Hon-g Chen

Histopathological and biochemical evidence of hepatopancreatic toxicity caused by cadmium and zinc in the white shrimp, Litopenaeus vannamei.

The white shrimp, Litopenaeus vannamei, a globally important cultured prawn species, is an ideal animal for studying the impairment caused by the effects of heavy metals that are often detected in coastal areas. In this study, L. vannamei was exposed to different concentrations of cadmium (Cd) and zinc (Zn) for up to 28 d. Histopathological alterations in the hepatopancreas were observed in L. vannamei after long-term exposure to Cd and Zn. Hepatopancreatic injury was further confirmed by the inductions of two biochemical markers, hemolymphatic glutamate-oxalacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT). It was notable that L. vannamei was able to repair its hepatopancreas from the damage caused by Zn, which was evidenced by the results of the histopathological observations, determinations of tissue metal concentrations, and examination of GOT and GPT levels.

Effects of gallium on common carp (Cyprinus carpio): acute test, serum biochemistry, and erythrocyte morphology

Gallium (Ga) is one of the intermetallic elements that are increasingly being used in making high-speed semiconductors such as gallium arsenide. The purposes of this study were to investigate the effects of gallium on acute toxicity, on serum biochemical variables as well as on erythrocyte morphological changes in the blood stream of common carp (Cyprinus carpio). Median lethal concentrations were determined in acute tests. The 96-h LC50 value was 19.78 (18.49-21.16) mgl(-1). Common carp were exposed to different gallium concentrations (2.0, 4.0, and 8.0 mgl(-1)) for 28 days in laboratory toxicity tests. Means of the measured serum biochemistry parameters (including glucose, blood urea nitrogen, creatinine, cholesterol, and triglyceride) of these exposed groups significantly differed from those of the untreated group. Deformation of erythrocytes suggest disturbance of respiration as an additional indicator of Ga exposure. Our results suggest that 2.0 mgl(-1) is proposed as a biologically safe concentration which can be used for establishing tentative water quality criteria concerning of same size common carp. In addition, serum biochemical parameters as well as erythrocyte morphological changes are promising clinical diagnostic tools for assessing the effects of gallium compounds on common carp.

Effects of dietary protein concentration on growth and muscle composition of juvenile Zacco barbata

The effects of dietary protein concentration on growth and muscle composition of juvenile Zacco barbata were investigated using white fish meal as the major protein source. Six experimental moist diets containing 20.5 to 45.3% protein were fed to triplicate groups of 16 fishes (0.338±0.002 g) for 10 weeks. There was no mortality among test fishes throughout the experiment. Specific growth rates and feed conversion ratios for fish fed diets containing 30.7, 35.2, 40.9, and 45.3% protein were better (P<0.05) than those fed diets containing 20.5 and 25.8% protein. Fish fed 35.2, 40.9, and 45.3% protein diets excreted more (P<0.05) ammonia than fish fed diets containing 20.5 and 25.8% protein. Fish on the lowest protein diet (20.5%) showed the highest protein efficiency ratio. Fish fed high-protein diets had higher protein and ash content in their muscle. Whereas, fish fed high-protein diets had lower lipid content in muscle than those fed low-protein diets. Analyzed by a broken-line model with final body weight as the indicator, the optimal dietary protein level for Z. barbata is approximately 32.0±0.1%.

Effects of chlordane and lindane on testosterone and vitellogenin levels in green neon shrimp (Neocaridina denticulata).

The purpose of this study was to investigate the acute toxicity of chlordane and lindane as well as their endocrine disruption effect on green neon shrimp (Neocaridina denticulata), a common habitant in freshwater system of eastern Asia and Hawaii. First, the organisms were exposed to chlordane and lindane to estimate the 96-h LC50(96-h median lethal concentration). Then, levels of testosterone and vitellogenin in hemolymph of N. denticulata after exposure to sublethal concentrations of chlordane (1 ng/L and 10 ng/L) and lindane (0.1 μg/L and 1 μg/L) were also examined. The 96-h LC50 values obtained from the results of acute exposure were 127.03 (130.11–122.35) ng/L and 9.36 (8.00–10.96) μg/L for chlordane and lindane, respectively. Furthermore, reductions of testosterone concentration were observed in both chlordane- and lindane-treated shrimps, whereas induction of vitellogenin-like protein was only apparent in chlordane-treated shrimps. Thus, it is concluded that chlordane and lindane may probably show some disruption endocrine functions on N. denticulata.

Bioaccumulation and Toxicodynamics of Cadmium to Freshwater Planarian and the Protective Effect of N-Acetylcysteine

Although toxic responses of freshwater planarians after exposure to environmental toxicants can be observed through external toxicological end points, physiological responses inside the bodies of treated planarians have rarely been investigated. The present study was designed, using cadmium (Cd) as a reference toxicant, to determine its bioaccumulation and toxicodynamics in the freshwater planarian, Dugesia japonica, after acute toxicity was obtained. Accumulated Cd concentrations, metallothionein levels, and the oxidative status in planarians were determined after exposure to Cd. Furthermore, we hypothesized that the acute death of Cd-treated planarians was associated with increased oxidative stress. After Cd-treated planarians were coexposed to antioxidant, N-acetylcysteine (NAC), we found that NAC protected planarians from Cd lethality by maintaining the oxidative status and decreasing the bioaccumulation of Cd. The results of the present study support planarians being used as a practical model for toxicological studies of environmental contaminants in the future.

