Plasticity in juvenile hormone in male burying beetles during breeding: physiological consequences of the loss of a mate

Burying beetles, Nicrophorus orbicollis, have facultative biparental care. They bury and prepare small vertebrate carcasses that provide food for their young. Here we establish the juvenile hormone (JH) profiles of paired females, paired males and single males and investigate some of the environmental and social factors that may affect these profiles. Before larvae hatch JH profiles of paired males and females were similar. However, after larvae hatch and during brood care, JH titers of females were very high and those of single males were significantly higher than those of paired males. We tested the hypothesis that higher JH was a response to the need for increased parental care by manipulating brood size. Although JH titers of single males caring for small versus large broods were not significantly different, when comparing JH titers and larval growth (a measure of parental effort), a significant positive correlation emerged. In contrast, we found that food quality had no effect on JH levels suggesting that increased feeding by males and females after carcass discovery cannot explain the elevation of JH. The regulation of JH in male burying beetles appears thus to be dependent on the presence of a mate and on critical stimuli from young.     

提高实验猴繁殖率的综合措施

实验猴繁殖率的高低直接影响实验猴养殖企业的经济效益。本文借鉴本中心多年实验猴繁育经验,总结了一套较为完备的提高实验猴繁殖率的措施,内容涵盖实验猴繁殖特性、种公猴选种、繁殖猴分群及梯度饲养、孕猴用药、母猴产后护理、仔猴补饲及断奶、繁殖猴饲料搭配等各方面。这些措施应用于实践后,实验猴繁殖率可保持在较高水平并逐年提高。我们认为这些措施可在其它实验猴养殖企业推广应用。     

Reproductive skew theory unified: The general bordered tug-of-war model

Reproductive skew has been identified as a major dimension along which animal societies vary. Two major kinds of reproductive skew models are transactional models, which explain the distribution of reproduction within animal societies as the result of reproductive payments exchanged among group members with differential leverage, and tug-of-war models, in which the reproductive shares are determined by costly ‘tugs-of-war’. These two models have recently been synthesized to yield the mutual-pay, bordered tug-of-war model. In this paper, we extend the latter, show its evolutionary stability, and demonstrate that the generalized model yields four sub-models, namely the mutual-pay, alpha-pay, beta-pay, and pure tug-of-war. The alpha-pay sub-model turns out to closely resemble the original “concessions” transactional skew model, and the beta-pay sub-model turns out to have properties similar to the “restraint” transactional skew model. Thus, the general model unifies the four major models of reproductive skew and is rich in its predictions, as each sub-model exhibits different qualitative and quantitative relationships between reproductive skew or intra-group conflict and the ecological and genetic factors that determine skew and conflict. The conditions favoring transitions among these sub-models also are precisely predicted by the general model. The general model accommodates data from acorn woodpeckers and primitively eusocial bees potentially can account for many of the highly varied empirical findings on reproductive skew. We suggest further research that focuses on (1) determining which model is suitable for certain species and (2) understanding why and how various social animals resolve their breeding conflict by different conflict resolution mechanisms.     

Brain aromatase mRNA expression in two populations of the peacock blenny Salaria pavo with divergent mating systems

Aromatase, the key enzyme in the conversion of androgens to estrogens, regulates the availability of these hormones in tissues and controls many physiological and behavioral processes. In fish and other vertebrates, the regulation of aromatase expression in the brain has been implicated in the modulation of male sexual and aggressive behaviors. Here, the pattern of mRNA expression of the brain aromatase isoform (encoded by the CYP19A2 gene also referred as CYP19b) was quantified at the peak of spawning season in brain macroareas from males and females of the blenny Salaria pavo originated from two populations displaying male alternative reproductive tactics but differing in their mating systems. In Trieste (Adriatic) nesting males aggressively defend nests and take the initiative in courtship and perform sexual displays more often than females while in Ria Formosa (Southern Portugal) the pattern is reversed as a result of shortage of appropriate nesting sites. Nesting males from Ria Formosa had overall higher levels of brain aromatase mRNA expression than nesting males from Trieste, suggesting a higher brain estrogen synthesis in these males. Since in some fish species exogenous estradiol administration has been shown to decrease sexual and agonistic behaviors, the higher levels of brain aromatase in Ria Formosa nesting males may explain their reduced expression of sexual and aggressive displays when compared with nesting males from Trieste. Alternatively, the higher brain aromatase levels in nesting males from Ria Formosa could be a mechanism to decrease the putative androgen-induced activation of aggressive and sexual displays by reducing the local availability of androgens through their metabolization into estrogens. Although females and parasitic female-like males also differ in their displays between populations, the interpopulational pattern of brain aromatase mRNA expression was similar, suggesting that other neuroendocrine agents mediate the expression of female and female-like behaviors. In conclusion, brain aromatase availability seems like a probable mechanism to regulate the effects of steroids on the brain circuits underlying the expression of sexual and agonistic displays in S. pavo.     

Dynamics of social and energetic stress in wild female chimpanzees

Stress hormone measurements can reinforce and refine hypotheses about the costs of particular contexts or behaviors in wild animals. For social species, this is complicated because potential stressors may come from the physical environment, social environment, or some combination of both, while the stress response itself is generalized. Here, we present a multivariate examination of urinary cortisol dynamics over 6 years in the lives of wild female chimpanzees in the Kanyawara community of Kibale National Park, Uganda. We hypothesized that chimpanzee socioecology provides strong indications of both energetic and social stress to females, but that the salience of these stressors might vary over a female's life history in accordance with their changing reproductive costs and social interactions. Using linear mixed models, we found that urinary cortisol levels increased significantly with age but were also elevated in young immigrants to the community. Across reproductive states, cycling, non-estrous females had relatively low cortisol compared to lactating, estrous, or pregnant females. Aggression from males led to higher cortisol levels among estrous females, frequent targets of aggressive sexual coercion. In contrast, energetic stress was most salient to lactating females, who experienced higher cortisol during months of low fruit consumption. Low dominance rank was associated with increased cortisol, particularly during the energetically demanding period of lactation. The effects of female conflict were felt widely, even among those who were the primary aggressors, providing further evidence that long-term resource competition, while apparently muted, exerts a far-reaching impact on the lives of chimpanzee females.     

Energetic challenges unmask the role of ovarian hormones in orchestrating ingestive and sex behaviors

Effects of ovarian hormones on sex and ingestive behavior are well studied, and yet, their role in diverting attention from food to sex has not been examined directly, possibly because these functions are masked under conditions of excessive food abundance typical of the laboratory. Female Syrian hamsters were either fed ad libitum or food-restricted to 75% of their ad libitum intake for 8 days and then tested every day of the estrous cycle for their preference for males versus food, food hoarding and food intake in an apparatus designed to mimic aspects of their natural habitat. The food-restricted, but not the fed females, varied significantly over the estrous cycle in appetitive behaviors, which included their preference for males versus food and in the amount of food hoarded, with low food hoarding and high male preference on the night of ovulation. In contrast, there were no significant differences between restricted and ad libitum-fed females in the consummatory behaviors, namely, food intake or lordosis duration. In ovariectomized females, estradiol plus progesterone treatment delayed food restriction-stimulated hoarding and hastened feeding-inhibited hoarding without affecting food intake or lordosis duration. In summary, energy restriction and the presence of males unmasked an effect that was obscured in the normal laboratory conditions characterized by isolation and an over abundance of readily available food. These results are consistent with the idea that ovarian hormones orchestrate appetites for food and sex to optimize reproductive success under fluctuating energetic conditions.     

Developmental regulation of protein kinase A expression and activity in Schistosoma mansoni

