摘要:

The supercooling points (SCPs) of a field population ofPolyzonium germanicumwere measured at different stages in the life cycle. There was no post‐freezing survival under the experimental conditions used. The mean SCP was ‐26.2°C for eggs and increased to ‐18.2°C for juveniles of stadium III experiencing their first winter. From stadium V onwards, SCP varied considerably among individuals, ranging from ‐22.7 to ‐4.7°C. SCP was shown to increase significantly with body size in both sexes. Seasonal changes also occurred in males, SCP being lower in autumn‐winter than in spring‐summer. Measurements from a sample starved in the laboratory showed that the winter decrease could result from starvation affecting a proportion of males in the field. There was no relationship between the SCP and relative water content of individuals. After starvation in the laboratory, however, there was a relationship between the SCP and relative fat content of males. The results show that freezing is not a significant threat to the field population studied, with the possible exception of the largest overw

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05310.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Diet selection and activities of sheep and red deer grazing alone and together across a grass (primarilyLolium perenne/Agrostis capillaris) and heather (Calluna vulgaris) boundary, between July and October, are described.Throughout the experiment, both animal species had a much higher proportion of grass than heather in their diet. Time spent grazing on each type of vegetation was similarly greater on grass, and the bite rates of the animals were also more rapid on the grass than on the heather.Red deer spent more time grazing per 24 hours than did sheep, with sheep grazing less during darkness hours than red deer. Total grazing time of both species did not decrease with decreasing daylength from July to October.There were no consistent differences in the diurnal patterns of activity of sheep and red deer, with both species showing 2‐3 large grazing peaks per day.There were no consistent effects of mixing sheep and deer on their grazing behaviour and diet compositio

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05311.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

An allometric analysis of reptilian incubation time was performed. Incubation time increased with increasing egg mass (allometric exponent = 0.14, r2= 0.31). However, significant heterogeneity was found within the Reptilia for this character. If periods of developmental arrest are excluded the orders Crocodylia, Testudinata, and the suborder Serpentes have the shortest incubation times and the lizards the longest. Significant differences within lizard families were also observed (Iguanidae, Agamidae, Gekkonidae, and Lacertidae have shorter incubation times than the Varanidae and Teiidae). Preliminary analyses indicate the heterogeneity in incubation time observed within the Squamata is correlated with differences in brain mass; this is similar to findings for mammals. The variation in incubation time indicates the existence of differences in growth rates in reptilian groups and suggests a partial explanation for the observed distribution of viviparity within the Squamata.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05312.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

At least 193 species of mammals are known to occur within the Manu Biosphere Reserve in south‐eastern Peru, contributing to its stature as one of the world's richest protected areas. Bats (Order Chiroptera) comprise more than 42% (82 species) of this diversity. Analyses of bat capture records over a transect extending more than 3 km in elevation show that most bat species at Manu are widely distributed in the Amazon Basin. Few are montane endemics or are localized in south‐eastern Peru, although exceptions to this generalization include two species new to science. Highland bat faunas tend to be attenuated versions of those found below, and the elevational zonation of bat communities is weak. Species turnover with elevation is monotonic and more‐or‐less smooth, with Jaccard's similarity values falling to 0.5 for sites differing by 750m in elevation. Subtle and orderly change in species composition with elevation is also reflected in the nested‐subset structure of these communities; over 19 different levels, this pattern of hierarchical structure is both striking and highly significant. Elevational ranges of species generally increase with elevation, in accordance with Stevens' extension of ‘Rapoport's rule’ of range amplitude. However, support for ‘Stevens' rule’ may be trivial, given Amazonian richness and Andean impoverishment. Reduced richness and poorly developed endemism in Andean bat communities contrast with patterns shown by sympatric rodent faunas, which are diverse and strongly endemic on the Altiplano and markedly zoned along the Eastern Versant. Contrasts are less sharp with bird communities, which nevertheless exhibit stronger zonation and higher endemicity. Factors responsible for these distinctive distributional patte

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05313.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

To understand their function and ontogeny better, we conducted a morphometric analysis of claw size and shape variation in the strikingly heterochelous, north‐eastern Pacific ghost shrimp,Neotrypaea(formerlyCallianassa) californiensis.Master claws approached 25% of total body weight in mature males, but rarely exceeded 10% in females. Minor claws were less than 3% of body weight in both sexes. The proportions of right and left master claws did not differ significantly from 50:50. Males exhibited a greater positive allometry than females in both master and minor claw size, though master claws differed more than minor claws. Sexual dimorphism was also observed in master but not minor claw shape: compared to females, mature male master claws: a) were proportionally higher relative to their length; b) exhibited a deeper propodal notch and consequently a larger gape; c) developed a more slender and more distally hooked dactyl; and d) exhibited more well‐developed teeth about the periphery of the claw gape.The shape of the conspicuous gape in mature male master claws bore a close resemblance to the cross‐section of similar‐sized master claws. The shape of this gape, and the presence of fine teeth about its periphery, strongly suggests that master claws function in a highly stereotyped form of grappling during agonistic encounters or perhaps during mating between similar‐sized conspecifics. In addition, a landmark morphometric analysis of relative growth suggested that the pronounced propodal notch develops via localized deformations near the base of the fixed finger rather than via a more generalized contraction of the ventral manus region. Finally, a preliminary survey suggests that the distinctive propodal notch, which may be diagnostic of the hypothesized grappling function, has evolved at least twice in the Callianassidae, once in the Callianassinae and once in the Callichirinae. Sexual selection may have significantly influenced the evolution of these unusual mas

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05314.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The Australian elapid snake genusVermicellahas traditionally included three taxa:annulata, multifasciata, andsnelli.These animals have a history of unstable taxonomy and nomenclature, with rearrangements based mainly on subjective evaluations by different authorities rather than on acquisition of new data. We have quantified characters of external morphology to examine patterns of phenotypic variation in 425 museum specimens ofVermicella.Our aims were to understand better the nature of morphological variation in the genus, and the taxonomic implications of this variation, using univariate and multivariate statistical techniques. Based on our results, we recognize each of the three currently described taxa as separate species, and describe two additional species.Vermicella multifasciatais restricted to those specimens from the Darwin area that display exceptionally high numbers of, and very thin, body bands, and is sympatric with a new species described in this paper.Vermicella snelliis restricted to northern Western Australia and a second species from the Alice Springs area of the Northern Territory that displays fewer body bands is described.Males have fewer ventral scales and more subcaudal scales than females in the four species, with sample sizes large enough for meaningful statistical analyses, andV. annulatafemales have more body and tail bands than conspecific males. In conjunction with the taxonomic study, we also examined reproductive biology and diet ofVermicella.Females reach larger adult body sizes than males inV. annulata, V. intermedia, and probably the other species as well. Gut contents of four species suggest that they feed solely on blind snakes of the genusRamphotyphlops.Clutch sizes for the smaller species ofVermicellaare low, ranging from one to four, while published data for the largerV. annulatashows clutch size to vary from two to 13. Based on published work, it appears that the affinities ofVermicellamay lie withSimoselapsin Australia and/or some Melanesian elapids.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05315.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

In squamate reptiles there is an allometric pattern for small‐bodied females to have smaller clutches and proportionally larger eggs than large‐bodied females, and this pattern occurs both among and within species. The allometric patterns in two species of the geckoGehyrawere studied to see how evolutionary reductions in adult body size affect fecundity and offspring size among species, and how these changes affect allometric relationships within species.Gehyra dubiahas two eggs per clutch (the typical clutch size for gekkonid lizards), whereas the smallerbodiedG. variegatahas a single egg per clutch. Within both species, egg size increased with female body size. The data are consistent with at least two mechanistic hypotheses: (1) that the width of the pelvis constrains egg size; and (2) in species with invariant clutch sizes, larger females can only allocate additional energy towards egg size and not number. More direct tests of these hypotheses are warranted. Miniaturization of body sizes inGehyrais correlated with a clutch size reduction of 50% (from two to one), and a large (1.7‐fold) compensatory increase in relative egg mass. However, the small‐bodiedG. variegata(one egg per clutch) had a lower relative clutch mass than didG. dubia.These findings have implications for understanding the influence of evolutionary reductions in body size on reproductive traits, and for allometric trends in squamate reptiles in

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05316.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Small birds in temperate zones increase body mass in winter (Lehikoinen, 1987). We investigated daily and annual variation of body mass and fat reserves of locally‐reared Australian zebra finchesTaeniopygia guttata, by exposing them to different photoperiods, feeding periods, and temperatures.Experiments with long and short photoperiods and long and short feeding periods, showed that long photoperiods increased body mass and fat reserves of the zebra finches, and readiness to breed, independently of the actual feeding period.Furthermore, the zebra finches in indoor aviaries with constant temperature (22‐24°C) and in outdoor aviaries with ambient temperature, both exposed to the natural daylength changes of Bielefeld, Germany (52 °N), had high dawn body mass in summer (12.9 and 12.0‐12.4g, respectively) and low in winter (10.7 and 11.1 g, respectively). Thirty to sixty percent of these mass changes were related to changes in fat reserves, so that the finches had only 0.1‐0.2g of metabolizable fat reserves in short photoperiods (or in winter), which increased up to 1.5g in long photoperiods (or in summer).Indoor finches consumed more seeds in summer than in winter (3.3 vs. 2.7g/day), while outdoor finches consumed 4‐5g of seeds per day throughout the year, which probably represented the limit of energy intake for a 11‐13g bird (Kirkwood, 1983). Nightly mass loss, increasing from 0.7g in summer up to 2.0g in winter, was highly positively correlated with night length, not influenced by ambient temperature. Foraging before dawn and after dusk, roosting with well‐filled crops, and decreasing body mass and fat reserves, seem to be adaptations of zebra finches for survival in winter. The summer fattening probably accelerates reproduction in this opportunistic breeder, by allocating more time to reproductive behaviour and more endogenous nutrients t

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05317.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The shallow subtidal scallopMinnivola pyxidutusoccurs in the relatively clean oceanic, southern, and south‐eastern waters of Hong Kong and elsewhere in the Western Pacific and is highly polymorphic in terms of shell patterning of the left, upper valve. Locally, because of sea‐bed perturbations, numbers are declining. The species can probably live for ∼ 3 years, with reproduction occurring in winter.M. pyxidatusis monoecious.Shell form and anatomy are described. Normally, the species lives attached by a fragile byssus to sand grains or stones, but can swim, albeit weakly, in response to predation risks.In most respects,Minnivola pyxidatusis a typical scallop, with a bowl‐shaped, right lower valve and a concave, disc‐like, left upper valve. The mantle has pallial eyes and a complex array of tentacles which possess small, ciliary‐based sensory cells. There is also a cleansing tract on the outer surface of the middle mantle fold and a muscular velum formed from the inner fold. The latter is developed into a simple exhalant aperture posteriorly. Both mantle lobes possess extensive posterior pallial glands and an abdominal sense organ on the right lobe only, anterior to the single posterior adductor muscle. Ciliary currents of the mantle cavity are for cleansing and are powerful, particularly on the visceral mass and right mantle lobe but not the left.The ctenidia and their ciliary currents are typical of the Pectinidae except that the ascending lamellae of all demibranchs are greatly reduced and, it is suggested, previse the situation seen in the Propeamussiidae where they are lost and the ventral margins of the inner and outer descending lamellae fuse to create an ‘inside out’ gill. Unusually, the labial palps ofMinnivola pyxidatusare fused to the mantle and visceral mass, preventing their collapse in the mantle cavity and thus maintaining particle selection efficiency. The gut is simple. Left and right statocysts are unusually equal and the pericardium is located dorsal to the adductor muscle.Minnivola pyxidatusis adapted to an epibenthic life on subtidal sands and muds. Powerful cleansing currents and an ability to swim have allowed this species to survive in dredged and trawled waters with high levels of settling and r

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05318.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05319.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY