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761.
Escape-swimming speeds (U
max) were studied in settled turbot (Scophthalmus maximus L.) reared at 18°C. Metamorphosis was complete at 4.0 cm total length (TL). U
max scaled in proportion to TL0.74 in fish of 0.88 5o 8.00 cm TL at 18C. The scaling relationship for U
max was similar for temperatures between 13 and 23°C and could be fitted by the model:
. U
max temperature-dependent, with a Q10 of 1.77 over the temperature range studied. Analysis of covariance showed that U
max for farmed turbot was 14% lower than for wild fish filmed within 2 wk of capture; 3 mo after capture the average differences in escape performance were no longer significant, which suggests that the lower escape speeds of farmed fish are due to acclimation effects and not genetic stock differences. In order to assess the individual variability of U
max, 18 wild juvenile turbot [TL=6.2±0.4 cm (Week 1) to 7.5±0.5 cm (Week 17); means±SD] were maintained in individual containers at 18°C. U
max was determined weekly for 6 wk, standardised for fish length using the scaling relationship U
max=1.46 TL
0.74, and individuals were ranked in order of performance. Temperature was reduced after 6 wk to 13°C, resulting in a significant decline in U
max from 104.0±14.4 to 87.8±12.5 cm s-1 (means±SD). After 3 wk at 13°C U
max had increased to a level not significantly different from that at 18°C. Kendall's coefficient of concordance showed that repeatability of ranking of the experimental U
max of individuals was maintained over a 13 wk period and through temperature change. The results demonstrate that escape-swimming speeds in juvenile turbot are repeatable, individually variable, and can be modified in response to temperature acclination. 相似文献
762.
Summary A comparative analysis of demographic variables for three populations of gelada baboons (Theropithecus gelada) showed that these were determined by a combination of environmental, demographic and social factors interacting in complex ways. Both birth rates and survivorship were found to be adversely influenced by the severity of local climatic conditions. These independently influenced adult sex ratio, which in turn determined the proportion of multimale reproductive units in the population. Mean harem size was found to be independent of all environmental and demographic factors with the sole exception of the proportion of harem-holding males, suggesting that it is mainly a consequence of social factors related to harem fission rates. Migration rates and band fission rates were related to population growth rates, these in turn being determined largely by local mortality and birth rates. 相似文献
763.
764.
Experimental etching with hydrofluoric acid indicated that silica deposition occurs in a recognizable pattern in common sponge microscleres. The postdepositional alteration of these spicules has previously been generally unrecognized or misinterpreted in the literature. Early stages of postdepositional etching of sponge spicules were observed in the acid insoluble fraction of sediments from the West Atlantic barrier reef near Carrie Bow Cay, Belize. Preliminary data on silica distribution in the Belize barrier reef show that concentrations in fine sediment (<0.25 mm) increase landward of the main reef tract. Sponge spicules are the main component of particulate silica in sediments of the reef and fore-reef where sponge populations abound, whereas grains prevail in the back-reef lagoon deposits. Recycling of locally dissolved silica appears to be important for the growth of many off-shore reef sponges. 相似文献
765.
Larvae of Pleuroncodes monodon (Milne-Edwards, 1837), a red crab of commercial importance in South America, were reared in the laboratory at 2 different temperatures (15° and 20°C), from hatching up to the last larval stage. The 5 typical stages, with their corresponding functional appendages, are described and figured. The main characteristics useful in differentiating larvae of P. monodon from those of the other Chilean species of Galatheidae and its northern congener P. planipes are discussed. Data on duration of each larval stage, length of moulting intervals and mortality at the 2 test temperatures are also given.This study was financially supported by the Chilean Ministry of Agriculture and by the National Commission for Scientific and Technological Research (CONICYT). 相似文献
766.
The reproductive status of the holothuroid species Isostichopus badionotus (Selenka, 1867) and Holothuria mexicana (Ludwig, 1875) was studied over 16 months in Bocas del Toro (Panama), from November 1999 to February 2001. Sexual reproduction was evaluated by the gonad index method, and by histology of gonad development. In addition, population structure was assessed based on sex ratio, minimum reproductive size, and length and weight distributions of males and females. The sex ratio in both species was 1:1, with a unimodal population distribution composed mainly of mature individuals. The minimum reproductive length and weight were 13-20 cm and 150 g, respectively, for both species, although reproductive individuals 10 cm in length were also found. A consistently higher gonad index was observed in H. mexicana, due to a high proportion of mature females and males and high gonad indices in most monthly samples. Gametogenesis and spawning patterns seemed to occur throughout the year, with periods of enhanced activity. Two periods of maximum reproductive activity were tentatively identified: July-November for I. badionotus and February-July for H. mexicana, but neither species had a single, sharply defined annual spawning event. Further work on these exploited holothuroids should examine the relationships between reproduction and environmental factors and between reproductive status and recruitment. 相似文献
767.
Biosorption of Cr(VI) using low cost sorbents 总被引:2,自引:0,他引:2
N. Fiol I. Villaescusa M. Martínez N. Miralles J. Poch J. Serarols 《Environmental Chemistry Letters》2003,1(2):135-139
Waste products from industrial operations, such as yohimbe bark, grape stalks, cork and olive stones were investigated for
the removal of Cr(VI) from aqueous solutions. Equilibrium batch experiments at room temperature were performed. Metal uptake
showed a pH-dependent profile and optimum uptake at initial pH between 2.0–3.0. Slight influence of NaCl on metal uptake was
observed. The sorption data fitted well to the Langmuir model within the concentration range studied. Grape stalks proved
to be the most efficient sorbent followed by yohimbe bark, cork and olive stones.
N. Fiol is the recipient of the 2002 ACE Environmental Chemistry Award 相似文献
768.
769.
A change in the Si:N ratio of diatom cells during growth was examined for Chaetoceros socialis and Thalassiosira sp., with different initial silicate to nitrate (Si:N) ratios in the media. During exponential growth, C. socialis assimilated silicate and nitrate with a molar ratio of 0.5, independent of the ratio in the media, but after the depletion of nitrate, silicate continued to be taken up, and the Si:N ratio in the stationary phase increased to 2 as a function of the Si:N ratios in the media. In contrast, the ratio of silicate to nitrate taken up by Thalassiosira sp. increased with an increase in the Si:N ratio in the media. The Si:N ratio in the cells during the stationary phase increased in response to an increase in this ratio in the media. The Si:chl a ratio also increased with the increase in the initial Si:N ratio in the media, while the N:chl a ratio did not change to a great extent, indicating the changes in the cellular Si:N ratio was derived from changes in the Si content of the cells. These results indicated that the cellular Si:N ratio changed with the Si:N ratio in the medium, and the Si:N uptake ratio during the growth phase was different depending on diatom species. Thus, the dominance of different diatom species may affect nutrient composition and dynamics in the ocean. 相似文献
770.