Gill Lesions Research Articles

Particulate accumulations in the vital organs of wild Brevoortia patronus from the northern Gulf of Mexico after the Deepwater Horizon oil spill.

Histopathologic lesions were observed in the commercially important filter-feeding fish, Brevoortia patronus (Gulf menhaden), along the Louisiana Gulf Coast. Menhaden collected from Louisiana waters in 2011 and 2012, 1 and 2 years following the Deepwater Horizon oil spill, showed varying severities of gill lesions as well as an unusual accumulation of black particulates visible at necropsy in the heart and stomach vasculature. The PAH derived particulates were typically 1-4 µm in diameter, but larger aggregates were observed in the coronary vessels on the ventricle surfaces and their location and size was confirmed by light microscopy. Composited particulate composition was consistent with weathered petrogenic polycyclic aromatic hydrocarbon (PAH) mixtures based on GC-MS analysis. Particulates were present in 63 and 80% of fish hearts and 70 and 89% of stomach muscularis collected in 2011 and 2012, respectively. Tissue embedded particulates can lead to localized cellular damage from bioavailable compounds, as well as chronic effects from occlusion of sensitive tissues' blood flow. The PAH derived particulates appeared to act as emboli in small capillaries, and could associated with localized inflammation, focal necrosis and inappropriate collagen and fibroblast tissue repair. We believe large volume filter feeding teleosts, such as menhaden (up to 3 million gallons per year/fish) with high lipid content, have a higher exposure risk and greater potential for toxicity from toxic particulates than other higher trophic level finfish. Suspended PAH derived particulates following an oil spill therefore, should be considered when assessing long-term ecological impacts and not be limited to physical contact (coating) or water soluble fractions for assessing toxicity (gill and neurologic).

Isolation and identification of Vibrio toranzoniae associated with diseased red conger eel (Genypterus chilensis) farmed in Chile

The present study deals with the first isolation of Vibrio toranzoniae from cultured red conger eel (Genypterus chilensis). During the summer season of 2011, mortalities were observed in young red conger eel at one aquaculture experimental rearing system in Quintay, Valparaiso, Chile. The microbiological analysis of the diseased fish resulted in the isolation of three dominant and representative isolates, designated as R.17, R.18 and R.19, which were obtained from gill, fin and external lesions from three different fish, respectively. All isolates were identified as V. toranzoniae by means of a polyphasic taxonomic approach, including phenotypic characterization, sequencing of 16S rRNA and housekeeping genes, and DNA–DNA hybridization. Inoculation of a representative strain (R18) in turbot as model fish species demonstrated the pathogenic potential for fish of the Chilean isolates. Results obtained indicate that the geographical and host distribution of V. toranzoniae is wider than expected, and that this species may have negative incidence in the culture of marine organisms.

Cyprinid herpesvirus-3 (CyHV-3) disturbs osmotic balance in carp (Cyprinus carpio L.)—A potential cause of mortality

Cyprinid herpesvirus-3 (CyHV-3) causes a fatal disease in carp (Cyprinus carpio) and its ornamental koi varieties which seriously affects production and trade of this fish species globally. Up to now, the pathophysiology of this disease remains unclear. Affected individuals develop most prominent lesions in gills, skin and kidney, in tissues which are involved in the osmotic regulation of freshwater teleosts. Therefore, here serum and urine electrolyte levels were examined during the course of an experimental infection of carp with CyHV-3. In infected carp an interstitial nephritis with a progressive deterioration of nephric tubules developed, which was paralleled by elevated electrolyte losses, mainly Na+ in the urine. The urine/plasma ratio for Na+ increased from 0.03 in uninfected carp to 0.43–0.83 in carp under CyHV-3 infection, while concentration of divalent ions were not significantly changed. These electrolyte losses could not be compensated since plasma osmolality and Na+ concentration dropped significantly in CyHV-3 infected carp. This was most probably caused by the progressive deterioration of the branchial epithelium, which in teleosts plays a prominent role in osmoregulation, and which was seen concomitantly with decreasing electrolyte levels in the serum of carp under CyHV-3 infection.Immediately after infection with CyHV-3, by day 2 post exposure, affected carp showed severe anaemia and prominent leucocytosis indicating the development of an acute inflammation, which could intensify the observed hydro-mineral imbalances.The data presented here show that an infection with CyHV-3 induces an acute inflammation and a severe dysfunction of osmoregulation in affected carp or koi, which may lead to death in particular in the case of acute disease progression.

