摘要:

Data on the population dynamics of tropical isopods in general, and those inhabiting forests in particular, are scarce. Consequently, the population dynamics of three sympatric isopods,Burmoniscus ocellatus(Philosciidae),Formosillo raffaeleiandOrodillo maculatus(Armadillidae), were studied at two neighbouring sites in a mixed forest in Hong Kong between March 1985 and December 1986. Isopod population densities varied with the species, site and season, with mean densities ranging from 100–150 m‐2.Burmoniscus ocellatusandF. raffaeleihad a single recruitment peak per year, whileO. maculatushad two. Results of the present study revealed that air temperature was the main factor explaining seasonal variations in population density, while rainfall exerted its effect with a two‐ to three‐week time‐lag, depending on the species studied. Approximately 20% ofFormosillo raffaeleiandO. maculatussampled were found infected byRickettsiellabacteria. The possible influence of pathogens, and other biotic factors, on the dynamics of the Hong Kong isopod populations was

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb06030.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The stages of permanent tooth development observed in radiographs of the mandible were described for known‐aged fallow deerDama dama. Ten stages were defined and, by allocating scores for these stages, the scores that may be expected for a particular age have been identified. Lastly, the predicted age was given for total molariform scores. These were obtained, with 95% prediction intervals, from a regression of age on total molariform scores. An age assessment from tooth development stages can be made up to three years, after which, no further development takes plac

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb06031.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

In the summer of 1987 a project was initiated to study certain aspects of the environmental impact of tunnelling for the Channel Tunnel. The study areas were situated in East Kent between Dover and Folkestone. At one of the chosen study sites, a male and female of the linyphiid spiderMinicia marginella(Wider), hitherto unknown from Britain, were taken in pitfall traps. Both sexes of the species are described and illustrated from the British material.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb06032.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The diet of coypu (Myocastor coypus) on two sites in a managed marsh was investigated by field observations and microscopic analysis of faeces. The habitat is mainly grazing pasture and over 51% of the plant fragments recovered from faeces were leaves of Graminaceae. Other food included hydrophytes, Cyperaceae, dicotyledons, flowers and seeds of Graminaceae and various roots. The mean annual diet of coypu was similar at both sites and showed moderate interannual variations. Relative proportions of different foods varied with season and availability. Hydrophytes, mostly Lemnaceae, were preferentially selected in late summer and autumn. Coypu fed on roots during winter, particularly in periods of exceptional food shortage due to flooding and severe frost. Even when crops were available, coypu utilized a wide range of food. The study shows the importance of feeding strategy in the ability of coypu to colonize new habitats, particularly those which are man‐mad

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb06033.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Saliva was collected from the parotid glands of anaesthetized common wombats (Vombatus ursinus) to ascertain the maximal flow rates, salivary composition and possible adaptations to the diet. After temporary catheterization of the parotid duct through the oral opening, salivary secretion was evoked by ipsilateral intracarotid infusion of acetylcholine at varying rates to produce salivary flow rates ranging from 0.017±0.0012 ml.min‐1(0.62±0.037 μmin‐1.kg‐1body weight) to 2.00±0.148 ml.min‐1(70.5±3.21 μl.min‐1kg‐1body weight). The concentrations of Na (22.2±5.50 to 107.0±5.2 mmol.1‐1) and H+ (12.5±1.73 to 17.4±1.40 nmol‐1‐1) were positively correlated with salivary flow rate. The concentrations of K (99.3 ± 6.51 to 13.7±0.62 mmol.1‐1), Ca (1.36±0.229 to 0.74±0.021 mmol.1‐1), Mg (1.14±0.092 to 0.03±0.002 mmol.1‐1), HCO3(65.3±2.43 to 55.7±1.70 mmol.1‐1), PO4(3.30±0.334 to 0.51±0.038 mmol‐1‐1), protein (2.08±0.284 to 0.49±0.084 g.1‐), amylase activity (6.75±1.515 to 1.97±0.538 mkat.1‐1) and urea (10.9±0.89 to 3.88±0.28 mmol‐1‐1) were negatively correlated with flow rate. The relationships between salivary flow and C1 concentration or osmolality were diphasic: negative at low flows and positive at high flow rates. The patterns of excretion of the major anions in the saliva differed substantially from those reported for parotid glands of other marsupials. The saliva had levels of amylase activity which were far higher than those of other marsupials and which may be an adaptation to a diet rich in carbohydrate. Salivary Na/K ratios were not decreased by high‐rate intracarotid infusion of aldosterone (80–100 μg.h‐1for 4 h) which indicated that the wombat gland, like the parotid glands of macropods, requires chronic

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb06034.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The coelomic cavity of freshly collectedHolothuria poliispecimens contains a variable number of brown pigmented and unpigmented encapsulating structures. They are composed of nodules with entrapped parasites and an internodular mass which comprises a number of nodules. Both brown and unpigmented bodies occur in different size classes depending upon the number of nodules accumulated in a complete body. The unpigmented bodies probably represent an early unmelanized stage of the brown ones.The nodule was ultrastructurally constituted by foreign bodies surrounded by a fibrous, electron‐dense, non‐cellular layer, probably melanin, followed by a layer of elongated and extremely flattened amoebocytes. Nodules were assembled in an internodular mass formed by amoebocytes type I, II and III spherule cells. As for the amoebocytes constituting the nodule, those present in the spaces between nodules did not develop junctional complexes. It is conceivable that the intricate network established among the cell processes could represent the mechanical force maintaining the whole structure.As suggested by our results, two functional amoebocyte populations seem to be responsible for the organization of the scavenger body: 1. encapsulating amoebocytes, characteristically non phagocytosing, elongated cells; and 2, phagocytosing amoebocytes. The former organize the nodules, the latter constitute the internodular mass of several nodules.Most probably, the double scavenger activity justifies the considerable complexity of theH. poliiencapsulating structure compared to other invertebrates.Spherule cells participate only in constituting the internodular m

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb06035.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Three specimens of the rare giant squid (genusArchiteuthis, 18 nominal species) are described from the waters around southern Africa. Consideration of their internal and external morphology, including beaks, radula, statocyst and statolith give no reason to suppose that the three specimens do not pertain to the same species. A standardized data collection form and a summary of existing morphometric data are presented for the first time and the morphology and systematics of the genus are discussed. The value of various systematic characters is examined and certain guidelines are proposed, with an appeal for a more scientific approach toArchiteuthisstudies.Features of the internal anatomy, including the female reproductive tract, are described and illustrated and the beak dimensions are used to evaluate existing regression formulae for beak and body parameters. The statocyst and statolith are described and illustrated in full, the statolith for the first time, and are compared with those of other squids.The value of recent data from trawl‐caught specimens, as well as indirect evidence, is cited to replace speculation in discussions on distribution and habitat. Our specimens suggest that the waters off the south‐western coast of Africa may be one of the natural habitats ofArchiteurhis, during both feeding and spawning periods of the life cy

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb06036.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The venom glands ofHeteropneusteslie deep in the epidermis at the sides of the pectoral fin spines, and consist of large cells that react positively to histochemical tests for proteins, histidine and tyrosine, negatively to periodic acid‐Schiff and for serotonin and bombesin. The venom cells are of two types, appearing to have dense or lucent cytoplasm when seen by electron microscopy. The dense type has the better developed Golgi systems, the lucent type has more ribosomes. Both appear to differentiate from the basal layer of the epidermis. The epidermis over the glands has a zone with relatively few desmosomes and enlarged intercellular spaces. Both staining reactions and fine structure differentiate the venom gland cells from the club cells of the epidermis, to such an extent that they must be considered distinct secretory element

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb06037.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Hamilton&Zuk (1982) hypothesized a positive correlation between a species' sexual showiness and its level of parasitic infection. We tested the hypothesis in 26 species of lizards, members of a class of vertebrates never before used to test the model. The prevalence of parasites was determined using published lists of parasites found in wild lizard populations. An index of showiness (brightness) was derived by scoring photographs of lizards in natural settings. Contrary to expectations of Hamilton&Zuk (1982), we found an inverse correlation between a lizard species' brightness and parasite prevalence. No correlation was found between a species' brightness and the number of parasite genera, species, or percentage of individual infecting parasite taxa. These results are discussed in relation to other interspecific tests of the hypothesis.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb06038.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Wet and dry calorific values (energy densities) and total energy content of lesser sandeelAmmodytes marinus, spratSprattus sprattus, Atlantic herringClupea harengus, whitingMerlangius merlangus, saithePollachius virensand codGadus morhua, were measured. Calorific values varied both within and between species. Larger fish tended to have higher calorific values than small ones, particularly when considered in terms of wet weight, but there was considerable temporal variation. The calorific values and body weights of sandeels larger than 10 cm showed marked seasonal trends and in consequence the total energy content of a sandeel of given length in summer is approximately double the spring value. The calorific values of herring and sprat also varied from month to month but seasonal cycles were less obvious. Whiting varied least. Both calorific values and total energy content of individual sprat were very variable in summer (the spawning season of this species). Because there is so much intraspecific variation, care must be taken when assessing the relative merits (in terms of energy) of different species as prey. The practical difficulties of obtaining reliable data on wet calorific values are discussed and the use of dry calorific values and dry weight/length relationships is recommended.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb06039.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY