A study on ectoparasites in Indian Mackerel, Rastrelliger kanagurta (Cuvier, 1817) of Thiruvananthapuram coast, South India

Parasitic infestation in marine fish requires urgent attention, especially those that infect economically important fishes, which affect their aesthetic quality and palatability. Ectoparasites in Indian Mackerel, Rastrelliger kanagurta (Cuvier, 1817), have not been studied well. Morphological and seasonal study of ectoparasites in R. kanagurta from the Thiruvananthapuram coast was conducted during March-August 2018. The study investigated three parasitic groups: Trichodinids, Digenean cysts (Centrocestus Looss, 1899), and Cymothoids (Norileca indica Milne Edwards, 1840 and Nerocila phaiopleura Bleeker, 1857) from R. kanagurta during the present study. Of the 240 fishes examined, the Trichodinids and digeneans showed 100% prevalence on the gill samples. Seasons had no significant effect on trichodinids and digeneans prevalence. However, parasitic Cmothoids fluctuated significantly according to the season. They showed greater prevalence during the pre-monsoon (45%) and least in monsoon (25%) due to environmental parameters like rainfall, salinity, and temperature. Trichodinids parasitized gills of R. kanagurta showed increased mucus production, paleness in the gills, and multifocal whitish areas. The Cymothoid infested fish showed lesions with the erosion of the epidermis and underlying dermis at the site of attachment. The noticeable changes were observed in the gill epithelium due to the encystment of digeneans. The Trichodinid ciliates and Heterophyid digenean cysts (Centrocestus Looss, 1899) are reported for the first time in R. kanagurta.

Histopathological alterations caused by monogenean parasites the gills of tambaqui Colossoma macropomum (Serrasalmidae)

Monogeneans are ectoparasites of fish with a global distribution. In farmed fish, high infestations may result in morbidity and mortality. This study investigated the histopathological effects of three species of monogeneans Anacanthorus spathulatus, Notozothecium janauachensis and Mymarothecium boegeri on the gills of farmed Colossoma macropomum. Parasitological indices revealed a prevalence of 100%, and a mean abundance of 81.3 ± 11.8. This infection caused displacement of the gill epithelium, focal hyperplasia of epithelial cells, lamellar fusion, congestion and shortening of the secondary lamellae of gills, in addition a complete fusion of the secondary lamellae. However, these tissue alterations were reversible and punctually located lesions, which may not compromise the normal functioning of gills. Lastly, this study showed the potential damages caused by parasite monogeneans to gills of infested fish, thus sanitary management is essential for the growth of fish farm of C. macropomum.

Assessing the histological changes in fish gills as environmental bioindicators in Paraty and Sepetiba bays in Rio de Janeiro, Brazil

The use of fish species uses as bioindicators is an important environmental monitoring tool. Histological biomarkers are adopted to assess the health conditions of different organisms and to indicate an environmental hazard. Histology can be applied as an effective method to analyze the effects of pollutants and other stressors. Accordingly, histological changes in the gill epithelium were analyzed to assess the adoption of fish species Menticirrhus americanus (Linnaeus, 1758) and Micropogonias furnieri (Desmarest, 1823) as a bioindicator to measure environmental quality in Paraty and Sepetiba bays, in Rio de Janeiro. A random sample of 58 fish was collected from the assessed bays. We found Paraty Bay to be in good conservation condition, whereas Sepetiba Bay is contaminated. The fish species collected from Sepetiba Bay showed lesions such as epithelial lifting, aneurysm, and necrosis in the gills; thus, it was possible to suggest that histological biomarkers be used bioindicators to measure the environmental impact in these bays.

HISTOPATHOLOGY STUDIES OF SELECTED ORGANS OF Hemichromis fasciatus INHABITING IGUN GOLD MINING AND OPA RESERVOIRS, OSUN STATE, NIGERIA: A COMPARATIVE STUDY

This study examined the histopathological alterations in the gills, fillet and liver of Hemichromis fasciatus in Igun reservoir (located in an abandoned goldmine area) compared to those of Opa reservoir. Life fish species were collected from Opa and Igun reservoirs and identified in the laboratory. Techniques based on histological analyses were done on the organs and photomicrographs taken using digital binocular compound LED microscope. Epithelial lifting and hypertrophy of lamellae were observed in the gills of H. fasciatus in Opa reservoir and compared to rupture of gill epithelium, rupture of chloride cell, fusion, hyperplasia, curling of lamellae in H. fasciatus of Igun reservoir. The fillet of H. fasciatusin Opa and Igun reservoirs revealed splitting and atrophy of muscle bundles. Also, parasite cyst and necrosis were observed in the fillet of H. fasciatus of Igun reservoir compared to degeneration in muscle bundles in the fish of Opa reservoir. Similarly, the liver of H. fasciatus in Igun and Opa reservoirs showed splitting at the wall of central vein, hepatopancreas and liver cells degeneration. Moreover, nucleus hypertrophy was also identified in the liver of H. fasciatus in Opa reservoir compared to vascular congestion in the central vein, bile duct, portal vein and portal artery of H. fasciatus in Igun reservoir. The study therefore concluded that H. fasciatus specimens in Igun reservoir were histopathologically unhealthy as compared with those of Opa reservoir probably due to the high level of pollution resulting in bioaccumulation of heavy metals in Igun reservoir samples. Obayemi, O. E | Department of Zoology, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria