The ocean is filled with animals in a vast array of shapes and sizes. Although most people are familiar with the large size of whales and sharks, they might be surprised at just how large a sea star or jellyfish can get. Here are a few of the ocean’s largest animals.
The Blue Whale is the Largest Living Animal
The Blue Whale (Balaenoptera musculus) is the largest mammal and possible the largest animal to ever live on this planet, according to the American Cetacean Society’s webpage “Blue Whale”. The largest recorded was 33 meters (108 feet) in length. Although these giant creatures can weigh up to 136,000 kilograms (150 tons) they eat only tiny shrimp-like creatures called krill. These mighty beasts can be found throughout all the ocean’s waters from the Earth’s poles to the equator.
The Largest Fish in the Ocean
The Whale Shark (Rhincodon typus) is the biggest fish in the sea and while it is not a whale it is classified as a shark. Whale sharks can be found around the world and according to the National Geographic’s “Whale Shark Profile” the largest measured was 12.2 meters (40 feet) long; however they are thought to grow bigger. Although huge, the whale shark eats mostly plankton and is a filter feeder.
The Biggest Marine Creatures with Tentacles
The largest Colossal Squid (Mesonychoteuthis hamiltoni) measured was 18 meters (59 feet) in length and weighed 900 kilograms (1 ton) according to the National Geographic’s 2009 “Giant Squid Profile”. These creatures have the largest eyes in the animal kingdom at 25 centimeters (11 inches) across. Although the Colossal Squid is the largest invertebrate on Earth, little is known of them.
The Lion’s Mane Jellyfish (Cyanea capillata) is commonly found off the coast of England according to the Marine Life Information Network. It can grow up to 200 centimeters (6.5 feet) and has a deadly sting.
The Largest Ocean Animals with Shells
The Japanese Spider Crab (Macrocheira kaempferi) at 4 meters (13 feet) from claw to claw is likely the largest arthropod in the world says the Britannica Online Enclopaedia in “Giant Crab”. This crab can weigh up to 40 pounds and lives in the Pacific Ocean off of Japan at depths of 50-300 meters (150-1000 feet).
The Giant Clam (Tridacna gigas) is the fitting name for the largest shelled mollusk as the National Geographic reports in its 2009 “Giant Clam Profile”. At 1.2 meters (4 feet) in length this large ocean creature can weigh up to 227 kilograms (500 pounds). This giant found around Southeast Asia and the Indian Ocean can live over 100 years when left alone. Unfortunately, due to over-harvesting by humans for food and shells this amazing marine animal is considered a vulnerable species by many groups.
The Ocean’s Giant Sea Stars
The title of longest and heaviest sea stars belong to two different species. The sea star, Thromidia catalai, can weigh up to 6 kilograms (13 pounds) and lives off the coast of New Caladonia according to Daniel Gilpin in the book Starfish, Urchins & Other Echinoderms, page 41. In the Gulf of New Mexico lives Midgardia xandaros which has long but slender arms extending 1.38 meters (4.5 feet) across.
The Ocean Contains Many Large Creatures
The ocean’s creatures can grow surprisingly large. However, size is not the only interesting aspect of marine animals. Creatures of the sea display numerous interesting features including fish that can change gender and species living in dependent relationships with each other. Marine creatures are surely interesting to study given the variety of their size, shape, and lifestyles.
The Different Layers of the Ocean
As any marine biology student knows, the ocean is not one homogenous block of water. Covering over 70% of the Earth’s surface, the ocean spans from the balmy equator to the frigid poles. The ocean is also very deep with temperatures getting colder and water pressure increasing at greater depths. These changes mark different layers in the sea and at different layers animals require certain adaptations to survive.
The Sunlight Zone is the Top Ocean Layer
NOAA describes the various layers of the ocean in its National Weather Service article “Layers of the Ocean”. The sea surface down to 200 meters (660 feet) is known as the Epipelagic Zone or the Sunlight Zone. This zone varies greatly from the tropics to the poles. Tropical coral reefs are one of the most biodiverse ecosystems on the planet, home to schools of tropical fish, shrimps, seastars, and more.
The Twilight Zone is in the Ocean
After the Sunlight Zone marine biology students learn about the Mesopelagic Zone, or the Twilight Zone, which occurs from 200 meters to 1000 meters. NOAA writes that sunlight in this ocean layer is faint and temperature fluctuates greatly. The Twilight Zone is home to the thermocline, an area where temperature changes quickly with depth. Paddy Ryan writes about many of this layer’s creatures in Te Ara’s “Deep Sea Creatures – The Mesopelagic Zone”. Ryan notes that most of the food in this layer comes from the Epipelagic Zone and that fish will travel upwards at night to eat it. These include lanternfish (Myctophids) and bristlemouths (Gonostomatids). Also found in this layer are the blobfish (Psychrolutes species) and the prickly shark (Oxynotus bruniensis).
Marine Creatures in the Midnight Zone
NOAA writes that the Bathypelagic Zone is also called the Midnight Zone as sunlight never reaches its depths of 1,000-4,000 meters (3,300-13,100 feet). The only light found is from bioluminescent animals. Temperatures are usually a constant 4 °C (39 °F) and at the deepest edge of the Midnight Zone pressure is at 5850 pounds per square inch. Sperm whales will dive to these depths to find food. The Midnight Zone is also home to many animals including angler fish, eels with giant jaws, and tube worms of hydrothermal vents.
Finding Marine Life in the Abyss
The Abyssopelagic Zone, or simply the Abyss, occurs from 4,000 meters down to 6,000 meters (13,100 feet to 19,700 feet). Even at these crushing depths and frigid temperatures marine biologists have found fish. As Rebecca Morelle writes for the October 7, 2008 BBC article “‘Deepest ever’ living fish filmed” a school of 30 cm (12 in) Pseudoliparis amblystomopsis was found off of Japan at a depth of 7.7 km (4.8 mi). The fish is also sometimes called a liparid.
The Deepest Part of the Ocean
NOAA continues that the Hadalpelagic Zone is the deepest layer of the ocean, extending from 6,000 meters (19,700 feet) to a depth of 10,911 meters (35,797 feet) in the Mariana Trench off of Japan. At such depths the temperature is constantly just above freezing and the weight of water is greater than 8 tons per square inch. NOAA compares this to the weight of 48 Boeing 747 jets. Yet life lives here too reports NOAA; in 2005 a type of plankton called foraminifera was discovered in a trench southwest of Guam. This recent discovery just goes to show that marine biologists still have much to learn about the ocean and its inhabitants.