Effects of dieldrin-contaminated food on the development of Leptodius floridanus larvae

Leptodius floridanus (Rathbun) (Decapoda: Xanthidae) larvae were fed dieldrin-contaminated Artemia nauplii throughout their development to megalopa. Sublethal effects were noted at dieldrin concentrations as low as 5.49 ppm, and no larvae completed their development when fed Artemia containing 33.0 ppm dieldrin. Organochloride pesticide residues were measured in zooplankton collected from Onslow Bay, North Carolina, USA. These residue levels were found to be much lower than those found to affect Leptodius larvae in the laboratory.     

Effect of Pb,Cd and Cu on survival and development of Culex quinquefasciatus (Diptera: Culicidae)

ABSTRACT

The present research aimed to determine the lowest levels of three heavy metals (Pb, Cd and Cu) to which the larvae of Southern House Mosquito, Culex quinquefasciatus are susceptible in water. The study also aimed to investigate the effects of these heavy metals on the development of Cx. quinquefasciatus at concentrations set by Pakistan Environmental Protection Agency (Pak-EPA) as permissible levels for liquid industrial effluents. The 2nd instar larvae of Cx. quinquefasciatus were exposed to different concentrations of Pb, Cd and Cu and their effects on oviposition preference, egg hatching rate and larval development were studied. The LC₅₀ values of Pb, Cd and Cu were 12.6, 6.3 and 2.6?ppm, respectively. Gravid female mosquito adults deposited a significantly lower number of egg rafts in containers containing 0.50?ppm Pb or 1.0?ppm Cu in water. Each of the heavy metals in water resulted in significantly (p?<?0.05) lower egg hatching rate, prolonged time to pupation, lower pupation rate, prolonged time to adult emergence, lower adult emergence rate and higher female to male ratio. It is concluded that the 2nd instar larvae of Cx. quinquefasciatus are susceptible to Pak-EPA permissible levels of Pb, Cd and Cu in municipal and liquid industrial effluents.     

In vitro and in vivo inhibition of Ca2+-Mg2+-ATPase activity by cadmium in post larvae of Penaeus monodon

Ca²⁺-Mg²⁺-ATPase is a membrane-bound enzyme and is responsible for regulating cytosolic free calcium. In vitro and in vivo effects of cadmium were studied on Ca²⁺-Mg²⁺-ATPase activity in plasma membrane/mitochondrial fraction of Penaeus monodon post larvae. In vitro studies revealed a concentration-dependent decrease in enzyme activity with an IC₅₀ value of 11.02?µM. In vivo experiments were conducted by exposing the post larvae to 1/10th (0.12?ppm) and 1/5th (0.24?ppm) of LC₅₀ values of cadmium for 30 days. Both ATPase activity and metal accumulation were estimated in post larvae exposed to 0.12 and 0.24?ppm of cadmium at different intervals of 24?h, 48?h, 96?h, 10 days and 30 days. ATPase activity showed a gradual decrease in post larvae on exposure to both the sub-lethal concentrations with respect to their controls and the decrease was significant (p?相似文献   

Effects of oil on behavioral responses to light,pressure and gravity in larvae of the rock crab Cancer irroratus

Cancer irroratus Say larvae (Zoeal Stages I–V and megalopae) were cultured and studied in 0.0, 0.1, and 1.0 ppm concentrations of water-accommodated fractions of No. 2 fuel oil under static conditions. Behavioral changes were monitored in terms of water column responses to various conditions of light, pressure and gravity. Results showed significant (F=206.12, P<0.01) effects of this oil fraction on larval behavior, with the specific response to oil depending upon the concentration, larval stage and the combination of light, pressure and gravity tested. Responses at 0.1 ppm differed from those at 1.0 ppm (F=5.01, P<0.05). Geonegative upward movements in the water column were typically depressed in early-stage larvae and enhanced in late-stage larvae after subjection to oils, showing gravity responses to be greatly affected. Phototactic behaviors were significantly changed by the oil and pressure responses were slightly affected.     

