Fish size and habitat depth relationships in headwater streams

Summary Surveys of 262 pools in 3 small streams in eastern Tennessee demonstrated a strong positive relationship between pool depth and the size of the largest fish within a pool (P<0.001). Similarly, the largest colonizers of newly-created deep pools were larger than the colonizers of shallow pools. We explored the role of predation risk in contributing to the bigger fish — deeper habitat pattern, which has been noted by others, by conducting five manipulative field experiments in two streams. Three experiments used stoneroller minnows (Campostoma anomalum); one used creek chubs (Semotilus atromaculatus); and one used striped shiners (Notropis chrysocephalus). The stoneroller experiments showed that survival of fish approximately 100 mm in total length (TL) was much lower in shallow pools (10 cm deep) than in deep (40 cm maximum) pools (19% versus 80% survival over 12 d in one experiment) and added cover markedly increased stoneroller survival in shallow pools (from 49% to 96% in an 11-d experiment). The creek chub experiment showed that, as for stonerollers, pool depth markedly influenced survival: the chubs survived an average of 4.9 d in shallow pools and >10.8 d in deep pools. In the striped shiner experiment in shallow artificial streamside troughs, no individuals 75–100 mm TL survived as long as 13 d, where-as smaller (20–25 mm) fish had 100% survival over 13 d. The results of the experiments show that predation risk from wading/diving animals (e.g., herons and raccoons) is much higher for larger fishes in shallow water than for these fishes in deeper water or for smaller fish in shallow water. We discuss the role of predation risk from two sources (piscivorous fish, which are more effective in deeper habitats, and diving/wading predators, which are more effective in shallow habitats) in contributing to the bigger fish — deeper habitat pattern in streams.     

Metabolism of a subtropical Brazilian lagoon

Total community, planktonic and benthic metabolisms were measured by using the carbon dioxide production and consumption, the diurnal curve' method and the in situ bottle incubation technique over an annual cycle in two sublagoons of the Saquarema Lagoon, Brazil. Metabolic rates of the phytoplankton-based lagoon were characterized by considerable daytime and daily variability in production and respiration, by a seasonal shift between net autotrophy and heterotrophy and by an annual balance of production (P = 105 ± 65 mmoles/m²/dayn = 25) and respiration (R = 102 ± 50 mmoles/m²/dayn = 25). Total community metabolism was similar throughout the lagoon, but phytoplankton assimilation rates and benthic respiration showed spatial differences. Bottle incubations compared to total community free water respiration suggested that the pelagic community was 2–5 times more active than the benthos     

Modified structure and kinetics of cytochrome-c oxidase in fibroblasts from patients with Leigh syndrome

In this study we compared the properties of cytochrome-c oxidase (COX) in cultured fibroblasts from two patients with Leigh Syndrome with COX from control fibroblasts. The fibroblasts from patients showed decreased growth reates and elevated lactate production. COX activity of patients fibroblasts was about 25% of control. Kinetic studies with isolated mitochondria showed a higher K_m for cytochrome c and a markedly reduced molecular turnover of COX from patients, indicating a different structure of the enzyme. A biphasic change of COX activity was obtained by titration of dodecylmaltoside solubilized mitochondria from control fibroblasts with increasing concentrations of anions. With patient mitochondria we found only the inhibiting phase of COX activity and, in contrast to control mitochondria, irreversible inhibition of COX activity by guanidinium chloride. ELISA titrations with monoclonal antibodies to subunit II, IV, Vab, VIac and VIIab indicated a normal amount of mitochondrial coded subunit II, but a reduced amound of nuclear coded subunits. The data indicate incompletely assembled nuclear coded subunits of COX from patient fibroblasts.     

Theory of chaperonin action: inertial model for enhancement of prokaryotic Rubisco assembly.

We have performed a computational simulation of the aggregation and chaperonin-dependent reconstitution of dimeric prokaryotic ribulose bisphosphate carboxylase/oxygenase (Rubisco), based on the data of P. Goloubinoff et al. (1989, Nature 342, 884-889) and P. V. Viitanen et al. (1990, Biochemistry 29, 5665-5671). The aggregation is simulated by a set of 12 differential equations representing the aggregation of the Rubisco folding intermediate, Rubisco-I, with itself and with aggregates of Rubisco-I, leading up to dodecamers. Four rate constants, applying to forward or reverse steps in the aggregation process, were included. Optimal values for these constants were determined using the ellipsoid algorithm as implemented by one of us (Ecker, J.G. & Kupferschmid, M., 1988, Introduction to Operations Research, Wiley, New York, pp. 315-322). Intensive exploration of simpler aggregation models did not identify an alternative that could simulate the data as well as this one. The activity of the chaperonin in this system was simulated by using this aggregation model, combined with a model similar to that proposed by Goloubinoff et al. (1989). The model assumes that the chaperonin can bind the folding intermediate rapidly, and that the chaperonin complex releases the Rubisco molecule slowly, permitting time for its spontaneous folding while interacting with the chaperonin. This is followed by self-association of the folded Rubisco monomer to yield the active dimeric Rubisco. A modification of the model that simulates temperature effects was also constructed. The most important results we obtained indicate that the chaperonin-dependent reconstitution of Rubisco can be simulated adequately without invoking any catalysis of folding by the chaperonin. In addition, the simulations predict values for the association rate constant of Rubisco-I with the chaperonin, and other variables, that are subject to experimental verification.     

Beta beta homodimers exist in native rabbit skeletal muscle tropomyosin and increase after denaturation-renaturation.

Native tropomyosin from rabbit skeletal muscle (RSTm) consists mainly of alpha alpha and alpha beta coiled coils (alpha/beta approximately 3-4/1). In some extant studies, no beta beta molecules have been found. In this study, RSTm from several different preparations was disulfide cross-linked, both preparation and cross-linking being done under nondenaturing conditions. The cross-linked product was assayed for the presence of beta beta molecules cross-linked at both C36 and C190 (beta = beta). In such cross-linked RSTm, 3-8% beta = beta is detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis, C4 reversed-phase high-performance liquid chromatography, and a free-solution capillary electrophoresis experiment. This percentage becomes approximately 4-10% beta beta when corrected for incomplete double cross-linking and is independent of protein concentration (0.1-10.0 mg/mL), indicating that the observed beta beta species are not artifacts due to intermolecular cross-linking. Upon denaturation and subsequent renaturation either by heating to 55 degrees C or by incubating at 45 degrees C followed by quenching to room temperature, or by guanidine hydrochloride exposure followed by phased renaturation by dialysis, the fraction of beta beta increases, indicating that the reassociation favors homodimer formation somewhat over random association. This result differs from the random association observed when the sulfhydryl on one of the chains is carboxyamidomethylated (Holtzer, M.E., Breiner, T., & Holtzer, A., 1984, Biopolymers 23, 1811-1833), and from the overwhelming heterodimer preferences reported for tropomyosins from other organisms (Lehrer, S.S., Qian, Y., & Hvidt, S., 1989, Science 246, 926-928; Lehrer, S.S. & Qian, Y., 1990, J. Biol. Chem. 265, 1134-1138).     

青龙河底栖无脊椎动物群落结构及其水质评价

本文论述了青龙河底栖生物种类、数量、分布和结构等特点及其与环境因子间的关系。应用Beck、Gleason、Shannon、Simpson等生物指数对水质状况进行评价。结果表明青龙河除个别断面受污染外,大部分河段属尚清洁水。     

Species number, species abundance and body length of arboreal arthropods associated with an Australian rainforest tree

Abstract.

• 1 The species number, the abundance per species and the body length of arthropods foraging within the crowns of an over-storey rainforest tree from Australia, Argyrodendron actinophyllum (Sterculiaceae), were investigated by interception trap sampling and restricted canopy fogging. Emphasis was placed upon the interpretation of trap data. Arthropods were trapped continuously day and night, over a 2-year period and the final analyses examined the attributes of 759 species which represented 20,500 individuals.
• 2 The proportion of‘rare’species (Le. collected once) intercepted was high (35.7%), although lower than in other similar rainforest surveys. Neither the α log-series nor the log-normal distribution could be fitted to the relationship between number of species and number of individuals, since the number of rare species was much higher than predicted and the mode of the distribution could not be identified. The proportion of rare species was higher in fogging collections (452%) than in trap collections.
• 3 The data are compared with a study of Bornean arboreal beetles, obtained by fogging trees during a single sampling event. Several patterns were common to both data sets. However, the three-dimensional plot of the variables describing the structure of the arthropod community showed a notably rougher surface than in the case of Bornean beetles.
• 4 Although several factors may complicate the interpretation of the three-dimensional plots, long-term and continuous sampling may alter our perception of complex arthropod communities. This methodology is imperative for a proper understanding of arthropod community structure in rain forests.

     

Observations on the relation between phytoplankton diversity and environmental factors in the Vaal River at Balkfontein,South Africa

The relationship between specific environmental factors as independent variables and temporal changes in phytoplankton community structure in the Vaal River (a turbid system) during 1984 was investigated by employing different diversity indices. Temporal changes in community structure reflected temporal changes in certain environmental factors. Phytoplankton diversity, measured with Shannon-Wie H' and Hurlbert PIE indices, was related firstly to discharge and discharge derived variables (such as SO₄, Si, N and P loading) and secondly to turbidity derived variables (such as euphotic zone depth). Discharge appears to be of prime importance in affecting diversity. Observations were made that shed new light on conditions contributing to the development of an August peak (dominated by Stephanodiscus hantzschii fo. tenuis and Micractinium pusillum) in phytoplankton concentration. Increased environmental stress may reduce the number of sensitive species, thus reducing interspecific competition between tolerant species which could then exploit the — for them — more favourable conditions resulting in an increase in their numbers to peak concentrations.     

Pelagic rotifers of Lake Glubokoe from 1897 to 1984

After alteration in the pattern of drainage of run-off from the surrounding swamps and changes in the colour and transparency of the Lake Glubokoe water, the previously epilimnial Trichocerca similis, Conochilus unicornis and Keratella cochlearis showed a shift of their maximum numbers to deeper layers. Pompholyx sp. and Trichocerca capucina, which are regarded as indicators of eutrophic waters, have disappeared from the pelagic zone of the lake and Conochilus hippocrepis, Synchaeta pectinata, Gastropus stylifer, Asplanchna herricki, Ascomorpha ecaudis, Ascomorpha saltans, Euchlanis dilatata and Trichocerca porcellus have made their appearance. Most of the new species are considered to be indicators of oligotrophic conditions. However the total density of pelagic rotifers remained at the same level. Apparently the establishment of the new species of rotifers was possible due to some ‘rarefaction’ of the epilimnion, the disappearance of predaceous Mesocyclops leuckarti and the invasion of the pelagic zone by Peridinium cinctum.