Re:A little help here

#5145
Pete Giwojna
Guest

Dear Caspian:

I’m not Leslie but I’ll do my best answer your questions nevertheless.

In nearly stages of pregnancy, it can be very difficult to tell whether a male is carrying developing eggs in his pouch or not. But one 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, as the pregnancy progresses, the male’s pouch will often darken 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.

In short, if you suspect that your stallion may be pregnant, the first things to look for are changes in his pouch (size and coloration) and changes in his behavior. A stallion may become increasingly shy and reclusive when he is carrying developing young. 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 it comes to their coloration, Caspian, seahorses are not like most other marine fish — rather, they are truly the chameleons of the sea with a propensity for changing color in response to a wide range of environmental factors, hormonal influences, and behavioral interactions.

For instance, they may change coloration for camouflage purposes, in order to better blend into their background, which helps conceal them both from potential predators and their prey. Likewise, the color a seahorse displays at any given moment also reflects its emotional state. As an example, seahorses often brighten in coloration when excited or aroused, whereas they tend to darken in response to fear or stress. And, of course, a whole range of other factors such as the aquarium lighting, water quality, diet, and medicines, to name just a few, can also have a marked influence on the coloration of seahorses.

But I suspect you are primarily interested in the color changes seahorses undergo when they are courting and mating, Caspian. Tropical seahorses will often brighten or lighten up in coloration dramatically when they are courting and mating. In Hippocampus erectus, for example, the normally dark colored seahorses will often adopt shades of white — anywhere from a pearly white to a chalky white or chalk yellow — during courtship and mating. However, regardless of the colors involved, the head, dorsal surface (i.e., back), and ventral line (keel) of the seahorse normally remain quite dark while the rest of the body becomes lighter and dramatically intensifies in color during courtship displays (Vincent, 1990).

For a more complete discussion of how and why seahorses change color, Caspian, see the two-part article on coloration in seahorses that I recently wrote for Conscientious Aquarist online magazine. The first article explains how seahorses use their amazing color changing ability, while the second article explains how they accomplish their color changes and is loaded with tips for keeping colorful seahorses such as Sunbursts looking their best and brightest. You can read the articles at the following URL’s and enjoy Leslie Leddo’s magnificent photographs. Just copy the following URL’s and paste them into your web browser, and it will take you directly to the articles:

part one:
http://www.wetwebmedia.com/ca/volume_4/V4I1/hippocampus_color/Color_In_Hippocampus.htm

part two:
http://www.wetwebmedia.com/ca/volume_4/V4I2/hippocampus_color2/Color_In_Hippocampus2.htm

There is a relatively easy way to tell when the female has transferred all of her eggs to the pouch of the male, Caspian. 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 are lucky enough to watch the egg transfer, you’ll be able to see the female’s body slim down dramatically during the mating attempt, which is a good indication of a successful egg transfer.

As you know, the actual transfer of eggs takes place while the couple is suspended in midwater or slowly descending toward the bottom — a maneuver that is every bit as tricky as it sounds. Coitus is marked by an extremely awkward, fleeting embrace, aptly described as little more than a brief belly-to-belly bumping (Vincent, 1990). (Brief and fleeting as in if one dares to blink, take a bathroom break, or run for your camera you may miss what you have waited all this time to witness!) As you can imagine, many difficult and delicate maneuvers are required to bring the pair into proper position for this most improbable merging. The female will attempt to insert her oviduct into the gaping aperture of the male’s inflated brood pouch. An inexperienced pair will often end up misaligned, perhaps at right angles to one another or with one of the partners too high or too low to join. This is very typical of the many false starts and abortive attempts that are ordinarily involved. The frustrated couple will separate to rest on the bottom prior to successive attempts. They may require many such rises before the proper positioning is achieved and the crucial connection is finally made.

The female will eventually succeed, with the full and active cooperation of her mate. He positions himself slightly below his mate, with the aperture of his pouch fully dilated and gaping open, ready to receive her eggs. The female will hover directly over the aperture until she can actually insert her oviduct into the opening at the top of his brood pouch or drop her eggs into the basket while hovering directly above the pouch. Pairs occasionally entwine tails when joined, but more often than not their tails will be stretched back behind them, out of the way.

If she makes a good connection, she will extrude her eggs in one long, sticky string, and the pair will hang together in midwater while the transfer is completed, drifting slowly downward as the eggs surge downward deep inside the pouch (Vincent, 1990). The entire clutch — up to 1600 eggs — is transferred in one brief embrace lasting a mere 5-10 seconds (Vincent, 1990). Sperm streams from the male’s urogenital pore into the pouch opening as the eggs are deposited (Vincent, 1990). The couple separates as they descend, drifting slowly toward the substrate. Exhausted by their efforts, the pair seek out comfortable hitching posts for a well-deserved rest. One almost expects to see them light up cigarettes at this point.

Young ponies and inexperienced pairs often find coitus awkward and difficult to accomplish successfully, and when they don’t make the crucial connection smoothly, it’s not unusual for some of the eggs to be lost during the transfer. So under certain circumstances, it’s not at all unusual for eggs to be spilled while mating or even for a female to drop her entire clutch of eggs.

Hippocampus erectus ova are bright orange ovoids about 1.5 mm in diameter. Unlike most fish eggs, which are round or nearly so, seahorse eggs are slightly 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. The presence of these pigments gives the eggs their characteristic orange coloration. The eggs are negatively buoyant and sink to the bottom when released. The eggs are also very sticky or adhesive.

Seahorse roe is indeed very nutritious due to the rich yolk supply, and the scavengers in the tank typically make short work of them, scarfing them up like caviar.

Best of luck with your new seahorses, Caspian!

Happy Trails!
Pete Giwojna


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