摘要:

The anatomy of one species of neolepetopsid limpet,Eulepetopsis vitrea(Order Patellogastropoda, Suborder Lepetopsina), is described, and this is followed by comments on differences shown by four other members of the Suborder,Neolepetopsis occulta, N. densata, N. gordensisandParalepetopsis fioridensis.These limpets possess features linking them directly with limpets from other habitats, in this case with patellogastropods. Shared external features relate to the shallow pallial cavity with no gill; the single fold of the mantle edge, which is sensory, glandular, and has a respiratory function; in the gut the presence of inner as well as outer lips, with a strongly arched dorsal jaw associated with the former; the absence of an epipodium; and the cavity of the protoconch sealed from that of the teleoconch by a septum. The relationship displayed by internal anatomy is even more striking: the docoglossate radula and licker; the oesophageal glands forming a series of pouches, each with its own opening to the oesophagus; the stomach a simple ciliated sac lacking gastric shield, sorting area, and caecum; the enlarged initial part of the intestine; the orientation of the chambers of the heart, which is not traversed by the rectum; the lack of haemocyanin; the opening of the gonad directly to the base of the papilla of the right kidney; the absence of secondary sexual structures; the small left kidney displaying characters of a nephridial gland; and the degree of concentration of the main ganglia and the arrangement of the visceral loop. This aggregate of characters shows that the neolepetopsids cannot be separated from patellogastropods.The radula of the neolepetopsid differs from that of other patellogastropods in its unmineralized and articulating teeth and in the presence of a rachidian: the first feature appears to be a derived character and the other two ancestral. These radular differences contrast with the anatomical homogeneity exhibited not only here but throughout the patellogastropods. Such anatomical differences as do occur are most easily explained as mosaic evolution.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb06013.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The reproduction of 37 species of bats from Malawi was investigated, and the strategies (litter size and chronology) of seven species were determined. Reproduction was then related to rainfall and (if possible) abundance of food. Strategies of Malawian bats were compared with strategies of bats from six other African environments with different patterns of rainfall and availability of food. Monotocous species are numerous and found in all environments, but there are few polytocous species and polytocy has not been recorded in some environments. Ten reproductive chronologies (distinguished by the timing of parturition in relation to season, the presence of reproductive synchrony, the number of pregnancies/year, and the presence or absence of postpartum oestrus) were recognized in African bats. The number and kind of chronologies occurring in different environments is variable. Four chronologies have been recorded in fruit‐bats; intraspecific variability is rare, possibly because fluctuations in the abundance of fruit are comparatively small in the environments where most species of fruit‐bats are found. Reproductive inflexibility may explain why most fruit‐bats do not exploit diverse environments. Eight chronologies have been recorded in insect‐eating bats. These bats show more interspecific and intraspecific variability than fruit‐bats, probably because seasonal differences in the availability of insects are great enough to impose considerable selective pressure on reproduction. Species capable of reproductive flexibility exploit diverse env

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb06014.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The eruption of the large deciduous upper canines in the nimravid sabretooth catBarbourofeliswas delayed until after the individual was eating meat. This inference is based primarily on the eruption sequence and dental wear displayed by seven specimens referred to this genus. It indicates that the sabres were not required for feeding and suggests that these teeth were primarily killing devices. The deciduous upper canines inBarbourofelisand the permanent canines in large felids probably erupted at similar stages of dental ontogeny. If the potential for independence from adults occurs with the eruption of canines that were large enough to serve as killing devices, the delayed eruption of the deciduous sabres in nimravids did not necessitate any significant extension to the long period of parental care that is typical of the extant Carnivora.SummaryThe eruption sequence of, and patterns of wear to, the dentition ofBarbourofelisdemonstrate that juveniles were processing meat before the eruption of the deciduous sabres and thus the upper canines were not necessary for feeding. This supports the view that the sabres were preferentially killing devices; any use of the sabres in dismemberment of the carcass by adults was probably secondary. The transfer of these inferences to felid sabretooths such asSmilodonmay be unwise; however, arguments thatSmilodon'ssabres were inefficient slicing devices (Simpson, 1941), and the patterns of wear on its incisors and cheekteeth (Miller, 1969; Akersten, 1985), suggest that a similar scenario is likely. The marked modifications to the morphology and eruption sequence of the dentition inBarbourofelismay not have resulted in any significant increase in the length of parental care.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb06015.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Post‐weaning behaviour of southern elephant seals,M. leonina, was studied at Marion Island. Duration of fast in both sexes increased in direct proportion to weight at weaning, while it decreased with weaning date in males. Both sexes appear to fast until they have reached a lower weight ‘threshold’ of around 70% of weaning weight. Local dispersion after the fast was studied by resighting tagged animals at weekly intervals. Only 460 (7.0%) resights out of 6530 involved a move between sites, representing 378 (16.8%) of the 2246 pups that were tagged. Males moved more frequently between tagging sites and covered greater distances than females. Moves between sites are more frequent and distances travelled are greater in December than November. Differences in dispersion patterns between Marion Island and lies Kerguelen may be caused by differences in coastal configuration. Underyearlings spent 105.0±19.6 days at sea before returning for between 10 and 20 days in the autumn. Weaning weight had no effect on likelihood of hauling out in autumn. Movements between sites during the autumn haulout are infrequent and no fidelity to birth site is evident at this

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb06016.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Post‐capture decision rules and the mechanisms and constraints controlling these rules were examined in a New Zealand crab spider,Diaeasp. indet.Diaeaenvenomates prey, principally in the head and thorax, and injects the total amount of venom it uses to immobilize prey within 15 s of the prey being captured.Diaeainjects a larger volume of venom into larger prey, which demonstrates that this species can regulate the amount of venom injected.Diaeausually feeds from two sites on the prey—initially the head, then the posterior abdomen. Prey envenomated in the thorax or abdomen are re‐oriented by the spider so it can begin feeding from the prey's head. During feeding the exoskeleton of the prey remains intact.Diaeainitially mixes digestive fluid, secreted from itsmidgut, with the contents of the prey. Fluid is then extracted from the prey using suction provided by the combined action of pharyngeal muscles and a sucking stomach. The sucking phase of feeding generates a pressure deficit (vacuum) within the prey and alternates with a relaxing phase, during which the spider stops sucking and the extracted fluid flows back into the prey. Both the sucking and relaxing phases lengthen as increasing volumes of fluid move between the spider and the prey. Reflux of fluid into the prey allowsDiaeato mix digestive fluid with parts of the prey that are not in the immediate vicinity of the spider's mouthparts. Fluid is refluxed at an increasing distance from the spider's mouth as the lengthening sucking phase increases the vacuum within the

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb06017.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Mesoseiulus robertsin.sp. is described fromBactrothripssp. (Insecta: Thysanoptera) found on dead mango leaves in Cameroon.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb06018.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Eggs and embryos (up to the unilaminar blastocyst stage) were collected from grey short‐tailed opossums,Monodelphis domestica, at known time intervals after mating. Some were fixed immediately for examination by light and electron microscopy while others were maintained in culture at 37 °C in 5% CO2in Ham's F10 medium containing foetal calf serum. Cleavage to the early blastocyst stage was obtainedin vitroalthough most embryos displayed arrested development at the eight‐cell stage. From gross morphological and ultrastructural observations a pattern of embryogenesis to the unilaminar blastocyst was constructed. Comparisons were made with the events of early development in other marsupials.SummaryOocytes were fertilized soon after ovulation and their zonae pellucidae surrounded by a mucoid layer originating from mucopolysaccharide secretion of oviductal epithelial cells. Within 24 hours zygotes passed into the uterus and shell membrane formation commenced.1The early embryonic developmentin vivoand in culture of the grey short‐tailed opossum,Monodelphis domestica, was investigated by light and electron microscopy. The following timetable of events was constructed:2The first cleavage at about 28 hours after ovulation (54 hours after mating) was at right angles to the equator of the zygote and was accompanied by the vesiculation of yolk mass. The resulting two blastomeres were composed of peripheral polar cytoplasm.3The second cleavage (44 hours) and third cleavage (approx. 72 hours) produced small blastomeres with no cell contact. Yolky vesicles surrounded the blastomeres.4The fourth cleavage division (approx. 96 hours) occurred in the same equatorial plane as the second resulting in two tiers of cells which subsequently flattened against the inner surface of the zona pellucida. Tight junctions formed between adjacent blastomeres.5Unilaminar blastocysts were formed about 5 days after fertilization.6Developmentin vitrofollowed a similar time course to thatin vivo, however, most embryos were arrested at the 8‐ce

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb06019.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Variation in the diet of wood mice,Apodemus sylvaticus, was investigated in two contrasting habitats, deciduous and coniferous woodland, over 26 months and in 10 additional sites trapped during winter. Stomach contents were categorized as seed, fruit, green plant, root and animal material. Diet was evaluated using the percentage occurrence of each food type. Age and sex differences in diet occurred infrequently. Seed predominated throughout but was especially prevalent in autumn and winter. There was a peak in the incidence of animal material in the spring and early summer. Animal food was generally more frequent in mice caught in conifer plantations than in deciduous woodland during the longer‐term study. Further, mice from the additional coniferous habitats had greater percentage occurrence of animal food than those from the additional deciduous sites. There was a negative, non‐linear association between relative population size and diet in these winter samples. This suggests that spatial variation in numbers ofA. sylvaticusis dictated by food availability and density is locally food limi

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb06020.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The thymus in muntjac and fallow deer, as well as in sika (Cervus nipponand red (Cervus elaphus, has both cervical and thoracic portions. Foetal development of the gland in muntjac, fallow and sika is rapid and occurs relatively earlier than in the red fox, the only other mammal for which comparable data are available. Between birth and one year the thymus weights of muntjac and fallow fawns do not change significantly, but from then onwards there is a decline in weight and by six years of age the gland is very small.The thymus of muntjac appears to be less responsive to sexual changes than that of fallow and it is suggested that this may be related to the fact that muntjac breed at all times of the year. The thymus response in deer is perhaps less clear‐cut than in other mammals for which we have information and the relationship of the gland to sexual state merits further investigation.Thymus involution occurs with old age and also with trauma and many other stresses experienced by deer in the wil

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb06021.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1990.tb06022.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY