Asian swamp eels lack fins and have scaleless, cylindrical bodies with tails that taper at the end. The mouth contains bristle-like teeth and there is a distinctive v-shaped gill on the throat. Overall, the coloration is variations of green, brown, and olive with the ventral side being lighter in coloration. In the U.S., Asian swamp eels are sometimes mistaken for the native American eel (Anguilla rostrata; but the Asian swamp eel is not a true eel and belongs to the fish family Synbranchidae. True eels have small pectoral fins and paired gills on each side of the head.
The kaluga (Huso dauricus) is a large predatory sturgeon found in the Amur River basin. Also known as the river beluga, they are claimed to be the largest freshwater fish in the world, with a maximum size of at least 1,000 kg (2,205 lb) and 5.6 m (18.6 ft). The kaluga is one of the biggest of the sturgeon family. Like the slightly larger beluga, it spends part of its life in salt water. Unlike the beluga, this fish has 5 major rows of dermal scutes, nail-like teeth in its jaws, and feeds on salmon and other fish in the Amur.
Northern Stargazers have an organ on their heads that can create an electric charge (up to 50 volts) that may stun their prey and discourage their predators. This electric organ develops when juvenile Northern Stargazers mature into adults. Marine bony fishes like the Northern Stargazers which possess this ability are described as bioelectrogenetic. Due to their ability to electrocute other fishes and eat them alive by camouflaging themselves before attacking, Northern Stargazers are dubbed as "the meanest fish in creation".
Close kin to seahorses, the leafy sea dragon doesn't live on tropical reefs, but in the cooler rocky reefs off south and western Australia. There, this rare fish, with its leaflike fins and frilly appendages, is perfectly camouflaged among seaweeds and seagrass beds. It can be difficult to spot among the kelp as it slowly sways back and forth with the current. The leafy sea dragon eats small shrimplike animals called mysids that live among the algae and seagrasses. A sea dragon's tubelike mouth works like a drinking straw; a hungry dragon waits until its prey ventures near, then slurps it up. Each day, a single sea dragon may slurp up thousands of mysid shrimp.
One of the smallest members of the genus Synodontis, the upside-down catfish is aptly named for its upside-down swimming posture, which makes it easier for it to feed more effortlessly on the water's surface. It is also known as the blotched upside-down catfish because of its spotted appearance. They are an extremely popular species that have been admired for countless centuries; their images have even been found in ancient Egyptian art. Although they swim faster when upside down, don't be surprised if they swim right-side-up for periods of time. This is particularly true when they want to graze the bottom of the tank for morsels of food. Upon closer examination of the inner structures of this catfish, scientists found that its swim bladder was normal and there was nothing unusual about the balancing organ of the ear, as it resembles that of other catfish.
Blenny is a common name for many types of fish, including several families of percomorph marine, brackish, and some freshwater fish sharing similar morphology and behaviour. Blennies are mostly small, usually marine fishes found from tropical to cold seas. They are slim, ranging in form from moderately elongated, as in some of the tropical species, to very long and eel-like, as in the gunnel and wolffish of northern waters. As a group, however, they are united by such features as a long dorsal fin and pelvic fins, when present, that are placed near the throat and contain one spine and two to four rays.
Both seals and heavy human smokers have high levels of carbon monoxide in their blood streams. While humans acquire it from burning tobacco, researchers think seals' blood carbon monoxide levels are connected to their deep dives. One study found that elephant seals' blood is around 10% carbon monoxide, which researchers attribute to the animals holding their breaths for about 75% of their lives. Exhaling is the only way for an animal to clear carbon monoxide from its body
The egg fish goldfish is a fancy goldfish breed which lacks a dorsal fin and has a pronounced egg-shaped body. They look like ranchu but without the swollen heads of ranchu, and a longer body. Eggfish goldfish are sociable, lively, curious, and friendly with their human caretakers once they get to know them. They do not like to live alone and would prefer the company of other goldfish.
Unlike many species of corals, lobe corals are either male or female, not both. They reproduce via broadcast spawning, where several individuals release their eggs or sperm into the water column at the same time. This method increases the likelihood that eggs become fertilized and reduces the danger from egg predators near the reef surface. Within a few days after the eggs hatch, larvae settle onto the reef surface and begin to form new colonies. Like most shallow-water corals, lobe corals have symbiotic algae living within their cells, providing the corals with excess energy that they make via photosynthesis (the use of sunlight to convert carbon dioxide into food/energy).
The vampire squid is a small cephalopod found throughout temperate and tropical oceans in extreme deep sea conditions. The vampire squid uses its bioluminescent organs and its unique oxygen metabolism to thrive in the parts of the ocean with the lowest concentrations of oxygen. It has two long retractile filaments, located between the first two pairs of arms on its dorsal side, which distinguish it from both octopuses and squids, and places it in its own order, Vampyromorphida, although its closest relatives are octopods. As a phylogenetic relict, it is the only known surviving member of its order