African Catfish Larvae Research Articles

The Performance of Rotifer <i>Brachionus plicatilis</i> (Müller 1786) and Chicken Egg Yolk on the Larval Rearing of African Catfish, <i>Clarias gariepinus</i> (Burchell 1822) in Hatchery

800x600 The possibility of utilizing rotifer Brachionus plicatilis (Muller, 1786), broiler chicken egg yolk, and a mixture of the two as starter feeds in the larval rearing of African catfish ( Clarias gariepinus, Burchell, 1822) was explored. Larvae of four days following commencement of exogenous feeding were used for the purpose. The experiment lasted for 15 days under ambient hatchery conditions in a set of nine tanks of 900 litres capacity randomly allocated. The experiment was carried out in two phases. In the end of each phase, the larvae from each set of tanks were counted and from each feed treatment 30 larvae were randomly chosen and measured their weights and lengths for the estimation of average weight and length. The average lengths of the larvae from each phase and each feed treatment were used for the estimation of growth rates, survival %, specific growth rate (SGR), and conditional factor (CF). During the 1 st phase, the larvae fed with rotifers indicated the highest survival (98%) with poorest growth rate (25.76%/day). During the 2 nd phase (weaning period), the larvae fed with rotifers indicated the poorest survival (54%) while those fed with egg yolk indicated the highest growth (weight and length of 19.85±3.66mg and 12.13±0.60mm, respectively) and survival of 61%. The findings imply that rotifers are too small for the rearing of African catfish larvae, thus unsuitable. Chicken egg yolk can successfully be used as a substitute of live diet for rearing of African catfish larvae if need arises . Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Times New Roman,serif;}

Toxicity of buprofezin on the survival of embryo and larvae of African catfish, Clarias gariepinus (Bloch).

Buprofezin is an insect growth regulator and widely used insecticide in Malaysia. The present study evaluated the toxic effects of buprofezin on the embryo and larvae of African catfish (Clarias gariepinus) as a model organism. The embryos and larvae were exposed to 7 different concentrations (0, 0.05, 0.5, 5, 25, 50 and 100 mg/L) of buprofezin. Each concentration was assessed in five replicates. Eggs were artificially fertilized and 200 eggs and larvae were subjected to a static bath treatment for all the concentrations. The mortality of embryos was significantly increased with increasing buprofezin concentrations from 5 to 100 mg/L (p< 0.05). However, the mortality was not significantly different (p<0.05) among the following concentrations: 0 (control), 0.05, 0.5 and 5 mg/L. Data obtained from the buprofezin acute toxicity tests were evaluated using probit analysis. The 24 h LC50 value (with 95% confidence limits) of buprofezin for embryos was estimated to be 6.725 (3.167-15.017) mg/L. The hatching of fish embryos was recorded as 68.8, 68.9, 66.9, 66.4, 26.9, 25.1 and 0.12% in response to 7 different concentrations of buprofezin, respectively. The mortality rate of larvae significantly (p<0.05) increased with increasing buprofezin concentrations exposed to 24-48 h. The 24 and 48 h LC50 values (with 95% confidence limits) of buprofezin for the larvae was estimated to be 5.702 (3.198-8.898) and 4.642 (3.264-6.287) mg/L respectively. There were no significant differences (p>0.05) in the LC50 values obtained at 24 and 48 h exposure times. Malformations were observed when the embryos and larvae exposed to more than 5 mg/L. The results emerged from the study suggest that even the low concentration (5 mg/L) of buprofezin in the aquatic environment may have adverse effect on the early embryonic and larval development of African catfish.

Reduced Cannibalistic Behavior of African Catfish,Clarias gariepinus, Larvae Under Dark and Dim Conditions

In general, African catfish shows higher survival rates in the dark conditions than in the light conditions. In this study, larval behavior of African catfish was observed under 0, 0.01, 0.1, 1, 10, and 100 lx using a CCD camera to investigate the reason why African catfish larvae show higher survival rates in dark conditions. The larvae showed significantly higher swimming activity under 0, 0.01, and 0.1 lx than that under 10 and 100 lx. The larvae also showed significantly increased aggressive behavior under 10 and 100 lx; the swimming larvae attacked resting individuals more frequently under 10 and 100 lx than under 0, 0.01, and 0.1 lx. The aggressive behavior and sharp teeth of the attacking larvae appeared to induce skin surface lesions on injured larvae. Chemical substances were then generated from the injured skin surface, and these chemical stimuli triggered cannibalistic behavior in other fish near the injured fish. The results of this study demonstrate that the higher survival rates of African catfish larvae under dark conditions are a result of inactivity and subsequent increase in chemical releasing stimuli concentrations around inactive individuals that triggers feeding behavior in nearby active catfish. Therefore, we recommend larval rearing of African catfish in dark or dim conditions, as it improves catfish survival rates.

Fatty Acid Profiles and Growth of African Catfish Larvae Fed on Freshwater Cyclopoid Copepods and &lt;i&gt;Artemia&lt;/i&gt; as Live Starter Feed

The possibility of utilizing freshwater crustaceans (Cyclopoid copepods) as an alternative live starter feed for African catfish ( Clarias gariepinus , Burchell, 1822) larvae was explored. Larvae cultured in experimental tanks under ambient hatchery conditions were tested on three experimental diets for three days following commencement of exogenous feeding: freshly decapsulated Artemia cysts, early stages of Cyclopoids-copepods and a combination of the two. Change in total length measurements of larvae was used as a measure of growth. Fatty acid profiles of four-day old larvae were determined using Gas chromatography-mass spectrometry (GC-MS) method. Overall, growth of catfish larvae was significantly different (F=25.94, P<0.05) across diets. Cyclopoid- Artemia -fed larvae grew faster (9.1±0.89) mm, followed by Cyclopoid-fed larvae (8.8±0.92) mm and Artemia -fed larvae (8.6±0.79) mm. Similarly, significantly high composition of α linolenic acid (LNA), Arachidonic acid (AA), and Docosahexaenoic acid (DHA) were recorded for Cyclopoid copepods-fed larvae than for Artemia -fed larvae (LNA, F=14.7, P=0.028; AA, F=12.1, P=0.037 and DHA, F=101.9, P=0.002, respectively) . These essential fatty acids play a significant role in the structural, physiological and functional development of larval fish thus promoting growth. A combination of Cyclopoid copepods with Artemia was of an added advantage possibly due to the large-sized Artemia that makes catchability easy. These results demonstrated that p artial or total replacement of Artemia with Cyclopoid copepods as a live starter feed for African catfish larvae is feasible but call for further investigations on cost benefit analysis.

Growth performance, survival, feed utilization and nutrient utilization of African catfish (Clarias gariepinus) larvae co-fed Artemia and a micro-diet containing freshwater atyid shrimp (Caridina nilotica) during weaning

Problems of limited number of dry feeds as supplement or replacement of live feeds have led to poor larval nutrition in many species of fish. Therefore, the suitability of co-feeding 8-day-old African catfish (Clarias gariepinus) posthatch larvae using live feed (Artemia salina) and formulated dry diet containing freshwater atyid shrimp (Caridina nilotica) during weaning was investigated. The experiment ended after 21 days of culture and respective groups compared on the basis of growth performance, survival, feed utilization and nutrient utilization. Larvae co-fed using 50%Artemia and 50% formulated dry diet resulted in significantly (P < 0.05) better growth performance, food gain ratio (FGR), protein efficiency ratio (PER) and productive protein values (PPV) than other treatments. The lowest growth performance occurred in larvae weaned using 100% formulated and commercial dry diets. Better survival of over 90% was obtained in larvae weaned using 50%Artemia and 50% dry diet, while abrupt weaning using 100% dry diets resulted in lower survival (<75%). These results support a recommendation of co-feeding C. gariepinus larvae using a formulated dry diet containing C. nilotica and 50% live feed when weaning is performed after 8 days posthatching period.

Growth performance and survival of hybrid African catfish larvae (&lt;i&gt;Clarias gariepinus x Heterobranchus bidorsalis&lt;/i&gt;) fed on different diets

The study evaluates the growth performance and survival of hybrid African catfish larvae (Clarias gariepinus X. Heterobranchus bidorsalis) fed different diets: live Artemia nauplii, decapsulated Artemia cysts, live Ceriodaphnia sp and commercial dry diet (50% crude protein). Catfish larvae of mean weight 10.01±0.01mg of mean length 9.05±0.09mm were fed from the onset of exogenous feeding for 28days in plastic aquaria tanks (10L capacity each). At the end of the feeding trial, the highest weight gain, 889.99±5.00mg was recorded for the larvae fed with decapsulated Artemia cysts followed by those fed with live Ceriodaphnia with mean weight gain of 442.66 ± 2.24mg. The least weight gain 60.42 ± 1.80mg was obtained in larvae fed with commercial diet. The best and the least specific growth rates (SGR), 16.07 ± 0.02 and 6.97 ± 0.01 were also obtained in larvae fed decapsulated Artemia cysts and commercial diet respectively. Statistically, all the results of the growth parameters obtained from the different diets were significantly different (p

Growth and Survival of African Catfish (Clarias gariepinus) Larvae Fed Decapsulated Artemia, Live Daphnia, or Commercial Starter Diet

The effects of three diets (decapsulated Artemia, live Daphnia spp., and commercial starter diet) on the growth and survival of Clarias gariepinus larvae were investigated in the laboratory for seven days using a completely randomized block design. Larvae were hatched by the hypophysation technique and, immediately after resorption of the yolk sac, randomly distributed into nine tanks at a stocking rate of 180 larvae per experimental plastic tank. Triplicate groups were fed treatment diets ad libitum twice daily, in the morning and in the evening. The highest growth values were obtained in larvae fed decapsulated Artemia (p&lt;0.05), while the survival rate was similar in fish fed decapsulated Artemia and live daphnia. It is concluded that feeds of animal origin are more suitable for first feeding of C. gariepinus larvae than inert diets.

Evaluation of the suitability of various dry and moist feeds for rearing larvae of the catfish, Heterobranchus longifilis (Teleostei, Clariidae)

The effects of various dry and moist diets on water quality, feeding behaviour, mortality and growth of the African catfish (Heterobranchus longifilis) larvae were investigated in a twelve day feeding trial. Five food types and one reference diet were tested in duplicate: Beef liver (BL), beef brain (BB), beef liver and beef brain (BL & BB), toasted soya beanmeal (SB), SB and tilapia fish meal (FM). The reference diet consisted of decapsulated Artemia cysts (AC). One group of larvae received no food (NF) and was included to determine their survival under starvation. The larvae were fed in excess of their requirements, 6 times during the daytime at 2-hour intervals, from the onset of exogenous feeding,which occurred 56-62 hours after hatching.Water quality did not undergo any degradations likely to induce fish kills. The final mean length (16.7 mm) and weight (38.5 mg), growth rate (3.06 mg.d-1), specific growth rate (31.4 %.d-1), condition factor (0.83) and survival rate (91.4 %) of fish fed decapsulated Artemia cysts were significantly higher than those of fish fed other diets (P less than 0.05). The dry diets based on soya and fish meal led to significantly lower growth and survival rates in comparison to the moist diets based on beef liver and beef brain.The results also indicated that the moist diet based on the mixture of beef liver and beef brain produced the highest specific growth rate (19.04 %.d-1) and survival (68 %) compared to other dry and moist diets. It was observed that larvae in starving conditions increased in length up to 5 days of age, and 7% survived at the end of the trial.

Pengkayaan Daphnia spp. Dengan Viterna Terhadap Kelangsungan Hidup Dan Pertumbuhan Larva Ikan Lele Dumbo (Clarias gariepinus) &lt;Br&gt;&lt;I&gt;[Enrichment Of Daphnia spp. With Viterna To Survival And Growth Of African Catfish (Clarias gariepinus) Larvae]&lt;I&gt;

Abstract African catfish (Clarias gariepinus) is one of fish consumption use to fulfill animal protein. The fulfillment need of animal protein with aquaculture effort, where as in the aquaculture effort will larvae quality increased. Increasingly of larvae quality with natural food had been adding feed supplement. Natural food to used is Daphnia spp. and then food supplement to used is viterna. The viterna will increase Daphnia nutritions, because of the viterna contains many nutritions to survival and growth of African catfish. The aim of this study was to know the influence of Daphnia spp. enrichment with viterna to survival and growth of African catfish (Clarias gariepinus) larvae. The rearing of larvae during 40 days. This study used Complete Random Design. The treatment were A (present Daphnia spp. without viterna), B (Daphnia spp. enrichment with viterna 10 ml/L dose), C (Daphnia spp. enrichment with viterna 10 ml/L dose), D (Daphnia spp. enrichment with viterna 10 ml/L dose), E (Daphnia spp. enrichment with viterna 10 ml/L dose) dan F (Daphnia spp. enrichment with viterna 10 ml/L dose), each treatment with 4 replications. The result show that viterna applications to Daphnia was significantly influenced (p&lt;0,05) to survival African catfish larvae. The highest survival was E treatment (7,25 %). The viterna leaf to Daphnia spp. Was significantly influenced (p&lt;0,05) to specific growth rate African catfish larvae. The highest specific growth rate was B treatment (1,885 %BW/day).

Regulation of body mass growth through activin type IIB receptor in teleost fish

Myostatin is a TGF-β family member that plays a key role in regulating skeletal muscle growth. Previous studies in mammals have demonstrated that myostatin is capable of binding the two activin type II receptors. Additionally, activin type II receptors have been shown to be capable of binding a number of other TGF-β family members besides myostatin. An injection of a soluble form of activin type IIB receptor obtained from CHO cells into wild-type mice generated up to a 60% increase in muscle mass in 2 weeks. The knowledge on the role of activin receptors in fish is limited. In the present study, we examined the growth effect of administering a recombinant, soluble form of goldfish activin type IIB receptor extracellular domain to juvenile and larval goldfish ( Carassius auratus), African catfish ( Clarias gariepinus) larvae and tilapia ( Oreochromis aureus) larvae. We have expressed the goldfish activin type IIB receptor extracellular domain in the yeast Pichia pastoris and we have demonstrated for the first time that this recombinant molecule stimulates growth in teleost fish in a dose-dependent manner. We provide evidence that this body weight increase is achieved by an increase in muscle mass and protein content. Histological analysis of the goldfish muscle revealed that treated fish exhibited hyperplasia as compared to controls. These findings contribute to the understanding of the mechanisms that regulate growth in non-mammalian vertebrates and suggest a powerful biotechnology approach to improving fish growth in aquaculture.

Laboratory investigation of daily food intake and gut evacuation in larvae of African catfish Clarias gariepinus under different feeding conditions

Temporary accumulation of ascorbic acid 2-sulfate (AAS) was measured to estimate food intake and gut evacuation in larvae of African catfish. Fish larvae were fed decapsulated cysts of Artemia containing AAS. In a first experiment it was found that no biosynthesis of AAS occurs in the larvae of this species. In a second experiment, the gut contents of the fish larvae fed were calculated as they changed during development. In a third experiment, the gut evacuation rate of fish larvae was determined during continuous and discontinuous feeding regimes in the first five days after the start of exogenous feeding. Food consumption by catfish larvae increased from 46.5% of their body dry weight (BDW) on day 1 after the start of exogenous feeding to 53.8% BDW on day 3. Thereafter, food consumption decreased to 27.8% BDW on day 5. A similar pattern was observed for gut evacuation, which increased during the first days of exogenous feeding and decreased as fish growth continued. The rate of gut evacuation in a continuous feeding regime was significantly higher (P < 0.05) than that under discontinuous feeding. On day 1 post-hatch and 7 h after first food ingestion the fish larvae evacuated 87% of the food in continuous feeding compared with 43% under discontinuous feeding. It was found that gut emptying differs during larval development. Under continuous feeding, on days 1 and 3 post-hatch and 11 h after the first meal 90% of the food was evacuated compared with 71% evacuated on day 5. The advantages and limitations of the AAS method for estimation of food consumption by fish larvae are discussed.

Development of sensory organs in larvae of African catfish Clarias gariepinus

African catfish Clarias gariepinus hatched with morphologically immature features; however, sensory organs developed rapidly with fish growth. Although the eyes of newly hatched larvae were immature without pigment, in 2 day‐old larvae, the retina of the eyes had already developed except for the rod cells. No free neuromasts were observed in newly hatched larvae. In 1 day‐old larvae, however, free neuromasts were observed on the head and trunk. Free neuromasts increased with larval growth. Newly hatched larvae had simple round‐shaped otic vesicles; however, all sensory epithelia of the inner ear were observed until the larvae were 3 days old. Two day‐old larvae swam horizontally, had sharp teeth, commenced ingesting rotifers and also artificial feed (small‐size pellets) under both light and dark conditions; by then the larvae already had many taste buds. Three day‐old larvae showed negative phototaxis and cannibalism by eating their conspecifics. Most of the free neuromasts observed in this study had the peculiar feature of many microvilli around the sensory cells on the apical surface. Detected free neuromasts as ordinary type lateral‐line organs were not observed in previous reports in teleosts. In 10 day‐old larvae, there were two lines of free neuromasts on the flank and lower edge of the trunk; presumptive canal neuromasts were oval shaped and had begun to sink under the skin. The direction of maximum sensitivity of the neuromasts was parallel with the longitudinal axis of their elliptical apical surface.

Effect of chronic exposure to water soluble fractions of forcados crude oil on the growth and development of african catfish (&lt;i&gt;Clarias gariepinus&lt;/i&gt;) larvae

Effect of chronic exposure to water soluble fractions of forcados crude oil on the growth and development of african catfish (&lt;i&gt;Clarias gariepinus&lt;/i&gt;) larvae

STUDIES ON THE EFFECT OF NATURAL FEEDS IN DIFFERENT COMBINATIONS ON GROWTH AND SURVIVAL OF CLAR1AS GARIEPINUS LARVAE

The suitability and potential of three live food were evaluated for feeding Clarias gariepinus fry. Three-day old African catfish larvae (5-7 mm total length, 1.2-3.0 mg body weight) were stocked at a density of 100 larvae per liter in nine glass aquaria 150 X 50 X 50 cm each, representing three treatments. Each treatment was represented in three replicates). Fish were reared for 35 days on three different feeding regimes using Artemia salina, Moina macrocopa and Brachionus plicatilis as live food. Larvae of all treatments were fed on Brachionus at a density of 10 per ml in the first four days. From day 5, the three treatments were fed on Brachionus at a density of 20 per ml until day 9, for treatments 1 and 3, and day 15 for treatment 2. In all rearing aquaria, Chlorella was added at a density of 1-3 X 10 5 cells per ml to serve as food for the rotifer and maintain good quality of water. Starting at day 10, Artemia nauplii were given to larvae of the first and third treatments initially at a density of 2 per ml in addition to Brachionus. The amount of Brachionus in the two treatments was gradually reduced to 10 per ml until it was completely removed on day 17. From this day to the end of the experimental trial, fish of the first treatment were fed on Artemia only, whose density was finally increased gradually to be 10 per ml. In treatment 3, Moina macrocopa were fed to the Clarias gariepinus larvae in combination with Artemia from day 18 to day 20 and later on, Moina was fed until day 35. In treatment 2, fish continued to feed on Brachionus and feeding of fish on Artemia was delayed until day 15. Artemia nauplii were fed in combination with Brachionus until day 20, after which only Artemia was given* Delaying feeding of Artemia nauplii until day 15 (in treatment 2) on resulted in slower larvae growth rates compared with fish fed Artemia starting on day 10. Partial replacement of Artemia nauplii by Moina macrocopa starting on day 17 showed a marked growth in larval growth over the delayed

Heat treatment affects protein quality and protease activity in decapsulated cysts of Artemia when used as starter food for larvae of African catfish Clarias gariepinus (Burchell)

Decapsulated cysts of Artemia subjected to different heat treatments (40, 60, 80 and 96 °C) were fed to African catfish Clarias gariepinus larvae. Heated cysts, untreated cysts and live Artemia nauplii as control constituted the experimental diets. Protein denaturation and solubility, total alkaline protease and specific trypsin activities in the cyst diets were evaluated. The growth of catfish larvae and the proteolytic activity of larval samples during development were also determined. Heat treatment of cysts increased protein denaturation and decreased protein solubility. The protease activity in the cyst diets decreased with higher heating temperatures. The growth of catfish larvae differed according to the diet; higher fish growth was achieved with nauplii and cysts heated at 40 °C. The digestive enzyme activity in larval samples remained similar in all dietary treatments during larval development. The quality of food protein and the way this protein is processed might be more important for successful larval growth than exogenous enzyme supply.

