Gnathia maxillaris infestation in exhibition aquaria: control and treatment strategies

An outbreak of gnathiids in a captive fish population in a large exhibition aquarium is described, including a method for enumeration of the causative agent. This procedure for harvesting and counting the parasites was based on the positive phototropism of their larvae (zuphea and praniza). Water pumps with spotlights allowed capture of larva using a 200‐micron plankton net. Harvested samples were rinsed with fresh water in the laboratory to immobilise the zuphea and praniza and thus facilitate the enumeration process by direct observation under a stereoscopic glass. The sampling method was found to be representative of the degree of infestation experienced by the entire aquarium system; this finding is very important as it allows the enumeration of different life‐cycle stages (zuphea, praniza and adults). The outbreak was studied and the infestation monitored over a period of many years. Several substrates were assayed for the capture of gnathiid males, with identification of the causative parasite by such morphological characteristics as Gnathia maxillaris. Physical and chemical treatments were applied to mitigate the infestation. Selected to control the infestation and its lifetime in closed marine‐water systems, the Trichlorfon was evaluated by chromatography.     

Further Studies on Haemogregarina bigemina Laveran & Mesnil,the Marine Fish Blennius pholis L., and the Isopod Gnathia maxillaris Montagu1

Haemogregarina bigemina is redescribed from the blood of the marine fish Blennius pholis, and stages presumed to be those of the haemogregarine are recorded from the hematophagous praniza larva of the isopod Gnathia maxillaris. At College Rocks, Aberystwyth, Wales, the main study area, a high incidence of infection occurred in B. pholis. No exoerythrocytic stages were observed in these fish, nor was sexual dimorphism of the gametocyte evident. As in an earlier study, ecological evidence favored transmission by G. maxillaris rather than by leeches. Gametocytes, syzygy, oocysts, sporoblasts, and sporozoites were identified in the anterior hindgut of the isopod. The stages observed in G. maxillaris are compared with those of other haemogregarines described from the digestive tract of leeches. Mention is made of an intraleucocytic haemogregarine of another fish, Crenilabrus melops.     

Effects of varying levels of dietary vitamin E (α‐tocopherol) on growth performance,proximate and fatty acid composition of juvenile silver pomfret (Pampus argenteus Euphrasen, 1788)

This study investigated the effects of elevated dietary levels of vitamin E (α‐tocopherol) on growth performance, proximate composition and fatty acid profiles of juvenile silver pomfret, Pampus argenteus. Three semi‐purified experimental diets were formulated to contain 49% protein and 16% lipid. High docosahexaenoic acid (DHA) tuna oil was added to the diets to supplement DHA. A graded level of vitamin E (0‐, 50‐, and 100 mg kg^?1) was added to experimental diets 1 to 3, respectively. Analyzed vit. E levels were 155.2, 195.3 and 236.4 mg kg^?1 in diets 1, 2 and 3, respectively. The experiment was conducted for 12 weeks with juvenile silver pomfret (29.6 ± 7.6 g) using a flow‐through system consisting of nine 1‐m³ tanks. Each treatment had three replicates and fish were stocked at the rate of 20 m^?3. Growth performance and feed utilization parameters of fish fed diets 2 and 3 were significantly (P < 0.05) higher than in fish fed diet 1, but the parameters in diets 2 and 3 did not differ significantly (P > 0.05). Although whole body protein levels were not influenced by the dietary vit. E levels, whole body lipid in fish fed diet 2 was significantly higher than in fish fed the other diets. The whole body vit. E levels in fish fed diet 2 (22.6 mg kg^?1) and diet 3 (24.1 mg kg^?1) were significantly (P < 0.05) higher than in those fed diet 1 (18.2 mg kg^?1). Whole body total saturated fatty acids were significantly lower, and DHA levels higher in fish fed diets 2 and 3 than those fed diet 1. The results of the present study suggest that increasing dietary supplementation of vit. E in high lipid diets enhances the growth performance of fish and that a dietary level of 196 mg kg^?1 vit. E is suitable for the growth of silver pomfret.     

Ionregulation in juvenile swordspine snook (Centropomus ensiferus,Poey, 1860) in relation to environmental salinity

Ninety‐nine swordspine snook Centropomus ensiferus (9.80 ± 0.3 g, mean ± SE) were studied in order to evaluate the influence of salinity on physiological properties under rearing conditions. Growth performance, survival rates, and ion concentrations (Na⁺, K⁺, Cl^?) as well proximal composition were measured over 76 days. Fish were exposed to three experimental salinities (0, 10, 20 ‰ , three replicates per treatment) and maintained in plastic tanks with a recirculation system equipped with flow‐through aquaria pumps (533 L per tank). Fish were fed twice daily to apparent satiation; at the end of the experiment the weight of fish kept in 10 ‰ was higher than that of fish kept in 0 and 20 ‰ , however no significant differences (P > 0.05) were observed among the experimental salinities. Survival was significantly lower in 10 ‰ salinity than in fish kept in 20 and 0 ‰ salinities. No significant differences (P > 0.05) were found in the Condition factor (K), specific growth rate (SGR), or in plasma Na⁺, K⁺, or Cl^? concentrations among treatments. Salinities also did not affect body composition (P > 0.05), but were significantly lower (P < 0.05) than at the start of the experiment. However, towards the end of the experiment a large accumulation of visceral fat in fish farmed in the three salinities (VFI > 4%) was observed. Water quality was within the optimum range (T: 28.7 ± 0.1°C; O2: 5.6 ± 0.1 mg L^?1; ammonia: 0.2 mg L^?1) for the growth of swordspine snook. Data indicates that C. ensiferus is an ionoregulator fish and able to cultivate successfully in various osmotic conditions, and in turn, maintain high levels of survival in captivity.     

Switching among natal and auxiliary hosts increases vulnerability of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) to insecticides

The role of insecticidal application and host plant resistance in managing Spodoptera exigua has been well documented, but the effect of different host plants, on which the pest cycles its population in the field, has seldom been investigated. Therefore, we have studied the vulnerability of S. exigua against commonly used insecticides (cypermethrin, chlorpyrifos, lufenuron, and emamectin benzoate) with different mode of actions when it switches its generations from natal to auxiliary hosts and vice versa. Different field populations being established on different host plants including castor, cauliflower, cotton, okra, and spinach were collected and reared in the laboratory before insecticidal bioassays. The role of larval diet and host plant switching on their response to tolerate applied insecticides was studied using leaf‐dip bioassay methods. Host switching demonstrated a significant role in altering the vulnerability of S. exigua populations to tested insecticides. Spodoptera exigua sourced from castor, when switched host to okra and spinach, exhibited 50% higher mortality when treated with emamectin benzoate. This trend in mortality was consistent upon complete host switch cycle (natal—auxiliary—natal host). However, the highest increase (92%) in vulnerability was recorded when the larvae were shifted to spinach from cotton. In general, chlorpyrifos and lufenuron had highest efficacies in terms of larval mortality. The findings of present studies provide insights to a better understanding the behavior of polyphagous pests and the role of different host plants in altering the susceptibility of these pests against applied insecticides. Ultimately the results warrant that due consideration should be given to cropping patterns and time of host switching by pest population during planning and executing chemical control.     

防治新入侵害虫蜂巢小甲虫杀虫剂的室内筛选

蜂巢小甲虫Aethina tumida是一种新入侵为害蜜蜂蜂巢的危险性害虫,筛选出具有较高毒力水平的化学药剂防治该虫迫在眉睫。本文采用浸渍法测定了10种杀虫剂对蜂巢小甲虫幼虫的毒力。试验结果表明,10 mg/L高效氯氰菊酯、啶虫脒和功夫菊酯在24 h内对蜂巢小甲虫幼虫的致死率达到36.67%、33.33%和29.39%,而10 mg/L高效氯氰菊酯和功夫菊酯在48 h对蜂巢小甲虫幼虫的致死率均达到100%。啶虫脒、高效氯氰菊酯和功夫菊酯在24 h的LC_(50)分别为10.47 mg/L、16.94 mg/L和19.1 mg/L。其它受试的杀虫剂如多杀菌素、氟虫腈、氟啶脲、虫酰肼、敌百虫、阿维菌素和甲维盐的触杀致死率相对较低。筛选结果显示,啶虫脒、高效氯氰菊酯和功夫菊酯可作为目前防治蜂巢小甲虫的的重要参考防治药剂。     

Assessing the resistance risk to emamectin benzoate in Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae): selection,cross-resistance dynamics and estimates of realized heritability

Emamectin benzoate, a non-systemic, translaminar, and broad spectrum insecticide, is excessively used in cotton. It kills the pest by suppressing the muscle contraction. Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) is one of the major sap sucking pests of cotton in many countries and has been shown resistance to various insecticides. In this study, we have continuously selected P. solenopsis with emamectin benzoate in the laboratory from G₃ to G₁₈ to determine the resistance development and resistance risk to emamectin benzoate and also to evaluate the dynamics of cross-resistance (CR) development with three other insecticides. After continuing selection of P. solenopsis for 16 generations with emamectin benzoate, the emamectin selected strain (Ema-SEL) developed a 280.15-fold resistance when tested at G₁₉. Ema-SEL strain showed no CR to abamectin (0.28–1.65-fold), and profenofos (0.12–0.29-fold), but a very low to low CR to cypermethrin (6.02–11.29-fold). Abamectin was negatively cross-resistant with emamectin benzoate in Ema-SEL strain at G₁₃, G₁₅ and G₁₉ while profenofos also exhibited similar results at G₁₃, G₁₅, G₁₇ and G₁₉. Realized heritability (h²) of resistance to emamectin benzoate was 0.24 from G₃ to G₁₉. The results of projected rate of resistance development showed that if h² = 0.24, 0.34, and 0.44 at slope = 1.08, then 2.03, 1.43, and 1.11 generations, respectively are required for tenfold increase in LC₅₀ at 95 % selection intensity. Results of the present study suggested that P. solenopsis has the ability to develop resistance to emamectin benzoate but it can be managed by the alternate use of other insecticides including abamectin, profenofos and cypermethrin due to lack of/or very low to low CR with these insecticides.     

Feeding response of the cotton aphid,Aphis gossypii,to sublethal rates of flonicamid and imidacloprid

The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is an important sap‐sucking pest of many plants, including melons and peppers. This study was conducted to determine the effects of sublethal exposure to flonicamid and imidacloprid and the mechanisms by which these insecticides affect the feeding behavior of A. gossypii. The median lethal concentrations (LC₅₀) of flonicamid and imidacloprid for adult A. gossypii were 2.40 and 1.92 mg l^?1, respectively. The lower lethal concentrations of flonicamid were 1.01 mg l^?1 (LC₃₀) and 0.29 mg l^?1 (LC₁₀), and those of imidacloprid were 0.82 mg l^?1 (LC₃₀) and 0.24 mg l^?1 (LC₁₀). The developmental period of A. gossypii nymphs at LC₃₀ was 3.6 days for both insecticides, which was shorter than that of the untreated controls (4.2 days). Longevity and total fecundity of A. gossypii adults were decreased at the sublethal concentrations of both insecticides. The lowest net reproductive rate was observed in A. gossypii treated with the LC₃₀ of flonicamid. Feeding behavior analyses using an electrical penetration graph showed that sublethal concentrations of flonicamid and imidacloprid had significant effects on the duration of phloem ingestion. Higher doses of flonicamid induced starvation by inhibiting phloem ingestion, whereas imidacloprid acted as a contact toxin rather than an inhibitor of feeding behavior.     

Effects of metalaxyl enantiomers stress on root activity and leaf antioxidant enzyme activities in tobacco seedlings

The objective of this experiment was to study the effects of metalaxyl enantiomers on the activity of roots and antioxidative enzymes in tobacco seedlings. Water culture experiment was conducted to analyze the effects of different concentrations of metalaxyl enantiomers (30 and 10 mg L^?1) on root activity and leaf superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities and malondialdehyde (MDA) content of tobacco seedlings. The results showed that metalaxyl significantly inhibited root activity and significantly improved leaf SOD, POD, and CAT activities and MDA content. A better physiological response in tobacco seedlings was observed at 30 mg L^?1 than at 10 mg L^?1 metalaxyl. The stereoselectivity for different enantiomers had no obvious effect on root activity and the leaf POD activity, but it affected significantly the SOD and CAT activities and MDA content. The SOD activity was promoted more by R‐enantiomer than by S‐enantiomer at 30 mg L^?1 metalaxyl, and the same effect was observed on CAT activity from the beginning to the end of the stress period. The MDA content under the stress by R‐enantiomer was higher than that under the stress by S‐enantiomer at 10 mg L^?1 metalaxyl.     

Microalgae for phosphorus removal and biomass production: a six species screen for dual‐purpose organisms

Microalgae biofuel production can be feasible when a second function is added, such as wastewater treatment. Microalgae differ in uptake of phosphorus (P) and growth, making top performer identification fundamental. The objective of this screen was to identify dual‐purpose candidates capable of high rates of P removal and growth. Three freshwater – Chlorella sp., Monoraphidium minutum sp., and Scenedesmus sp. – and three marine – Nannochloropsis sp., N. limnetica sp., and Tetraselmis suecica sp. – species were batch cultured in 250 mL flasks over 16 days to quantitate total phosphorus (TP) removal and growth as a function of P loads (control, and 5, 10, and 15 mg L^?1 enrichment of control). Experimental design used 100 μmol m^?2 s^?1 of light, a light/dark cycle of 14/10 h, and no CO₂ enrichment. Phosphorus uptake was dependent on species, duration of exposure, and treatment, with significant interaction effects. Growth was dependant on species and treatment. Not all species showed increased P removal with increasing P addition, and no species demonstrated higher growth. Nannochloropsis sp and N. limnetica sp. performed poorly across all treatments. Two dual‐purpose candidates were identified. At the 10 mg L^?1 treatment Monoraphidium minutum sp. removed 67.1% (6.66 mg L^?1 ± 0.60 SE) of TP at day 8, 79.3% (7.86 mg L^?1 ± 0.28 SE) at day 16, and biomass accumulation of 0.63 g L^?1 ± 0.06 SE at day 16. At the same treatment Tetraselmis suecica sp. removed 79.4% (6.98 mg L^?1 ± 0.24 SE) TP at day 8, 83.0% (7.30 mg L^?1 ± 0.60 SE) at day 16, and biomass of 0.55 g L^?1 ± 0.02 SE at day 16. These species merit further study using high‐density wastewater cultures and lipid profiling to assess suitability for a nutrient removal and biomass/biofuel production scheme.     

Evaluation of optimum dietary vitamin E requirements using DL‐α‐tocopheryl acetate in the juvenile eel,Anguilla japonica

The study aimed at evaluating the optimum dietary vitamin E requirements using DL‐α‐tocopheryl acetate in the juvenile eel, Anguilla japonica, as assessed by fish growth performance and fish body composition. Five semi‐purified experimental diets were formulated to contain 0 (TA₁), 15 (TA₁₇), 30 (TA₃₂), 60 (TA₆₂) and 120 (TA₁₁₉ mg TA kg^?1 diet on a dry matter (DM) basis in the form of DL‐α‐tocopheryl acetate (TA). After a 4‐week conditioning period, fish (15 ± 0.3 g) were randomly distributed into aquaria in groups of 20 at 25 ± 1.0°C (mean ± SD). One of the five diets was fed on a DM basis to fish in three randomly selected aquaria twice daily to satiation (approximately 3% of wet body weight per day at the beginning and 2% of wet body weight per day at the end of the feeding trial) for 12 weeks. At the end of the 12‐week feeding trial, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) were determined; these were significantly lower in control fish than in fish fed supplemented diets (P < 0.05). The values for fish fed TA₁₇ were significantly higher than for fish fed TA₁, TA₆₂ or TA₁₁₉ (P < 0.05). There were no significant differences in WG, FE or PER among fish that were fed TA₁₇ and TA₃₂, among those that were fed TA₃₂ and TA₆₂, and among those that were fed TA₆₂ and TA₁₁₉ (P > 0.05). There were also no significant differences in SGR among fish fed TA₃₂, TA₆₂ or TA₁₁₉ (P > 0.05). A broken‐line regression analysis on the basis of WG, SGR, FE and PER showed that dietary vitamin E requirements of juvenile eels were 21.2, 21.6, 21.2 and 21.5 (mg kg^?1 diet), respectively. These results indicate that the dietary vitamin E requirement could be <21.2 mg kg^?1 but <21.6 mg kg^?1 diet in juvenile eel, A. japonica, when DL‐α‐tocopheryl acetate is used as the dietary vitamin E source.     

6种杀虫剂对南美番茄潜叶蛾的毒力及田间防效

[目的]研究6种杀虫剂对南美番茄潜叶蛾卵、幼虫和成虫的毒力及其在温室番茄上的防治效果,为南美番茄潜叶蛾防治提供高效杀虫剂和施药技术。[方法]采用浸渍法和药膜法测定了6种杀虫剂对南美番茄潜叶蛾卵、幼虫和成虫的毒力,田间调查毒力较高杀虫剂对温室番茄上南美番茄潜叶蛾防效。[结果] 6种杀虫剂中的乙基多杀菌素、甲氨基阿维菌素苯甲酸盐和阿维菌素对南美番茄潜叶蛾卵有毒力作用,致死中浓度（LC₅₀）分别为1.415、13.588和23.194 mg·L^-1。6种杀虫剂对南美番茄潜叶蛾幼虫的LC₅₀分别为：阿维菌素0.026 mg·L^-1、四唑虫酰胺0.052 mg·L^-1、甲氨基阿维菌素苯甲酸盐0.057 mg·L^-1、乙基多杀菌素0.072 mg·L^-1、氯虫苯甲酰胺0.484 mg·L^-1和呋虫胺2.039 mg·L^-1。对于南美番茄潜叶蛾成虫,24 h时,仅甲氨基阿维菌素苯甲酸盐和四唑虫酰胺对成虫有较高毒力;72 h时,6种杀虫剂对成虫的LC₅₀分别为：甲氨基阿维菌素苯甲酸盐0.390 mg·L^-1、乙基多杀菌素1.646 mg·L^-1、四唑虫酰胺2.630 mg·L^-1、呋虫胺5.577 mg·L^-1、阿维菌素22.502 mg·L^-1和氯虫苯甲酰胺39.636 mg·L^-1。在成虫盛发期第4天施药,阿维菌素、四唑虫酰胺、甲氨基阿维菌素苯甲酸盐、乙基多杀菌素在南美番茄潜叶蛾危害严重的温室番茄上防效达80%以上。[结论]阿维菌素、四唑虫酰胺、甲氨基阿维菌素苯甲酸盐、乙基多杀菌素、氯虫苯甲酰胺和呋虫胺对南美番茄潜叶蛾卵、幼虫或成虫有较高毒力,其中阿维菌素、四唑虫酰胺、甲氨基阿维菌素苯甲酸盐和乙基多杀菌素田间防效较好。     

Increases in benthic community production and metabolism in response to marine‐derived nutrients from spawning Atlantic salmon (Salmo salar)

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Zinc nutrition increases the antioxidant defenses of honey bees

Is the typical zinc (Zn) content of honey and pollen sufficient to meet the nutritional requirements of honey bees? To answer this question, and find the optimal dietary Zn levels for honey bees, we investigated the effects of varying dietary Zn levels on both captive worker bees and free‐flying honey bees, Apis mellifera ligustica Spinola (Hymenoptera: Apidae). We fed captive workers and free‐flying honey bees with 50% (wt/wt) sucrose solutions with Zn levels of either 0, 15, 30, 45, 60, or 75 mg kg^?1 diet and measured their Cu/Zn‐SOD activity, the mean survival time of captive bees, the Cu/Zn‐SOD activity of larvae, and the Zn concentration of royal jelly. Captive workers provided with 30 mg kg^?1 dietary Zn had higher Cu/Zn‐SOD activity and mean survival time than the control. Dietary Zn levels from 60 to 75 mg kg^?1 significantly increased the Zn content of royal jelly provided by colonies and the Cu/Zn‐SOD activity of larvae. Honey or pollen with a Zn content of <30 mg kg^?1 was insufficient to satisfy the maintenance nutritional requirements of bees that were not raising larvae. It therefore seems advisable to supply supplementary Zn to non‐brooding colonies when the Zn content of honey or pollen is <30 mg kg^?1. Honey or pollen with a Zn content of 60 mg kg^?1 was sufficient to satisfy the nutritional requirements for royal jelly production and to improve the health of larvae. It may therefore also be advisable to provide supplementary Zn to colonies with larvae when the Zn content of honey or pollen is <60 mg kg^?1.     