Toxic effects of mercury on the hard clam, Meretrix lusoria, in various salinities

1. The 96-hr lc50 values for juvenile hard clams, Meretrix lusoria, were 328, 392 and 194 μg/l Hg in 10, 20 and 30 ppt salinities at 25 ± 1°C, respectively; for adult hard clams 341 and 140 μg/l Hg in 20 and 30 ppt salinities, respectively. 2. Acclimatizing the adult clams to low salinity of 10 ppt lessened the toxicity of mercury. However, juvenile animals appeared to be more sensitive to mercury poisoning after 96 hr exposure in 10 ppt salinity. 3. All embryos exposed to 40 μg/l Hg and above died within 30 hr. In the control, 44% of hatched embryos had developed into D-stage larvae, while those exposed to 20 μg/l Hg were still in the trochophore stage. Most of the retarded larvae developed into abnormal forms within 30 hr at 28°C in 15 ppt salinity. 4. In order to maintain water quality and protect natural resources, the recommended safe level of mercury is 0.046 (0.039–0.053) μg/l Hg, based on the estimated 30-hr EC50 for the clam embryos, with an application factor of 0.01.

Desiccation resistance of two semiterrestrial isopods, Ligia exotica and Ligia taiwanensis (Crustacea) in Taiwan.

The ability to resist desiccation stress was examined in two semiterrestrial Ligia species, Ligia exotica Roux and L. taiwanensis Lee, in Taiwan, under a certain desiccation condition. L. exotica exhibited the longer survival time, lower weight-specific rates of water loss, and the slightly higher ability of tolerance to water loss, compared to L. taiwanensis. In each species, the animal size displays a positive correlation to the survival time and total ability to resist desiccation, yet this size effects on the weight-specific water loss rate is negative. Neither water content nor maximum tolerance to water loss shows the association with the animal size in both species. The path ways and magnitudes of the interactions between these traits of desiccation resistance are analyzed and diagrammed using a stepwise regression model. In this model, the body sizes of animal can explain the most part of the variations in the survival time. The body size has a direct effect and an indirect effect, through the effect on water loss rate, on the time that the experimental animals can survival under this desiccated condition. These results suggest that L. exotica attains larger size than does L. taiwanensis, a lower transpiration rate and, consequently, a greater ability in desiccation resistance. The performances of these interactions in the desiccated resistance are more advantageous for L. exotica to migrate and colonize in variable land habitats within a certain limit, and as a result that L. exotica shows a broader distribution pattern than did L. taiwanensis in Taiwan.

Responses of Two Semiterrestrial Isopods, Ligia exotica and Ligia taiwanensis (Crustacea) to Osmotic Stress

When immersed in fresh water, Ligia taiwanensis is a poorer osmoregulator than Ligia exotica ,a s judged by a lower LD50 at 96 hr and by the osmolalities of haemolymph. Animals appear to osmoregulate more efficiently in air. On immersion, both species displayed hyper- and hypo-osmoregulatory ability. Both species subjected less osmotic selection pressure during their inland colonization. The results suggest that a route of terrestrial colonization not involving transitional freshwater stresses had been taken by L. exotica and L. taiwa- nensis. comp biochem physiol 118A;1:141-146, 1997.

Sublethal Effects of Paraquat and Malathion on the Freshwater Shrimp, Macrobrachium nipponense

In this research, we compared the responses of a freshwater shrimp (Macrobrachium nipponense), including food consumption, oxygen consumption, and body weight change, after paraquat and malathion exposure. The effects of these two pesticides on the feeding rates were remarkable. Feeding rates of this shrimp decreased when it was respectively exposed to increasing concentrations of both paraquat and malathion. As to body weight, when the concentration of paraquat and malathion increased, body weight decreased, and paraquat had a stronger effect than malathion. As to oxygen consumption, although there was a decrease in weight-specific oxygen consumption for both the control and exposed groups, the decrease was greater in exposed shrimp in relation to the dissolved oxygen concentration.

Genetic Variation of the Viviparid Snail, Sinotaia Quadrata (Gastropod: Viviparidae), in Taiwan

Allozyme electrophoresis was used to assess the genetic variation and population structure of a Taiwanese viviparid snail, Sinotaia quadrata. Five of 17 loci were polymorphic, but a deficiency of heterzygotes for all loci was observed. Values for Neis genetic distances among the SIX populations were small, with a mean value of 0.0061. The phenogram constructed using the UPGMA method revealed that the six groups of viviparids could be clustered into northern and southern-eastern groups. The fixation index (Fst) was low (mean = 0.056), and the effective number of migrants was high (Nm = 6.5846). However, no correlation between genetic distance and geographical distance was detected (r2 = 0.0636, p = 0.364). Gene now probably due to aquaculture activities has resulted in high genetic similarity among populations of S. quadrata.