Effects of castration and sex steroids on sexually dimorphic development of the mouse submandibular gland

The aims of this study were to characterize sexual dimorphism in the submandibular glands of young adult mice and to determine how sex differences arise during postnatal development. In the mouse submandibular glands, prominent sexual dimorphism was observed at 30 days of age, when the male gland was superior in both the relative occupied area (ROA) and the mitotic rate of the granular convoluted tubules (GCT) to those of the female. By neonatal castration, this sexual dimorphism was abolished, and the intraglandular structures of castrated males were similar to those of normal females. In castrated mice of both sexes, daily treatment with testosterone and 5 alpha-dihydrotestosterone for 10 days from 20 days induced only the ROA of the GCT to increase to the normal male levels but not those of the other three regions of the glands, the acini, intercalated ducts and excretory striated ducts. Testosterone responsiveness of the glands, considering both the glandular weight gain and the mitotic rate of the GCT, was significantly higher in castrated males than in castrated females. On the other hand, 17 beta-estradiol had no effect on the glands of castrated mice. Therefore, the present study suggests that the testicular hormones are responsible for the masculine development of GCT of the glands, but not the ovarian hormones, and that there is a sex difference in the responsiveness of the glands to testosterone, which is more effective in males than in females.     

Seasonal and social correlates of fecal testosterone and cortisol levels in wild male muriquis (Brachyteles arachnoides)

Fecal testosterone and cortisol levels were analyzed from six wild male muriquis (Brachyteles arachnoides) over a 19-month period at the Esta??o Biológica de Caratinga in Minas Gerais, Brazil, to investigate the hormonal correlates of seasonal sexual behavior and environmental conditions. Group mean testosterone levels based on weekly samples from the six males did not differ between copulatory and noncopulatory periods or between rainy and dry seasons. Cortisol levels did change with copulatory periods, and were significantly higher during the second dry season, when mating continued following an exceptionally heavy rainy season, than during the first dry season, when mating ceased. Males exhibited individual variation in the timing of their hormone shifts relative to their sexual activity, but neither hormone levels nor sexual activity were related to male age. Despite individual differences in the timing of testosterone fluctuations around the onset and offset of the copulatory season, all males exhibited elevated cortisol concentrations following a slight increase in testosterone at the beginning of the copulatory season. Both the lack of significant changes in testosterone levels with the onset of the rainy and copulatory season and the lack of prebreeding increases in cortisol may be related to the low levels of overt aggression displayed by male muriquis over access to mates.     

Seasonal diet composition of Fundulus lima (Cyprinodontiformes: Fundulidae) in two oasis systems of Baja California Sur, Mexico

Fundulus lima inhabits river drainage systems and is threatened after the introduction of cichlids in the area. To support conservation programs, the spatial and temporal variation of the diet composition of this endangered killifish, was determined in two oasis systems of Baja California Sur, Mexico (San Ignacio and La Purisima river drainages), during rainy and dry seasons. F. lima was captured by using passive and active capture techniques. A total of 192 stomach contents of F. lima was analyzed. The contribution of each prey item in the diet composition was quantified by means of the indices of occurrence frequency (% OF), numerical (% N) and volume (% V) percentages. The relative importance of each prey item was determined according to the percentage of the Relative Importance Index (% RII). The similarity of the diet was calculated between hydrological basins (populations combined by basin), seasons (rainy versus dry months), sexes and size classes, by using Schoener's resource overlap index. We used two ecological indices to determine the type of feeding strategy exhibited by the fish: (1) niche breadth of Levins and (2) proportional similarity of Feisinger. Sand was the most abundant item in the stomach content of killifishes from both drainages (39% and 47%, respectively). Diet composition was similar for both drainages (74%) as well as among their respective size classes; however, it was different between sexes. In both drainages, F. lima predated mainly on diatom algae, dipterous and trichopteran larvae, and fish scales during the dry season; while it preferred dipterous larvae, filamentous algae and ostracods in the rainy season. A feeding strategy of opportunist type was exhibited by F. lima during the rainy season, changing to specialist type during the dry season. This information will be the basis for future investigations related to the conservation of this endangered species and its habitat.     

Postnatal developmental changes in submandibular glands of rats and mice

The submandibular glands of mice and rats are not fully developed at birth. In early postnatal life, differentiation of acini takes place before that of granular convoluted tubule (GCT) cells. The latter develop from striated duct cells, and first appear in both species around 15 days of age. In mice their full development gets under way by 20 days of age and is rapid in males and slow in females, resulting in a clear sexual dimorphism in adults. In rats, GCT development is more protracted, and accelerates around 40 days of age, with no sexual dimorphism seen at any time. The course of postnatal development of several GCT cell products is correlated with the cytodifferentiation of these cells. Reliable data are available for the development of amylase, proteases (including kallikrein), renin, epidermal growth factor, and nerve growth factor. Preliminary information exists for a glucagon-like substance. Cytodifferentiation of GCT cells is under hormonal control. Androgens alone can not precociously induce GCT cells, but thyroid hormones can do so, acting either alone or synergistically with androgens.     

Ecology of the growth of Anolis nebulosus (Squamata: Dactyloidae) in a seasonal tropical environment in the Chamela region,Jalisco, Mexico

Juvenile growth rates are thought to be restricted by available food resources. In animals that grow throughout the year, such as tropical lizards, growth is therefore predicted to be faster during the rainy season. We test this prediction using a population of Anolis nebulosusby describing the growth trajectories of both sexes using nonlinear regression models, and we then correlate the growth rates of individuals with food available in the environment, precipitation, and temperature. The Von Bertalanffy model fits the growth rates of the females better, while the logistic‐by‐length model fits the males better. According to both models, the males grew faster than females, reaching slightly smaller sizes at adulthood. Males reached sexual maturity when 35 mm long, at an age of seven months, and females matured at 37 mm (SVL), taking nine months to reach this size. In 1989, juvenile males and females grew more in both seasons (rainy and dry) than adults; for 1990, there were no differences by season or between age classes. These results are interesting since in the 1989 and 1990 rainy seasons, practically the same orders of prey and the greatest abundance of prey available in the environment were registered. A possible explanation could be that predation was more intense in 1990 than in 1989. There is little evidence that food, temperature, and humidity affect growth rates of A. nebulosus, refuting our predictions. This is mainly due to the low variation in growth observed in 1990. Therefore we think that the growth of this species reflects a complex combination of ecological and genetic factors.     

垂叶榕榕小蜂群落及种间互作网络季节动态

群落中的物种相互作用构成了复杂的生态网络。有关物种的数量和组成的季节性动态变化已有较多的研究, 但是对于生态网络的动态变化知之甚少。揭示生态网络的动态变化对于理解群落的稳定性以及群落的动态变化过程和机理具有重要意义。本研究以垂叶榕(Ficus benjamina)榕小蜂群落为研究对象, 分别在西双版纳的干季和雨季采集了榕小蜂的种类和数量信息。比较了两个季节榕小蜂群落的动态变化以及共存网络的参数(例如网路直径、连接数、嵌套性和群落矩阵温度)变化。结果显示: 雨季榕果内传粉榕小蜂Eupristina koningsbergeri所占比例高于干季, 传粉榕小蜂的种群数量也高于干季, 而在干季非传粉榕小蜂的种类增加(干季15种小蜂, 雨季14种)。从榕树-传粉榕小蜂互利共生系统的适合度来看, 干季非传粉小蜂的增加对传粉榕小蜂和榕树的适合度是不利的。在干季, 共存网络物种间的连接数(干季0.95, 雨季0.47)多于雨季, 群落矩阵温度(干季23.24, 雨季2.64)也显著高于雨季。表明干季榕小蜂群落组成及种间关系较雨季更为复杂而多样, 高的矩阵温度暗示群落受到的干扰更大。     

Thelazia rhodesii (Desmarest, 1828) in cattle of Central Province, Zambia

Sanga cattle from Central Zambia were examined during the dry and the rainy seasons for the presence of the adult stage of eyeworm Thelazia rhodesii. Prevalences were recorded according to age/sex groups. The occurrence of ocular diseases was also noted. Differences between the total prevalences of infection with the parasite in the dry and rainy seasons were observed: respectively 3.1% and 26.6% of all cattle examined (p less than 0.001), which numbered 223 head in the dry season and 248 in the rainy season. In both seasons, adult males showed the highest prevalence and calves the lowest. In the dry season the parasite was found in two of the 23 males (8.7%) but in none of the 24 calves. During the rains, eight of the 22 adult males (36.4%), and two of 53 calves (3.8%) were parasitized (p less than 0.001). A comparison of the prevalences in the latter season between a group of cows sprayed weekly with a synthetic pyrethroid and an untreated group showed no significant difference between the two groups (p greater than 0.1). No correlation was found between T. rhodesii infection and the occurrence of eye lesions (p greater than 0.1). It is concluded that in traditionally managed Zambian cattle the infection is seasonal, is more frequent in adult male animals and is not associated with eye infections (i.e., pink-eye).     

