摘要:

From the seasonal occurrence of 11 stranded nconates, the earliest and latest observations of possible calving behaviour, and the seasonal incidence of calves in shore‐based counts, the extent of the calving season for southern right whales off South Africa can be characterized as from late June to late October, with a peak in August. The occurrence of 89 ‘new’ calves located during monthly photogrammetric flights between July or August and November indicated that 50% were born by 1 September in 1988 and by 15 August in 1989, and that the effective calving season (in which 95.5% of calves are estimated to have been born) lasted 118 days in each year. From regression analysis of the lengths of 221 foetuses and their dates of death, and assuming a mean date of birth of 24 August, the duration of the linear phase of foetal growth is estimated to be 325 days, and the mean size at birth 6‐1 m. Uncertainty over the duration of the initial, non‐linear phase of foetal growth results in alternative estimates of 357 or 396 days for the total length of gestation. Foetuses of smaller females seem to be conceived later (or experience a longer initial, non‐linear phase of foetal growth) than those of larger females. The apparent rarity of adult females in coastal waters in the year in which they are presumed to conceive is attributed to either a brief residence time or the possibility that conceptions may occur well outside coa

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01567.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Przibram's Rule of growth in hemimetabolous insects is derived from average values for the ratios of mean weights (2–09) and mean lengths (1–29) of successive instars in mantids. Adult males of the jumping spiderZygoballus rufipesPeckham&Peckham (Araneae, Salticidae) were shown to be dimorphic, while adult females were monomorphic. The male body weight distribution was bimodal, with two distinct body‐size classes (morphs). A method was developed for testing the null hypothesis that an observed ratio of two means is equivalent to a previously derived null ratio. The observed ratio of mean weights for the two male morphs ofZ. rufipes(2–12) was not significantly different from the value for Przibram's Rule for weight (2–09), suggesting that males matured at two different instars. The body‐size dimorphism found in males was consistent with the existence of two size‐based alternative life‐his

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01568.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Gonadal structure and cellular composition were examined in juveniles, males and females of the protandric hermaphrodite,Amphiprion melanopus.Functional sex change was experimentally induced in the field and gonad structure was histologically examined both qualitatively and quantitatively at 10, 20, 30 and 45 days after its initiation. Juvenile gonads consist primarily of immature ovarian tissue. Functional male gonads are ovotestes with co‐existing mature spermatogenic tissue and immature ovarian tissue, while females possess only ovarian tissue. The initiation of sex change is marked by a rapid maturation of spermatogenic tissue and proliferation of putative oogonia. Gonads were essentially female by 20 days into sex change, but evidence of mature female function (marked by the initiation of vitellogenesis) was not observed until 45 days. Considerable variation between individuals was seen in quantitative measures of gonadal change in the early stages of sex change, but not in later stages. Progress in sex change as indicated by histological indicators was, however, consistent within stages. Duet systems for gamete transport changed from the male to the female form after all male tissue had been replace

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01569.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The serratus ventralis in mammals is a fan‐shaped scapulo‐thoracic muscle that is believed by most morphologists both to support body weight and to rotate the scapula during quadrupedal locomotion. Electromyographic studies of this muscle in cats, dogs and opossums confirm the dual supportive and rotatory roles of the serratus ventralis. Although this muscle has been studied in several primate species, the concentration on arboreal locomotion has resulted in an inadequate data set to permit direct comparisons to non‐primate terrestrial quadrupeds. In order to provide a more comparable data set, we examined cranial, mid‐ and caudal thoracic regions of the serratus ventralis during terrestrial quadrupedalism in the vervet monkey,Cereopithecus aethiops.Our results indicate that the serratus ventralis does support the body during the stance phase of quadrupedalism in this primate. However, unlike several non‐primate mammals, it plays a relatively insignificant rotatory role during sw

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01570.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Many animal connective tissues are composite materials formed into sheaths containing regularly organized collagen fibres in a crossed, fabric‐like array. From a few simple assumption about the interactions between fibres, we construct a model for the effect of such a fabric‐like construction on the Poisson's ratio of connective tissue sheaths. Surprisingly, the model predicts high Poisson's ratios (often greater than 1.0) Mdashespecially high given the value of 0.5 that is usually used for primarily aqueous biological tissues (based on assumptions of incompressibility and anisotropy). However, virtually all empirical attempts to measure Poisson's ratio in animal connective tissue sheaths (including our own experiments on salamander skin) reveal similarly high Poisson's ratios. The model also predicts that Poisson's ratio will increase with increasing strain, at a rate dependent on the initial angle of the crossed fibres relative to the direction of strain. Since the Poisson's ratio of a material is directly correlated with the material's stiffness, such strain‐dependent changes in Poisson's ratio have important implications for the stiffness properties of connective tissue sheaths. Given the structural support role of connective tissues, stiffness is assumed to be one of their most important qualities, and several examples of how our model might predict the stiffness qualities within the walls of cylinders formed from helically wound crossed fibre sheaths (such as mammalian annular ligament and nematode cuticle) are

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01571.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Relative movements of the main wing areas around the major flexion lines are compared during wing folding at rest, and during the supinatory phase of the flight cycle, which involves considerable wing deformation. Folding of the wing apex at rest is achieved by a combination of movements around the median flexion line (the main longitudinal flexion line), the principal transverse fold, and a variety of smaller, oblique ‘tucking’ folds. During flight, wing tip deformation is strongly influenced by elastic forces involved in the normal wing folding and unfolding processes. Those beetles possessing an inwardly sprung wing apex display partial folding at supination, associated with the temporary relaxation of the forces opposing spring recoil. These beetles also show enhanced mobility about the median flexion line which facilitates leading edge supination. The presence of the principal transverse fold may help to concentrate ventral flexure towards the wing tip. The wings of beetles possessing an outwardly‐sprung apex are much less affected by the presence of the flexion lines associated with folding. In these cases, enhanced supination of the leading edge, in the face of an overall increase in wing membrane stiffness, may be related to the presence of the highly‐sclerotized pter

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01572.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Annual variations in resting metabolic rate (RMR) and body temperature(Tb)were measured in the streaked tenrecsHemicentetes nigicepsandH. semispinosus.RMR in non‐reproducing, non‐torpid adults was lower than predicted by the Kleiber (1961) curve, supporting Genoud's (1990) hypothesis on BMR in hibernating mammals. Both species demonstrated a reduction in RMR andTbduring the austral winter and these changes were independent of body mass.H. semispinosusfrequently roused from torpor to forage whereasH. nigricepsremained dormant throughout the winter, This contrast in activity patterns may result from altitudinal differences in species distributions.H. nigricepsmay be an obligate hibernator whereasH. semispinosus,living at lower, warmer altitudes, may be a facultative hibernator. It is proposed that the ability ofH. semispinosusto remain active during favourable climatic conditions allows winter breeding and increases annual reproductive out

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01573.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Examination by scanning and transmission electron microscopy (SEM and TEM) has found no actual taste buds in the mouth ofRaja clavata.Prominences of the epithelium on the roof and floor of the mouth, and on the oral valves, contain large numbers of innervated bipolar cells, not associated in the form of taste buds, with a cytology intimating that they have a chemosensory function. The apices of these sensory cells, each bearing a group of microvilli, protrude between the superficial epithelial cells. Neurite profiles are associated with the sensory cells; synaptic specializations are marked by a cluster of vesicles with inconspicuous dense cores and some densities on the cell membrane. Shrunken, electron‐dense, cell profiles are interpreted as apoptotic. Shrunken sensory cell profiles are commoner than similar epithelial cells, especially in young individuals, indicating a relatively rapid turnover of sensory cells. The epithelium contains a variety of granulocytic leucocytes, some of which contain large phagosome

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01574.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Although body size in reptiles has important consequences for their ecology, it is quite variable in most species, presumably because growth in these animals is influenced by many factors. In this study, we analyse the effects of family membership and sex on first‐year growth of garter snakes(Thamnophis elegans)held under identical conditions in the laboratory. Litters, but not the two sexes, differed significantly in mean size at birth. Larger snakes ate more food and had a higher absolute (but not relative) growth rate in length than smaller snakes. Thus, there was significant variation in length increase among litters, but not between the sexes. All else being equal, variance in size at birth could contribute significantly to variance in adult body siz

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01575.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The relationships between the main abiotic environmental variables, food availability, dict, activity and home range size of the fox in a Mediterranean mixed pinewood were assessed. Food habits were determined by faecal analysis on a weekly basis. Food availability was measured by weekly censuses. Radio‐tracking allowed the detection of fox movements and activity. Individual differences shown by a sample of four radio‐tagged foxes were analysed. Juniper berries(Juniperus oxycedrus)were the staple of the diet during the year, except in summer. Insects, mainly nocturnal Orthoptera and cicada larvae(Cicada orni),were the main prey in the warm season. Large vertebrates, mostly wild boars(Sus scrofa),were scavenged in winter. In the warm season foxes' activity depended largely on the pattern of activity of prey. Food habits tended to depend on food availability, which, in turn was mainly influenced by temperature. In spite of habitat similarity, individual differences in food habits were detected within the same season. Home ranges were larger in pinewood than in neighbouring heterogeneous habitats. Individual home range sizes were: (i) directly correlated to Orthoptera abundance and distribution; (ii) inversely correlated to the abundance of cicada larvae in diet. Resident males may exist in fox society, exploiting other males' territories when good clumped food resources are availa

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1994.tb01576.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY