Character Displacement and Acoustic Insects

Crickets, katydids, grasshoppers, and cicadas should be idealfor illustrating character displacement. Their species-specificcalling songs are of direct importance to reproductive success,and species with similar songs and overlapping ranges shoulddevelop greater differences in their songs in areas of sympatry.Although many pairs of species have suitably similar songs andoverlapping ranges and the data concerning songs are extensivefor crickets and katydids, no convincing example of characterdisplacement has been found in acoustic insects. Lack of suchexamples can be attributed to false premises, to divergencecompleted in allopatry. to elimination of geographical variationin song by gene flow between the zone of sympatry and the zonesof allopatry, and to the scanty sample that has been intensivelystudied.     

Effects of double ligation of Stensen's duct on the rabbit parotid gland

Salivary gland duct ligation is an alternative to gland excision for treating sialorrhea or reducing salivary gland size prior to tumor excision. Duct ligation also is used as an approach to study salivary gland aging, regeneration, radiotherapy, sialolithiasis and sialadenitis. Reports conflict about the contribution of each salivary cell population to gland size reduction after ductal ligation. Certain cell populations, especially acini, reportedly undergo atrophy, apoptosis and proliferation during reduction of gland size. Acini also have been reported to de-differentiate into ducts. These contradictory results have been attributed to different animal or salivary gland models, or to methods of ligation. We report here a bilateral double ligature technique for rabbit parotid glands with histologic observations at 1, 7, 14, 30, 60 days after ligation. A large battery of special stains and immunohistochemical procedures was employed to define the cell populations. Four stages with overlapping features were observed that led to progressive shutdown of gland activities: 1) marked atrophy of the acinar cells occurred by 14 days, 2) response to and removal of the secretory material trapped in the acinar and ductal lumens mainly between 30 and 60 days, 3) reduction in the number of parenchymal (mostly acinar) cells by apoptosis that occurred mainly between 14–30 days, and 4) maintenance of steady-state at 60 days with a low rate of fluid, protein, and glycoprotein secretion, which greatly decreased the number of leukocytes engaged in the removal of the luminal contents. The main post- ligation characteristics were dilation of ductal and acinar lumens, massive transient infiltration of mostly heterophils (rabbit polymorphonuclear leukocytes), acinar atrophy, and apoptosis of both acinar and ductal cells. Proliferation was uncommon except in the larger ducts. By 30 days, the distribution of myoepithelial cells had spread from exclusively investing the intercalated ducts pre-ligation to surrounding a majority of the residual duct-like structures, many of which clearly were atrophic acini. Thus, both atrophy and apoptosis made major contributions to the post-ligation reduction in gland size. Structures also occurred with both ductal and acinar markers that suggested acini differentiating into ducts. Overall, the reaction to duct ligation proceeded at a considerably slower pace in the rabbit parotid glands than has been reported for the salivary glands of the rat.     

A MUCILAGE-FORMING LACTOBACILLUS SPECIES ISOLATED FROM CIDER. PART II. POLYSACCHARIDE FORMATION

SUMMARY: Cultures grown at 25° under an atmosphere of CO₂ in a medium containing maltose, inorganic salts and ethanolic extracts of peptone and yeast autolysate produced a polysaccharide, which was isolated and purified. Examination by a variety of chemical and biological methods indicated that it was a dextran of low molecular weight.     

NUTRITIONAL REQUIREMENTS OF ACETOBACTER SPECIES: INORGANIC AMMONIUM SALTS AS SOURCES OF NITROGEN

SUMMARY: Forty-six strains of Acetobacter , representing twenty species, have been compared on the basis of their respective abilities to proliferate in two defined inorganic media, in which either glucose or ethanol was the sole source of carbon and energy. Twenty-three strains, representing eleven species, grew in either inorganic medium when glucose was present and nine of these strains, representing five species, could grow also in either inorganic medium when ethanol was present. The remaining twenty-three strains, representing eleven species, failed to grow in either medium with either glucose or ethanol. Three organisms grew better with ethanol than with glucose and three were inhibited by ethanol in the presence of glucose.     

The Laminariaceae off North Shapinsay: Changes from 1947 to 1953

Four sublittoral surveys, off the north coast of the islandof Shapinsay, Orkney, have been completed in May 1947, July1951, July 1952, and July 1953. The calculated quantity of seaweed from 1 to 6 fathoms was 34,000tons during the initial survey of May 1947 after a comparativelymild winter and before the period when bad weather brings aboutthe loss of large quantities of the previous year's growth oflaminaria fronds. The three resurveys were completed after this. The quantity of seaweed in July 1951 was 10,000 tons, and inJuly 1952 a further reduction was found, bringing down the quantityto 6,000 tons. In July 1953 the quantity had partially recovered,reaching 7,000 tons. The increase was reflected more in theseaweed cover than in density. Between 1952 and 1953 the weightof individual plants had decreased but the number of plantsper unit area was greater, which, combined with an increasein the area of seabed covered, made an overall gain in quantity.Laminaria saccharina maintained its dominance in this area throughoutthe period 1947–53.