Fish Diseases and Management

2.2.5 Hyperplasia

It is an abnormal increase in the number of cells with consequent enlargement. Hyperplasia is a much more generalised phenomenon in fish epidermis than that of higher animals. Epidermal hyperplasia has been found to be much more frequent at low temperature in all the species so far studied.

1) Dermal and hypodermal changes

Stratum compactum is poorly endowed with blood supply, because of that the major pathological changes take place in the stratum spongiosum and the hypodermis that the .

The inflammatory response exhibited by these layers of skin is triphasic, comprising a vascular, an exudative and a cellular component, with the relative time span of these phenomena being directly correlated with environmental temperature. Chronic inflammation in fish skin manifests all of the features found in higher animals including sensitization, caseation and cell mediated immunity and the development of giant cells.

a) Vascular

It refers to the blood circulatory system or blood capillary. The blood flow is disturbed.

b) Exudative

Blood capillaries consist of minute holes known as fenestrae – when the capillaries are dilated. There is release of fluid through the fenestrae and hypertrophy ( a non-tumorous enlargement of organ mainly due to increase in cell size ) normally occurs in this region. All the blood components exudate.

c) Cellular component

The cellular component changes when the cell component is affected.

In some case the dermis or hypodermis layer will be directly damaged by specific type of physical damage. Mechanical injury or parasite piercing and any damage in the skin leads to the formation of ulcer.