Secondary Gill Lamellae Research Articles

Morphological and attachment changes of Lamellodiscus theroni (Monogenea: Diplectanidae) during its post-larval development on fish.

Species of the genus Lamellodiscus Johnston et Tiegs, 1922 (Monogenea: Diplectanidae) are characterised by a complex haptor bearing many different attachment elements: two pairs of main hooks joined by medial bars, 14 peripheral marginal hooks and one or two lamellodiscs, formed by several overlapping sclerotised plates (lamellae). These haptoral structures appear gradually during parasite development and, therefore, attachment strategies vary with developmental stage. The main aim of this work was to study the developmental changes of Lamellodiscus theroni Amine, Euzet et Kechemir-Issad, 2007 under experimental conditions, with special attention to the gradual variations in attachment strategies and the pathological implications. Throughout the gradual development of the sclerotised structures, six developmental phases were distinguished in L. theroni: phase I, with only 14 peripheral marginal hooks; phase II, with main hooks (ventral and dorsal) formed; phase III, with ventral bar formed; phase IV, with dorsal bars formed; phase V, with dorsal and ventral lamellodiscs formed; and phase VI, adult stage with male copulatory organ formed. During development, parasites attach to different parts of the first and secondary gill lamellae and the mode of attachment changes from unspecific stage, i.e. based on piercing any flat gill tissue in the early stages, through an intermediate stage when ventral and dorsal main hooks are completely functional and parasites become restricted to the interlamellar space, and finally to the definitive adult attachment stage when lamellodiscs are fully developed. The timing of key events in the development of L. theroni was used to establish adequate intervals for anthelmintic drug administration.

Effects of waterborne iron on fry ofCatla catla(Ham.),Labeo rohita(Ham.) andCirrhinus mrigala(Ham.)

Effects of waterborne iron on Indian major carps (Catla catla, Labeo rohita and Cirrhinus mrigala) fry was evaluated in the present study. In short-term definitive test a concentration series of 8, 10, 12, 14, 16, 18, 20, 22 and 24 mg l−1 of iron were selected. In long-term partial life cycle test 1.0, 2.0, 3.0, 5.0 and 6.0 mg l−1 of iron were selected to observe the behavioural changes, feeding rate, growth rate and bioaccumulation of iron in different organs of fishes. Supplement of iron was done by adding FeSO4 to get the test concentrations. Rohu showed highest tolerance to iron toxicity. The lowest 96 h LC50 value was found for mrigal as 11.21 ± 0.53 mg l−1 whereas the highest was observed in rohu as 16.75 ± 0.96 mg l−1. Among the organs tested, comparatively gill showed higher iron accumulation and muscle showed the lowest. However, rate of change of iron accumulation in gills w.r.t toxicant concentration was lowest as compared to other tissues. Histopathological study of gill showed the evidence of iron accumulation and erosion of secondary gill lamellae. In long-term partial life cycle test reduction in feeding rate, behavioural changes and reduced weight gain was observed. Mrigal showed highest accumulation and catla showed the lowest.

Association between swimming performance, cardiorespiratory morphometry, and thermal tolerance in Atlantic salmon (Salmo salar L.)

This experiment tested the hypothesis that swimming performance in Atlantic salmon (Salmo salar) parr is connected to cardiorespiratory performance and morphology, as well as maximum heart rate (fHmax) related measures of thermal tolerance. Moreover, it was hypothesized that the cardiorespiratory differences between poor and strong swimmers will be retained in a later life stage, i.e., 15 weeks post-smoltification and seawater transfer. This experiment screened a population of 3,200 parr (11.2 ± 0.25 g) for their swimming performance, classifying them as poor and good swimmers based on their critical swimming speeds (4.4±0.1 body length s-1 and >6.8±0.1 body length s-1, respectively). Compared with poor performing parr, good swimmers had a significantly thicker compact myocardium (by 23.7%) and taller gill secondary lamellae (by 16.2%). In contrast, there was no significant difference in maximum oxygen consumption between the two groups as assessed using a ‘chase’ protocol, and the relationship between heart rate specific measures of thermal tolerance and swim performance was variable. For example, three measures did not differ between the two groups, whereas the Arrhenius breakpoint temperature for fHmax and fHmax were higher and lower, respectively, in the poor swimmers. Importantly, the identified morphological and fHmax differences at the parr stage persisted after 15 weeks of common garden rearing in seawater, and they were associated with an increase in relative ventricular mass and a small, but significant, improvement in growth rate. Therefore, it seems that an early assessment of swimming performance can effectively screen for morphological capacities related to oxygen supply and growth rate, but less so for heart rate related measures of thermal tolerance.

TOXICITY OF TWO BIOPESTICIDAL PLANTS AQUEOUS LEAF EXTRACTS TOOREOCHROMIS MOSSAMBICUS –HISTOPATHOLOGY OF GILL, LIVER AND INTESTINE

ABSTRACT An investigation on the toxicity of two biopesticidal plants – Carica papaya and Nerium oleander aqueous leaf extracts to Oreochromis mossambicus. The LC50 value of Carica papaya and Neriumoleander aqueous leaf extracts was 700 ppm and 400 ppm respectively. The sub lethal concentration for C. papaya and N. oleander was 70ppm and 40ppm respectively. The fishes wereexposed to the sub lethal concentration for a period of 14 days. At the end of 7th and 14th day thefishes were dissected and the gill, liver and intestine were removed from exposed and control groupfishes. The tissues were processed and sectioned at 4µm and then were stained with Haematoxylin- Eosin. The observation of the slides was done under light microscope at 40x magnification andphotographed. The exposed group showed histopathological changes in the tissues, such as: shrunken and narrow secondary gill lamellae, mild to moderate infiltration of inflammatory cells inthe primary and secondary gill lamellae, vacuolar degeneration of epithelial cells of intestinal villi, massive infiltration of inflammatory cells throughout the base of the villi and disruption of epithelial cells. The liver showed swollen nucleus, hydrated and vacuolar degeneration of hepatocytes and mild pockets of infiltration of inflammatory cells.

Histopathological and haematological response of male rainbow trout (Oncorhynchus mykiss) subjected to butachlor

This study was aimed at assessing the histopathological and haematological effects of a widely used herbicide on rice paddy fields, i.e. butachlor, on rainbow trout. Fish were exposed to butachlor at a concentration of 0.39 mg/l, for a period of 10 days. Haematologically, fish showed a significant decrease in erythrocyte count, haemoglobin, white blood cells and lymphocytes and a significant increase in neutrophils compared to controls (P < 0.05). Histopathological observations of prepared sections of the treatment group also revealed pathological lesions of varying severity in studied organs, including liver (hyperaemia and haemorrhage, bile duct hyperplasia, dilated sinuses, interstitial oedema, monocellular necrosis, nuclear degeneration and hypertrophy in hepatocytes), gills (hyperplasia and hyperplasia of lamellar epithelium, fusion of lamellae, rod-like structures of secondary gill lamellae, cystic-like lesions) and kidneys (vacuolar degeneration of tubular epithelium, desquamation of epithelium and necrosis of tubular epithelium). It is concluded that butachlor caused changes in certain haematological parameters and histopathologically, exerted destructive effects on the gills, liver and kidneys of rainbow trout.  

Cellular metabolic, stress, and histological response on exposure to acute toxicity of endosulfan in tilapia (Oreochromis mossambicus).

Endosulfan is one of the most hazardous organochlorines pesticides responsible for environmental pollution, as it is very persistent and shows bio-magnification. This study evaluated the impact of acute endosulfan toxicity on metabolic enzymes, lysozyme activities, heat shock protein (Hsp) 70 expression, and histopathology in Tilapia (Oreochromis mossambicus). Among the indicators that were induced in dose dependent manner were the enzymes of amino acid metabolism (serum alanine aminotransferase and aspartate aminotransferase), carbohydrate metabolism (serum lactate dehydrogenase), pentose phosphate pathway (Glucose-6-phosphate dehydrogenase) as well as lysozyme and Hsp70 in liver and gill, while liver and gill Isocitrate dehydrogenase (TCA cycle enzyme) and marker of general energetics (Total adenosine triphosphatase) were inhibited. Histopathological alterations in gill were clubbing of secondary gill lamellae, marked hyperplasia, complete loss of secondary lamellae and atrophy of primary gill filaments. Whereas in liver, swollen hepatocyte, and degeneration with loss of cellular boundaries were distinctly noticed. Overall results clearly demonstrated the unbalanced metabolism and damage of the vital organs like liver and gill in Tilapia due to acute endosulfan exposure.

Effects of Dimethoate (EC 30%) on Gill Morphology, Oxygen Consumption and Serum Electrolyte Levels of Common Carp, Cyprinus Carpio (Linn)

Synthetic pesticides are an important group of aquatic pollutants affecting health of fishes. This study is an attempt to assess the sub lethal effects of dimethoate, an organophosphate insecticide on gill morphology, ventilation rate, oxygen consumption and electrolyte levels of common carp (C. carpio). Healthy juvenile fishes were exposed to a sub lethal concentration of 0.96 mg/l (60% of 96 h LC50) of dimethoate; and at 24, 48 and 96 h exposure blood and gill tissues were collected, oxygen consumption and ventilation rate was determined. The changes in the gills of exposed fish were characterized by epithelial hyperplasia, lifting and degeneration of respiratory epithelium, lamellar bending and curling, fusion and disintegration of secondary gill lamellae. The degree of damage showed direct correlation with the duration of exposure. The electrolyte levels also fluctuated, levels of calcium decreased and phosphate levels increased during the exposure. Oxygen consumption and ventilation rate showed significant decrease at all exposure durations. The study demonstrates high sensitivity of fish gills to dimethoate, at short term and sub lethal exposure.

Outbreak of a novel disease associated with Vibrio mimicus infection in fresh water cultured yellow catfish, Pelteobagrus fulvidraco

An outbreak of a novel disease characterized by serious and regularly shaped ulcers in the skin was recorded in cultured yellow catfish (Pelteobagrus fulyidraco) in Guangdong and Guangxi provinces of South-China in 2011. Several bacterial strains that exhibited the same phenotypic traits and biochemical characteristics were isolated from the lesions of diseased fish. One bacterial isolate named XQ was identified as Vibrio mimicus according to biochemical tests and phylogenetic analysis derived from 16S rDNA, rpoA, recA and pyrH gene sequencing. In challenge trials, the bacterial isolate XQ exhibited high virulence in yellow catfish with an intra-peritoneal LD50 value of 3.39 x 10(6) CFU per fish. In addition, skin ulcers occurred in all challenged fish groups whether they were treated with the bacterial isolate XQ by intraperitoneal injection, oral delivery or bath exposure, suggesting that the V. mimicus is the etiological agent of the enzootic and could infect the host fish via more than one route. Furthermore, histopathology of diseased fish infected with V. mimicus showed destruction of the epidermis and fibrinoid necrosis in skin; renal tubular epithelial cell necrosis in kidney; hepatocyte swelling and serious hemorrhage in the liver; macrophage aggregations and necrosis of the lymphoid tissue in spleen; severe necrosis and shedding of the intestinal mucosal villi in intestines; and, edema and exfoliation of epithelial cells in gill secondary lamellae. (C) 2014 Elsevier B.V. All rights reserved.

3D Visualization of the Initial Yersinia ruckeri Infection Route in Rainbow Trout (Oncorhynchus mykiss) by Optical Projection Tomography

Despite the fact that enteric redmouth disease (ERM) in farmed rainbow trout is one of the most devastating disease problems, little is known about the initial route of infection and pathogenicity of the aetiological agent, Yersinia ruckeri. In order to determine the initially infected organs, optical projection tomography (OPT), a novel three-dimensional (3D) bio-imaging technique, was applied. OPT not only enables the visualization of Y. ruckeri on mucosal surfaces but also the 3D spatial distribution in whole organs, without sectioning. Rainbow trout were infected by bath challenge exposure to 1×108 CFU/ml of Y. ruckeri O1 for 1 hour. Three fish were sampled for OPT and immunohistochemistry (IHC) 1, 10 and 30 minutes, 1, 3, 6, 12 and 24 hours, as well as 2, 3, 7 and 21 days after the start of the infection period. Y. ruckeri was re-isolated from the blood of infected fish as early as 1 minute post infection. Both OPT and IHC analysis confirmed that the secondary gill lamellae were the only tissues infected at this early time point, indicating that Y. ruckeri initially infects gill epithelial cells. The experimentally induced infection caused septicemia, and Y. ruckeri was found in all examined organs 7 days post infection including the brain, which correlated with the peak in mortality. To the best of our knowledge this is the first description of Y. ruckeri infection in the brain, which is likely to cause encephalitis. This in part could explain the lethality of ERM in rainbow trout. Using OPT scanning it was possible to visualize the initial route of entry, as well as secondary infection routes along with the proliferation and spread of Y. ruckeri, ultimately causing significant mortality in the exposed rainbow trout. These results demonstrate that OPT is a state-of-the-art technique capable of visualizing pathogenesis at high resolution.

Short and long‐term strategies to facilitate aerial exposure in a galaxiid

This study investigated two potential strategies to survive short and longer-term aerial exposure in a galaxiid. This scaleless fish possesses cutaneous pores that dilated in the short-term (15 min-3 h) but contracted over longer periods (15 h) out of water, suggesting that these organs are used to cope with shorter durations of air exposure. Pores on the abdominal surface showed the greatest variation while those on the operculum surface hardly changed. Conversely, thickening of the epithelial layer of secondary gill lamellae showed a slower increase but persisted in an approximately linear fashion over the duration of this study, indicating that this is a strategy that facilitates longer-term aerial exposure. Thus, this species has the capacity to accommodate both short and long-term exposure to air.

Some Biochemical and Immunological Changes Associated with Use of Garlic Extract (Allicin) in Combating Some Fish Pathogens

We studied the effects of garlic (allicin) which used as immunostimulant on some physiological, biochemical parameters, survival rate, histopathological studies and bacteriological characteristics of sea bream. Fish (50 ± 5 g/fish) were assigned to 3 treatments, with three replicates each. Treatment groups had a different level of allicin (Garlen®), (1 and 2 gm. /kg feed) added to their diets; the control group diet was free from garlic. Diets also contained 25% crude protein (CP) and were administered at a rate of 3% live body weight twice daily for 8 weeks. At the end of 7th week ten fish from each treatment group and from the control were artificially infected by intra peritoneal injection with 0.2 ml of culture suspension of pathogenic Vibrio alginolyticus previously adjusted to 104.Results showed that the differential leucocytic count, phagocytic activity, phagocytic index, serum lysozomal and bactericidal activity increased significantly with increasing levels of allicin. Plasma Cortisol level decreased significantly with increasing levels of allicin. Total protein and globulin were also increased significantly in the treated groups than the control group. All bacterial counts decreased significantly in treated groups than the control in all weeks. Treated groups had lower mortality rate than the control group during the challenge test. Histopathological studies of control group revealed congestion in blood vessel of gills, liver, spleen and kidney with, hyperplasia of epithelial cells between secondary lamellae led to fusion, edema and lifting of the lamellar epithelium of secondary lamellae in gills, vacuolar degeneration of hepatocytes, with infiltration by monocytes in liver, dilation of blood vessel, severe depletion of white bulb ,edema, and hyperactivation of melanomacrophage center in spleen ,necrosis of renal tubules epithelium, and inter renal haemopoietic tissues with atrophied glomerular tuft and widening of bowman capsules in kidney. Moderate to minimal histopathological changes appeared in all organs in groups received (Garlen®) according to its dose.

Clinical and Histopathological Study of Important Air-Breathing Fishes

A study was conducted to know the health and disease problems of three important air-breathing fishes viz. Shing (Heteropneustes fossilis), Magur (Clarias batrachus) and Thai Koi (Anabas testudineus) through clinical and histopathological technique from June 2007 to March 2008 collected from selected farms and from local markets. Generally, during December and January, acute pathologies were recorded. Clinical signs of Shing included haemorrhage, extended belly and ulceration. Histopathologically, partly missing and splitted epidermis and dermis, necrotic, vacuoled and ruptured myotomes of muscle with fungal granuloma were observed. Major gill pathologies included partly missing and highly hypertrophied, haemorrhagic gill lamellae, presence of monogenetic trematode and pyknotic cells. In liver, haemorrhagic areas, necrotic, vacuoled, hyperplasid hepatocytes, cell debris, pyknotic nuclei and plenty of inflammatory cells were evident. Haemorrhages, vacuolation, necrosis, missing and ruptured kidney tubules and pyknotic nuclei were the major pathologies of kidney. Clinically, dark red lesion, haemorrhage, necrosis and ulcer in body surface were seen in Magur. Histopathologically observed pathologies in Magur were almost similar to that of Shing. Clinical signs of Thai Koi included discoloration, loss of scales and fins, abnormal caudal fin, haemorrhage in gill and ulcer. Marked histopathology in the skin and muscle were observed such as totally lost epidermis, dermis separated from muscle, severely ruptured, degenerated and missing of myotomes in many places. In gills, hypertrophy, hyperplasia, telangiectasis, clubbing, haemorrhage and massive necrosis in both primary and secondary gill lamellae were found. Pathologies observed in liver and kidney were most alike to that of Shing. In the months of February and March, all the investigated organs of the three fish species were at a healing stage.DOI: http://dx.doi.org/10.3329/pa.v19i1.17109 Progress. Agric. 19(1): 69 - 78, 2008

Differentiation and development of the gill in <I>Trachinotus ovatus</I> during larval and juvenile development

We documented the differentiation and development of the gill and the relationship between gill struc-ture and function in Trachinotus ovatus using histology and scanning electron microscopy.Development of the gill was divided into three stages in the larvae and juveniles.Stage I included organ-primordium formation between 0–3 days after hatching(DAH).During this stage,gill-primordia were present but undifferentiated,there were no gill rakers,and respiration occurred primarily via the finfold,skin,and the microvascular surface of the yolk-sac.Stage II occurred between 4–17 DAH and was characterized by differentiation and development of gill filaments.Gill arches,filaments,secondary gill lamella,and gill rakers developed gradually and the basic structure and morphology of the gill were established.Stage III was initiated at 18 DAH,at which time the gill organs(e.g.,arches,filaments,secondary gill lamella,and rakers) resembled the adult in terms of morphology and function.The total number of gill filaments increased with the increasing body weight and body length in larvae and juve-niles.Thus,the single secondary gill lamella area and total respiratory area also increased with an increase of body weight.The differentiation and development of the gill was in accordance with growth,development,and function in larval and juvenile T.ovatus.

Histopathological changes induced by paraquat on some tissues of gourami fish (Trichogaster trichopterus)

Paraquat is a contact and non-selective herbicide which is used for controlling a wide range of terrestrial weeds and aquatic plants. A long-term contact with this xenobiotic can potentially lead to injuries in fishes as live non-target organisms. Therefore, the current study aimed to investigate the effect of sub-lethal toxicity of paraquat on the pathology of gill, liver, and spleen tissues in gourami fish (Trichogaster trichopterus). In this study, sub-lethal concentration is determined based on lethal concentration (LC50 : 7.16±0.69, 4.46±0.43, 2.19±0.27 and 1.41±0.17 mg/l of paraquat within 24, 48, 72 and 96 hours, respectively). The experiment was done with four varied concentrations of paraquat (0.0, 0.07, 0.15, and 0.3 mg/l equal 0.0%, 5%, 10% and 20% of nominal value of 96 h LC50) during 3 weeks. The exposed ?sh displayed erratic swimming and became lethargic. The changes in gills were characterized by hypertrophy, epithelial, epithelium increase of gill filament, edema and secondary gill lamella. The liver showed hypotrophy of liver cells, cloudy swelling and formation of cytoplasmic vacuoles in the liver tissue of fish treated with 0.15 and 0.3 mg/l concentrations of paraquat. Disorder in the ellipsoid cell and hemosiderin accumulation in melano-macrophage centers was observed in the spleen tissue of fish exposed to 0.15 and 0.3 mg/l of paraquat.

양식 동남아산 뱀장어, Anguilla bicolor의 Anguillid herpesvirus-1 (AngHV-1) 감염증

양식 동남아산 뱀장어 Anguilla bicolor에 아가미의 출혈 및 간장의 충혈을 특징으로 하는 질병의 원인을 조사한 결과 Anguillid herpesvirus (AngHV-1) 의 감염이 확인되었다. 병어는 병리조직학적으로 아가미의 상피세포의 증생과 모세혈관의 출혈, 간장의 공포변성 및 중심정맥의 충혈이 관찰되었다. 병어를 <TEX>$35^{\circ}C$</TEX>에 10일간 승온 사육한 결과 아가미의 형태가 건강어의 아가미와 유사한 형태로 회복되었으며, 폐사율도 10%로 승온 처리가 폐사율 감소에 효과적인 것으로 나타났다. Diseased eel (Anguilla bicolor) displayed severe hemorrhages in the gills, and congestion and swelling in the liver. During the epizootic, the water temperature was <TEX>$28^{\circ}C$</TEX> and the morality rates were about 5%. No parasites were found on the gills and skin. Bacteria were not cultured from any internal organs using TSA or SS agar at <TEX>$28^{\circ}C$</TEX> for 48 hrs. Histopathologically, the gills showed epithelial hyperplasia in the base of secondary gill lamellae and hemorrhages in the capillaries. Some cells in the proliferated interlamellar epithelia exhibited marginal hyperchromatosis. And severe vacuolated changes in the parenchymal cells and congestion in the central veins were observed in the liver. The specific amplicon (396 bp) was detected from gills and opercula of affected eel PCR using Anguillid herpesvirus-1 (AngHV-1) -specific primer sets HVAPOLVPSD (5-'GTG TCG GGC TTT GTG GTG C-3') and HVAPOLOOSN (5'-CAT GCC GGG AGT CTT TTT GAT-3'). Sequencing analysis of the amplicon demonstrated that this gene was 99% homologous to the AngHV-1 sequence deposited in GenBank. This is the first report of AngHV-1 outbreak in the farmed shortfin eels (A. bicolor) in Korea. When diseased fish were maintained for 10 days at water temperatures of <TEX>$32^{\circ}C$</TEX> and <TEX>$35^{\circ}C$</TEX>, the cumulative mortalities were 100% and 10%, respectively. Even though the AngHV-1 genome in the gills from the eel kept at <TEX>$35^{\circ}C$</TEX> was detected using PCR, the structure of gill filaments was similar with that of normal fish. Increasing the water temperature to <TEX>$35^{\circ}C$</TEX> was an effective way to diminish the mortality of AngHV-1 affected eel.

Chlorpyrifos-induced Histopathological Alterations in Duttaphrynus melanostictus (Schneider 1799) Tadpoles: Evidence from Empirical Trials

This paper reports the histopathological responses of the gill, liver and tail muscle tissues in tadpoles of the Asian Common Toad Duttaphrynus melanostictus (Schneider, 1799) exposed to chlorpyrifos a common organophosphorus pesticide. Tadpoles of Gosner stages 24-26 were continuously exposed to low, mid and high (500, 1000 and 1500 µgl–1) concentrations of chlorpyrifos for two weeks. Histological alterations in the tissues of the surviving larvae were microscopically examined both at the end of the exposure period and after a week following the final exposure. Several histological alterations were noted in the gills, liver and tail muscles of the larvae exposed to 1500 µgl–1 of chlorpyrifos. The gills of exposed larvae showed architectural distortion resulting from reduced primary and secondary gill lamellae and blood vessels, and alterations in the gill epithelium. In the liver sinusoidal congestion and dilation, cytoplasmic vacuolation and changes in hepatocytes such as hyperchromatic nuclei and nuclear fragmentation were observed. The tail muscle tissue suffered from severe atrophy and myotomal disintegration. Although histological alterations in the gill and liver tissues were noted only at the high concentration, changes in the muscle tissue i.e. muscle degeneration and atrophy, were apparent at both low and mid concentrations. The degree of damage in surviving larvae in a week following the final exposure was lower than that observed during the exposure, probably indicating recovery or resistance. The findings of the present study emphasize the need to investigate possible sublethal damage induced by pesticides in amphibians inhabiting agricultural habitats.

Carbaryl exposure and recovery modify the interrenal and thyroidal activities and the mitochondria-rich cell function in the climbing perch Anabas testudineus Bloch

We examined the effects of carbaryl (1-naphthyl methylcarbamate; sevin), a carbamate pesticide, on interrenal and thyroid activities and mitochondrial rich (MR) cell function in climbing perch to understand the physiological basis of toxicity acclimation in this fish to the chemical stressor. Carbaryl exposure (5–20mgL−1) for 48h increased cortisol and glucose, but decreased the T3 level without affecting T4 concentration in the plasma. These responses of the carbaryl-exposed fish were nullified and a rise in plasma T4 occurred in these fish when they were kept for 96h recovery in clean water. A tight plasma mineral control was indicated in the carbaryl-exposed fish as reflected by the unchanged plasma Na, K, Ca and inorganic phosphate levels. The ouabain-sensitive Na+, K+-ATPase activity showed an increase in the gills but the intestinal and renal tissues showed little response to carbaryl treatment. However, substantial increases in the intestinal and renal Na+, K+-ATPase activities occurred in the recovery fish. The MR cells in the branchial epithelia showed a strong Na+, K+-ATPase immunoreactivity to carbaryl treatment indicating an activated MR cell function. The numerical MR cell density remained unchanged, but stretching of secondary gill lamellae as part of gill remodeling occurred during carbaryl exposure. The increased surface of these lamellae with abundant MR cells as a result of its migration into the lamellar surface points to marked structural and functional modifications of these cells in the carbaryl-treated fish which is likely to a target for carbaryl action. The rise in plasma T4 and the restoration of normal branchial epithelia in the recovery fish indicate a thyroidal involvement in the recovery response and survival. Our data thus provide evidence that carbaryl exposure and its recovery evoke interrenal and thyroid disruption in this fish leading to a modified osmotic response including an altered MR cell function.

Sublethal Effect of Copper Toxicity Against Histopathological Changes in the Spiny Lobster, Panulirus homarus (Linnaeus, 1758)

The tissue damage induced by various organic pollutants in aquatic animals is well documented, but there is a dearth of information relating to the histological alterations induced by copper in the spiny lobster. In the present study, intermoult juveniles of the spiny lobster Panulirus homarus (average weight 150-200 g) were exposed to two sublethal concentrations of the copper (9.55 and 19.1 μg/l) for a period of 28 days. The muscle, hepatopancreas, midgut, gills, thoracic ganglion and heart of the lobsters were then dissected out and processed for light microscopic studies. Exposure to copper was found to result in several alterations in the histoarchitecture of the muscle, hepatopancreas, midgut, gills, thoracic ganglion and heart of P. homarus. The alterations included disruption and congestion of muscle bundle in muscle tissue; blackened haemocytes; distended lumen and F cell; necrosis of the tubules of the hepatopancreas; disarrangement of circular muscle of the midgut; accumulation of haemocytes in the haemocoelic space; swelling and fusion of lamellae; abnormal gill tips; hyperplastic, necrotic, and blackened secondary gill lamellae of the gills; damaged neurosecretory cell and sensory and motor fibre; necrotic of the thoracic ganglion; dispersedly arranged muscle bands; clumped satellite cells and nucleus of the heart. The results obtained suggest that the muscle, hepatopancreas, midgut, gills, thoracic ganglion and heart of lobsters exposed to copper were structurally altered. Such alterations could affect vital physiological functions, such as absorption, storage and secretion of the hepatopancreas, digestion of gut and respiration, osmotic and ionic regulations of the gills, which in turn could ultimately affect the survival and growth of P. homarus. Thus, all possible remedial measures should be adopted to prevent the occurrence of copper contamination in the aquatic environment.

Immunohistological classification of ionocytes in the external gills of larval Japanese black salamander, Hynobius nigrescens Stejneger

In this cytological and immunohistological study, we clarified the localization of the membrane transporters Na(+) , K(+) -ATPase (NKA), vacuolar-type H(+) -ATPase (VHA), and epithelial sodium channel (ENaC) and distinguished ionocyte subtypes in the gill of the Japanese salamander (Hynobius nigrescens). In larvae (IY stages 43-65), NKA immunoreactivity was observed on the basolateral plasma membrane in more than 60% cells and less than 20% cells in the primary filaments and secondary lamellae of the external gills, respectively. VHA immunoreactivity was observed on the apical membrane of some epithelial cells in the secondary lamellae of the external gills. High ENaCα immunoreactivity was widely observed on the apical cell membrane of a population of squamous cells, presumably pavement cells (PVCs), and mitochondria-rich cells (MRCs), in the primary filaments and secondary lamellae of the external gills. Using double immunofluorescence microscopy, epithelial cell types involved in ionic regulation were characterized and divided into three ionocyte types: NKA-, NKA- and ENaC-, and VHA-positive cells. VHA-immunoreactive cells as well as NKA-positive cells were observed during IY stages 43-65 of the salamander larvae. During late stages of metamorphosis, NKA, VHA, and ENaCα immunoreactivities in the external gills decreased and finally disappeared during the completion of metamorphosis (IY stage 68). PVCs and MRCs in the external gills are probably involved in acid-base balance regulation and osmoregulation in urodele amphibian larvae. The results are discussed in relation to the ionocytes previously reported in fish gills and the frog skin epithelium.

Comparative study of the three attachment mechanisms of diplectanid monogeneans

One of the main characteristics of the monogenean family Diplectanidae Monticelli, 1903 is their complex haptor formed by 2 pairs of hooks, transversal bars, 14 peripheral marginal hooks, and accessory adhesive organ (lamellodisc or squamodisc) that can be present or absent. Sub-family Lamellodiscinae Oliver, 1969 presents one or two lamellodiscs, formed by several overlapped lamellar esclerites (lamellae) which are piled up. Species like Furnestina echeneis only have one large ventral lamellodisc. This organ function has been categorized in different ways (i.e. accessory adhesive organ, supplementary or compensating disc or sucker), although its real mode of operation and function is still unclear. Specimens of Lamellodiscus and F. echeneis were examined. The lamellodisc of F. echeneis, studied both in vivo and fixed, seems to work as a sucker: the separated lamellae revolve around the single smallest lamellodisc lamella like the slats of a hand-held fan and create a suction volume. Lamellodiscus spp. lamellae (except the basal one) slide in telescopic movement, exerting a posterior and ventral or dorsal force that tightens it to the secondary gill lamellae. This force is contrary to the pulling force of hooks. Opposite forces together with the attachment to two different secondary gill lamellae gives strong binding and stability. These observations were compared with previous knowledge about Diplectanum aequans of subfamily Diplectaninae Monticelli, 1903, whose squamodiscs are formed by numerous spines and presents a different attach strategy. D. aequans produces extensive and deep alterations in the gill epithelium surrounding the parasite. The different attachment mechanisms of the diplectanid species can explain the different degrees of damage that each species provoke, and the information provided in this work can be useful for anthelmintic treatment designs.