Vaccination with recombinant protein (r22C03), a putative attachment factor of Neoparamoeba perurans, against AGD in Atlantic salmon (Salmo salar) and implications of a co-infection with Yersinia ruckeri

Amoebic gill disease (AGD) affects salmonids during the marine grow-out phase in the Tasmanian industry and in other major salmonid producing countries. During the period post-transfer to seawater, the bacterial condition yersiniosis can also cause high levels of mortality in Atlantic salmon grown in Tasmania, in addition to the hatchery outbreaks. The recombinant protein r22C03, a mannose-binding protein-like (MBP-like) similar to attachment factors of other amoebae, was tested as a vaccine candidate against AGD in a large scale challenge trial. Fish were immunised with r22C03 combined with FCA via intraperitoneal (i.p.) injection, and given a booster five weeks later by either i.p. injection (RP group) or by a dip-immersion (mRP). Fish were then challenged twice with Neoparamoeba perurans: the initial challenge 16 weeks after primary immunisation was terminated due to presence of ulcerative lesions in the skin of salmon; the second challenge was carried out after five weeks of treatment with oxytetracycline. These skin lesions might have been associated with a concurrent infection with Yersinia ruckeri, which was detected by real-time qPCR in serum of a large proportion of moribund and survivor fish after the AGD challenge. Before and during the N. perurans infection, levels of antibodies against r22C03 were measured by ELISA in serum, skin mucus and supernatant from skin and gill explants. For the second challenge, the average size of AGD lesions was recorded from histology sections and survival curves were obtained. Before AGD challenge, r22C03 induced antibody responses in serum and explants with both vaccination strategies. At the end of the challenge, levels of antibodies were lower than before challenge irrespective of treatment. Both vaccinated groups presented increased serum antibody responses, while only mRP presented antibody responses in skin mucus, and no significant antibody responses were measured in the explants. Antibodies did not confer protection to N. perurans infection, as no difference was observed in the survival curves of the vaccinated and control groups, and there was no effect on the gill lesion size. The concurrent yersiniosis infection probably represented more closely infection patterns observed in commercial settings. However, it could have interfered with the survival results and with the ability of the fish to respond to the amoebae infection.

Scanning Electron Microscopic Studies on the Gills of the Catfish Heteropneustes fossilis (Bloch) Exposed to Copper at Varying pH.

Alterations in gill ultra-structure of the catfish, Heteropneustes fossilis exposed to copper at varying pH were investigated using scanning electron microscopy. Fish were treated with 3ppm copper sulphate (48h LC50 concentration at pH 7±0.5) at varying pH of diluent water. Low pH resulted in higher copper (30.01µg/g dry wt.) accumulation on gills as compared to neutral and high pH treatments, at 18.01 and 16.07µg/g respectively. Post (48h) exposure observations included lesions in gills of the treated fish, epithelial lifting, loss of alignment of primary and secondary lamellae, hyperplasia, and hypertrophy of the respiratory epithelium. Fish at pH 5±0.5 showed relatively greater injury compared to pH 8±0.5. The severity of gill damage in copper treated fish followed the sequence of pH 5±0.5>pH 7±0.5>pH 8±0.5. Results indicate the synergistic stress caused in fish gill due to acute toxicity of copper and low pH.

Effects of contaminated harbour sediment on the growth and histopathology of Nile tilapia (Oreochromis niloticus): A long-term study

Growth and histopathology of juvenile Oreochromis niloticus (L.) was studied upon continuous exposure to contaminated sediments from the maritime fisheries harbour of Galle, Sri Lanka. Sixteen week long experiment comprised of four duplicated groups of fish in freshwater (NC: negative control without sediment, C: control with unit-dose of pristine sediment, T1 with unit-dose of contaminated sediment, T2 with three unit-doses of contaminated sediment) with total renewal of water and sediment on each fourth day serially. Unit-dose of sub-lethal wet sediment was arbitrarily decided as 38ml through a series of tolerance tests. Total length and weight of fish were recorded (n=20x4 per group) initially and on completion of weeks 4, 10 and 16. Gill and liver histology was qualitatively examined using four sacrificed fish per group at termination. Results showed that harbour sediment in water significantly (p<0.05) decreased cumulative growth rates of T1 and T2 fish in terms of absolute growth rate (0.58-0.59 mm/day and 0.17g/day), relative growth rate (1.52-1.56% length gain day-1 and 0.73% weight gain day-1) and specific growth rate (0.89-0.91% day-1 in length, 2.60-2.61% day-1 in weight) as compared to C and NC groups. T1 and T2 juveniles developed toxicopathic signs in gill (lamellae-fusion, decreased inter-lamellar space) and in liver (extensive necrosis, hydropic vacuolation). Growth parameters remained similar between C and NC groups throughout the study with no histological alterations suggesting that sediment borne salinity had no differential effect across groups. This study shows that exposure to contaminated sediment from Galle fisheries harbour causes growth reduction and pathologic lesions in gills and liver of O. niloticus juveniles. DOI: http://dx.doi.org/10.4038/jur.v2i1-2.7850 J. Univ. Ruhuna 2014 2:14-23

Gill infection model for columnaris disease in common carp and rainbow trout.

Challenge models generating gill lesions typical for columnaris disease were developed for the fry of both Common Carp Cyprinus carpio and Rainbow Trout Oncorhynchus mykiss by means of an immersion challenge and Flavobacterium columnare field isolates were characterized regarding virulence. Carp inoculated with highly virulent isolates revealed diffuse, whitish discoloration of the gills affecting all arches, while in trout mostly unilateral focal lesions, which were restricted to the first two gill arches, occurred. Light microscopic examination of the gills of carp exposed to highly virulent isolates revealed a diffuse loss of branchial structures and desquamation and necrosis of gill epithelium with fusion of filaments and lamellae. In severe cases, large parts of the filaments were replaced with necrotic debris entangled with massive clusters of F. columnare bacterial cells enwrapped in an eosinophilic matrix. In trout, histopathologic lesions were similar but less extensive and much more focal, and well delineated from apparently healthy tissue. Scanning and transmission electron microscopic observations of the affected gills showed long, slender bacterial cells contained in an extracellular matrix and in close contact with the destructed gill tissue. This is the first study to reveal gill lesions typical for columnaris disease at macroscopic, light microscopic, and ultrastructural levels in both Common Carp and Rainbow Trout following a challenge with F. columnare. The results provide a basis for research opportunities to examine pathogen-gill interactions.

Biomarcadores histopatológicos na espécie Hoplias malabaricus (Pisces, Osteichthyes, Erythrinidae) em uma Unidade de Conservação de São Luís (MA)

Neste estudo objetivou-se validar dois órgãos (brânquia e fígado) de Hoplias malabaricus para análise de biomarcadores de contaminação aquática na Área de Proteção Ambiental (APA) do Maracanã em São Luís-MA. Exemplares de traíra foram capturados em uma lagoa de policultivo e no Rio Ambude, localizados na APA do Maracanã. A biometria foi realizada em laboratório. Brânquias e o fígado de cada espécime foram fixados em formol a 10% e mantidos em álcool a 70% até a execução da técnica histológica usual. Cortes de aproximadamente 5µm de espessura foram corados em hematoxilina e eosina (HE). Os resultados referentes à biometria dos peixes capturados durante o período de estiagem indicaram que o comprimento total e padrão dos exemplares foram maiores quando comparados com os indivíduos do período chuvoso. As alterações hepáticas identificadas foram: lipidose, necrose, infiltração leucocitária, vacuolização do citoplasma, hemossiderina e centro de melanomacrófagos. Constataram-se as seguintes lesões branquiais: fusão lamelar, aneurisma lamelar, deslocamento e necrose do epitélio, proliferações de células do muco e dilatação capilar. As respostas biológicas de H. malabaricus, registradas em nível branquial e hepático, podem ser caracterizadas como biomarcadores de contaminação aquática. As brânquias mostraram-se como os melhores órgãos para esse tipo de análise na espécie. Esses resultados indicam que os peixes da região apresentam a saúde comprometida por poluentes presentes nos ambientes analisados.

