Parasites are organisms that live in other organisms (hosts), both on the surface of the body and in the body and take advantage of the host. Fish as aquatic biota cannot be separated from parasite infestations. Some cases of parasite infestation in fish, both consumption and non-consumption fish have been reported in Indonesian waters. Some parasitic groups in fish can also cause disease in humans (zoonoses). As has been reported the Anisacis worm infestation in canned fish. This worm if eaten by humans can cause several diseases in the digestive organs.
One of the preventive efforts to overcome parasitic infestations is through the process of identifying parasites, so that a proper diagnosis and control can be established. An important first step in carrying out the identification process of fish parasites is the preparation and observation of parasites as pathogenic agents.
Parasites can be collected and prepared in freeze-dried form. This technique is carried out with the working principle of preserving the body structure of the parasite without causing damage or deformation. Furthermore, the parasites which have undergone the freeze-dried and fresh form stages are processed in the fixation stage, namely preservation in the fixative solution. Parasitic fixation can be done in ethyl-alcohol (ethanol), 10% glycerin alcohol, 70% alcohol and 40% formalin (aqueous formaldehyde). The principle of giving fixative solutions is to remove the water content from the organism. The volume of fixation solution should be 10x more than the size of the parasite that will be preserved. Fixation solutions can be replaced several times to avoid decay.
Furthermore, fixed parasites can be directly observed under the microscope and the coloring process is carried out to see in more detail the organs they have. The commonly used parasitic dye is Acetic Carmine. Giving coloring, facilitates the observation of parasites in more detail. However, this cannot be done on parasites from the Nematode or Branchiura worm groups because the administration of the dye will cause color accumulation in the organs in the parasite, resulting in obscurity in the organs they have. Giving dyes can be done on the worm parasites of the Trematode, Cestoda, Acantocephala and Hirudinae groups. The accuracy of the preparation technique is very important in obtaining clean specimens and facilitating the observation process.
Author: Putri Desi Wulan Sari, S.Pi., M.Sc.
(Lecturer in the Department of Fish Health and Aquaculture Management – FPK UNAIR)