摘要:

(With 9 plates and 2 figures in the text)Wing deformations were studied in representatives of several hymenopteran families during free Right in hovering or near hovering conditions. The claval furrow, costal break, stigma and a variety of flexion lines occupying the wing apex are all involved in regulating forewing profile during the flight cycle in lchneumonidae and Tenthredinidae. In these families, as well as in the sphecidSphex rujocincius, the median flexion line of the hindwing is also active in the terminal stages of supination. The plaiting fold of the vespid forewing plays an important role in profile control during the upstroke, reversing its polarity compared to rest. Little wing distortion was observed in the large scolidsScotia flavifronsandS. hirta, possibly attributable to the presence of strengthening ridges and grooves in the wing apex.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb05363.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Relationships between body shape and relative abdominal size were compared among differentially elongate species within the scincid lizard genusBrachymeles, to investigate how morphological evolution affects the proportion of body volume available to hold eggs and offspring. Relative abdominal size is inversely related to elongation, suggesting that relative clutch mass decreases with addition of abdominal body segments. Shape‐volume relationships contradict trends seen in comparisons among distantly related limbed and limbless squamates (lizards and snakes), in which snakes have relatively more abdominal volume. Comparison within a phylogenetically restricted group allows the identification of functional and ontogenetic factors potentially limiting reproductive output. InBruchymeles, constraining factors include retention of anterior body segments bearing parasternal ribs, which prevents extension of the clutch anteriorly within the body, and reduction of allometry of abdominal segments, which provides extended series of uniformly‐sized vertebrae for limbless locomotion, but reduces the relative size of the abdomen. The latter trait is associated with overall size reduction, which affects relative egg‐size and packing. Factors constraining abdominal volume in this genus are probably common to other elongate lizards, a morphological group that has been rarely represented in comparative studies of life hi

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb05364.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The three most important primates of French Guiana are frugivorous species, but to different degrees.Ateles paniscusis almost exclusively frugivorous,Alouatta seniculusfrugivorous‐folivorous, andCehus apellupartially insectivorous; thus, the overall specific diet spectra arc well separated. During the season when fruit production is minimal, fruit intake by all species is also minimal which results in the greatest diversities in diet and the lowest diet overlaps. Real competition for the common main food category, i.e. fruits, only occurs during the most favourable period. Nevertheless, some fruit characteristics (e.g. size…) separate the monkey species from each other in fruit choice and make the interspecific competition of little importa

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb05365.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Anogenital distance (AGD). a sex differentiation marker in mice (Mus musculus), is thought to be a secondary sexual trait exclusively regulated by androgens during development. However, recent studies suggest that some so‐called secondary sexual traits may be influenced by sex‐chromosomal genotype. To explore this question further we studied the AGD of theXXSxr'sex‐reversed’mouse, which has adequate androgens for masculinization.The AGDs of adult and prepubertal XY,XYSxrcarrier,XXSxr'sex‐reversed’and XX mice were measured. We found that adultXXSxr'sex‐reversed’mice (which we refer to as pseudomales) andXYSxrcarriers have shorter mean AGDs than their XY siblings. PrepubertalXXSxranimals also have shorter mean AGDs than their XY siblings when AGD is expressed as a proportion of body length. XX adult and prepubertal mice have significantly shorter AGDs than the other genotypes at similar stages of development. The differences in AGD between adult and prepubertal XY and XXSxr sibs, and adult XY and XYSxr sibs, reported here, do not appear to be due to androgen levels, since adult testicular and serum testosterone levels are higher in pseudomales and carriers than in XY mice, and fetal pseudomale androgen levels also appear to be at least as high as those of normal males. Furthermore, the AGD differences between genotypes are not correlated to differences in testis size. We conclude that the differences are likely to be due to a tissue specific effect of the genetic constitution of the individuals, as is the case with scrotal development in the marsupialMacropus eugenii(the

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb05366.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The toad,Bufo viridis, can live for several months without access to free water, absorbing soil‐bound water down a water‐potential gradient created, mainly, by accumulating urea in its body fluids. We investigated if the retention of urine was sufficient to account for the rate of accumulation or if an increased rate of urea production was needed in order to do so. The basal rate of urea production in unfed animals in the absence of osmotic stress was estimated by two methods; first, analysis of the bathing medium and, secondly, collection and analysis of urine at two‐hourly intervals. This was then repeated with animals fed a weight‐maintaining diet. Generally similar results were obtained by either method in both fed and unfed animals, although higher urea production rates were found in the former. Although it had been planned to apply the short interval method to toads with free access to water, the control condition for toads transferred to soil, it proved to be impracticable. Some animals did not bathe for almost a day, during which time minute quantities of urine were obtained. Larger volumes were only produced during or after bathing. Consequently, animals which were partially immersed in water were substituted as controls. Total urea content was determined in these and in toads after a week on soil. The calculated increase was compared to that which could be expected from urine retention. It was found that urea accumulated at more than twice the predicted rate. When rates of accumulation were calculated over longer periods, urine retention alone was sufficient to account for them within three weeks on soil, the usual period required for acclimation. We concluded thatB. viridisincreased its rate of urea production only for a short period, until a favourable water potential gradient was a

