Fish and sea creatures

The pioneering studies are associated with Humboldt-era naturalists, especially those who documented the South American electric eel in the late 18th and early 19th centuries. The eel’s shocks are generated by specialized electric organs made of modified muscle cells.

The first scientific description of the living coelacanth is credited to J. L. B. Smith, who identified the famous East African specimen in 1938. The fish was thought extinct for about 66 million years before that discovery.

Early comparative anatomy work by Georges Cuvier helped establish that sharks have skeletons made of cartilage, not bone. That feature is one reason sharks are classified with rays and skates in the cartilaginous fish group.

The classic evidence is associated with Franz and Eleanor Persaud and later researchers such as Kenneth Lohmann and Cathy Lohmann. Their experiments in the late 20th century helped demonstrate magnetic orientation in sea turtles and fish.

Lanternfish were described by 19th-century ichthyologists working on deep-sea life, with many species later named in modern oceanographic surveys. They are now famous for being one of the most abundant fish groups in the ocean.

Naturalists studying remoras in the 18th and 19th centuries described the dorsal fin transformed into a suction disc. That adaptation lets remoras hitchhike on sharks, turtles and other large animals.

The relationship was documented by marine biologists in the 20th century, building on earlier natural-history observations. Clownfish are protected by mucus that helps them avoid the anemone’s stinging cells.

The giant squid was formally described in the 19th century by naturalists working from specimens and stranded remains. The animal became one of the ocean’s most famous deep-sea mysteries.

Modern studies by marine biologists in the 20th century showed that octopuses can rapidly alter skin color and surface texture. The underlying control comes from specialized skin cells and nerve control.

Deep-sea naturalists and oceanographers in the 19th and 20th centuries documented the anglerfish’s glowing lure. The lure is a modified dorsal spine tipped with light-producing symbiotic bacteria in some species.

Naturalists and comparative anatomists in the 18th and 19th centuries documented shark tooth replacement. Sharks can lose and replace teeth continuously throughout life.

Marine biologists in the 20th century established that male seahorses carry the developing embryos in a brood pouch. This is one of the most unusual reproductive systems in fish.

Ancient and early modern naturalists noted electric rays, but their electric nature was scientifically explained much later by comparative anatomists. Electric rays can generate strong shocks used in defense and prey capture.

Early naturalists and anatomists described the nautilus shell as chambered and used for flotation. The animal adjusts gas and fluid in those chambers to control depth.

Marine biologists studying coral reefs in the 20th century described cleaner wrasse stations where larger fish are cleaned of parasites. The behavior is a well-known example of mutualism.

Lungfish were studied by 19th-century naturalists who recognized their unusual lungs and survival in low-oxygen water. They became important in discussions of vertebrate evolution.

The animal nature of corals was established by 18th- and 19th-century naturalists and zoologists. They showed that corals are colonies of animals that secrete calcium carbonate skeletons.

Paleontologists such as Philip Gingerich and others established the fossil transition from land mammals to whales in the late 20th century. The evidence came from fossils like Pakicetus and Ambulocetus.

Marine biologists in the 20th century documented the giant Pacific octopus’s problem-solving ability and complex behavior. It became one of the best-known examples of intelligence in an invertebrate.

Modern marine biology in the 20th century revealed that jellyfish have nerve nets, coordinated movement and complex life cycles. They are much more biologically sophisticated than their simple appearance suggests.

Oceanographers in the 20th century showed that plankton form the base of marine food chains. Their studies connected microscopic life to fish populations and marine ecosystems.

The torpedo ray’s electric organ was described by early naturalists and later anatomists studying bioelectricity. It can deliver shocks for defense and prey capture.

Marine biologists studying stomatopods in the late 20th century measured the mantis shrimp’s explosive strike. The punch can accelerate so fast it can stun prey and even create cavitation bubbles.

Regeneration in sea stars was documented by naturalists and later experimental biologists over the 19th and 20th centuries. Some species can regrow arms, and in certain cases parts of the body can regenerate extensively.