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831.
SYNOPSIS. A symbiotic alga from the foraminifer Archaias angulatus was isolated axenically. Algae from crushed hosts were coccoid and highly vacuolated; division stages within an envelope were common. Biflagellate motile piriform organisms predominated in newly transferred cultures and were gradually replaced by the coccoid, highly vacuolated stage. Incorporation of 14C label in intact Archaias was greatest for organisms fed and incubated in light. Starved symbiotized organisms incubated in the light incorporated ~30% as much label as fed counterparts, There was no obvious difference in 45Ca incorporation between fed and starved organisms. Light significantly enhanced calcification. The Archaias symbiont infected Rosalina leei but not Quinqueloculina spp. 相似文献
832.
ABSTRACT. Silent‐site nucleotide diversity data (πsilent) can provide insights into the forces driving genome evolution. Here we present πsilent statistics for the mitochondrial and nuclear DNAs of Polytomella parva, a nonphotosynthetic green alga with a highly reduced, linear fragmented mitochondrial genome. We show that this species harbors very little genetic diversity, with the exception of the mitochondrial telomeres, which have an excess of polymorphic sites. These data are compared with previously published πsilent values from the mitochondrial and nuclear genomes of the model species Chlamydomonas reinhardtii and Volvox carteri, which are close relatives of P. parva, and are used to understand the modes and tempos of genome evolution within green algae. 相似文献
833.
ELLEN M. GOLDSTONE SHIB DAS BANERJEE JAMES R. ALLEN JOHN J. LEE S. H. HUTNER C. J. BACCHI JAMES F. MELVILLE 《The Journal of eukaryotic microbiology》1966,13(1):171-174
SYNOPSIS. Polysphondylium pallidum WS-320 grows indefinitely as vegetative amebae in a liquid medium where (a) substrates comprise sucrose, glycerol, acetate, lactate, citrate, and glutamate; (b) essential nutrients (riboflavin, lysine, glycine, and possibly several other amino acids that may be essential) are supplied. The growth thus supported (2 × 106 cells/ml) is more than doubled by provision of a mixture of crude fatty acids, an acid hydrolysate of casein supplemented with B vitamins, purines, pyrimidines, and fat-soluble antioxidants. 相似文献
834.
835.
A field and laboratory based bioassay has been developed to investigate the effects of the quantity and duration of simulated pollutant nitrogen (N) deposition on root-surface phosphomonoesterase (PME) activities in calcareous and acid grasslands. Seedlings of Plantago lanceolata were transplanted to a calcareous grassland and Agrostis capillaris seedlings were grown in microcosms containing soil from an acid grassland that had received either 7 yr (long-term) N additions or 18 months (short-term) N and phosphorus (P) additions. The bioassay revealed that short-term N treatments had little effect on the enzyme activity, whereas long-term N additions significantly increased PME activity within 7 d of transplanting into the field plots. Root-surface PME activity of A. capillaris was significantly reduced in soil that received additions of P. In the plots receiving long-term additions of N, a strong relationship was observed between extractable soil ammonium and root-surface PME activity. Soil ammonium concentrations accounted for 67% of the variation in PME activity of P. lanceolata in the calcareous grassland, and 86% of the variation in PME activity of A. capillaris in the acid grassland. These results provide evidence that N deposition may have considerable effects on the demand and turnover of P in ecosystems that are approaching or have reached N saturation. 相似文献
836.
Substrate discrimination by larvae of the sessile rotifer Ptygura beauchampi Edmondson 总被引:2,自引:0,他引:2
ROBERT LEE WALLACE 《Freshwater Biology》1977,7(4):301-309
SUMMARY. In an acid bog pond, the sessile rotifer Ptygura beauchampi was limited to the trap door areas of one of three distinct prey capturing organs of the carnivorous hydrophyte Utricularia vulgaris ; four other co-occurring congeneric species ( U. gibba, inflata var. minor, intermedia , and purpurea ) were not colonized. This pattern was not the result of differential capture of larvae by the prey traps. Laboratory settling experiments demonstrated that P. beauchampi larvae select this particular substrate to the exclusion of all others. This selectivity was independent of the presence of captured prey organisms in the traps.
P. beauchampi larvae select younger vestibules (trap door areas) over older ones. Observations of natural populations showed denser colonization of those slightly bigger traps closer to the plant stem. However, no relation was found between vestibular area and adult rotifer density. Selectivity for traps more proximal to the plant system was not demonstrated. In natural populations a distinct distribution of adults within the vestibule was noted. This pattern was statistically different from sites which the larvae colonize in laboratory experiments. Adult distribution is probably a modification of the larval settling pattern by site-dependent survivorship of adults.
Larval settling experiments showed that larvae select uncolonized vestibules over those previously colonized of approximately equal age. Settling outside the vestibule area was highest on traps closest to the plant stem and was related to the density of adults colonizing the vestibule.
The adaptive significance of larval selection of a particular substrate is discussed. 相似文献
P. beauchampi larvae select younger vestibules (trap door areas) over older ones. Observations of natural populations showed denser colonization of those slightly bigger traps closer to the plant stem. However, no relation was found between vestibular area and adult rotifer density. Selectivity for traps more proximal to the plant system was not demonstrated. In natural populations a distinct distribution of adults within the vestibule was noted. This pattern was statistically different from sites which the larvae colonize in laboratory experiments. Adult distribution is probably a modification of the larval settling pattern by site-dependent survivorship of adults.
Larval settling experiments showed that larvae select uncolonized vestibules over those previously colonized of approximately equal age. Settling outside the vestibule area was highest on traps closest to the plant stem and was related to the density of adults colonizing the vestibule.
The adaptive significance of larval selection of a particular substrate is discussed. 相似文献
837.
838.
ABSTRACT. Adults of Hippodamia convergens Guerin-Meneville (Coleoptera: Coccinellidae) form massive overwintering aggregations in the Sierra Nevada Mountains of California. These diapausing pre-reproductive adults may remain in the aggregations for up to 10 months. Beetles were collected from overwintering sites in Nevada County, California, and held at 4C for 6 weeks. In order to simulate the winter to summer transition, the beetles were transferred to 20C and 68% r.h. under a LD 12:12h cycle. Supercooling points increased slightly from - 16C on day 0 to - 12.9CC on day 21. In contrast, low temperature tolerance decreased markedly within 2 weeks. On day 0 nearly all beetles survive 2 h of exposure to - 5C, whereas only 50% survived this treatment on day 4. These data demonstrate the general lack of correlation between the supercooling point and the lower lethal temperature in warm-acclimated beetles. Within 1 day of transfer to 20C, oxygen consumption decreased by 26%. This decrease continued through day 14 when the rate of oxygen consumption had decreased to 40% of initial values. Beetles acclimated to 20C selected temperatures significantly higher than cold-acclimated beetles. The parametric shifts observed in this study are consistent with a physiological transition from cold-hardiness and energy conservation during winter to one of dispersal, feeding and reproduction in summer beetles. 相似文献
839.
LEE KF 《Public Health Reports》1952,67(5):474-478
840.