摘要:

In mammals, lactation performance may influence future reproduction of a mother and her young. We measured the quantity and quality of milk produced by female house mice (Mus musculus) during a period of 28 days after birth of a litter. We aimed to analyse how females cope with the energy demands of different sized litters as a tradeoff between current and future reproduction. Litter sizes examined were small (six young), intermediate (7.3 0–7), and large (12 young).Females met the energy demand of a growing litter both by increasing the amount of milk given to the young and by improving the quality (through an increase in total solid and fat concentrations) to a peak during days 9–16. At the onset of weaning (day 17), milk production decreased and young shifted to solid food. The main energy source in the milk of house mice was fat, which provided more than 80% of the energy to the suckling young. Average lipid concentrations were 20%, and peak values of 33% were reached during days 13–16. Protein concentrations were 6–8% and carbohydrate (lactose) concentrations 3–4%.With larger litters, females increased both the amount of milk and the absolute amount of major nutrients (lipids, proteins, lactose). However, regulation was imperfect. When litter size was doubled from six to 12, amount of milk produced rose by 44%, and energy content only rose by 30%. The reduction in milk supply for individual young in larger litters was reflected in slower growth and lower weaning weight.The efficiency of conversion of milk energy into biomass of young was highest for intermediate litters (51%; for small litters, 43%; for large ones, 36%). During days 5–16, a single pup in an intermediate litter needed less energy for metabolism and growth than pups in the other litter sizes examined.Although individual young of small litters have a relatively high weaning weight‐which might improve their future reproduction‐females gain higher reproductive success by dividing the energy available per litter between the largest number of young they can raise to a weaning weight of on average 9 g.For the time‐lifen reproductive success of a female house mouse‐at least for the strain used in this study‐an intermediate litter size of seven seems to be best because of a favourable ratio of energy cost of lactation to number and s

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02425.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A study of blood levels in mute swansCygnus olorin Ireland has revealed that ingested lead pellets are responsible for acute lead poisoning. Forty‐two percent of blood samples from 890 live birds at one site showed elevated lead levels. X‐ray examination of live birds revealed the source of contamination to be ingested lead pellets. Urban birds were shown to have higher (P0001) lead levels than rural birds, the blood lead levels of which were presumed to reflect natural background levels. Urban grass was shown to have elevated lead but this did not cause lead poisoning in Canada geeseBranta canadensis. Post‐mortem examination has shown that 68% (n= 101) of all mute swans examined from a number of sites died from lead poisoning. Two sources of poisoning were identified; spent gunshot from a claypigeon shooting site at Lough Neagh, Northern Ireland, and lost or discarded anglers' weights at Cork Lough and at a fishing pond in Belfast, N.I. The first known case of lead poisoning in whooper swansCygnus cygnusin Ireland is recorded which resulted from the ingestion of gunshot used almost two decades earlier. Aspects of the pathology of lead poisoned swans is disc

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02426.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The anatomy of female reproductive tracts collected from 28Acrobates pygmaeus(Shaw) is described. The tract differs from that of other small possums of the families Burramyidae and Tarsipedidae by having a prominent septum that divides the left and right sides of the vaginal system for most of its length. A median birth canal occurs at parturition but closes within 3–4 days of birth.In south‐eastern Australia, most femaleA. pygmaeusproduce two litters within the breeding season (July to February). A post‐partum oestrus follows the birth of the first litter and the resulting embryos undergo a period of embryonic diapause. The embryos grow slowly during diapause, until the unilaminar blastocysts become approximately 2.0 mm in diameter, and contain about 2,000 cells. The factors influencing reactivation after diapause remain unclear, since no embryos past the blastocyst stage were found. Post‐partum oestrus may follow the birth of the second litter, but if it occurs, the ova either remain unfertilized or degenerate after fertilization. Females are anoestrus during the non‐breeding season.Corpora lutea in the ovaries seldom outnumber blastocysts in the uteri or teats in the pouch. During diapause they undergo a pattern of growth similar to that of the blastocysts and enter a quiescent phase. Corpora lutea disappear within nine days of birth.The pattern of female reproduction in this species is similar to that of other small possums of the families Burramyidae and Tarsipedidae, but is distinct from those of other m