Comparative selectivity of pesticides used in greenhouses,on the aphid parasitoid Aphidius colemani (Hymenoptera: Braconidae)

A series of bioassays were conducted under laboratory conditions to determine the relative toxicities of various pesticides (acetamiprid, cypermethrin, chlorantraniliprole and emamectin benzoate, Bacillus thuringiensis var. kurstaki and Helicoverpa armigera nucleopolyhedrovirus, copper oxychloride, iprodione, mandipropamid, a mixture of propamocarb?+?fluopicolide and mixture of fludioxonil?+?cyprodinil) on Aphidius colemani adults and mummies, as well as sublethal effects on female fecundity. Cypermethrin was highly toxic to pupa of A. colemani within host mummies. Acetamiprid, cypermethrin, emamectin benzoate, a mixture of propamocarb?+?fluopicolide and mixture of fludioxonil?+?cyprodinil were also highly toxic to A. colemani adults (92–100% mortality at 48?h post treatment). Mandipropamid, iprodione and copper oxycloride treatments significantly reduced fecundity of the female parasitoids. In contrast B. thuringiensis var. kurstaki, H. armigera nucleopolyhedrovirus and chlorantraniliprole were harmless (<30% mortality) to the parasitoid species tested according to International Organisation for Biological Control toxicity classification and are likely to be compatible with integrated pest management programmes.     

Field evaluation of nucleopolyhedrosis virus and some biorational insecticides against Helicoverpa armigera Hubner (Noctuidae: Lepidoptera)

American bolloworm, Helicoverpa armigera Hubner (Noctuidae: Lepidoptera) is considered as a major pest of various crops all over the world. It is mainly controlled by indiscriminate use of synthetic insecticides in the world due to which this pest developed resistance to most of the available insecticides. Therefore, in the current study, the efficacy of virulent strain of HaNPV (0.5 × 10⁹ PIB/ml) alone and in combination with recommended doses of spintoram (20 g/100 L of water) and emamectin benzoate (200 ml/100 L of water) was tested in field. The combination of HaNPV with spintoram and emamectin benzoate 100% reduced the larval population as compared to emamectin benzoate and HaNPV alone. This suggested that the combination of spintoram and emamectin benzoate with HaNPV could be used in field to manage the infestation of H. armigera.     

Effects of ammonia on growth,digestion and antioxidant capacity in juvenile yellow catfish Pelteobagrus fulvidraco (Richardson, 1846)

Effects of ammonia stress on food ingestion, growth, digestion and antioxidant capacity were investigated in juvenile yellow catfish Pelteobagrus fulvidraco (Richardson) with initial body weights of 20.24 ± 0.18 g. The fish were reared in triplicate in 15 experimental tanks at a rate of 30 fish per tank for 56 days. Water was maintained at a dissolved oxygen (DO) level of over 6.2 mg L^?1, pH 7.2–7.6, and temperature of 29.0 ± 1.5°C under a natural 12L: 12D photoperiod. Survival, food ingestion (FI), specific growth rate (SGR), food conversion efficiency (FCE), apparent digestibility coefficient (ADC), total antioxidant capacity (T‐AOC), levels of glutathione (GSH) and malonaldehyde (MDA), and activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH‐PX) of the juveniles were determined in total ammonia nitrogen (NH₃‐N+NH₄‐N) levels of 0 (control group), 3.36, 6.72, 13.44 and 26.88 mg L^?1. The results show that the survival, FI, SGR, FCE, and ADC decreased significantly with an increase in total ammonia nitrogen (p < .05), and a significantly negative correlation between SGR and total ammonia nitrogen levels (p < .05). T‐AOC, SOD, CAT, GSH‐PX and GSH in the blood, liver and gills were found to decline significantly with an increase in the total ammonia nitrogen level (p < .05), while the MDA in the blood, liver and gills was elevated significantly with the increase in total ammonia nitrogen (p < .05). The results indicate a threshold in the induction of the T‐AOC and activities of antioxidant enzymes in yellow catfish tissues with a total ammonia nitrogen increase. In the present study the total ammonia nitrogen threshold thus changed from 6.72 mg L^?1 in the juvenile yellow catfish.     

Growth response of cultured larvae of silver therapon Leiopotherapon plumbeus (Kner, 1864) in outdoor tanks in relation to fertilizer type and fish density

This study evaluated the effects of fertilizer type and fish density on early growth and survival of silver therapon Leiopotherapon plumbeus (Kner, 1864) larvae reared in outdoor tanks. In the first experiment, larvae (1.92 ± 0.09 mm total length) were stocked into nine, 4 m³ tanks at an initial density of 0.5 larvae L^?1 and reared for 42 days at an ambient temperature of 28.8–30.7°C. Three treatments with three replicates each were compared: organic (chicken manure, OF) or inorganic fertilizers (ammonium phosphate, IF) applied once every 2 weeks, and the unfertilized (NF) tanks serving as the control group. Water quality, zooplankton densities, survival or growth of L. plumbeus larvae did not vary significantly in either fertilized or unfertilized tanks. Fertilization resulted in elevated nutrient concentrations, which did affect survival (2.10%–6.07%) of the fish larvae. In the second experiment, larvae were stocked at densities of 0.4 or 0.6 larvae L^?1 in tanks fertilized at 4–5 days interval with OF and IF for 30 days. Growth performance of L. plumbeus larvae was affected by fish density, with significantly larger (20.04 ± 2.65 mm in total length) and higher specific growth rate (SGR; 6.97 ± 0.48% day^?1) at 0.4 larvae L^?1 than at 0.6 L^?1. Fry production did not vary significantly between fish density treatment groups given the same fertilizer types, but survival rates were improved at 0.4 L^?1. Together, production of L. plumbeus larvae in outdoor tanks can be optimized at a lower stocking density, regardless of the type of fertilizer used.     

The effects of α‐pinene on the feeding performance and pheromone production of Dendroctonus valens

Herbivorous insects exploit multiple plant cues to detect and orient toward suitable hosts and, accordingly, hosts have evolved complex constitutive and inducible defenses in response. In China, the red turpentine beetle, Dendroctonus valens LeConte (Coleoptera: Curculionidae: Scolytinae), an invasive bark beetle from North America, attacks mainly Pinus tabuliformis Carrière (Pinaceae), which contains many monoterpenes. In this study, we explored how the monoterpene α‐pinene affects the feeding performance and pheromone production of D. valens. First, the composition and quantities of monoterpenes of both P. tabuliformis healthy trees and fresh stumps were determined and the infestation of D. valens in healthy trees and fresh stumps was investigated, linking the amount of monoterpenes and D. valens infestation. Gas chromatography–mass spectrometry (GC‐MS) analysis showed that P. tabuliformis mainly contained α‐pinene, with concentrations of 0.1 and 0.5 mg g^?1 in healthy pine phloem and stump phloem, respectively. Second, the monoterpene's influence on feeding performance was tested using phloem media with α‐pinene concentrations ranging from 0 to 30 mg g^?1. The results showed that the percentages of beetles boring and the gallery lengths of both adult females and larvae were negatively correlated with the α‐pinene concentration although body weight changes did not correlate with α‐pinene concentration. Finally, pheromone analysis showed that the production of all pheromones increased with increasing α‐pinene concentrations. This study showed the dual effects of α‐pinene on D. valens: α‐pinene inhibited the bark beetle's feeding activities and in turn the bark beetle made use of it to produce pheromones. Our study indicated the importance of promptly removing fresh stumps in the field for the management of the bark beetle.     

Influence of Tribulus terrestris extract on the survival and histopathology of Oreochromis mossambicus (Peters, 1852) fry before and after Streptococcus iniae infection

The aim of this study was to determine the effects of Tribulus terrestris extract (TT) on growth performance, disease resistance and histopathological changes in intestine and liver tissues of Oreochromis mossambicus (Peters, 1852) first‐feeding fry before and after exposure to Streptococcus iniae. Five isonitrogenous and isocaloric diets were formulated to contain 0 (control), 200, 400, 600, and 800 mg kg^?1 TT. After feeding for 45 days, fish were infected with S. iniae and mortalities recorded. Final weight, weight gain and SGR of tilapia fry fed the 400 mg kg^?1 TT diet were significantly greater than that of control diet. In the challenge experiment, the best survival rate was obtained with 400 mg kg^?1 TT supplementation. Infection by S. iniae appeared to have a negative effect on histopathological findings and outcome than did TT‐800 used alone. However, administration of TT (200 or 400 mg extract kg^?1) resulted in overall improvement in the intestine and liver histopathology, emphasizing the protective potential of TT. The present study suggests the protective potential of TT in alleviating intestinal and hepatic damage that can occur after a S. iniae infection. It was concluded that 400 mg kg^?1 TT can enhance growth and disease resistance during first–feeding of O. mossambicus fry. This suggests that TT may be an alternative to antibiotics in controlling streptococcal disease in tilapia culture.