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Shoals of fish are often composed of individuals similar in body size or other characteristics. This study tested for the assortment by sex (controlled for body size) in a species with a low degree of sexual dimorphism. Zebrafish (Danio rerio) shoaling was studied in the laboratory using four different experiments utilizing two different methodologies. In most of the experiments, females showed a statistically significant preference for shoaling with other females, but males typically showed no preference. In choice experiments zebrafish preferred swimming near a compartment containing another zebrafish compared to swimming near an empty compartment, but this preference was strongest for same-sex pairings, both female-female and male-male. In additional choice experiments, the results showed a preference among females (but not males) for a group of three same-sex fish over three opposite-sex fish. There was no consistent result when females were forced to choose between three females and six males, thus the preference for same-sex shoalmates may be balanced with a preference for larger shoals. The second methodology used freely-swimming groups of four fish. Females swam closer to females than to males, but males showed no preference. Few previous studies have demonstrated sex-assortative shoaling.
Physarum polycephalum, a slime mold typically found in decaying plant vegetation, is a member of the class/superclass Myxogastridae. P. polycephalum moves through cytoplasmic streaming due to the interaction between actin and myosin within the walls of its plasmodial tubes. Although early studies indicated that calcium has an excitatory effect on growth, more recent studies showed that the effect of calcium on growth is inhibitory. To determine the direction of the effect of calcium on the growth of P. polycephalum, the organism was grown on agar strips containing various concentrations of CaCl2 for a 72-hour period. Growth was monitored every 24 hours. During the first 48 hours of growth, calcium significantly increased the growth of P. polycephalum. However, in the next 24-hour interval, calcium significantly decreased the growth of the organism. In addition, as the CaCl2 concentration increased, both the enhancement and inhibition of growth became greater. This suggests that the initial effect of calcium is enhancement and the later effect is inhibition.
The fruit from milk thistle (Silybum marianum) contains flavonolignans that posses therapeutic properties. Milk thistle extract is sold and taken as an herbal supplement. However, it is not regulated by the Food and Drug Administration. The amount of flavonolignans in the commercial products is unknown. High-performance liquid chromatography (HPLC) was used to analyze the flavonolignans from six different commercial milk thistle products. The six commercial supplements consistently show lower amounts of total flavonolignans compared to the amount of milk thistle extract stated on the bottle. A consumer would receive the highest amount of total flavonolignans in a capsule by taking the Vitamin Shoppe product. On a cost basis, Origin provides the highest amount of total flavonolignans per capsule at the lowest price.
There are seven documented types of spider silk, all composed of proteins. Each type is synthesized in a specific gland on a spider's abdomen in a liquid crystalline form and spun through a unique spinneret where it experiences oligomerization and becomes a solid. In this study, the structures of spider silk were examined using a Scanning Electron Microscope. Spider silk was collected from a variety of species from both indoor and outdoor environments in Massachusetts and Vermont, including the genera: Achaearanea, Araneus, Argiope, Cryphoeca, Mimetus, and Pholcus as well as the family Salticidae. The silk was sputter coated with gold and visualized at magnifications up to 35,000×. Several types of silk structures were observed to be common regardless of the species. These structures included large rounded bilateral fibers averaging 1.29µm in diameter and fibers laden with equidistant silk droplets ranging from 0.22µm to 43.75µm depending on the species. Based on their consistency in appearance, these structures may be associated with particular functions. The bilateral fibers may be dragline or major ampullate silk, which has been described as the strongest silk, providing the web's structural support. The strands covered in droplets may be viscid or glue-like silk that is involved in catching prey. Several other structures were observed as well, and included rectangular bifurcated, ridged, corkscrew, wound bifurcated, semi-braided, single and multiple stranded fibers. Further research may provide insight in to spider silk structures and how each type is used by the spider.
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