Post-prandial protease activity in the digestive tract of African catfish Clarias gariepinus larvae fed decapsulated cysts of Artemia

The alkaline proteolytic activity in the gut of African catfish larvae was studied during short time ranges from 30 min to 4 h after ingestion of decapsulated Artemia cysts. The variation in total protease and trypsin activities during the day was monitored during starvation, after one single meal ingestion, and during continuous feeding. In starved larvae the enzymatic activity was low and did not change in time. No significant endogenous secretion of digestive enzymes was detected. The level of alkaline proteolytic activity found in starved larvae was further considered as the basal level. In larvae fed only one meal during the day, the enzyme activity significantly increased from 3 h post-feeding up to a maximum level found 12 h after feeding. In the larvae receiving a meal every 4 h, the effect of feeding on the proteolytic activity was significantly different from the one in fish fed only once a day. The total protease activity in this dietary treatment changed according to the time of feeding and fluctuated around a constant level, which was intermediate between the maximum and the basal level. No rhythmic cycle of enzyme production in the fish was observed when the proteolytic activity was studied during a cycle of 24 h. When specific trypsin activity was measured, a similar pattern was found as with the total protease. The contribution of digestive enzymes from Artemia to the total digestion of food by the catfish larvae was calculated to be less than 1% of the total amount of the proteolytic activity measured in the larval gut.

Experiments for the improved use of decapsulated Artemia cysts in intensive culture of African catfish larvae

Feeding dried and vitamin C enriched decapsulated Artemia cysts to African catfish larvae increased their growth rate significantly after 6 days over those fed only freshly decapulated cysts. Groups fed with Artemia nauplii had a significantly higher growth during the experiment, although this difference was not considerably important in practice. Tank colour had no influence on growth. Because of their lower price, the decapsulation of lower quality cysts can be an appropriate feed source in intensive cultures of African catfish larvae.

Experiments for the improved use of decapsulated Artemia cysts in intensive culture of African catfish larvae

Experiments for the improved use of decapsulated Artemia cysts in intensive culture of African catfish larvae

Use of Fresh Palm Fruit Extract as a Feed Ingredient in the Diet of Larval African Catfish, Clarias gariepinus

Three experiments were conducted. In Experiment 1, the acceptance time of pelleted diets sprayed with fresh palm fruit extract (FPFE), commercial palm oil (COM), or a control diet to African catfish, Clarias gariepinus, fingerlings was investigated. In Experiment 2, the effects of five diets on growth and survival of African catfish larvae were determined: (1) bambara nut waste-based (BW) diet; (2) bambara nut waste-based diet with 5% of diet formula of FPFE (BWP); (3) bambara nut waste-based diet with 5% of diet formula of FPFE plus 1.5% of diet formula of Spirulinapowder (BWPS); (4) fish waste-based diet (FWP); and (5) brine shrimp, Artemiasp., nauplii (control). In the BWP, BWPS, and FWP diets, fresh palm fruit extract was sprayed on the diets as a feed attractant. The Spirulinapowder was included in BWPS as an additional attractant. In Experiment 3, the effects of seven diets on growth and survival of the African catfish larvae were investigated: (1) BW; (2) BWP; (3) FWP; (4) a bambara waste-based diet with 5% COM (BWC); (5) a fish waste-based diet with 5% of formula as COM (FWC); (6) a fish waste-based diet with neither FPFE nor COM, and (7) brine shrimp nauplii (control). African catfish finger-lings accepted the pellets containing FPFE in significantly less time (P < 0.01) than they did the other pelleted diets. Inclusion of FPFE as 5% of diet formula significantly (P<0.05) improved the growth and survival of African catfish larvae fed formulated diets. Inclusion of Spirulinaat 1.5% of diet formula had no effect. Brine shrimp was nutritionally superior to the formulated diets for the African catfish larvae during the first 28 days of feeding. The results indicate that FPFE can be added to a diet for African catfish at 5% of diet formula. However, brine shrimp nauplii fed to larvae had the highest percentage survival and highest growth rates of any of the treatments.

Morphological abnormalities in african catfish ( Clarias Garieupinus) larvae exposed to malathion

Newly hatched larvae of Clarias gariepinus were exposed to malathion concentrations ranging from 0.3 mg/I to 5.0 mg/I. Their development was observed through five days posthatch, i.e. the stage in which the vertebral elements are not yet present and the notochord is the only functional body axis. A significant higher proportion of C. gariepinus larvae with deformed notochord and pericardial edema was detected at 2.5 mg/l malathion and higher. The results suggested that (1) deformed notochord was the result of the uncontrolled contractions of the body musculature due to malathion toxicity and (2) the vertebral deformities observed in the fish which have been exposed to malathion from the notochord-stage onwards were the result of a deformed notochord instead of the deformation of the vertebral elements themselves.