摘要:

When acclaimated for two months at 26 C the social Mashona mole‐ratCryptomys hottentotus darlingi(±S.D.) resting metabolic rate (RMR) of 0·98±0.·14cm2O2g‐1h‐1(n=21), within a thermal neutral zone (TNZ) of 28 31·5 C ambient temperature (Ta). The body temperature (Tb) of the mole‐rat is very low. 33·3±0·5 C, and remained stable between 25 31·5 C (n=28). Above 33 C. Tb increased to a mean of 34·±0· C (n=28) (Ta range 33 39 C). Below Ta 25 C. Tb showed strong poikilothermic tendencies, with Tb dropping to a mean of 26·8±1·16 C. whereas above Ta25 C. Tb varied in a typically endothermic pattern. The conductance is high 0·19±0·03 cm2O2g1C1(n=28) at the lower limit of thermoneutrality. The mean RMR at 18 C (the lowest Ta tested) was 2·63 ± 0·55 cm3O2g1h1(n=7) which is 2·6 times that of the rest

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb01910.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The form of the proximal segments of antenna two peduncle and of the antennary gland exit duct on peduncle article two has been examined in 16 species of amphipod crustaceans (including 14 species of Talitridae).Gammarus duebeni(Gammaridae), regarded as exemplifying the norm for aquatic amphipods, has a very distinctive fluted exit duct emanating from a pronounced gland cone. The talitroidHyale nilssoniwas regarded as a typical representative of the hyalid‐like ancestors of the Talitridae. It also has a gland cone, but the exit duct of the antennary gland is a thin‐walled, collapsible cone. The two proximal articles of antenna two peduncle are much reduced in Talitridae. Only the second may retain a degree of mobility. No gland cone remains. The structure of the urinary exit duct in seven species of simplidactylate landhoppers (Bousfield's Gp IVa) was very similar to the hyalid condition. Beachfleas (Gp II) have strengthened, often sculpted ducts. whilst sandhoppers (Gp III) have no protruding exit duct at all. Only one species of Gp IVb (cuspidactylate) landhopper (Tasmanorchestiasp.) was investigated and it has an exit duct similar in form to that of the beachfleas (Gp II).Neorchestia plicibranchiata(a Gp IVa species), however, already known to be an anomalous species, has unusually elongate urinary ducts (for a Gp IVa species). These observations lend support to the notion that the landhoppers are a polyphyletic grouping and that the sandhoppers are a very isolated ecomorphological grouping within the fam

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb01911.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Two methods for the analysis of cross‐species data are used to investigate whether tarsal spur length or number are correlated with mating system in three phasianid subfamilies. One method, the phylogenetic regression. suggests that polygamous species have relatively longer and fewer spurs than monogamous species. hut this relationship is not found when a matched‐pairwise comparison is used. These ambiguous results suggest that at the moment it is not possible to conclude either way whether spurs are under any selective pressure related to mating system, and that previously published conclusions are not suppor

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb01912.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Daily energy expenditure (DEE) of free‐living birds during the incubation and subsequent brood‐rearing stages was measured using the doubly‐labelled water technique for seven species of bird. These data are combined with published information to provide a data set of 17 species of bird covering the mass range 12–85 g.Allometric relationships between DEE and body mass for the two stages of breeding were constructed using three models (log‐transformation regression, geometric mean regression, and iterative non‐linear regression). The geometric mean regression model was rejected as inappropriate. The iterative non‐linear regression model provides the best predictions of DEE given the average body mass of a species, but is of less value for comparing data sets. The most commonly used model (log transformation regression) was thus favoured for comparative purposes as the predictions it generates do not significantly alter the conclusions that would be obtained with use of the iterative non‐linear regression models (Marquardt model) for the data sets in this work. Comparison between the average DEE for the two stages of breeding suggest higher DEE during the brood‐rearing period, although this was significant in only five species.The difference in body mass among species can account for more of the variation in average DEE during incubation (r2= 82·6%) than during brood‐rearing (r2= 67·3%1), indicating that other effects such as activity are probably more important determinants of energy expenditure during brood‐rearing.The residual variation in DEE during incubation, after the effect of body mass had been removed, was considered for groups of species occupying different ecological niches. It is shown that the level of activity and ambient temperature can explain much of the residual variation in DEE during incubation.The blue tit was used as an example to demonstrate the role of energy balance as a constraint on reproductive success durin

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb01913.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The woodmouse is primarily a woodland species but it also occurs on maritime sand‐dunes. The home ranges of mice living on the sand‐dunes are much larger than those of animals living in woodlands. Here we test the hypothesis that this difference is due to the fact that woodland provides substantially more food than do sand‐dunes. Our experimental approach was to provide supplementary food in the form of wheatgrain to a sand‐dune population and to compare range sizes with a control population. Range sizes on the supplemented area were significantly smaller than the controls and essentially similar to those of woodmice living in deciduous w

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb01914.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The diet ofEpfesicus serotinuswas investigated by faecal analysis and the validity of this technique as a means of obtaining reliable quantitative results was assessed. Knowledge of what the bats eat will allow predictions of which habitats contribute most prey. Three male serotines were kept in captivity during the months of July and August 1991 and fed known quantities of identified insects. With captiveE. serotinusthe remains of prey appeared within 33 min of first bite and continued to appear for up to 32 h after consumption. Scales from twoNoctua pronubamoths consumed were contained in 59 subsequent droppings. Similarly, fragments of three beetles,Geotrupes stercorarius, were contained in 28 subsequent faeces.Analysis of the faeces of free‐living bats revealed insects from seven orders. Coleoptera were found to be present in 96.1% of the droppings examined; the next most frequently found order was Lepidoptera, occurring in 14.7%. The beetles were mostly associated with hay meadows (Aphodiusspp. andMelolonthaspp.), or grazed pasture (Aphodiusspp. andGeotrupesspp.). Quantitative determination of prey eaten is not possible owing to the large number of the droppings shown to contain the remains of marker insects and the long period over which they are produce

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb01915.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The diet and utilization by brent geese of two plant communities (Limonium/Armeriamarsh—a short sward community in the upper mid salt‐marsh and composed of several species, andSalicorniamarsh—a community of the lower salt‐marsh dominated bySalicornia europueaagg. andAster tripolium) were studied on the north Norfolk coast. The biomass on these communities was highest in autumn and declined markedly in November owing to the senescence and die‐off of the succulent species. This decline was not significantly precipitated by the grazing of the geese but coincided with their switch to inland habitats where the biomass m‐2and total food available on fields of winter wheat and grassland within the population's home range was 20–30 times greater. Brent geese continued to graze salt‐marsh at a low intensity through the winter, feeding largely onPuccinellia maritima.In spring they returned largely toLimonium/Armeriamarsh where they significantly reduced the regrowth ofPuccinellia maritima.The main plant species ealen wasPuccinellia maritima, especially in mid winter.Salicornia maritimaagg. leaves and seeds formed much of the diet in autumn, whereasTriglochin maritima, Plantago maritimaandAster tripoliumwere important foods onLimonium/Armeriamarsh in spring. All these species were selected at some part of the year. Selection was related to the proline (an imino acid used by salt‐marsh plants as an osmoregulator) and chloride content and avoidance related to tannins. Two species which contained condensed tannins.Limonium vulgareandArmeria maritima, were rarely eaten. As well as being a nutrient, proline may help to neutralize the effects of tannins in the diet if incorporated into prol

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb01916.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Several species of simultaneously hermaphroditic land snails show a genital dimorphism: aphallic individuals differ from euphallic ones by a lack of male copulatory organs (penis plus genital retractor muscle). Aphallic individuals can self‐fertilize or outcross as females but not as males. Thus, the mating system of a population may be significantly influenced by the proportion of aphallic individuals.We present data on the frequency of aphally in 23 natural populations of the rock‐dwelling land snailChondrina clientaon the Baltic island of Öland, Sweden. The populations varied greatly in percentage of aphallic individuals, ranging from 52.2 to 99.1%, (grand mean 77.7%)). This variation did not follow any geographical pattern.In a laboratory experiment, we examined whether food supply (high or low) and/or population density (high or low) experienced during ontogeny affected the expression of genital dimorphism. Snails derived from a population with 99.1% aphallic individuals and raised under different food and density conditions did not differ from the original population in frequency of aphally. By contrast, when snails from a population with 66.7% aphallic individuals were raised on a low food supply, more individuals became euphallic than expected under complete genetic determination. These results suggest that, in addition to a genetic component. the expression of the genital dimorphism can be influenced by environmental condit

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb01917.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The feeding responses of three species of newt larvae were compared under circumneutral and sublethal acid conditions. Under acid conditions (pH 4.5) feeding behaviour was suppressed in palmate newts,Triturus helveticus, and smooth newts. T. vulgaris, but not in crested newts,T. cristatus.At low pH, approach and orientation towards food occurred inT. helveticusandT. vulgaris, but snapping was inhibited;T. cristatussnapped and consumed food immediately it was offered under the same conditions. These differences are not consistent with the apparent greater tolerance ofT helveticusfor acidified ponds. The observations suggest that the chemosensory system ofT. helveticusandT. vulgaris may be impaired at low pH.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb01918.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Sex differences in the dynamics of the relationship between harbour seal mothers and their pups were investigated. An index of pair proximity governance suggested that pups became increasingly responsible for maintaining the distance between the pair over the course of the nursing period. Male pups demonstrated a stronger tendency to control initiation distance than female pups. A Nursing Index utilizing suckling bout initiations and terminations revealed that, as weaning approached, pups became progressively more responsible for the continuance of nursing. Male pups exhibited more control than female pups, primarily through initiating a greater portion of the bouts. On‐teat times averaged 4.08 min per bout, with no significant differences between male and female pups. Male pups, however. nursed a greater portion of haul‐out time due to higher bout frequencies obtained through more bout initiations. Mothers did not preferentially reject attempts to nurse by pups of either sex. These results suggest that the tenet of parental investment theory suggesting male pups enjoy preferential investment may be misleading. In harbour seals. male pups seem actively to seek out resources, as opposed to any inherent strategy on the par1 of the mot

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1993.tb01919.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY