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5 Interesting Sea-dwelling Creatures (With Photos)

The author is a research enthusiast. She studied botany and zoology as major subjects in her bachelor's program.

Read on to learn about 5 fascinating sea-dwelling animals

Read on to learn about 5 fascinating sea-dwelling animals

Sea-dwelling Animals

Sea-dwelling animals have some amazing characteristics and adaptations for their survival in the sea. Their eye-catching shapes and colors are very attractive. There are around one million animal species that live in the ocean. In this article, you will be able to learn about the following five sea-dwelling animals:

  1. Portuguese Man O' War
  2. Radiolaria
  3. Christmas Tree Worm
  4. Sea Anemones
  5. Octopus

1. Portuguese Man O' War (Physalia Physalis)

Physalia physalis, also known as the "bluebottle" or "floating terror," is a marine hydrozoan (from ancient Greek: hydro, "water," and zoan, "animals"). It is the only species in the genus Physalis that uses jet propulsion to move. It exists in the form of colonies, and each colony is divided into smaller units called zooid.

The Man o' war lives on the surface of the ocean. The most conspicuous part of the Man o' war is the pneumatophore, or bladder, which is translucent and 3.5 to 11.8 inches long. It allows the colony to move with the prevailing wind and acts as a floating device.

How to Treat a Bluebottle Sting

  • Avoid rubbing the infected area and wash the tentacles with saltwater.
  • To kill the protein in the venom, dip the stung area in warm water (40 degrees Celsius).
  • Don't treat the sting with vinegar or Adolph's meat. It will make the skin look worse.
  • If the symptoms persist, immediately contact the hospital's helpline.

Interesting Facts

  • The tentacles of the Portuguese Man o’ war can grow as long as 165 feet.
  • It was named after its resemblance to 18th-century Portuguese warships.
  • Each colony acts as a specific sex—male or female.
  • It is a venomous species and delivers a horrible sting that can be fatal.
  • The pear-shaped sac (floating body) has aerodynamic properties, and it is modified by the muscular contraction of the crest.
Colored electron microscopy of Radiolaria

Colored electron microscopy of Radiolaria

2. Radiolaria

Radiolaria are protozoa that are found as zooplankton throughout the global ocean. They are tiny creatures, between 0.1 and 0.2 millimeters in size, containing unique, glass-like exoskeletons. The skeleton is formed by bars or spines and is made up of silica.

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Reproduction takes place by budding and binary fission. They often travel in gelatinous colonies, which can be seen with the naked eye. They feed on bacteria by ingesting them and also through the photosynthesis of symbiotic algae.

A sedimentary rock composed of Radiolarian Skeletons

A sedimentary rock composed of Radiolarian Skeletons

Radiolarian Shells

Radiolarians are covered with elaborate globular shells, usually made of silica and lanced with holes. Acantharian radiolarian shells are made up of strontium sulfate crystals.

Radiolarians come in many shapes and are divided into four groups. When they die, their shells sink to the ocean floor and become part of the ocean sediments. These sedimentary rocks are primarily known as "chert."

Interesting Facts

  • Dead Radiolarians are transformed into a siliceous ooze and cover a large part of the ocean floor.
  • These alien-looking creatures have lived on our planet for approximately 500 million years.
Christmas Tree Worm Close-up

Christmas Tree Worm Close-up

3. Christmas Tree Worm

The Christmas tree worm, or Spirobranchus giganteusr, is a tube-dwelling worm that belongs to the family Serpulidae. The common and scientific names come from their spiral structure. Two crowns protrude from their tube-like bodies.

They are primarily sedentary and lack specialized appendages essential for swimming. The nervous system and circulatory system are well developed in these worms.

A Variety of Colorful Christmas Tree Worms

Interesting Facts

  • The estimated life span of these worms is ten years. But studies have revealed that some worms can live more than 40 years. It is very impressive that a worm with a body length of 10 cm can live for 40 years.
  • In dangerous situations, the worms retract into their tubes, and the tubes become closed with an operculum decorated with antler-shaped spines.
  • The crowns of these worms come in different bright colors, including white, blue, yellow, orange, and red.

4. Sea Anemones

They are marine animals with predatory qualities. The colonies of Sea anemones fight with each other for territory and act like armies. They consist of a single polyp. Breeding occurs by liberating sperm and eggs into the sea.

The majority of Sea anemones are sessile (immobile or lacking mobility). They feed on their prey, including small fish, dislodged mollusks, and carbs.

Breeding in Sea Anemones

They can reproduce sexually or asexually. In sexual reproduction, sperm and eggs are released through the mouth. Fertilization occurs in water, and the fertilized egg develops into a planula larva.

Sexes may be separate in many species, and some species are sequential hermaphrodites. In asexual reproduction, they break in half or into smaller pieces that regenerate into polyps.

Interesting Facts

  • Sea anemones can change their shape dramatically. The tentacles and columns can lengthen, contract, bend, and twist because of the longitudinal, transverse, and diagonal sheets of muscles.
  • They are named after a terrestrial flowering plant, the anemone. They are also known as "flowers of the sea" because of their bright colors and body shape.
  • Many fish live in the tentacles of sea anemones. Of these, the most recognizable is the "clownfish" or "anemone fish." They both (sea anemones and clownfish) have a mutualistic relationship.
  • Some species of sea anemones can change their sex at a later stage of their lives.

5. Octopus

These soft-bodied cephalopods inhibit various ocean regions and have a short life span. The Octopuses are bilaterally symmetrical. They are made up of soft tissues that allow them to squeeze through the tiny gaps.

An ink sac is present under their digestive gland. After shooting out the ink, a thick, dark blob is created, allowing Octopuses to escape from predators. They are predatory animals and feed on other mollusks such as calms and whelks. Open ocean Octopuses feed on prawns, fish, and other cephalopods.

Interesting Facts

  • Octopus blood is blue because of hemocyanin, a copper-rich protein.
  • The Octopus is made up of three hearts and nine brains. Two hearts pump blood to the gills, and the larger one circulates blood to the rest of the body.
  • All the arms contain mini-brains that help them act independently.
  • If one arm of an octopus is lost, it can grow back in a few days.
  • The Octopus is widely considered the most intelligent invertebrate.
  • Its camouflage abilities are outstanding. Its skin can change color and pattern according to its surroundings.
  • Each octopus contains a hidden beak, which is made up of keratin. An octopus uses its beak to inject venom and crush crabs.

Octopus Shooting Ink

Resources and Further Reading

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2021 EK Jadoon

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