pregnant H.barbori

Dear Bob:

Yeah, that’s a bit unusual for a male to deliver just one or two fry on consecutive days. A gravid males normally gives birth to his entire brood within the space of a few hours or spread out over the course of the day. However, as Leslie pointed out, it’s not uncommon for a stallion to deliver one or two fry ahead of time and then temporarily suspend operations, only to give birth to the remainder of his brood a day or two later as usual.

The fully developed young emerge from their individual compartments and shake loose into the lumen of the pouch immediately prior to birth (Vincent, 1990). They become very active toward the end of the pregnancy and can sometimes be seen wriggling about through the membrane of the swollen brood pouch. This appears to be every bit as uncomfortable as it sounds, since expecting males become agitated and distressed as the big moment approaches. They experience definite labor pains when birth is imminent, evident as a series of powerful contractions, and soon begin pumping in time with these birth spasms in order to forcibly eject the fry from their pouches. Labor usually begins well after dark in the early morning hours (Vincent, 1990). The distraught male may pump and thrust vigorously for hours before finally ejecting the first of the newborns (Vincent, 1990). The fry are expelled singly or in ones and twos at first, but are soon spewing forth in bunches and bursts of a half dozen or more.

Delivering a large brood this way is hard work, and the exhausted male will pause periodically to recover from his exertions, gathering his strength until he is caught in the throes of another round of contractions. In some cases, it takes 2-3 days for the entire brood to be delivered in this manner.

No matter how often I see a male giving birth, it never ceases to amaze me. Watching the fry erupt into existence that way is an incredible sight. They are perfect miniature replicas of their parents, able to fend for themselves from the first. It seems a brutal beginning, a ruthlessly rude awakening, to be violently thrust into the world in such an abrupt fashion, but the newborns hit the water swimming without missing a stroke.

So it’s unusual for just one or two babies to be born each day, and I wonder if the abnormal fry you describe might have been delivered prematurely. Such "preemies" are very pug- nosed, lacking the typical seahorse snout, and are still attached to yolk sacs.

Benthic or demersal fry orient to the substrate and seek out hitching posts right from birth, but it is not normal for them just to lay on the bottom and jerk or twitch about. Benthic babies can swim normally and can use their prehensile tails to hitch onto objects the moment they are delivered. Barb babies will scoot along the bottom as Leslie described, rather than suspending in the water column, but the behavior of the newborns you are describing sounds more like a problem with undeveloped or underinflated swim bladders, which is a complication that sometimes affects the fry under certain circumstances, as described below.

A newborn’s first instinct is to head to the surface to fill its swim bladder. (Physosymotous fishes have a connection between their gas bladder and the gut in the form of an open tube called the pneumatic duct, and are thus able to fill the swim bladder by gulping air at the surface. Like many teleost fishes, seahorses lose this connection very early in life, so that their swim bladders are completed closed as adults.) In many species, gulping air is the way in which gas is first introduced into the larvae’s bladder, and if denied an opportunity to do so, their development is hampered due to uninflated swim bladders (Silveira, 2000).

This is the case with seahorse fry. 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. Often 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.

On rare occasions seahorses are born without a swimbladder, so it’s possible that your bottom-hugging fry could have a similar birth defect. Or if these first few fry are preemies, it’s quite possible that your barb male will give birth to the rest of the brood shortly, and if so, there’s a very good chance these full-term fry will be perfectly normal.

In the meantime, make sure you have enough surface agitation to prevent any kind of film from forming on the surface and that the newborns have an opportunity to fill their swim bladders.

Best of luck with your barb and his offspring, Bob!

Respectfully,
Pete Giwojna