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441.
Hermit crabs are unique among crustaceans in that they choose their shell and can, therefore, be used to investigate apparent preferences for the presence of epizoic fauna. These may be beneficial due to increased protection from predators via enhanced crypsis but may also make the shell more difficult to carry. The effects of encrusting fauna on the physical properties of empty gastropod shells, the shell preferences of hermit crabs and the physiological costs of shell carrying were examined in the present laboratory study. Heavily encrusted shells weighed more than shells of the same internal volume that were free of epizoic fauna, hermit crabs showed a clear preference for un-encrusted shells and those that occupied encrusted shells had elevated haemolymph lactate in comparison to those supplied with un-encrusted shells. Under laboratory conditions, any benefit from increased crypsis is, therefore, outbalanced by the increased costs of carrying encrusted shells. 相似文献
442.
443.
Eve?McDonald-MaddenEmail author Mark?A.?Elgar Kathrine?A.?Handasyde 《Behavioral ecology and sociobiology》2004,56(4):322-327
The costs of reproduction are widely recognised as a major selective force in the evolution of various behavioural and life-history characteristics. In particular, the behaviour of reproductively active animals is likely to change when breeding increases risk of predation. We investigated the effect of an experimentally derived threat on the vigilance and escape behaviour of female Trichosurus caninus with and without dependent offspring and at different stages of offspring development. Females with offspring showed a heightened response to the threat in comparison to females without offspring. In addition, females with offspring displayed a stronger response at earlier stages of their offsprings development.Communicated by P. Bednekoff 相似文献
444.
Indirect Effects of Feral Horses on Estuarine Communities 总被引:1,自引:1,他引:1
Phillip S. Levin ‡ Julie Ellis Rachel Petrik Mark E. Hay† 《Conservation biology》2002,16(5):1364-1371
445.
446.
Diet induced differences in carbon isotope fractionation between sirenians and terrestrial ungulates
Carbon isotope differences (Δ13C) between bioapatite and diet, collagen and diet, and bioapatite and collagen were calculated for four species of sirenians,
Dugong dugon (Müller), Trichechus manatus (Linnaeus), Trichechus inunguis (Natterer), and the extinct Hydrodamalis gigas (Zimmerman). Bone and tooth samples were taken from archived materials collected from populations during the mid eighteenth
century (H. gigas), between 1978 and 1984 (T. manatus, T. inunguis), and between 1997 and 1999 (D. dugon). Mean Δ13C values were compared with those for terrestrial ungulates, carnivores, and six species of carnivorous marine mammals (cetaceans = 1;
pinnipeds = 4; mustelids = 1). Significant differences in mean δ13C values among species for all tissue types were detected that separated species or populations foraging on freshwater plants
or attached marine macroalgae (δ13C values < −6‰; Δ13Cbioapatite–diet ∼14‰) from those feeding on marine seagrasses (δ13C values > −4‰; Δ13Cbioapatite–diet ∼11‰). Likewise, Δ13Cbioapatite–collagen values for freshwater and algal-foraging species (∼7‰) were greater than those for seagrass-foraging species (∼5‰). Variation
in Δ13C values calculated between tissues and between tissues and diet among species may relate to the nutritional composition of
a species’ diet and the extent and type of microbial fermentation that occurs during digestion of different types of plants.
These results highlight the complications that can arise when making dietary interpretations without having first determined
species-specific Δ13Ctissue–diet values.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
447.
Jonathan Mark Wilson Alexandre Leitão Ana Filipa Gonçalves Catarina Ferreira Patrick Reis-Santos Ana-Violeta Fonseca Joana Moreira da Silva José Carlos Antunes Cristina Pereira-Wilson João Coimbra 《Marine Biology》2007,151(5):1633-1645
The Anguillid juvenile glass eel must deal with the osmoregulatory consequences of highly variable environmental salinities
on its recruitment migration from coastal to fresh waters. Changes in ionoregulatory parameters and branchial ion transport
protein [Na+/K+-ATPase, Na+:K+:2Cl− cotransporter (NKCC), cystic fibrosis transmembrane regulator (CFTR) anion channel, V-type proton ATPase] expression (activities,
protein and/or mRNA level expression and/or cellular localization) in response to acclimation to a broad range of ionic strengths
[distilled water (DW) to hypersaline water (HSW; 150%) sea water (SW 32‰)] was studied. The estuarine glass eels were very
euryhaline and successfully acclimated to acute changes in environmental ionic strength from 50% SW, with high mortality only
observed in HSW (51%) and sublethal osmoregulatory indicators (whole body water content and sodium levels) disturbed at the
extremes (DW and HSW). Central to a high salinity acclimation were elevated branchial Na+/K+-ATPase, NKCC and CFTR expression. At lower salinity, Na+/K+-ATPase expression was maintained and NKCC and CFTR expressions were reduced. Branchial chloride cells increased in size up
to SW but decreased in HSW. During hypotonic disturbance (DW), no compensatory elevation in V-ATPase or Na+/K+-ATPase expression was observed. 相似文献
448.
ROH Mark S DE BENEDETTI Laura JOUNG Young Hee LEE Nam Sook 《应用与环境生物学报》2007,13(2):145-151
Germplasm collection is important to preserve and maximize genetic diversity for germplasm conservation. Tsuga dumosa ( D. Don) Eichler in Engler & Prantl. and T. chinensis var. forrestii (Downie) Silba germplasm was collected from three localities in China: Mt. Yulong, Wenfeng Temple and Mt. Dishiergu, Yunnan Province. Accessions were identified based on morphological characters and RAPD markers. The shapes of the apices and margins of needles were examined, and the length and width of needles, cones and seeds from accessions of mature plants were used to compare the morphological differences and to identify the germplasm. Molecular markers generated by randomly amplified polymorphic DNA (RAPD) were also used to characterize the taxa. Although the clustering based on RAPD markers was inconsistent with the morphological characters of the needles, based on the overall morphological characters and on RAPD markers, the accessions from Mt. Yulong and Wenfeng Temple were identified as T. chinertsis var. forrestii, and those from Mt. Dishiergu identified as T. dumosa. Taxonomic identification of the accessions was made based on morphology and by RAPD markers concurred. The results indicate that the shapes of the apices and margins of needles particularly from young plants could not be used as a possible key to identify T. dumosa and T. chinertsis var. forrestii. Fig 6, Tab 3, Ref24 相似文献
449.
Contests often occur between members of the same sex when they compete for access to mates, but inter-sexual contests may
occur over access to other essential resources such as food or shelter. Despite the possibility that such contests are common,
most studies focus on male fighting, and very few have analysed fights between males and females. Because males and females
differ physically and physiologically, fighting ability or resource-holding potential (RHP) may also be subject to inter-sexual
variation. In this study, we investigate size-controlled inter-sexual contests over the ownership of empty gastropod shells
in the hermit crab Pagurus bernhardus. During these fights, there are two roles, attacker and defender, and we use a fully orthogonal experimental design to compare
the performance of males and females in each role, when fighting either a male or female opponent. Although females fight
more intensely, male attackers have an advantage when compared to females playing the attacker role, as they are more likely
to evict the defender from its shell and thus win the resource. Further, in the defender role, male defenders are subject
to shorter attacks than female defenders. The differences in agonistic performance could not be attributed to differences
in perceived resource value between the sexes or to differences in body or weapon size. There are clear differences in the
agonistic behaviour of males and females, and this possibility should be incorporated into models of contest behaviour. In
particular, evolutionarily stable strategies may be expected to vary with sex ratios. 相似文献
450.
We used a replicated sampling program to examine the use of roadside corridors as habitat by native mammals. Our procedure compared the abundance and diversity of mammals in remnant forest, pasture, and two types of roadside corridor. Fixed transects were established in these four habitat types at six replicate sites. Spotlight, live-trap, and daytime observation surveys were used as census techniques. Few mammals were detected in pasture, and spotlighting revealed a higher total density of mammals in corridors than in forests, indicating corridors provide important habitat. Nevertheless, the number of species using corridors distant to forest was less than that in the corridors close to forest and the forest patches. Different species did not utilize corridors in the same way. We also found intraspecific differences in habitat use by one species of small mammal (Antechinus stuartii), which may have implications for the value of corridors to this species. Specifically, there was a higher proportion of males, and individuals of both sexes had lower body weight in corridors than in forests. Our study demonstrates that corridors can provide useful habitat for mammalian assemblages, but may not provide a complete solution to the problem of landscape fragmentation. 相似文献