Effects of mercury on embryonic development and larval growth of the sea urchin Echinometra mathaei from the Persian Gulf

This study investigated the effects of increasing mercury (Hg) concentration on early developmental stages of sea urchin, Echinometra mathaei, as a bioindicator. The toxicity test was carried out after the gamete released induction and fertilization in six concentrations of mercury within the range of 4, 8, 16, 32, 64 and 128 µg/L. Embryos samples were incubated for 30 h in control and test solutions. After incubation, the percentage of developed 4-arm pluteus larvae was recorded in each group and embryonic abnormalities were studied by a microscope. Results of this study indicate that exposure of embryos to increasing mercury concentrations lead to abnormalities such as changes to shape and size of pluteus larval arms and also arrested development in early embryonic stages. Furthermore, embryos were analyzed to determine mercury absorption by cold vapour atomic absorption spectrometry method (AAS). The median effective concentration (EC50) value calculated for mercury was 17/42 µg/L

Determination of developmental stages of embryo in the sea urchin, Echinometra mathaei

Sea Urchin is one of the most useful tools in developmental biology studies because this organism has the simplest kind of developmental stages. We aimed to determine developmental stages and timetable of Echinometra mathaei embryo (the species of Persian Gulf). The spawning of E. mathaei was induced by 0.5M KCl injection (1ml) into the coelomic cavity. After fertilization, embryos were placed in beakers and were incubated at 29°C and a salinity of 39 ppt until embryos reached the pluteus stage. The developmental stages of embryos and the timing of each stage including cleavage, morulae, blastula, gastrula, prism and pluteus larvae were studied under the microscope. Our results showed that after 30 hours from fertilization time, the embryos developed to pluteus larvae. E. mathaei had the shorter development time in comparison to the other Sea Urchin species. Therefore, it may be appropriate as a model organism in biological researches

Agglomeration in counter-current spray drying towers. Part A: Particle growth and the effect of nozzle height

Agglomeration of particles and droplets is critical to the operation of spray dryers, however it remains relatively unexplored. This paper studies the effect of the nozzle height on product properties, wall deposits and dryer conditions in a counter-current spray drying tower of detergent with a swirling air flow. The process efficiency is driven by changes in particle agglomeration. To interpret the results and facilitate the study of swirl towers, it is useful to subdivide these units according to the sources of growth in (a) spray region(s), (b) concentrated near-wall region(s) and (c) wall deposits. The particles formed are very heterogeneous and show a size-dependent composition. In this case, particle properties are driven by the separation of solid and liquid phases during atomization and the formation of a heterogeneous set of droplets. Agglomeration serves to homogenise the product and create a distinct source of porosity. The capacity and energy consumption of the dryer are also determined by the evolution of the particle size, as fine powder is elutriated from the tower top and coarse particles are removed from the product. When the nozzle is moved to lower positions in the tower the increased temperature near the spray suppresses agglomeration, however the residence time is shortened and ultimately it leads to creation of wet, coarse granules. An optimum location is found high enough to maintain the drying efficiency but sufficiently far from the top exit to minimise the loss of fine particles. In this way, a capacity ratio (i.e. product vs spray dried powder) C > 90% can be obtained and energy efficiency maximised