摘要:

Bimonthly live‐trapping over 15 months of 1 ha grid in the Menagesha State Forest, Ethiopia, revealed six species of rodents, dominated byPraomys albipes(64.3% of the catch). All age groups were recorded at each trapping occasion, and pregnant females were observed throughout the year. Both snap‐trapping and captive breeding programmes suggest a mean litter size greater than 4 (range 2–8). Despite this, the monthly density and biomass of captured rodents declined towards the last trapping occasions from 35 to 12/ha and 1546 to 454 g/ha, respect

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05375.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Mating in Schrcibers’long‐fingered bat (Miniopterus schreibersii) from central Zimbabwe (18°S) occurred between mid‐April and mid‐May, after a five‐month period of spermatogenesis. Implantation was delayed until early July and parturition occurred between late October and mid‐November, about four months after implantation and six to seven months after fertilization. The timing and length of gestation at 18°S are similar to that described forM. schreibersiifrom Zaire (11σS) and when these date are compared with those for the same species from higher latitudes in Africa, it is apparent that there is a small, but distinct, increase in the total length of pregnancy and the length of delayed implantation with increasing latitude. The reproductive bilogy ofMiniopterus schreibersiifrom Africa and France differs fundamentally from that of the same species from Australia and Japan, and it is suggested that studies of the relationship between latitude and duration of delayed implantation should be based on comparisons within single species from different latitudes on the same continent, and that comparisons between species and between continents sho

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05376.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A sightings survey was conducted in the summer of 1991 in the western Mediterranean to describe the distribution of fin whales and to estimate their absolute abundance during the summer feeding season. Fin whales were only found in the Liguro‐Provençal basin, in deep waters (mean depth 2,360, S.E.: 46.8 m), beyond the continental shelf. The highest densities of fin whales were found in relatively cool waters (mean = 23.9°C), and water in areas in which fin whales were found was significantly cooler than that in areas without fin whales. Patterns of distribution of whales, with remarkably high densities in the feeding grounds, and composition of schools, which were found to be smaller than in other regions, suggest that food resources for the species in the north‐western Mediterranean feeding grounds occur at higher densities but are more patchily distributed than in other fin whale feeding grounds so far studied. Abundance was estimated as 3,583 individuals (S.E.: 967; 95% CI: 2,130

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05377.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The subdermal connective tissue sheath (SDS) of dolphins is a fibre‐reinforced membrane connected to other locomotor tissues, including blubber, axial muscles and tendons, and vertebral column. The complicated connections between the SDS and other locomotor tissues suggest that the SDS acts as a peripheral skeletal element for the axial locomotor muscles and as an anchor for ade novodermal appendage, the dorsal fin. The morphology of the SDS suggests that the dolphin can be modelled as a fibre‐wound, thin‐walled, pressurized cylinder. Existing cylinder models predict that the SDS functions to resist torsional forces, prevent aneurysms, and limit wrinkling when the dolphin bends in locomotion. I present a new functional model that more accurately represents the morphology of the dolphin cylinder wrapped by the SDS. The new model predicts that the SDS: (1) acts as a retinaculum for the terminal tendons of the axial locomotor muscles; and (2) plays a role in maintaining the laterally flattened cross‐sectional shape of the caudal peduncle. The model is based on external morphological features of dolphins shared by other steady swimming aquatic vertebrates, such as carangiform and thunniform fishes. These features, which include a streamlined body shape and narrow necking of the caudal peduncle have been identified as adaptions to reduce drag. The new model offers insight into some of the structural features of the body wall required to maintain the hydrodynamicallytuned, external morphology of steady‐swimming ve

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05378.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

This paper discusses phenotypic plasticity of the avian intestine and presents data about the dynamics and mechanisms accounting for size variation of the avian intestine. Gut lengths of 56 bird species were compared for interspecific and intraspecific coefficients of variation. Intraspecific gut length variation relates to seasonal changes in quality and composition of food in some species. Such phenotypic plasticity is thought to adjust gut structure and function to seasonal differences in nutrition and to maintain optimized gut function under differing feeding regimes. Morphometry at five segments along the intestine provided basic measurements of the quail intestine. Whereas the duodenum can be separated from the rest of the intestine in almost all parameters, the small intestine, rectum, and caeca are rather uniform. Changes of circumference and length of the gut segments account for the major portion of size changes of the resorptive surface. BrdU/3H‐TdR double labelling experiments were performed to study the dynamics of cellular turnover of the intestine. The experiments revealed a constant S‐phase length of 6.5 hours along the intestine. The turnover time of the mucosa epithelium ranges between 9 and 17 days, depending on the circumference of the gut segment. Such a turnover time permits reconstruction of the intestine in short periods and its adjustment to seasonal differences in composition and quality of food. The study revealed significant differences between cell proliferation activity at day and at night. Animals labelled at night had almost twice the labelling index of those labelled during the day. These results were consistent in other tissues (liver, muscle, connective tissue, glandular stomach). Because high night‐time proliferation activity coincides with low antigen levels and high free radical scavenger concentration (e.g. melatonin),it is suggested that the circadian patterns in labelling index represent a fine tuning of DNA‐replication activity to ‘safer’per

