Integumental ultrastructure and color patterns in the iridescent copepods of the family Sapphirinidae (Copepoda: Poecilostomatoida)

The ultrastructure of the integument of the sapphirinid copepods was studied by scanning and transmission electron microscopy. Samples were collected between 1991 and 1993 by plankton-net tows from the subtropical and tropical waters of the North Pacific. In all the seven species examined of Sapphirina and Copilia, a structure with multilayered platelets was found in the epidermal cells of the dorsal integument of the male. Each platelet is a regular hexagonal prism. The platelets form a plate with honeycomb arrangement within each epidermal cell. Just ventral to the dorsal cuticle, 10 to 14 plates are located parallel to each other and to the cuticle. The mean diameter and thickness of the platelets measured between 1.0 and 1.8 m and 61 and 83 nm, respectively, for the four species. The specific coloration of seven species was examined with reflected and transmitted light. The iridescent color may be explained by the theory of multiple thin-layer interference in some species which are considered to have an ideal laminar structure, but for the other species, mechanisms from non-ideal systems, including pigment-thin layer interaction, may also be involved.     

Reproduction and growth of the freshwater prawn, Palaemon paucidens (Decapoda: Palaemonidae) in a lake of Korea

This study analyzed the reproduction and growth of freshwater prawn, Palaemon paucidens De Haan 1844 from Suk-dang lake(Korea). The analysis of the sex ratio showed a higher proportion of males than that of females. The average size of the eggs was 6.12 (+/-0.55) mm3 in the non-eyed stage (stageA) and 7.20 (+/-0.86)mm3 in the eyed stage (stage B). The reproductive output (RO) calculated with the dried-body weight of an incubating female and the weight of the eggs in dried condition was 26.97% (n = 17) of the average females weight. Incubating prawn appeared in April, and the gonadosomatic indices(GSI) showed the highest value during three months from January to March. Based on the month when there was a high proportion of incubating females with a high GSI, the estimated spawning season of P. paucidens was April. The maturity of the female was evaluated by the development of the ovaries and the existence of eggs. The average body length when 50% of the females in the group reached maturity was 8.55 (+/-2.74) mm. The analysis of the length-frequency distribution showed that the life span of P. paucidens ranged from 12 to 13 months. Females mature faster than males.     

Mercury contamination in agricultural soils from abandoned metal mines classified by geology and mineralization

Lead (Pb) contents and partition in soils collected from eleven vegetable-growing lands in Fujian Province, China, were investigated using a modification of the BCR (Community Bureau of Reference) sequential extraction procedure coupled with the Pb isotope ratio technique. Pb contents in Chinese white cabbage (B. Chinensis L.) grown on the lands for this study were also measured. Results showed that Pb concentrations in fifty samples of topsoil ranged from 456 to 21.5 mg kg⁻¹, with each mean concentration of six sampling lands exceeding the national standard (50 mg kg⁻¹); while Pb concentrations in edible portions of thirty-two vegetable samples ranged from 0.009 to 2.20 mg kg⁻¹, with four sampling sites exceeding the national sanitary standard (0.2 mg kg⁻¹). A significant correlation (r = 0.971, P < 0.01) of Pb contents in the acid-extractable fractions by BCR approach and the vegetables was observed, which indicates that the acid-extractable Pb is useful for evaluating the metal bioavailability for plants and potential risk for human health in soils. The determination of lead isotope ratios in different chemical forms of soils by BCR sequential extraction procedures provides useful information on the Pb isotopic composition associated with different soil fractions (especially in the acid-extractable fractions), and the result is helpful for the further study on controlling and reducing Pb contamination in vegetable-growing soils.     

The effects of soil properties on the turbidity of catchment soils from the Yongdam dam basin in Korea

Environmental concerns have been raised that suspended solids in turbid water adversely affect human health, and that their removal increases in the cost of water treatment. The Yongdam dam reservoir, located in the southwestern region of Korea, is severely affected by inflowing turbid water after storms. In this study, soil samples were collected from 37 sites in the Yongdam upstream basin to investigate mineralogical and environmental factors associated with the turbidity potential of soils in water environments. Turbidity potential was estimated by measuring the turbidity of soil-suspension solutions after settling for 24 h. The mineralogy of the soils was dominated by four minerals—quartz, microcline, albite, and muscovite—with lesser amounts of hornblende, chlorite, kaolinite, illite, and mixed layer illite. The quartz content was the most variable of the soil mineralogy among the collected samples. Principal-components analysis (PCA) was used to examine relationships between turbidity potential and other soil properties. The variables considered in the PCA included turbidity potential, quartz content, albite content, mean size of soil particles, clay content, clay mineral content, zeta potential, conductivity, and pH of the soil-suspension solution. The first two components of the PCA explained 52% of the overall variation of the selected variables. The first component was possibly explained by physical properties such as the size of the soil particles; the second was correlated with chemical properties of the soils, for example dissolution and extent of weathering. Closer examination of the PCA results revealed that the quartz content of the soils was negatively correlated with their turbidity potential. A linear correlation (r = 0.63) was obtained between measured turbidity potential and that predicted using multiple regression analysis based on the content of clay-sized particles, clay minerals, and quartz, and the conductivity of the soil-suspension solution.