山东潍县武家村第四纪地层及哺乳类化石

本文根据武家村发现的第四纪哺乳类,海、陆相软体类化石,以及地层中所含的植物孢粉和岩性特征,把该地区第四纪地层初步划分为全新统、晚更新统、中更新统(陆相沉积)和早更新统(海相沉积)。     

Analysis of Crop Losses in Tomato Due to Pratylenchus penetrans

The effects of Pratylenchus penetrans upon yields of ''Veebrite'' tomato were studied at initial soil population densities (P_i) of 360, 2,010, 4,580, and 14,360 nematodes/kg of soil in 20-cm (i.d.) clay-tile microplots. The lowest P_i appeared to stimulate fruit production. Higher P_i''s suppressed fruit production (total weight of marketable tomatoes and numbers of intermediate- and large-sized fruits), in comparison to control yields, the highest P_i resulted in 38% fewer fruits which weighed 44% less. These losses were at least partly due to a delay in fruit ripening, caused by the nematodes, which did not become apparent until the fourth week. Nematode populations in the soil increased at all but the highest P_i; final populations were around 7,000/kg of soil. Nematode populations in roots ranged from 230-590/gm of root at the completion of the experiment. Nematode control by fumigation would definitely be warranted at soil population densities of 2,000/kg or higher; with 500-2,000/kg, the decision to fumigate would depend on soil type and economic and hiological factors.     

Fine structure of early previtellogenic oocytes in Mugil (Liza) auratus Risso, 1810 (Teleostei,Mugilidae)

Summary Sequential cytological events at the onset of previtellogenesis were studied in oocytes from 12 m to 70 m in diameter of golden grey mullet. The main cytological changes observed (increase in size of cell, nucleus, nucleolus and increase in number of nucleoli, RNP particles, nuage and mitochondria) provide evidence for important synthetic processes in an early preparatory phase of oocyte development.Somatic cells (pre-follicle, follicle and thecal) are also described.     

A brief review on the development of stronglid nematode eggs and larvae under constant and changing temperature conditions-I. Egg development

The present work gives a brief review on the major aspects of the effect of constant and changing temperatures on the development of stronglid nematode eggs. The effect of culture media on the range of temperatures at which the eggs may hatch as well as the rate of their hatching is also included. In addition, a revision of resistance of the eggs to low and high temperatures is also tackled.     

Assimilatory sulfur metabolism in marine microorganisms: Sulfur metabolism,protein synthesis,and growth of Pseudomonas halodurans and Alteromonas luteo-violaceus during unperturbed batch growth

Analysis of the distribution of ³⁵S-sulfate and ¹⁴C-glutamate in major biochemical components of the two marine bacteria, Pseudomonas halodurans and Alteromonas luteo-violaceus, was compared with cell density and total cellular protein during exponential growth in batch culture. For both organisms, the sulfur distribution was restricted principally to the low molecular weight organic and protein fractions, which together accounted for over 90% of the total sulfur. Carbon was more widely distributed, with these two fractions containing only 70% of the total label.Growth rate constants calculated from increases in cell numbers, protein, and ³⁵S and ¹⁴C in the various fractions indicated nearly balanced growth in A. luteo-violaceus, with constants derived from all biosynthetic parameters agreeing within 5% during the exponential phase. In contrast, protein synthesis and ³⁵S incorporation into residue protein constants were 30% higher than constants derived from cell counts and incorporation of ¹⁴C in P. halodurans. Therefore the cellular protein content P. halodurans varied over a two-fold range, with maximum protein per cell in the late exponential phase. A distinct reduction in the rate constants for total protein and ³⁵S incorporation into residue protein foreshadowed entry into the stationary phase more than one generation before other parameters.Incorporation of ³⁵S-sulfate into residue protein paralleled protein synthesis in both bacteria. The weight percent S in protein agreed well with the composition of an average protein derived from the literature. Sulfur incorporation into protein may be a useful measurement of marine bacterial protein synthesis.Abbreviations L.M.W. low molecular weight - TCA trichloroacetic acid - CFU colony forming unit     

Autoinduction of bacterial bioluminescence in a carbon limited chemostat

Several strains of four species of luminous marine bacteria were maintained in a chemostat at a constant dilution rate and a variety of steady state densities by carbon (glycerol) limitation in order to study the relationship between culture density and bioluminescence activity. In general, luminescence per cell was constant at high culture density, and decreased dramatically at low culture density. For Vibrio fischeri, luminescence decreased to nondectable levels when the culture was maintained at low density; such dark cells were stimulated to synthesize luciferase and became luminous within minutes when purified autoinducer was added to the chemostat. Two strains, Photobacterium phosphoreum NZ11D and Photobacterium leiognathi S1, did not show the decrease in light intensity at low culture density that was characteristic of all other strains tested; they appeared to be constitutive for bioluminescence.Abbreviations BCM basal salts glycerol medium - BM basal salts medium - BSA bovine serum albumin - D dilution rate - DTT dilitiothreitol - LU light unit=2×10¹⁰ quanta s^-1 - OD optical density - SWC sea water complete medium - specific growth rate     

Factors affecting entomophilic activity of Neoaplectana feltiae in mushroom compost

The host-searching ability of Neoaplectana feltiae Filipjev (= S. bibionis Bovien) (Nematoda: Steinernematidae) in response to larvae of a mushroom fly, Lycoriella solani Winn. was examined in a mushroom substrate. Individuals of L. solani were less attractive for the parasite than larvae of Galleria mellonella L. The nematode juveniles penetrated a 22 cm layer of casing mixture within 2–4 days. In the casing alone nematode effectiveness was better than in mushroom compost or in compost and casing together. In the casing mixture parasite dosages of 20 and 100 juveniles per cm² led to 22% and 45% parasitization of L. solani respectively, while all G. mellonella larvae were parasitized at both dosages. The prevalence of nematode infection depended on the content of water in the mushroom substrate. The highest N. feltiae infectivity was observed, when the ratio of the dry casing weight to the weight of water content was 1: 2.5. The practical aspects of the observed phenomena, essential for the use of N. feltiae in the protection of commercial mushroom cultivation are discussed.     

The nematode fauna of a temperate Australian mangrove mudflat; its population density,diversity and distribution

The nematode fauna of an estuarine mangrove Avicennia marina mudflat in Southeastern Australia has been intensively studied. About 85% of the nematodes occur in the top cm of soft mud, but 5–7 species inhabit the deeper anoxic mud down to 10 cm, both at low and high tide. One square metre was intensively sampled from four zones with different nematode faunas. At the low tide zone 58% of the nematodes were epistrate feeders, including many diatom-feeders, but in the mangrove zone selective microbial feeders made up over 60% of the population, while between high water neap and high water spring, above the mangrove zone, omnivore/predators and plant root feeding nematodes increased in relative importance. Random replicate cores reliably sampled species occurrence, but gave a high variance in density estimates. Replicate aliquots from homogenised mud gave lower density variance. Nematode densities (maximum 5 × 10⁶ m^-2) were not as high as have been reported from non-mangrove estuaries in other countries, but were within the range found in mangroves elsewhere in Australia. Margalef Species Richness values ranged from 1.7 to 3.89, which is similar to values found in other mangroves mudflats in Australia. Nematode biomass ranged from 888 mg dry weight m² (383 mg C m^-2) at the low tide zone to 19 mg dry weight m^-2 (8 mg C m^-2) at the upper tide level.     

^137Cs,^134Cs在人工海洋小生境中的行为

在自行建立的人工海洋小生境中,采用示踪法综合地研究~(137)Cs、~(134)Cs在人工小生境中的行为。结果表明,~(137)Cs和~(134)Cs具有共同的生理生态行为,并表现出相似的规律、沉积物对~(137)Cs、~(134)Cs的吸附能力甚低,~(137)Cs、~(134)Cs在海洋动物体内趋于全身性的分布。各主要生化物质均能检出~(137)Cs、~(134)Cs。排泄实验后,海洋动物的胃肠、肝(消化腺)~(137)Cs、~(134)Cs损失显著。沉积物表现为解吸-重吸附的过程。