ABSTRACT
High mortality is among the most serious problems and challenges in the ornamental fish trade. Examination of the discus Symphysodon aequifasciatus from ornamental fish hatchery revealed infestation with the monogenean Sciadicleithrum variabilum. Gill infestation with this monogenean induced serious damage to the gill lamellae, including clavate lamellae, vascular congestion in the peripheral blood vessels, lamellar blood sinus dilation, and other structural anomalies. Light and transmission electron microscopy showed that in all infested hosts the interlamellar cell mass (ILCM) completely filled the interlamellar space. The monogenean-associated damage combined with the ILCM led to severe impairment of respiratory efficiency of the gill. Anti-parasitic treatment was applied during breeding (hatchery), which was followed by almost complete regression of the ILCM seen in the fish. A single point of ILCM hyperplasia was observed in only one specimen at the site of parasite attachment to the gill filament. The ILCM covering the gill lamellae protected the discus against infestation with this monogenean, but considerable reduction in the gaseous exchange surface and serious damage to the gill lamellae contributed to the increased mortality of the fish in the hatchery, which reached 90%.
Subject(s)
Cichlids , Gastropoda , Trematoda , Animals , Gills/parasitologyABSTRACT
BACKGROUND: Widespread common carp (Cyprinus carpio) mortalities have been recorded in Khuzestan province fish farms in recent years. In summer of 2017 two cases of harmful algal bloom were encountered that led to massive mortality in common carp in Khuzestan, Iran. AIMS: The aim of this study was to identify the possible etiologic agent of two mortalities with characteristic symptoms of gill lesions due to harmful algae. METHODS: Water samples were collected and 5 moribund fishes were examined by histophatologic, scanning electron microscopic and PCR examination. RESULTS: In wet smear preparations, a lot of algal cells and fragments, and sloughed, necrotic epithelial cells were observed between the lamellae. In histopathologic examination of gills, hyperplasia, necrosis and algal cells surrounded by hyperplastic cells were seen in tissue sections. No inflammatory cell aggregation was noticed. In scanning electron microscopic examination the algae was found attached to the gill surface (cell diameter: 8.5 ± 4.2 µm) with 2 equal flagella. CONCLUSION: Phytoplankton analysis using direct microscopy and electron microscopy, morphologically resembling Heterosigma was identified, however, in PCR tests, Heterosigma analysis showed negative results, therefore the causative agent was called "Heterosigma-like" algae.
ABSTRACT
Com o objetivo de analisar a intensidade das alterações histológicas em brânquias de Centropomus undecimalis para avaliar a qualidade da água do Parque Ecológico Laguna da Jansen, em São Luís, Estado do Maranhão, coletaram-se exemplares de peixes no período chuvoso de 2012 e amostras de água nos períodos seco de 2011 e chuvoso de 2012 para análises físico-química e bacteriológica. Os resultados mostraram que a maioria dos parâmetros físico-químicos e bacteriológicos estava de acordo com os valores estabelecidos pela Resolução do CONAMA nº 357 de 2005. As alterações histológicas observadas foram: elevação do epitélio lamelar; proliferação excessiva de células dos epitélios filamentar e lamelar causando fusão total ou parcial das lamelas; alteração da estrutura das lamelas; hiperplasia das células mucosas; ruptura do epitélio lamelar; espessamento descontrolado do tecido proliferativo filamentar e lamelar e aneurismas de vários tamanhos. Também foi observada a presença de parasito em alguns exemplares. O Índice de Alteração Histológica (IAH) por indivíduo variou de 2 a 114. O valor médio do IAH obtido foi de 40,3, demonstrando que as brânquias dos indivíduos amostrados da espécie C. undecimalis apresentaram alterações de moderadas para severas no tecido. As alterações histológicas encontradas indicam que esses indivíduos desenvolveram mecanismos de defesa contra a ação de estressores presentes na água da laguna e a um provável desequilíbrio parasito-hospedeiro-ambiente associado à baixa qualidade do ambiente...
Aiming to analyze the intensity of the histological changes in the gills of Centropomus undecimalis to assess the water quality at Ecological Park of the Laguna da Jansen, in São Luís, State of Maranhão, specimens of fish were collected during the rainy season of 2012 and water samples during the dry season in 2011 and rainy season in 2012 for physical-chemical and bacteriological analyses. The results showed that most of the physical-chemical and bacteriological parameters analyzed agreed with the values established by CONAMA Resolution nº 357 of 2005. The histological changes were elevation of the lamellar epithelium, excessive cell proliferation of the filamentum and lamellar epithelium causing total or partial melting of the lamellar; changing the structure of the lamellar, hyperplasia of mucous cells, disruption of the lamellar epithelium, uncontrolled proliferative tissue filamentum thickening and lamellar and aneurysms in various sizes. We noted the presence of parasites in some samples. The Index Histological Amendment (IAH) per individual ranged from 2 to 114. The mean IAH obtained was 40.3, demonstrating that the gills of the individuals of the C. undecimalis species showed moderate to severe changes in the tissue. The histological findings indicate that these individuals have developed defense mechanisms against the action of stressors present in the water of the Laguna da Jansen and a probable parasite-host-environment imbalance associated with the environment's low quality...
