摘要:

Several investigators have described in some crocodilians a row of round or oval organs, called dorsal glands, lying under scutes on each side of the dorsal midline. The function of these glands is unknown, but they are hypothesized to produce skin‐conditioning secretions. We investigated the anatomy and histochemistry of the dorsal glands of adult American alligators (Alligator mississippiensis). Twenty to 22 pairs of glands containing a viscous, often black, material were observed lying from the mid‐cervical to the anterior caudal regions in the axial musculature or on the inner surface of the dermis. The capsule of each gland consists of dense collagenous fibres and numerous short elastic fibres, and is surrounded by skeletal muscle. The single lumen is lined by one to several layers of cuboidal to columnar epithelium in varying stages of degeneration, indicating a holocrine secretory mode. The epithelial cell membranes often interdigitate and tight junctions and desmosomes occasionally are observed between them. The epithelial cells and secretory product contain slight to considerable amounts of lipid; glycoproteins may be present. Crystals exhibiting a dense core and/or layering occur in the epithelial cells and secretory product. Energy‐dispersive X‐ray analysis demonstrates calcium, copper, iron, lead, potassium, and zinc in the crystals. Mitochondria, vacuoles, and short segments of rough endoplasmic reticulum also occur in th

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05466.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The pattern of chick feeding of the British storm‐petrelHydrobates pelagicusin a Mediterranean colony was examined by weighing chicks at 24‐h intervals on different days during the nestling period. In order to calibrate daily mass increments (NET) against number of feedings, daily mass changes of chicks were regressed upon the sum of positive mass increments recorded overnight (SUM) during four nights. The average meal size delivered to chicks per night by one parent was 3.5 ß 1.3 g or 12% of adult weight. This was insufficient for sustaining constant chick mass during a day. On average 85% of chicks were fed each night, and the mean interval between feeds was 1.2 ß 0.5 nights. Nightly feeding frequencies differed among days, but this night‐to‐night variation was not related to meteorological conditions. Both food requirements necessary for chick body maintenance (zero‐growth) and meal size were relatively constant for ages up to 59 days. However, feeding frequency decreased throughout the fledging period, accounting for agespecific variation in growth rates until fledging. Food requirement and feeding patterns at Benidorm were different from North Atlantic colonies. None the less, growth patterns were almost identical, suggesting adjustment to maintain chick body mass at a determined level, as food delivery to nestling appears to be regulated to chicks’nutritional

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05467.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The sizes of total brain, the five fundamental brain parts, and certain telencephalic structures were measured in wild mink (Mustela vison energumenos) and ranch mink of a Dark Standard strain of the same species. By means of intraspecific allometric methods for analysing the relationship between brain weight and body weight (net carcass weight), the volumes of the brain parts were compared in both groups. In general, total brain, as well as all the parts measured, were smaller in size in ranch mink independent of body size, age, and sex, indicating that domestication has led to a decrease in size. There were differences in the amount of decrease in various brain parts. These are discussed in connection with domestication time, with comparable results obtained in other species, and with regard to the functional importance of the brain parts.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05468.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Males of the beeAmegilla dawsoni(Anthophorini) vary greatly in size, with some of the largest individuals as large as the largest females, a rare phenomenon in insects. The occurrence of unusually large males appears to be the product of sexual selection for fighting ability. As predicted from this hypothesis: (1) males regularly competed aggressively to be in the best position to mount sexually receptive, virgin females as they emerged from the ground; (2) larger males usually won fights for potential mates, as demonstrated by the fact that males able to defend sites with an emerging female were larger on average than males they kept at bay; (3) the fighting advantage of large males translated into greater mating success. Males captured while mounted on a female were significantly larger on average than randomly captured matesearching males in two of three populations sampled in 1993. Moreover, males known to mate more than once were consistently larger than single‐mating males in the 10 samples taken from four populations examined in 1994. Thus, a large male mating advantage applies across years and among populations, making it potentially advantageous for females of Dawson's burrowing bees to produce large, superior fighting sons about the same size as their daughter

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05469.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Nuptial flights ofTermitophilomyia zimbraunsiwere observed over three years (1990‐1993) near the open chimney of anOdontotermes transvaalensismound in Harare, Zimbabwe. Copulating phoretic pairs landed on the chimney; males quickly disengaged and flew away whilst females ran inside the vent and tore off their wing membranes. Agitated termite workers and soldiers swarmed the rim in a partially successful physical attempt to expel the phorids; the termites appeared to anticipate the threat of invasion. After acquiring the scent of the nest, female phorids ran underground to lay their large single eggs, probably in the hosts’fungus gardens. Nuptial flights occurred throughout the year but only in the early mornings, peaking in the hot dry season and being least in the hot wet season. The flights were highly temperature dependent (15.0‐17.9 °), usually occurring at relatively low light intensities but across a wide range of humidities. Phoresy and sexual dimorphism in wings, mouthparts, food and division of labour inT. zimbraunsiare discussed, as is its termitophilous habit and the responses of termites to it.Although the females ofMesopathusa modestaare apterous, nuptial flight behaviour is very similar to that ofT. zimbraunsi.Neither phorid is host‐specific, both species having been found on bothOdontotermes latericiusandO. transvaalensismounds, althoughM. modestais more common onO. laterici

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05470.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Testes externalized in a scrotum are found only in those mammals whose present lifestyle (or that of their ancestors) involves jumping, leaping or galloping, thereby creating concussive hydrostatic rises in peritoneal pressure. This would be expected to expel the contents of the reproductive tract since it does not possess a sphincter. The lower temperature of the externalized testes is then seen as a secondary adjuvant adaptation to a cooler location than within the body cavity. The theory also explains the close phylogenetic relationship between the Proboscidea, Hyracoidea, and Sirenia, if it is assumed that their common ancestor was not endowed with the genes necessary for externalization.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05471.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Slender‐tailed meerkats (Suricata suricatta) are small, diurnal, and gregarious mongooses which inhabit the semi‐arid regions of southern Africa. In the south‐western Kalahari, substantial fluctuations in productivity are caused by extreme seasonality in rainfall and temperatures. We observed the foraging behaviour of habituated meerkats from January to July, a period covering the entire birth season and stages of high and low prey availability. Insects were the most frequently occurring prey class (78.1%), of which larvae (33.4% total frequency) and adult Coleoptera (27.5% total frequency) were the most important prey items throughout the year. Reptiles were heavily utilized in terms of prey bulk‐an index of volume‐(19.9%), but not by frequency (9.2%). Consumption of Coleoptera was positively correlated with rainfall, and negatively with temperature. Meerkats used a mean of 6.7 ± 1.1 prey categories daily, and there were significant monthly differences in prey diversity in the diet. Dietary shifts were apparently related to fluctuations in prey availability and the presence of preferred prey. There were no differences between the sexes in dietary diversity or niche breadth, but pregnant and lactating females foraged at significantly higher rates than males. The timing of foraging activity altered over the months in response to changes in daylength and thermoregulatory constraints. Foraging behaviour and seasonality in foraging effort are described, and the implications of an insect prey base for meerkat socioecology are

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05472.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A population of wood mice,Apodemus sylvaticus(L.), was studied by capture‐mark‐recapture, in five 0.81 ha grids within a habitat mosaic produced by the felling of a plantation of mature Sitka spruce (Picea sitchensisCarriere). From May 1990 to June 1992, we estimated population sizes, survival (total and by weight classes), recruitment, and home‐range sizes, usually at monthly intervals, for the study area taken as a whole. Inter‐grid movements were frequent for both sexes, supporting the assumption that the population could be analysed in this way. Wood mice were more abundant in 1991 than in 1990, associated with increased seed supply. In both years, numbers were low in spring and increased gradually towards an autumn peak, which was of similar size in both years. Male home‐range areas varied seasonally, and were negatively correlated with population sizes, while female home ranges showed little seasonal variation. Survival and recruitment both declined sharply in late autumn, apparently in a densitydependent way. Except for this latter result, the population dynamics in a heterogeneous coniferous woodland were consistent with those described previously for this species in more homogeneous deciduous woodlands, suggesting that the same regulatory processes are operating in both

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05473.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Natricine colubrid snakes, including the grass snake,Natrix natrix, are frequently involved in complex social behaviour during the reproductive season. During these social behaviours, several males may simultaneously court a single female, resulting in a ‘ball’of mating snakes in which each male ‘combats’with rival males by ‘tail wrestling’(see Madsen&Shine, 1993). I performed some experiments in outdoor enclosures for testing the male‐male competition and the determinants of mating success in male grass snakes involved in such ‘ball’aggregations. I demonstrated that competition between males occurred both when a single female was available to multiple males and when two females were simultaneously available to males. The larger males achieved more copulations than the smaller ones, thus demonstrating that body size is a crucial determinant of the individual mating success. It was not clear which aspect of male body size is the most important in determining success in these mating ‘balls’, but it was evident that the age of the ‘fighting’male was not correlated with mating success. Larger females attracted more males than smaller ones, both in the field and in the enclosure. Furthermore, when the size difference between available females in the cage was high, only the largest femal

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05474.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Data from four radio‐tracked female otters (Lutra lutra) were used to describe the temporal and spatial patterns of resting‐sites by the species along the south‐west coast of Portugal. Two female otters were tracked during 24‐h periods, showing a continuous resting period in daylight, whereas during the night there were several hunting bouts in the sea interspersed with periods ashore. These otters spent most of the time each day in daytime rest‐sites (72.1%), and devoted only a small time to hunting (18.3%) and other activities (9.6%). The onset of fishing activity was monitored for three animals, starting on average 45.4min after sunset; this was largely independent of the degree of human disturbance close to the rest‐sites. Most rest‐sites were located within dense thickets ofRubussp. along coastal and estuarine streams, and sometimes they were near areas disturbed by human activities. Three otters were captured along the coast and they were found in eight daytime rest‐sites on 116 occasions, each otter using regularly a small number of sites (2.7); the mean re‐use rate of sites was high (9.5 days per site), and the sites were spread over 4.2‐15.0km of coast, with 0.20‐0.71 sites/km. One otter was captured in an estuarine stream, where she was found on 70 occasions in 13 daytime rest‐sites spread over 6.0 km of streams; the density of rest‐sites was 2.2 sites/km and the re‐use rate was 5.4 days/site. The results of this study suggest that rest‐sites are scarce for marine‐feeding otters in south‐west Portugal. This is probably because rest‐sites used by these otters have an obligatory association with freshwater sources, and these are infrequent and scattered along this coast. Conservation impli

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05475.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY