Life Sciences Commons^™

Heterochronic Genes Control The Stage-Specific Initiation And Expression Of The Dauer Larva Developmental Program In Caenorhabditis Elegans, Zhongchi Liu, Victor R. Ambros

Victor R. Ambros

We report that a stage-specific developmental program, dauer larva formation, is temporally regulated by four heterochronic genes, lin-4, lin-14, lin-28, and lin-29. The effects of mutations in these four genes on dauer larva formation have revealed that they regulate two different processes of dauer larva formation: (1) a decision specifying the larval stage at which dauer larva development initiates, and (2) the specialized differentiation of hypodermal cells during dauer larva morphogenesis. Epistasis analysis has suggested a model in which lin-4 negatively regulates lin-14, and the resulting temporal decrease in lin-14 activity specifies the stage of dauer larva initiation. Our results …

Amino Acid Uptake And Metabolism By Larvae Of The Marine Worm Urechis Caupo (Echiura), A New Species In Axenic Culture, William Jaeckle, Donal T. Manahan

William Jaeckle

Axenic (bacteria-free) larval cultures of the marine echiuran worm, Urechis caupo, were reliably obtained by aseptically removing gametes directly from the gamete storage organs. Trochophore larvae only removed neutral amino acids from seawater as measured by high-performance liquid chromatography (HPLC). There was no detectable uptake, as measured by HPLC, of acidic or basic amino acids. Kinetic analysis showed that the transport system for alanine in 4-day-old larvae had a Kt of 4-6 μM and a Jmax of 9-10 pmol larva-1 h-1. Following a 50-min exposure, the majority of the radio-activity (95%) from 14C-alanine was found in the trichlo-roacetic acid-soluble fraction. …

Effects Of Intensive Fishing Effort On The Population Structure Of Quahogs, Mercenaria Mercenaria (Linnaeus, 1758), In Narragansett Bay, Michael Rice, Charles Hickox, Itrat Zehra

Michael A Rice

Plant-Animal Interactions: An Overview, W. Abrahamson

Warren G. Abrahamson, II

Fads In Ecology: Is There A Bandwagon And Do We Know When To Get Off?, W. Abrahamson, T. Whitham, P. Price

Warren G. Abrahamson, II

Feeding By A “Nonfeeding” Larva: Uptake Of Dissolved Amino Acids From Seawater By Licithotrophic Larvae Of The Gastropod Haliotis Refescens, William Jaeckle

William Jaeckle

No abstract provided.

Growth And Energy Imbalance During The Development Of A Lecithotrophic Molluscan Larva (Haliotis Rufescens), William Jaeckle, Donal T. Manahan

William Jaeckle

Larvae of the gastropod Haliotis rufescens are classified as "nonfeeding" because they cannot capture particular foods. However, for only 1 out of 5 independent cultures was a net decrease observed in dry organic weight during the complete period of larval development (5 to 7 days). In fact, there were net increases in dry organic weight from the oocyte (day 0) to the newly formed veliger larvae (2-day-old). These weight increases during early development could be explained by increases in the amounts of specific biochemical components of the larvae, relative to oocytes. The metabolic rates of larvae were measured (oxygen consumption) …

Life History Of A Ponderosa Pine Coneworm, Dioryctria Auranticella (Lepidoptera: Pyralidae), Judith E. Pasek, Mary Ellen Dix

Judith E Pasek

Dioryctria auranticella (Grote), a coneworm that infests ponderosa pine, Pinus ponderosa Douglas ex. P. Lawson and Lawson, and Austrian pine, P. nigra Arnold, in southeastern Nebraska is univoltine. Head capsule measurements indicate five instars. First instars apparently overwinter in hibernaculae. Second and third instars feed in male and female pine flowers during early May. Fourth and fifth instars tunnel in second-year cones for about 2-3 wk between mid-May and mid-June and often require two cones to complete development. Larvae pupate within cones during June, and adults are active from mid-June to late July. at 26C, eggs hatch in 6-9 d. …

Genetics Of Screwworm, New Genetic Markers And Preliminary Linkage Map., David B. Taylor

David B. Taylor

Eight new genetic markers for Cochliomyia hominivorax (Diptera: Calliphoridae), the screwworm, are characterized. The markers include three eye mutants, lemon-eye (Ie), cherry-eye (ch), and red-eye (re); one wing mutant, curly-wing (cw); and four allozyme markers, amylase (Amy-1), glycerol-3-phosphate dehydrogenase (Gpd), phosphoglucomutase (Pgm), and octanol dehydrogenase (Odh). The markers are associated into four linkage groups. Radiation-induced translocations were used to correlate the linkage groups with their respective chromosomes. A preliminary genetic linkage map with these and three previously characterized loci is presented.

Texture, Climate And Cultivation Effects On Soil Organic Matter Content In U.S. Grassland Soils, Ingrid C. Burke

Ingrid Burke

Soil organic C content, a major source of system stability in agroecosystems, is controlled by many factors that have complex interactions.The purpose of this study was to evaluate the major controls over soil organic carbon content, and to predict regional patterns of carbon in range and cultivated soils. We obtained pedon and climate data for 500 rangeland and 300 cultivated soils in the U.S. Central Plains Grasslands, and statistically analyzed relationships between C and soil texture and climate. Regression models of the regional soils database indicated that organic C increased with precipitation and clay content, and decreased with temperature. Analysis …