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31.
WATER-REGULATORY BEHAVIOUR IN TERRESTRIAL GASTROPODS 总被引:3,自引:0,他引:3
DAVID J. PRIOR 《Biological reviews of the Cambridge Philosophical Society》1985,60(3):403-424
1. Terrestrial snails and slugs are exceedingly susceptible to dehydration due to evaporative water loss from the integument and lung surface, and the deposition of a dilute mucous trail. Active slugs can lose 30–40% of their initial body weight (IBW) within 2 h. 2. Both field and laboratory studies have revealed that habitat selection by snails and slugs is well correlated with the availability of water. In addition, numerous species display homing behaviour, returning directly to their moist secluded daytime resting sites at dawn. 3. Several aspects of locomotor activity are affected by body hydration and environmental conditions such as relative humidity. Moist conditions result in termination of aestivation in snails and a generally higher level of activity in both snails and slugs. In contrast, severe dehydration initiates aestivation in snails and an increase in the intensity and duration of circadian locomotor activity in slugs. 4. Huddling behaviour is a specialized example of the general preference of slugs for moist habitats. When groups of slugs are exposed to dry environmental conditions, they form closely packed aggregations. This response results in a decrease in the rate of dehydration of the individual slugs. 5. When slugs have been dehydrated to about 90% IBW, rhythmic closures of the pneumostome are initiated. As dehydration progresses there is a reduction in the open diameter of the pneumostome. These responses reduce the total exposure of the lung surface and thereby evaporative water loss. In slugs dehydrated to about 80 % IBW, these responses can result in a 7 % reduction in water loss. 6. When slugs have been dehydrated to about 65% IBW (67·6 ± 4·3% IBW) they move on to a moist surface, assume a characteristic flattened posture and remain quiescent while water is absorbed through the surface of the foot. Once they are rehydrated (to 93·5 ± 12·4% IBW) they move off the moist surface. Thus there exists a specific dehydration threshold for the initiation of contact-rehydration and a rehydration set-point at which the response is terminated. 7. Both initiation and termination of contact-rehydration are controlled by variations in haemolymph osmotic pressure. The behaviour can be experimentally initiated by injection of hyperosmotic mannitol solution and terminated by injection of dilute saline. 8. Contact-rehydration involves bulk flow of water through an epithelial paracellular pathway in the integument of the foot. The rate of absorption of [14C]inulin during contact-rehydration is similar to that of water. The efficacy of water movement through the pathway is modulated by body hydration, the pathway being opened only in dehydrated slugs. 9. By means of the dual-limit control of contact-rehydration slugs can behaviourally regulate their body hydration and haemolymph osmolality within the tolerable hydration range described by the upper and lower limits. 相似文献
32.
Improvements of jackknife confidence limit methods 总被引:1,自引:0,他引:1
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DAVID C. QUELLER 《Biological journal of the Linnean Society. Linnean Society of London》1984,23(2-3):133-143
Game theory models show that the evolution of interactions between relatives is determined by two kinds of fitness effects: Hamilton's inclusive fitness effect, and a frequency-dependent synergistic effect. The latter arises when an individual's behaviour has different effects on the fitness of interactants, depending on whether or not they perform the same behaviour. Knowing the sign of the synergistic effect is sufficient to understand most of the qualitative features of genetic models that show departures from Hamilton's rule. Since this synergistic effect does not depend on the interactants being related, it is best viewed as something distinct from kin selection. In this view, Hamilton's rule is basically correct for describing kin selection, and most deviations from it are due to the distinct process of synergistic selection. 相似文献
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An earlier proposed hypothesis by Straka & Lane (1970), suggesting 'Idiognathoides' noduliferus and Idiognathoides sulcatus as the progenitors of a closely related group of Lower Pennsylvanian (Morrowan) conodonts, is here considered as unnecessarily complex and based on insufficient data. An alternative and more simple interpretation is offered based on phylogenetic, ontogenetic, and stratigraphic considerations. It is suggested that the Idiognathoides sulcata (and/or I. opimus)-Idiognathoides sinuatus (and/or I. opimus ) group descended from Gnathodus defectus , and that Neognathodus bassleri was descended from Declinognathodus. Declinognathodus noduliferus and Gnathodus defectus are considered as having shared the common ancestor, Gnathodus girtyi simplex. 相似文献
37.
Nucleoside diphosphate kinase was a predominantly soluble enzymein lily pollen (Lilium longiflorum, var. Ace), and very littleenzyme activity was associated with the mitochondrial fraction.GTP was the preferred substrate when ADP was the second substrate.The enzyme was purified 18-fold to a specific activity of 7µmoles/min/mg protein.
1This study was supported by grant GB-8764 from the U.S. NationalScience Foundation. (Received October 5, 1970; ) 相似文献
38.
Ribosomes,G-factor and Siomycin 总被引:13,自引:0,他引:13
G-factor interacts with the 50S ribo-somal subunit at a site which is distinct from the peptidyl transferase centre and which is inactivated by siomycin. 相似文献
39.
Antigenic Heterogeneity of Human IgD Immunoglobulins 总被引:3,自引:0,他引:3
SUBCLASSES of the three major classes of human immunoglobulins, IgG, IgA and IgM, are recognized: four of IgG are well defined1,2 and at least two of IgA3–5 and two of IgM6,7 have been demonstrated. This communication presents evidence for the existence of an antigenic heterogeneity in the heavy chains of IgD, which may also be indicative of subclasses within this class of immunoglobulin. 相似文献
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