Length-weight regressions of the microcrustacean species from a tropical floodplain

AIM: This study presents length-weight regressions adjusted for the most representative microcrustacean species and young stages of copepods from tropical lakes, together with a comparison of these results with estimates from the literature for tropical and temperate regions; METHODS: Samples were taken from six isolated lakes, in summer and winter, using a motorized pump and plankton net. The dry weight of each size class (for cladocerans) or developmental stage (for copepods) was measured using an electronic microbalance; RESULTS: Adjusted regressions were significant. We observed a trend of under-estimating the weights of smaller species and overestimating those of larger species, when using regressions obtained from temperate regions; CONCLUSION: We must be cautious about using pooled regressions from the literature, preferring models of similar species, or weighing the organisms and building new models.

Otolith mass asymmetries in the utricle and saccule of flatfish

The otolith mass of the saccules and utricles of plaice, Pleuronectes platessa (n = 39) and turbot, Psetta maxima (n = 21) was measured using an electronic microbalance. In the right-eyed plaice, the left utricular otoliths were found to be significantly heavier than the right (p < 0.0001), whereas no significant difference was found between left and right saccular otoliths (p < 0.751). In the left-eyed turbot, both the right utricular and saccular otoliths were found to be significantly heavier (in both cases, p < 0.0001). While the gene and regulative protein responsible for the peripheral biomineralisation process have been identified, it remains unclear how the symmetry between the right and left otoliths in fish species is regulated. Here it is likely that an additional central mechanism is involved. It must be assumed that similar processes govern the systematic asymmetry observed in flatfish such as the plaice and turbot. Taken together these findings are strongly suggestive of concomitant CNS modification and metamorphic plasticity, presumably represented in genetic code.

The Kinetic Investigation of the Deposition of Alumina and Aluminosilicates from Mixtures of SiCl4, AlCl3, CO2, and H2

The codeposition of alumina, silica, and aluminosilicates from mixtures of silicon tetrachloride, aluminum trichloride, carbon dioxide, and hydrogen is investigated in this study. Chemical vapor deposition experiments are carried out in a hot-wall reactor of tubular geometry coupled with an electronic microbalance. In order to elucidate some aspects of the codeposition process, the deposition of pure alumina and pure silica from mixtures of silicon tetrachloride and aluminum trichloride, respectively, with CO2 and H2, is also investigated. Among the most interesting findings of our study is that the presence of AIC13 has a catalytic effect on the incorporation of silica in the deposit, leading to codeposition rates that are higher than the deposition rates that are obtained when only one of the two chlorides (SiCI4 or A1C13) is present in the feed