The changes of heavy metal and metallothionein distribution in testis induced by cadmium exposure

Cadmium (Cd) is known to cause various disorders in the testis, and metallothionein (MT) is known as a protein, which has a detoxification function for heavy metals. However, the changes of Fe, Cu, and Zn distribution in the testis induced by Cd exposure have not been well examined. Moreover, only a few studies have been reported on the localization of MT after Cd exposure. In this study, we have investigated the changes of Fe, Cu, and Zn distribution in Cd-exposed testis by a newly developed in air micro-Particle Induced X-ray Emission (PIXE) method. Also, we examined the distribution of MT expression in testis. In the testis of Cd-treated rats with significant increases of lipid peroxidation, the sertoli cell tight junction was damaged by Cd exposure, resulting from disintegration of the blood testis barrier (BTB). Evaluation by in air micro-PIXE method revealed that Cd and Fe distribution were increased in the interstitial tissues and seminiferous tubules. The histological findings indicated that the testicular tissue damage was advanced, which may have been caused by Fe flowing into seminiferous tubules followed by disintegration of the BTB. As a result, Fe was considered to enhance the tissue damage caused by Cd exposure. MT was detected in spermatogonia, spermatocytes, and Sertoli’s cells in the testis of Cd-treated rats, but was not detected in interstitial tissues. These results suggested that MT was induced by Cd in spermatogonia, spermatocytes, and Sertoli’s cells, and was involved in the resistance to tissue damage induced by Cd.     

Metallothionein induction in early larval stages of tilapia (Oreochromis mossambicus)

Amounts of whole-body metallothionein (MT) in tilapia (Oreochromis mossambicus) larvae increased to a peak (1,500 ng mg(-1) protein) 1 d after hatching (H1), decreased rapidly thereafter, and was maintained at a constant level (700 ng mg(-1)) 3 d after hatching (H3). Waterborne Cd(2+) could stimulate MT expression in newly hatched (H0) larvae in dose-dependent and time-dependent patterns. H0 larvae, which were treated with 35 microg L(-1) Cd(2+) for 24 h, showed a 1.7-fold increase in the MT amount (174.0+/-64.7) and a 6. 5-fold increase in accumulated Cd(2+) but no significant change in Ca(2+) content, compared with the H0 control (MT, 102.6+/-48.1). H3 larvae with the same treatment revealed about a 10-fold increase in accumulated Cd(2+), a 10% decrease in Ca(2+) content, but no change in MT (261.2+/-120.0), compared with the H3 control (MT, 330+/-74.0). H0 larvae could synthesize more MT to bind Cd(2+) for detoxification in 35 microg L(-1) Cd(2+), a dose that would not affect normal physiology or survival of H0 larvae. On the other hand, 35 microg L(-1) Cd(2+) caused H3 larvae to experience hypocalcemia, an abnormal physiological condition, in which H3 larvae could not synthesize sufficient MT, thus causing greater than 25% mortality. These results indicate for the first time that the inducibility of MT by waterborne Cd(2+) is development dependent, being correlated with inconsistent sensitivities to Cd(2+) during larval development.     

Effects of cadmium chloride on the development of rainbow trout Oncorhynchus mykiss early life stages

The sub-chronic (28–56 days) effects of exposure to low concentrations of cadmium (Cd; 0·05, 0·25, 0·50 and 2·50 μg l⁻¹) shortly following fertilization on embryos, larvae and juvenile rainbow trout Oncorhynchus mykiss were examined. Premature hatching occurred at lower concentrations (0·05 and 0·25 μg l⁻¹ Cd), however, delayed hatching was seen in the 2·50 μg l⁻¹ Cd group, with >90% of hatching occurring on the last day of the hatching period. Larval growth was negatively affected by Cd exposure in a concentration-dependent manner. Larvae exposed to 2·50 μg l⁻¹ Cd were 13·9 ± 0·8% shorter in total length ( L _T) and weighed 22·4 ± 3·5% (mean ± s . e .) less than controls at the end of the exposure period. Plasma sex steroid concentrations (oestradiol in juvenile females and 11-ketotestosterone in juvenile males) were elevated (four- to 10-fold over controls) in exposed fish in both males and females, following 28 days of exposure to 0·05, 0·25 and 0·50 μg l⁻¹ Cd, respectively. These results suggest that environmentally realistic concentrations (in the μg l⁻¹ range) of Cd can affect the development of O. mykiss impacting embryos, larvae and juvenile fish.     

Cadmium is deposited in the gut content of larvae of the beetle Tenebrio molitor and involves a Cd-binding protein of the low cysteine type

Binding of cadmium (Cd) to metallothionein (MT) and non-MT proteins with low contents of cysteine has been observed in terrestrial arthropods. We recently isolated a Cd-binding protein with no cysteine that was induced in Cd-exposed larvae of the beetle Tenebrio molitor. In this study we have examined the molecular distribution of Cd within extracts of different tissues and compartments of Cd-exposed T. molitor larvae. A Cd-peak consistent with the low cysteine Cd-binding protein was induced within the gut content where it could be detected after 4-8 days of exposure. Examination of gut wall tissue revealed no increase in Cd-binding capacity, indicating that no accumulation of MTs was taking place in this tissue. Incorporation of Cd in the gut wall tissue stabilized after 8 days of Cd-exposure at a rather low level compared to the other organs. There was a statistical trend towards Cd being incorporated in the gut content in a manner that was disproportionally high compared to the amount of Cd in the gut wall tissue. The possible role of the low cysteine Cd-binding protein in reducing the uptake of Cd in the tissues is discussed.     

光照强度与光周期对虎斑乌贼胚胎发育的影响

为探究光照对虎斑乌贼受精卵孵化的影响,确定其胚胎发育的最佳光照条件,本研究采用单因子试验方法,分析了不同光照强度(10、30、50、70、90 μmol·m^-2·s^-1)和光周期L∶D(24 h∶0 h、18 h∶6 h、12 h∶12 h、6 h∶18 h、0 h∶24 h)对虎斑乌贼胚胎发育的影响.结果表明: 不同光照强度对虎斑乌贼胚胎发育的孵化率、卵黄囊断裂率、培育周期、初孵幼体体质量与胴长均影响显著;而对孵化周期和幼体出膜7 d后存活率无显著影响.其中孵化率、培育周期、初孵幼体体质量与胴长随着光照强度的增强先增大后减小,而卵黄囊断裂率则逐渐增大.最适光照强度为30 μmol·m^-2·s^-1,此光照强度下孵化率为(90.0±4.1)%,卵黄囊断裂率为(7.3±1.5)%,培育周期为(25.50±0.35) d,孵化周期为(8.10±0.89) d,初孵幼体体质量为(0.213±0.011) g,胴长为(1.013±0.022) cm,出膜7 d后存活率为(97.1±4.0)%.不同光周期对虎斑乌贼胚胎发育的孵化率、培育周期、孵化周期均影响显著,而对卵黄囊断裂率、初孵幼体体质量、胴长和幼体出膜7 d后存活率无显著影响.其中孵化率和孵化周期随着光照时间的增加呈现先增大后减小的变化.最适光周期为LD(12 h12 h),此光周期下孵化率达(88.7±1.8)%,卵黄囊断裂率为(8.7±1.8)%,培育周期为(25.00±0.50) d,孵化周期为(7.00±3.20) d,初孵幼体体质量为(0.209±0.005) g,胴长为(0.998±0.026) cm,出膜7 d后存活率为(96.8±7.1)%.说明弱光照强度30 μmol·m^-2·s^-1和半日光照强度L∶D(12 h∶12 h)更有利于虎斑乌贼的胚胎孵化.在实际生产中,应避免阳光直射,采取适当的遮光措施.     

Induction of a putative metallothionein gene in the blood cockle, Anadara granosa, exposed to cadmium

The relationship between a putative metallothionein gene (MT) and exposure to cadmium (Cd) in blood cockles (Anadara granosa) is reported. In a 96-h dose-response experiment, mortality of cockles was found to proportionately increase in the range of 0.2-5.0 mg/l Cd with a calculated LC(50) of 2.94 mg/l. Exposure to 0.25 mg/l Cd for 16 days caused significant increases (P<0.05) in Cd concentrations in whole tissues, gills and hepatopancreas, and the accumulation of Cd in these tissues increased with the duration of exposure. Two cDNA libraries constructed using the hepatopancreas from control and Cd-treated cockles gave titres of 5.62 x 10(5) and 1.94 x 10(5) pfu/microg vector, respectively. A putative MT gene, AnaMT, of 510 nucleotides in length, was isolated from the treated cDNA library using a heterologous probe MT20 from the blue mussel, Mytilus edulis. Northern analyses using AnaMT as a probe indicated low expression of the MT mRNA in control animals. In cockles treated with 0.25 mg/l Cd for 4 days, MT mRNA level increased to approximately 168%, but declined to 108% at day 8. After 12 and 16 days of Cd treatment, expression of the MT gene was 138% and 187%, respectively, compared to the controls. These observations suggest that induction of the MT gene by a sublethal dose of Cd is rapid, occurring within 4 days of treatment.     

Characteristics of egg and larval production in captive bluespotted gobies

Spawning of the Hawaiian coral-reef goby Asterropteryx semipunctata was diurnal, occurring at various times throughout the day. Mean length of eggs deposited in nests was 0·76 mm (range 0·67–0·84); mean egg width was 0·47 mm (range 0·41–0·52). Clutch size varied from 296 to 1552 eggs (mean=886±309), and was independent of standard length, total body weight, and body condition. Mean relative clutch size was 1·59 eggs mg^-1 total body weight (range 0·84–2·43). Clutches hatched 4–5 nights after being deposited in a nest. Mean notochord length of newly-hatched larvae was 1·88 mm (range 1·60–2·04). The minimum period of time that elapsed between egg deposition and subsequent growth of a new batch of oocytes to spawning size was 5–6 days, providing a reasonable estimate of minimum spawning interval. Compared with other gobiids, tropical species tend to have shorter incubation periods, smaller eggs and smaller larvae at hatching.     

Effect of delayed first feeding on development and feeding ability of Paralabrax maculatofasciatus larvae

The impact of delayed feeding early in development on late feeding ability and development of spotted sand bass Paralabrax maculatofasciatus larvae was examined. Larvae were sampled from hatching until day 19 after delayed feeding for zero (control), 1, 2, or 3 days. Feeding incidence was evaluated as the percentage of larvae with food in the gut and feeding intensity was measured by direct counting of prey after dissection of the gut. Delayed feeding effects due to starvation were observed early in development. By day 5, significant differences ( P  < 0·05) were observed between controls and larvae submitted to degrees of delayed feeding, including total length ( L _T), eye diameter, and the size of the head, liver, gut, muscles and body. Differences were still apparent in L _T, and body, liver and muscle heights at the end of the studied period. Larvae under total starvation did not survive beyond day 5. Initial feeding incidence was 35, 60, 90 and 10% for larvae first fed on day 2, 3, 4 or 5, respectively. Mean ±  s . d . feeding intensity was 3·6 ± 0·8, 2·8 ± 1·3, 5·2 ± 0·3, and 10·2 ± 1·5 rotifers per larva depending on whether larvae were initially fed on day 2, 3, 4 or 5, respectively. The point of no return occurred between 4 and 5 days after hatching.     

Induction of gynogenesis and gonad development in the muskellunge

Muskellunge Esox masquinongy eggs activated with UV-irradiated yellow perch Perca flavescens sperm were subjected to heat shock at 31 ± 1° C for 6 min, 20 min after fertilization in three experiments. Survival at eyed stage was 1·7 ±1·6, 6·8 ± 4·8 and 2·3 ±0·5% in experiments I, II and III, respectively. After rearing the gynogenetic muskellunge in troughs and then in ponds, the sex ratio of gynogens in experiment I did not significantly (P>0·05) differ from the expected ratio 0:1 (male: female), however, one male and one intersex were observed. In experiments II and III, the sex ratio of gynogens differed significantly from expected (0 : 1). Three months after hatching, the growth of females did not significantly (P>0·05) differ among control and gynogenetic groups, whereas male growth was significantly (P<0·01) higher in the control v. gynogenetic group. The histological structures of the gynogenetic fish gonads in both sexes were similar to those described in the gonads of control muskellunge. After the overwintering period, signs of active spermatogenesis were observed in the testis of 1 + year old gynogenetic fish, whereas ovaries contained only oocytes at the perinucleolar stage. At this stage, plasma sex steroids testosterone (T) and oestradiol-17β (E2) cannot be used to discriminate the sex of gynogenetic muskellunge, as intersex, male and female fish had similar levels of T and E2.     

Size at hatching and incubation period of Sympterygia bonapartii (Müller & Henle, 1841) (Chondrichthyes, Rajidae) bred in captivity at the Temaiken Aquarium

Two mature Sympterygia bonapartii held in captivity laid a total of 136 egg cases, 33 of them were incubated at constant temperature (16·5° C), salinity (36) and photoperiod (12L:12D). The hatching rate was 100%. Juvenile fish hatched after 135 ± 10 days (mean ± s . d .) and the mean total length, disc width and mass at hatching were 140 mm, 86 mm and 15·1 g respectively.     

Multiple forms of metallothionein from the digestive gland of naturally occurring and cadmium-exposed mussels, Mytilus galloprovincialis

Polymorphism of metallothioneins in the digestive gland of naturally occurring (control) and experimentally Cd-exposed mussels Mytilus galloprovincialis (200 μg Cd l^–1; 14 days) was studied by applying the conventional methods of Sephadex column liquid chromatography (G-75 and DEAE A-25), and by an electrochemical method (DPASV) for determination of Cd, Zn and Cu concentrations in chromatographic fractions. In both control and Cd-exposed mussels, two distinct molecular mass components of the metallothioneins, monomeric (MT-10) and dimeric (MT-20), were resolved by Sephadex G-75 gel filtration chromatography. In control mussels, the MT-10 component was predominantly expressed as containing markedly higher constitutive levels of Zn (100×) and Cu (10×) than of Cd. Each of these two molecular mass components was further resolved into seven metal-rich peaks by anion-exchange chromatography. In Cd-exposed mussels the larger proportion of Cd was bound to the MT-20 than to the MT-10 component, suggesting that the dimeric component may be considered as a primarily inducible metallothionein. The elution positions of metal-binding maxima of Cd-exposed and control mussels on the respective DEAE chromatographic profiles were comparable. A great similarity in elution positions of Cd maxima between the composite and single-specimen samples was also observed. Our study confirms a high multiplicity of MT forms in mussels from the Mytilus genus not only under the laboratory high-level metal exposure conditions, but also at a natural seawater metal exposure level. The ecotoxicological significance of dimeric and monomeric MT forms, as well as their possible application in the biomonitoring of seawater for trace metals, has been considered. Electronic Publication     

Subcellular changes of essential metal shown by in-air micro-PIXE in oral cadmium-exposed mice

To clarify the relation of essential metals to cadmium (Cd) toxicity, we evaluated metallothionein expression and analyzed the subcellular distribution of essential metals using in-air micro-Particle-Induced X-ray Emission (PIXE). Four mice were dosed orally with 100 mg/L of Cd in drinking water for 1.5 or 2 years. Frozen samples of organs were used for micro-PIXE analysis and formalin-fixed samples were used for metallothionein staining. Immunohistochemically, metallothionein induction by 1.5y-Cd exposure was higher in the renal cortex than in the liver. Metallothionein expression was reduced after 2y-Cd administration compared to the 1.5y-Cd-exposed mice. Cd-induced tissue damage became marked in the 2y-Cd-exposed mice compared to the 1.5y-Cd-exposed mice, in which nephrotoxicity was more prominent than hepatotoxicity. Cd yield was higher in the renal cortex of the 2y-Cd-exposed mouse than in that of the 1.5y-Cd-exposed mouse, whereas no such increasing tendency was found in the liver. Compared to the control, the Cd-exposed mice markedly accumulated zinc in the liver and renal cortex. In the Cd-exposed mice, iron was mildly accumulated in the renal cortex and was slightly deprived in the liver. Elemental maps showed that a large amount of Cd was spatially combined with zinc in the 1.5y-Cd mouse. Free Cd became abundant in the 2y-Cd-exposed mouse. In addition, a small amount of Cd was colocalized with iron. The data suggest that zinc may contribute to protect against oral-administrated Cd toxicity, and impaired induction of MT may participate in hepato-nephrotoxicity of the 2y-Cd-exposed mouse.     

Influence of static and fluctuating salinity on cadmium uptake and metallothionein expression by the dogwhelk Nucella lapillus (L.)

The aim of this study was to investigate the effect of salinity on cadmium (Cd) accumulation and metallothionein (MT) expression in the dogwhelk Nucella lapillus (L.). Adult dogwhelks (shell length: 23.4±1.3 mm) were acclimated to salinity of 33 psu (control), 22 or 11 psu under controlled laboratory conditions (9.5 °C; pH 7.9) for 10 days in a stepwise manner by reducing the salinity by 5.5 psu day⁻¹. Ten treatment groups were used and comprised five salinity regimes (three fixed salinity [33, 22 or 11 psu] and two fluctuating salinity [varied daily between 33 and 22 psu or 33 and 11 psu in a cyclic manner]) at each of two Cd concentrations (control: <0.001 μg Cd l⁻¹ or treatment: 500 μg Cd l⁻¹). After acclimation, groups of 20 dogwhelks were exposed to each of the 10 Cd/salinity combinations. All the control and Cd-exposed dogwhelks exposed to 11 psu were dead within 5 days of exposure due to hypo-osmotic stress. Twenty days after exposure to all other treatments, concentrations of Cd and MTs in the tissues of surviving dogwhelks were quantified using atomic absorption spectrophotometry and the silver saturation method, respectively. Both Cd accumulation and MT induction in control or Cd-exposed N. lapillus were significantly influenced by changes in salinity, especially at a prolonged and fixed low salinity (22 psu), although such influences of salinity on the concentration of MTs were dependent on the tissue type. The study highlights that salinity should be considered when monitoring trace metals and/or MTs in intertidal molluscs, particularly in estuarine or transplanted biomonitors.     

Monitoring populations of the almond seed wasp, Eurytoma amygdali, with sex pheromone traps and other means, and optimal timing of chemical control

During the four years 1986–1989 we monitored an adult male population of the almond seed wasp, Eurytoma amygdali Enderlein, in the region of Thessaloniki, using sex pheromone traps, each containing 25 living virgin females. The emergence of adults from infested almonds of the previous year was also monitored in cages in the field, as well as the progress of fruit infestation and egg hatching in the almonds of the Retsou variety. Finally, two chemical control experiments were done against the newly hatched larvae to determine the optimal time for chemical control.During the 4-year study the start of adult captures occurred between April 13 and April 24, and the maximum between April 17 and May 11. In most cases, adult emergence from infested almonds in field cages began with a delay of 2 to 14 days in relation to the start of trap captures, and was affected by factors such as the date of cage installation. In all years most eggs hatched within 12–18 days of oviposition.A treatment with phosphamidon at a concentration of 0.06%, applied to tree branches of the Retsou variety with a hand-sprayer on May 23, 1987, when 54.1% of the eggs had hatched, was very effective (final infestation in July was 4.7% as compared to 89.1% of the untreated control). Three treatments with phosphamidon 0.06%, applied each on different tree branches, on May 14, 20, and 25, 1988, when the percentage of egg hatching was 7.8%, 65.3%, and 93.5%, respectively, were all very effective (final infestation in July was 1.6%, 3.6%, and 4.2% respectively, as compared to 93.6% of the untreated control). However, the presence of mines in the perisperm and outer endosperm, caused by the feeding larvae before they were killed, was more conspicuous in the almonds treated when the percentage of egg hatching was high.Our data suggest that the almond seed wasp can be effectively controlled with a single treatment of a systemic insecticide against the newly hatched larvae, preferably applied when the percentage of egg hatching is low to medium (between 10% and 50%). In the area of Thessaloniki, during 1986–89, 10% and 50% of egg hatching occurred about 21 and 27 days respectively after the beginning of male adult captures in pheromone traps.     