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb05367.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In captivity, Orkney volesMicrotus uruulis orcudensisshow an activity pattern that consists of regularly alternating periods of rest and activity with a periodicity of about 2.8 hours. Captive voles kept under ambient conditions are equally active day and night at all times of the year. Free‐living voles also show a regular short‐term rhythm of activity but in addition the partition of activity between day and night varies seasonally. At two sites on Orkney Mainland cyclic variation in diurnality with a period of 12 months were recorded. Although surface activity occurred during both the day and night throughout the year, day activity predominated, particularly during the winter months. The cycle appeared to be synchronous at the two study sites.Seasonal variation in diurnality appeared to be associated with population density and due largely to the proportion of juveniles in the population. Given the 12‐month cycle of diurnality found in the Orkney vole, phase relationships with photoperiod are likely to be consistent between years. This may explain why populations of this subspecies do not appear to undergo multi‐annual population cycles.Despite intense levels of predation by raptors, including the short‐eared owl which switches between nocturnal and diurnal hunting, Orkney voles exhibit a relatively simple and highly predictable cycle of diurnality. This cycle is unlikely therefore to have evolved as a means of preventing predator specialization with respect to time of day, seaso

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb05368.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Inhibition of reproduction occurs in colonies of the Damaraland mole‐rat (Cryptomys damarensis), where one female and usually one male are reproductively active. They remain the sole reproductive animals thoughout their stay in the colony, which in the field may exceed five years.An 18‐month study on a captive colony ofC. damarensisshows that non‐reproductive females remain anovulatory and always have concentrations of urinary progesterone lower than that of the reproductive female 10.7 8.8 nmols/mmol creatinine (n = 85), although their progesterone concentrations are slightly elevated when the reproductive female is early in pregnancy. In contrast the reproductively active female has elevated concentrations of progesterone 63.3 70.1 nmols/mmol creatinine (n= 14).Standard histological together with immunohistochemical examination of the ovarian structure shows that follicular development in the non‐reproductive females is halted at varying stages prior to ovulation and that the unruptured follicles luteinize. These unruptured luteinized follicles stain positive for 3β hydroxysteroid dehydrogenase—the enzyme catalysing the synthesis of progesterone from pregnenolone. It is possible that the low levels of circulating progesterone produced by the luteinized follicles in the non‐reproductive females in the colony are sufficient to feedback on the hypothalamo‐pituitary axis and prevent the surge of LH necessary for ovulation.Behavioural studies provide corroborative evidence for sexual suppression. Thus the non‐reproductive females in the colony are never involved in courtship or copulatory behaviour. nor do they actively solicit males in the colony. The reproductive female, however, plays an active role in mate selection and is the initiator in courtship behaviour.The suppression of ovulation in non‐reproductivc females is maintained for as long as there is a reproductive fe

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb05369.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

From 1987 to 1992 diet and condition of two populations of wild boar which received no supplementary feeding were studied in the Veluwe area, a large area of heathlands and forests in The Netherlands, and were compared with those obtained in a previous study (1974–1976), when supplementary food was provided. Composition of stomach contents depended mainly on season, mast availability, and area‐specific factors, whereas sex and age were of little or no importance. Density dependence was found for the decrease in mast (tree seed) consumption from autumn to winter. In autumn, and in winters of rich mast years, mast was the main constituent of the diet. In winters of poor mast years this was replaced by broadleaved grasses in one area and by broadleaved grasses, wavy hairgrass, and roots in the other. We found no important differences between the stomach contents of animals receiving no supplementation, and the natural fraction during a period of supplementary feeding. Variation in body weight was related mainly to age and sex, but also to mast availability. Judged by relative loss of body weight and decrease of bone marrow fat, juveniles seemed to suffer more from poor mast availability than adults. The decrease in body weight from autumn to winter was greater when population density was high. In poor mast years, recruitment into the population receiving no supplementation depended on the availability of broadleaved grasses; in rich years, recruitment was still lower than in populations receiving supplementary feeding. In populations receiving supplementary feeding, recruitment seemed independent of mast availabil

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb05370.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A tooth eruption and wear pattern useful to determine ten age classes when the horns are not available for this purpose, is described for Cantabrian chamois (Rupicapra pyrenaica parva) inhabiting the Cantabrian Mountains (north of Spain). In animals under eight years old, age is not significantly over‐ or under‐estimated when using the method, however, the age of animals older than eight years is significantly under‐esti

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb05371.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Static nestling, adult and ontogenetic allometry were analysed in three species of finches. Static nestling allometry was very similar across age in early ontogeny and among species and could be approximated by a single matrix of phenotypic variances and covariances. The first eigenvector of this matrix showed negative allometry of bill and tarsus to mass, but positive for wing length to mass. Adult static allometry was also very similar among species, but differed from nestling pattern. In adults the bill had a positive allometry in relation to tarsus and wing, but negative to mass, while tarsus and wing were unrelated to mass. The ontogenetic allometry in each species was very similar to nestling static allometry. Viewed in relation to final size, bill characters grew more slowly than body characters, but for a longer time, which created the difference between adult and nestling allometric patterns. There were differences among species both with regard to elevation and slope of allometric coefficients, suggesting that the differences among species came about by changes in the three fundamental ontogenetic parameters namely growth rate, onset of growth and offset of growth.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb05372.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY