Pygmy Seahorses: Amazing Camouflage in Animals
Camouflage is a wonderful method for animals to protect themselves from predators. By mimicking the color and texture of their background, prey animals can become almost invisible. Some animals blend in with their surroundings so successfully that it's even hard for humans to distinguish them from their environment. Two animals with this impressive camouflage are the Bargibant's pygmy seahorse and the Denise's pygmy seahorse.
Pygmy seahorses are tiny animals that live in the tropical oceans of Southeast Asia. Most are no more than 2.5 cm (0.98 inches) in length. At the moment there are seven known species plus one that has been reported but not yet given a scientific name. Scientists suspect that there are more species waiting to be discovered. Their small size, camouflage techniques, and nocturnal activity often cause the animals to be overlooked.
All seahorses belong to the family Syngnathidae and the genus Hippocampus. The genus name comes from two Ancient Greek words: hippos, which means horse, and kampos, which means sea monster.
Life Among Sea Fans
Bargibant's and Denise's pygmy seahorses live amongst much larger animals called sea fans. A sea fan is actually a colony of small animals known as polyps. It has a branched, fan-like structure made of calcium carbonate and protein and resembles coral. The branches bear bumps, which each contain a polyp. The polyp is a soft-bodied creature that has tentacles around its mouth. The tentacles are extended at times to sweep food into the mouth. Sea fans are sometimes known as gorgonians.
Pygmy seahorses are often very hard to see as they rest on a branch of a sea fan, since the appearance of their body surface resembles that of their background. Their bodies are covered with tubercles (rounded bumps or projections) that look like polyps as well as stripes and spots that help them blend in with their background.
Pygmy seahorses are all small animals, with a length of about 1.4 to 2.7 cm (0.55 to 1.06 inches). They are a type of fish, although they don't look very fish-like. They live in a region of ocean known as the Coral Triangle. This area is surrounded by Malaysia, Indonesia, Papua New Guinea, and the Philippines. Some pygmy seahorses live amongst sea fans, some live in coral reefs, and some are free living.
The fish have short snouts, making them look rather like baby full-sized seahorses. They also have prehensile tails that can curl around objects and grip them. They have only one gill opening, which is located on the back of their head. Other seahorses have two gill openings, with one opening on each side of their head. The fish feed on small crustaceans that are present in seawater, such as brine shrimp. They suck their prey into their digestive tract through their tubular mouth.
As in bigger seahorses, the male pygmy seahorse broods the young. However, while other seahorses hold their young in a pouch under their tail, pygmy seahorses hold the developing youngsters in a pouch in their trunk. (The three parts of the animal's body are the head, trunk, and tail.) The pouch has a slit-like pore for egg entry and the release of the young.
Masters of Disguise
Pygmy seahorses perform ritualized courtship behaviors before egg release. During courtship they greet each other, synchronize their movements, and wrap their tails around each other. After these rituals, the female transfers unfertilized eggs from her body into the male's brood pouch through a structure called an ovipositor. The eggs are fertilized by the male's sperm inside the pouch.
The eggs develop into young seahorses within the pouch, which provides the correct chemical environment for the eggs and protects them from injury. When the youngsters are ready to face the world, the male seahorse forcibly expels them. He may become pregnant again almost immediately.
According to Richard Smith, a biologist who specializes in pygmy seahorses, the Denise's pygmy seahorse has a gestation period of about eleven days. The male gives birth to between 6 and 16 youngsters. The youngsters settle on an appropriate host and after a few days develop a color that matches the host. It's not known if pygmy seahorses can change color if they move to a new host which has a different color.
Courtship, Babies, and Color Change
Unfortunately, because pygmy seahorses are so hard to detect, we don't know how many of the fish exist or whether their population is increasing, staying the same, or decreasing.
The Bargibant's or Bargibanti's Pygmy Seahorse
The Bargibant's pygmy seahorse, or Hippocampus bargibanti, was the first pygmy seahorse to be discovered. It was found accidentally in 1969. A scientist had collected a sea fan to bring into a museum. As he examined the sea fan in the lab, he was amazed to see two tiny seahorses amongst its branches.
Although the Bargibant's pygmy seahorse is very small, it's big compared to most other pygmy seahorses and may reach as much as 2.7 cm in length. It's always found around a sea fan belonging to the genus Muricella.
The body of the seahorse is covered with tubercles. The animal's color depends on the species of Muricella that is acting as its host. If the polyps of the sea fan have red tentacles (Muricella plectana), the seahorse is a light grey or pale purple color with red tubercles. The surface of the seahorse is also speckled and striped with red marks, similar to those found on the branches of the sea fan. The tubercles resemble slightly open polyps that are showing their red tentacles.
Sea fans with yellow to orange polyps (Muricella paraplectana) are inhabited by a different variety of the Bargibant's pygmy seahorse. This variety has a yellow body with orange tubercles.
There are several versions of the common name of the fish. The terms Bargibant, Bargibant's, Bargibanti, and Bargibanti's are all used. Whatever it's called, the seahorse is a very interesting creature.
Life in the Wild
Denise's Pygmy Seahorse
The Denise's pygmy seahorse (Hippocamous denise) is smaller than the Bargibant's seahorse and is usually around 1.6 cm in length. The animal is often orange in color and has orange tubercles. These colors help it to blend in with orange sea fans. The tubercles are generally not as large or as noticeable as those of the Bargibant's pygmy seahorse.
The Denise's seahorse lives among a wider variety of sea fans than the Bargibant's seahorse and is quite variable in color and tubercle size. For example, one variety of the fish is pink in color and lives amongst the branches of a pink sea fan. Another variety is yellow in color and lives on yellow sea fans, and yet another is red and lives on red sea fans.
The fish is named after Denise Tackett, an underwater photographer. Until her discoveries and reports, the animal was thought to be a juvenile version of the Bargibant's pygmy seahorse.
The Satomi pygmy seahorse (Hippocampus satomiae) is the smallest pygmy seahorse discovered so far. It's about 1.4 cm long. It lives on the coast of the Derawan Islands in Indonesia and is found on coral instead of sea fans.
Other Tiny Seahorses
Not all seahorses with the word "pygmy" in their name belong to the pygmy seahorse group. For example, the Red Sea soft coral pygmy seahorse is small (about 3.5 cm long), but it shares the features of normal-sized seahorses and lacks the unique characteristics of the pygmy ones.
The Japanese pygmy seahorse is a true member of the pygmy seahorse group. It hasn't been described in any detail yet, however. More species probably exist. Finding them is a challenge, but the search is exciting for both biologists and scuba divers. The tiny and beautiful creatures are fascinating to observe.
Hooper, Rowan. "Cute but deadly: The camouflaged world of the pygmy seahorse." New Scientist. https://www.newscientist.com/article/mg22630240-100-cute-but-deadly-the-camouflaged-world-of-the-pygmy-seahorse/ (accessed August 16, 2017).
Cassidy, Joshua. "Pygmy Seahorses: Masters of Camouflage." KQED Science. https://ww2.kqed.org/science/2014/10/21/pygmy-seahorses-masters-of-camouflage/ (accessed August 17, 2017).
"Hippocampus bargibanti." FishBase. http://www.fishbase.ca/summary/53790 (accessed August 16, 2017).
"Denise's Pygmy Seahorse." Wildscreen Arkive. http://www.arkive.org/denises-pygmy-seahorse/hippocampus-denise/ (accessed August 16, 2017).
© 2013 Linda Crampton