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05379.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Craniometric variation between ottersLutra lutra(L.) from Ireland, Scotland, Shetland, Norway, and Czechoslovakia was examined using multivariate statistical analyses. Significant sexual dimorphism in cranial size and shape occurred in all samples, although the degree of dimorphism varied between samples, with the Irish sample exhibiting the most. Morphological differences were also observed across samples. Three groups were observed; Irish, Scottish, (Mainland and Shetland), and Mainland European, though within the two composite groups the samples were still differentiable. There was a good agreement between the patterns of variation between male and female samples, but morphological differentiation was not significantly correlated with geographic separation. These results are discussed in the light of our current knowledge of the ecology of the species in Europe. It is argued that, while there is morphological evidence for subspecific status of the Irish otter (asL. l. roensis), further investigations of morphological and genetic variation across Eurasia are clearly required.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05380.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A new species of suctorian protist epibiont of the mysidSchistomysis parkeriis described. The individuals show two types of adult form: elongated and flattened, both with 4‐8 tentacular lobes. This new suctorian differs from described species ofpro‐Ophryodendrongroup by size, number of tentacular lobes, insertion of the tentacles, union of the lorica with the body, shape of the macronucleus, number of micronuclei and the lack of stalk (adult forms). The life cycle of this species is analysed and a succession pattern of its different stages is propo

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05381.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

We studied the function of cheek‐rubbing in golden marmots (Marmota caudata aurea) by combining observations of the external morphology of the orbital gland, observational studies of marmots cheek‐rubbing, and experimental studies of marmots’responses to olfactory secretions from the orbital gland. Adult males had larger eyepatches–areas without hair above the orbital gland–than adult females. Both sexes produced sufficient glandular exudate to pool on the surface of the skin or fur above the orbital gland. Adult males cheek‐rubbed more than adult females throughout the summer active season, but both males and females generally cheek‐rubbed within 10m of a main burrow. Adult males responded more vigorously to the smells of non‐group members of both sexes than to group members of either sex. Adult females responded more vigorously to the smell of non‐group females than to non‐group males or group members of either sex. Our results are consistent with the hypothesis that marmot cheek‐rubbing functions to mark defended areas, possibly to minimize costs of ag

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05382.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Age and growth in the scorpaenidSebastes capensiswas studied at Tristan da Cunha and Gough Island using otoliths. The growth rate of specimens collected at Gough Island was almost twice that of specimens collected at Tristan da Cunha. The largest specimen from Tristan was aged at 18 years while similar‐sized fish from Gough were only 11 years old. Because the populations at the two localities were not considered to be genetically isolated from one another, it was hypothesized that the difference in the growth rate and longevity was related to site‐specific environmental conditions. Inshore sea temperatures were, on average. 3°C higher at Tristan than at Gough throughout the year. It is concluded that this temperature difference may affect growth rate indirectly through regulating diet and metabolic activity inS. capensis.Changes in reproductive strategy related to the level of environmental predictability at the two localities may also affect growth rate in this spe

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05383.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

To determine the duration and hormonal characteristics of the oestrous cycle in scimitar‐horned oryx, ovulation was synchronized in 11 females using exogenous progesterone and a prostaglandin analogue. Daily blood samples were taken from six animals during 46 days (with a 7‐day hiatus). The remaining five animals were blood sampled every 30 min for 6 h on three occassions druing 22 days, then resynchronized with prostaglandin analogue and pregnant mare's serum gonadotrophin and blood sampled daily for another 21 days (with a 7‐day hiatus). Behavioural observations were made on days 1 through 3 and 24 through 28 to determine the occurrence of oestrus.Only animals>2 years old (n= 7) had plasma progesterone concentrations indicative of luteal function, with a mean luteal phase progesterone concentration of 13.6 ± 3.3 (S.E.) nmol.l−1and a mean follicular phase concentration of<3.2 nmol.l−1. Mean duration of the oestrous cycle estimated from plasma progesterone profiles and behavioural data 22.7 ± 1.1 (S.E.;n= 7) days, range 17‐25 days. When estimated from behavioural data alone, mean duration of the oestrous cycle was 22.3 ± 0.3 (S.E.;n= 3) days, range 22‐23 days. Mean length of the luteal phase was 17.3 ± 0.6 (S.E.;n= 8) days, range 14‐19 days, and mean length of the follucular phase was 5.6 ± 0.5 (S.E.;n= 5) days, range 3‐7 days. Pulses in plasma LH concentration detected by Cluster analysis ranged from 0.34‐1.55ng.ml−1in animals ≷ 2 years old (n= 3), and from 0.17‐0.29ng.ml−1in animals<2 years old (n= 2), the difference in mean pulse height being significant (P2 years of age (n= 3), suggesting that these older animals adapted better to the stress of repeated sampling. Plasma cortisol concentrations also declined throughout the serial bleed but there was no difference in this decline between the two age groups.Results of this study define the duration of the oestrous cycle in scimitar‐horned oryx and show that its hormonal components are similar to the well‐characterized pat

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05384.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY