Sex differences in leadership during group movement in mantled howler monkeys (Alouatta palliata)

Benefits of group life depend in large part on whether animals remain cohesive, which often requires collective decisions about where and when to move. During a group movement, the leader may be considered as the individual occupying the vanguard position of the group progression, when its movement evokes following by other group members. In nondespotic societies, individuals with greater incentives to move frequently are leaders. During 15 months of observations (1,712 contact hours), we investigated two mantled howler monkey (Alouatta palliata) groups at La Flor de Catemaco (Los Tuxtlas, Mexico) to examine whether sex and female reproductive state influenced leadership likelihood in two contexts: movements toward feeding trees; movements associated with loud calls, a group-defense behavior used by males of this genus. Females led and occupied forward positions during group movements toward feeding trees more often than adult males. Adult females led these movements more frequently when they were gestating than when they were lactating or cycling. There were no differences between sexes in the leadership of group movements associated with loud calls. Leadership by gestating females is perhaps the result of their higher nutritional/energetic needs when compared with cycling females, and of their greater mobility when compared with lactating females carrying dependent offspring. Female leadership during movements toward feeding trees may be a mechanism to optimize access to food resources in mantled howler monkeys.     

Aggressive behavior of adult meadow voles (Microtus pennsylvanicus) towards young

Summary Field evidence indicates that adult microtines, especially females, may be a major cause of poor juvenile survival and this may be instrumental in their population regulation. This suggests that males and females behave differently towards young animals. To examine how adult males, nonlactating females, and lactating females behave towards strange young, I introduced young animals into the home cage of the adults. Lactating females were most aggressive towards young; most males investigated them; most nonlactating females ignored them. However, discriminant function analysis indicated a great deal of overlap in the behavior of the classes. None of the classes behaved differently towards young of either sex. Females did not vary their behavior during lactation. Behavior varied among lactating females, with 55% showing little aggression and 20% showing a great deal. Most lactating females showed similar behavior in each of their bouts: docile females remained docile, aggressive females remained aggressive. I conclude that lactating females are most aggressive towards strange young. These results are consistent with the field evidence, which suggests that adult females depress juvenile survival and recruitment and that the main culprits are breeding females.     

Immunocytochemical localization of renin in the submandibular gland of the mouse during postnatal development.

The localization of renin in the developing mouse submandibular gland was studied immunocytochemically using the unlabelled antibody-enzyme method of Sternberger ('74). Bouin-fixed submandibular glands of mice of both sexes were examined at 5-day-intervals from birth (day 0) to 50 days of age. At all stages studied, only granular convoluted tubule (GCT) cells stained immunocytochemically for renin; such cells were first seen in glands of 30-day-old males and of 30-day-old females. The size and number of renin-containing GCT cells increased rapidly in males, attaining adult status by 50 days of age. In females, differentiation of GCT cells immunoreactive for renin was slower and less regular than in males, and at 50 days of age the GCT segment had not yet reached adult conditions with respect to the distribution of renin. Renin appears in GCT cells at later ages than other GCT cell products (e.g., EGF and amylase), suggesting the existence of independent developmental control for the expression of various biologically active substances in the GCTs.     

Reproductive performance of wild boar females in Portugal

Reproductive tracts of 214 female wild boars collected in Central Portugal between October and February over the period 1997 to 2001 were examined. From this material, we were able to determine reproductive phenology (conception and birth periods) as well as age and weight of sows at puberty, ovulation rates of adults, foetal sex ratio, levels of intrauterine mortality, final litter size and postnatal mortality. Differences between year, region, age and body weight were analysed. A total of 66.8% of the females examined were gestating or lactating and 96.3% of these weighed >40 kg. The highest proportions of pregnant sows were found in the adult age/weight classes (74%). None of the juvenile females (1 year old and younger) were lactating and only 7% was pregnant. The average number of foetuses/female (4.1 ± 1.2SD) and that of corpora lutea per female (4.6 ± 1.7SD) increased from lighter and younger to heavier and older wild sows. Foetal sex ratio was biased towards males (1.3:1). Observed intrauterine mortality rate (9.7%) and postnatal mortality (6.3%) were among the lowest recorded in European wild boar populations. The productivity rate of the Central Portuguese wild boar population was calculated as 1.1 young per individual in the population. Conception and birth periods did not differ significantly between the considered 4 years. Birth synchronisation was pronounced in all the years, with a peak of births occurring in March.     

Androgen regulation of the cellular Distribution of the true tissue kallikrein mK1 in the submandibular gland of the mouse.

The kallikrein gene family encodes for at least four different proteases in the mouse submandibular gland (SMG): mK1 (true tissue kallikrein), mK9, mK13, and mK22. These enzymes and many other biologically active proteins are synthesized by the granular convoluted tubule (GCT), a specialized segment of the SMG duct system. The GCT is under multihormonal regulation by androgens, thyroid hormones, and adrenocortical hormones. Androgens suppress synthesis of mK1 in the SMG but enhance expression of the other three kallikreins. We prepared an antibody with limited immunoreactivity for mK1 and used it to examine the effects of androgen status on the distribution of this isozyme in the SMGs of developing and mature mice by immunoperoxidase staining for the light microscope and immunogold labeling for the electron microscope. In prepubertal mice, every immature GCT cell contains mK1, confined to an accumulation of small granules in the subluminal cytoplasm. In mature mice, not every GCT cell contains mK1, and in those cells that do there is considerable intergranular variation in the intensity of staining for mK1. GCT cells containing mK1 are much more abundant in the glands of females than of males, resulting in a peculiar sexually dimorphic mosaic distribution of this isozyme in the mature SMG. Castration of adult males increases the number of GCT cells expressing mK1. Administration of androgen to intact or castrated males or to intact females reduces the number of cells staining for mK1. In all cases, immunogold labeling for mK1 is confined to secretory granules. No fine structural differences were noted between cells that were positively or negatively stained for mK1. Therefore, although GCT cells appear to be composed of a uniform population of cells on the basis of morphology alone, they are not homogeneous in their content of secretory proteins. These results indicate that androgen regulation of GCT cells is more complex than has been appreciated to date.     

Harris lines in the prehispanic population of Gran Canaria (Canary Islands)

Harris lines were assessed in 194 right tibiae of prehispanic inhabitants of Gran Canaria, belonging to 52 adult females and 123 adult males. No Harris lines were detected in 45 (23%) of the adult individuals (13 females (25%) and 26 males (21%), these differences being not statistically significant. Female tibiae showed a slightly lower mean number of Harris lines at the distal end than male ones (1,692±1.681 in females vs 1.91±1.825 in males). Ages at which Harris lines were formed showed two peaks, a major one at the age of 1 year, and another between 15 and 16 years in males and between 11–12 and 14–15 years in females. Harris lines were more frequently observed at the distal than at the proximal end of the bone. The relative low number of lines detected in our population when compared with the high prevalence of osteoporosis among the adult population of this island is striking.     

Neuroanatomical distribution of aromatase mRNA in the rat brain: indications of regional regulation

Aromatase, the enzyme responsible for the conversion of testosterone to estradiol, is found in the rat brain and is present in regions of the preoptic area, hypothalamus, and limbic system. Gonadal steroid hormones regulate aromatase activity levels in many brain regions, but not all. Using in situ hybridization, we examined the distribution of aromatase mRNA in the adult male forebrain, as well as the levels of aromatase mRNA in the brains of males and females, and the regulation by gonadal steroid hormones. In the adult male, many heavily labelled cells were found in the encapsulated bed nucleus of the stria terminalis (BNST), the medial preoptic nucleus (MPN), the ventro-medial nucleus (VMN), the medial amygdala (mAMY) and the cortical amygdala (CoAMY). The regional distribution of aromatase mRNA was similar in males and females, but males tended to have a greater number of aromatase mRNA-expressing cells in each region compared to females. Aromatase mRNA levels in the BNST, MPN, VMN and mAMY tended to be lower in castrated males than in intact males, whereas aromatase mRNA levels were unaltered by castration in the CoAMY. Further analysis of individual cells expressing aromatase mRNA suggests that aromatase mRNA may be regulated by steroid hormones differentially in specific populations of cells in regions where enzyme activity levels are steroid-hormone-dependent.     

Immunocytochemical localization of epidermal growth factor during the postnatal development of the submandibular gland of the mouse.

The time of appearance and the pattern of localization of epidermal growth factor (EGF) in submandibular glands of mice was studied during postnatal development immunocytochemically. EGF was first detectable in the granular convoluted tubule (GCT) cells in the glands of males at 20 days of age and of females at 30 days of age. Development of GCT cells containing EGF was rapid in males, approaching adult conditions by 45 days of age. In females EGF- containing GCTs developed more slowly and irregularly, and did not reach adult status by 45 days of age. It is concluded that EGF is restricted during postnatal development to the GCT cells, and that these cells and the distribution of EGF are represented dimorphically from their first appearance in the submandibular glands of both sexes.     

