Re:Micro Mini Star on Seahorse!

Pete Giwojna

Dear Tammy:

Thanks for the update! It’s good to hear that the tiny Asterina starfish was just hitchhiking and didn’t cause any problems while it was attached to yourseahorse.

Yes, although uncommon, it is possible for a mature female in breeding condition to become egg bound. But this is unlikely to happen when there is a receptive male available to receive the clutch of eggs, and even when there not a stallion that’s eager to get pregnant ready and waiting, a female with ripe eggs will simply release the clutch of eggs before it becomes a problem.

Seahorses are fractional spawners. Females maintain a spiraling assembly line of developing oocytes (egg cells) at all times, only a portion of which are fully mature and are released at each mating (Vincent, 1990). This differs from the reproductive strategy of most fishes, which are multiple spawners that release all their eggs each time they mate and then start over, maturing an entirely new clutch of eggs from scratch for the next spawning.

The structure of these production-line ovaries is unique to syngnathids. They are paired organs, which join to form a single oviduct (the seahorse’s version of a Fallopian tube) just before the urogential pore (Vincent, 1990). Oocytes spiral out from the center of each ovary, creating a coiled sheet of developing eggs at differing stages of growth (Vincent, 1990). The earliest or primordial eggs arise from the germinal ridge that runs the entire length of the ovary, and lie at the center of the coil from which they spiral out as they develop so that the fully mature eggs are the furthest from the center of rotation (Vincent, 1990). Roughly 20% to 25% of the outermost eggs in this ovarian assembly line are mature, ready to be discharged during ovulation and deposited with the male (Vincent, 1990). Thus, fully 70-75% of the female’s developing eggs are retained in the ovaries after mating, so a new clutch of eggs will mature relatively quickly and lie in readiness for the next mating cycle.

Seahorse ovaries are thus always active, busy creating and developing new eggs (oogenesis), forming the yolk (vitellogenesis), and resorbing any mature ova (atresia) leftover after mating or at the end of the breeding season (Vincent, 1990). Eggs in all 4 stages of development can be found in the ovaries throughout the year.

Mature eggs are normally only hydrated (i.e., water is added) at the last minute, in the final few hours before mating occurs. This is done to assure that a receptive male is waiting to receive the clutch once the eggs have been hydrated. All of the hydrated eggs are transferred to the male during the copulatory rise. Unhydrated eggs are retained and continue to mature and move along the ovarian assembly line until they are needed for the next mating. The hydration is quite evident to the observer because the hydrating eggs increase in size greatly as they take on water, and the resulting swelling of the ovaries is quite visible. Once swollen with ripe eggs, a breeding female’s trunk becomes quite plump and rounded, especially in the region near the vent.

Most of this time this does not present a problem at all, since the female will deposit the eggs with her mate, or if that’s not possible for some reason, simply release her ripe eggs and spill them on the bottom. It will be quite obvious if your female drops her clutch of eggs, since she will lose up to 30% of her body weight after releasing them (Vincent, 1990). Unless you’re cleanup crew makes short work of them, the eggs she spills will be equally evident. Unlike most fish eggs, which are round or nearly so, seahorse eggs are pear-shaped. They are full of oil droplets and rich in carotenoids (yellow to red pigments), which help to provide an intracellular source of oxygen for the fetal fry (Vincent, 1990). The presence of these pigments gives the eggs their characteristic bright orange coloration. The eggs sink, so if she releases her clutch, they dropped eggs will appear as a mass of tiny (1.2 mm) bright yellow-two-orange ovoids that are very sticky to the touch. You can’t miss them.

In short, Tammy, it’s possible at your female is carrying a large clutch of mature eggs. If so, that should not present a problem in your case because she has a persistent suitor who is trying very hard to get pregnant with which to deposit the eggs. And even if she decides to resist his advances at the last minute, she will most likely either dump them on the bottom or gradually resorb them (atresia), and all will be well.

Here is an excerpt from my new book (Complete Guide to the Greater Seahorses in the Aquarium, unpublished) that discusses egg binding in more detail and explains the circumstances under which it is most likely to occur:

Egg Binding: a Health Risk for Breeding Females.

<quote> Egg binding occurs when a female has ripened (hydrated) a clutch of eggs and is unable to deposit them with a mate or release them for some reason. As more eggs develop, the egg bound female becomes increasing bloated and great pressure begins to build up internally. The abdomen will be very swollen, especially around the vent, and often prolapsed tissue or other material will begin to protrude from the vent as the pressure builds. The affected female will show rapid respiration and may go off her feed. If the pressure cannot be relieved, death results.

