Seahorse Miscarriage

Dear Nigel:

Rats! I’m sorry to hear that your seahorse continues to have a problem carrying his pregnancy full term. I know how much you are looking forward to rearing the brood of young and these prematurely aborted pregnancies must be terribly frustrating for you, sir.

This is an unusual occurrence and I don’t think that the fertility of your brood stock is an issue; at least, that’s not a problem that I have ever encountered in all my years. Rather, I suspect that something is disrupting the normal course of the pregnancy and preventing your male from completing gestation. It appears that something is interrupting the normal gestation process and causing your male to abort. When that happens, hobbyists often describe the phenomenon as a phantom pregnancy or a false pregnancy or a miscarriage.

As we have discussed previously, several things can interrupt a pregnancy and cause a gravid male to lose the embryonic young or fetal fry he is carrying. For example, in seahorses, a hormone known as fish isotocin, which is the equivalent of oxytocin in mammals, triggers parturition or giving birth (Vincent, 1990). Thus anything that stimulates excess secretion of isotocin can result in premature births, whereas anything which decreases or delays the secretion of isotocin can postpone delivery and prolong a pregnancy abnormally. In a similar manner, disruption of other hormones can cause a male to spontaneously abort a pregnancy or to actually resorb the eggs. The placenta-like changes that take place in brood pouch, the development of the young, and the pregnancy itself are all controlled by various hormones — testosterone, adrenal corticoids, prolactin, and isotocin (Vincent, 1990) — so basically anything that influences the secretion of those key hormones can have a profound effect on the pregnancy.

Some of the factors that influence these hormonal responses are the presence of the female, low oxygen levels, diet and, of course, stress. The presence of the female most definitely influences the gestation and brood success of her mate. Numerous studies indicate that the presence of female fishes visually or hormonally stimulates male sexual activity such as courtship, nest building, and the development of androgen-dependent sexual characteristics (Vincent, 1990). Research has also shown conclusively that male seahorses which have been with the same female for more than one mating cycle are markedly more successful in brooding young (Vincent, 1990). It is believed that one of the reasons for this is that the presence of their mate stimulates the secretion of the corticoids (steroid hormones produced by the adrenal cortex) and prolactin that control the pouch environment and maintain the incubation (Vincent, 1990). The male is thought to further expand his pouch and develop the placenta-like internal structures to a greater degree as a result (Giwojna, Feb. 2002). More of the eggs can then be successfully implanted and carried to full term (Giwojna, Feb. 2002). Separating a gravid male from his mate can therefore have a negative impact on his pregnancy and should be strictly avoided.

Low oxygen levels during pregnancy can likewise be disastrous. They result in respiratory distress for the gravid male, putting the embryonic young at risk, as well as directly altering the hormones we have been discussing, which can further disrupt the pregnancy. (So check your dissolved oxygen levels, Nigel!)

Poor water quality — especially ammonia and/or nitrite spikes — are one of the most common aquarium stressors that can disrupt hormones and interrupt a pregnancy. Stress hormones such as cortisol will be released in response to such stressors, at the expense of other adrenal hormones, which can have a negative impact on the pregnancy and the developing fry.

Heat stress is doubly bad news for gravid males. Not only can abnormally warm temperatures disrupt the secretion of these key hormones and shut down breeding, they can also directly denature long chain polymers and macromolecules (e.g., proteins, enzymes and hormones) by altering certain bonds and changing the three-dimensional shape of the molecule on the atomic level. And, of course, water temperature also directly affect the metabolism of the seahorse and therefore its gestation period. Up to a certain point, increasing water temperatures will shorten the normal gestation period, just as decreasing water temperature will prolong or extend gestation.

Past a certain point, however, when the increasing temperatures exceed the comfort range for the seahorses, elevated temperatures will bring reproduction to an abrupt halt. For example, the Mexican population of H. ingens begins breeding in late September when the water temperatures decreases below 81°F (27°C), and keep breeding until late May when the water temperatures increase above 80°F again (Eliezer Zúñiga, pers. comm.).

An inadequate diet can also be detrimental to a gravid male for obvious reasons. Maintaining a large brood of developing young can be a big drain on the male’s bodily resources, and a nutritious diet rich in HUFA and essential fatty acids is necessary at this time to help the male keep up his strength. That is why male seahorses have an intestinal tract that’s 50% longer than that of females (Tamaru, Aug. 2001). They need the extra food absorption ability and digestion a longer intestine provides in order to sustain the metabolic demands of up to 1600 rapidly growing fry.

When factors such as these disrupt the pregnancy, it’s not so much a case of "false pregnancy" as a failed pregnancy — a gravid male that was not able to carry his brood of embryonic young and fetal fry to full term due to the sorts of developments we have been discussing. This is how Carol Cozzi-Schmarr describes the situation: "If… conditions are not optimum and the general stress level of the male is too high, the male will simply re-absorb the eggs or abort them. You will sadly think that he was never really pregnant."

So the actions of the aquarist and the aquarium conditions can have a big effect on how well a pregnancy progresses, and whether or not the fetal fry develop normally and are brought to full term, or are aborted, delivered prematurely, or resorbed as embryos. In short, it’s important to handle gravid males with care and to provide them with a nutritious diet, optimal water quality, and a stress-free environment at all times. Those are the most important things you can do to prevent the recurrence of this problem in the future, Nigel.

Although I don’t believe the fertility of your male and his mate is a concern, you should be aware that environmental pollutants and contaminants, particularly heavy metals, can affect sperm and interfere with the fertilization process. A recent study on reproduction in seahorses conducted by Katrien van Look and colleagues at the Institute of Zoology in London found that the sperm released by a male seahorse during copulation comes in direct contact with seawater before fertilization occurs, and therefore any contaminants in the water that inhibit the motility of the spermatozoa can have an adverse impact on the fertilization of the eggs (http://news.independent.co.uk/world/science_technology/article2165477.ece):

"We found that the sperm duct is actually external which means that the sperm has to go outside into seawater before it can enter the pouch," Dr Van Look said.

"This means that seawater is in direct contact with the sperm, as well as with the inside of the pouch when it is opened to let the sperm in. This means that any environmental pollution in the seawater will also be in direct contact with the sperm and eggs."

So if there are any pollutants or contaminants in the water in your seahorse tank, that could have prevented the eggs from being fertilized normally and disrupted the pregnancy accordingly, Nigel. With that in mind, let’s review some of the common environmental factors that can be harmful to seahorses, as explained in the following excerpt from my new book (Complete Guide to the Greater Seahorses in the Aquarium, TFH Publications, unpublished):

<open quote>
Environmental Diseases Associated with Water Quality

Ammonia poisoning and nitrite toxicity are the most common of these problems (Indiviglio, 2002). Ammonia is highly toxic to fish and invertebrates in even small amounts (> 0.01 mg/L or ppm). Nitrite is slightly less poisonous to fishes, but deadly to some invertebrates at very small concentrations (0.01 mg/L or ppm). To be safe, ammonia and nitrite levels must be kept at zero at all times.

Dangerous levels of ammonia and nitrite can build up in the aquarium for many reasons. Failure to cycle the tank properly and establish the biofilter is a common beginner’s mistake, as is adding too many specimens too soon before the biofilter can adjust to the heavier bioload (i.e., new tank syndrome). Impairment of the biofiltration can also cause ammonia and nitrites to reach dangerous levels. This can result from medicating the main tank, a lack of oxygen for the beneficial aerobic bacteria due to a pump failure or power outage, disrupting the live sand bed too deeply when cleaning the substrate, and so on. The undetected death of tankmate such as a starfish or large snail can lead to harmful ammonia and/or nitrite spikes after it begins to decompose, as can overcrowding and overfeeding. Ammonia spikes are a common problem following a heavy feeding.

Seahorses suffering from ammonia and/or nitrite poisoning will struggle to breathe. The symptoms to look are a loss of equilibrium, hyperexcitability, increased respiration and oxygen uptake, and increased heart rate. At extreme ammonia or nitrite levels, fish may experience convulsions, coma, and death. Seahorses exposed to less extreme ammonia levels will struggle to breathe. They will be lethargic and exhibit rapid respiration. They may appear disoriented, periodically detaching from their hitching posts only to sink to the bottom. They will be lethargic and exhibit rapid respiration. Test kits can often confirm your diagnosis by revealing unacceptable levels of ammonia and/or nitrite in the water, but transitory ammonia splikes (following a heavy feeding, for example) may not be detected by testing the water after the fact.

The appropriate treatment is to immediately transfer the seahorses to clean saltwater in a hospital tank and add methylene blue, which aids oxygen transport in the blood. Methylene blue will help seahorses with ammonia poisoning to breathe, and can actually reverse the effects of nitrite toxicity. While the seahorses are undergoing treatment, partial water changes will reduce the levels of ammonia/nitrite in the main tank. The cause of the problem must then be determined or corrected. This can be as quick and easy as finding and removing a dead specimen or as difficult and time consuming as recycling the entire tank.

Heavy metal poisoning is another environmental disease hobbyists must sometimes contend with. Even tiny concentrations of heavy metals are deadly to marine fish and invertebrates. This used to be a common cause for concern among marine aquarists when steel-framed aquariums were commonplace, but the advent of all-glass tanks and acrylic aquaria have greatly reduced such problems.

The chief offender nowadays is copper, which usually becomes a problem when the hobbyist overdoses the tank with a copper-based medication (Indiviglio, 2002). Other times copper enters the aquarium in tap water used for water changes or topping off the tank. The copper is leached into the tap water from copper pipes and plumbing (Indiviglio, 2002).

Other heavy metals (iron, lead, and aluminum) sometimes also present a problem when they are accidentally introduced to the aquarium in rocks, gravel, ornaments or decorations. Some of rocks and gravel sold (e.g., red flint) for freshwater use are unsafe in marine tanks because of a high metal content. The same is true for many aquarium ornaments and decorations (Giwojna, 1990). Be especially wary when purchasing artificial plastic plants for the aquarium. Stick with calcareous rocks and gravel and make certain any ornaments or plastic plants you consider are designed for use in marine aquariums and certified to be safe.

Even the popular sponge or foam filters are often a hazard. Many of them contain metal weights as ballast to hold them on the bottom, which is fine in freshwater but can be deadly in a saltwater setup when the metal slugs corrode and leach heavy metal ions into the water.

Seahorses suffering from heavy metal poisoning will act as if they are falling-down drunk. They will be listless and loggy, and if they attempt to move, they will be disoriented, bump blindly into things, and have great difficulty maintaining their normal equilibrium and balance (Giwojna, 1990). And they will be breathing hard and fast.

Treatment is as for ammonia/nitrite poisoning — get them into clean saltwater ASAP, identify the source of contamination and eliminate it, and change out the water in the main tank. Polyfilter pads pull out copper and many heavy metals and may be especially useful in such a situation.

Contamination of the aquarium water with household chemicals is another common problem for the hobbyist (Indiviglio, 2002). Avoid using anything that gives off strong fumes anywhere near your aquarium! This includes bleach, paint, lacquer, varnish, paint thinner, turpentine, insect sprays, bug bombs, pesticides, hairy spray, cigarette smoke, and household cleaners of all kinds (Giwojna, 1990). Even if the aquarium is tightly covered or sealed with plastic, airborne contaminants from fumes and aerosols will still be pumped into the aquarium from the air pumps (Indiviglio, 2002). To prevent this from happening when you must use such products near an aquarium that cannot be moved, disconnect the air pumps first and work only in well-ventilated area. Use submersible powerheads to maintain circulation in the covered aquarium, work fast, and air out the room thoroughly before you reconnect the air supply.

Medicating the aquarium is the worst possible thing you can do when seahorses are suffering from diseases related to water quality or environmental problems such as the toxic conditions described above (Giwojna, 1990). Afflictions such as these are not caused by parasites or pathogens, so medicating the tank not only fails to address the problem, it actually makes matters worse (Giwojna, 1990). Chemotherapeutic agents can be harsh on the seahorses, especially when they are already weakened due to poor water quality or actual poisoning. Worse yet, they are often hard on the biofilter as well and apt to further degrade water quality by killing off beneficial Nitrobacter and Nitrosomonas bacteria.

Stray voltage is another common cause of chronic stress for seahorses and other aquarium inhabitants, as well as a much more prevalent problem than most hobbyists suspect. Installing a grounding probe in the tank easily prevents it, and every seahorse setup should be equipped with one. A titanium grounding probe is an inexpensive investment that can safeguard the health of your seahorses.

Hypoxia due to low oxygen levels or high carbonic dioxide levels is another environmental condition that has been known to kill seahorses suddenly and without warning. This often tends to happen overnight when CO2 naturally rise as O2 levels are dropping due to the reversal of photosynthesis.

As you know, while they are photosynthesizing during the day, zoanthellae and algae consume CO2 and produce O2, but at night, in the absence of light, this process is reversed and the photosynthetic organisms consume O2 and give off CO2 instead. Seahorse setups in general are susceptible to such problems because hobbyists are so conscious of their seahorses’ limited swimming ability that they tend to leave their aquariums undercirculated. Poor circulation and inadequate surface agitation can lead to inefficient oxygenation and insufficient offgassing of carbon dioxide.

Seahorses are more vulnerable to low O2/high CO2 levels than most fishes because of their primitive gills. Unlike most teleost (bony) fishes, which have their gills arranged in sheaves like the pages of a book, seahorses have rudimentary gill arches with small powder-puff type gill filaments. Seahorses are said to have "tufted" gills because they appear to be hemispherical clumps of tissue on stems. Their unique, lobed gill filaments (lophobranchs) are arranged in grape-like clusters and have fewer lamellae than other teleost fishes. Because of the difference in the structure and efficiency of their gills, seahorse are unsually vulnernable to hypoxia when CO2 levels are high and/or O2 levels are low.

Most deaths due to hypoxia occur when the water pump or filter fails during the night, or there is a power outage overnight when the aquarist is unaware, cutting off the filtration, water circulation, and aeration of the aquarium with devastating results. <End quote>

Okay, that’s the rundown on some of the environmental problems that could possibly be contributing to a failed pregnancy or interfering with the normal fertilization of the eggs, Nigel. Make sure that you’re water quality is not an issue, provide your brood stock with a nutritious diet, and make your seahorse tank as stress-free as possible, and I’m confident that your mated pair will soon get things right and produce a brood of healthy young for you.

Best of luck with your seahorses, sir!

Respectfully,
Pete Giwojna