Larval release behaviors of the striped hermit crab, Clibanarius vittatus (Bosc): Temporal pattern in hatching

Ovigerous hermit crabs, Clibanarius vittatus (Bosc), were examined in the laboratory to (1) determine if the time of larval release is a synchronous event, (2) determine the influence of a damaged gastropod shell during the egg hatching process, and (3) describe larval release behaviors. Ovigerous hermit crabs from natural light:dark (LD) and tidal cycles were moved to constant conditions 2-3 days prior to the predicted time of larval release. Larval release was synchronous, occurring near the time of expected sunset. Females with early-stage embryos placed under constant conditions displayed a free-running circadian rhythm, suggesting that the rhythm is under endogenous control. Hermit crabs with early-stage embryos that were placed under a shifted LD cycle (advanced 12 h relative to the ambient photoperiod) before being placed under constant conditions advanced their larval release rhythm by 12 h, indicating the rhythm can be entrained by the LD cycle. Hermit crabs with an intact shell released larvae in bursts at sunset over several consecutive nights (period = 24.2 h). In contrast, hermit crabs with damaged shells released larvae at different times over the course of a single day. Ovigerous females with intact shells exhibit several stereotypical hatching behaviors. The female stands on her walking legs and thrusts her abdomen, moving the shell in an oscillating motion. This movement may assist in breaking the outer membrane of the egg case. The female generates a water current inside the shell with her scaphognathite and mouthparts, which transports the newly hatched larvae out of the shell. Females in damaged shells did not display these behaviors; instead, larval release was a prolonged event with little movement of the female, and often the newly hatched larvae were not viable. These results indicate that an intact shell plays an important role in the hatching process for this hermit crab.     

Prey selection and functional morphology through ontogeny of Amphiprion clarkii with a congeneric comparison

The relationship between the complexity of the feeding apparatus and prey selection through ontogeny was examined in Amphiprion clarkii larvae. Larvae were reared from 1 to 10 days post-hatch (dph) on a diet of rotifers, wild-caught plankton and newly hatched Artemia sp. nauplii. Results were compared with available data on the relationship between functional morphology and prey selection of Amphiprion frenatus to establish patterns of functional morphology and prey selection between the larvae of two species of coral-reef fishes. Larvae of both species exhibited an increase in selection of larger prey through ontogeny coincident with an increase in the complexity of the feeding apparatus. The first elements to ossify in larvae of both species were the pharyngeal teeth ( A. clarkii : 5 dph, near ± s.d. Standard length, L _S,4· 3 ± 0· 2 mm; A. frenatus : 5 dph, L _S5· 0 ± 0· 4 mm) which, in combination with the development of a more functional feeding apparatus, may have permitted larvae to better process new types and sizes of prey. Prey items, however, were selected differentially between the two fish species, which could not be fully explained by the functional state of the feeding apparatus. While prey selection is influenced by the functional state of the feeding apparatus, all aspects of larval fish biology (morphology, behaviour and physiology) should be considered.     

Survival and sublethal responses of early life stages of pike exposed to low pH in artificial post-mining lake water

The threshold pH for survival of early life stages of pike Esox lucius in post-mining lakes was determined in a laboratory experiment using artificial water characterized by high concentrations of dissolved Ca, Al, Fe, Mn and SO2/4⁻. At pH 3·50–4·00, high mortality was observed before hatching. At pH 4·00 and 4·25, hatching rates were reduced compared with the controls (pH 7·40), and many embryos died in a partly hatched state. Hatching success of embryos exposed to pH levels of 4·50 or higher was not affected. However, at pH 5·00 many newly hatched embryos were deformed. Furthermore, pike exposed to pH 4·00–5·00 did not start feeding. At pH 4·75 and below, mortality increased to 100%, and at pH 5·00, only few eleutheroembryos which were in extremely poor condition survived to the end of the experiment. At pH 5·50, survival was in the same range as in the control group, but growth was reduced. Therefore, early life stages of pike are expected to survive in Lustian post-mining lakes when a pH of 5·50 and above is reached and maintained.     

