Microhabitat use by fish in the upper Rio Matarraña, Spain, 1984–1987

Abstract– We evaluated the microhabitat use and abundance of Barbus graellsii, Bardus haasi, Chondrostoma toxostoma, Noemacheilus barbatulus, Oncorhynchus mykiss and Rutilus arcasii between 1984 and 1987 in the upper Rio Matarraña, Spain. The mean abundance classes for all species ranged from 1.8 to 3.0 (where 1=1–6, 2=6–10, 3=11–20 and 4=>20 specimens, respectively). Mean abundance was consistently higher in 1984–1985 (2.4–3.0) than during 1986–1987 (1.8–2.8). The decreases noted in 1986–1987 were attributable to declines in abundance of O. mykiss (introduced in winter 1984) and B. haasi. Barbus graellsii and Ch. toxostoma, however, remained abundant throughout the entire 4-year study. We only observed N. barbatulus and R. arcasii irregularly in the study site. Analyses of microhabitat availability data indicated that the study site contained more silt and less algae/debris during spring 1985 and early and late summer 1986 than in the majority of the remaining season. The converse was true for late summer 1985 (i. e., less silt and more algae/debris than the majority of seasons). Principal component analyses showed that B. graellsii and Ch. toxostoma generally occupied deeper microhabitats with low to average velocities, higher amounts of depositional substrata and lower quantities of erosional substrata. B. haasi tended to avoid microhabitats with rubble substrata and occurred in those with higher amounts of algae/debris. O. mykiss occupied shallower areas with slightly higher velocities and a heterogeneous substratum. With the exception of B. haasi, microhabitat use by assemblage members was similar from 1984 to 1987. B. haasi, however, was not as strongly affected by depth in the latter two years of the study as it was during 1984–1985. Seasonal and annual analyses of intraspecific microhabitat use showed that most changes were due to variations in microhabitat availability. Nonetheless, all species exhibited minor seasonal shifts in microhabitat use. Size-related analyses indicated that both smaller B. graellsii and Ch. toxostoma occupied shallower microhabitats with slower velocities than larger specimens. Intersite differences in microhabitat use for B. graellsii and Ch. toxostoma showed that most differences in substratum use were attributable to disparities in substratum availability. Both species occurred closer to the substratum in the site with higher velocities (i. e., upper reach), although this response was more pronounced in Ch. toxostoma. Interspecific analyses indicated that B. graellsii and Ch. toxostoma did not consistently occupy statistically differentiable microhabitats, although both species occurred farther from the substratum and refuges than did B. haasi. O. mykiss occupied shallower microhabitats with more gravel than either B. graellsii or Ch. toxostoma. The lack of microhabitat shifts by native species during the study period indicates that interactions with either B. haasi or O. mykiss did not play a strong role in microhabitat use by the remaining assemblage members.     

Alternatives to Blood as a Source of DNA for Large-scale Scanning Studies of Canine Genome Linkages

Participation and compliance are critical to the success of any large-scale study of canine disease using DNA markers. Most canine genetic studies rely upon DNA extracted from peripheral blood samples. We assessed the utility of buccal swab epithelial cells and toe nails as a source of DNA for use in genomic screening studies. Using eight multiplexed canine microsatellite markers, amplified DNA obtained from peripheral blood, and from freshly extracted buccal epithelial cells, and buccal swab DNA extracted and stored at –20°C for 27 months or extracted from toe nails were compared for three dogs. The accuracy of the genotyping at each locus was identical for each preparation. Buccal swab DNA samples were readily and uniformly amplified and could be stored for years without loss of integrity. Each buccal swab provided sufficient DNA for more than 200 individual PCR reactions. Toe nails provided ample DNA for thousands of PCR reactions and had the added advantage of ease of storage of the original tissues. These studies demonstrate the potential utility of DNA derived from buccal swabs or nails in large-scale genomic scanning and marker linkage studies.     

Reproductive timing in three southern Appalachian stream fishes

We quantified the reproductive biology of mottled sculpin (Cottus bairdi), rosyside dace (Clinostomus funduloides) and longnose dace (Rhinichthus cataractae) in Coweeta Creek, North Carolina, USA, a fifth order stream. These species are abundant in coldwater streams through out the southern Appalachian mountains, the southernmost limit of their range. We collected fishes from Coweeta Creek every second month (between July 1984 and January 1986) and quantified the seasonal reproductive cycles of females, using both histological techniques and the relative gonadal index (RGI). Both techniques indicated that I) C. bairdi reproduced between March and May, 2) CI. funduloides spawned between May and August and 3) R. cataractae were reproductively active between June and July. These conclusions were supported by the following: 1) the presence of reproductive coloration, 2) gravid females, 3) courtship displays, 4) the presence of nest-guarding C. bairdi males and 5) the timing of young-of-the-year recruitment. The reproductive characteristics of these 3 species were correlated with different environmental variables. The mean monthly RGI values for both C. bairdi and R. cataractae were inversely correlated with both maximum and minimum daily water temperatures. The mean RGI values for C. bairdi also were negatively correlated with photoperiod, whereas the values for R. cataractae and CI. funduloides were positively correlated with the change in daily photo period.     

Intracranial drug implants: an autoradiographic analysis of diffusion

Labeled crystalline atropine, administered to the hypothlalamus of rats, remainted strictly localized in a sphere, 1.0 to 1.8 millimeters in diameter, ditring the first 3 minutes. A similar distribution obtained after 1 hour. At intermediate times, slightly elevated radioactivity, reflecting concentrations 2,000 to 10,000 times below behaviorally effective doses, was observed several millimeters from the implantation site.     

Compression fracture of wood parallel to the grain

Summary A theoretical model of wood is presented consisting of a bonded assembly of long hollow tubes. As increasing load is applied to the tubes in the direction of their length, it is assumed that the bonding material breaks until sufficient free lengths exist for portions of the tubes to buckle. The dependence of the buckling stress and the free length on dimensions and properties of the tubes is calculated and the angle of the band of unstable portions is derived. The behaviour of the model is compared with the measured behaviour of wood. Agreement is encouraging and refinements are suggested to reduce the discrepancies observed.     

Histochemical localization of renal trehalase: demonstration of a tubular site

Trehalase activity has been localized histochemically within the cortical tubules of the human, rabbit, and mouse kidneys. The specific localization of the enzyme supports the hypothesis that trehalase, in concert with a series of other enzymes which synthesize trehalose from glucose, functions in a mechanism for the reabsorption of glucose from the glomerular filtrate.     

The unusual varl gene of yeast mitochondrial DNA

The var1 gene specifies the only mitochondrial ribosomal protein known to be encoded by yeast mitochondrial DNA. The gene is unusual in that its base composition is nearly 90 percent adenine plus thymine. It and its expression product show a strain-dependent variation in size of up to 7 percent; this variation does not detectably interfere with function. Furthermore, var1 is an expandable gene that participates in a novel recombinational event resembling gene conversion whereby shorter alleles are preferentially converted to longer ones. The remarkable features of var1 indicate that it may have evolved by a mechanism analogous to exon shuffling, although no introns are actually present.     

VEGA Balloon Dynamics and Vertical Winds in the Venus Middle Cloud Region

The VEGA balloons provided a long-term record of vertical wind fluctuations in a planetary atmosphere other than Earth's. The vertical winds were calculated from the observed displacement of the balloon relative to its equilibrium float altitude. The winds were intermittent; a large burst lasted several hours, and the peak velocity was 3 meters per second.     

Three-year incidence of AIDS in five cohorts of HTLV-III-infected risk group members

The incidence of the acquired immune deficiency syndrome (AIDS) among persons infected with human T-lymphotropic virus type III (HTLV-III) was evaluated prospectively among 725 persons who were at high risk of AIDS and had enrolled before October 1982 in cohort studies of homosexual men, parenteral drug users, and hemophiliacs. A total of 276 (38.1 percent) of the subjects were either HTLV-III seropositive at enrollment or developed HTLV-III antibodies subsequently. AIDS had developed in 28 (10.1 percent) of the seropositive subjects before August 1985. By actuarial survival calculations, the 3-year incidence of AIDS among all HTLV-III seropositive subjects was 34.2 percent in the cohort of homosexual men in Manhattan, New York, and 14.9 percent (range 8.0 to 17.2 percent) in the four other cohorts. Out of 117 subjects followed for a mean of 31 months after documented seroconversion, five (all hemophiliacs) developed AIDS 28 to 62 months after the estimated date of seroconversion, supporting the hypothesis that there is a long latency between acquisition of viral infection and the development of clinical AIDS. This long latency could account for the significantly higher AIDS incidence in the New York cohort compared with other cohorts if the virus entered the New York homosexual population before it entered the populations from which the other cohorts were drawn. However, risk of AIDS development in different populations may also depend on the presence of as yet unidentified cofactors.     

GONG Observations of Solar Surface Flows

Doppler velocity observations obtained by the Global Oscillation Network Group (GONG) instruments directly measure the nearly steady flows in the solar photosphere. The sun's differential rotation is accurately determined from single observations. The rotation profile with respect to latitude agrees well with previous measures, but it also shows a slight north-south asymmetry. Rotation profiles averaged over 27-day rotations of the sun reveal the torsional oscillation signal-weak, jetlike features, with amplitudes of 5 meters per second, that are associated with the sunspot latitude activity belts. A meridional circulation with a poleward flow of about 20 meters per second is also evident. Several characteristics of the surface flows suggest the presence of large convection cells.