Transparent animals — creatures with luminous, clear, almost glass-like skin — can be found in a variety of ecosystems around the globe. These fascinating, verging-on-invisible organisms are the tangible ghosts of the real world. From underwater creatures to butterflies and beetles, here's our list of 11 of the world's most intriguing transparent animals.

1 of 11 Glass Shrimp stevelenzphoto / Getty Images Also known as ghost shrimp, these minuscule crustaceans have nearly translucent shells. In the wild, different species can be found in ponds, lakes, and streams in the eastern U.S. from Florida to New Jersey. The animal is so clear in appearance that it only has color during reproduction, or after it has eaten a colorful meal, which is typically plant-based and, therefore, usually green.

2 of 11 Glass Frogs ABDESIGN / Getty Images There are over 100 species of amphibians of the family Centrolenidae, or glass frogs. So named because the abdominal skin of many is highly transparent, and the frogs' internal organs are on display. Most range in color from light to dark green. Found in the jungles of Central and South America, these animals are mostly arboreal, and they tend to live high in the trees over water.

3 of 11 Glasswing Butterfly Rvasudev / Wikimedia Commons / CC BY-SA 3.0 If it wasn't for the opaque outline around the glasswing butterfly’s transparent wings, the average observer might not see one perched on a leaf or flower. This unusual feature allows the glasswing to remain camouflaged even in flight. Found throughout Central America and parts of South America, adult glasswing butterflies will often migrate great distances. Males of the species are known to lek, or gather in large groups for the purpose of competitive mating displays.

4 of 11 Barreleye Monterey Bay Aquarium Research Institute (MBARI)/ YouTube This unusual fish is found in the deep ocean. Sometimes called a "spook fish," no doubt because of its appearance, the barreleye has a completely transparent forehead. The purpose of the clear head is that its eyes, which are located inside its head, can look straight up as it swims, presumably so that it can detect the silhouettes of available prey. Its eyes can rotate within the socket so that the fish can look in multiple directions, which would be impossible if not for its transparent cranium.

5 of 11 Glass Octopus Joubin / Wikimedia Commons / Public Domain The glass octopus is so unique that it occupies its own family, Vitreledonellidae. Little is known about this marine animal, but it can be found in tropical and subtropical waters around the world. Thanks to its transparent skin, scientists know that its optic lobes have unusually long optic nerve stalks, meaning its sense of sight is acute. Your eyesight would have to be pretty good, too, to spot one of these ghostly creatures.

6 of 11 Crocodile Icefish uwe kils / Wikimedia Commons / CC BY-SA 3.0 These Antarctic predators are unusual because their transparent appearance is due in large part to their nearly invisible blood. They are the only known vertebrates in the world that are white-blooded and do not have hemoglobin, the protein in blood that transports oxygen. They survive without hemoglobin thanks to the subzero temperatures of the ocean where they live, since cold water has a much higher dissolved oxygen content than warmer water. Their unique adaptation lowers their internal body temperature so they can survive in the extreme cold of the Southern Ocean.

7 of 11 Tortoise Shell Beetle Charles Lam / Flickr / CC BY-SA 2.0 This remarkable beetle is not completely transparent, but it does have a carapace that is nearly invisible. The purpose of the transparent outer shell is to fool potential predators, as it reveals markings on its back that act as a warning. Tortoise beetles come in many different varieties, and the design under their clear shells can be distinct and beautiful.

8 of 11 Salps Donato Margapoti / Getty Images Not to be confused with jellyfish, salps are transparent, free-floating tunicates. Their gelatinous bodies swim by contracting and pumping water through internal feeding filters, feasting on algae while they move. They can be found anywhere, but they are probably most common in the Southern Ocean, where they sometimes form enormous transparent swarms. During the day, salps can be seen feeding at the water’s surface, while at night they make their way to the bottom of the ocean to avoid predators.

9 of 11 Transparent Sea Cucumber NOAA Okeanos Explorer / Wikimedia Commons / Public Domain Discovered by researchers with the Census of Marine Life, this sea cucumber is so transparent that its digestive tract is on spectacular display. Found in the Gulf of Mexico at a depth of 2,750 meters (over 9,000 feet), it is one of many unusual finds discovered by the marine census which was conducted over a 10 year period ending in 2010. When encountered, this cucumber was creeping forward on its many tentacles at about two centimeters per minute sweeping detritus-rich sediment into its mouth.

10 of 11 Glass Squid George Sedberry, NOAA-OE / Wikimedia Commons / Public Domain There are about 60 different species of glass squid, so-called because many of them appear completely transparent. This transparency keeps them hidden from predators, which is particularly important in the deep ocean in which they thrive. One species, the cockatoo squid, has other adaptations as well: it can change from transparent to colored when threatened, and is able to expand in size and hold itself motionless when necessary.