Internuclear Genetic Transfer in Dikaryons of SCHIZOPHYLLUM COMMUNE. II. Direct Recovery and Analysis of Recombinant Nuclei

The recessive gene, mound (mnd), allows the appearance of globose masses of compacted hyphae. Dikaryons of Schizophyllum commune that are heteroallelic for mnd [(mosaic dikaryons: (mnd + mnd(+))] have been successfully dedikaryotized in cholate-containing medium in order to recover the component nuclear types directly. The relative proportion of the two recovered monokaryotic types shows in all cases a marked deviation from 1:1. Hyphae from nonmound mycelial regions yield monokaryotic types identical to those originally used to form the dikaryons. In hyphae from mound-forming regions, however, homoallelism of the mnd allele has been demonstrated; the nuclear type that formerly contained the mnd(+) allele acquired a mnd allele.-The process of internuclear transfer or recombination is unaccompanied by the simultaneous alteration of any additional genetic markers carried by the recipient nucleus. The newly acquired mnd allele segregates in Mendelian fashion in subsequent outcrosses and appears to be chromosomally located. A novel process of somatic recombination, with several features distinct from classical parasexual mitotic recombination, appears to be in operation.     

Seasonal fluctuation of zooplankton populations in lower Delaware Bay

Quantitative zooplankton samples were obtained monthly or bi-monthly 15 times from June 1974 to May 1975 at three stations in lower Delaware Bay. Two 12-hour cruises were also conducted at one of the stations.Arthropods dominated the samples in terms of number of species and number of individuals. The number of zooplankton from surface samples ranged from 58/m³ in August to 21,092/ m³ in June, while bottom samples varied from 259/m³ in August to 30,395/ m³ in October. In general, larger concentrations of individuals were found in bottom samples.Only on three occasions did meroplankton exceed the holoplankton, and these occurred at the shallow water stations. Meroplankton comprised a larger percentage of the bottom samples than surface samples. Zoeae of Neopanope sayi and Uca sp. contributed mainly to the large proportion of meroplankton in July 1974, veligers of Mytilus edulis in January 1975, and nauplii of Balanus sp. in May 1975.Copepods were the largest component of the population throughout most of the year. At all stations and depths, Arctica tonsa dominated most of the summer samples. In the spring of 1975, A. tonsa was replaced by Centropages hamatus, Temora longicornis, and Pseudocalanus minutus.During the 12-hour cruises there were higher numbers of individuals in the bottom waters in the day with migration to surface waters in the afternoon and evening. Based on cluster analysis, five time-related assemblages were discerned: June, July–August, September–November, December, January–May. Comparison of Delaware Bay zooplankton with other estuarine systems indicated that the densities obtained locally were most similar to those reported in the York River, Virginia.     

Release of outer membrane fragments from normally growing Escherichia coli

A complex containing lipopolysaccharides, phospholipids and proteins is released into the culture medium by Escherichia coli during normal growth. It can be separated from the medium by gelfiltration on Sephadex G-200 or by centrifugation. Electron microscopy revealed that this material is released as vesicles and membrane fragments. To determine the origin of these fragments, they were compared to outer and cytoplasmic membranes with respect to keto-deoxyoctulosonic acid, phospholipid, and protein content, phospholipid composition, fatty acid composition, protein distribution on sodium dodecyl sulfate-polyacrylamide gels, buoyant density, and content of several membrane marker enzymes. The results of this comparison indicate that the membrane fragments found in the culture supernatant of normally growing Escherichia coli consist of practically unmodified outer membrane. Possible mechanisms as to the cause of the release of outer membrane fragments, and its relationship to cell-division, are discussed.     

Analysis of structural variations in a shallow estuarine deposit-feeding community

Changes in the structure of an estuarine, subtidal, benthic deposit-feeding community have been investigated. Three quantitative samples were taken within a grid 10 m on a side every four weeks from May, 1971 to July, 1973. Each sample was washed over a 250 μm sieve. Streblospio benedicti Webster, Capitella capitata (Fabricius), Heteromastus filiformis (Claparède), Potydora ligni Webster, and Paranais litoralis (Müller) were the five dominant species on the basis of their total abundance, percentage occurrence, and biological index value. Repeatable cycles in diversity were observed for Fager's scaled standard deviation and scaled information measure, as well as for Lloyd and Ghelardi's equitability, but not for the unsealed information theory measure. McNaughton's dominance index was strongly inversely correlated with all diversity measures. Graphical measures of lognormal skewness and normal kurtosis, as applied to Whittaker's dominance diversity curves, followed repeatable cycles, whereas normal skewness and lognormal kurtosis did not. A strong relationship between Fager's scaled standard deviation diversity, dominance, and the degree to which resources were being shared by the deposit-feeding segment of the community was suggested. A decrease in average niche width and average niche overlap was observed as the community developed during the period of strong larval recruitment.     

Observations on the Bolbitiaceae – 23. Interesting Danish members of the family

Conocybe huijsmanii Watling, C. elegans Watling and C. parvula Dossing & Watling are described as new species. Bolbitius lacleus J. E. Lange is redescribed and neotypified, and C. utriformis P. D. Orton is recorded for the first time for Denmark. Short notes on a collection agreeing with Jakob E. Lange's interpretation of Pholiota brunneola and on Danish material of Agrocybe firma (Peck) Singer are offered.