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271.
An herbivorous cichlid fish Cichlasoma (Theraps) nicaraguense has been reported to perform brood care for the fry of a piscivorous cichlid Cichlasoma (Nandopsis) dovii in a Nicaraguan lake. It was suggested that interspecific brood care (IBC) evolved to propagate C. dovii as a predator of another herbivorous fish Neetroplus nematopus, which is superior to C. nicaraguense in competition for breeding territory. However, it is still unclear how IBC is maintained in the face of cheaters that do
not provide IBC. In this study, to elucidate the conditions for maintenance of IBC, we developed a spatially structured model,
assuming a trade-off between reproduction and IBC (i.e., intra- and interspecific competition) and behavioral plasticity in
IBC. The model predicted the following maintenance conditions: the probability of expressing (or suppressing) IBC in response
to competitor invasion (or exclusion) is low, or, if the probability is high, then IBC is less effective for exclusion of
competitors. Furthermore, we also predicted that IBC can be maintained without spatial structure if it is plastic behavior.
Our model contributes to understanding of maintenance of IBC by providing empirically testable predictions. We discuss how
this model is applicable to more general relationships, such as those in competitive or mutualistic systems. 相似文献
272.
A new method for the isolation of smooth endoplasmic reticulumand tonoplast from etiolated mung bean hypocotyls (Vigna radiata[L.] Wilczek) has been developed. After centrifugation in aFicoli density gradient [5.5% (w/w) in 15% (w/w) sucrose] ofa crude microsomal membrane fraction (10,000156,000?gpellet) which had been prepared and resuspended in buffer systemsthat contained 0.25 M sorbitol, more than 80% of the total amountsof smooth endoplasmic reticulum and tonoplast were co-bandedat the interface between the sample load and the Ficoll layer,while most of the other cellular membranes, including plasmamembrane, Golgi membranes and yellow-colored membrane materials,which were presumably the etioplast envelopes, were sedimentedthrough the Ficoli layer. Smooth endoplasmic reticulum and tonoplastwere separated from each other to a high degree of enrichmentby a subsequent two-polymer phase partitioning. The separationis based on the principle that mung bean tonoplast has a highpartition coefficient for the polyethylene glycol-enriched upperphase and the smooth endoplasmic reticulum has a high partitioncoefficient for the Dextran-enriched lower phase. Assessed interms of degree of contamination by activities of membrane markerenzymes, the isolated smooth endoplasmic reticulum and tonoplastfractions were found to be highly purified. An ATPase sensitiveto neutral detergent and vanadate was found to be specificallyassociated with the smooth endoplasmic reticulum.
1Contribution No. 3172 from the Institute of Low TemperatureScience (Received April 22, 1988; Accepted September 28, 1988) 相似文献
273.
The effects of chilling on protein synthesis in vivo in etiolatedhypocotyls of Vigna radiata L. were investigated. After exposureof the tissues to 0?C for various periods of time, proteinswere labeled with [35S]-methionine at 26?C. The total amountof 35S incorporated into soluble and membrane proteins was reversiblyreduced by chilling for 24 h, during which time the tissuessuffered no injury. Further prolonged chilling produced an irreversibledecline both in the incorporation of radioactivity and in cellviability as assessed by the extent of leakage of electrolyte.The 35S-labeled proteins in the soluble and the total membranefractions were analyzed quantitatively. Chilling of etiolatedhypocotyls for one or two days induced the syntheses of twosoluble proteins (82 and 74 kDa) and one membrane protein (80kDa). Moreover, three heat-shock proteins (HSPs) that were inducedby heat stress (41 ?C, 4h) had the same electrophoretic mobilitiesas those of the proteins induced directly or indirectly by thechilling treatment.
1Contribution No. 3170 from the Institute of Low TemperatureScience. (Received April 22, 1988; Accepted September 30, 1988) 相似文献