Effect of the stage of the reproductive cycle on vocalization and behaviour in female bank voles

Females of several species of rodents are known to emit audible and ultrasonic sounds during same-sex encounters. There is very little information about factors affecting this vocalization. The present study was undertaken to investigate the effect of the stage of the reproductive cycle on vocalization and behaviour of adult bank vole females during various same-sex encounters. Pregnancy and lactation were studied as important phases of female life. The possible role of ovarian hormones in the emission of acoustic signals was also investigated as these hormones are known to be important in the regulation of other female social behaviour. The behaviour and vocalization of sexually naive, ovariectomized, pregnant and lactating females were studied using 10-min confrontation tests. The results demonstrate that the behaviour displayed and the emission of sounds in female–female bank vole encounters depend on the phase of reproductive cycle. Ultrasounds are produced more often by sexually naive and ovariectomized females which present mainly non-aggressive behaviour than by more aggressive lactating females. Audible sounds are emitted only occasionally by naive and by ovariectomized females but pregnant and especially lactating females emitted such calls more often, with shorter latencies and for longer than the unmated groups. Ultrasonic vocalization therefore seems to be related to non-aggressive behaviour and audible vocalization to aggression.     

Distribution in a density gradient of human erythrocytes: sex-related differences

Differences in erythrocyte distribution on Ficoll-Sodium Metrizoate discontinuous density gradient were evaluated between adult males and females. Testosterone and androstenedione plasma levels were tested in males, oestradiol, progesterone and prolactin in both males and females. Female group showed a much higher proportion of lighter younger erythrocytes than males, while males showed higher proportion of denser older cells. Positive correlation was found between young cell percent and oestradiol level, both in males and females, but no correlation was found with androgen hormones.     

Sex differences and hormone influences on tyrosine hydroxylase immunoreactive cells in the leopard frog

We examined sex differences in tyrosine hydroxylase immunoreactive (TH-ir) cell populations in the preoptic area (POA), suprachiasmatic nucleus (SCN), posterior tuberculum (TP), and caudal hypothalamus (Hy) in the leopard frog (Rana pipiens), in addition to the effects of natural variation in sex steroid hormones on these same populations in both sexes. All four of these populations have been shown to be dopaminergic. Gonadal sex, androgens, and estrogen all influenced TH-ir cell numbers, but in a complicated pattern of interactions. After factoring out the effects of sex steroids by multiple regression, TH-ir cell numbers in all four areas differed between the sexes, with males having a greater number of TH-ir cells. The influence of androgens and estrogen differed by region and sex of the animals. Androgens were the main influence on TH-ir cell numbers in the POA and SCN. Plasma androgen concentrations were positively correlated with TH-ir cell numbers in both areas in males. In females, androgen concentration was negatively correlated with TH-ir cell numbers in the POA; there was no significant relationship in the SCN in females. In the more caudal populations, estrogen (E2) levels were positively correlated with TH-ir cell numbers in the TP of both males and females. In the caudal hypothalamus, E2 levels were positively correlated with TH-ir cell numbers in females, but there was no significant correlation in males. The results indicate that gonadal sex imposes a baseline sex difference in the four TH-ir (dopamine) populations, resulting in a higher number of such cells in males. Individual and sex-linked differences in gonadal steroid hormones lead to variation around this baseline condition, with androgens having a greater influence on rostral populations and estrogen on caudal populations. Last, an individual's gonadal sex determines the effect that androgens and estrogen have on each population.     

Fine Structure of the Pars Distalis of the Pituitary Gland in the Female Mink,Mustela vison

Pituitary glands of intact and experimental adult females of mink, Mustela vison, were examined by electron microscopy. Conventional methods involving removal of endocrine glands (ovaries and adrenals), administration of radioactive isotope, ¹³¹I, blocking agents (thiouracil and metopirone) and hormones (thyroxine, hydrocortisone, thyrotropin and luteinizing hormone releasing hormones) were employed. Five categories of granular cells were distinguished both by their ultrastructural characteristics and qualitative changes throughout the year and following different treatments. The cell types are described and their functions discussed. From conventional electron microscopical studies it proved difficult to draw any satisfactory conclusions about the gonadotropic cells. Further investigation by means of immunocytochemistry and radioimmunoassay techniques is required to determine, whether the presumptive gonadotropic cell type produces both FSH and ICSH or only one of these hormones. Morphologically two types of agranular cells were identified. Their morphological inter-relationship and function are discussed briefly.     

Communal Nesting among Genetically Similar House Mice

From March to October 1986, 35 house mice, Mus domesticus, were fitted with radio-transmitters and tracked in and around a Colorado feed shed for an average of 5 (range 2 to 17) days. 5 of 36 simultaneously tracked pairs of lactating females used identical nesting sites. Genotypic similarity at 5 enzyme loci, assayed from biopsies of blood and toes, indicated that these females were more genetically alike than would be expected if pairing occurred randomly among females. We posit that female house mice recognize and preferentially form communal nests with close relatives. Aside from the communally nesting females, minimal overlap occurred among home ranges of lactating females. Only 4 of 10 adult male home ranges appreciably overlapped female home ranges. The home ranges of these 4 males overlapped less than the other adult male home ranges suggesting that males defend one or more females for access to mating. The possibility that communally nesting females are nursing each other's pups is discussed.     

Some endocrine traits of transgenic rabbits. I. Changes in plasma and milk hormones

The aim of these studies was to compare some endocrine and non-endocrine characteristics of transgenic (carrying mammary gland-specific mWAP-hFVIII gene construct) and non-transgenic rabbits. The concentrations of corticosterone, progesterone, testosterone, estradiol, insulin-like growth factor I (IGF-I) and human factor VIII (hFVIII) in the blood plasma of adult females (9 months of age, third generation transgenic animals), adult males, and young females (1-2 months of age, fourth generation of transgenic animals), as well as in the milk of lactating adult females, were analyzed by using RIA. In addition, litter size and body mass of pups born by transgenic and non-transgenic females from the third generation were compared. Transgenic animals were compared with their non-transgenic siblings (the same genetic and epigenetic background). Transgenesis did not influence plasma hFVIII, but significantly increased corticosterone (in all animals), reduced IGF-I (in adult males and females), testosterone and estradiol, (in young females) and altered progesterone (increase in adult males and decrease in adult females) concentrations in blood plasma. In addition, transgenic females had higher milk concentrations of testosterone, but not progesterone or IGF-I than their non-transgenic sisters. These endocrine changes were not associated with changes in litter size. Transgenic male (but not female) pups have smaller body mass than control animals. These observations demonstrate the influence of transgenesis per se on the animal growth and endocrine system (secretion of reproductive and stress steroid hormones as well as growth factors) over four generations.     

The growth of the freshwater crayfish A ustropotamobius pallipes in Northumbria

SUMMARY. Growth increments, moult frequency and growth rates of individuals in a population of the freshwater crayfish Austropotamobius pallipes were followed for a period of 3 years during a mark-recapture study. There was an inverse relationship between body size and the growth increment relative to body size. The absolute increment increased from the juvenile to the young adult stage and thereafter declined with increasing body size.
Differences between the adult male, reproductive female, non-reproductive female and juvenile subpopulations in the size of growth increments are reported and growth increments during the two major moult periods of each year are compared. The effect of the endoparasite Thelohania contejeani and of chela regeneration was to reduce slightly the growth increments.
Instantaneous growth rates declined throughout life in both sexes, but adult males maintained higher growth rates than adult females, particularly in the largest size class studied. The effect of reproduction on growth appeared to be most severe in the smallest breeding females. Males maintained the tendency to moult twice annually to a larger size than females. A simplified construction of the relationship between size and age in the population is presented for each sex. The oldest animals were estimated to be at least 11 years old.     

Seasonality of reproduction in the European badger Meles meles in south-west England

The reproductive cycle of male and female badgers in the south-west of England was studied by post-mortem examination of 1875 badgers collected in 1973–80. The sample was obtained by several methods and showed that animals obtained as road casualties were not representative of the total population samples. Active spermatogenesis was present throughout the year, and in some males aged 8–9 months. A few females first ovulated as yearlings but most primiparous females were adults. Births were in general confined to the early part of the year, but ovulations and matings also occurred at other times. Almost all (97%) adult females possessed corpora lutea. Unimplanted blastocysts were found in females for 11 months of the year (over 80% of adult females in July-November). Implanted embryos were found in only 32% of adults in January and February: the number of blastocysts per female and the number of implanted embryos per female were not significantly different, indicating that sows implanted all blastocysts or none. Foetal mortality was 36% and post-natal losses were estimated at 42% from the proportion of lactating females.     