Effects of the juvenile hormone mimic ZR-515 (Altosid®) on larval development of the mud-crab Rhithropanopeus harrisii in various salinities and cyclic temperatures

Effects of 0.01, 0.1 and 1.0 ppm methoprene (Altosid^®: ZR-515), a juvenile hormone (JH) mimic which shows high activity against some economically important insect pests, especially Diptera, were tested on larvae of the mud-crab Rhithropanopeus harrisii (Gould) (Brachyura: Xanthidae) from hatching to the first crab stage under optimum and stress conditions of a number of salinities and cyclic temperatures. There was a significant reduction in survival of zoeal larvae with increasing concentrations of methoprene in nearly all combinations of salinity and temperature. On the average there was 9% less survival in the 0.01 ppm concentration of methoprene than in the control, and in the 0.1 ppm concentration the survival was further reduced by another 16%. At 1.0 ppm methoprene no larvae survived beyond the first zoeal stage under optimum conditions or under stressful combinations of salinity and temperature. Except at 0.2 ppm in 27.5% S, survival of the megalopa was not significantly reduced in 0.01 or 0.1 ppm methoprene in any salinity or temperature, although the percentage of abnormal megalopa increased under stress conditions. The first zoeal stage was the most sensitive of the larval stages to methoprene as well as to salinity and temperature stress. The duration of zoeal development was significantly lengthened with an increase in concentration of methoprene under nearly all conditions of salinity and temperature. The JH mimic had, however, no significant effect on the duration of megalopa development. A significant synergism between methoprene, salinity and temperature was not observed. It can be concluded from the results that methoprene does not inhibit metamophosis of R. harrisii larvae at the 0.1 ppm level or lower. Reduction in survival of zoeal stages and increased duration of zoeal development with increasing concentrations of methoprene are presumably related to stress.     

Individual effects and interactions of salinity,temperature, and zinc on larval development of the grass shrimp Palaemonetes pugio. I. Survival and developmental duration through metamorphosis

Larvae of the estuarine grass shrimp Palaemonetes pugio (Holthuis) were reared from hatch through successful completion of metamorphosis in 80 combinations of salinity (3 to 31%), temperature (20° to 35°C), and zinc (0.00 to 1.00 ppm Zn⁺⁺). Response-surface methodology was employed to depict the individual effects and interactions of the three factors on survival and developmental duration through total larval development. Outside the optimal salinity-temperature conditions of 17 to 27 S and 20° to 27°C, viability of larvae was reduced by both the individual effects of salinity and temperature and interactions between the two factors. Survival capacity of larvae and resistance adaptations to salinity and temperature were progresively reduced by zinc concentrations from 0.25 to 1.00 ppm Zn⁺⁺. Response-surface analysis of the data suggested that the duration of total larval development of P. pugio was least at salinities from 18 to 23 and at temperatures from 30° to 32°C. At both higher and lower salinity-temperature conditions and in increasing zinc concentrations from 0.25 to 1.00 ppm Zn⁺⁺, developmental rates were retarded. A significant zinc-temperature interaction existed, whereby increasing zinc concentrations reduced both survival and developmental rates of larvae more at suboptimal temperatures. Larval resistance to zinc toxicity was least at supraoptimal salinities, indicative of a significant zinc-salinity interaction. The reduced viability, restricted euryplasticity, and retarded developmental rates of P. pugio larvae developing in media with low-level zinc contamination would limit the distributive properties of the pelagic phase in the life cycle of the species and reduce recruitment both into and out of the parent estuarine population.     

Acclimation and tolerance of Artemia salina to copper salts

The brine shrimp Artemia salina L. was acclimated in sea water with cupric chloride, acetate, carbonate, and sulphate, each at concentrations of 0.1, 0.05 and 0.025 ppm Cu⁺⁺, together with sea water controls. Growth inhibition was observed in all four compounds, generally in direct relationship to the concentration. It was least in sulphate, and increased progressively in chloride, acetate and carbonate in that order. No inhibition however was observed in carbonate at 0.025 ppm Cu⁺⁺. In toxicity tests, 2-week old larvae from each solution were exposed to concentrations of 10, 7.5, 5, 2.5 and 1 ppm Cu⁺⁺ of the same compounds, together with unacclimated larvae of the same age. Similar tests were held with 6-week old adults acclimated (a) in 0.1 ppm Cu⁺⁺ (chloride, acetate and sulphate) using the same concentrations and (b) in 0.5 ppm Cu⁺⁺ (carbonate), using 150, 125, 100, 75, and 50 ppm Cu⁺⁺. Toxicity to unacclimated larvae and adults differed with the compounds, carbonate being the least toxic, followed by sulphate, chloride and acetate in increasing order. Larvae acclimated in chloride (0.025 ppm Cu⁺⁺) and sulphate (0.1 and 0.5 ppm Cu⁺⁺) showed an increased tolerance to 1 and 2.5 ppm Cu⁺⁺ compared to untreated controls. Tolerance was not enhanced from 5 ppm Cu⁺⁺ upwards. In both compounds, adults acclimated in 0.1 ppm Cu⁺⁺ showed an increased tolerance to concentrations between 1 and 7.5 ppm Cu⁺⁺ compared to controls. Larval mortality in carbonate was below 50% in all test solutions. Adults acclimated at 0.5 ppm Cu⁺⁺ showed an increased tolerance to 50 ppm Cu⁺⁺ compared to controls. Considerable precipitation occurred with the high levels of this compound, thus effecting the final concentrations. No acclimation effect was observed in acetate for either larvae or adults. It is suggested that in A. salina, copper toxicity depends on the particular form of the metal, and that this difference is also evident in growth inhibition and in the potential acquisition of increased tolerance through exposure to low concentrations.     

A long-term study of the effects of water-soluble fractions of No. 2 fuel oil on the survival,development rate,and growth of the mud crab Rhithropanopeus harrisii

Mud crabs, Rhithropanopeus harrisii (Gould), were exposed continuously for 6 months after hatching to water-soluble fractions (WSF) of No. 2 fuel oil. Survival, growth and development rate were monitored during this time. The zoeal stages were the most sensitive to fuel oil. A 20% WSF (0.36 ppm total naphthalenes, 1.26 ppm total hydrocarbons) was acutely toxic to these stages. Of the zoeal stages, the first stage appeared to be the most sensitive. The combined duration of the 4 zoeal stages was significantly increased by increasing WSF exposure concentrations. The megalopa and crab stages were not particularly sensitive to continued petroleum hydrocarbon exposure, particularly when compared to zoeal stages. However, mean duration of the megalopa and first crab stages was significantly affected by oil exposure. Individuals which survived the highest exposure concentrations as larvae appeared to grow larger during the crab stages, so that at the end of 6 months comparably staged crabs were equal to or larger than both control crabs and those exposed to low WSF concentrations. Stage distributions at the end of 6 months showed no differences due to WSF exposure. Sex ratios, which could be determined at the end of 6 months, were approximately 1, indicating no sex-related differential sensitivity to WSF exposure, at least as larvae or juveniles. The data indicate that these crabs possess considerable ability to recover from the effects of chronic sublethal exposure to petroleum hydrocarbons. The most deleterious effects of oil pollution on this species may be due to its impact on larval recruitment into the adult population.     

Acclimation and tolerance of Artemia salina and Ophryotrocha labronica to cooper sulphate

The brine shrimp Artemia salina L. and the polychaete worm Ophryotrocha labronica La Greca and Bacci were acclimated in sea water with copper sulphate at concentrations of 0.1, 0.05, and 0.025 ppm Cu⁺⁺, for 3 and 2 generations, respectively. Both adults and larvae of A. salina showed a greater tolerance to 1 ppm Cu⁺⁺ after acclimation compared to controls of the same age, although this tolerance diminished in successive generations. The acclimation effect was less marked in O. labronica. In both species, tolerance to 10 ppm Cu⁺⁺ upwards was not enhanced. Growth-rate inhibition and an adverse effect on reproduction was observed, in some instances in direct relationship to the acclimation concentration. It is suggested that, in A. salina, a certain tolerance to copper may be acquired through exposure to low concentrations.     

Effects of zinc on epidermal ultrastructure in the larva of Clupea harengus

In March, 1983 changes in epidermal ultrastructure were examined in Clupea harengus L. larvae hatched from eggs incubated in four zinc concentrations (0.5 2.0, 6.0 and 12.0 ppm). In addition to the outer and inner epidermal cell types described previously, a third type of cell is present. Ultrastructurally this resembles the epidermal chloride cells of Sardinops caerulea Girard, characterised by numerous mitochondria, extensive smooth endoplasmic reticulum and a free surface exposed to the environment. These cells occur on the yolk sac, head and in the regions of the trunk just above the yolk sac. In larvae treated in 12.0 ppm zinc, the cells contain fewer mitochondria with fewer cristae than those in the controls. Smooth endoplasmic reticulum is much reduced forming nodular masses and contains granular osmiophilic inclusions. In larvae hatching from eggs previously incubated in 6.0 and 12.0 ppm zinc, the epidermal cells contain more vesicles, intracellular spaces, and swollen mitochondria and show signs of necrosis. The viability of these larvae is discussed.     

Biological effects of oil on early development of the Baltic herring Clupea harengus membras

The effects of petroleum hydrocarbons from two crude oils and one fuel oil (No. 1) were studied on the ontogenic development of the Baltic herring Clupea harengus membras L. Herring eggs exposed to water-soluble fractions of the oils at the time of fertilization showed no decrease in numbers of fertilized eggs compared to eggs exposed 6 or 72 h after fertilization. During embryongenesis, treatment with 3.1 to 8.9 ppm or 3.3 to 11.9 ppm total oil hydrocarbons from light fuel oil and the two crude oils respectively, gave rise to alterations in embryonic activity, decreased heart rate, and premature or delayed hatching. Although many larvae hatched from eggs exposed to contaminated water (3.1 to 11.9 ppm total oil hydrocarbons), the majority of the (70 to 100%) were malformed or dead 1 day after hatching. Exposure of eggs to 5.4–5.8 ppm total oil hydrocarbons resulted in significantly (P<0.001) decreased lengths of the larvae. Increased temperature (from 9° to 14°C) aggravated the effects of the oils. The results are discussed in relation to the potential effects of oil spills and chronic oil pollution on fish eggs and larvae in the Baltic Sea.     

Long-term effects of water-soluble fractions of Kuwait crude oil on the larval and juvenile development of the mud crab Eurypanopeus depressus

Larvae of the mud crab Eurypanopeus depressus (Smith) were reared in various concentrations of the water-soluble fraction of Kuwait crude oil. The 48-h TL_m (median tolerance limit) for Zoea Stage I was approximately 10 ppm total dissolved hydrocarbons and that for Zoea Stage II approximately 17 ppm. Chronic toxicity of more dilute solutions (4.3 and 8.7 ppm) was assessed independently for each larval stage and for subsequent developmental stages through Crab Stage 5. In the group continuously exposed to oil from hatching, there was differential mortality relative to controls in every larval stage and increased duration of intermolt periods was observed at every stage through Crab Stage 5. Mortality in groups not exposed until larvae had reached Zoea Stages III or IV was not greater than controls, suggesting that toxicity to advanced larval stages may be related to accumulation of toxic compounds by the larvae. Neither concentration (4.3 or 8.7 ppm) of crude oil caused increased mortality among juvenile crab stages regardless of the time of initial exposure. Increased occurrence of an extra and morphologically abnormal megalopa stage was associated with exposure to the crude oil. This has not been reported before.Communicated by I. Morris, West Boothbay Harbor     

Effects of the juvenile hormone mimic ZR-512 (Altozar®) on larval development of the mud-crab Rhithropanopeus harrisii at various cyclic temperatures

