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Horse Forum - February 2002

by Pete Giwojna and Carol Cozzi-Schmarr
from the February 2002 issue of Freshwater and Marine Aquarium magazine (FAMA)

Dear Pete,

If you have a pregnant male should he be removed from a tank with a bio filter and protein skimmer to prevent babies from being sucked up through either? Thanks,

Maureen Riberdy

Dear Maureen:

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. 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.

A better alternative is to modify your filter, screening off the intake or covering it with a sponge prefilter. 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!)

The young can then be carefully transferred to a waiting nursery tank at your leisure. NEVER lift the babies out the water when transferring them. They will swallow air and develop fatal buoyancy problems that leave them bobbing helplessly at the surface, unable to submerge or eat. Exposing the newborns to the air is one of the most common mistakes inexperienced breeders make, and it often results in the loss of the entire brood. The proper way to move the babies is to carefully scoop them up in a small cup or bowl, and gently immerse the cup in the nursery tank to release the fry. Or a common turkey baster works well for gently sucking up one or two of the fry at a time and releasing them into their nursery.

Generally, the only time a paternity tank is advisable is if your main sea horse exhibit houses specimens that would be inclined to regard the newborns as tasty treats. Sea Horses very often give birth in the early morning hours, so any such predatory tankmates would almost discover the newborns and make serious inroads in their numbers before the hobbyist could intervene.

Should it ever become necessary to remove a gravid male for treatment of a health problem or to avoid voracious tankmates that might want a side order of "fries," make the transfer early in his pregnancy and make sure the paternity tank 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.

Dear Carol,

I watched my male give birth the other day and it seemed like it was so much work for him. Does the birthing process stress the male?? Does the male need time to recover from giving birth? Should he be separated from his mate until he has recuperated?? If so, how long should this be for and how does on tell if he is ready to mate again??

Thanks Madeline,

Dear Madeline,

Although it may seem that the male is stressed while giving birth, this is a natural process that he is well designed for. His physiology and genetic make up enables him to handle this seemingly painful process without any ill affects as long as he is feed a proper diet rich in Highly Unsaturated Fats (HUFA's) as well as vitamins and minerals during his pregnancy and that he is always (and she!!) provided with the appropriate environment. This includes optimum water quality, proper tank height and volume, proper habitat and tank mates and freedom from harmful pathogens.

As Pete Mentioned, probably the most stressful thing one could do to a pregnant (gravid) male that is close to giving birth would be to "handle" him by moving the male from his normal environment (home!!) to a new and unfamiliar environment like a different holding tank. (hotel room!!). This unnecessary "transfer" and " handling" will force him to adapt to a strange environment causing a general increase in his stress level causing many possible negative outcomes such as decrease in appetite, lowering of the immune system causing opportunistic pathogens currently present in the aquarium but not at high levels to take a hold on the sea horse causing health problems, and sadly may prevent him from re mating with his mate.

You see, the male will continue his bonding rituals (such as Pete has described) with his mate during the birthing process and immediately after giving birth. The pair will begin the treasured mating dance that will hopefully result in a successful egg transfer from the female to the male often within hours after giving birth!! Remember that with many sea horse types the older the male the larger the size of his pouch and therefore the greater the number of sea horse babies in the pouch!! For example, a 5 year old adult H.reidi male may give birth to as many as 2000 babies with each spawn!!!! A young 6 month old juvenile male may only give birth to 10 or 20 babies!!! It is also more likely that the older male has been mating with the same female all is life!! Imagine the stress of not being with his " beloved" during this time!

This unnecessary "handling" or "transfer" is, of course, extremely hard on wild caught males and may cause his death immediately after giving birth. One should avoid purchasing wild caught pregnant males at all costs. It is easy to feel sorry for him in the pet store, but his purchase only encourages the collectors to take additional pregnant males the next time causing further devastation to the already highly threatened wild sea horse populations.

Certainly this "handling" or "transfer" stress is greatly reduced with the farm raised pregnant males but the general concept still applies. If you purchase a farm raised pregnant male you should not expect a male that is almost ready to give birth but one that is within 2 weeks of giving birth. The normal gestation period averages at 30 days depending mostly on species and environmental parameters such as temperature and diet.

If these 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 pregnant

If , however, you are able to keep these parameters optimum, you will have a much greater chance of being successful with your pregnant male so that you can enjoy this amazing phenomena of the pregnant male sea horse!! With a little more patience you will surely be rewarded with the great performance of the sea horse mating dance followed by the most precious site of all......the fat bellied pregnant male sea horse!!!

Aloha, Carol Cozzi-Schmar

Dear Pete:

I have a few questions that have arisen out of watching my sea horses flirt.

I have three female comes and one male (still waiting for more males to show up in shops near us). I realize that the behavior should stop if I add more males, but for now what happens is that the male starts courting one of the females, they both flirt for a while, and then he gets distracted and moves across the tank to another female and flirts with her. And he travels from one to the other. Sometimes another of the females butts in and that's what breaks up a pair flirting, but most of the time it seems like he has attention deficit. I wonder if he's just hoping he gets lucky with someone, anyone of the three. I have seen one female whom he was flirting with acting huffed when he switched attention to another female, she started butting in on them. However it is mainly the male that is aggressive flirter.

So here are the questions.

Does the male always initiate the courting? My male approaches the female from the left side and slightly lower than her and herds her in clockwise circles. In other captive environments, do people's male sea horses seem to just hope to hit it off with any female in the tank and court all of them at once?

Are any hormones or such released into the water, because I sometimes see horses across the other side of the tank from the flirting pair starting to flirt when the others flirt? It seems like a chain reaction. (This is not restricted to just the comes as the reidi start following too).

Sarah.

Dear Sarah:sea horses try to give their eggs away. In the kinky world of sea horse sex, the boys still chase the girls, even though it's the boys who get pregnant as a result! Many sea horse species are essentially monomorphic, but when there are significant differences between the sexes, it's the males who are larger and more colorful, as seen with Hippocampus abdominalis.

I have already discussed the issue of pheromones or chemical triggers that may stimulate courtship and breeding in a previous question, Sarah, and the evidence does suggest that Pumping males may release such a substance during their pouch displays. (The hormone prolactin is the prime suspect.) Whether it's the visual stimulation provided by nearby courting couples, or some equine "aphrodisiac" at work in the water, I can confirm your observation that courtship often seems to be contagious in captivity. Your description of a "chain reaction" of sexual activity under certain conditions is especially apt for Dwarf Sea Horses (Hippocampus zosterae), which often breed best in groups, as discussed in the following question.

Dear Pete,

Funny you should ask for questions on this topic. Early last May I received 5 dwarfs from FL. Two males and three females. One male had a buoyancy problem and was near death when he arrived. He did eventually start eating, but he never did recover, and he died after about 5-6 weeks. The other male was pregnant and gave birth within the first week. I noticed him courting one of the females several times over June and July, but to no avail. I usually saw this in the mornings, and since I'm back to teaching as of August

I really don't know if he has given up or not. The lower part of his pouch appears darker now. I know dwarfs often don't breed well when there are less than six of them in the tank, so why was he trying then? I was just wondering if you could shed some light on the matter. I'm contemplating ordering some more to add to the tank.

Thanks, Kelli

Dear Kelli:

Well, dwarf sea horses do indeed breed better when kept as a group, but it's not an absolute prerequisite for successful mating. Anytime you have a male and female together, mating is possible, and the stallion is apt to try his luck with any available mare, but the chances he will find a compatible partner increase along with the number of prospective mates he has access to. In the wild, dwarf sea horse populations have been found to be heavily biased in favor of females (Strawn ), with females outnumbering males by as much as to 10:1 in certain areas (Joanne Heuter, personal communication). These is extremely unusual for sea horses-in most species, males predominate-and this unbalanced sex ratio may have something to do with the highly promiscuous nature of H. zosterae and the fact that it breeds best when kept in groups in which the males have a choice of partners. In general, the "more the merrier" is the rule when breeding Hippocampus zosterae, and the odds of reproductive success increase markedly when they are kept in mixed groups of ten or more.

In fact, this is how I described them in last month's column: "Dwarf sea horses are as prolific as they are promiscuous in captivity. Far from inhibiting courtship, crowding seems to stimulate breeding in zosterae, almost as if they reach "critical mass" at a certain population density, triggering a chain reaction of mating attempts."

As an extreme example of this, I know of one case where over 300 H. zosterae were kept in a 10-gallon tank due to a lack of space (Robert Straughan, Keeping Sea Horses, 1961). Despite these crowded conditions, over 100 of them managed to pair up and mate repeatedly in this cramped setup. Straughan reported that at any given moment, dozens of dwarves were actively engaged in courtship, so it was a common sight to witness several couples rising simultaneously to exchange eggs, and that one or more of the gravid males would be delivering young virtually around the clock.

A so-called "orgy theory" has even been advanced to explain this behavior in the dwarf sea horse. In a nutshell, it maintains that the sight/scent or nearby courting couples has a snowball effect in zosterae herds, stimulating other dwarves to initiate courtship and mating, which in turn triggers tankmates in their proximity to join in the fun, eventually spreading throughout the colony in this manner. Whether the driving stimulus is visual (the sight of many couples actively courting close by) or hormonal (the concentration of excitatory chemicals produced by several males Pumping simultaneously in a limited volume of water), no one can say for sure, but it's a legitimate phenomena among captive zosterae.

Happy Trails!

Pete Giwojna

Dear Pete:

How much is know about what a sea horse is looking for in a potential mate? I know they are evaluating each other in some way, or certain horses would not be left out. One such example is a tank with a male and female H. comes, male and female H. erectus, and a male and female H. reidi. The female reidi is the pick of ALL 3 of the males in the tank to the exclusion of the other females. I have not heard of this happening often and would

appreciate help on how to advise this person to straighten out their sea horses! Another tank is not available to this person at this time, but they really want their pairs of horses to breed to their own kind, and they can't figure out why only this one filly is sought after when there are other females present.

Carol Keen

Dear Carol:

Sea Horses do indeed appear to choose their partners selectively, and it is usually the female that has the last word on a prospective pairing.

Thus far, laboratory studies of competition for mates have clearly identified only one factor that is positively correlated with success: size-both male and female sea horses prefer large, robust mates. Researchers say there is a "fecundity advantage" to large size in sea horses. Clutch size and egg size are both correlated with female size, so it's no mystery why stallions prefer big females. Large males are apparently in demand because they can successfully incubate a larger proportion of the female's clutch, and survive better in the wild (the welfare of the young he is carrying is obviously dependent on the male's ability to survive long enough to deliver his brood).

This preference extends across species lines. One of my all-time favorite sea horse photos shows a tiny Hippocampus breviceps male, his pouch inflated to the bursting point like a balloon, in hot pursuit of a much larger H. abdominalis female, that clearly finds the miniscule male far beneath her notice. Apparently, the little H. breviceps found the sight of a female of such absolutely unprecedented proportions to be utterly irresistible!

I'm willing to wager the H. reidi female is the biggest of the three fillies by a considerable margin. If she monopolizes the attention of all the males, she is also probably the only female in the tank to ripen eggs, and that is one other thing all male sea horses are drawn too-an egg-laden female. Male sea horses can tell when a female has ripened her clutch, and in non monogamous species, it is a common sight to see all the males in the tank totally ignoring the other readily available females in order to compete over the one female swollen with eggs. Wherever she goes, an entourage of over-aroused males will accompany her, all with fully inflated brood pouches, looking like a flotilla of hot air balloons.

As long as the reidi is the largest female in the tank, and the only one regularly carrying a clutch of ripe eggs, she is bound to remain the most popular gal in town. The obvious solution is to provide the Brazilians with a tank of their own, but if that's out of the question, your friend might consider partitioning her sea horse tank and confining the reidi behind an opaque barrier at one end of the aquarium. Give the H. reidi roughly 1/3 of the tank to themselves, and the H. comes and H. erectus females may suddenly start to look a lot better to their respective males.

Hi Pete!!

I was wondering about pheromones and do we know anything about pheromones being released during the actual mating "dance"? I've observed my reidi pair, and wonder if the constant pouch flushing that the male does during his display could possibly be releasing a chemical signal to ripen the eggs in his mate?

Jennifer Myerscough

Dear Jennifer:

Good question! The pouch displays you refer to are known as "Pumping," and are a vital part of the courtship ritual in all sea horse species that have been studied to date. When Pumping, a male sea horse inflates his pouch and mimics the motions of giving birth by repeatedly flexing his tail forward from its base, and then straightening up again to thrust his belly outward. This has the effect of alternately compressing the inflated brood pouch in the middle, and then expanding it to its fullest, thereby pumping water in and out of the pouch. The male performs this exercise with great energy, and an aroused male looks remarkably as if he were doing ''abdominal crunches'' in gym class.

As summarized below, many theories have been advanced to explain the purpose of Pumping displays, including the possibility of sending chemical signals:

(1) Pumping indicates to the female that the pouch is empty of eggs, unmistakable advertising that "I am an eligible male."

(2) Pumping signals that the male is ready, willing, and able to mate.

(3) Pumping flushes and cleanses the pouch-preliminary preparations for receiving a new clutch of eggs.

(4) Pumping allows the female to judge pouch volume in a prospective mate, demonstrating that the male has the capacity to carry a large brood.

(5) Pumping is very energetically demanding, thus providing a measure of male vigor and stamina.

(6) Pumping is very like the parturition process and so may indicate the male's effectiveness at ejecting his young.

(7) And, of course, Pumping may stimulate a female by chemical means.

The latter theory was first proposed by Weber in 1924 during his research with Hippocampus brevirostris, and has much circumstantial evidence to support it. In male sea horses, the elaboration of pouch structures necessary to support the developing embryos is under testicular control via testosterone, but corticoids and the hormone prolactin maintain the actual incubation. The role prolactin plays in stimulating parental care in other fishes is well-established: for instance, prolactin is known to stimulate egg fanning in sticklebacks and wrasse, and it increases mucus production in discus via its effects on epithelial tissue, allowing newborn discus to feed on mucus from the flanks of their parents. It is also well known that females are sensitive to prolactin and that it likewise plays a role in female reproductive processes. (For example, it stimulates milk production in human females beginning during late pregnancy.)

Garrick-Maidment sums up the situation as follows: "The pouch is an amazing organ. It is controlled by hormones, one of which is lactin...The male starts to rise in the water, enticing the female to rise with him by doing contractions very similar to the ones he uses when giving birth. As he contracts, he sends a hormonal signal out into the water. His pouch is also flushed out during these contractions, making sure it is clean and ready to receive eggs..." (pp 18-19).

Here's what is known for certain. A courting male directs his pouch displays towards the female he is romancing, while facing her. The heavily vascularized brood pouch is under hormonal control. Any traces of these hormones that remain within the pouch would be wafted over the nearby female during displays of Pumping. Female sea horses have receptors for certain of these hormones, which fit them like a key fits a lock. And it is an indisputable fact that female sea horses only hydrate their eggs on the final day of courtship, in response to persistent displays of Pumping by an ardent stallion. (Once she has ripened her eggs in this manner, the female must deposit them with a receptive male within the next 24 hours or drop her eggs and lose her entire clutch.) So while I am aware of no research that conclusively proves that prolactin, or any other substance released by an aroused male, triggers a sexual response in the female he is courting, it seems likely that chemical cues are involved.

Hi Pete!!

I'd also like to know if the female being gravid could prompt the male to deliver, even prematurely? My male reidi seems to deliver early (in as few as 11 days). I do also believe this is temperature-related (tank was running about 82 degrees during the Summer months), but I wondered if the female sends chemical signals to the male to indicate that she is ready to mate again.

Jennifer Myerscough

Dear Jennifer:

This is an interesting question. Females sea horse are fractional spawners, meaning they maintain an assembly-line of maturing oocytes at all times, only a portion of which are deposited in any single clutch, so they always have an abundance of mature eggs at their disposal. All that is necessary to ripen these eggs for ovulation is to hydrate them, a process which takes only a few hours. Female sea horses therefore theoretically have the ability to mate every few hours. In actuality, they will only ripen their eggs in the presence of a receptive male that is actively Pumping, and only mate once per breeding cycle.

In pair-bonded sea horses such as Hippocampus reidi, the couple performs a daily ritual known as the "morning greeting" that repeats the initial stages of courtship. The partners approach one another at first light, brighten, and dance for an average of 5-10 minutes. In full courtship regalia, they will alternate between displays of synchronized side-by-side swimming, termed the "Parallel Promenade," and the circling "Maypole display" or "Carousel Dance," often with their tails entwined, but always stopping short of Pumping and Pointing respectively. The daily greetings serve to strengthen and reinforce the pair bond, but more importantly, they keep the couple acutely attuned to one another's physiological condition, enabling them to keep their biological clocks synchronized. When the male delivers his latest brood, the female will be waiting nearby, ready to hydrate her next clutch, and they will typically remate within the next 24 hours. It is thus the gravid male who determines when the female ripens her next clutch of eggs, not vice versa.

Having said that, however, the presence of the female most definitely influences the gestation period 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 androgen-dependent sexual characteristics. Research has also shown conclusively that male sea horses which have been with the same female for more than one mating cycle are markedly more successful in brooding young. It is believed that one of the reasons for this is that the presence of their mate stimulates the secretion of the corticoids and prolactin that control the pouch environment. The male is thought to further expand his pouch and develop the placenta-like internal structures to a greater degree as a result. More of the eggs can then be successfully implanted and carried to full term.

These same hormones also help control the development of the embryos, so female sea horses may indirectly influence the gestation of their mates by stimulating the secretion of these all-important substances. As an example of how this can come about, organic ions that have diffused into the marsupial fluid are transformed into amino acids by a protease secreted by the pouch epithelium under the influence of the male hypophysary prolactin. Since amino acids are the building blocks of protein, the development of any structures that incorporate protein will be affected if the production of prolactin is impaired, and growth and development of the fetal fry will be hindered accordingly.

