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There are three possibilities when a male’s pouch is obviously very swollen and enlarged:
1) He is pregnant and carrying a large brood of developing young;
2) He is courting and performing pouch displays known as "Pumping" and "Ballooning;"
3) He is ailing and his pouch is filled with gas or swollen with accumulated fluid.
When the brood pouch is bloated with gas, we would certainly expect the male to be experiencing positive buoyancy and having severe difficulty swimming, if not actually floating and bobbing at the surface like a cork. On the other hand, if his brood pouch was distended with accumulated fluid (ascites), he would be very likely to have difficulty swimming due to negative buoyancy. When that happens, the seahorse tends to hang downward from his hitching post, rather than assuming the normal upright posture, and he may spend periods of time lying prone on the bottom. Since your male is not having any buoyancy problems or difficulty swimming, Tammy, I think we can probably rule out the third possibility.
Ballooning is a simple display in which courting males inflate their brood pouches with water to the fullest possible extent and parade around in front of the female in all their glory as though trying to impress her with the sheer dimensions of their pouches. The pumped up paramours perform proudly, putting on quite a show for the flirtatious fillies.
Pumping is a similar pouch display that requires a series of coordinated movements and a lot more exertion on the part of the courting stallion. Bending vigorously, the aroused male jackknifes his tail to meet his trunk, thereby compressing his inflated brood pouch in the middle. The male then straightens up again, suddenly snapping back to "attention" so as to relieve the pressure on his severely compressed midsection. This rapid pumping motion has the effect of forcing water in and out of the brood pouch in a manner that is virtually identical to the way the young are expelled at birth (Vincent, 1990).
The strenuous pumping action is the stallion’s way of demonstrating his pouch is empty of eggs and that he is a strong, healthy, vigorous specimen capable of carrying countless eggs (Vincent, 1990). By so doing, he assures the female that he is ready, willing, and able to mate, and that he can successfully carry and deliver her entire brood. The male’s marsupium also becomes grossly distended during displays of Pumping, but in that case, it is obvious the male is courting because it looks like he’s doing abdominal crunches as the vigorously pumps water in and out of his brood pouch. Once a male is pregnant, he seals the aperture of his pouch and no longer performs these this place of pumping, although he will continue to engage in other forms of courtship with his partner during their daily greetings.
During displays of Ballooning and Pumping, the male’s pouch is inflated with seawater, so he maintains neutral buoyancy and can swim normally. So I would say your male is most likely either pregnant or performing his displays of Ballooning. That seems to be the most likely explanation in your case, Tammy, since the male in question has been aggressive with the other stallions and flirting like crazy with all of the available females. The fact that you can’t see through his swollen pouch with a light shining from behind it could also be an indication of pregnancy, since the placenta like changes that take place in the lining of the pouch (increased vascularization and thickening of the pouch walls) make the marsupium less transparent..
In other words, you’re stallion is probably either already pregnant or doing his very best to get himself pregnant, and in either case, he may be presenting you with a brood of young in the not-too-distant future. Close observation of your male over the next few days should make it clear which of these possibilities is correct in your case, Tammy.
Here are some signs to look for that indicate mating has occurred and that the pregnancy is progressing normally:
Indications of Pregnancy.
If you witness the copulatory rise and exchange of eggs there is no doubt that mating has occurred and, knowing the date of conception, you can confidently begin the countdown toward the maternal male’s delivery date. Knowing approximately how long the gestation period will be allows plenty of time to prepare nursery tanks, set up a battery of brine shrimp hatcheries, and culture rotifers and ‘pods for the insatiable fry.
But what if you missed the big moment? How do you proceed if you missed the actual mating and transfer of eggs, and you’re not sure if you will soon be dealing with a gravid male and hordes of hungry newborns?
There are no aquatic obstetricians, underwater ultrasounds, blood tests or over-the-counter pregnancy tests to perform, and I shudder to think how one might go about collecting a urine specimen to dip! No worries. Fortunately, there are subtle signs and suggestions that indicate a pregnancy is underway. There are number of changes in the parents’ appearance and behavior to look for. For instance, the male and female will still continue to flirt, but the nature a their displays will change from full-blown courtship to regular greeting rituals.
After mating, in subsequent days the couple will continue to change colors and brighten up when in close proximity and dance together in an abbreviated version of courtship known as the Morning Greeting or Daily Greeting. The pair exhibits the same basic behaviors and maneuvers as when they were courting with one big difference — the male never "pumps" and the female does not "point."
In addition, as the pregnancy progresses, the male’s pouch darkens due to the proliferation of epithelial and connective tissue and the placenta-like changes taking place in the wall of the marsupium, and the pouch gradually swells and expands according to the number of young developing within. The latter is not always a reliable indicator, however. Inexperienced couples often spill eggs during the exchange and a male’s first few broods are often inordinately small. The brood pouch of a male that is carrying only a few fetal fry is hardly any larger than normal, and hobbyists have often been surprised by unexpected births under such circumstances.
On the other hand, an experienced male carrying a large brood can be easily distinguished by his obviously expanding pouch. These mature breeders may carry broods numbering over 1600 fetal fry, depending of course on the species. A stallion incubating hundreds of fry will have an enormously distended pouch by the time his due date approaches.
Gravid males often become increasingly reclusive and secretive as their pregnancy advances. When the onset of labor and birth is imminent, the male will begin to shows signs of distress and his respiration rate will increase to 70-80 beats per minute. The fully developed young become very active and shake loose into the lumen of the pouch shortly before delivery. In some cases, the writhing of the young can be detected through the stretched membrane of the pouch, which causes the male considerable discomfort. He may become restless and agitated as a result, swimming slowly to and fro and pacing back and forth like, well — an expectant father. The fry are usually born in the early morning hours between midnight and dawn, arriving all at once or in multiple batches 24 hours apart.
So if you happen to miss the exchange of eggs, watch closely for the following indications that mating has occurred:
(1) A change in the physical appearance of the parents. The gravid male’s pouch will change from a light opaque color to a dark brown due to the elaboration of the internal structures and thickening of the walls of the pouch. It will enlarge steadily over the next few weeks as the young grow and develop, and the aperture will change from fully dilated to a tightly closed vertical slit. The female’s trunk will change from rotund, full with ripe eggs, to noticeably shrunken and pinched in immediately after the exchange of eggs.
(2) A change in the seahorses’ courtship displays. The pair will continue to flirt and dance and brighten in coloration as part of their Daily Greetings, but the male will no longer pump (no pouch displays) and neither the female nor the male will point. The pair will make no more copulatory rises.
(3) A change in the behavior of the male. He may become increasingly shy and reclusive. Gravid males may go off their feed as the delivery date approaches, missing meals or even going into hiding. When birth is imminent, he will become agitated and distressed and his respiration will increase markedly.
When you notice these telltale signs of pregnancy, it’s time to kick your brine shrimp hatchery into high gear and start some microalgae and rotifer cultures brewing.
At this point, Tammy, it’s difficult to say whether the swelling you noticed in the brood pouch is an early indication of bigger things to come or if it’s just a sign that your male is maturing or preparing his pouch for courtship displays.
One rule of thumb the pros sometimes rely on in such situations is that if the male’s pouch remains swollen and distended for more than three consecutive days, then he is likely pregnant and not merely performing pouch displays.
It is normal for the abdomen of a seahorse to become more rotund after a heavy meal, but during a pregnancy, it is the male’s marsupium or brood pouch that swells and expands rather than its abdomen.
Good luck with your seahorses, Tammy! Here’s hoping your new Sunbursts male provides you with a brood of healthy babies.