The human right clavicle tends to be shorter than the left. A range of possible explanations can be advanced to account for this asymmetry. In the present work, clavicular morphology was studied in a medieval skeletal assemblage from Wharram Percy, England, with the aim of evaluating these competing explanations. At Wharram Percy, as anticipated, the right clavicle tended to be shorter. Patterns of asymmetry in curvature, robusticity, vascularization, and in the morphology of ligament and muscle attachment sites were also studied. The patterning in these data at Wharram Percy is consistent with inhibition of longitudinal growth of the clavicle on the dominant side due to lateral bias in mechanical loading, particularly in axial compression. Copyright © 1999 John Wiley & Sons, Ltd.

Zebra mussels, Dreissena polymorpha, were collected monthly from April/May to November in 1990 and 1991 from two sites in Lake St. Clair. The sites were characterized by relatively high and low mussel densities. The following variables were measured: ash-free dry weight (AFDW) per unit shell length (SL), lipid content and classes, carbon content, and nitrogen content. Mussels from the high-density site had a lower AFDW. SL relationship, lower lipid content, and a lower C:N ratio than mussels from the low-density site. Seasonal trends in these variables were consistent between sites and years. AFDW:SL, lipid, and carbon content were highest in the spring and then declined to minimum levels in late summer/fall. The mean seasonal decline in weight from spring to late summer for a standard 15-mm mussel was 60%. This decline was greater than might be expected from gamete release alone and was likely a result of nutritional stress from warm summer temperatures and limited food supplies. Between 1990 and 1991, the mean AFDW of a 15-mm mussel declined 34% and 50% at the high- and low-density site, respectively. However, when C:N ratios and lipid levels in 1990 and 1991 were compared, C:N ratios were only lower in fall 1991 compared to fall 1990, and lipid levels for the 2 years were generally similar.

A direct microscopic method for distinguishing dead from viable bacterial cells in milk is reported. The method is based on the principles of vital staining. One cc. of the milk to be examined is mixed with 0.5 cc. of a dye mixture containing 0.1 per cent methylene blue and 0.1 per cent Nile blue sulfate, and with 0.5 cc. of a gelatin-agar mixture containing 8 per cent gelatin and 2 per cent agar. 0.01 cc. of this mixture is placed on a clean glass slide and covered with a small cover glass (1.28×1.28cm.). The stained cells are then counted and they represent the dead cells already present in the milk. To a similar mixture one drop of 0.7 to 0.8 normal NaOH is added. This causes staining of all the cells present in the milk. The difference between the two counts represents the number of viable cells present.

While the cause of the widespread dieback has not yet been identified, it is believed that a number of interacting factors may be involved. These factors include environmental conditions associated with a 2-year drought in south Louisiana. Environmental conditions linked to drought include increased air, soil, and water temperatures, reduced freshwater input from rainfall and river flows, increased salinity, and changes in the concentration of potential phytotoxins such as hydrogen sulfide and various metals. The physicochemical factors influenced by the drought may act to exacerbate effects of potential biotic stressors, including pathogens (e.g., fungi, viruses), and herbivory. This proposal describes a one-year field study to identify the potential physicochemical causal factors for the dieback, and to characterize impacts to existing plant communities due to the phenomenon.