Pete Giwojna
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Re:Pregnant Seahorse - 2006/02/27 14:12
Dear Bob:
You can expect your Sunburst to give birth approximately 2-4 weeks after mating. The gestation period for Mustangs and Sunbursts varies between 2-4 weeks, dependent largely on water temperature and diet. No, I wouldn't recommend moving a pregnant male into a paternity tank when he's ready to deliver. That's a bad idea for a number of reasons we'll discuss in greater detail at the end of this e-mail.
Here are some other indications 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.
Now that you know what to look for as your male's pregnancy progresses and the birth spasms approach, we can deal with the issue of whether or not it's best to move your male or let him give birth right where he is.
The Paternity Tank: just say, "No!"
To successfully raise sea horses, preparations to feed and house the fry must begin well before the brood is due. Start by setting up two or more nursery tanks, depending on how many babies you expect to be raising and whether or not you will be dealing with benthic or pelagic seahorse fry. Your first decision is which of the different types of nurseries we have discussed is best suited for your needs. One of them should be ideal for your circumstances. Set up your preferred nurseries just as previously described.
Your next decision is whether to allow the pregnant male to give birth in the main tank and then to transfer the fry to the waiting nurseries, or to transfer the expectant father to the nursery tank ahead of time so he can delivery his brood there. There are two schools of thought on this. Some hobbyists feel it's best to use the nursery tank as a paternity ward, since the delicate newborns never need to be handled if the male gives birth directly in the nursery. Other breeders feel it's better to disturb the pregnant male as little as possible and prefer to have him deliver his brood right where he is, in the familiar surroundings in which he's most comfortable.
That's a no-brainer, folks. In my opinion, it's ALWAYS better to assure the well being of the male and safeguard your broodstock. A pair-bonded couple will soon establish a regular breeding cycle in the aquarium, producing a new brood every two, four, or six weeks. (The gestation period varies with the species and is often correlated with the lunar cycle so that the fry are delivered during the highest tides, which helps disperse the young; Vincent, 1990.) A healthy pair-bonded male will deliver a new brood of young every month or so during the breeding season, producing countless offspring over the course of its life. But if you lose a breeding male, you lose all of his future progeny with him, as well as the superior genetic traits he carries. It is folly to jeopardize the health of a pregnant male for the sake of the brood he is carrying at the moment.
Handling a gravid male, especially when the pregnancy is well-advanced, should be avoided at all costs. At best, it will be stressful for the male to be captured, separated from its mate, and transferred to a strange new environment (Giwojna and Cozzi-Schmarr, Feb. 2002). At worst, rough handling and stress can trigger premature delivery or cause the pregnancy to be aborted altogether, adversely affecting the health of the male and his brood (Giwojna and Cozzi-Schmarr, Feb. 2002). Stressing a pregnant seahorse has many detrimental effects, including decreased appetite, adverse hormonal changes, impairing the immune response and lowering disease resistance.
Separating the expectant father from his mate at this crucial time can also prevent him from re-mating with his chosen partner and may even break up a pair-bonded couple (Giwojna and Cozzi-Schmarr, Feb. 2002). Throughout his pregnancy, the male maintains daily greeting rituals with his mate that serve to strengthen and reinforce their pair bonds and keep them physiologically attuned to one another. When the male gives birth, his mate is normally waiting nearby, ready to hydrate her clutch and rise for the exchange of eggs as soon as he has recovered. Many times they will resume their mating dance and re-mate scant hours after the male delivers his latest brood.
Isolating the male from his partner during the pregnancy effectively puts an end to all of that. They are preventing from conducting morning greetings, their carefully orchestrated breeding cycle may be disrupted as their hormonally regulated reproductive synchrony is lost, and the pair bond is weakened accordingly (Giwojna and Cozzi-Schmarr, Feb. 2002). Their bonding may even be broken as a result. That's not what a successful breeder should strive for!
If you are concerned about the filtration in your main tank "eating" the newborns, modifying your filter to prevent this is a much better alternative than transferring the male to a paternity ward (Giwojna, Feb. 2002). Just screen off the intakes or cover them with sponge prefilters. Or you can simply switch off the skimmer and any supplemental filter(s) when his due date arrives and delivery is imminent. (Just don't shut down your primary biofilter!) That way, the male can remain with his partner through the pregnancy and deliver his brood in a stress-free environment.
Generally, the only time a paternity tank is advisable is on those rare occasions when a pregnant male develops a health problem that requires treatment (Giwojna, Feb. 2002). In that case, it's best to make the transfer early in his pregnancy (at least 2 weeks prior to his delivery date). Make sure the hospital tank/paternity ward has been prefilled with water from the main tank to reduce stress and ease the transition. If at all possible, transfer his mate along with him. And situate the paternity tank in a quiet, low traffic area, making certain it includes enough shelter so that the expectant father won't feel vulnerable and exposed.
Best of luck with your pregnant Sunburst, Bob! Here's hoping he provides you with many broods of healthy fry.
Happy Trails!
Pete Giwojna
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