Secondary Gill Lamellae Research Articles

Histopathological alterations in the vital organs of Indian major carp Labeo rohita exposed to monosodium glutamate (MSG)

BackgroundMonosodium glutamate (MSG E621) is one of the most popular flavouring agents of modern times and is widely used in many commercially packed food and even in house hold cooking. Previous studies revealed that excessive intake of MSG in diet causes obesity, metabolic defects, nephrotoxicity, neurotoxicity and hepatotoxicity in rats, but no reports are available in the literature about the ecotoxicological assessment of MSG by using fishes as a bioindicators. Since fishes are important consumer in aquatic food chain and directly linked with human health status, the present study was aimed to investigate the impact of MSG in freshwater fish Labeo rohita by using histological biomarkers.ResultsNinety-six h-LC50 of MSG to Labeo rohita was determined (1.5 g/L), and fish exposed to sub-lethal concentration of MSG (1/10th of 96 h-LC50 concentration of MSG (150 mg/L)) showed distinguished behavioural changes like erratic movement, loss of appetite and excessive mucous secretion all over the body as an adaptive syndrome to avoid the direct exposure to MSG in the medium. Histopathological analysis clearly depicts severe damages in the vital organs of fish. In gills, epithelial necrosis, hypertrophy, hyperplasia, primary and secondary gill lamellae degeneration, oedema, fusion of adjacent secondary lamellae and rupture of gill epithelium were observed. The intensity of tissue damage was increased as the exposure period was extended. The liver displayed vein congestion, vacuole formation, degeneration in parenchymal cells and bile stagnation, whereas MSG-treated kidney tissue showed high interstitial inflammation. Among the vital organs gill and liver displayed the highest histopathological alterations.ConclusionsThe present study clearly demonstrated that MSG is toxic to fish and able to cause significant damages in the vital organs as the exposure period was extended. Since the studies on the toxicity of MSG to fish are rare, the present investigation may contribute to the scarce literature on sub-lethal toxicity of MSG to freshwater fishes.

Study on the Impact of Brick-kiln Effluent on Histomorphology of Gill and Hepatopancreas of Channa punctata Bloch. with Reference to Mobilization of Thyroid Hormones

This study deals with the effect of sublethal exposure of brick kiln effluent on lipid and protein peroxides, Aspartate Transferase (AST), Alanine Transferase (ALT) and Alkaline Phosphatase (ALP) activities and mobilization of thyroid-stimulating and thyroid hormones in gill and hepatopancreas of Channa punctata Bloch., with supporting histochemical investigations in these tissues. Acclimatized adult fishes of either sexes of three groups were reared separately in three aquaria. Aquarium-I comprised the normal control group, and the other two aquariums, i.e. Aquarium-II and Aquarium-III, comprised experimental groups of fishes exposed to 20ppm/L and 30ppm/L of brick kiln effluents, respectively. Before these, the LC50 value of the Fish for brick kiln effluent was evaluated as 55±0.50 ppm/L for 28 days. Increased lipid and protein peroxides, decreased transaminase activities with hypothyroidic conditions were observed both in gills and hepatopancreas on treatment. Significant alternations of these biochemical parameters were recorded, with some drastic changes in the histo-architecture regarding treatment issues. Gills showed hypertrophy with fusion and curving of gill lamellae. Spiked secondary gill lamellae were also observed to have several degenerative features. Decreasing hepatocytes and vacuolation at several places were recorded in hepatopancreas with necrosis of the tissues and patchy degeneration.

Phylogeny and ultrastructure of Elthusa raynaudii (Isopoda, Cymothoidae) firstly recorded from the invasive silver cheeked toadfish (Lagocephalus sceleratus) (Gmelin 1789) in eastern Mediterranean Sea coast

With the opening of the Suez Canal in 1869, many changes have occurred in the Mediterranean Sea ecosystem so became a home to many invasive Lessepsian marine species that have migrated from the Red Sea. About 500 marine species including pufferfish have immigrated and rapidly established a population in the Mediterranean Sea causing significant impact on its ecosystem and fisheries sector. The parasitic fauna of these pufferfish has scarcely been studied in the Mediterranean Sea and also in their native habitat. During this surveillance study on the invasive pufferfish species from the Egyptian Mediterranean coast, the female cymothoid isopod Elthusa raynaudii was detected from the branchial cavity and also in the buccal cavity of 23.9% of the examined Lagocephalus sceleratus. The isolated isopod species was firstly identified and described through electron microscopy and molecular phylogeny based on the sequences of mitochondrial 16S rRNA gene. Additionally, the description of eggs, embryonic stage, and manca of E. raynaudii was firstly provided. The pathological impact on the infested fish tissues was investigated and revealed curling and loss of secondary gill lamellae in addition to mucous exudates in between the gill filaments and granuloma formation in the gill arch. The study provided the first report of L. sceleratus as a new host for the isopod E. raynaudii collected from the Egyptian Mediterranean coast as a new locality record. The role of the Lessepsian invasive pufferfish in transmitting parasites to the native fish species was discussed.Graphical

Conventional Anthelmintic Concentration of Deltamethrin Immersion Disorder in the Gill Immune Responses of Crucian Carp.

Current treatment strategies for parasitic infectious diseases in crucian carp primarily rely on chemotherapy. As a commonly used antiparasitic agent, deltamethrin (DEL) may have the potential adverse effects on external mucosa of fish such as gills. In this study, 180 healthy juvenile crucian carp (Carassius auratus) (average weight: 8.8 ± 1.0 g) were randomly divided into three groups for 28 days, which were immersed in 0 μg/L, 0.3 μg/L, and 0.6 μg/L of DEL, respectively. The results of histological analysis revealed that severe hyperplasia in the secondary lamellae of gills was observed, and the number of goblet (mucus-secreting) cells increased significantly after DEL immersion. TUNEL staining indicated that the number of apoptotic cells increased in crucian carp gill. At the molecular level, the mRNA expression analysis revealed significant upregulation of apoptosis (caspase 3, caspase 8, and bax), autophagy (atg5 and beclin-1), and immune response (lzm, muc5, il-6, il-8, il-10, tnfα, ifnγ, tgfβ, tlr4, myd88, and nf-kb), whereas tight junction-related genes (occludin and claudin12) were downregulated after DEL immersion, suggesting that DEL immersion altered innate immunity responses and promoted mucus secretion. Moreover, tandem mass tag (TMT)-based proteomics revealed that a total of 428 differentially expressed proteins (DEPs) contained 341 upregulated DEPs and 87 downregulated DEPs with function annotation were identified between the control and DEL groups. Functional analyses revealed that the DEPs were enriched in apoptotic process, phagosome, and lysosome pathways. Additionally, DEL immersion also drove gill microbiota to dysbiosis and an increase in potentially harmful bacteria such as Flavobacterium. Overall, this study showed that DEL elicited shifts in the immune response and changes in the surface microbiota of fish. These results provide new perspectives on the conventional anthelmintic concentration of DEL immersion disorder of the gill immune microenvironment in crucian carp and theoretical support for future optimization of their practical application.

Gills of Molly Fish: A Potential Role in Neuro-Immune Interaction

This study identified the cellular compositions of the gills in molly fish and their role in immunity using light-, electron- microscopy, and immunohistochemistry. The molly fish gills consisted of four holobranchs spaced between five branchial slits. Each hemibranch carried many fine primary and secondary gill lamellae. The gill arch was a curved cartilaginous structure, from which radiated the bony supports of the primary lamellae. The gill arch contained the afferent and efferent brachial arteries. The gill arch was covered by epidermal tissue rich with mucous cells. The primary lamella had a central cartilaginous support and efferent and afferent arterioles and was covered with pavement cells (PVC), salt-secreting chloride cells, and pale-staining mucous cells. These chloride cells contained abundant mitochondria and tubulovesicular system and are involved in ionic transport with a potential role in detoxification. The surface of the secondary lamellae (site of gaseous exchange) consisted of overlapping or interdigitating PVC supported and separated by pillar cells. Other cells were found within the gill epithelium and interstitial connective tissues, including lymphocytes, macrophages, monocytes, telocytes, stem cells, astrocytes, and neuroepithelial cells. The immunohistochemical analysis revealed that APG-5, iNOS-2, IL-1β, NF-κB, and TGF-B showed positive immunoreactivity in macrophages. The epithelium of the primary gill lamellae contained positive-GFAP astrocytes and S100 protein—chloride cells. The stem cells expressed SOX9, myostatin, and Nrf2. Neuroendocrine cells expressed S100 protein. In conclusion, the current work suggests that the gills of molly fish are multifunctional organs and are involved in immune reactions.

Toxic effects of Parthenium hysterophorus on Muscles of freshwater fish Labeo rohita. (Vikhar)

The present study is conducted and assessed the toxicity of Parthenium hysterophorus is on locally available fresh water fish. The present study deals with to determine histological effects on fresh water fish, Labeo rohita. The fishes were collected from nearby water body and brought to the laboratory for determination of histological parameters up to 96hr. period. The muscles of fish exposed lethal concentration for different time exposure (24hrs. 48hrs. 72hrs. and 96hrs.) showed lesion, inflammation, pigment and necrosis of primary and secondary gill lamellae during low concentration while, increasing concentration for different time exposure showed necrosis, malignancy and cellular degeneration were seen at later time of exposure.

Digestive enzymes (amylase and invertase) analysis and histopathological changes in Oreochromis mossambicus treated with tricyclazole (75%) fungicide

Despite being efficient against rice blast fungal diseases when applied to agricultural fields, tricyclazole 75% fungicide has a variety of drawbacks that outweigh its benefits for the aquatic environment. Shortterm exposure to a sublethal dose of tricyclazole, fish O. mossambicus displayed altered digestive enzymes (amylase and invertase) as well as histological abnormalities in tissue organs like the skin, muscle, gills, liver, intestine, and brain tissues. The activity of amylase and invertase was found to decreasing and increasing in various concentrations. Histopathological changes on exposure to tricyclazole fungicides was found to increase in its pathological lesions of the tissue organs studied skin, muscle, gills, liver, intestine, and brain tissues of O. mossambicus noticed with necrosis, vacuolar degeneration, fusion and atrophy of the primary and secondary gill lamellae, degeneration of the cytoplasm in hepatocytes, atrophy, formation of vacuoles, rupture in blood vessels, damage in the dermis, concentrated melanophores, damaged blood vessels, and enlarged muscle fibers with increasing concentrations. Enzymatic alterations and pathological lesions in the tissue of O. mossambicus exposed to a toxicant at a sub-lethal concentration are a functional response of organisms that offers information on the nature of the toxicant. Hence, in the present study, in order to evaluate the environmental/aquatic pollution under experimental settings, an evaluation of the fish’s histological alterations and enzyme levels was carried out. In conclusion, fish are among the most susceptible aquatic species to harmful compounds; buildup of the fungicide in the fish may cause pathological problems that spread to people through the food chain.

Toxicological effects of the textile industrial effluent to an Indian freshwater fish, Clarias batrachus

In this study, the histological effects of textile industrial effluent in the freshwater fish, Clarias batrachus was studied after 10, 20, and 30 days period of exposure. The 24, 48, 72, and 96 hours LC50 values were found to be 58.476, 53.231, 47.253, and 37.429% respectively. During the experiment, the treated fishes showed abnormal behaviors like erratic swimming, hyper-excitation, rapid opercular movement, and thick mucus covering which indicated the toxicity of the effluent. The observed changes in the gills were epithelial hyperplasia with lamellar fusion, necrosis, vacuolar degeneration, and atrophy of primary and secondary gill lamellae. On the other hand, the liver showed the formation of the number of vacuoles, enlargement of nuclei of some cells, degeneration of cytoplasm in hepatocytes, atrophy, a rupture in blood vessels, and disposition of hepatic cords. The kidney also showed abnormalities like degeneration of proximal and distal convoluted tubule, vacuolation of renal interstitial tissue, necrosis, cellular hypertrophy, and granular cytoplasm.

Differential sensitivity of offspring from four species of goodeine freshwater fish to acute exposure to nitrates

Nitrate-nitrogen (NO3-N) pollution related to anthropogenic activities is increasing in freshwater ecosystems. Knowledge about NO3-N sensitivity in freshwater wild fish is needed to understand the differential tolerance between species. Goodeinae is a subfamily of 41 endemic fishes that inhabit central Mexico, with 33 species in the IUCN red list and three extinct. Distributional patterns suggest tolerant and sensitive goodeines related to the conservation gradient of freshwater ecosystems. Four species with a differential distribution and tolerance were selected to evaluate their physiological responses to NO3-N. Fish were exposed to different NO3-N concentrations for 96 h and the median lethal concentration (LC50) was determined. Swimming disorders plus gill and liver histopathological indexes were estimated and incorporated into an Integrated Biomarker Response (IBR) for each species. Skiffia lermae (LC50 = 474.332 mg/L) and Xenotoca variata (LC50 = 520.273 mg/L) were more sensitive than Goodea atripinnis (LC50 = 953.049 mg/L) and Alloophorus robustus (LC50 = 1537.13 mg/L). The typical histological damage produced by NaNO3-N exposure was fusion of secondary lamellae in gills. This was present in all species and cellular degeneration was observed at the highest concentrations. Secondary lamellae aneurysms were only observed in G. atripinnis. Liver alterations included vascular dilation in hepatic sinusoids, hyperemia and nuclear hypertrophy; higher concentrations produced hepatocyte cytoplasmic vacuolation and reduced frequency of cell nuclei. Behavioral and histopathological alterations could explain the differential species sensitivity. The results suggest that species which preserve gill function and transfer the task of detoxification to the liver might have the best chance of surviving in polluted environments. Moreover, species previously considered as tolerant may be highly susceptible to NaNO3-N exposure. Therefore, it is necessary to closely monitor NaNO3-N concentrations in freshwater ecosystems and, if possible, reduce their levels to avoid the loss of wild populations.

Acute and Chronic Toxicity Effects of the Heptachlor Pesticide on Tilapia (Oreochromis mossambicus): Impact to Behavioral Patterns and Histopathological Responses

Manimekalai, D.; Srinivasan, A.; Padmavathy, P.; Jawahar, P.; George, R., and Arisekar, U., 2022. Acute and chronic toxicity effects of the heptachlor pesticide on tilapia (Oreochromis mossambicus): Impact to behavioral patterns and histopathological responses. Journal of Coastal Research, 38(5), 999–1010. Coconut Creek (Florida), ISSN 0749-0208. Heptachlor is an organochlorine (cyclodiene) insecticide that enters water bodies and affects aquatic organisms such as fishes and shellfishes. Due to its persistent nature, it spreads from the source of its use and pollutes the area. The toxic effect of heptachlor on histopathological changes in the gill, liver, kidney, and muscles of tilapia Oreochromis mossambicus were studied. The experimental fish were exposed to four concentrations of heptachlor, viz., 0.756, 1.513, 3.025, and 6.050 ppm, for a period of 96 hours during an acute toxicity test. In the current study, the lethal concentration (LC50) value of heptachlor on tilapia at 96 hours was calculated as 4.006 ppm. Fish were subjected to three different concentrations of heptachlor (0.2003, 0.4006, and 0.8012 ppm) based on the LC50 value to study the long-term effect of heptachlor. Histological changes such as lamellar fusion, lamellar cell hyperplasia, degenerated secondary gill lamellae; Bowman's space dilation and renal tubules detachment; hepatic cells death, melanomacrophage formation, and multifocal degeneration of myocytes; and myoepithelium vacuolation were observed in the gill, kidney, liver, and muscles, respectively, during acute and chronic exposure to heptachlor. The toxicity study revealed that the heptachlor pesticide is highly toxic to tilapia even at a minimum concentration of 0.756 ppm. Hence, it is suggested that care must be taken not to allow the entry of pesticides into the habitat of fishes.

Toxic Effects of Arsenic in Commercially Important Fish Rohu Carp, Labeo rohita of Bangladesh

This study was designed to elucidate the effects of arsenic (As) on the morpho-behavior, growth development and molecular mechanisms of a commercially important fish, rohu carp, Labeo rohita, in Bangladesh. Fish fry with an average weight of 387.5 ± 169.25 mg and an average length of 3.35 ± 0.37 cm were collected from a local hatchery in Mymensingh, Bangladesh and acclimatized for a week in the Department of Fisheries, University of Dhaka before starting the exposure with arsenic. Fishes were exposed for a period of 14 days with three treatments of NaAsO2, namely treatment 1(T1)—2.5 mg/L; treatment 2 (T2)—15 mg/L; and treatment 3 (T3)—30 mg/L, along with a control (C)—0.0 mg/L, with three replicates. These concentrations were determined based on the LC50 value for 96 h measured for this experiment. This study revealed remarkable morphological abnormalities and deformities in arsenic-exposed rohu carp. In fish exposed to 30 mg/L, caudal fin erosion was a frequent deformity. There was no significant difference in RNA:DNA ratio among the treatments. The overall weight of fish was decreased as the concentration of arsenic was increased. The T3 fish had a statistically significant negative weight gain (−0.05 ± 0.07 g), but the other treatments (T1 and T2) and control fish had no significant weight gain. Different types of histopathological changes were observed in the gills and intestines of arsenic-treated fish. Necrosis and severe damages were found in the secondary lamellae of gills at the highest arsenic concentration (30 mg/L). Epithelial lifting, irregular shape and damages in the gill raker were also observed in the primary lamellae of the gills for the same treatment. In this study, the expression of heat shock protein (HSP 60) and metallothionein (MT) genes was assessed by qPCR, and these genes were upregulated in different treatments compared to controls. The findings of the present study suggest that arsenic pollution significantly changes the morphology, behavior, growth, development, histopathology and molecular mechanisms of this economically important fish, rohu carp, in Bangladesh.

Histopathological evaluation of Wallago attu (Bloch & Schneider, 1801) infested by ectoparasites

BackgroundHost-parasite interaction studies represent the dependency of the parasites on the host through various models. Gill infesting copepods, monogeneans and isopods served as excellent models to study the details of host-parasite interaction. In the present investigation, Wallago attu (Bloch & Schneider, 1801) was extensively studied for histopathological damage caused by ectoparasites like monogeneans (Thaparocleidus indicus, Thaparocleidus wallagonius and Mizelleus indicus), copepod (Ergasilus malnadensis) and an isopod (Alitropus typus) during August 2017 to February 2018. Both the control (least infested) and severely infested gills were examined through light microscope to approximate the intensity of damage caused by above ectoparasites.ResultsPathological effects of ectoparasites displayed a fusion of secondary lamella, hyperplasia of the gill filaments and the epithelial cells, propagation of bronchial tips, thinning of the central axis, deshaping, shortening and fusion of secondary gill lamellae epithelium, severe degenerative and necrotic changes in gill filaments and secondary lamellae, curling of secondary lamellae and mucous cells proliferation.ConclusionsEctoparasites cause severe damage to gills of W. attu, thereby diminishing the gill breathing capacity of the fish. Timely pathological studies can reveal the extent of damage caused by the parasites and thus various diagnostic programs and best management practices can be implemented in aquaculture for the better yield.

Eradication of Livoneca redmanii infestation in cultured Argyrosomus regius

Two Argyrosomus regius nursery ponds suffered from high mortality during the summer season of 2020. Diseased fish showed signs of respiratory distress, mainly during hot days. Physiochemical pond water parameters were normal, except dissolved oxygen was lower than the optimum level. Livoneca redmanii (Cymotidae, Isopoda) was isolated from the gill chamber of infested fish. The infestation percent was 41 and 33%, and the intensity was 1.146 and 1.06 in the first and second ponds, respectively. The diseased fingerlings were infested in the natural habitat (Mediterranean Sea) before collection for culture. L. redmanii infestation was associated with high economic losses due to direct fish mortality, reduced growth rates and lower condition factor. The molecular study confirmed the presence of L. redmanii based on the phylogenetic analysis of 16S rRNA and COI gene sequences. Infested fish gills showed massive destruction in gill filaments, sloughing and curling of secondary gill lamellae with the detachment of the cartilaginous core supporting the primary gill filaments. Deltamethrin and trichlorfon effectively eradicated L. redmanii at concentrations of 12.5 μg.l−1 and 0.5 mg.l−1, respectively. The lowest detectable deltamethrin residue in treated pond water was 2.18 μg.l−1 at 120 h, with a half-life of 47.63 h.

The effect of copper and cadmium on oxygen consumption of the juvenile common carp, Cyprinus carpio (L.)

This study was carried out on juvenile Cyprinus carpio (L.) to investigate the effects of sub-lethal concentrations of copper and cadmium (0.1, 0.25, 0.4 ppm) on the survival rate, oxygen consumption and histopathological changes in the gills of exposed fish. The results showed a decrease in survival rate with increasing concentration of each metal. Copper has the most toxic effect compared with cadmium, the survival rate has decreased from 50% to 10% for copper and from 70% to 20% for cadmium with increasing concentration for 15 days. The half lethal time (LT50) was (14 and >15) days for copper and cadmium, respectively. Oxygen consumption rate decreased with increasing concentration and there was a negative correlation between oxygen consumption and metal concentration. The exposure to each metal caused histopathological changes in the gill and resulted in separation of epithelial secondary gill lamellae, hyperplasia, fusion of secondary lamellae and necrosis.

Air sac and gill vasotocin receptor gene expression in the air-breathing catfish Heteropneustes fossilis exposed to water and air deprivation conditions.

Heteropneustes fossilis is a facultative air-breathing freshwater catfish and inhabits ponds, ditches, swamps, marshes and rivers that dry up in summers. It possesses a pair of unique tubular accessory respiratory organ (air sac), which is a modification of the gill chamber and enables it to live in water-air transition zones. In the catfish, three vasotocin (Vt) receptor gene paralogs viz., v1a1, v1a2 and v2a were identified for Vt actions. In the present study, the receptor gene transcripts were localized in the gill and air sac by in situ hybridization, and their expression levels in relation to water and air deprivation conditions were investigated by quantitative RT-PCR. The catfish were exposed to 1h and 2h in gonad inactive (resting) and gonad active (prespawning) phases. The gene paralogs showed overlapping distribution in the respiratory epithelium of primary and secondary lamellae of gills and reduced lamellae of the air sacs. In water deprivation (forced aerial mode of respiration) experiment, v2a expression showed a high fold increase in the air sac, which was unchanged or inhibited in the gill. Both v1a1 and v1a2 expression was significantly upregulated in the air sac but showed varied responses in the gill. The gill v1a1 expression was unchanged in the resting phase and modestly upregulated in the prespawning phase. The gill v1a2 expression was modestly upregulated at 1h in both phases but unchanged at 2h. In the air deprivation experiment (forced aquatic respiration), the v2a expression in the air sac was inhibited except for a mild stimulation at 1h in the prespawning phase. In the gill, the v2a expression was stimulated with a steep upregulation at 2h in the prespawning phase. Both v1a1 and v1a2 expression was significantly high in the gill but only modestly increased or unchanged in the air sac. The expression patterns point to a functional distinction; the V2 type receptor expression was higher in the air sac during forced aerial respiration, and the V1 type receptor expression was highly prominent in the gill during forced aquatic respiration. Water and air deprivation treatments caused a significant increase in plasma cortisol level, and the stimulation was higher in the water deprivation fish in the resting phase but equally prominent in the water and air deprivation groups in the prespawning phase. The results indicate that the changes in the expression patterns of Vt receptor genes may be a sequel to stress (hypoxic, metabolic and osmotic), and both Vt and cortisol may interact to counter the stress responses. This study shows that Vt has a new role in the control of air sac functions.

Histopathology and Morphometric Characters of Tilapia guineensis as Biomarker to Evaluate Level of Environmental Stress in Badagry and Ojo Creeks, Lagos, Nigeria

Forty wild adult Tilapia guineensis were sourced from Ojo and Badagry creeks between January and March 2021, to investigate its morphometric character (total length, body weight, standard length, and head depth) and tissues structure (gill, muscle and small intestine) differences. Samples were collected and analysed using standard methods. The results showed no significant difference (P<0.05) between the mean total length, body weight, standard length, and head depth of Tilapia guineensis recorded from both creeks. Length-weight relationships of T. guineensis obtained from both creeks showed negative allometry(b<3) growth pattern while its condition factor (k) value was more significant than one, which indicated that the fishes are in good condition. Muscle of T.guineensis from Ojo creek showed a severe lesion of muscle bundle, degeneration of muscular bundle and shortening of bundles. Similarly, the gills structure of T. guineensis from Ojo creek showed severe degeneration, hyperplasia of secondary gill lamellae, and curling of secondary lamellae with unclear water channels. It is also characterized by hypertrophy of lamellae, and there is evidence of partial fusion of lamellae and dilation of gill filament. The observation of none lesion or degenerated tissues of T. guineensis in Badagry creek could suggest that Ojo creek is more subjected to effluents or other environmental stressors than Badagry creek. In conclusion, T. guineensis from Badagry creek is less affected by any environmental contaminants than T. guineensis from Ojo creek. Therefore, a collective effort towards ensuring reduction in direct discharge of untreated effluent or avoidance of another unhygienic usage of the creeks is very pertinent.

Immuno-pathological changes in Indian catfish Clarias magur (Hamilton, 1822) upon experimental challenge with Aeromonas hydropila

Motile Aeromonas septicaemia (MAS), caused by Aeromonas hydrophila, is one of the most significant problem among the bacterial diseases responsible for causing mortality in catfishes. The objective this study was to understand the modulation of innate immune parameters and histopathological alteration in Indian catfish Clarias magur (Hamilton, 1822), following intraperitoneal injection with A. hydrophila. At 3 to 8 h post-infection (hpi), respiratory burst activity, myeloperoxidase, protease, total anti-protease and α2 macroglobulin increased significantly (p<0.05) indicating immune response of host against pathogen invasion at an early stage of infection. The total protein, albumin, albumin/globulin ratio and bactericidal activity were significantly decreased indicating the response of pathogen to suppress host immune response to establish infection. Serum bactericidal activity, bacterial agglutination titre and lysozyme activity increased significantly at 24 hpi. Histopathological examination of infected fish revealed the accumulation of melanomacrophage centres, congestion, hepatocyte degeneration and vacuolated hepatocytes of liver; hyaline droplet accumulation, lymphocytes infiltration and diffuse necrosis of renal tubule in kidney; unilateral fusion of secondary gill lamellae, leukocytic infiltration as well as dilated central venous sinus in gills. Knowledge regarding the immune response in magur could be useful for developing strategies for improving disease resistance against A. hydrophila infection. Keywords: Aeromonas hydrophila, Histopathological alterations, Indian catfish, Innate immune parameters, Intraperitoneal challenge

Toxicological impact of Zinc Nano Particles on tilapia fish (Oreochromis mossambicus)

In this study we investigated the acute toxicity of Zinc Nano Particles (ZnO NPs) and bulk ZnO on tilapia fish (Oreochromis mossambicus). Oreochromis mossambicus was exposed to the different concentration of ZnO NPs, ZnO and mixed solution of both ZnO NPs and ZnO (20 ppb, 20 ppb, 20 ppb) respectively for 96 h. A very high impact was recorded in hematological parameters which shows significant increased (p < 0.05) in count of white WBCs and platelets in all the experimental groups compared tocontrol group. The count of RBCs, Hb, hematocrit and MCHC were significantly decreased. The remarkable changes which were recorded during this study were histopathological lesions in the gills of exposed fish including, disorganization of gill lamella, cartilaginous core disruption, lifting of epithelium, loss of secondary gill lamellae, blood congestion, fusion of secondary gills lamellae, shortening of secondary gills lamellae, atrophy and curling. Disassembly were seen in plasma membrane of liver along with blood congestion, pyknosis, necrosis, hyperplasia and formation of vacuoles. Intestinal alterations which were observed include shortening of villi, necrosis, detachment and fusion of villi and extreme goblet cells formation. It is concluded from the present study that high level of ZnO NPs, ZnO and mixed solution has a strong tendency to alter hematological parameters, histological architecture, therefore, the indiscriminate use of ZnO NPs and ZnO can subsidize in reducing the population of Oreochromis mossambicus in natural water bodies.

