I understand that you have a seahorse that seems to be having seizures, and that darkens in coloration where it is experiencing these seizures.
After examining the video you provided, the spasmodic movements of the seahorse are similar to the muscular contractions that a pregnant seahorse undergoes when giving birth. However, the seahorse in the video appears to be a young female, so its contortions are clearly not birth spasms.
It is possible for seahorses to exhibit seizure-like symptoms when they have suffered brain damage or a head injury or when they had been exposed to toxic substances.
For example, we sometimes see neurological symptoms like that under hypoxic conditions when seahorses have been deprived of oxygen for too long.
Erratic behavior, neurological symptoms, and seizures can also result when a seahorse is suffering from major organ failure, particularly if the liver and/or kidneys are involved. Seahorses have primitive aglomerular (having tubules but no glomeruli) kidneys, whose primary function is to filter waste from the blood (Evans, 1998). The seahorse’s kidneys are also hard at work maintaining its blood and tissues at the proper osmotic concentration at all times (Seahorse Anatomy, 2004). This is necessary because seahorses live in seawater that is four times saltier than their blood and body fluids, and they are constantly losing water via osmosis across their gills, through their skin, and in their urine as a result (Kollman, 1998). Marine fish risk dehydration because salt cannot diffuse into their bodies but water is being continual lost to the concentrated seawater that surrounds them ((Kollman, 1998).
To compensate for this, marine fish drink seawater continuously to replace lost fluids and then excrete the excess salts they have taken in through the kidneys, in their feces, and from their gills (Kollman, 1998). As a result, their kidneys produce a very concentrated, salty urine (Kollman, 1998). Expelling excess salt this way is very energetically demanding and comes at a high metabolic cost because the salts must be pumped out of their bodies against a strong pressure gradient (Kollman, 1998).
If your female’s kidneys have failed or been impaired as a result of an infection of some sort, she could be suffering from dehydration or a buildup of toxins in her system, either of which could cause the sort of seizure-like behavior and symptoms your female is now displaying.
The seahorse’s liver is also different than that of other vertebrates. Like many fishes, seahorses do not have a separate pancreas. Instead pancreatic tissue is dispersed throughout the liver, which thus performs double duty, carrying out the functions of both the liver and the pancreas (Seahorse Anatomy, 2004). For this reason, the fish liver is usually referred to as the hepatopancreas. The seahorse’s hepatopancreas is basically a big digestive gland (Seahorse Anatomy, 2004). It is a large organ that secretes enzymes and produces bile to aid in digestion and food absorption. It also stores food energy in the form of glycogen and plays a vital role in the detoxification of blood. If your seahorse’s liver was impaired and can no longer perform that role, toxins would again build up in the blood and tissue of your seahorse and could then cause the sort of symptoms your female is showing once they build up past a certain point. The most common cause of such liver problems is hepatic lipidosis or fatty liver disease.
Because of their lazy lifestyle, captive seahorses that are feed a diet that’s excessively rich in HUFA (highly unsaturated fatty acids) and other lipids are vulnerable to a debilitating affliction commonly known as “fatty liver disease” or hepatic lipidosis. When the seahorse’s liver or hepatopancreas becomes infiltrated with fatty deposits as a result of hepatic lipidosis, it interferes with the organ’s ability to perform these vital functions and that has dire consequences for the affected seahorse.
If your female was an old warhorse that’s getting up in years, such problems with her liver or kidneys could simply be the result of the inevitable aging process. The aging process is always associated with increased morbidity and mortality, and seahorses are no exception to be sure. As seahorses age, they become increasingly vulnerable to certain conditions that did not trouble them when they were younger. This often manifests itself as an increased incidence of gas bubble disease (particularly pouch emphysema and subcutaneous emphysema), chronic wasting, and certain types of cancers. For example, I know of several older seahorses that developed malignant neoplasms, including tumors of the small intestine with liver metastasis and a case of a fibrosarcoma of the pouch. Specimens with anorexia and chronic wasting often have distended gall bladders, fatty livers, and sunken eyes.
Hepatic lipidosis in the most common of these age-related conditions. Of all the necropsies Dr. Martin Belli has performed on hobbyist’s seahorses, fully 38% of them had fatty livers (Belli, per. com.).
As I mentioned, because of their sedentary lifestyle, our galloping gourmets are susceptible to this debilitating affliction when they are given a diet that’s excessively rich in HUFA (highly unsaturated fatty acids) and other lipids. Mature seahorses that are no longer breeding are at greatest risk from hepatic lipidosis. Young seahorses need a high-fat diet to sustain their rapid growth and development, and breeding pairs that are churning out brood after brood of fry likewise need all the energy they can get. But once they reach sexual maturity, their growth rate slows markedly, and nonbreeding adults that receive a high-fat diet will begin to store excess fat in specialized cells called adipose tissue (Tamaru, Sep. 2001). Eventually these fatty deposits will begin to infiltrate the liver cells, hence the name fatty liver disease (Tamaru, Sep. 2001).
In severe cases, adipose tissue can become so thick that it can literally hides the internal organs, cloaking them within a cocoon of fat, and distending the abdomen (Tamaru, Sep. 2001). When the seahorse’s liver or hepatopancreas becomes badly infiltrated with fatty deposits, it interferes with the organ’s ability to perform its vital role in digestion, food absorption, and detoxification of the blood, which can result in the sort of unusual behavior and seizure-like symptoms your female is suffering from.
Hepatic lipidosis is one of those conditions you can’t do much about after the fact, so the best way to address such problems is to concentrate on preventing them in the first place. Avoiding overfeeding, fasting adults once a week and using relatively low-fat enrichment products such as Vibrance II for mature seahorses that are no longer breeding are simple ways to prevent fatty liver disease.
In summation, those are some of the things that can cause seahorses to exhibit seizure-like behavior, but I don’t know of any of them apply in your case. I’m very sorry I could not be more helpful in this instance.
Pete Giwojna, Ocean Rider Tech Support