A study of the karyotype of a population of banded killifish (Fundulus diaphanus) from the Hudson Rive

Studies were carried out to find appropriate techniques for securing a suitable karyotype from a population of Fundulus diaphanus in the Hudson River and to compare it with a published karyotype of a population of the same species from the New Haven, Connecticut area. A modification of the basic method of Denton & Howell proved to be a simple, effective and inexpensive approach for acquiring numerous and distinct chromosomal spreads for detailed karyotype analyses. The two karyotypes were identical in modal number, arm number and number of submetacentrics; however, they differed in numbers of acrocentrics and secondary constrictions. These differences may indicate incipient chromosomal evolution with the two distinct environments acting as selective agents. Preliminary work was carried out with banding techniques; the modified Denton & Howell method with banding appears to be an effective and promising direction for fish cytogenetics.     

Polypeptide composition of rat high density lipoprotein: characterization by SDS-gel electrophoresis

The histones synthesized by three different interspecies hybrid echinoid embryos have been examined. In all three crosses, the species-specific F1 histone of the paternal parent is found in the chromatin of the hybrid. These findings provide direct evidence for the involvement of newly transcribed mRNA in the synthesis of this protein. F1 histone is a unique protein in that it is the only paternal protein detected in these hybrids. The possibility that the synthesis of histones is controlled differently from that of other proteins is discussed.     

Colonization and succession of benthic macroinvertebrates in a new reservoir

The purpose of this study was to examine the colonization and succession of benthic macroinvertebrates in shallow areas (<7 m) of Lake Anna, a new mainstream impoundment in the southeastern U.S.A. Benthic macroinvertebrates were sampled for the first three years after filling by means of artificial substrates placed on the bottom and retrieved with SCUBA. Lake Anna was well colonized by benthic macroinvertebrates during the summer season immediately after impoundment. The total density of organisms increased in each of the first three years. Major changes in the fauna occurred between the first and second years, but the changes between the second and third years were more subtle. The fauna could be divided into two distinct groups based upon the time when the organisms were most consistently abundant. The first colonizers appeared to be dependent upon the components of the former terrestrial ecosystem for food and habitat. As autochthonous factors began to regulate succession, diversity increased and the dominant species shifted to an assemblage of second colonizers. These factors included: (1) decomposition of terrestrial vegetation and detritus leaving bare substrate, (2) sedimentation, (3) improved food quality of the organic matter in the sediment because of ingestion and egestion by the organisms themselves, (4) increased plankton populations, and (5) appearance of macrophytes. As the second colonizers became firmly established in the third year, distinct patterns of spatial distribution began to appear among species with similar niches.     

Average seasonal phytomass: a temporally independent index of herbaceous plant dominance

Diversity, similarity and dominance in plant communities are usually assessed from data collected at a single date. Herbaceous species have differing periods of growth, making phytomass or cover-weighted indices of diversity, similarity or dominance highly dependent on the timing of data collection. A new way of mathematically expressing residence time is presented. Average seasonal phytomass values can be used to better express dominance throughout a growing season. A similar approach could be used for cover or any other dynamic property of plant growth. These values could then be used in dominance-weighted indices of community similarity and diversity. Acknowledgements: J. Watkins-Williams assisted in the field and laboratory. R. L. Bayn, Jr. assisted in data processing. This study was supported in part by Grant DEB-78-05328 from the National Science Foundation to J. A. MacMahon.     

Catalytic versatility of trehalase: synthesis of alpha-D-glucopyranosyl alpha-D-xylopyranoside from beta-D-glucosyl fluoride and alpha-D-xylose

Trehalase was previously shown (see ref. 5) to hydrolyze alpha-D-glucosyl fluoride, forming beta-D-glucose, and to synthesize alpha, alpha-trehalose from beta-D-glucosyl fluoride plus alpha-D-glucose. Present observations further define the enzyme's separate cosubstrate requirements in utilizing these nonglycosidic substrates. alpha-D-Glucopyranose and alpha-D-xylopyranose were found to be uniquely effective in enabling Trichoderma reesei trehalase to catalyze reactions with beta-D-glucosyl fluoride. As little as 0.2mM added alpha-D-glucose (0.4mM alpha-D-xylose) substantially increased the rate of enzymically catalyzed release of fluoride from 25mM beta-D-glucosyl fluoride at 0 degrees. Digests of beta-D-glucosyl fluoride plus alpha-D-xylose yielded the alpha, alpha-trehalose analog, alpha-D-glucopyranosyl alpha-D-xylopyranoside, as a transient (i.e., subsequently hydrolyzed) transfer-product. The need for an aldopyranose acceptor having an axial 1-OH group when beta-D-glucosyl fluoride is the donor, and for water when alpha-D-glucosyl fluoride is the substrate, indicates that the catalytic groups of trehalose have the flexibility to catalyze different stereochemical reactions.