Characterization of Flavobacterium columnare from farmed infected rainbow trout, Oncorhynchus mykiss (Walbaum, 1792) of Central Indian Himalayan region, India

Flavobacterium columnare, the causative agent in columnaris disease, leads to the mass mortality in many cultured freshwater fish species globally. Flavobacterium columnare (n = 7) was isolated from the gill lesions of farmed rainbow trout, Oncorhynchus mykiss in Central Indian Himalayan region. The bacterium was identified by colony characteristics, partial amplification of 16S rRNA gene and phylogenetic analysis. The partially amplified 16S rRNA gene (~1400 bp) was sequenced and matched with (>99%) the sequences of other F. columnare strains in the GeneBank and designated as F. columnare, BRTAGILLFC 01. From phylogenetic analysis of 16S rRNA sequences of F. columnare, the isolate was assigned to genetic group 2. The in-vitro assays for the virulence characteristics of the F. columnare BRTAGILLFC 01 revealed its ability for hemolysis, biofilm formation, protease production and capsule formation. In transmission electron microscopy (TEM), the negatively stained bacterial samples revealed the presence of capsular structure and large numbers of fimbriae. The experimental infection of rainbow trout fingerling with F. columnare BRTAGILLFC 01 at 1.5 × 108 CFU mL−1 reproduced the disease and led to cumulative mortality of 60% within 30 days. The post challenge observations illustrated swelling and hemorrhage in gill, abnormal behavior and pigmentation, decreased feeding and increased mortality in infected rainbow trout fingerlings. The histopathology of trout depicted severe degenerative changes in gill such as necrosis, fusion of secondary gill lamellae, hypertrophy, hyperplasia and epithelial lifting. The other organs revealed cellular hypertrophy, congestion and vacuolation in liver, renal corpuscle dilation and tubular necrosis in kidney and melanomachrophage aggregation in spleen. Among all therapeutic antibiotics, the bacterium was susceptible to oxytetracycline, erythromycin, ampicillin and florfenicol at the lower concentrations. In conclusion, the study confirms the first report of F. columnare infection in gill tissue of farmed rainbow trout in Central Himalayan region of India.

Histopathological study of Channa gachua exposed to sublethal concentration of malathion

This is well established fact that the exposure of pesticide leads to the significant physiological and histological changes in aquatic fauna. Therefore, ecotoxicology and histopathology have become the important areas of research for scientists, now a days. In order to investigate histopathological effects of synthetic pyrethroids, Skin, Liver, kidney, gills, and spleen of Channa gachua were examined after exposure to sublethal and acute concentration of melathion (0.8 and 1.6 mg/L) for 20 days. Fishes showed degenerative, necrotic changes and congestion of blood vessels in gill filament. Severe degeneration in secondary gill lamellae, separation of gill filament from basement membrane, proliferation of mucus cells and atrophy of gill filament were seen. Hyperplasia was found as an increased number of epithelial cells at the distal or basal portions of kidney. Few nephrons had obstructed glomerular capillary and detachment of the tubular epithelium with the surrounding tissue. Necrosis was present in hematopoietic tissue, glomerular cells, and tubular cells. Melanomacrophage centers (MMC) were scattered throughout liver and spleen. Exudates and necrosis in the splenic white pulp were observed. The liver had a low number of necrotic hepatocytes and enlarged hepatic perisinusoidal areas containing eosinophilic material. Vacuolar dystrophy of hepatocytes and hypertrophy of hepatocytes were also observed. Fish showed serious skin lesions but did not show any behavioural abnormality as compared to controlled group. Their histological recovery was also examined for next 30 days. These changes which observed during exposure were reversed after 30 days of recovery period.