Problem or Just a Weak Swimmer?

Dear Claire:

Yes, from the swimming behavior you describe it certainly does sound as though Sydney is having a problem with negative buoyancy. This can be either due to an underinflated swimbladder or to ascites, a buildup of fluid within the coelom or abdominal cavity (often associated with kidney problems). If your female, Sydney, is not bloated then I suspect that the negative buoyancy is the result of an underinflated swimbladder.

As in many other bony fishes, the seahorse’s gas bladder functions as a swim bladder, providing the lift needed to give them neutral buoyancy. In essence, the swim bladder is a gas-filled bag used to regulate buoyancy. Because the seahorse’s armor-plated body is quite heavy, this organ is large in Hippocampus and extends well down into the body cavity along the dorsal boundary. It will have a whitish to silvery appearance and is a simple, single-chambered sac that begins at the bend in the neck and extends to about 1/3 of the length of the coelomic cavity (Bull and Mitchell, 2002).

When the swim bladder is inflated with just the right amount of gas, the seahorse achieves neutral buoyancy, which just means that if neither tends to rise or sink. It is thus weightless in the water, with the buoyancy from its gas bladder exactly canceling out the pull of gravity. This facilitates swimming and makes holding its body upright effortless.

But a number of things can disrupt the normal functioning of the gas bladder and the gas gland that inflates it, resulting in either too little or too much gas being secreted into the swimbladder. When too much gas is secreted into the swimbladder the seahorse becomes too buoyant. Hyperinflation of the swimbladder thus results in positive buoyancy and the tendency to float. Likewise, if too little gas is secreted into the swimbladder, exactly the opposite occurs in the seahorse becomes too heavy. Under inflating the gas bladder therefore results in negative buoyancy and the tendency to sink.

So I think you are correct, Claire, and that your female is struggling with an underinflated swim bladder or gas bladder. The resulting negative buoyancy makes it difficult for the armor-plated seahorse to swim normally, rise from the bottom, or even hold itself erect. An underinflated swim bladder is sometimes a problem a seahorse can correct on its own, as more gas is gradually secreted into the swim bladder from the gas gland. However, this is a gradual process and may take days to accomplish. But if Sydney has been this way for an extended period, lurching from hitching post to hitching post and making crash landings frequently, then I suspect some sort of the swim bladder disorder.

For example, an underinflated gas bladder can also result from infection, and I have seen several cases of swim bladder disease that were associated with internal parasites (digenes), which sometimes also contribute to generalized weakness, and I would ordinarily recommend treating your seahorses with a good antiparasitic that is effective against internal parasites, such as metronidazole or praziquantel as a precaution.

But I know you have recently completed treating your main tank with metronidazole/praziquantel, Claire, so you have already covered that possibility. Hopefully, Sydney will be able to correct the situation herself in time, I gradually releasing more gases into her swimbladder via the gas gland. If not, you can always consider administering an antibiotic orally via gutloaded shrimp, but I am not entirely certain if that would be appropriate or helpful in a case like this.

In the meantime, just make sure your pH and dissolved oxygen levels are on the mark, keep your temperature in the comfort zone for H. angustus, and maintain optimum water quality.

Best wishes with all your fishes, Claire!

Respectfully,
Pete Giwojna

Post edited by: Pete Giwojna, at: 2009/07/08 21:34

Dear Claire:

Yes, I do agree that Sydney’s problem is most likely due to an underinflated swim bladder, and since treating the seahorses with metronidazole/praziquantel did not resolve her problem, the malfunction with her swim bladder is apparently not due to internal parasites. Sometimes bacteria are involved in swim bladder disorders, Claire, so you might consider administering antibiotics orally via gutloaded shrimp, but I really have no idea if that would be helpful at all in this case.

This could be a problem that began shortly after birth. Newborns that miss the opportunity to gulp air at the surface while their pneumatic duct is still open — perhaps as the result of an oily or greasy film at the surface of the water — suffer from underdeveloped swim bladders. As they grow and become heavier, they sink to the bottom and are unable to swim or feed normally.

