I’m glad to hear that your new seahorses are doing so well.
Yes, sir, from your description it does sound like your seahorses are courting. Brightening or lightening in coloration, and synchronized swimming with intertwining tails, are the preliminary stages of courtship that seahorses engage in when in the process of pairing up and mating.
However, that does not necessarily mean that you have a male/female pair, since same-sex courting displays (both male and female) are also common when no member of the opposite sex is present. Under such circumstances, these passionate ponies are not picky about their partners — males will dance with other stallions and frustrated females will sometimes flirt with other fillies (Abbott, 2003)!
If one of your seahorses is indeed a male, that should become evident as the courtship escalates. When the seahorses are getting serious about mating, the males perform a series of vigorous pouch displays known as "Pumping" and "Ballooning" respectively, whereas the females will engage in a display known as "Pointing" prior to the copulatory rise.
Here are the type of courtship displays you should be on the lookout for that will tip you off that mating may be imminent, FERS4REEF:
Pumping and Ballooning.
Pumping and Ballooning are pouch display performed to some extent by all male seahorses regardless of species. The energetic display known as "Pumping" is a vital part of the courtship ritual in all seahorse species that have been studied to date. Temperate and tropical seahorses alike, from the smallest pygmy ponies to the largest of the "giant" species, it appears that all male seahorses perform such pouch displays.
Pumping requires a series of coordinated movements. Bending vigorously, the aroused male jackknifes his tail to meet his trunk, thereby compressing his inflated brood pouch in the middle. The male then straightens up again, suddenly snapping back to “attention” so as to relieve the pressure on his severely compressed midsection. This rapid pumping motion has the effect of forcing water in and out of the brood pouch in a manner that is virtually identical to the way the young are expelled at birth (Vincent, 1990).
The strenuous pumping action is the stallion’s way of demonstrating his pouch is empty of eggs and that he is a strong, healthy, vigorous specimen capable of carrying countless eggs (Vincent, 1990). By so doing, he assures the female that he is ready, willing, and able to mate, and that he can successfully carry and deliver her entire brood.
Pumping is an impressive display to say the least. Perhaps a bit too impressive at times. For example, I often receive emergency emails, urgent instant messages, and frantic phone calls from novice seahorse keepers who have just observed their stallions performing for the first time and are convinced something is horribly wrong. To their untrained eyes, the poor creatures appear to be in the midst of an acute attack of appendicitis or an epileptic fit, if not their death throes. The alarmed hobbyists are certain their poor pets are having violent convulsions and proceed to describe in lurid detail how the pitiful ponies are doubling over in obvious agony again and again, in the grip of seizures so severe they are all but being torn in two.
It is my great pleasure to reassure them that all is well, and that their ailing male is actually happy and healthy and very much at home in their tank to the point that he is displaying a hearty interest in mating. Indeed, the courtship display they are witnessing is an unmistakable indication that they are doing things right and that their male is quite content with the conditions they have created in the aquarium. One might only wish that all seahorse crises were so easily dismissed, so quickly resolved, and with such a happy outcome.
Courtship in many temperate and subtemperate seahorses is dominated by such pouch displays. In addition to pumping, these coldwater ponies also engage in a different type of pouch display known as “Ballooning.” This is a simple display in which they inflate their brood pouches to the fullest possible extent and parade around in front of the female in all their glory as though trying to impress her with the sheer dimensions of their pouches. The pumped up paramours perform proudly, putting on quite a show for the flirtatious fillies. (All you ladies out there are surely all too familiar with this act. No doubt you attract the same sort of attention and elicit the same type of behavior every summer at muscle beach, where all the macho men pump up their biceps, suck in their guts, and throw out their chests whenever you stroll past.)
Often all the males in the vicinity will compete for the attention of the same female, chasing after her with their pouches fully inflated this way. When all the boys are in full-blown pursuit of a female ripe with eggs, they look like a flotilla of hot air balloons racing to the finish line.
Hippocampus abdominalis, H. breviceps, and H. tuberculatus, in particular, have developed enormous pouches that are all out of proportion to their bodies when fully expanded. Their oversized pouches look like over-inflated balloons ready to burst when these stallions come a courting. Take the tiny Hippocampus breviceps, for example. With its brood pouch expanded to the maximum, a courting male looks like a fuzzy 3-inch pipe cleaner that swallowed a golf ball! Courtship in temperate/subtemperate species generally centers on pouch displays more than color changes, dancing or prancing.
Pumping is one of the final stages of courtship and it indicates the seahorses are really getting serious (Vincent, 1990). Mating will take place shortly, as soon as the female hydrates her eggs, unless something intervenes in the interim.
Pumping probably serves several important functions simultaneously, making it the courting male’s method of multitasking. It is an important part of pouch preparation and certainly indicates the stallion’s readiness to breed. No doubt Pumping also provides the female with a means of judging the merits of prospective mates. She will generally favor the stud with the greatest stamina and the largest brood pouch. And there is a growing body of evidence that suggests pumping males are releasing sex hormones that stimulate the female to ripen her eggs in preparation for ovulation, secure in the knowledge that a receptive male will be standing by, ready to receive them.
Eventually, the female will respond to repeated bouts of Pumping with a display known as Pointing, thereby signaling her eagerness to rise for the exchange of eggs.
Pointing is the prelude to mating and the transfer of the eggs. The female’s eggs will have been fully hydrated by this time, as indicated by the rounded appearance of her obviously swollen abdomen and the protrusion of her oviduct or genital papilla (Vincent, 1990). At this point, she will be anxious, even desperate, to mate. In order to ensure fertilization, the female must add water to her mature oocytes (egg cells) just prior to mating (Vincent, 1990). A ripe female is committed to mating once she has hydrated her clutch of eggs. She cannot retain the hydrated eggs indefinitely (Vincent, 1990). They can only be retained for approximately 24 hours, before they must be released. She must transfer these eggs to a receptive male within 24 hours of hydration, or lose the entire clutch.
Should she be unable to transfer them to a receptive male within that time, she risks becoming egg bound, and her only recourse is to release them into the water column, spilling her eggs onto the substrate. This is an expensive waste of precious bodily resources that must be avoided at all costs. In fact, the whole purpose of the elaborate courtship ritual developed by Hippocampus is to assure that a receptive male is standing by at the crucial moment, ready, willing and eager to accept the eggs.
The ripe female signals her urgency by "Pointing" — rising on the tip of her fully extended tail and stretching vertically towards the surface of the water while raising her upturned head until her snout points straight up (Vincent, 1990). It looks almost as if the female is answering the male’s overtures by nodding her head in assent.
Pointing is an unmistakable sign that the female is ready to rise for the nuptial embrace, which will soon take place in midwater (Vincent, 1990). Pointing thus triggers an immediate response from the male, who typically reacts by Pumping or Tilting (Vincent, 1990). At first there is a stimulus-response relationship between the pointing of the female and the pumping of the male, with one eliciting the other. This helps to coordinate the couple’s courtship, assuring that both partners are fully aroused and physiologically prepared for the transfer of eggs when the moment arrives. There is a direct correlation between the frequency of pointing and pumping and the arousal level of the female and male, and one can easily judge how soon mating will occur by noting the tempo and vigor with which they perform these maneuvers. When mating is imminent, the male often responds not by pumping, but by echoing the female’s Point with one of his own (Vincent, 1990).
If he does not take the hint fast enough, the female will push off the bottom in mid-Point and rise up alone, enticing the male to follow. After a few of these solo rises, the male will eventually get the idea, and prepare to follow her lead. The couple will then rise together for the culmination of their courtship.
This is the final phase of courtship. It is the climax of the entire affair during which the partners meet in midwater for the transfer of the eggs (Vincent, 1990). The female initiates the rise by pushing up from the bottom in mid-Point and the male immediately follows her lead. They ascend through the water column facing each other, with their heads raised high and their abdomens thrust forward (Vincent, 1990). At this point, the female’s genital papillae or oviduct will be everted and protrude slightly from her vent, and the male’s brood pouch is usually fully inflated (Vincent, 1990). As they ascend, the female often continues to Point and the male may continue to Pump (Vincent, 1990). They will meet at the apex of their rise for the nuptial embrace.
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 stream 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.
The pregnancy-sustaining changes in the male’s pouch begin the moment the last egg is tucked safely away inside this protective pocket. The male’s pouch deflates, compressing the eggs against the pouch lining in order to facilitate implantation. The male then perches and attempts to settle the eggs properly in his pouch, often undergoing a series of agitated contortions, swaying, twitching, or wagging his tail from side to side, and perhaps stretching as though trying to rearrange the eggs more comfortably (Vincent, 1990). He is dispersing the eggs uniformly throughout his pouch, giving each one the best chance to be fertilized and implant in the septum or wall of the marsupium.
Meanwhile, the female’s belly slims down noticeably as she transfers her eggs. She may lose up to 30% of her body weight after depositing a large clutch of eggs (Vincent, 1990). As a result, her abdominal plates or belly rings will be concave or pinched in for the next couple of days.
The seahorse’s charming courtship rituals and delightful displays are a wonder to behold. The grace and beauty of the courtship dance, with its carousel-like ballet and elegant parallel promenade, the rhythmical swaying and passionate performances of "Pointing" and "Pumping," and the fabulous midwater finale all combine to create an unforgettable spectacle that’s unprecedented in all of nature.
Best of luck with your seahorses, sir! It’s encouraging that they are showing a healthy interest in courtship and mating.