哺乳期棕色田鼠对配偶的识别记忆

观察了分娩后哺乳雌性棕色田鼠（Microtus mandarinus）与配偶分离7d、14d、21d后对配偶与陌生雄鼠的行为反应。结果发现,在频次和持续时间上,与配偶分离7d、14d、21d的雌鼠对配偶的攻击行为显著低于陌生雄鼠（P〈0．05）;对配偶的嗅闻及友善行为显著高于陌生雄鼠（P〈0．05）。处于哺乳前、中、后期不同阶段的雌鼠对陌生雄鼠攻击水平没有显著性差异（P〉0．05）。这些结果说明,在整个哺乳期,雌鼠能够识别配偶,对配偶的记忆不因分离时间的增加而减弱,而且对陌生鼠的攻击水平不会因哺乳阶段的变化而变化,维持高水平的攻击可能与其较强的母性行为有关。     

Spleen size variations and reproduction in a Mediterranean population of wild boar (<Emphasis Type="Italic">Sus scrofa</Emphasis>)

We analysed spleen size variations of free-ranging wild boars from the west-central Iberian Peninsula during the hunting season (autumn and winter) in relation to the rut, the gestation effort and the attainment of sexual maturity by males and females. Females had larger spleens than males once they reached their sexual maturity. Individuals shot in winter had larger spleens than those shot in autumn, the start of the rutting period. In contrast to other reports, we found no influence of the reproductive status of adult females on their spleen sizes. Our findings may point to an influence of sex hormones, and possibly also stress hormones, and environmental factors on spleen development, mainly in adult and subadult males.     

Spontaneous or experimentally induced formation of a special zone in the adrenal cortex of the adult brush-tailed possum (Trichosurus vulpecula)

The cytology and ultrastructure of the hypertrophied special zone, which is formed spontaneously in the adrenal cortex of adult female brush-tailed possums (Trichosurus vulpecula), was compared to the adrenocortical tissue in adult males in which the special zone, normally absent, was induced following castration alone or by additional treatment with follicle-stimulating hormone (FSH). The special zone in females was situated between the zona fasciculata and the zona reticularis, the latter being a rudimentary zone in this species. Special zone tissue extended as a broad band parallel to and on one side of the adrenal medulla. In the luteal phase of the reproductive cycle, the special zone cells showed ultrastructural features commonly associated with steroidogenic tissues, with many mitochondria and compact masses of smooth endoplasmic reticulum. Cytoplasmic lipid inclusions were rarely observed. In lactating females, however, the special zone cells exhibited cytological and ultrastructural features suggestive of a transformation in their morphology broadly divided into two types of cells: (1) cells at the periphery of the special zone (closest to the zona fasciculata) showed variable quantities of lipid inclusions, mitochondria with dispersed cristae, and segregation of the smooth endoplasmic reticulum into compact masses; (2) cells within the more central regions showed an increasing abundance of lipid inclusions which in many cells became the dominant feature of the cytoplasm. These special zone cells contained very little smooth endoplasmic reticulum and their mitochondria contained few cristae together with amorphous granular material within the matrix. In castrated males, special zone tissue developed between the zona fasciculata and the zona reticularis, appearing initially as focal islands of cells (8 months postcastration) and later (11 months postcastration) expanding into a single zone, probably via the proliferation and differentiation of adjacent cells of the zona fasciculata and longitudinal growth of the special zone. Similar focal aggregations of special zone cells were induced after 14 days of FSH treatment given to 2-month castrated males. In all castrated and FSH-treated castrated males, the ultrastructure of special zone cells was similar to that of special zone cells in luteal-phase female possums. The findings suggest that the formation and cellular composition of the special zone is associated with changes in the pituitary-gonadal axis and that FSH plays a primary role in the differentiation of this tissue.     

Determinants of Affiliative Interactions between Adult Males and Lactating Females in Pigtail Macaques (Macaca nemestrina nemestrina)

In some species of Cercopithecine primates, unrelated adult males and females maintain affiliative relationships ('friendships') that are apparently unrelated to mating or parental care. This study investigated the occurrence of friendships in a captive group of pigtail macaques, and some of their possible determinants. Study subjects were six adult males and 15 adult females with their newborn infants. Females were focally observed for 2 h every week during the first 12 wk of lactation. With the exception of the fourth-ranking male, adult males showed little interest in initiating affiliative interactions with lactating females and their infants. Most episodes of contact and grooming were initiated by high-ranking females and directed to the alpha male. Because female grooming was not generally reciprocated by the alpha male, it is likely that females benefited from associating with him in terms of agonistic support or protection. Genetic data on paternity determination indicated that the fourth-ranking male, who displayed high levels of affiliation towards mother-infant dyads, sired most of the infants born in the group in the year prior to this study. Thus, whereas females may be interested in associating with males to obtain their support, some males may affiliate with females as a consequence of their previous mating relationships with them or to increase the chances of future mating success. Taken together, however, the findings of this study provide little evidence that adult males and lactating females maintain strong reciprocal bonds that may qualify as friendships.