Re:Sunburst Turning Different Color

Pete Giwojna

Dear Joe:

Yes, Sunbursts can and will change coloration in response to a wide range of environmental influences, hormonal changes, social interactions, and many other factors. In other words, the color change you noted is probably perfectly normal and does not indicate poor health. In your case, there are two common reasons why your Sunbursts may have changed their coloration that come to mind off the top of my head.

The first reason is to blend in with the rest of your herd. This works both ways, by the way — a drab black or brown seahorse may brighten up and adopt a vivid coloration when placed amongst brightly colored seahorses. Or a bright yellow or orange seahorse will sometimes darken in coloration when placed amidst the herd of drab seahorses. This is a protective mechanism — in nature, it’s dangerous to stick out from the rest of the herd and attract the unwanted attention of potential predators to oneself.

The second reason brightly colored seahorses will darken in a new aquarium is if the lighting is too intense. In nature, bright light means exposure to harmful ultraviolet radiation, and the seahorses respond by producing excess melanin, just as people will develop a dark tan in the summertime if they spend a lot of time in the sun. For this reason, seahorses that are displayed under metal halide lighting may darken in coloration due to the excessive production of melanin.

Adding some colorful hitching posts will often encourage seahorses to display brighter colors, Big Joe. For a complete discussion of how and why seahorses change color, please check out the a two-part article on coloration in seahorses that I recently wrote for Conscientious Aquarist online magazine. You can read the articles at the following URL’s and enjoy Leslie Leddo’s magnificent photographs. Pay close attention to part two of the article, sir — it explains the different factors that can have an adverse affect on a seahorse’s coloration and discusses how to keep your seahorses looking their best and brightest in some detail:

part one:

part two:

If your existing female is a Mustang (Hippocampus erectus), it’s certainly possible that she may mate with your male Sunburst (H. erectus). They would produce perfectly viable offspring but it’s difficult to predict what their progeny may look alike due to the tremendous genetic diversity that’s characteristic into this line of seahorses. Their offspring would have varying genotypes and display a variety of phenotypes.

When discussing Ocean Rider’s strains of cultured Hippocampus erectus, such as Mustangs and Sunbursts, it’s important to understand two things. First of all, as intraspecific hybrids, their H. erectus have a great deal of genetic diversity built right into them, so that they are the very epitome of hybrid vigor. That’s partly what makes them so healthy and hardy. Secondly, Sunbursts are not mutations or homozygous recessives. Allow me to elaborate.

Mustangs and Sunbursts are different color morphs of the same species (Hippocampus erectus). As such, they have identical aquarium requirements, interbreed freely, and are equally hardy. Sunbursts are a bit smaller than Mustangs on average, topping out at around 5-6 inches, whereas the ‘stangs can reach well in excess of 6 inches in length.

But they differ primarily in their coloration: Mustangs tend to be darker colored, displaying the dominant dark brown to black coloration that is so typical of wild erectus, whereas the Sunbursts tend to be more brightly colored, and typically display the much less common yellow to orange color pattern.

But it’s important to note that the Sunbursts are not genetic mutations that are locked into specific colors. Colorful Ocean Riders are not homozygous recessives nor or they mutations that are unable to manufacture certain pigments altogether. In other words, they are not like albinos that are always white because they lack the ability to produce melanin (black pigment), nor are they like lutino mutations that are always yellow because they lack the ability to manufacture any pigments other than yellow. But they do exhibit differential proliferation of chromatophores and this gives each type a predisposition to display certain colors.

Mustangs, for example, have a preponderance of melanophores (black pigment cells) and 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.

Although yellow and orange pigments tend to predominate in Sunbursts, they are equipped with a full range of chromatophores and can display a wide range of colors. This means they are predisposed towards the sunset colors (yellow, gold, peach and orange) when conditions are to their liking. However, they have a complement of melanophores in addition to their bright pigment cells and are able to change their coloration to reflect changing circumstances and conditions. So yellow and orange are the most commonly seen colors in Sunbursts, but you also find them in white, pearly, tan or even brown color phases from time to time.

In short, Mustangs exhibit the normal coloration for wild H. erectus and tend to be darker colored as a rule, but will show brighter color phases from time to time. Likewise, Sunbursts tend to exhibit the sunset colors when conditions are favorable, but they also display darker color phases on occasion.

