Channa punctata, (Bloch) (Bloch)

Choudhury, Mrinmoy, Deka, Prantik & Purkayastha, Debashree, 2024, Sub-lethal toxic effect of cadmium chloride (CdCl) on freshwater murrel Channa punctata (BLOCH), International Journal of Fisheries and Aquatic Studies 12 (1), pp. 63-66 : 64-65

Species: punctata

Materials and Methods

Collection and maintenance of test fish

Channa punctata were collected from culture pond near Serispore T.E., Hailakandi, Assam, India and brought to the laboratory in aerated containers. In the laboratory, the fishes were maintained in an aquarium with constant aeration. Fishes were fed with commercially available fish meal twice daily and were acclimatized in the aquarium for a week before the experiment.

Experimental design of fish bio-assay

For test setup, Channa punctata were kept in a tank (Group-I) with heavy metal (CdCl 2) for seven days. A control with no treatment was also run simultaneously in another tank. After seventh day, the protein content of liver was examined.

Experimental Design

The fishes were randomly divided into three groups viz., control, low dose, sub-lethal-1 (SL-I, 5ppm) and high dose sub-lethal 2(SL-II, 10ppm). They were kept in three different buckets containing 5 litres of water obtained from a pond and were labelled as control, SL-1(5ppm) and SL-2 (10ppm). The experiment was run for seven days. Fishes were taken out from all the tanks after seven days and were anesthetized and the total length and body weight were recorded. Test fishes were sacrificed and tissues like gills and liver were dissected and stored at refrigerator until further analysis.

Procedure for estimation of total protein content Estimation of protein content

Total protein content was estimated by the protocol developed by Lowry et al. (1951).

Reagents used

A. Alkaline copper Reagent.

Reagent A: 2 % Na 2 CO 3 in 0.1 N NaOH.

Reagent B: 0.5% CuSO 4. 5H 2 O in sodium potassium tartarate

The alkaline copper reagent was made by mixing 50 ml of reagent A and 1 ml of reagent B.

B. Folin Ciocalteu phenol reagent (It is commercially available which is diluted with distilled water in the ratio of 1:2

C. 0.1N NaOH

D. 70% alcohol

E. Protein (stock) Standard solution: 100mg % Bovine Serum Albumin in 0.1 N NaOH.

Working standard

10 ml of the stock was diluted to 100ml with distilled water.

The protocol

1 ml of 70% alcohol was added to the test tube after 0.2 ml of tissue homogenate was pipetted out. For ten minutes, the tubes were centrifuged at 5,000 rpm. After discarding the supernatant, 1 ml of 0.1N NaOH was used to dissolve the precipitate. 5 ml of Alkaline Copper Reagent was added, and it was left at room temperature for ten minutes. The Folin-Ciocalteu phenol reagent was added after ten minutes, and it was left in the dark for thirty minutes. The UV-Vis Spectrophotometer was used to measure the absorbance at 620 nm against a blank for the reagent. Simultaneously, a series of graded protein standard volumes were run. The data are given as milligrams of protein per gram of tissue weight that is moist.

Results and Discussion

The present study indicated that the heavy metal Cadmium Chloride (CdCl 2) has a dreadful effect on the freshwater fish Channa punctata (Bloch) (Qureshi et al, 2011) [ 3]. From the behavioural responses of fish exposed to sub-lethal concentration of the heavy metal showed that they were under stress. The increase in opercular movement and the bottom to upward movement of the fishes to overcome hypoxic condition was seen in the 5 th and 7 th day of exposure. Mucus secretion, starting of depletion of scales, skin lesions on dorsal and lateral side of the body, copious mucus, clumping of gills increased with the increasing concentration of the toxicant (Rastogi, et al., 2018) [ 5]. Colour changes of the body from blackish to pale yellowish and restlessness again confirmed the anxiety level of the fishes in the experiment ( Table 1 ). Also many visible lesions were observed near operculum, mouth, pectoral and pelvic fins and also near the caudal fins.

Also from the total protein content assay, it was observed that the gills and liver tissues when exposed to sub lethal heavy metal concentration of CdCl 2 (5ppm and 10ppm) showed gradual decline in the protein content with the increase in exposure time, which further confirms the toxicity of the heavy metal ( Table 2 ). This result indicates that the vital organs like gills and liver if affected proves lethal in survival of the fishes (Agrahari et al., 2007) [ 1].

Tables

Table 1: Morphological and behavioural changes in fishes when exposed to doses (5 ppm and 10 ppm) of CdCl2 at different exposure time

Exposure Time	Dose	Colour Changes	Opercular activity	Bottom to surface movement	Resting at Bottom	Mucous Secretion	Loss of Equilibrium
Control
Day 1	SL-I	=	*	+	=	+	+
	SL-II	*	*	+	=	+	*
Control
Day 2	SL-I	+	=	=	*	+	=
	SL-II	=	=	*	*	+	*
Day 3	Control SL-I	+	*	=	=	+	=

Table 2: Protein Content of the tissues (gill and liver) of C. punctata at different concentrations of CdCl2 after 7 days of exposure

Treatments	Duration	Gill	Liver
5 ppm CdCl2 (mg/L)	7 Days	70.3±0.25	79.3±0.20
10 ppm CdCl2 (mg/L)	7 Days	65.3±0.30	71.3±0.25
Control	7 Days	82.5±0.20	89.7±0.15