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02427.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Between 1984 and 1986, reproductive tracts were collected from 17 maleAcrobates pygmaeus(Shaw) from south‐eastern Australia and the anatomy of these tracts is described. The prostate is heart‐shaped and the arrangement of its three segments, anterior, central and posterior, is different to the patterns described for other marsupials. The testes are large in proportion to the body size but their structure and that of the remainder of the tract is typical of other marsupials. The sperm morphology is similar to that of the Phalangeridae and Burramyidae.Seasonal cycles were found in the sizes of testes and prostates. Increases in testes sizes, starting in April or May, were associated with increases in seminiferous tubule diameter and Leydig cell size. The weight of the prostate increased rapidly to a short peak in June when the testes also reached maximum weight. The first births occurred approximately one month later in this population. Following this peak, both the testes and the prostate decreased in size and had returned to the original weights by January. The beginning of this period when the testes and prostate were small coincided with the cessation of births in the population and was marked by an interruption in spermatogenesis.Males born early in a breeding season mature before the start of the next breeding season, but males born at the end of a breeding season may not mature until the second season after their birth, at which time they are approximately 18 months of

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02428.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The body fattening and weight gain preceding vernal migration in birds is timed by a set of environmental factors of which daylength is predominant. However, the mechanism(s) by which these events is determined is poorly understood. Previous investigations on a photoperiodic migratory species, the blackheaded bunting (Emberiza melanocephala), indicate the involvement of a light‐sensitive circadian rhythm during initiation of fat deposition and body weight gain. This communication presents data from another set of experiments aimed to characterize further the mechanism(s) of fat deposition in the same species.Groups of photosensitive, unstimulated and stimulated birds were subjected to transfer and superimposition experiments for 30 days. While the former set included shifting of long‐day (LD) birds to DD, SD (short days), DD/LD and SD/LD, in the latter a 90‐minute bright light was superimposed at two different times of the day during the dim‐green lighted phase 15L:9D of varying intensity. Birds were weighed at the beginning and at the end of experiments. Those in transfer cycles were also weighed at 10‐day intervals. The results suggest that the premigratory body fattening and weight gain in blackheaded buntings is light dependent and timed by environmental daylength in accordance with the photosensitive endogenous circadian rhythm (ECR). They also show that the photoperiodic responses in birds in general are mediated by circadian

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02429.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Geometric design in the barnacle genusBalanushas been studied in relation to variation in adult shell form, that includes differences among species, and size‐related changes in shape. The genus comprises 40 Recent species, and as a group these display a more or less constant morphology over an extraordinary size range (10 to 200 mm in basal length).Linear and volumetric measurements were collected from 232 adult individuals of 14 species representing the variation in size, shell form and shell design thought to occur in the genus. Specimens were chosen to represent the size ranges of the species. Only isolated individuals growing on planar surfaces were used; shells were complete, undamaged and undistorted.Shell form differs among taxa, and no two species scale alike; intraspecific variation for five ratio variables shows strong allometry over the adult size range of each species. As size increases, there is a trend for the basis and orifice to maintain their shapes or to become slightly more elliptical, and for shells to become more conical and proportionately taller.Throughout their size ranges, species can be described by these geometries: paraboloid (6 species), frustum of an ellipsoidal cone (5 species), frustum of a cone (2 species) and a cone (1 species). Shell geometry is not a function of species size, but there does appear to be a correlation between shell geometry and shell volume. Species with relatively small shell volumes are described by a frustum of an ellipsoidal cone, or by a cone, while those with a relatively large shell volume are described by a paraboloid, or by the frustum of a con

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02430.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Condition in animals is often measured in relation to various demands, such as reproduction, migration and cold weather. Usually, indices of protein and fat reserves have to be measured on dead animals. Measurements on live animals enable variations in the condition of individuals to be monitored over time, and can be related to their life histories.In birds, the size of the breast muscle is the most commonly used measure of protein reserves. A technique for measuring breast muscle thickness was developed, using ultrasound, and was tested on mute swans. The measurements were accurate and highly repeatable. Breast muscle thickness was positively related to the lean dry weight of the breast muscle, and is likely to be a good indicator of total protein reserves.A system of fat scoring by colour was developed to assess the size of the subcutaneous fat layer. Although the method relies on subjective judgements, the results were highly correlated with the percentage of fat in the subcutaneous layer, and with other measures of fat reserves.Measurements were made on live, non‐breeding swans to monitor seasonal variations in reserves. The seasonal pattern of fat reserves was similar to the normal cycle of weight changes; high in winter and low in summer. There was no change in relation to the moult. No distinct seasonal variation in muscle thickness was found.There is an unusual pattern of change in the relative size of reserves during emaciation in swans. Muscle reserves appear to be depleted to a greater extent than fat reserves. This is possibly due to the effects of lead poisoning, causing protein necrosis and preventing muscle regeneratio

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02431.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The maximum stresses to which a wide range of mammalian limb tendons could be subjected in life were estimated by considering the relative cross‐sectional areas of each tendon and of the fibres of its muscle. These cross‐sectional areas were derived from mass and length measurements on tendons and muscles assuming published values for the respective densities. The majority of the stresses are low. The distribution has a broad peak with maximum frequency at a stress of about 13 MPa, whereas the fracture stress for tendon in tension is about 100 MPa. Thus, the majority of tendons are far thicker than is necessary for adequate strength. Much higher stresses are found among those tendons which act as springs to store energy during locomotion. The acceptability of low safety factors in these tendons has been explained previously (Alexander, 1981). A new theory explains the thickness of the majority of tendons. The muscle with its tendon is considered as a combined system which delivers mechanical energy: the thickness of the tendon is optimized by minimizing the combined mass. A thinner tendon would stretch more. To take up this stretch, the muscle would require longer muscle fibres, which would increase the combined mass. The predicted maximum stress in a tendon of optimum thickness is about 10 MPa, which is within the main peak of the observed stress distribution. Individual variations from this value are to be expected and can be understood in terms of the functions of the various musc

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02432.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Dusk to dawn observations, using a bat detector and occasionally an image intensifier, were made outside two nursery roosts of lesser horseshoe batsRhinolophus hipposiderosfrom late May to September. Emergence was correlated with sunset but delayed by extended twilight. Light intensity was important in triggering departure and cloud cover advanced it. Light‐testing behaviour was invariably undertaken, in the form of brief flights out and back into the roosts. The exit from one roost was shaded by trees and exploratory flights were generally more extended there. Heavy rain inhibited emergence. There was almost always intermittent activity throughout the night, with many individuals returning and departing, and no indication of seasonal or overnight peaks. A bat detector inside a third roost confirmed overnight observations at the other two. Some bats often returned to the roost for the night before dawn. Dawn return was linked to sunrise, prolonged twilight in midsummer hastening it. Colony size varied appreciably over periods of a few days and even overnight. There is some limited evidence that increased colony size, perhaps through social interaction, may have influenced timing of departure at dusk and return at daw

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02433.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Observations and experiments on the behaviour of shore rocklings have shown that the modified and vibratile anterior dorsal fin can be involved in the detection of food but is not essential to foraging by the fish. The epidermis of the vibratile fin rays contains numerous chemosensory cells, of similar cytology in the two species studied. These chemosensory cells are compared with the gustatory cells of the taste buds borne on other fin rays. Synaptic modifications in both cases consist of densities on the apposed membranes, with a dense layer under the membrane of the neurite more distinct than that in the cell. Vesicles are not a feature of these synapses, although some of the sensory cell bases are vesicular. Denervation experiments have shown that the chemosensory cells of the vibratile rays are supplied by a facial nerve component. After denervation a small proportion of the sensory cells were found to have an association with spinal nerve fibres. The present status of solitary chemosensory cells in fishes is discussed.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1988.tb02434.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY