Some interesting organisms of the ocean

cover image credit: Ryo Minemizu (for more, see


Notes: males are tiny compared to females. In many species of anglerfish, mating occurs through males attaching to and then fusing with females such that their circulatory systems join together. The male provides sperm and is eventually absorbed into the female.

Image: [credit: Dante Fenolio]

Basking shark

Notes: second largest type of shark (after the whale shark), reaches about 7.9 m in length. They feed on plankton by swimming forwards with the mouth open and filtering via gill rakers.

Image: [credit: Wikipedia page]

Blanket octopus

Notes: characterized by transparent flaps connecting the dorsal and dorsolateral tentacles in adult females. In a case of extreme sexual dimorphism, the females grow to around 2 m in size while the males are only about 2.4 cm.

Image: [credit: Steve Hamedl]

Colossal squid

Notes: at around 10 m long, they are shorter than giant squid, but they are much heavier. Colossal squid also has the largest eyes of any organism (around 30-40 cm in diameter).

Image: [credit: NPR]


Notes: depending on the type crinoid adults can either swim freely or be tethered to the sea floor by a stalk. The former are called feather stars and the latter are called sea lillies. Crinoids can also crawl using rootlike structures called cirri as legs. They consume plankton and detritus by filtering through their featherlike arms and then propelling it towards a mouth. They reproduce sexually, releasing sperm and eggs into the water. Fertilized eggs hatch into freely swimming larvae that settle on the sea floor and transition into a stalked juvenile state before eventually breaking away (in the case of feather stars) as adults to swim freely once more.

Image: [credit: Wikipedia page]


Notes: cuttlefish are among the most intelligent invertebrates. They can rapidly change color using their chromatophore cells as a mode of communication and camouflage as well as to warn off predators (called a deimatic display).

Image: [credit: Wikipedia page]

Garden eels

Notes: garden eels are distinguished by their behavior of living in burrows on the sea floor and poking their heads out of the burrows to eat prey and sliding back into the burrows to avoid predators. Colonies of them can resemble grasses, hence their name.

Image: [credit: Insider]

Glaucus atlanticus

Notes: a type of small (up to 3 cm) sea slug that floats upside down using a gas-filled stomach to stay adrift. They feed on Portuguese man o’ war jellyfish and similar organisms. After consuming venomous nematocysts from their prey, they store the stinging cells in sacs (called cnidosacs) located in their own extremities. This concentrates the nematocysts, making the sting of Glaucus atlanticus potentially more potent even than that of the man o’ war jellyfish itself.

Image: [credit: Wikipedia page]

Hawaiian bobtail squid

Notes: enjoys a symbiotic relationship with bioluminescent Aliivibrio fischeri bacteria that inhabit a light organ in the squid’s mantle.

Image: [credit: Wikipedia page]

Japanese spider crab

Notes: has the largest legspan of any arthropod, reaching about 3.7 m across.

Image: [credit: Kids Discover]

Lion’s mane jellyfish’s_mane_jellyfish

Notes: one of the largest types of jellyfish. Though their sizes vary widely, some can reach a bell diameters of more than 2 m and possess tentacles extending for over 30 m in length.

Image: [credit: The Toronto Star]


Notes: a category of animals that exist as flat sheets a few cells thick with a ciliated epithelium on their undersides. They use these cilia to move along the seafloor and most of them reproduce asexually by budding or fragmenting into smaller individuals (though one subtype does also reproduce sexually).

Image: [credit: Wikipedia page]


Notes: a type of marine cyanobacteria which represents perhaps the most abundant photosynthetic organism on Earth.

Image: [credit: Wikipedia page]

Sunflower sea star

Notes: large sea stars which can reach diameters of 1 m. Sunflower sea stars are predatory and consume various prey such as sea urchins, other sea stars, clams, sea cucumbers, and more. They move at a speed of about a meter per minute using thousands of tube feet located on their undersides.

Image: [credit: Wikipedia page]

Vampire squid

Notes: a deep sea cephalopod of about 30 cm length that lives in the ocean’s aphotic zone. Vampire squid (Vampyroteuthis infernalis) have flaps of tissue connecting their tentacles, each of which is lined by fleshy spines. It is covered in photophores that produce disorientating flashes of light to confuse predators. Rather than ink, they can eject a sticky cloud of bioluminescent mucus when highly agitated by predators.

Image: [credit: Wikipedia page]


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