A Survey of Gill Histopathology of Thirteen Common Fish Species in the Sanyati Basin, Lake Kariba, Zimbabwe/ Badania Histopatologiczne Skrzeli Trzynastu Pospolitych Gatunków Ryb W Zlewni Sanyati, Jezioro Kariba, Zimbabwe

Abstract Following a study of gill pathology in African catfish (Clarias gariepinus) and Nile Tilapia (Oreochromis niloticus) from the Sanyati Basin of Lake Kariba, Zimbabwe, a similar survey was carried out in thirteen other common fishes of Lake Kariba. Gill tissues were dissected from the fish, preserved and prepared for histology. The prepared tissue sections were observed under a light microscope. Six histopathological lesions were observed, namely epithelial lifting, hyperplasia, lamellae fusion, parasitic cysts, oedema, and aneurysm. Epithelial lifting was prevalent in all fish species whilst aneurysm was only observed in two fish species. Synodontis zambezensis had the highest prevalence of gill lesions whilst Marcusenius microlepidotus, Brycinus imberi and Micralestes acutidens had the least prevalence of lesions. Most of these histopathological lesions were mild to moderate, and this is suggestive of good health of the fish species investigated. Seventy seven percent of the fish species were infected with monogenean ectoparasites. More research on fish health in Lake Kariba is recommended and future studies should aim to quantify these histological changes in relation to environmental conditions of the lake. This will enable histopathology to be used as a biomarker or predictor of water quality.

Effects of single and repeated infections with Neoparamoeba perurans on antibody levels and immune gene expression in Atlantic salmon (Salmo salar)

Amoebic gill disease (AGD) is the main health problem for the salmon industry in Tasmania, Australia and is now reported in most salmon producing countries. Antibody and gene expression responses to the pathogen, Neoparamoeba perurans, have been studied independently following primary exposure; however, the effects of sequential reinfection, which can often occur during net-pen culture of salmon, remain unclear. The association between the transcription of immunoglobulin (Ig) and their systemic and mucosal antibody levels in regards to AGD is unknown. Herein, we assessed the antibody responses as well as Ig transcription in the gills of Atlantic salmon infected only once and also sequentially with N. perurans. After four successive AGD challenges, no significant differences in plasma or skin mucus levels of IgM were observed between AGD-naïve and challenged fish. However, IgM gene expression in gill lesions of AGD-affected fish increased up to 31 d after infection, while no changes in IgT, TCR and CD8 transcription were observed. Changes at IgM transcription level did not match the lack of antibody response in mucus, which is possibly explained by weak correlations existing between protein and mRNA abundances in cells and tissues. In the second experiment, which investigated Ig responses to AGD at the transcriptional as well as antibody production level in salmon after a single infection, the levels of serum or skin mucus IgM antibody were not affected and no changes in the IgM or IgT transcription were induced.

Structural alterations in Gills, Liver and Ovaries of Tilapia Fish (Saratherodon galilaeus) as a Biomarker for Environmental Pollution in Ismalia Canal

The present work studied the histological changes in gills, liver and ovaries of Tilapia fish (Saratherodon galilaeus) subjected to disturbed urban stream (sewage and industrial contamination) of two sites (EL-aakada and EL-amerya) on Ismailia Canal during summer season. The most common lesions in gills were epithelial lifting, hyperplasia and hypertrophy of the respiratory epithelium, and lamellar fusion. Liver hepatocytes showed hypertrophied, cytoplasmic and nuclear degeneration, inflammatory cells aggregates and focal areas of necrosis. The ovary showed widened vitellogenic space filled with huge debris, the oogonial cells and immature oocytes were in the process of degeneration particularly at the ooplasmic level. The most sever lesions were comparatively in the liver. It is concluded that histopathology can used as a biomarker for study the effect of pollutants in organs of fish.

Fusarium solani species complex associated with carapace lesions and branchitis in captive American horseshoe crabs Limulus polyphemus.

Captive American horseshoe crabs Limulus polyphemus housed at the National Aquarium presented with a variety of shell and gill lesions over a 3 yr period. Carapace lesions were located on both the dorsal and ventral prosoma and opisthosoma and included multifocal circular areas of tan discoloration, ulcerations, and/or pitting lesions, extending from superficial to full thickness. Gill lesions involved both the book gill cover (operculum) and individual book gill leaflets and included multifocal circular areas of tan discoloration, tan to off-white opaque proliferative lesions, and/or areas of black discoloration. Histopathology revealed fungal hyphae, with variable morphology throughout the thickened and irregular cuticle of the carapace and occasionally penetrating into subcuticular tissues, with associated amebocytic inflammation. Book gill leaflets were infiltrated by fungal hyphae and contained necrotic debris and amebocytes. Thirty-eight of 39 animals (97%) evaluated via histopathological examination had intralesional fungal hyphae. Fungal cultures of carapace and gill lesions were attempted in 26 tissue samples from 15 individuals and were positive in 13 samples (50%), with 10 cultures (77%) yielding identification to genus. Fusarium sp. was identified in 8 of the 10 cultures (80%) via culture morphology. The Fusarium solani species complex was confirmed in 6 of these 8 (75%) via polymerase chain reaction amplification of 2 different ribosomal-specific sequences of isolated fungal DNA. Ante-mortem systemic and topical treatments were performed on some affected individuals, but no appreciable change in lesions was observed. Mycotic dermatitis and branchitis are serious health issues for captive American horseshoe crabs.

Evaluation of the use of common sculpin (Myoxocephalus scorpius) organ histology as bioindicator for element exposure in the fjord of the mining area Maarmorilik, West Greenland

The former Black Angel lead–zinc mine in Maarmorilik, West Greenland, is a historic example of how mining activity may result in a significant impact on the surrounding fjord system in terms of elevated concentrations of especially lead (Pb) and zinc (Zn) in seawater, sediments and surrounding biota. In order to shed light on the present contamination and possible effects in the fjord we initiated a range of studies including a pilot study on gill and liver morphology of common sculpins (Myoxocephalus scorpius) around Maarmorilik. Sculpins were caught and sampled at five different stations known to represent a gradient of Pb concentrations. Fish livers from all specimens were analyzed for relevant elements in the area: Fe, Zn, As, Cu, Se, Cd, Pb, Ag, Hg, Co and Ni. Lead, As and Hg showed significant differences among the five stations. For 20% of the sculpins, Hg concentrations were in the range of lowest observed effect dose (LOED) of 0.1–0.5μg/gww for toxic threshold on reproduction and subclinical endpoints. Likewise LOEDs for tissue lesions, LOEDs for biochemistry, growth, survival and reproduction were exceeded for Cd (0.42–1.8μg/gww) and for As (11.6μg/gww) in 28% and 85% of the sculpins, respectively. Similar to this, the no observed effect dose (NOED) for biochemistry was exceeded for Pb (0.32μg/gww) and for growth, mortality and reproduction for Zn (60–68μg/gww) in 33% and 24% of the sculpins, respectively. For all sculpins, females were significantly larger than males and for five of the elements (Fe, Co, Ni, Cu, Se) females had higher concentrations. The chronic lesions observed in liver (mononuclear cell infiltrates, necrosis, vacuolar hepatocytes, portal fibrosis, bile duct hyperplasia, active melanomacrophage centers) and gills (fusion and edema of secondary lamellae, laminar telangiectasis, mononuclear cell infiltrates, blebs) were similar to those in the literature studies for both wild and laboratory exposed sculpins and other fish species carrying similar or higher Hg concentrations. Ignoring sex and size, specimens with hepatic cell infiltrates had the highest concentrations of most elements, a relation that was also found for gill telangiectasis and Hg (all p<0.05). When controlling for sex and size, the prevalence of vacuolar hepatocytes and endoparasites was significantly highest at the three most contaminated stations and similar differences were found for liver necrosis. We suggest that beside exposure to mining-related elements, other environmental factors, such as parasites, might be co-factors in the development of the observed liver and gill lesions. Therefore, sculpin liver and gill pathology are likely to be suitable health indicators when biomonitoring gradients of mining and other element related activity effects; while a larger study is required to fully evaluate the relationships.

Immunohistochemical localization of inflammatory cells and cell cycle proteins in the gills of Loma salmonae infected rainbow trout (Oncorhynchus mykiss)

Microsporidial gill diseases particularly those caused by Loma salmonae incur significant economic losses to the salmonid aquaculture industry. The gill responses to infection include the formation of xenomas and the acute hyperplastic inflammatory responses once the xenomas rupture releasing infective spores. The aim of this work was to characterize the inflammatory responses of the gill to both the presence of the xenomas as well as the hyperplasia associated with L. salmonae infection in the rainbow trout gill following an experimental infection using immunohistochemistry. Hyperplastic lesions demonstrated numerous cells expressing PCNA as well as an apparent increased expression of caspase-3 and number of apoptotic cells (TUNEL positive cells). There was an expression of TNFα in individual cells within the gill and increased expression of a myeloid cell line antigen indicating the presence of granulocyte infiltration of both the hyperplastic lesions as well as the xenomas. Similar immune-reactivity was seen in gill EGCs. Hyperplastic gill lesions showed a marked infiltration of CD8+ cells and expression of MHC class I antigens. These findings suggest that L. salmonae xenomas may be subject to infiltration by the host immune cells as well as the mounting or a marked cellular cytotoxic immunoreaction in the resultant hyperplasia following xenoma rupture and spore release.

Pathology and mortality associated with the mauve stinger jellyfish Pelagia noctiluca in farmed Atlantic salmon Salmo salar L.

Jellyfish can cause significant losses to the aquaculture industry. This report describes the clinical presentation and pathology caused by the mauve stinger jellyfish Pelagia noctiluca (Forsskal, 1775) in cultured Atlantic salmon Salmo salar L. in Ireland and highlights the potential consequences and need for descriptive pathology of such interactions. P. noctiluca is a member of the cnidarian class Scyphozoa (Order Semaeostomeae; Family Pelagiidae) and has worldwide distribution through the warm and temperate waters of the marine environment. This golden brown to purple jellyfish species lacks the benthic polyp stage and has a primarily pelagic habitat, although ocean currents bring it closer to coastal waters. P. noctiluca is frequently observed from the west coast of Ireland especially during the autumn months, but large aggregations are not commonly reported. In a jellyfish survey carried out around Ireland in 2009, P. noctiluca was the most abundant species found, accounting for 93% of the overall catch (total wet weight of gelatinous species) (Bastian et al. 2011). Its distribution and density were found to be heterogeneous, with great variation between regions (apparent North-South gradient in density) and sampling points (Bastian et al. 2011). When in contact with a fish farm, small jellyfish can pass through the nets, while bigger individuals tend to break up into pieces still capable of stinging the fish. In jellyfish blooms, affected fish can suffer from hypoxia, mechanical damage and toxicity via nematocysts discharge (Baxter et al. 2011a; Rodger, Henry & Mitchell 2011). In 2013, large swarms of P. noctiluca were observed intermittently in several Northern and Southern farms in the west coast of Ireland from the beginning of August to mid-November. Jellyfish presence was determined by visual observations from boat and cages and by divers during removal of mortalities. Zooplankton sampling through vertical net tows and posterior species identification was also carried out. The diagnosis of the jellyfish species involved was based on the morphological features described in detail by Russell (1970). Jellyfish appeared in the vicinity and inside cages (Fig. 1a), and associated mortalities ranged from <1% to 70% depending on farm and pen location. The highest mortalities occurred in two farms situated in the North region, after an atypically warm summer when the seawater temperature ranged from 21 °C in August to 10 °C in November. Significant numbers of jellyfish were observed within the affected cages prior to presence of the gill and skin lesions. Therefore, the reported pathology was directly associated to the jellyfish presence. Affected fish showed respiratory distress, loss of appetite, lethargy and/or increased jumping behaviour. On the most severe cases, up to 80% Correspondence Mar Marcos-L opez, Vet-Aqua International, Unit 7b Oranmore Business Park, Oranmore, Co. Galway, Ireland (e-mail: mar.marcos.lopez@gmail.com)

Effects of combined exposure to 17α-ethynylestradiol and dibutyl phthalate on the growth and reproduction of adult male zebrafish (Danio rerio)

To evaluate the combined effects of 17α-ethynylestradiol (EE2) and dibutyl phthalate (DBP) on the growth and reproduction of male zebrafish, three-month-old fish were exposed to 0.005 or 0.020µg/L EE2, 100 or 500µg/L DBP or their binary mixtures under semi-static conditions. Investigated parameters include the length, weight, condition factor, vitellogenin (VTG) induction, acyl-CoA oxidase (AOX) protein level, histopathological alteration of testis, liver and gill, and reproductive capacity. After 21d exposure, no statistical difference was found among the weights, lengths and condition factors of different treatment groups. In all binary mixture groups, decreased VTG levels were detected compared to EE2-only groups; and the AOX levels were significantly lower than DBP-only treatments while both chemicals can individually induce AOX synthesis. Therefore, EE2 and DBP may act additively on VTG and antagonistically on AOX induction in males. After 45d exposure, delayed gametogenesis was observed for the DBP-only groups, indicated by fewer spermatozoa and more spermatocytes, which was further aggravated with the addition of EE2. The developmental delay of testis partially recovered after a 30d depuration in clean water. Combined exposure also caused liver and gill lesions, which were not alleviated during the 30d depuration, suggesting a nonreversible harmful effect the same as single exposure. Mixed EE2 and DBP were observed to impair the reproductive capability (the fecundity and fertilization rate) of males, while single exposure did not. Co-exposed to 0.020µg/L EE2 and 100µg/L DBP promoted the early hatching of offspring (F1 generation) at 48h post-fertilization (hpf), but the survival rates of the F1 generation were similar in all treatments. Our findings indicate that the effects of mixed EE2 and DBP at environmentally relevant levels can be either antagonistic or additive relying on the specific toxicological endpoints and the respective doses of each chemical.

Effects of anionic polyacrylamide products on gill histopathology in juvenile rainbow trout (Oncorhynchus mykiss)

Anionic polyacrylamide (PAM) products are commonly used to remove suspended materials from turbid waters and to help mitigate soil erosion. In the present study, juvenile rainbow trout (Oncorhynchus mykiss) were exposed to 3 mg/L to 300 mg/L of 10 commercially available PAM products (Clearflow Water Lynx Polymer Log and Clearflow Soil Lynx Granular Polymer; Clearflow Enviro Systems Group), and gill histological parameters were measured following either 7 d or 30 d of polymer exposure. A cationic polymer product (≤0.38 mg/L MagnaFloc 368; Ciba Specialty Chemical) was also tested for comparison. Mild gill lesions were observed in fish exposed to polymer products. Lamellar fusion, interlamellar hyperplasia, epithelial lifting, mucous cell metaplasia, and cell counts of epithelial swelling and necrosis/apoptosis were minimal in fish exposed to environmentally relevant concentrations of anionic polymer (≤30 mg/L). Gill morphology was largely unaffected by exposure to concentrations up to 300 mg/L of many PAM products. Several anionic polymer products noticeably affected gill tissue by increasing epithelial hypertrophy, interlamellar hyperplasia, mucous cell metaplasia, and the frequency of necrotic cells. The severity of the lesions lessened with time, suggesting that fish may have experienced a short-term irritant effect. Similar levels of gill pathology were frequently observed in fish exposed to cationic polymer MagnaFloc 368 despite the concentration being 1000-fold lower than that of the PAM products. These observations highlight the increased toxicity of cationic polymers to aquatic life compared with anionic PAMs.

Exposure to contaminated sediments induces alterations in the gill epithelia in juvenile Solea senegalensis: a comparative in situ and ex situ study

Exposure to contaminated sediments induces alterations in the gill epithelia in juvenile Solea senegalensis: a comparative in situ and ex situ study

Evidence of immune and inflammatory processes in the gills of AGD-affected Atlantic salmon, Salmo salar L.

Amoebic gill disease (AGD) is a disease caused by the ectoparasite Neoparamoeba perurans which affects several cultured marine fish worldwide. The characterisation of pro-inflammatory and immune related genes at the mRNA level in AGD-affected Atlantic salmon gills was performed at 10 days post-inoculation using 2D quantitative RT-PCR, a method of mapping transcriptional responses in tissues. The genes of interest were IL-1β, TNF-α, TCR-α chain, CD8, CD4, MHC-IIα, MHC-I, IgM and IgT. A significant increase in expression of the mRNA of all the genes was observed in the gills of AGD-affected fish. Contrary to previous studies, our data suggest that the parasite, N. perurans, elicits a classical inflammatory response in the gills of AGD-affected fish and indicates that the mRNA expression of immune genes within gill lesions misrepresents the cellular immune response in the gills during AGD.

Amoebic gill disease due to Paramoeba perurans in ballan wrasse (Labrus bergylta)

Ballan wrasse (Labrus bergylta) is cultured for the use as cleaner fish in Atlantic salmon farms. A low level of mortality was experienced in ballan wrasse broodstock tanks during spawning. Examined moribund and clinically healthy fish showed patchy gill lesions characteristic of amoebic gill disease (AGD). Microscopy on wet preparations from gill patches showed large numbers of amoebae. Histology revealed pathology characteristic for AGD, such as extensive hyperplasia, bridging of lamellae and forming of interlamellar spaces. Lesions were associated with amoebae, resembling Paramoeba spp. Molecular studies on both gill samples and gill-derived amoeba-cultures showed the presence of Paramoeba perurans. These observations show that cultured ballan wrasse may host P. perurans infections. Since this observation suggests that ballan wrasse may be infected with P. perurans also in nature, the possible role of wrasses in the epizootiology of AGD in salmonid aquaculture needs to be examined.