Part II

How They Do It and How to Keep Seahorses Looking Their Best and Brightest

by Pete Giwojna and Ben Giwojna

In the first part of this article we explored some of the ways seahorses employ their remarkable ability to change coloration.  We discussed how our amazing aquatic equines rely on color for camouflage, their complex social interactions and courtship rituals, and to express their mood and emotional state.  Now that we have laid the groundwork, we can examine what gives the seahorse its chameleon-like abilities and explore some of the things aquarists can do to help kep their seahorses looking their best and brightest.

Hippocampus accomplishes its dramatic color changes through the contraction or expansion of pigment cells known as chromatophores. Each chromatophore is a contractile cell or vesicle containing liquid pigment or pigment granules and capable of changing its form or size, thus causing changes of color in the skin of the animals that possess them.  The chromatophores may be under nervous control and able to change very rapidly or under hormonal control and able to change only relatively slowly.

In seahorses, the chromatophores are branched (dendritic) cells, within which the color pigment can be moved (Tamaru, Sep. 2001).  When a chromatophore contracts, all of its pigment is concentrated in one small spot in the center of the cell, resulting in the loss of color in the fish (Tamaru, Sep. 2001).   When a chromatophore expands, the pigment spreads throughout the entire cell to all its branches, resulting in bright color (Tamaru, Sep. 2001).  Muscles attached to the chromatophores can also move the pigment cells a little closer to or a little further away from the surface of the skin (Walls, 2004).  When the pigment cells are close to the surface of the skin, the color is bright and clear; when the pigment cells are further away from the surface, the color is muted and more diffuse.

Different types of chromatophores contain different pigments such as melanin (black), xanthin (yellow), lipochrome (orange), erythrin (red) and so on (Cusick, 2004).  The different types of chromatophores are named according to the type of pigment they contain (e.g., melanophores, erythrophores and xanthophores).  These specialized pigment cells are usually stacked upon each other or clustered in groups (Tamaru, Sep. 2001).  Hippocampus is typically endowed with just a few different types of chromatophores, and all other colors are derived from these 3 or 4 basic pigments.  The exact color the seahorse displays at any given time therefore depends on the concentration of these pigment cells, how close the cells are to the surface of the skin, and which chromatophores are expanded or contracted at the moment (Cusick, 2004).

For example, seahorses have no blue pigment cells, but the color blue can be approximated nonetheless.  A low concentration of melanin (black pigment) deep in the dermal layer gives the skin of the fish a bluish cast (Cusick, 2004).   Achieving a blue tint in this way while simultaneously expanding xanthophores (yellow pigment cells) produces shades of green, and maintaining a bluish background color while opening erythrophores (red pigment cells) yields shades of purple and violet.  Likewise, a seahorse that has no orange pigment cells can still assume a bright orange coloration by simultaneously expanding its xanthophores (yellow pigment cells) and erythrophores (red pigment cells) to the fullest.  The exact shade of orange it becomes and its brightness is determined by the proportion of yellow to red cells it opens, how fully they are expanded, and how close to the skin's surface they are.  Obviously, a seahorse that is black has all its melanophores expanded and a seahorse that is white has ALL of its chromatophores contracted so that all the wavelengths of visible light are reflected back to the observer, and so on. 

In seahorses, melanophores are the most common of these pigment cell types (Tamaru, Sep. 2001).  They contain the pigment melanin, which gives most seahorses their typical black or dark brown coloration.  Essentially melanin absorbs the entire visible light spectrum and looks black because no light is reflected back to the observer (Tamaru, Sep. 2001).  When a melanophore is open and fully expanded, the melanin it contains is dispersed throughout the cell, and when all the melanophores are opened at once, melanin is distributed evenly across the surface of skin, rendering the seahorse black (Tamaru, Sep. 2001).  Seahorses typically respond to stress by expanding their melanophores and darkening this way.

The different types of pigment cells seahorses possess vary from species to species.  Hence, not all seahorses have the same palette of colors at their disposal.  Some seahorses can never turn red because they lack erythrophores; red is simply not in their wardrobe.  In general, tropical seahorses tend to have brighter colors in their repertoire than temperate species.  And deep-water seahorses often have more red and orange pigment cells than other seahorses.  In order words, different seahorse species have different coloration due to the differential proliferation of chromatophore cell types.

Depending on the species, the results can be very striking.  For example, the painted seahorse (Hippocampus syndonis) from Japan can adorn itself in a psychedelic or Harlequin-like pattern of riotous colors ranging from the richest crimson to brilliant saffron yellow (Walls, 2004).  Of course, the flamboyant reddish, bright yellow, and blazing orange color morphs of the Brazilian seahorse (H. reidi) are almost legendary among aquarists.  Nowadays, a boldly colored Pinto or dazzling SunFire from Ocean Rider is the crown jewel in many a seahorse keeper’s collection.  And almost all species of seahorses can adopt cryptic coloration featuring contrasting blotches, splotches, saddles, stripes, bars, speckles, lines and dots that serve to break up their silhouette and disguise their shape (walls, 2004).

Some species of seahorses such as H. erectus have been captive-bred-and-raised for more than 20 generations and domesticated seahorses are now available in virtually every color of the rainbow.  However, most strains of colorful cultured seahorses are not homozygous recessives nor are they mutations that are unable to manufacture certain pigments altogether.  But they have been selectively bred to exhibit differential proliferation of chromatophores and this gives each type a predisposition to display certain colors.  For example, Mustangs (Ocean Rider's strain of H. erectus) have a preponderance of melanophores, and therefore tend to be dark (earth tones) or cryptically colored most of the time. But 'stangs also have bright pigment cells and they can brighten up when the occasion calls for it, such as during courtship or when competing for mates.

I own a pair of these spirited steeds myself, and have watched them go through a number of color phases from month to month. One has settled on gray-green as its base coloration for the moment, and the other ranges between rust, burnt umber, and orange, but always with contrasting beige bands. Last season, the male adopted a rich ochre yellow as his everyday attire (still with the same beige bands, though), while the female displayed a dark purplish ensemble with definite greenish highlights. When courting, they consistently brighten to a pearly white and a creamy yellow respectively. They make a handsome couple, and I find my Mustangs to be very attractive specimens in all their guises.

On the other hand, Sunbursts are a different color morph of H. erectus that has also been developed by Ocean Rider.  Sunbursts are equipped with a full range of chromatophores (pigment cells) and can display a wide range of colors, but as their name suggests, they are predisposed towards the sunset colors (yellow, gold, peach and orange) when conditions are to their liking. They have proportionally fewer melanophores (black pigment cells) than Mustangs, which are typically dark brown or black, so the background or base coloration of the Sunbursts tends to be lighter. Yellow and orange specimens predominate, but they also display whitish, tan, pearly and even brown color phases at times.  Hobbyists can expect their Sunbursts to go through a number of color phases and color changes over the months.

The hobbyist should also be aware that there are any number of environmental conditions and hormonal influences that can affect the coloration of seahorses in the aquarium, often by affecting the ability of chromatophores to contract and expand. These include the following factors:

Stress -- seahorses often respond to stress by darkening.

Emotional state -- when excited, seahorses typically brighten in coloration, reflecting a state of high arousal. On the other hand, fear, anxiety and distress are generally accompanied by dark, somber hues.

Social interactions -- seahorses often brighten during their courtship displays; pair-bonded seahorses likewise brighten during their morning greeting rituals, and rivals go through characteristic color changes (see Part 1 of this article in the previous issue of Conscientious Aquarist) during their confrontations and competitions.

Competition for mates -- dominant individuals brighten; subordinate seahorses darken in submission.

Poor water quality -- high levels of nitrogenous wastes (e.g., ammonia, nitrite or nitrate) can cause chromatophores to contract and colors to fade.

O2/CO2 -- low oxygen levels (or high CO2 levels) can cause colorful seahorses to fade and they will blanch when subjected to hypoxic conditions.

Background colors -- seahorses will often change color in order to blend in with their immediate surroundings.

Medications -- some antibiotics and malachite-green-based remedies negatively affect color (Cusick, 2000).

Tankmates -- seahorses may change their base coloration to blend in with the rest of the herd or to match their mate (or a potential partner). This can work both ways: a dark seahorse may brighten up and assume vivid hues when introduced to an aquarium with bright yellow or orange tankmates, just as a brightly colored seahorse may darken and adopt subdued coloration when placed amidst drab tankmates. Of course, seahorses are not responding to peer pressure when they conform in this manner; rather, this is probably instinctive behavior. In nature, it's not healthy to be too conspicuous and stick out in a crowd since an individual that stands out from the rest of the herd draws the attention of potential predators to itself.

Temperature -- chromatophores tend to contract at high temperatures (above the seahorse's comfort zone), causing colors to fade; cooler temps within their optimal range can make pigment cells expand, keeping colors bright.

Disease -- skin infections (bacterial, fungal, or parasitic) can cause localized loss of pigmentation or discoloration of the affected areas.

Diet -- seahorses cannot synthesize the pigments used in their chromatophores. It is therefore important to enrich their food with pigments such as carotenoids in a form that's easy for them to absorb. If color additives are not provided, the chromatophores will gradually lose their pigments and the seahorse's color can fade (Giwojna, 2002). Vibrance, for example, is exceptionally rich in Vitamins A and C as well as natural carotenoids, which are not found in the frozen Mysis that serves as the staple diet for most seahorses. This is important because the carotenoids are a class of yellow to red pigments, which include the carotenes and the xanthophylls (Giwojna, 2002). Like all cells, individual pigment cells have a limited life expectancy in the body and must be regularly renewed. Marine organisms cannot synthesize carotenoids, so if they do not receive adequate amounts in their diet, they will have difficulty replenishing their red and yellow pigments (Giwojna, 2002). This means that the colors of bright yellow, orange, and red seahorses will gradually fade over time if their daily diet is lacking in carotenoids. So don't neglect the enrichment step in your daily feeding regimen! If seahorses are fed a strict diet of Mysis without additional enrichment, they may begin to develop dietary deficiencies over time, and both their health and coloration will eventually suffer (Giwojna, 2002).

Lighting -- seahorses may darken in response to UV radiation or excessively bright lighting, producing excess melanin as a protective measure, whereas bulbs that emit wavelengths of light shifted towards the red end of the visual spectrum (i.e., Grolux fluorescent tubes) can greatly enhance the coloration of red, orange or purplish seahorses to the point that they almost literally glow.

All of the different factors mentioned above need to be addressed in order to keep your seahorses looking their brightest   For instance, this is what I recommended in that regard in an article titled, "Ocean Rider: A Horse of a Different Color," which appeared in the June 2002 issue of FAMA magazine:

All seahorses may respond to stress by darkening and expanding their melanophores to signal their distress (Giwojna, 2002).  When that happens, it doesn't matter how brilliant their normal coloration may be, since the melanin absorbs the entire visible spectrum (black is essentially the absence of color) and none of the underlying colors are able to shine through (Giwojna, 2002).  Consequently, seahorses may never color-up and look their best if subjected to dubious water quality, unacceptable aquarium parameters, an inadequate diet, or other stressful conditions. 

When setting up and maintaining your seahorse tank, your primary goal must therefore be to provide your seahorses with a stress-free environment that meets all of their requirements.  Begin by making sure your saltwater tank is properly cycled and by maintaining your water quality within the following parameters: pH 8.2-8.4, specific gravity 1.021-1.025, temperature 72°F-75°F (Giwojna, 2002).  Those are the optimal readings for most of the cultured tropical seahorses that are now available.  Strive for stable readings within those limits, and maintain zero ammonia and nitrite at all times (Giwojna, 2002).

Elevated nitrates are also stressful to seahorses over the long term, and can keep your seahorses from looking their brightest.  For best results, consider using live rock and/or a live sand bed (preferably situated in your sump) in conjunction with a good protein skimmer to help filter your seahorse setup (Giwojna, 2002). The skimmer will remove excess organic compounds before they enter the nitrogen cycle, and live rock and a deep sand bed will provide significant denitrification ability, all of which will help keep your nitrates down (Giwojna, 2002).  Don't overstock, don't overfed, remove leftovers promptly (a good clean-up crew is useful here), practice good aquarium maintenance and maintain a sensible schedule for water changes (Giwojna, 2002)