I know of one case where a male sea horse that was nearing the end of his gestation was removed from his mate, only to have its gestation abnormally prolonged. He was due to deliver within a day or two, yet several days later, no young were forthcoming. The days became weeks and still nothing happened. The male remained obviously pregnant throughout, seemingly ready to pop, and behaved normally and ate well all the while, but there was no sign of any offspring. Finally, after more than two breeding cycles had passed uneventfully, the long overdue male was reunited with his mate. Sure enough, shortly thereafter, he delivered a normal brood. It was as if gestation had simply been suspended, the young merely maintained in the brood pouch, arrested without further growth and development, all the while he was separated from his mate. Draw your own conclusions.

However, it is very unlikely that the presence of the female could stimulate the male to deliver prematurely. Quite the contrary, the evidence clearly shows that pair-bonded males successfully carry a greater portion of each clutch full term the longer they remain with their mates. That pattern will likely be repeated with your pair over time.

In your case, the elevated temperatures are the probable cause for your male's abbreviated gestation, just as you suspected. The gestation period of H. reidi is about 14 days at 75-degrees F/24-degrees C, and a rise to 82-degrees F could easily shave a day or two from that figure. In addition, heat stress is one of the factors that can trigger premature births. Bear in mind that gestation can vary considerably from individual to individual within the same species.

Dear Carol,

I watched my male give birth the other day and it seemed like it was so much work for him. Does the birthing process stress the male?? Does the male need time to recover from giving birth? Should he be separated from his mate until he has recuperated?? If so, how long should this be for and how does on tell if he is ready to mate again??

Thanks Madeline,

Dear Madeline,

Although it may seem that the male is stressed while giving birth, this is a natural process that he is well designed for. His physiology and genetic make up enables him to handle this seemingly painful process without any ill affects as long as he is feed a proper diet rich in Highly Unsaturated Fats (HUFA's) as well as vitamins and minerals during his pregnancy and that he is always (and she!!) provided with the appropriate environment. This includes optimum water quality, proper tank height and volume, proper habitat and tank mates and freedom from harmful pathogens.

As Pete Mentioned, probably the most stressful thing one could do to a pregnant (gravid) male that is close to giving birth would be to "handle" him by moving the male from his normal environment (home!!) to a new and unfamiliar environment like a different holding tank. (hotel room!!). This unnecessary "transfer" and " handling" will force him to adapt to a strange environment causing a general increase in his stress level causing many possible negative outcomes such as decrease in appetite, lowering of the immune system causing opportunistic pathogens currently present in the aquarium but not at high levels to take a hold on the sea horse causing health problems, and sadly may prevent him from re mating with his mate.

You see, the male will continue his bonding rituals (such as Pete has described) with his mate during the birthing process and immediately after giving birth. The pair will begin the treasured mating dance that will hopefully result in a successful egg transfer from the female to the male often within hours after giving birth!! Remember that with many sea horse types the older the male the larger the size of his pouch and therefore the greater the number of sea horse babies in the pouch!! For example, a 5 year old adult H.reidi male may give birth to as many as 2000 babies with each spawn!!!! A young 6 month old juvenile male may only give birth to 10 or 20 babies!!! It is also more likely that the older male has been mating with the same female all is life!! Imagine the stress of not being with his " beloved" during this time!

This unnecessary "handling" or "transfer" is, of course, extremely hard on wild caught males and may cause his death immediately after giving birth. One should avoid purchasing wild caught pregnant males at all costs. It is easy to feel sorry for him in the pet store, but his purchase only encourages the collectors to take additional pregnant males the next time causing further devastation to the already highly threatened wild sea horse populations.

Certainly this "handling" or "transfer" stress is greatly reduced with the farm raised pregnant males but the general concept still applies. If you purchase a farm raised pregnant male you should not expect a male that is almost ready to give birth but one that is within 2 weeks of giving birth. The normal gestation period averages at 30 days depending mostly on species and environmental parameters such as temperature and diet.

If these 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 pregnant

If , however, you are able to keep these parameters optimum, you will have a much greater chance of being successful with your pregnant male so that you can enjoy this amazing phenomena of the pregnant male sea horse!! With a little more patience you will surely be rewarded with the great performance of the sea horse mating dance followed by the most precious site of all......the fat bellied pregnant male sea horse!!!

Aloha, Carol Cozzi-Schmar

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