Five Fascinating Facts About Seahorses

1. A Group of Seahorses Is Called A Herd

According to National Geographic, there are about 36 known seahorse species found in a variety of ocean habitats all over the world. They generally prefer warmer, tropical environments and live together in small social groups called herds. Seahorses are monogamous during a breeding season and even “hold hands” with their mate by grasping each other’s tails! Unfortunately, seahorses are vulnerable to extinction due to human activities. Read on to learn more about these unique creatures!

 

2. Seahorses are the slowest swimming fish, but are very effective predators

Seahorses use the small fin on their back to propel themselves. Since this is their only method of locomotion, it does not make them very effective swimmers. In fact, many seahorses die of exhaustion when they are forced to swim for longer periods of time, such as getting caught in a strong current or being displaced by a storm. They would much rather prefer to use their prehensile tails to grip onto plants or coral and stay in place.

However, just because seahorses are not strong swimmers, does not mean they are unable to hunt effectively. A seahorse diet consists of plant-matter, small crustaceans like shrimp, as well as plankton and newborn fish. They eat by sucking food through their long snouts! Seahorses are also great at camouflage (see fact #5!) and often take their prey by surprise as they swim by. Their unique eyes are helpful for catching prey, as they are able to move them independently from one another.

3. Male Seahorses Give Birth and Care for the Young

Well, technically they don’t “give birth.” The female lays her eggs into the male seahorse’s pouch. A male pouch can carry upwards of 1,500 eggs! These eggs then develop for about 6 1/2 weeks and when it is time for them to be born, they pop out of the male pouch and are usually swept away in the ocean current. Infant seahorses have no parental care and generally begin feeding on plant-life as soon as they are hatched. Unfortunately, there is a high mortality rate among young seahorses with less than 1% surviving to adulthood. Because young seahorses do not need parental care, many males can immediately be impregnated again within a matter of hours after hatching a brood of young.

4. Seahorses eat (almost) non-stop

Seahorses do not have stomachs. They need to eat constantly in order to maintain nutrients in their bodies, as food passes through so quickly. An adult seahorse eats about 30 to 50 times per day; which is equivalent to about 3,000 brine shrimp in a day!

 

5. Seahorses Are Incredible at Camouflaging Themselves

Seahorses tend to stay stationary, so they have developed excellent camouflage in order to protect themselves from predators. Even though the seahorse does not have many predators due to a hard-to-penetrate exoskeleton, some type of fish and crabs still find them to be tasty snacks! Seahorses have the ability to change color in order to blend in with plants and coral which allows them to remain safely hidden. This ability is not only done for safety, but both sexes will change their color during courtship as well.

Image Credit: Dennis Polack, FishWise Professional. CC BY-NC-SA.

Five Fascinating Facts About Sea Stars

1.Sea Stars Are Echinoderms, Not Fish

Despite commonly being called starfish, sea stars are not a fish species. They do not have gills, scales, or tails like fish. They also do not have a backbone, so they are considered an invertebrate species. More specifically, they belong to a family called Echinoderms. Being an Echinoderm means that members of these species have five-point radial symmetry (even though some sea stars have different numbers of arms! See fact number 2) Some other species in the Echinoderm family include, sand dollars, sea urchins, and sea cucumbers.  Another interesting characteristic that makes sea stars unique is how they move through the water. They have small tube feet under their body that helps to propel them through the water. These feet also have suction cups which allows the sea star to attach to rocks and prey. There are approximately 2,000 sea star species, all of which exist in ocean habitats.

2.Some Species of Sea Stars Have Different Numbers of Arms  

Although we generally think of a sea star with five pointy arms, this isn’t always the case. In fact, some species of sea star can have anywhere from 10, 20, or even 40 arms, such as the sun star species. On the other end, a species called cushion sea stars appear to look like a blob with no arms. Sea stars have the amazing ability to grow new arms if one is injured. Some can even regenerate an entirely new sea star from a damaged limb. This process of regeneration takes about a year.

Common Sunstar

 Cushion Star. Photo by Joi Ito

3.Sea Stars Do Not Have Blood

Instead of blood, sea stars have a special circulatory system, called a water vascular system, that pumps sea water through their bodies. The sea water delivers nutrients to the sea star, as blood would in mammals.

 

4.Sea Stars Turn Their Stomach(s) Inside-Out to Eat

A sea star’s mouth is located on their underside. They also have two stomachs!  Their prey generally consists of  mussels, clams, snails, and other bivalves. When they find their prey, they wrap their legs around their shell and open it enough to push its first stomach through its mouth and into the opening. Then, they slide their stomach back into their body and the food drops to their second stomach where it is digested. This unique way of eating allows the sea star to eat prey that it would not otherwise be able to fit into its small mouth.

Sea Star Eating. Photo Courtesy of Rosario Beach Marine Laboratory, via Invertebrates of the Salish Sea, CC-BY-NC-SA

5.Some Sea Stars Can Switch Their Gender

Sea stars are gonochorous, which means they are born either male or female. Although many species retain their birth gender their entire lives, many species have the ability to switch their gender. For example, all cushion sea stars are born male and later switch to female for reproductive purposes. All sea star species can reproduce sexually or asexually by regeneration.