Kemampuan adaptasi ikan gobi amfidromus terhadap perubahan salinitas

Abstract

Each group of fish has its specific migration pattern, which is commonly related to its life cycle. Amphidromus is one of the most common forms of diadromous migration in fishes. Gobies is a group of fish whose members are mostly amphidromus. In the process of their amphidromus migration, gobies have to adapt to various environments, from zero salinity in fresh waters, to an environment with a  totally different level of salinity which is as high as 34ppt, in marine waters or vice versa.  To cope with this, gobies have to prepare their physiological functions so that they can immediately adapt well to their new environment with an osmotic pressure that is very different from the previous environment. Gobies larvae hatching in freshwater rivers must migrate to seawater within a few hours to survive.  Larvae failing to reach seawater will not undergo metamorphosis and will eventually die. Larvae that reach marine waters will grow and develop into post-larvae, and at this stage will migrate back to fresh water. The motivation to migrate from sea to freshwater is related to an alteration in the endocrine system, which play an essential role in controlling the osmotic balance of the fish body migrating from sea water to fresh water. The migrating postlarvae gobies undergo all processes of preparation for their physiological functions and adjusments in  osmoregulation system to anticipate the drastic change in the osmolality gradient of their environment. The metamorphosis process of all external and internal organs, including the fins, cranium, digestive system and osmoregulation system, takes place simultaneously during the migration process.  Most gobies are true amphidromus fish, but they are also superb osmoregulator fish.