Effects of temperature on developmental performance, survival and growth of sea lamprey embryos

This study assesses the influence of thermal regime on the development, survival rates and early growth of embryos of sea lamprey Petromyzon marinus incubated at five constant temperatures (7, 11, 15, 19 and 23° C). The time from fertilization to 50% hatching and from hatching to 50% burrowing were inversely related to incubation temperature. All the embryos incubated at 7° C died at very early stages, while those maintained at 11° C did not attain the burrowing stage. Survival from fertilization to hatching was 61, 89, 91 and 89% at 11, 15, 19 and 23° C, decreasing to 58, 70 and 70% from hatching to burrowing at 15, 19 and 23° C, respectively. Larvae reared during the first 3 months of exogenous feeding in a common environment at constant 21° C, revealed maximum survival for an incubation temperature of 15° C (43% of burrowed larvae) decreasing strongly at 19° C (16%) and 23° C (one suvivor among 240 larvae). Body length at the burrowing stage was maximum for embryos incubated at 19° C, but body mass increased in the interval 15–23° C. Mean incubation temperatures experienced by 117 broods during the embryonic development in the source river were estimated in 15·3±2·30° C and 16·7±1·76° C (mean±1 s.d .) for the periods fertilization-to-hatching and hatching-to burrowing, respectively.     

Cadmium effects on development and reproduction of Oncopeltus fasciatus (Heteroptera: Lygaeidae)

Newly hatched nymphs of the insect Oncopeltus fasciatus were exposed to various concentrations of CdCl2 administered in drinking water until the end of adult life. Significant nymphal mortalities were observed at concentrations above 30 mg Cd/l (corresponding to the LC50). The duration of the nymphal stages increased in proportion to the Cd concentration; at the lowest Cd concentration of 10 mg Cd/l, the median duration was significantly prolonged by one day, while at the highest concentration of 100 mg Cd/l it was increased by 10 days over the control group. The weight of newly emerged adults lineally decreased with Cd concentration, being reduced to half the weight of controls at 100 mg Cd/l. In addition, a proportionality between delay in development and weight reduction was found in Cd-treated adults. Survival of adult females was decreased at concentrations higher than 10 mg Cd/l, while males were only affected at 30 mg Cd/l or higher doses. Reproduction was the most affected parameter. Oviposition rate, fecundity and fertility of females exposed to 10 mg Cd/l were significantly lower than controls (73%, 58% and 55% relative to controls, respectively). Hatchability of the eggs laid by treated females was also reduced. These results show that development and reproduction of O. fasciatus are seriously impaired at sublethal Cd concentrations.     

Influence of water temperature and waterborne cadmium toxicity on growth performance and metallothionein–cadmium distribution in different organs of Nile tilapia,Oreochromis niloticus (L.)

Cadmium (Cd) is believed to be one of the most abundant and ubiquitously distributed toxins in the aquatic system. This metal is released to the aquatic environment from both anthropogenic sources, such as industrial, agricultural and urban effluents as well as natural sources, such as rocks and soils. Otherwise, the temperature increase of water bodies, which has been observed due to global climatic changes, has been shown to increase Cd toxicity for several aquatic animal species including fish. In the present study, Nile tilapia, Oreochromis niloticus (L.), (26.0±0.38 g) were reared at 20, 24, 28, or 32 °C and exposed to 0.0 or 0.5 mg Cd/L for 8 weeks to investigate effects of water temperature, Cd toxicity and their interaction on fish performance as well as metallothionein (MT) and Cd distribution in different fish organs. It was found that fish reared in Cd-free group at 28 °C showed the optimum growth and feed intake, while Cd-exposed fish showed low growth and feed intake irrespective to water temperature. A synergetic relationship between water temperature and Cd toxicity was observed where Cd toxicity increased as water temperature increased and the worse growth was obtained in Cd-exposed fish reared at 32 °C. Additionally, the highest Cd residues in different fish organs were detected in Cd-exposed fish reared at 32 °C. Similarly, MT concentrations in different fish organs increased as water temperature increased especially in Cd-exposed fish groups. A high positive correlation between MT and Cd concentrations in fish organs was detected. The distribution of MT and Cd levels was in the order of liver>kidney>gills>muscles. The present study revealed that the optimum water temperature suitable for Nile tilapia growth is 28 °C. Additionally, Cd exposure had a deteriorate effect on the growth and health of Nile tilapia. This hazardous effect increased as water temperature increased. Further, liver and kidney were the prime sites of Cd accumulation, while Cd load in the muscles was the lowest as compared to the other investigated organs.