicate marked within-group differences in testes volume. In 12 of 17 groups examined, testes volume of at least two resident adult males differed by 21–174%. Among these males, testes volume was not correlated with either body weight or adult age class. We also examine whether factors such as time of year had an effect on reproductive condition. An analysis of body measurements of 128 adult male and 127 adult female moustached tamarins, wild-trapped and released in northeastern Peru, indicates cyclic changes in genital size. For males, mean monthly testes volume in July (712 mm³) was twice that recorded in June (351 mm³). Females exhibited a similar pattern. Although endocrine information on intra- and intersexual social effects on fertility are unavailable for S. mystax, given the high degree of social cooperation and lack of overt aggression among adult male group members, we offer the possibility that resident male moustached tamarins compete for access to the groups' lone breeding female through socially induced reproductive suppression and sperm competition. © 1996 Wiley-Liss, Inc.