Effects of the juvenile hormone (JH) mimic hydroprene (Altozar^®: ZR-512), which exhibits high activity against Lepidoptera, were studied on the larval development of the mud-crab Rhithropanopeus harrisii (Gould) (Brachyura: Xanthidae). Larvae reared in 20 S at 3 cycles of temperature of 20° to 25°C, 25° to 30°C and 30° to 35°C, were exposed to 0.01, 0.1 and 0.5 ppm hydroprene from hatching to the first crab stage. Larvae were also exposed to 0.1 and 0.5 ppm hydroprene only from the megalopa stage to the first crab stage. When larvae were treated with hydroprene throughout larval life, survival was significantly reduced with increasing concentrations of the compound at all temperature cycles. Synergistic effect between hydroprene and temperature on survival of zoeal larvae was not observed. On the average there was 11% less survival in the zoeal stages at the 0.01 ppm concentration. of hydroprene than in the control, an additional reduction of 13% occurred at 0.1 ppm, and finally there was a further decrease of 46% at 0.5 ppm hydroprene. Significant decrease in survival in the megalopa stage occurred only in the 0.5 ppm concentration of hydroprene at the lowest temperature cycle when larvae were exposed to the compound from hatching. When larvae were treated with hydroprene only within the megalopa stage, a significant reduction in survival was not observed. First-stage zoeae were the most sensitive of the larval stages to hydroprene. Duration of zoeal development was significantly delayed at 0.5 ppm hydroprene at the two lower temperature cycles, whereas in the megalopa stage the delay began at the 0.1 ppm level at all 3 temperature cycles when larvae were exposed to hydroprene from hatching. A significant delay was also observed at 0.1 ppm hydroprene at the two lower cycles when larvae were exposed to hydroprene only in the megalopa stage; at 30° to 35°C a significant delay was observed only at the 0.5 ppm level. The results show that metamorphosis to the first crab stage was not inhibited at the 0.5 ppm level of hydroprene or lower. Reduction in survival and increase in duration of larval development were presumably related to stress conditions caused by hydroprene. The results also suggest an interaction between temperature and hydroprene on survival of megalopa larvae and duration of larval development.     

Accumulation and release of fuel-oil-derived diaromatic hydrocarbons by the polychaete Neanthes arenaceodentata

Male and gravid female Neanthes arenaceodentata (Moore) (Polychaeta: Annelida) were experimentally exposed to a sublethal concentration of No. 2 fuel oil seawater extract for 24 h. Within 1 h both sexes had incorporated, in equal proportions, most of the diaromatic hydrocarbons (naphthalene, methylnaphthalenes) eventually accumulated. No net loss of accumulated naphthalenes was observed during the exposure period. When returned to hydrocarbon-free seawater, male worms slowly released naphthalenes down to undetectable (< 0.1 ppm) levels in 400 h (17 days). Gravid females retained essentially all of the originally accumulated naphthalenes for 3 weeks, at which time they released their eggs during fertilization, with subsequent dramatic decreases in naphthalenes content. Zygotes and trochophore larvae from exposed females contained 18 ppm naphthalenes, accounting for a majority of those amounts initially present in parent females. As trochophore larvae developed into 18-segment juveniles, naphthalenes concentrations dropped to near undetectable levels (0.4 ppm) in 21-day old juveniles (= 18-segment worms). When sampled at the next stage of development (32-segment worms) 5 days later (1050 h after exposure of gravid females), offspring were free of naphthalenes. Results suggest the importance of lipid-rich eggs in the accumulation and retention of diaromatic hydrocarbons by marine polychaetes.     