大山雀身体大小的性二态及其季节变化

动物中普遍存在雌雄个体身体大小的性二态现象。了解近缘种之间身体大小性二态现象的差异，可为深入探讨身体大小性二态现象的潜在驱动机制提供证据。国外对欧亚大山雀（Parus major）的研究发现，其喙长、跗跖长、翅长等 6 项身体大小指标存在着明显的性二态，且喙长的性二态存在季节间差异。大山雀（P. cinereus）曾被作为欧亚大山雀的一个亚种，其形态和行为与欧亚大山雀存在着诸多相似之处。为探讨大山雀是否也存在身体大小性二态及季节性差异，本研究分析了 2018 至 2020 年间在河南董寨国家级自然保护区捕捉的 226 只（雌性 96 只和雄性 130 只）大山雀的喙长、头喙长、跗跖长、翅长、尾长和体长这 6 项体征指标的两性差异及其季节变化。结果显示，大山雀上述 6 项身体大小指标均存在不同程度的性二态现象，且雄性个体仅喙长与雌性的差异不显著，其余 5 项指标均显著大于雌性。此外，身体大小指标的两性差异不随季节显著变化，但两性的跗跖长在秋季均显著短于冬季和繁殖季，尾长在繁殖季均显著长于秋季和冬季。上述结果表明，大山雀身体大小的性二态及其季节性差异与欧亚大山雀并不完全相似。无论其身体大小存在性二态和季节变化的原因，还是其与欧亚大山雀在身体大小性二态模式上的差别，都有待今后进一步的研究。     

Stable isotopes complement focal individual observations and confirm dietary variability in reddish–gray mouse lemurs (Microcebus griseorufus) from southwestern Madagascar

We examine the ecology of reddish‐gray mouse lemurs from three habitats at Beza Mahafaly Special Reserve using focal follows and stable carbon and nitrogen isotope data. Focal observations indicate dietary differences among habitats as well as sexes and seasons. Both sexes consume more arthropods during the rainy season but overall, females consume more sugar‐rich exudates and fruit than males, and individuals from riparian forest consume fewer arthropods and more fruit than those in xeric or dry forest. We ask whether these observations are isotopically detectable. Isotope data support differences between seasons and sexes. Nitrogen isotope values are higher during the rainy season when lemurs consume more arthropods, and higher in males than females, particularly during the dry season. However, differences among populations inferred from focal observations are not fully supported. Lemurs from riparian forest have lower isotope values than those in xeric scrub, but isotope data suggest that lemurs from the dry forest eat the least animal matter and that focal observations overestimated dry forest arthropod consumption. Overall, our results suggest that observational and isotopic data are complementary. Isotope data can be obtained from a larger number of individuals and can quantify ingestion of animal matter, but they apparently cannot quantify the relative consumption of different sugar‐rich foods. Combined focal and isotope data provide valuable insight into the dietary constraints of reddish‐grey mouse lemurs, with implications for their vulnerability to future habitat change. Am J Phys Anthropol 155:77–90, 2014. © 2014 Wiley Periodicals, Inc.     

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.     

Year-round local movements of the japanese fluvial sculpin,Cottus pollux (large egg type), with special reference to the distribution of spawning nests

Year-round local movements of adult Japanese fluvial sculpin.Cottus pollux (large egg type), were investigated by a capture-mark-and-recapture method from July 1989 to July 1990 in the upper reaches of the Inabe River, central Japan. In the pre-breeding (July to January) and post-breeding seasons (June to July), the mean distance of movements in males and females was less than 20 m, and there was no apparent tendency to move into a particular channel-unit habitat, suggesting residential tendency in both sexes. In the breeding season (February to May), males tended to move into the raceways where most of the spawning nests were found, but females did not do likewise, indicating a sexual difference in movements in that season. Such sexual difference in movements was also confirmed by the records of individuals captured and recaptured more than three times: six (42.9%) of 14 males moved into the raceways in the breeding season, whereas only one (7.1%) of 14 females did so in that season. The reason behind this sexual difference in movements observed in the breeding season is discussed from the viewpoint of the patterns of spatial distribution between sexes during the pre-breeding and breeding seasons.     

The social organization of giraffes in Niger

The social organization of the last population of giraffes ( Giraffa camelopardalis ) in West Africa was studied between October 1996 and December 1997. Population size increased from 51 to 63 individuals during the study period. Groups were larger during the rainy season (mean group size 9.4) than during the dry season (mean group size 6; U = 4131; P < 0.01). Giraffes did not show strong preferential associations. Group types observed were similar to those expected on the assumption that associations are independent of sex and age. Inter-individual associations were low (mean simple ratio value = 0.1), with an individual associating with only half of its partners of the previous day. Young males interacted more frequently than other classes did. Agonistic interactions occurred mostly among males. Contact interactions (i.e. non-agonistic or sexual) occurred between both sexes and most age classes. Links between local communities, domestic animals, fauna and the environment suggest that environment and development cannot be dissociated in the sustainable exploitation of natural resources.     

The efficacy of performing field surveys during the dry and rainy seasons to estimate species richness and composition of local bat assemblages

Here we assessed the efficacy of performing field surveys during both dry and rainy seasons to estimate species richness and composition of phyllostomid bats in 12 sites of the Brazilian Atlantic Forest. Our goal was to elucidate two opposite scenarios. If bat species compositions differ between the dry and rainy seasons, then field surveys in both seasons will be considered complementary for estimating local bat assemblages. In contrast, if bat species compositions in the dry season are a nested subset of the species present in the rainy season, then field surveys in both seasons will be considered redundant. Our results showed that field surveys performed only during the rainy season exhibited the same efficacy in recording bat species as field surveys considering both dry and rainy seasons combined. Consequently, the rare species sampled in the rainy season contributed to the uniqueness of communities in terms of species composition. Considering that time, funding, and the number of field personnel available for work are important factors when determining the sampling effort in highly biodiverse regions like the tropics, our results can be useful in establishing protocols for research projects with limited resources aiming to create a comprehensive list of species.     

Reproductive seasonality of the detritivorous fish <Emphasis Type="Italic">Cyphocharax abramoides</Emphasis> (Kner, 1958) (Characiformes: Curimatidae) in flooded rivers of the eastern Amazon

The Lower Anapu River, Eastern Amazon, has a discrete flood pulse with narrow flooded areas due to the reduced influence of tides. In this environment, local precipitation might act as an important factor in the input of detritus, which can serve as a trigger for fish reproductive period. Therefore, this paper aims to determine the effects of local precipitation on the reproductive ecology of an abundant detritivorous fish in flooded rivers. Between May 2012 and April 2013, 886 specimens (471 females and 415 males) were captured monthly using gill nets. Individuals were measured, weighted, sexed, and the gonadal development stage was defined macroscopically and confirmed histologically. Sex ratio, length-weight relationship (LWR), condition factor (k), Gonadosomatic Index (GSI), relative frequency of maturity stages, and size at first gonadal maturity (L₅₀) were estimated and tested in relation to rainfall periods. There was no difference between the expected sex ratio (1:1), and both males and females showed polyphasic growth. The condition factor indicated higher values at the beginning of the rainy season and lower values during the dry season for both sexes. GSI and relative frequency of mature individuals indicated a long reproduction period with gonadal investment starting within the dry season until early in the rainy season for spawning within the rains. The L₅₀ value showed that males reach sexual maturity before females. Results indicated a reproductive pattern strongly influenced by rainfall, corroborating the importance of local precipitation for lacustrine environments.     

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.     

