Bubble on Tail

Dear Sir:

My best guess is that your initial diagnosis is correct and that the regimen of Diamox (the tablet form of acetazolamide) you are administering is the best way to resolve the problem. The tail bubble sounds like subcutaneous emphysema and I would give the acetazolamide a little longer to do its work (it sometimes takes 7-10 days to resolve a stubborn case of tail bubbles).

The recommended dosage is 250 mg of acetazolamide per 10 gallons with a 100% water change daily, after which the treatment tank is retreated with acetazolamide at the dosage indicated above (Dr. Martin Belli, pers. com.). Continue these daily treatments and water changes for up to 7-10 days for best results (Dr. Martin Belli, pers. com.). Dr. Belli reports nearly a 100% success rate in treating GBS when this dosage is maintained for the full treatment period.

As you know, Gas Bubble Syndrome (GBS) is believed to be caused by gas emboli forming within the tissue of heavily vascularized portions of the seahorse’s anatomy — the placenta-like brood pouch of males, the eye, the muscular prehensile tail — and it can take several different forms depending on where the bubbles or emboli occur. When it occurs in the brood pouch of the male, chronic pouch emphysema or bloated pouch results, leading to positive buoyancy, which is by far the most common form of GBS. When it occurs in the capillary network behind the eye (choroid rete), Exopthalmus or Popeye results, and the eye(s) can become enormously swollen. When it affects the capillary network of the gas bladder (the rete mirabile), hyperinflation of the swimbladder occurs, resulting in positive buoyancy. When it affects the tail or snout, external gas bubbles (i.e., subcutaneous emphysema) form just beneath the skin and look like raised blisters. When intravascular emboli occur deep within the tissue and occlude blood flow, generalized edema results in the affected area. Or extravascular emboli may cause gas to build up within the coelom, often resulting in positive buoyancy and swelling or bloating of the abdominal cavity (internal GBS).

The prehensile tail of the seahorse is often affected when conditions are favorable for the formation of such gas emboli because it has a rich blood supply via the dorsal aorta and caudal vein and because the tail is the site where seahorses tend to store their limited fat reserves (the extravascular seed nuclei or emboli that trigger GBS form most readily in adipose tissue due to the higher solubility of certain gases in lipids than in aqueous tissues). Intravascular bubbles are seen in both the arterial and venous circulation, but with vastly greater numbers detected in venous flows (venous gas emboli). The far more numerous venous bubbles are believed to first form in lipid tissues draining the veins. Lipid tissue sites possess very few nerve endings, possibly masking critical insults at first, and veins, which are thinner than arteries, appear more susceptible to extravascular gas penetration.

In seahorses, oxygenated blood is delivered to the tail via the dorsal aorta, a major artery running the length of the body below the spine, and CO2-laden water is returned via the caudal vein which runs along the inside of the tail. In seahorses, venous bubbles often form at the most distal portion of the tail where the oxygen tension is lowest.

So I suspect you are indeed dealing with a form of GBS known as subcutaneous emphysema or tail bubbles. If the Diamox baths have not been producing the desired results, you may want to consider administering the Diamox orally instead, as explained below.

Administering Acetazolamide Orally

I have found that acetazolamide is often more effective when it’s ingested and administering the medication orally allows you to treat the seahorse in the main tank where he’s most comfortable and relaxed.

If you can obtain a small syringe with a fine needle, the acetazolamide solution can simply be injected into feeder shrimp or even frozen Mysis. Mic Payne (Seahorse Sanctuary) used this method of administering acetazolamide successfully when he had recurring problems with GBD due to maintaining a population of Hippocampus subelongatus in shallow tanks only 16-inches (40 cm) deep:

"Seahorses maintained in this system are susceptible to gas bubble disease. Specimens with bubbles around the eyes or under the epidermis of the tail are readily treated with acetazolamide (Diamox tablets 250 mg). Mix a very small amount of crushed tablet with water and inject it into several glass shrimp that are then frozen. These are then fed to the target animal at the rate of two per day for four days. Bubbles disappear on the second day."

Hawaiian volcano shrimp or red feeder shrimp (Halocaridina rubra) work great for this. If a fine enough needle is used, they will survive a short while after being injected — long enough for their twitching and leg movements to attract the interest of the seahorse and trigger a feeding response.

Leslie Leddo reports that a 1/2 cc insulin syringe with a 26-gauge needle was ideal for injecting frozen Mysis or live red feeder shrimp. They plump up when injected and ~1/2 cc is about the most of the solution they can hold. There bodies will actually swell slightly as they are slowly injected and excess solution may start to leak out. The 26-gauge needle is fine enough that it does not kill the feeder shrimp outright; they survive long enough for the kicking of their legs and twitching to assure that they will be eaten.

In summation, I would continue treating your seahorse with Diamox but perhaps consider administering it orally instead of as a bath.

If you can provide me with one or more good pictures of the suspicious tail bubble, I will be happy to look them over and see if it appears to be the usual sort of subcutaneous emphysema I am familiar with. Just insert the photos into an e-mail and send it to me off list ([email protected]).

Best of luck clearing up the tail bubble and restoring your seahorse to good health!

Respectfully,
Pete Giwojna