If denied access to the surface to inflate their swim bladders, the fry behave normally while they are small and their weight is still negligible. But over the weeks, as they grow and put on weight, their underdeveloped swim bladders and inability to achieve neutral buoyancy increasingly handicap them. Once they gain a little weight, they sink like rocks. Unable to swim, they are reduced to slithering along the bottom on their bellies and are commonly referred to as sliders. This deficiency does not become apparent until the fry are several weeks old. Needless to say, this hinders their swimming ability and severely limits their feeding opportunities, delaying their growth and development, and rendering entire broods useless. In several cases, the problem was traced back to an oily film on the surface of the nursery tank, which prevented the newborns from filling their swim bladders with air (Silveira, 2000). A protein skimmer will prevent this by removing filmy surface layers and surfactants in general.

So it’s possible that Sydney has had an underdeveloped or underinflated swim bladder from an early age. Ordinarily, seahorses can overcome an underinflated swimbladder simply by depositing additional gas into the bladder with the aid of the gas gland. The gas gland provides an acidic environment, and under acid conditions, hemoglobin releases oxygen in the gas gland, which is then deposited in the lumen of the swim bladder via diffusion. Likewise, carbonic acid dissociates into CO2 + H2O within the gas gland, liberating carbon dioxide, which is also deposited in the lumen of the swim bladder through diffusion. (The swim bladder of seahorses is filled primarily with oxygen, supplemented by carbon dioxide; Evans, 1998.) In this way, the gas gland can gradually reinflate the swimbladder to achieve neutral buoyancy, but for some reason this does not appear to be happening with Sydney.

Occasionally, this is because certain parasites and/or bacteria are presenting the gas gland or swim bladder from functioning properly, as in the following case reported by Paul Anderson in which undesirable copepods may have played a role in the problem:

<Open quote>
Hi folks,

I’ve been having some unusual health circumstances arise from my research seahorse population that I thought I’d share with you to see if anybody has encountered any similar problems.

First, I have a problem with harpacticoid copepods in my seahorse tanks. They seem to have gotten in everywhere; all system and quarantine tanks. I’m reasonably sure that they are coming in from live brine shrimp feedings.

Most of the animals seem unaffected by the copepods, but when picking up a seahorse it’s very common to see several of these copepods crawling on the animals. Most of the animals have not developed lesions as a result, but a few have, and I suspect the copepods for contributing to such problems.

Curiously, at least two animals have come down with negative buoyancy problems (sinking to the bottom, unable to keep upright or swim up). Over time, their swimbladders have become so swollen that it is markedly noticeable from the external profile of the animal. We have necropsied both animals that have presented as such and have found HUGE digenes in the swimbladder, coupled with a brownish exudate that, under microscopy, is loaded with bacteria and (presumably) digene eggs. The exudate was examined and cultured and, unfortunately, stained Acid-Fast Base positive and grew on Lowenstein-Jensen Media (suggesting Mycobacterium infection). There are probably other bacterial spp. present but I don’t have that information with me; this case is being worked up with our Veterinary Team here at the Department.

Here come the questions/thoughts:

Because digenes have an indirect life cycle, I suspect that either the copepods or the Artemia themselves are serving as intermediate hosts. If only the copepods are serving as intermediate hosts, the seahorses may be ingesting them when feeding on frozen mysids that the copepods may have attached to prior to ingestion. To help eliminate this problem, I am treating all tanks with Dimilin to eradicate the copepods. Initial treatment did reduce numbers, but the copepods are constantly being re-introduced through the live Artemia feedings. I am not treating the Artemia holding tank with Dimilin because Dimilin may also kill the Artemia.

I have more recently been thinking about biological controls. I was initially hesitant to include other spp. in my tanks to minimize experimental variability, but this problem may merit the introduction of something like a cleaner wrasse or similar animal in each tank to keep copepod numbers down (and off the seahorses).

What are your thoughts? Has anybody had any similar problems? Has anybody tried keeping seahorses with cleaner-type fish?

Looking forward to your responses. Thanks!

Paul Anderson
Ph.D. Candidate/Alumni Fellow
Department of Fisheries and Aquatic Sciences
University of Florida
<close quote>

So it’s very difficult to say precisely what could be causing Sydney to have a problem like this, and your best option may simply be to wait and see if Sydney is eventually able to correct the problem herself the natural way.

I would hesitate to suggest any sort of aggressive treatment without an understanding of exactly what is happening, and right now I am clueless in that regard, Claire…

Best wishes with all your fishes.

Respectfully,
Pete Giwojna

Dear Claire:

I’m sorry to hear that Sydney’s feeding difficulties due to weak snick and swimming problems associated with negative buoyancy have gradually been getting a little worse, rather than improving. It sounds like you’ve been doing a fine job of keeping her eating with the soft-body brine shrimp but that lately it has become increasingly difficult to see that she gets good nourishment.

Yes, I normally recommend treating the main tank with hyposalinity when stubborn cases of weeks neck don’t respond to other measures. In this case, however, I feel that the hyposalinity might be counterproductive since Sydney’s feeding problems are compounded by the difficulty she is having in supporting herself and maintaining her upright posture. Hyposalinity would worsen that problem by making the seahorse less buoyant in the low salinity water, which is not as dense as normal salinity seawater.

Instead, I would concentrate on getting good nutrition into your female. The key to resolving weak snick is to keep the seahorse eating or otherwise provide it with nourishment until it has recovered sufficiently to resume feeding on its own normally. This can sometimes take several weeks or months, and if the seahorse can no longer get enough to eat on its own, even by inhaling the soft-body adult brine shrimp, then it’s time to consider force-feeding (i.e., feeding by hand) or tube feeding the seahorse instead in order to provide it with nutritional support.

Before you resort to the more invasive tube feeding, Claire, I suggest that you try force feeding Sydney by hand. By handfeeding in this case I mean holding one entire, intact (whole and unbroken) frozen Mysis that you have carefully thawed in your fingertips and then placing the tail of the Mysid directly in the mouth of the seahorse. Many times the seahorse will simply spit it out again, but often if you can insert the Mysis into her open mouth far enough, her feeding instincts will kick in and take over so that she slurps up the frozen Mysis almost reflexively. That’s a much less stressful and less invasive method of force feeding a seahorse that sometimes works well (especially if the seahorse is accustomed to being hand fed and doesn’t shy away from the aquarist). Force feeding the seahorse by hand sounds much more difficult than it actually is, and seahorses will often respond well to this method of feeding, Claire. Even the professional curators at the large public aquariums will use this technique when their highly prized (and very expensive) seadragons are experiencing problems with weak snick, as explained in the discussion thread below:

<open quote>
Has anyone had problems with syngnathids having a problem
getting food into their mouths? Currently I have a few ribbon
pipehorses (seadragons) that have lost the ability to take in food,
either live or frozen when attempting to eat. It is as if they have
lost the suction power when they attempt to snap up the food. They
can see the food and chase it and attempt to eat but don’t have
enough snap to create the suction needed to get the piece of food
into its mouth. Even when putting the affected animal in a smaller
tank with lots of food, it still can’t get the food in.
This condition seemed to develop even though the ribbon
pipehorses were eating aggressively before the problem started. They
were mainly eating frozen mysis and occasionally were fed live mysis.
I was thinking that possibly the diet of mainly frozen mysis could
not be enough for them nutritionally as they were developing??? Not
sure.
I have occasionally seen this problem before in weedy and
leafy seadragons as well as some seahorses.
Has anyone else had this problem? Any ideas of what may
cause this problem? Any ideas on how to get them to eat again? Has
anyone had luck with force feeding seadragons to get them to eat
again?

Thanks,
Leslee Matsushige

Leslee Matsushige (Yasukochi)
Assistant Aquarium Curator
Birch Aquarium at Scripps
Scripps Institution of Oceanography
University of California San Diego

Hi Leslee,
Over the years, we have seen mouth problems develop in some of our dragons. Sometimes it’s attributed to injury. Sometimes we don’t know what causes it, but we are often successful in getting them to recover on their own with just supportive feedings until we observe that they are back to catching food normally. Sometimes this can take a long time…as in a month or two of force feedings before they are back to catching enough on their own to sustain themselves.
Although I have not had experience force feeding ribbon dragons, I have both force fed and tube fed leafy and weedy seadragons. Typically, we force feed numerous frozen mysids to a sick dragon up to 3 times a day. By force feeding, I mean that we very gently place a mysid in the mouth of the animal and then lightly hold a finger in front of it so that it can’t easily spit out the food. Usually they learn pretty quickly that they are getting food this way and start to slurp mysids up as soon as they are put in their mouth. I usually try to get 6-10 mysids in per feeding. It takes good eyesight and a steady hand to make sure you don’t injure their mouth with this method. We have also tube fed using a thick slurry of cyclopeeze or pulverized and moistened pelleted food…usually giving around .3cc per feeding…though it’s dependent on the size of the animal. I think we usually use a 2-3mm french catheter cut down to fit on a small syringe. Again we do this 3 x day. We find that the animals do better with the frequent feedings and usually they go right back to searching for food after being released.
Teryl Nolan
Aquarium Supervisor
SeaWorld Florida

Hi Teryl,
Thanks for your response to my posting. We are currently trying to tube feed one of our leafy seadragons. We have been feeding it 1x/day for now to see how it handles the feedings.
I was wondering what was the size of the seadragon that you feed .3cc of the food slurry to? Our leafy is about 10-11 inches in length. I am not sure of the amount to feed. Since we are feeding only 1x/day we are trying .6cc per feeding.
Do you find force feeding or tube feeding to be better in certain situations? Our leafy still attempt to get the food but can not snap its jaw with enough force to get the food into its mouth.
When you force feed the seadragon do you hold it upsidedown? What do you use to put the mysid in its mouth? If you could give more details about force feeding that you think might be helpful, can you pass this on?
Your response has been helpful!
Thanks,
Leslee

In a message dated 7/16/2009 1:20:44 P.M. Central Daylight Time, [email protected] writes:
Hi Leslee,
We usually feed our full-sized leafies just .3cc at each feeding. I don’t know that you can’t go higher, we just don’t. I try to be conservative and part of my philosophy about having to force feed them is that since they naturally tend to graze on food all day long, I like to feed them smaller amounts more frequently.

In our experience, the dragons usually go back to their normal routine after a tube or force feeding. If they were actively looking for food, but just not following through and eating it, that’s what they go back to. If prior to the feeding, they were acting pretty lethargic…maintaining a stationary position on the water, usually facing a wall, and not showing any interest in feeding…then we’ve noticed that after they get a little energy from the force feeding, they often come out, act a little more normally, and even show signs of hunting for food. The reason we started force feeding the sick ones 2-3x a day years ago, is because we see such a dramatic turn around in their behavior after they have gotten some food. If we don’t follow it up with another feeding that day, then they seem to lose steam and go back to their wall-facing behavior.

I’ve come to the point that I believe it’s better to force feed than to tube feed (unless I need to tube with an oral medication or the dragon won’t take the force feeding). If you have the very small mysids available because you purchase live or culture your own, that’s what I prefer to use. We freeze our mysids prior to feeding them out. If you lightly restrain the dragon, in an upright position, but completely under the water, I find it’s easier to use latex gloves and very carefully insert a small mysid into the dragon’s mouth tail first using my fingers. We can usually get them to eat 10-20 per feeding. They will usually slurp it up pretty quickly. Sometimes they spit them out the first couple times though. In which case, I lightly hold my finger in front of their mouth until they’ve swallowed the mysid. That keeps them from spitting them out completely…usually. We have a few that we hold under water and pour mysids in front of, then we just move them directly in front of the food and they slurp them up. I think they probably get more from the whole mysids than from the gruel.

We don’t even move them off exhibit unless there are other health issues. We just lean over the side of our system and handle the dragons quickly beneath the surface. Then release them. I think it is much less stressful on the animals if you don’t have to move them. They tolerate this extremely well in my experience and we have had numerous that required supplemental feedings for awhile, but then recovered.

I hope this helps!

Teryl Nolan
Aquarium Supervisor
SeaWorld Florida
<close quote>

All things considered, Claire, I think I would avoid hyposalinity in your case and concentrate on hand feeding Sydney individual Mysis as described above to provide her with nutritional support. If force feeding your little female by hand proves to be impractical, then tube feeding is probably the next best option at this point. Let me know if the tube feeding becomes necessary, and I can provide you with some additional instructions to help guide you through the procedure.

Best of luck getting good nutrition into Sydney until this problem can resolve itself.

Respectfully,
Pete Giwojna