Species assemblages of cyclopoid Copepoda from Mantecal,Venezuela

A 14 year monitoring of species composition and abundance of cyclopoid copepods throughout the rainy and dry seasons in a flooded savanna at Mantecal, Apure State, Venezuela, is presented. Two characteristic habitats within these water bodies were selected: the open center of small ponds free of emergent vegetation and the surrounding flooded grassland. In total, 13 species were registered, all of which appeared in the flooded grassland and 11 of which occurred in the open water. Ten species were common for the two habitats during the dry season. The highest abundance was found in flooded grassland during the dry season. Eight species showed abundances greater than 1.0 individual per liter in flooded grassland during both seasons; 3 and 7 species were this abundant in the open water during rainy and dry seasons, respectively. Mesocyclops meridianus and Microcyclops varicans were the most abundant species in both habitats and seasons, while Thermocyclops decipiens was the dominant species during rainy season in open water. Principal component analysis indicates that the important species were positively correlated between them (sharing habitat and season).     

Composition, abundance and distribution of macrozooplankton in Culebra Bay, Gulf of Papagayo, Pacific coast of Costa Rica and its value as bioindicator of pollution

The abundance, distribution and composition of the macrozooplankton of Culebra Bay, Costa Rica (10 degrees 38' N - 85 degrees 40' W) were studied at four stations throughout the dry (February-May) and rainy (September-November) seasons of 2000. The samples were collected at two-week intervals using a 500 microm mesh net with a 0.5 m diameter opening. Copepods (23-31%) and ostracods (20-34%) were predominant throughout the year, followed by cladocerans (2.5-14%), zoea (6.6-9.5%), and siphonophores (2.5-7.2%). High densities of zooplankton were obtained in February and March with peak abundance on March 18. The lowest densities were observed on September 3 and November 5. Significant differences in abundances at each station were observed for the groups Acartia tonsa (Copepoda), Ctenophora, Medusae, Ostracoda, Zoea, and Amphipoda. Comparison of the dry and rainy seasons revealed significantly higher zooplankton abundance in the dry season and copepod domination of all stations; during the rainy season ostracods dominated the off-shore areas. Zooplankton abundance and distribution are influenced by upwelling, which occurs during the dry season in Culebra Bay.     

Sleeping site ecology in a rain-forest dwelling nocturnal lemur (Lepilemur mustelinus): implications for sociality and conservation

Suitable sleeping sites as potentially restricted resources are suggested to shape sociality in primates. We investigated sleeping site ecology of a rain-forest dwelling sportive lemur in eastern Madagascar for the first time. Using radiotelemetry, we characterized the type, quality and usage of sleeping sites as well as social sleeping habits of 11 focal individuals of the weasel sportive lemur (Lepilemur mustelinus) during the dry and the onset of the rainy season. Morphometric measurements provided additional information. The sexes showed an unusual sexual dimorphism for primates. Males and females did not differ in body length, but females surpassed males in body mass suggesting female dominance. Both sexes used dense vegetation and holes in hollow trees high above the ground as shelters for sleeping during the day. No sex difference in the quality of tree holes was found, but focal individuals used tree holes more often than open sleeping sites in dense vegetation. Both sexes showed high sleeping site fidelity limited to two to six different sites that they used primarily solitarily. The results imply that suitable sleeping sites are limited and survival of this species will strongly depend on the availability of mature rain forests with suitable hollow trees. Furthermore, these findings provide evidence of a solitary sleeping and ranging system in this rain-forest dwelling sportive lemur with suitable sleeping sites as defendable resources.     

Seasonal changes in reproductive and physical condition, sexual dimorphism, and male mating tactics in the jewelled blenny Salarias fasciatus

To investigate seasonal changes in reproductive and physical condition, sexual dimorphism, and mating tactics in the jewelled blenny Salarias fasciatus, monthly collections were conducted on the fringing reef in northern Okinawa, Japan. Monthly variation in the female gonadosomatic index suggested that the breeding season of this species is from April to June. The physical condition and hepatosomatic index of both sexes considerably deteriorated during the course of the breeding season. Such declines may be primarily due to egg production in females and brood care in males. Males’ elongated anal spines were longer than females’, but no other apparent sexual dimorphisms were detected, indicating that S. fasciatus exhibits a low degree of sexual dimorphism. Examinations of testes size and the testicular gland area during the estimated breeding season revealed that the gonadosomatic index values of smaller males did not differ from those of larger males. This result may differ from other blenny species that exhibit alternative male reproductive tactics. However, patterns of male testicular glands of S. fasciatus were similar to those of other blennies with alternative tactics, i.e., smaller males had poorly developed testicular glands compared with larger males.