Impacts of temperature and acidification on larval calcium incorporation of the spider crab <Emphasis Type="Italic">Hyas araneus</Emphasis> from different latitudes (54° vs. 79°N)

The combined effects of ocean warming and acidification were compared in larvae from two populations of the cold-eurythermal spider crab Hyas araneus, from one of its southernmost populations (around Helgoland, southern North Sea, 54°N, habitat temperature 3–18°C; collection: January 2008, hatch: January–February 2008) and from one of its northernmost populations (Svalbard, North Atlantic, 79°N, habitat temperature 0–6°C; collection: July 2008, hatch: February–April 2009). Larvae were exposed to temperatures of 3, 9 and 15°C combined with present-day normocapnic (380 ppm CO₂) and projected future CO₂ concentrations (710 and 3,000 ppm CO₂). Calcium content of whole larvae was measured in freshly hatched Zoea I and after 3, 7 and 14 days during the Megalopa stage. Significant differences between Helgoland and Svalbard Megalopae were observed at all investigated temperatures and CO₂ conditions. Under 380 ppm CO₂, the calcium content increased with rising temperature and age of the larvae. At 3 and 9°C, Helgoland Megalopae accumulated more calcium than Svalbard Megalopae. Elevated CO₂ levels, especially 3,000 ppm, caused a reduction in larval calcium contents at 3 and 9°C in both populations. This effect set in early, at 710 ppm CO₂ only in Svalbard Megalopae at 9°C. Furthermore, at 3 and 9°C Megalopae from Helgoland replenished their calcium content to normocapnic levels and more rapidly than Svalbard Megalopae. However, Svalbard Megalopae displayed higher calcium contents under 3,000 ppm CO₂ at 15°C. The findings of a lower capacity for calcium incorporation in crab larvae living at the cold end of their distribution range suggests that they might be more sensitive to ocean acidification than those in temperate regions.     

Seaweed secondary metabolites as antifoulants: effects of Dictyota spp. diterpenes on survivorship, settlement, and development of marine invertebrate larvae

Summary. A recent investigation showed that the brown seaweed Dictyota menstrualis was unfouled relative to co-occurring seaweeds, and that larvae of fouling invertebrates avoided settling on D. menstrualis due to chemicals on its surface. The secondary metabolites dictyol E and pachydictyol A are among the compounds found on this alga's surface. In the present study, we tested the effects of specific diterpenes from Dictyota on the survivorship, growth, and development of invertebrate larvae and developing juveniles that could foul seaweeds. Exposure to dictyol E, dictyol B acetate, pachydictyol A, and dictyodial from Dictyota menstrualis and D. ciliolata caused significant larval mortality, abnormal development, and reduce growth rates for three species of co-occurring invertebrates when their larvae were forced into contact with these metabolites. Larvae were damaged at metabolite concentrations as low as 5% of maximum possible surface concentrations of these compounds for the populations of Dictyota we studied. The negative effects of these secondary metabolites on potential foulers, in conjunction with data demonstrating larval avoidance of dictyol-covered surfaces, suggest that these compounds could function as chemical defenses against fouling, and could select for larvae that avoid hosts producing these metabolites. Received 25 May 1998; accepted 22 June 1998.     

Effects of fertilization and elevated CO<Subscript>2</Subscript> on larval food and butterfly nectar amino acid preference in<Emphasis Type="Italic"> Coenonympha pamphilus</Emphasis> L.

The effects of larval diet on the nutritional preferences of butterflies has rarely been examined. This study investigates whether alterations in the larval diet result in changes in adult preferences for nectar amino acids. Larvae of Coenonympha pamphilus were raised on fertilized or unfertilized Festuca rubra, grown under ambient (350 ppm) or elevated (750 ppm) atmospheric CO ₂environments. Fertilization led to marked increases in leaf nitrogen concentration. In plants grown under elevated CO ₂conditions, leaf water and nitrogen concentrations were significantly lower, and the C/N-ratio increased significantly. Fertilization of the host plant shortened the development time of C. pamphilus larvae, and pupal weight increased. In contrast, larvae of C. pamphilus developed significantly slower on F. rubra grown under elevated CO ₂, but adult emergence weight was not affected by CO ₂treatment of the plant. C. pamphilus females showed a clear preference for nectar mimics containing amino acids, whereas males, regardless of treatment, either preferred the nectar mimic void of amino acids or showed no preference for the different solutions. Female butterflies raised on fertilized plants showed a significant decline in their preference for nectar mimics containing amino acids. A slight, but not significant, trend towards increased nectar amino acid preference was found in females raised on plants grown under elevated CO ₂. We clearly demonstrate that alterations in larval host quality led to changes in butterfly nectar preferences. The ability of the butterfly to either rely less on nectar uptake or compensate for poor larval conditions represents a trade-off between larval and adult butterfly feeding.     

Effects of nano carbon black and single-layer graphene oxide on settlement,survival and swimming behaviour of Amphibalanus amphitrite larvae

The effects of two carbon-based nanomaterials, nano-sized carbon black (nCB), and single-layer graphene oxide (GO) on settlement of Amphibalanus amphitrite (Cirripedia, Crustacea) cypris larvae (cyprids) were assessed after 24, 48, and 72 h of exposure. Additionally, the effects of these nanomaterials on the mortality and swimming behaviour of the nauplius larvae (nauplii) of the same organism were determined after 24 and 48 h. The data indicate that nCB is more effective as a potential antisettlement agent than single-layer GO; moreover, nCB did not show any adverse effects on the larvae. The swimming behaviour of II stage nauplii of A. amphitrite exposed to a suspension of nCB was inhibited only at very high nCB concentrations (≥0.5 mg/mL). Single-layer GO, on the contrary, showed lower antisettlement effects and was more active in altering the survival and inhibiting the swimming behaviour of the nauplii. An indication of the toxic or non-toxic mechanisms of the antisettlement properties of both of these nanomaterials is provided by the reversibility of the antisettlement activity. In conclusion, we propose nCB as an innovative antifouling nanomaterial that shows low toxicity towards the model organism (crustaceans) used in this study.     

Effects of suspended sediments on egg production of the calanoid copepod Acartia tonsa

The estuarine copepod Acartia tonsa was collected on several occasions between 4 April and 14 August 1985 from Terrebonne Bay, Louisiana (29°08N; 90°36W) and the effects in its diet of suspended sediments, collected from the same area, were measured at five different concentrations of sediment (100 to 1 000 ppm) and six phytoplankton concentrations (500 to 13 000 cells ml^-1 Thalassiosira weissflogii). Egg production rate was used as an index of diet quality. At low phytoplankton concentrations (500 cells ml^-1), and at intermediate phytoplankton concentrations (2 000 cells ml^-1) for previously starved copepods, egg production was reduced by up to 40% at a sediment concentration of 250 ppm and further reduced at higher sediment concentrations. At higher food concentrations (4 000 to 13 000 cells ml^-1), suspended sediment had no effect on egg production rates at sediment concentrations up to 500 ppm. Rates were reduced only at the highest sediment concentration of 1 000 ppm. Under most natural conditions, suspended sediment would not significantly affect egg production rates in A. tonsa.     

Toxicological and larvicidal activities of Alzanzalakhet,Melia azedarach against cucurbit fly,Dacus ciliatus at Hail Province in Saudi Arabia

Alzanzalakhet, Melia azedarach L. (Sapindales: Meliaceae) is a common medicinal plant which is found in Hail desert in Saudi Arabia and traditionally used for various purposes. In this study, toxin effectiveness of the ethanolic, acetonic, and aqueous extracts of M. azedarach leaves was tested to determine a larvicidal activity against the cucurbit fly, Dacus ciliatus (Loew) (Diptera: Tephritidae). Different treatments with M. azedarach extracts varied significantly in their impact on mortality of D. ciliatus larvae. Results showed that all tested extracts in the three solvents exerted a positive pattern for reducing larvae of D. ciliatus. However, the ethanolic M. azedarach extract was the most potent compared with other tested solvents. The highest mortality of the D. ciliatus larvae was shown to be 94%, 74%, and 68% when the concentration was 1?×?10⁵?ppm for ethanolic, acetonic, and aqueous extracts, respectively. In contrast, the concentration 1?×?10¹?ppm resulted in the lowest mortality of D. ciliatus larvae at 40%, 34%, and 12% for ethanolic, acetonic, and aqueous extracts, respectively. Overall, the results of this study suggest that the ethanolic extract of M. azedarach leaves may be used as a sustainable method for controlling D. ciliatus larvae.