Marvels & Mysteries
In this exhibit you’ll learn that fathers can give birth, animals can produce electricity, and fish can change sexes! Visit Marvels and Mysteries at 2 p.m. on Mondays, Wednesdays, and Fridays to witness the creative and bizarre ways some of these fish eat their food.
There are 47 identified species of seahorses—and scientists continually discover new species—but you’ll see many adult and baby potbelly seahorses in our Marvels and Mysteries gallery. These guys are very slow swimmers; they must beat their dorsal fin 34 times per second just to maintain their position in one place. Luckily they have a prehensile tail, or a tail that can grasp objects, which keeps them wrapped around seaweed, preventing the current from carrying them away.
Another interesting seahorse adaptation is the male brood pouch. Similar to a kangaroo’s pouch, the males have a pouch on their abdomen so that the females can place their eggs into the pouches. The male is then responsible for carrying the eggs until they are ready to hatch, at which point the muscles surrounding the pouch contract and free the young “fry.” The freed fry then fend for themselves, as neither parent provides any further care. In our Marvels and Mysteries gallery, you may see some “pregnant” fathers in the adult tank and many fry in the adjacent tank.
The stars of the feed show on Mondays, Wednesdays, and Fridays at 2 p.m. are the red-bellied piranha, the electric eel, and the Southeast Asian archerfish. These fish have exciting ways of eating and/or hunting their prey.
Piranhas are notorious for their razor sharp teeth; the word “piranha” literally means “tooth fish.” Their exceptionally sharp teeth, which interlock in a scissor-like motion to shred their food. Many species of piranhas are actually vegetarians, and even the most voracious species of piranha, the red-bellied piranha found in the Amazon, is only dangerous to humans when their food source is scarce during a dry season.
The electric eel is another Amazon native. These eel-ectrifying creatures have more than 6,000 specialized cells called electrocytes that store and release voltage. They are the only animal that have this power—literally! They can produce up to 600 volts in a single shock— that’s about as much voltage as 50 car batteries, and is definitely enough to knock a person down or even kill them. Electric eels use their electricity to stun their food and defend themselves from threats. Despite their serpentine form, they are not truly eels and are actually closer relatives to catfish.
Southeast Asian archerfish have a super-soaker for a mouth. Like a squirt gun with remarkable precision, archerfish use their mouths to shoot water at insects above the surface, causing the prey to fall within reach for consumption. If they miss on the first few tries, it’s not a big deal because grooves along the roofs of their mouths enable them to shoot up to seven consecutive streams. Archerfish can target their prey from a distance of 12 feet away, which is pretty impressive considering the fact that their bodies only average seven inches long. Scientists have discovered that archerfish eyes are adapted with sharp vision both above and below the water’s surface.
Not one, but two types of fish in our Marvels and Mysteries gallery (and a few in our Polynesian Reef) start life as one sex and end as another. For example, clownfish are born as males and can later become females. In every clownfish social circle there is one pair of fish that is larger than all the others; one of these large fish is a mature female and the other is a mature male. If something happens to that large female, the large male in the pair will transform into a female and choose a smaller male to replace his former role as the large male of the group.
Similar to clownfish, all ribbon eels are born male. As juveniles they are black and yellow, and they mature into blue and gold colors. These mesmerizing blue and gold ribbon eels are mature males; as they get older they continue to develop body parts, including female reproductive organs. As they develop these body parts they lose their blue color, living out their golden years quite literally as their bodies retain yellowish-gold color as females.
Cartographic, Communicative Currents
Like the electric eel, the black ghost knifefish has electrical adaptations. It does not have electrocytes like the electric eel so it cannot store electricity, but it does use a specialized organ to produce low-frequency electrical currents. Knifefish use this current for navigation and communication. Their ability to sense electricity is called electroreception, and it allows them to detect prey and other knifefish’s electrical signals because they can’t see well in the murky waters they inhabit. In order to find a mate, knifefish produce an electric current that communicates their sex; females produce higher frequency currents than their male counterparts.
Just like the jellies in our Amazing Invertebrates exhibit, the moon jellyfish and the Pacific sea nettle are cnidarians. With few bodies parts and no brain, it’s tempting to think of jellies as “simple” life forms. However, jellyfish have a fairly complex life cycle. All jellies begin as a fertilized egg and develop into a planula larva which in turn grows into a polyp. A polyp consists of a stalk with branches, and it attaches to itself to the seafloor or a coastal reef. Polyps then take one of two reproductive paths. It may reproduce asexually by dividing in half to create a genetically identical bud along itself, creating a longer polyp. The other option is for the polyp to develop into a freely swimming medusa. The medusa is the life stage we are all familiar with—a jelly with a bell and tentacles!
Moon jellies can spend up to 25 years as a polyp alternating between periods of feeding only and releasing ephyra, which are basically baby medusas.12 The Pacific sea nettle, which you’ll also see in Marvels and Mysteries, has a much shorter lifespan; it only lives about six to 12 months. Though their lives are short, their tentacles are very long. Pacific sea nettles’ oral tentacles can grow up to 15 feet long!
Dangerous and Danger-less Dart Frogs!
The most toxic species on Earth is smaller than the palm of an adult’s hand but you wouldn’t want to hold it! The golden poison dart frog is so toxic that you could die from simply holding one. These rainforest dwellers are found on the Pacific Coast of Colombia where indigenous people used to harvest their toxins to put in the tips of blow-darts for hunting (hence the name “dart” frog). Scientists believe their toxicity comes from the insects they eat; thus, our golden dart frogs at the Oklahoma Aquarium are not toxic because we do not feed them those type of insects.
The golden dart frog isn’t the only animal that benefits from its toxicity. Because poisonous frogs are often vibrantly colored, predators learn to associate bright colors with danger and they avoid eating animals colored this way. As a result, harmless animals like the mimic poison dart frog have evolved to look like their poisonous cousins.
Sea horses are constantly eating! They do it out of necessity because they have no teeth and no stomach, and they suck up food through their straw-like mouth, which goes straight to their intestines.
As a way of intimidating other fish, a piranha vibrates the muscles around it’s swim bladder (an air-filled organ used for buoyancy) to produce a grunting sound said to resemble a bark.
Clownfish form a symbiotic (mutually beneficial) relationship with the stinging anemones they live in. The anemone provides a safe home and hiding place for the clownfish without stinging it. Clownfish have a thick layer of mucus to prevent stings and the longer they live in the anemone the thicker the layer gets as it mixes with the anemone’s own mucus. Clownfish return the favor by scaring away predators, feeding the anemone with their waste, and cleaning the anemone.
Where’s the Octopus?
Our giant Pacific octopus is now at the Downtown Aquarium in Denver, Colorado, while we build a new octopus home, the Secret World of the Octopus!
Written by Alyssa Rodriguez, February 2019.