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Research Article
Histopathology of the Infestation of Parasitic Isopod Joryma tartoor of the Host Fish Parastromateus niger

S. Ravichandran, T.T. Ajith Kumar, P. Ronold Ross and M. Muthulingam

Research Journal of Parasitology, 2007, 2(1), 68-71.


The infestation of parasitic isopods in the fish Parastromateus niger was studied. Infested fish exhibited histopathological anomalies such as tissue reactions, primarily associated with the formation of granulomas consisted of macrophages and epitheleioid cells, which are occasionally surrounded by a thin rim of fibroblasts. The infestations such as lipofibrosis, hyperaemia, haemorhagic lesions and penetration of dactylus usually pressure atrophy often accompanied by the presence of parasites. Lesions had well developed granulomas that underlined in the muscle or overlying subcutaneous tissue, form these spread to underlying organs.

ASCI-ID: 84-12

Fig. 1 and 2).

Tissue reactions, primarily associated with the formation of granulomas consisted of macrophages and epitheleioid cells, which are occasionally surrounded by a thin rim of fibroblasts.

Fig. 1: Photograph showing the nature of thickening between the gill lamellae in Parastromateus niger

Fig. 2: Photograph showing the damage of gill raker and gill lamellae in Parastromateus niger

Fig. 3: Male and female J. tartoor in the branchial region of Parastromateus niger

Lesions were never encapsulated by developed granulomas that underlain in the lost epidermis. Lesions appeared to originate in the muscle or overlying subcutaneous tissue and from these they started spreading to the underlying organs.

The muscular growth has been identified as lipofibrous nodule that developed in response to the irritation caused by the isopod parasite J. tartoor. A glat nodule of tissue attached to the inner surface of the left operculum by slightly constricted base and formed about 1 to 2 mm thickness into the gill chamber. The base of the thickening consisted of a large normal fat tissue that is continuous with adjacent opercula flat. The surface of the thickening is solidly fibrous with a few small folds. In between, fibrous tissue and fat tissues intermingled. The surface epithelium that must have been present when the fish was alive was not in the section.

Nature of damage, observed in the gill remained the same, but the degree of damage varies, as the closely opposed gill arch observed a higher damage (Fig. 3). Terminal and middle regions of the gill lamellae bulged and the growth was stunted. Secondary gill lamellae uneven clubbed and showed fusion. Middle portion of some of the gill lamellae expanded to have some space or gap. Bifurcation was noticed at the tip of lamellae and the cartilaginous support of the gill arch was twisted.


Histological examination of the gill on which the isopod had settled, showed that the actions of the parasites meet with a characteristic reaction of the gill tissue, a reaction which is surprisingly uniform regardless of the stimulus applied; this reaction is the hypertrophy of epithelial and connective supporting tissues of the gill filament.

The lipofibrosis observed at the inner surface of the operculum was semihard and the surface was finely granulated and, showed invasive tendency. Accumulation of deeply stained acidophilic plasmacytes, marked separation of hyperplastic growth, perfuse infiltration of lymphocytes and granulocytes are the characteristic features of the lipofibrosis noticed in the present study. Earlier workers indicate the presence of hyperplastic and hypertrophied reaction as function of infection due to isopod parasites (Eller, 1975; Romestand et al., 1977; Rand, 1986).

Rand (1986) observed the presence of melanophores in the epidermis and dermal layers of fishes infested by Nerocila acumunata. In the present study, similar distinct melanophores were not accounted due to infestation of J. tartoor. Healthy tissue were absent at the pereopod attachment sites. Epidermis around pereopod attachment sites was hyperplastic, also, infested tissues appear to be deteriorated and is irregular in structure. The epithelial tissue contains intense hypertrophied cells. The effects may be due to the stress excerted by the parasite to the underlying tissues.

In the present study, apart from hyperplastic and hypertrophied reaction, the host tissue also showed lipofibrosis. This nodular formation of lipofibrosis at the branchial region might have initially formed as a small connective tissue thickening which subsequently due to constant contact of the parasite might have developed as a larger thickening as lipofibrosis. Hyperplasia in some situations represents an adaptation by the organism to protect the underlying tissues from any irritant (Meissner and Diamandopoulos, 1977). Hyperaemia was ascertained at the site of attachment of the parasite which in general had not been previously seen in young specimens. The parasite that attaches or settles on the host body, at first, causes localized inflammatory changes, but with time, they assure a different or diffused character. The changes always begin with hyperaemia in the angles between adjacent sides at the site of attachment and then move towards deeply situated area.

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