You can expect both Mustangs and Sunbursts to go through quite a range of color phases from month to month. For example, I have watched my pair of Mustangs go through a number of color changes over the years. One has settled on a dark grayish -green as its base coloration for the moment, and the other ranges between rust, chocolate brown and russet-brown, but always with contrasting beige bands. Last season, the male adopted a deep burnt umber as his everyday attire (still with the same beige saddles, 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.

Sunbursts exhibit equally variable coloration from month to month and are just as hardy as the Mustangs. Of course, the two types make great tankmates for one another.

To understand how the tremendous genetic diversity that’s built into Mustangs and Sunbursts is reflected in their offspring, let’s start with the basics. Essentially, when they begin working with a particular species, Ocean Rider’s approach is to obtain sufficient broodstock from throughout their range to completely eliminate any concerns about inbreeding, and then to pair males and females from different bloodlines in order to achieve intraspecific hybridization. That way, each pairing actually increases the genetic diversity of the offspring, and providing you avoid brother-sister crosses when you subsequently select your breeders for the next generation, each new generation will actually be strengthened (more genetically diverse than their parents) through the phenomenon of hybrid vigor.

This is especially true considering the primary traits Ocean Rider selects for are adaptability, disease resistance, vigor, aggressive feeding habits, and rapid growth. Far from being recessive characteristics that could eventually result in inbreeding, these are all adaptive traits that increase the line’s fitness and improve survivorship. In fact, they are the same sort of traits Mother Nature herself selects seahorses for in the wild to assure survival of the fittest. When nature culls out the weakest and least fit, it is known as "natural selection." It is nature’s way of keeping a species strong, vigorous, and adaptive (i.e., evolving to better fit its niche). The only difference is that Mother Nature is selecting for suitability to their natural habitat, whereas aquaculturists are selecting seahorses for fitness to captive conditions. In both cases, the selection process assures that the specimens become ever stronger and better adapted to their environmental niche, whether that is the aquarium or the ocean itself.

Practiced in this manner, selective breeding actually strengthens and improves a strain generation by generation, producing seahorses that are progressively hardier and better suited for aquarium life. This level of domestication not only improves their general health but also eliminates much of the stress wild seahorses experience in captivity, allowing cultured seahorses not only to live longer but to live better.

Initially, the breeders’ goal is not to rear the maximum number of offspring from each brood, but to assure that the weaker offspring are weeded out at every stage, and that only the fittest fry are selected for further rearing. As a result, it typically takes Ocean Rider several generations to strengthen a new line of seahorses in this manner before it is ready to bring to market.

It’s a good system: a multigenerational approach to rearing which assures that farm-raised seahorses will only continue to get stronger, hardier, and more trouble free over time as they become ever better adapted to aquarium conditions

When you consider that Ocean Rider has been working with Hippocampus erectus since 1998, producing dozens of generations of Mustangs and Sunbursts, each more genetically diverse than its predecessors, it’s easy to understand why there is so much variation within a given brood of seahorse fry. It is very commonplace for brothers and sisters in the same brood to express differences in variable trait’s such as coloration, spininess, the size and shape of the coronet, the presence or absence of cirri, and so on.

In short, within the same brood of young, it is quite common to have some juveniles that are very spiny along with others that are very smooth skinned. In the same brood, there may be some fry with all well-developed coronets and others with only low, rounded bumps, and many whose crowns are somewhere in between those extremes. There may be a few fry with very elaborate cirri adorning their heads and necks, whereas most of their brothers and sisters have no cirri at all. The same variability in coloration holds true as well.

For example, Mustangs produce offspring that typically display the dark coloration and lined pattern so characteristic of wild H. erectus. But in a large brood of Mustang fry, there will typically be a few specimens which display yellow or orange as their background coloration.

A brood of Sunburst fry likewise displays variable coloration. Because Sunbursts are not homozygous recessives, most of the fry they produce express the typical dominant dark coloration of wild erectus, not the bright coloration of their parents.

It’s all a function of the tremendous diversity that’s built right into the genes of Mustangs and Sunbursts as intraspecific hybrids.

Best of luck with your seahorses, Big Joe! Here’s hoping they are fruitful and multiply, and provide you with many brightly colored offspring.

Happy Trails!
Pete Giwojna

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