Probiotics are supplements that protect and maintain fish health, especially the health of reproductive organs. This supplement is believed to protect and help the “good” bacteria in the digestive tract from harmful pollutants by absorbing, digesting, and releasing them into harmless substances. Some heavy metals become hazardous materials in the aquatic environment. It can be absorbed directly into the digestive tract and neutralized immediately by probiotics.
Waste from industry, agriculture, transportation, and human activities is the main source of heavy metal in the aquatic environment. This material is often used during the manufacturing process in industry and becomes the source of the most water pollutants. Environmental pollution due to heavy metals has become a serious threat to the life of the fishes. The main danger is due to the process of absorption and deposition of heavy metals in the fish body. The danger can be from its nature which is difficult to decompose and produces highly reactive free radical molecules.
A small amount of heavy metals plays a role in decreasing the metabolic function of the body’s cells, for example mercury, cadmium, copper, lead, which are toxic to organisms. These heavy metals can damage the structure and function of the gills, liver and reproductive organs of fish, including reducing the ability for fertilization process and fish production.
The use of microorganisms to reduce the impact of aquatic pollutants is an alternative method that can be used to restore the health of fish contaminated with heavy metals. Many microorganisms have the ability to eliminate the toxic effects of heavy metals, some of them are lactic acid bacteria, including Lactobacillus sp. Lactic acid produced by these bacteria can suppress the growth of “bad” bacteria by making the environment condition more acidic. Furthermore, these bacteria can clean and neutralize heavy metals inside the digestive tract through the bond formation between heavy metals and bacterial cells, followed by its excretion through feces. Lactic acid bacteria can also reduce harmful substances that enter the digestive tract of fish by involving enzymatic activity produced by bacteria. The enzymatic activity accelerates the modification of toxic pollutants by changing its chemical structure to become harmless or non-toxic.
Fish farming carried out in reservoirs or ponds where the water comes from rivers contaminated with heavy metals need special attention. The usage of this water can affect the growth and development of fish. The use of ordinary fish food may not be able to overcome the negative impacts caused by pollutants. For this reason, supplementary feed containing a consortium of probiotics is recommended, so that it can clean, neutralize and increase the growth of “good” bacteria in the digestive tract of fish exposed to heavy metals. The feed supplements derived from probiotics have also been shown to restore and improve the quality of fish sperm exposed to heavy metals.
Based on the test results, it is known that supplementary feed containing probiotics can improve the reproductive health of fish exposed to heavy metals. This is supported by the change of testicular layer to become thicker and the seminiferous tubules to become elongated. The exposure to various metal concentrations decreased the thickness of the testicular layer and the length of seminiferous tubules compared to control.
Furthermore, the test of supplementary feed containing vitamin C only and containing both probiotics and vitamin C in contaminated fish did not show any difference in seminiferous tubule length compared to control. However, its size decreased when exposed to high concentration of heavy metals (Cd, 0.6 ppm).
The test of cyst and germ cells in the fish testicles showed a change in the size. Cyst is the part of the seminiferous tubules that contain germ cells (spermatogonium, spermatocytes, and spermatocytes). These cells grow and develop in the cyst. The size of the cyst corresponds to the growth of the germ cells inside. The results showed that exposure to heavy metals decreased the diameter of cysts and germ cells. Administration of probiotic supplements increased the cyst and germ cells diameter of the fish after heavy metal exposure, however giving the vitamin C alone or combination of both vitamin C and probiotics had no effect. Thus, it can be concluded that feeding containing probiotic supplements is better to improves the reproductive health of fish (seminiferous tubule length, testicular layer thickness, cyst and germ cells diameter) contaminated with heavy metals compared to other supplements (vitamin C alone or combination of both vitamin C and probiotics).
Author: Alfiah Hayati
Details of the research can be viewed at: http://www.envirobiotechjournals.com/article_abstract.php?aid=11068&iid=323&jid=4