Tracy Warland describes a typical case in a female Potbelly (Hippocampus abdominalis) as follows: "Went into the shed one morning to find an adult mare, probably fully mature, in distress. She had been living quite happily in the main tank with about 10 males to meet any desire she might have. Anyway she was lying on the bottom of the tank, panting. I removed her immediately and placed her in sick tank, thought it could be parasites so gave her several 5-minute freshwater baths, but these did not seem to help. I had checked all parameters of large tank the day before so I knew the water was pristine, no other horse was stressed.

When I was putting her back after a freshwater bath, I was supporting her upright for a few minutes to see if she could hitch somewhere. I applied very slight pressure to her belly, and out shot masses of orange stuff. I collected some and checked under the microscope and it looked very much like roe, but the yolk was almost smashed, with globules of a fat-like substance within the centre. We’ve had roe before, due to unsuccessful egg transfer, so we picked up some of bottom of tank and checked it out! I put it down to women’s problems, egg bound, could not discharge unfertilized eggs, these became rotten within her and therefore caused perhaps fever like symptoms."

Egg binding is uncommon in seahorses. Most females have no problem simply dumping their eggs and spilling them on the bottom when a receptive male is unavailable. But there are two circumstances that sometimes promote egg binding. One of them is when breeding seahorses are kept in a tank that’s too shallow. Courtship will proceed normally and the female will hydrate her clutch of eggs in due course, but the pair will then be unable to complete the copulatory rise due to the lack of depth. In such a situation, the female is very reluctant too dump her eggs while a receptive male is standing by, eager to receive them. If she retains the ripened eggs too long in hope that they will be able to complete the egg transfer despite the inadequate vertical swimming space, she may become egg bound.

The other situation that may predispose females to egg binding is when the sexes are segregated. For example, Heather Hall reports that the London Zoo was so successful in breeding and raising the prolific Cape Seahorse (Hippocampus capensis) that, at one point, they were forced to separate the males and females in order to bring a halt to the population explosion that resulted (Bull and Mitchell, 2002, p 30). However, they were soon forced to abandon their experiment in enforced abstinence because it proved stressful to the seahorses and the isolated females began developing swollen abdomens and experiencing difficulty with egg binding when deprived of the opportunity to breed (Bull and Mitchell, 2002, p 30).

There is no ready cure for egg binding and attempts to manually massage the eggs from the body usually only result in internal injuries. However, there is a folk remedy that’s commonly used to treat egg binding in freshwater fish. This treatment consists of placing the affected fish in a bath of Epsom salts (magnesium sulfate) for 10-15 minutes at a dosage of one tablespoon of Epsom salt for every one-gallon of water (Duedall, 2004). The Epsom baths are repeated once a day until the patient recovers (Duedall, 2004).

I have no idea if this remedy would have any affect on a marine fish, but many freshwater hobbyists swear by it, and egg binding is fatal if unresolved so you really have nothing to lose by trying it. Epsom salts are certainly inexpensive and readily available. If you want to give it a go, I suggest administering a 10-15 minute freshwater bath with one tablespoon of magnesium sulfate per gallon added to the bath water. Mix in the magnesium salts thoroughly, aerate the container, and observe the usual precautions for any freshwater dip. Repeat once daily as needed.

As always, prevention is the best cure. If you provide your seahorses with a reasonably tall aquarium and avoid separating the males from the females, there is a very good chance you will never see a case of egg binding. <end quote>

So that’s the lowdown on the female seahorses in breeding condition that are carrying a clutch of ripe eggs, Tammy. Chances are you’re plump female is simply very well-fed, but it’s conceivable that she could have been stimulated to ripen her clutch of eggs, in response to the persistent courtship attempts from her persistent pursuer. If so, perhaps she is ready to give in and mate with a stubborn stallion. And even if she has ripened eggs but besides not to mate with the male after all, it’s very likely she will simply expel the eggs when the time comes, or gradually resorb them before that point, and be none the worse for wear. But you’ll want to keep a close eye on her for awhile to rule out even the slightest possibility that she could become egg bound.

Best of luck with your seahorses, Tammy! Here’s hoping that your male’s persistence is finally rewarded and that your pair produces a healthy brood of babies very soon now.

Happy Trails!
Pete Giwojna

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