My experience leads me to believe that when fish are stressed, they swim around the aquarium completely out of control, with clearly visible "stress bars," hitting the glass and sometimes, after losing all energy, lying on the bottom of the aquarium or hiding, breathing with great difficulty. Frequently, their eyes droop from swimming sideways and scratching their retinas on the bottom of the aquarium, which is due to an excess of one of their hormones, cortisol.
In Discus, cortisol is the main hormone associated with the physiological stress response. Empirically, and before talking and discussing with different biologists, I always thought it was a hormone produced in the fish's brain, but in reality, it is not, contrary to my theory. The stimulus of catching a fish with a net and capturing it, its transport, lack of oxygen, sudden changes in water, or territorial conflicts are perceived by the nervous system located in the brain. This stimulus in the brain activates the HPI axis. You might ask: "But what is HPI?" These are the three letters of an axis composed of the hypothalamus (a small region of the brain located just below the thalamus that connects the nervous system to the endocrine system to maintain the body's internal balance), the pituitary gland (a small gland located at the base of the brain that controls most of the body's other glands), and finally, the interrenal system, the main stress response system in fish, where cortisol is produced.
The next article on this blog will be about what we do and how we save about 90% of Discus fish with excess cortisol.So, who produces cortisol ? Cortisol is produced primarily by interrenal cells, located in the kidney tissue.Discus obviously live with cortisol. However, it's important to understand the various stages of this hormone.Elevated cortisol for a few minutes/hours = normal adaptive response, as usually happens in our Discus.High cortisol for days/weeks = chronic stress, potentially harmful, leading to fits of madness that can cause death.
Episodes of acute stress adjust the immune system; however, chronic stress and high, continuous levels of cortisol suppress the immune system, making fish highly susceptible to infections from parasites, bacteria, fungi, but most deadly are "panic" attacks.
We know that Discus are among the most stressed fish. This is particularly interesting because capture, transport, sudden water changes, poor water quality, lack of oxygen, high density, territorial conflicts, and handling can trigger a stress response and raise cortisol levels, which, as I wrote before, when it happens for several weeks, can eventually lead to the fish's death. It's important to say that this remains my explanation for the death of fish with these "panic" attacks, and it is not scientifically proven. In the past, I managed to collect some fish with the first symptoms of "excess cortisol," eventually sending them to the laboratories of Manaus Aquarium, a pharmaceutical company that produces fish medications in Germany, along with other fish showing symptoms for Hector Gutierrez to observe. Neither of them found anything wrong with the fish's brain when observing them under a microscope; however, at the time, both stated that the fish were free of parasites, but the renal system was not examined, which is now scientifically proven to cause kidney problems. Cortisol.
The next article on this blog will be about what we do and how we save about 90% of Discus fish with excess cortisol.
