摘要:

The common frog and the pigmy shrew are common vertebrate predators in the uplands of Co. Antrim, Northern Ireland. This report concerns their habitat preference and trophic biology which are poorly documented at higher altitudes. Frogs preferred damp, grassy, reclaimed habitats while pigmy shrews appeared to favour moorland dominated byCalluna vulgaris.Both frogs and shrews were absent from pitfall trap collections from December to February and numbers of both were low until late spring. This corresponded to the period of lowest invertebrate abundance. Examination of stomach contents suggests that frogs are less selective feeders and utilize a greater diversity of prey items than pigmy shrews. Although sample size is low early in the year, diversity of the diet of pigmy shrews apparently increased from the first to the second quarter and again in the third quarter of the year. This led to an increase in food niche overlap with frogs in late summer but at a time of year when food supply was greatest. It is unlikely, therefore, that dietary overlap constitutes a basis for interspecific competition between frogs and shrews. This is likely to be ameliorated by habitat and behavioural differences between the two predators.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04025.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Enzyme variation has been investigated in eight populations ofBulinus cernicusfrom Mauritius using isoelectric focusing and starch gel electrophoresis. Of 11 loci examined for 10 enzyme systems, seven were found to be polymorphic. These were malate dehydrogenase, glucose phosphate isomerase, acid phosphatase (A and B), 3‐hydroxybutyrate dehydrogenase, 6‐phosphogluconate dehydrogenase and NADH‐dependent diaphorase. Invariant loci were phosphoglucomutase, xanthine oxidase, fructokinase and αaL‐glycerophosphate dehydrogenase. The percentage of polymorphic loci within the populations ranged from 9.1% to 54.5%. The average heterozygosity per population for all loci ranged from 0,009 to 0.203. Genetic distance values ranged from 0.01 to 0.3 with the higher values associated with comparisons of populations from the north‐west and south‐east of the island. A comparison of data sets for 1980 and 1986 revealed the allelic frequencies at five enzyme loci to be remarkabl

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04026.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The morphology and function of the masticatory apparatus in two armadillos,Dasypus novemcinctusandEuphractus sexcinctusare compared.Euphractus sexcinctus, a species restricted to South America, is omnivorous, eating a wide range of foods, including significant amounts of plant material and carrion.Dasypus novemcinctusis geographically the most widespread of all armadillos, ranging from northern Argentina into the United States. It is insectivorous‐omnivorous, apparently consuming whatever it encounters in the leaf litter. In South and Central America, this leads to a diet with a large proportion of ants and termites; in North America, the diet is considerably broadened. The teeth, jaws and jaw musculature ofE. sexcinctusare large and the configuration of the jaws maximizes force production.Dasypus novemcinctuspossesses derived morphology relative to the primitive condition in armadillos and exhibits many characteristics of ant and termite‐eating mammals, including reduced jaw muscles, teeth and facial bones. The apparent morphological specializations for myrmecophagy inD. novemcinctusdo not, however, constrain its diet to ants and termites. It is broadly omnivorous, especially in North America. Our data highlight the difficulties in predicting diet from morphological analysis and raise questions concerning the behavioural limits imposed by morphological specializat

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04027.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The mechanical properties of the bone material of femora of five wild polar bears, ranging in age from three months to seven and three‐quarter years, were compared with those of humans and axis deer. There are changes in mechanical properties in all three species with age, but their time course and extent vary greatly between species. The age‐related changes in mechanical properties are attributable mainly to changes in mineralization. At any age, the properties of the polar bear's bones lie between those of humans and the deer. The architecture of the bear's bones, and the mechanical properties of their bone material, were related to the weight of the bears. The calculated stresses in the bones, and their deflection under load, were relatively constant compared with the very large differences in the weights of the bears and the sizes of their bo

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04028.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Most previous research on metamorphosis of the musculoskeletal system in vertebrates has focused on the transformation of the skeleton. In this paper we focus on the transformation of the muscles of the head during metamorphosis in tiger salamanders (Ambystoma tigrinum) in order (1) to provide new data on changes in myology during ontogeny, and (2) to aid in interpreting previous data on the metamorphosis of function in the head of salamanders.The physiological cross‐sectional area of nine head muscles was calculated by measuring fibre angles, fibre lengths, and muscle mass in two samples of tiger salamanders obtained just before and just after metamorphosis. The major mouth‐opening muscles (rectus cervicis and depressor mandibulae) exhibit a significant decrease in estimated maximum tetanic tension (MTT) across metamorphosis of about 36%. The jaw‐closing muscles (adductor mandibulae internus and externus) and the head‐lifting muscles (epaxials) also decrease in MTT but not significantly. The muscles associated with tongue projection during feeding on land (the subarcualis rectus I, geniohyoideus, interhyoideus and intermandibularis) all show a slight increase in MTT at metamorphosis.Metamorphic transformation of feeding behaviour inAmbystoma tigrinuminvolves changes in performance, the design of skeletal elements, changes in muscle force‐generating capability, and changes in hydrodynamic design from unidirectional flow in larvae to bidirectional flow during aquatic feeding after metamorphosis. Although muscle activity patterns during aquatic feeding do not change across metamorphosis, tongue‐based terrestrial feeding involves a suite of novel muscle activity patterns, morphological characters acquired at metamorphosis, and a metamorphic increase in the masses of muscles important in tongue

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04029.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Stenolicmus sarmientoiis described as a new genus and species of the trichomycterid subfamily Sarcoglanidinae, from the RíAo Mamoré Basin, Bolivia. It can be distinguished from all other sarcoglanidines by: five‐rayed pectoral fin; elongate body shape (HL about 15% of SL); absence of fontanelles on cranial roof; well‐developed patches of opercular and interopercular odontodes (five or six on each bone); numerous accessory caudal‐fin rays (13 dorsal and 11 ventral); and presence of extensive dark pigmentation on the surface of the body. Three synapomorphies support a hypothesis that the new taxon forms a monophyletic group with other sarcoglanidines: presence of an anterior ossification of the palatine cartilage; quadrate with a dorsal expansion directed posteriorly; and premaxilla with a long lateral process.Stenolicmuslacks some synapomorphies shared byStauroglanis, MalacoglanisandSarcoglanis, and shares some other synapomorphies exclusively withSarcoglanisandMalacoglanis.These character distributions make it uncertain whetherStenolicmusis the sister group of all other sarcoglanidines or only ofMalacoglanisplusSarcoglanis, because the two positions imply equally parsimonious cla

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04030.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

It was shown in the mathematical model described elsewhere that when growth rate of the chicks is maximized and not constrained by the food availability, the optimal relationship between body mass and alimentary tract mass should conform to a single straight line, or two‐, or three‐segmented straight lines. Here, we present the data on growth of 11 bird species, and we test the model using the mass of intestines as an indicator of growth of the alimentary tract. The results support the predictions of the model for altricial species and contradict them for precocials. Since precocial species examined here were not food‐limited, we suggest that the lack of optimal growth of their alimentary tract is inherent to their mode of development. This may account for their lower growth rate, as compared to altricials. The existence of the optimal growth of the alimentary tract in altricial nestlings suggests that under natural conditions the food is much more abundant than it is generally as

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04031.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The arrival of Antarctic fur seals at a breeding beach on Bird Island, South Georgia, was studied over five consecutive breeding seasons, 1983 to 1987. Experienced bulls arrived first and established breeding territories on the beaches in anticipation of the arrival of the cows. Male arrival, which is less synchronous within years than female arrival, was significantly later in 1987 than in any other year. Female arrival, estimated by pup birth date where necessary, was highly synchronous; it usually started when 80% or more of potential territory sites were occupied by males. Cows arrived significantly later in 1984 and 1987 than in 1983, 1985 or 1986. The late arrival of both males and females in 1987 is attributed to unusually severe climatic conditions during the preceding winter. The late arrival and reduced fecundity of females in 1984 is attributed to markedly reduced food availability during the austral winter and summer of 1983. Males were not affected in 1984 because they could move away from the area of reduced food availability earlier than females and because they have a more varied diet. Factors influencing the winter distribution, the timing and pattern of arrival and the breeding of male and female Antarctic fur seals are discussed.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04032.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Photographic evidence shows that the ventral tube can be used as a tentacle‐like mechanical aid for self‐righting from an inverted position. It is proposed that the extraordinary length of the vesicles of the ventral tube in globular springtails has been evolved in order to combat postural instabilities resulting from spherical symmetry of body f

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04033.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Large non‐ruminant ungulates consume the more abundant low‐quality forage because this gives them the advantage of reducing search effort. However, large‐bodied herbivores would be predicted to search for high‐quality fruit patches if these patches were of large size and the fruits rich in nutrients. Diets of lowland tapir (Tapirus terrestris), a large non‐ruminant of the Amazon basin, were examined from animals of north‐eastern Peru to investigate this relationship between high‐quality fruit, lower‐quality browse and searching behaviour. Lowland tapir consumed on average 33% fruit, which is relatively high for a large non‐ruminant ungulate. The fruit portion of lowland tapir diets was dominated by the nutritiousMauritia flexuosa(Palmae) drupes, which were selected by tapir more frequently than other fruit types.M. flexuosapalms grow in virtually monotypic stands and occur in larger patches than other fruit trees used by terrestrial herbivores of the Amazon. Lowland tapir encountered fruits more frequently when ranging inM. flexuosapalm forests than in non‐palm forests, because they changed their searching behaviour once they entered palm forests by turning more abruptly. It appears that lowland tapir can consume greater proportions of fruit than other large non‐ruminant ungulates, because they exploit a nutritious fruit that occurs in large patches and that meets the energy demands of

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb04034.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY