Temperature and metabolic rate in sedentary fish from the Antarctic,North Sea and Indo-West Pacific Ocean

Resting metabolic rate was measured in demersal stages of the teleostNotothenia neglecta Nybelin from the South Orkney Islands, Antarctica, from 1985 to 1987. The relationship between and body mass (Mb) conformed to the general relationship , wherea is a proportionality constant andb is the scaling exponent. (mg O₂ h^–1) was found to scale toMb ^{(0.82±0.011)} in the summer (November to April, 1.6 to 1 850 g,n=56) and toMb ^{(0.76±0.013)} in the winter (May to October, 0.9 to 1 850 g,n=57) (values ofb are means ± SD). Although the scaling exponents were significantly different (P<0.01), was similar in the juvenile stages of summer- and winter-caught fish matched for body mass. The effects of activity on oxygen consumption was studied using a Brett respirometer. Adult stages had a factorial aerobic scope for activity of 5.7, which is similar to that reported for demersal fish from temperate latitudes. The effects of temperature on resting metabolism was investigated in fish with similar sedentary lifestyles from the North Sea (Agonus cataphractus andMyoxocephalus scorpius) and the Indo-West Pacific (Paracirrhites forsteri, P. arcatus, Neocirrhites armatus andExallias brevis). Extrapolated values of for the tropical species approached zero at 5 to 10°C. For a standard 50 g fish, for the tropical species at 25°C was in the range 3.4 to 4.4 mg O₂ h^–1, compared with 1.3 mg O₂ h^–1 forNotothenia neglecta at its acclimation temperature. Thus, the maximum metabolic rate of sedentary tropical species at 24°C is likely to be 2 to 4 times higher than inN. neglecta at 0°C. This suggests that the energy available for sustained activity is significantly lower in cold- than in warm-water fish.     

Dominions and desert clickers (Orthoptera:Acrididae): influences of resources and male signaling on female settlement patterns

Summary Previous field work on the grasshopper Ligurotettix coquilletti revealed that females were not evenly distributed among male mating territories, Larrea tridentata (creosote) bushes, but were clustered at particular locations. These sites generally harbored several signaling males simultaneously and also possessed foliage preferred by the insects as a food source, this preference being based on the relative concentrations of various extra-foliar compounds. The clustering of females, therefore, could result from a preference for specific bushes because of the resources (i.e., food) available there and/or an orientation to groups of males per se. Here, we present the results of 3 field experiments in which we controlled the spatial distribution and intensity of male signals using a computer-operated system of loudspeakers and monitored the movement of individually marked females released in the study area. When male song was identical at high and low quality territories (all having single loudspeakers), females still aggregated at the high quality sites, indicating that variability in host plant quality alone may be sufficient to promote a skewed distribution of females. Among high quality territories, females did not discriminate between sites with one versus three loudspeakers (all broadcasting the same signal), but displayed a strong preference for sites (all having single loudspeakers) with a high intensity signal over a low intensity one. Field measurements showed that the songs of grouped males were more intense than those of lone males, implying that the signaling of grouped males may have enhanced the settlement of females at the bushes harboring male groups above and beyond that influenced by territory quality alone. We conclude that female attraction to host plants is influenced primarily by male signaling, whereas their subsequent retention is more dependent on territory quality. An experiment on male settlement failed to show an aggregative tendency, suggesting that male groups form through the passive accumulation of individuals at high quality sites.     

Song as an attractant for male and female European starlings,and the influence of song complexity on their response

Summary We tested the hypothesis that song attracts females and repels males in the European starling. We broadcast recorded song from speakers attached to nestboxes, while paired boxes with silent speakers served as controls. As predicted, females were attracted to the song boxes. Contrary to prediction, males were also attracted to the `song' boxes. Singing by male starlings may be costly because it attracts competitors for limited nesting sites, but the cost cannot be avoided due to the need to attract a mate. In a second experiment simple song (composed of 20 different phrase types) and complex song (40 phrase types) were played simultaneously. More males were captured at boxes where simple song was played. Song complexity may function as an indicator of male quality and be used by male starlings to assess potential competitors.     

Determination of biomass burning emission factors: Methods and results

Biomass burning, in a broad sense, encompasses different burning practices, including open and confined burnings, and different types of vegetation. Emission factors of gaseous or particulate trace compounds are directly dependent both on the fuel type and the combustion process. Emission factors are generally calculated by stoichiometric considerations using the carbon mass balance method, applied either to combustion chamber experiments or to field experiments based on ground-level measurements or aircraft sampling in smoke plumes. There have been a number of experimental studies in the last 10 years to investigate wildfires in tropical, temperate, or boreal regions. This article presents an overview of measurement methods and experimental data on emission factors of reactive or radiatively active trace compounds, including trace gases and particles. It focuses on fires in tropical regions, that is, forest and savanna fires, agricultural burns, charcoal production, use of fuelwood, and charcoal combustion.     

Life-history parameters and vertical distribution of Maurolicus muelleri in Masfjorden in summer

Population characteristics, individual life-history variables, feeding and vertical distribution of the mesopelagic fish Müller's pearlside Maurolicus muelleri collected in 1990 in Masfjorden, western Norway, are reported as well as environmental variables from the fjord. Minimum size at maturity was far smaller than reported from previous investigations in the same region. Fecundity was size-dependent and total egg numbers were higher than reported from other investigations of M. muelleri world wide, while the number of maturing eggs was far lower than observed in the same region earlier. Food concentration in the fjord was an order of magnitude lower than previous early summer observations, and several factors indicated that feeding opportunities may have been low for a long period. Daily feeding rate (g prey g^-1 fish) decreased with increasing fish size. These observations fit well with a model of maximizing fitness by means of a flexible size at maturity. Minimum age at maturity seems to be achieved at the expense of fecundity. M. muelleri was concentrated in a 20 to 30 m deep sound scattering layer (SSL). The SSL stayed close to the surface during the night and at 100 to 180 m during the daytime. The vertical position of the SSL varied instantaneously with changes in surface light intensity, remaining at 10^-3 to 10^-4 mol m^-1 s^-1 at the top of the SSL. Stomach fullness was highest during the night; feeding intensity seems to have been peaked at dusk. Cladocerans were the main prey ranked by number, copepods by biomass. Intake of large copepods increased with fish size.     

Biodegradation of undecylbenzenesulphonate by mixed methane-oxidizing culture

Biodegradation of undecylbenzenesulphonate (C(11)LAS) was performed in shake flasks at 21 degrees C by using a mixed methanotrophic-heterotrophic culture containing type II methanotrophs. Concentrations of C(11)LAS and aromatic intermediates were determined by reversed-phase high-performance liquid chromatography (RP-HPLC). Methane and carbon dioxide concentrations were measured in headspace samples by using gas chromatography. RP-HPLC analyses of aqueous samples show that the culture MM1 expresses the capability of C(11)LAS transformation in the presence or absence of methane. Simultaneous methane oxidation and C(11)LAS degradation, and the inhibition of both transformation processes by acetylene were observed. This suggests the possibility that C(11)LAS transformation is catalyzed by methane monooxygenase (MMO). Comparable affinity of culture MM1 for both methane and C(11)LAS ( [Formula: see text], respectively), and more than four times higher maximum transformation rate for methane than for C(11)LAS ( [Formula: see text] (dry weight) cells day(-1), respectively), were determined. This further supports the involvement of MMO enzyme system in transformation and suggests a pronounced competitive inhibition of C(11)LAS degradation by methane.