Paleoecological reconstruction of changes in the productivity of a small,meromictic lake in Southern Ontario,Canada

Some aspects of the paleoproductivity of meromictic Crawford Lake, near Toronto, are inferred from a study of its sedimentary pigments, and diatoms. Several stages of lake development are observed over the 35 cm-deep sediment core removed from the center of Crawford Lake. Evidence of changes in lake productivity during the last 300 years was reflected by significant stratigraphic sediment pigment changes which were associated with European settlement in the Crawford Lake watershed and recent alterations associated with the area's operation by the Conservation Authority (1969 — present). One of the most important factors correlated with paleoproductivity was land clearance (mainly logging of white oak and pine). Deforestation during the last century is correlated with an increase in the amount of algal pigments deposited in the lake's sediments during the 1800's. During the last 10 years a striking increase in the accumulation of chlorophyll derivatives was observed. This is correlated with a dramatic increase in the number of visitors to the lake.Stratigraphic changes in the ratio of cyanobacterial to phototrophic bacterial pigment accumulation are used to infer changes which occurred during the shift from mesotrophy to eutrophy in Crawford Lake.     

Collagenous substrata regulate the nature and distribution of glycosaminoglycans produced by differentiated cultures of mouse mammary epithelial cells

We have investigated the influence of culture substrata upon glycosaminoglycans produced in primary cultures of mouse mammary epithelial cells isolated from the glands of late pregnant mice. Three substrata have been used for experiments: tissue culture plastic, collagen (type I) gels attached to culture dishes, and collagen (type I) gels that have been floated in the culture medium after cell attachment. These latter gels contract significantly. Cells cultured on all three substrata produce hyaluronic acid, heparan sulfate, chondroitin sulfates and dermatan sulfate but the relative quantities accumulated and their distribution among cellular and extracellular compartments differ according to the nature of the culture substratum. Notably most of the glycosaminoglycans accumulated by cells on plastic are secreted into the culture medium, while cells on floating gels incorporate almost all their glycosaminoglycans into an extracellular matrix fraction. Cells on attached collagen gels secrete approx. 30% of their glycosaminoglycans and assemble most of the remainder into an extracellular matrix. Hyaluronic acid is produced in significant quantities by cells on plastic and attached gels but in relatively reduced quantity by cells on floating gels. In contrast, iduronyl-rich dermatan sulfate is accumulated by cells on floating gels, where it is primarily associated with the extracellular matrix fraction, but is proportionally reduced in cells on plastic and attached gels. The results are discussed in terms of polarized assembly of a morphologically distinct basal lamina, a process that occurs primarily when cells are on floating gels. In addition, as these cultures secrete certain milk proteins only when cultured on floating gels, we discuss the possibility that cell synthesized glycosaminoglycans and proteoglycans may play a role in the maintenance of a differentiated phenotype.     

Temporal changes in the level of infestation of Simulium ornatum Meigen (complex) (Simuliidae: Diptera) larvae by the endosymbiotic fungus Harpella melusinae Lichtwardt (Harpellales: Trichomycetes)

The fungus Harpella melusinae (Harpellales: Trichomycetes) is obligately associated with the midguts of larval Simuliidae (Diptera). The level of infestation of a population of Simulium ornatum by H. melusinae was monitored at a stream in Hampshire, England. Significant temporal changes in the level of infestation were recorded during monthly and weekly collections; a twenty-fold increase being recorded over a nine-day period. Possible mechanisms by which these changes occur are discussed.     

Behavioral and hormonal aspects of reproduction in captive goeldi’s monkeys (Callimico goeldii) in a comparative and evolutionary context

The fate of most nonhuman primate species is intimately related to man. The increasing encroachment on the natural habitat has resulted in the decimation and even near extinction of some species. Along with this development, the basic concept in many modern zoos has changed from one of merely display to self-perpetuating units. Primate research facilities are orienting their research programs towards reproductive physiology and behavior in an effort to provide basic knowledge of reproduction in these species. This increased emphasis in the area of reproductive biology and the various efforts to improve breeding of these mostly endangered primates in captivity has stimulated the author to write this review. It represents an attempt to provide the reader with basic background information relating to the endocrinology and behavior of reproduction in the clawed New World monkeys as it exists at the time of publication. The intermediate evolutionary position ofCallimico goeldii between the clawed New World monkeys and the ‘true New World monkeys’ and our relatively poor knowledge about reproduction and behavior in this particular species fully justifies the focus on Goeldi’s monkey in this essay. This review is an attempt to provide a brief history of previous studies but also the basis for research in the future. The current status of knowledge of the small-bodied clawed monkeys is also discussed in an evolutionary context, with an emphasis on the different reproductive strategies in this dynamic group of primates. The outcome, not surprisingly, confirms the unique position ofCallimico goeldii in its social, ecological, and evolutionary environment.     

Getting to the root of the problem: new evidence for the use of plant root foods in Mesolithic hunter-gatherer subsistence in Europe

Vegetation History and Archaeobotany - This paper presents new evidence for the harvesting of edible plant roots and tubers at Northton, a Mesolithic hunter-gatherer site on Harris, in the Western...     

Effect of Planting Unit Size and Sediment Stabilization on Seagrass Transplants in Western Australia

Abstract The effect of increasing planting unit size and stabilizing sediment was examined for two seagrass planting methods at Carnac Island, Western Australia in 1993. The staple method (sprigs) was used to transplant Amphibolis griffithii (J. M. Black) den Hartog and the plug method was used to transplant A. griffithii and Posidonia sinuosa Cambridge and Kuo. Transplant size was varied by increasing the number of rhizomes incorporated into a staple and increasing the diameter of plugs. Planting units were transplanted into bare sand, back into the original donor seagrass bed, or into a meadow of Heterozostera tasmanica, which is an important colonizing species. Sprigs of A. griffithii were extracted from a monospecific meadow; tied into bundles of 1, 2, 5, and 10 rhizomes; and planted into unvegetated areas. Half the units were surrounded by plastic mesh and the remainder were unmeshed. All treatments were lost within 99 days after transplanting, and although larger bundles survived better than smaller ones, no significant differences could be attributed to the effects of mesh or sprig size. Plugs of P. sinuosa and A. griffithii were extracted from monospecific meadows using polyvinyl chloride pipe of three diameters, 5, 10, and 15 cm, and planted into unvegetated areas nearby. Half the units were surrounded by plastic mesh and the remainder were unmeshed. Posidonia sinuosa plugs were also placed within a meadow of H. tasmanica (Martens ex Aschers.) den Hartog. Only 60% of A. griffithii plug sizes survived 350 days after transplanting back into the donor bed; however, survival of transplants at unvegetated areas varied considerably, and analysis of variance indicated a significant two‐way interaction between treatment and plug size. Transplants survived better when meshed (90% survived) and survival improved with increasing plug size. Posidonia sinuosa transplants survived poorly (no plugs survived beyond 220 days in bare or meshed treatments) regardless of size. Survival of 10‐ and 15‐cm plugs was markedly better than the 5‐cm plugs in vegetated areas, including the H. tasmanica meadow. The use of large seagrass plugs may be appropriate for transplantation in high‐energy wave environments.