cAMP-dependent protein kinases (PKAs) are the main transducers of cAMP signalling in eukaryotic cells. Recently we reported the identification and characterisation of a PKA catalytic subunit (SmPKA-C) in Schistosoma mansoni that is required for adult schistosome viability in vitro. To gain further insights into the role of SmPKA-C in biological processes during the schistosome life cycle, we undertook a quantitative analysis of SmPKA-C mRNA expression in different life cycle stages. Our data shows that SmPKA-C mRNA expression is developmentally regulated, with the highest levels of expression in cercariae and adult female worms. To evaluate the biological role of SmPKA-C in these developmental stages, cercariae and adult worms were treated with various concentrations of PKA inhibitors. Treatment of cercariae with H-89 or PKI 14-22 amide resulted in loss of viability suggesting that, as in adults, PKA is an essential enzyme activity in this infectious larval stage. In adult worms, in vitro exposure to sub-lethal concentrations of H-89 or PKI 14-22 amide resulted in inhibition of egg production in a dose-dependent manner. Furthermore, using a murine model of schistosome infection where S. mansoni fecundity is impaired, we show that reduced rates of egg production in vivo correlate with significant reductions in SmPKA-C mRNA expression and PKA activity. Finally, restoration of parasite egg production in vivo also resulted in normalisation of SmPKA-C mRNA expression and PKA activity. Taken together, our data suggest that PKA signalling is required for cercarial viability and may play a specific role in the reproductive activity of adult worms.     

Lack of evidence on hybrid swarm in the sympatric population of Pinus mugo and P. sylvestris

Natural hybridisation between the taxa from Pinus mugo complex and P. sylvestris was postulated in several sympatric populations of the species in Europe. However, due to the absence of precise methods for identification of hybrid seeds and hybrid trees, the frequency of hybridisation and its influence on the genetic structure of relict P. mugo populations has not been clarified so far. In the present study, the species-specific chloroplast DNA (cpDNA) marker and isozymes were applied to test the hybridisation hypothesis in a postulated hybrid swarm population of the species from “Bór na Czerwonem” reserve at the northern foothills of Tatra Mts., Poland. The cpDNA marker was used to identify hybrids within two groups of polycormic (multi-stemmed) and monocormic (single-stemmed) pines from this population. Allelic frequencies at isozyme loci from both groups were compared to frequencies found in allopatric populations of the species. Additionally, cpDNA haplotypes of seedlings derived from open pollinated seeds were studied to detect the possibility of successful cross-pollination. The mixture of seedlings with P. sylvestris and P. mugo cpDNA haplotypes was derived from one parental tree that indicates hybridisation. However, all the mature polycormic pines had cpDNA haplotypes species specific to P. mugo and the isozyme frequencies were similar to frequencies found in three allopatric populations of P. mugo from Tatra Mts. (mean genetic distance, Dn=.027). The differences were much larger in comparisons with monocormic pines from this area (Dn=.085) and two P. sylvestris samples from distant allopatric populations (Dn=.077). Nearly all monocormic pines had cpDNA species specific to P. sylvestris and isozyme frequencies similar to other populations of this species (mean Dn=.004). Only one P. sylvestris-like monocormic tree had cpDNA of P. mugo and can be considered as a hybrid. The results do not provide evidence supporting the hybrid swarm hypothesis. Rather, the results suggest that mature hybrids have a low frequency within this population and (rare) hybridisation is not reciprocal but unidirectional with P. mugo as pollen donor.     

Secular Trends of Reproductive Indices in Chuvashian Women

In the present cross-sectional study of the Chuvashian rural population, we examined the secular trends of age at menarche, the age at menopause, the reproductive period, and the age of the first marriage of Chuvashian women. The cohort included 745 women aged 18–90 years; age at menarche (N = 653) ranging from 10 to 24 years (mean 15.42 ± 2.11). Data regarding menopausal age was obtained from 316 women born between 1920 and 1950 (mean 48.5 ± 4.6). Statistical analyses included the maximum likelihood estimation and a Whiskers plot. Women born during the second through the fourth decade of the 20th century showed increasing mean values of age at menarche from 15.4 (second decade) up to 16.5 (fourth decade) and after that a decrease of the mean values to 14.0 (ninth decade). The mean values of menopausal age increased from 47.0 (women born from 1920 to 1925) to 49.3 (born from 1945 to 1950). Age at first marriage showed a trend of decreasing age. Our study demonstrated secular trends of age at menarche in Chuvashian women who had matured after World War II and also confirmed secular trends of increased age at menopause and the duration of the reproductive period. Women, whose maturation was during or immediately after World War II, showed a higher age at menarche and a higher dispersion of age at menopause.