Reply To: Male Pouch Expanded

Okay, please do keep me informed.

If your male’s brood pouch is significantly enlarged and he is not having any buoyancy problems, and is in good appetite and behaving normally otherwise, then in all likelihood he is either pregnant and carrying developing young or he is performing pouch displays to impress the female and trying hard to get himself pregnant. If the pouch remains enlarged for more than three or four days with no sign of buoyancy problems or a tendency to float, then it’s usually safe to assume that the male is pregnant.

There are a couple of obvious tip offs that indicate mating has occurred you should keep in mind.

First of all, when a female ripens a clutch of eggs in preparation for mating, her lower abdomen becomes noticeably swollen, particularly around the area of the vent. When she subsequently mates and passes her eggs along to the male, she may then lose up to 30% of her body weight as a result. So if you notice that one of your females has slimmed down dramatically at the same time one of the male’s pouches has become enlarged, that could be an indication of a successful egg transfer.

As I mentioned briefly, the other rule of thumb to keep in mind is that if a stallion’s pouch remains enlarged for more than three or four days in a row, there is a good chance that an egg transfer may have taken place rather than that the male is simply showing off for the females by pumping up his brood pouch.

In addition to these obvious signs, there are also some more subtle behavioral changes that can alert and attentive aquarist to the fact that his male seahorse may be pregnant. Gravid males often behave somewhat differently; as their pregnancy progresses, they are less mobile and become real home bodies, since they cannot expose their developing brood to any unnecessary risks. They often tend to hole up and may even go into hiding; in the later stages of their pregnancy, they may go off their feed and may even miss a meal or two or fail to show up at the feeding station now and then.

Here are some other indications to look for which 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.

Respectfully,
Pete Giwojna, Ocean Rider Tech Support