Some potential stressors, such as shock and vibration or excess noise and traffic, can be eliminated altogether during the planning stage.  The medium of water transmits certain sounds wonderfully well--far better than air, in fact--and like all fishes, seahorses have organs specially designed to detect such vibrations, and are sensitive to external noises and outside sources of shock and vibration (Giwojna, 2002).  Whether it's a clunky air pump or compressor, the buzzing ballast from an aquarium reflector, the rattling impeller from a noisy power filter, or something totally unrelated to the aquarium, like a nearby clothes washer/dryer, dishwasher, stereo, television or some such appliance, any source of bad vibes can subject seahorses to chronic low-level stress (Giwojna, 2002).  Footfalls and nonstop passersby in heavy traffic areas can also be alarming to wild-caught seahorses, and when they feel threatened they react by darkening or assuming cryptic coloration, resorting to camouflage in order to conceal themselves in the face of potential danger (Giwojna, 2002). (Note: this is not a concern with domesticated seahorses, which are very social, highly gregarious animals that are very much accustomed to the human presence.  They will thrive in a high traffic area such as your living room or den or family room.)

To avoid this sort of stress, choose the location for your seahorse tank with care, dampen all potential sources of shock and vibration, and provide a thick pad (cork or Styrofoam is ideal) beneath the tank to deaden vibrations and soften any shocks that might otherwise be absorbed through the base of the aquarium.  If you're keeping skittish wild-caught seahorses, the aquarium should be situated in a relatively quiet room away from major traffic areas, blasting stereos, blaring TVs and noisy kids (Giwojna, 2002).  If you have modified your laundry room, utility room, or workshop so it can do double duty as your fish room, you may want to find a less mechanically cluttered area for your seahorses (Giwojna, 2002).

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 (Giwojna, 2002).  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 (Giwojna, 2002).  Think of it as an extraordinarily cheap, yet effective life insurance policy that can save your fish-and your hide-in the event of an electrical accident while working on your tank.

As previously discussed, diet also plays an important role in keeping your seahorses healthy and looking their best.  Captive-bred-and-raised seahorses are trained to eat a diet of frozen Mysis enriched with Vibrance.  In my opinion, the freshwater Mysis relicta (from Piscine Energetics) are a super food for seahorses, extremely rich in protein and essential fats.  In general, the total fat content of freshwater feeder fish and inverts (e.g., FW ghost shrimp and glass shrimp) is shockingly low, but Mysis relicta is a remarkable exception which has several times the fat levels of even highly desirable marine feeder organisms such as saltwater Penaeus shrimp (Giwojna, 2002).  But as nutritious as it is, Mysis relicta is not a suitable long-term diet for seahorses on its own, and Vibrance has been specially formulated to add certain vitamins, minerals, and additional long chain fatty acids that M. relicta lacks (Giwojna, 2002). 

For instance, Vibrance contributes high levels of HUFAs (highly unsaturated fatty acids) including the DHA omega 6 and omega 3 series, which are extra long chain fatty acids that are absent in virtually all live and frozen feeds (Giwojna, 2002). Most marine organisms, seahorses included, cannot synthesize these long chain fatty acids and must obtain them through their diet.  DHA, for instance, has been proven to be essential to high survivability, nerve development, stress management, and proper reproduction in fishes (Giwojna, 2002).  The combination of Mysis relicta enhanced with Vibrance is a superb, nutritionally complete diet for seahorse that contains everything they need for vibrant good health and long-term survival (Giwojna, 2002).  And as we've already discussed, Vibrance is also exceptionally rich in Vitamins A and C as well as natural carotenoids, which are not found in Mysis relicta.  It will provide your seahorses with the pigments they require to keep their colors vivid.

Aside from providing your seahorses with optimal water quality, a stress-free environment, and an ideal, enriched staple diet, you must also take care to furnish your aquarium in a manner that will encourage them to display their brightest colors.

Real or artificial, living or cured, it doesn't seem to make a difference -- branching sponges are veritable magnets for seahorses.  Colorful natural hitching posts like this will encourage brightly colored seahorses such as this Ocean Rider Hippocampus erectus to retain their vivid wardrobes."  Photo by Leslie Leddo

In a drab, largely monochromatic setting, seahorses may never look their best (Giwojna, 2002).  For instance, if you introduce your Sunbursts or Brazilian seahorses to an aquarium decorated primarily with the bleached white bones of coral skeletons and a substrate of dolomite, crushed coral or coral sand, you can expect their bright hues to fade quickly.  Seahorses rely on crypsis and their ability to blend into their background in order to avoid predators and stay out of trouble, and brightly colored seahorses will feel vulnerable and exposed in such a bleached coral seascape (Giwojna, 2002).  They will either adopt pale colors or a generalized, drab, nondescript, cryptic color pattern that makes them less conspicuous.  The same is true if their tank features algae-covered rock, loads of Caulerpa, and lots of other macroalgae, and is dominated by browns and greens.  Bright red and orange seahorses may not feel at home amidst algal mats or this sort of seagrass habitat, and are apt to revert to earth tones, cryptic patterns, or shades of olive drab (Giwojna, 2002).

Therefore, in order to show off your colorful seahorses to full effect and encourage them to live up to their potential and retain their true brilliance, it's a good idea to provide them with a colorful natural setting that will make them feel right at home (Giwojna, 2002).  This means furnishing their aquarium with appropriate, multi-colored décor.  Reef tanks featuring colorful sponges, mushrooms, leathers, and other seahorse-safe soft corals and gorgonians are ideal, guaranteed to keep seahorses feeling right at home and looking their best (Giwojna, 2002).  If you're not a reefer, you can often achieve the same effect using "faux" coral, plastic gorgonians and replicas of marine plants to encourage them to retain their natural coloration. Various types of Caulerpa, Gracilaria, and other attractive macroalgae can then be added to give your tank a welcome touch of green, red, gold and add a bit of living color (Giwojna, 2002).  Many hobbyists find that a dark substrate, such as black sand, brings out their seahorses' brightest colors and sets off their vivid hues exceptionally well, as well as being aesthetically pleasing (Giwojna, 2002).

Pay special attention to the hitching posts you select. Strive for bright reds, oranges, and yellows in anything your seahorses may adopt as a holdfast (Giwojna, 2002).  These aquatic equines -- especially the stallions -- will often choose one particular hitching post as their home base and spend much of there time perched right there (think of your Dad hunkered down in his favorite easy chair in the den).  Once they adopt a favorite base of operations like this, they will often proceed to change coloration to match their preferred resting spot (Giwojna, 2002).  So you want to encourage them to adopt one of the more vivid pieces as a favorite holdfast.

Mildred Bellomy provides a perfect example of how this works in the Encyclopedia of Seahorses:

Elizabeth Goetz of Miami, Florida has kept one or more seahorse stables in her home for many years.  She wrote the following anecdote about one of her seahorses that "turned red with envy."

"About five or six years ago, it was just about this time of year, [Christmas], we began our holiday decorating.  Our own is not the simplest place to decorate for special occasions in that we have so many aquariums -- approximately 35 at the time.  Fourteen of these tanks were the homes of seahorses (Hippocampus hudsonius).  [Author's note: Hippocampus hudsonius is an outdated synonym for Hippocampus erectus.] 

"After completing the superficial home decorating, we decided it would be a grand idea to really go all-out with the holiday scheme and include the aquariums.  On checking through our collection of assorted Christmas bric-a-brac, we found a number of ceramic items suitable for display in sea water.  There were Christmas trees in north-woods green, gaily ornamental angels lovely enough to have stepped from the very gates of Heaven, winged carolers, haloed mermaids, etc., and lo and behold! -- one, red-robed, sitting Santa Claus, with the most adorable facial expression one could imagine.  Here, then, was ample material to decorate to one's heart's content.

"The walls of the dining room are lined with 10- and 15-gallon aquariums so we chose the most prominent 15-gallon tank for this pixie-like Santa.  This was the home of five seahorses and they, too, seemed really happy with the decorating idea.  We will not argue the point that any other smooth ceramic piece would have pleased them equally, but it is more satisfying to believe that the seahorses joined in with the holiday spirit.  Nevertheless, almost as soon as their former hitching posts were removed and a Christmas item put in its place, the seahorses wrapped their respective tails around the new items and were completely at home again.  Though scientists may adamantly disagree, we firmly believe fish do have varied personalities, even within their own species.  Ask any hobbyist.  We have had friendly seahorses, unfriendly ones, and downright cussed critters; the timid, placid, bold, and boisterous, and all of these and more personality traits were observed in H. hudsonius alone. 

"All of the foregoing is merely to set the stage for our tale of the seahorse that turned red with envy. 

"Our little seahorse star of this story was the most calm and timid of the five in our Santa aquarium.  He would cruise calmly from his hitching post for exercise and return to his own station a short distance from the Santa, never trying to usurp the throne of another of his tankmates.  The others did claim Santa as a resting place.  Seldom was the time when Santa didn't have the tail of a seahorse wrapped gently around an arm that rested on his pack, or around the tipped-up tassel of his toboggan.  Our calm but "envious one" would stare in Santa's direction almost constantly, while resting.  It might be well, at this point, to emphasize that Santa was the only red-colored object or part of this aquarium.  This previously dark (brownish) seahorse -- originally colored the same as the other four -- turned bright red.  His change occurred gradually, over a period of about a week and it is quite true, he became a most beautiful red for the holidays."

Now we are well aware of color changes in nature, assumedly for protective measures, and being mindful of the fact that this timid little fellow did not cling to red-robed Santa, but remained some distance away, what then could the whimsical-minded, season-inspired person presumed other than that the most peace-loving seahorse in the aquarium bathed himself in the reflected glory of the mythical man-of-the-hour, the one and only Santa Claus.

Notice that the seahorse reverted to its usual dark brown coloration when the scarlet-clad Claus figurine was removed from the aquarium after the holidays.

The moral of this story is that you can never tell what might catch your seahorse's eye and trigger a corresponding color change in response to a change in its immediate environment.  With that in mind, some hobbyists have experimented with brightly colored aquarium backgrounds and achieved surprising results.  For instance, I have received reports that a bright orange aquarium backing can stimulate vivid color changes in some seahorses (Abbott 2003), although the result is often not what you would expect. (One wonders if Hippocampus perceives all colors the same way we do.)  Don't hesitate to experiment until you find the right combination that works well for both you and your seahorses.

Transitory color changes can be achieved rapidly, in a matter of moments, but long lasting transformations occur gradually, and may take days to complete.  This is often the case when a seahorse adopts a favorite hitching post and makes it his home base or center of operations.   When that happens, the seahorse will often assume a color that closely matches its chosen resting spot so it blends in with its background when hanging out at headquarters.  This is akin to the situation with the ceramic Santa; the color matching occurs slowly and, once the transformation is complete, the seahorse intends to keep its new coloration indefinitely.

A good way to tip the odds in your favor is to acquire one or more tree sponges for your seahorse tank.  Tree sponges are usually brightly colored (red and orange shades are common) and their shape and texture seem to make them irresistible to seahorses as hitching posts (Giwojna, 2002).  Real or artificial, living or cured, it doesn't seem to make a difference -- branching sponges are veritable magnets for seahorses.  Very often, all the seahorses in the tank can be found clinging to the same tree sponge together, eschewing other nearby holdfasts that appear every bit as comfy and attractive to human eyes (Giwojna, 2002).  Tree sponges are everything both you and your seahorses are looking for in terms of aquarium décor.

In short, provide your seahorses with optimal water quality, a nutritious diet rich in carotenes and natural color enhancers, and a complex stress-three environment with colorful aquascaping, and they will reward you with vibrant good health and remain at their peak of coloration.

References

Abbott, Alisa Wagner.  2003.  The Complete Guide to Dwarf Seahorses in the Aquarium.  Neptune City, NJ: TFH Publications.

Bellomy, Mildred D. 1969.  Encyclopedia of Seahorses.  Jersey City, NJ: TFH Publications.

Cusick, Terry.  2000.  "Where'd the Color Come From?" Barbels: Selected Articles. Mar. 2000 (accessed 2 Feb. 2004).  <http://www.nfkc.info/barbels003.htm>

Giwojna, Pete, unpublished text.  Complete Guide to the Greater Seahorses in the Aquarium.  Neptune City, New Jersey: TFH Publications. 

Giwojna, Pete.  Jun. 2002.  "Ocean Rider: A 'Horse of a Different Color, Part II."  Freshwater and Marine Aquarium

Tamaru, Dr. Clyde, and Carol Cozzi-Schmarr.  Sep. 2001.  "Horse Forum."  Freshwater and Marine Aquarium.  <http://www.oceanrider.com/articledetail.asp?ArtNo=8>  (accessed 28 Jan. 2004),  part of Ocean Rider Articles <http://www.oceanrider.com/articles.asp>

Wallis, Catherine.  2004.  Seahorses: Mysteries of the Oceans.  Bunker Hill Publishing Inc. Charleston, MA 02129.  USA

 

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