Marine Invertebrates

The earliest animals to inhabit Earth were invertebrates, animals that lack a backbone, and today these make up more than 98% of all existing species. Without a spine, these animals use different strategies for support such as shells, exoskeleton or hydrostatic pressure.

Marine invertebrates are the invertebrates that live in marine habitats. As on land and in the air, marine invertebrates have a large variety of body plans, and make up most of the macroscopic life in the oceans.

The ornately colored sea anemone (uh-NEM-uh-nee) is named after the equally flashy terrestrial anemone flower. A close relative of coral and jellyfish, anemones are stinging polyps that spend most of their time attached to rocks on the sea bottom or on coral reefs waiting for fish to pass close enough to get ensnared in their venom-filled tentacles.
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Cephalopods are a class of marine animals which include the octopus, cuttlefish and the squid.
The word cephalopod originates from Greek and literally translates to “head-feet”
These animals have a prominent head and a set of arms or tentacles. They are also able to produce and squirt ink. About 800 different species of cephalopods have been identified and range in size from 10mm (idiosepius thailandicus) to 14 meters (colossal squid) which is the largest living invertebrate.
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The Mediterranean fanworm is a large, tube-dwelling worm. It can measure up to 20mm wide and 800mm long. It has a prominent crown of feeding tentacles that extend out of the tube and can be 150mm in diameter. The crown is often banded orange, purple or white. The tubes are leathery, flexible and muddy-looking. They are generally found on hard sub-tidal structures, but can also be buried up to 10cm deep in soft substrates.
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There are around 3000 different species if this kind of sea slug. Not many of these species grow larger than 2 centimetres but what they lack in size they make up in spectacular colour patterns.
Nudibranchs get their name from Greek (nudi) and Latin (branch) words meaning "naked gills". There are two main types of nudibranchs: dorid nudibranchs look fairly smooth, with a tuft of feather-like gills toward the back of the animal that are used to breathe. Aeolid nudibranchs instead breathe with organs called cerata covering their backs.
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They live in all the world's oceans, in fresh water, and on land, are generally covered with a thick exoskeleton, and have a single pair of pincers. They first appeared during the Jurassic Period.
Crabs are mostly active animals with complex behaviour patterns such as communicating by drumming or waving their pincers. Crabs tend to be aggressive toward one another, and males often fight to gain access to females.
Crabs are omnivores, feeding primarily on algae, and taking any other food, including molluscs, worms, other crustaceans, fungi, bacteria, and detritus, depending on their availability and the crab species.
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There are about 950 living species of this spiny marine invertebrate animals.
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Corals are marine invertebrates which typically form compact colonies of many identical individual polyps. A coral "group" is a colony of genetically identical polyps. Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in height. A set of tentacles surround a central mouth opening. In reef bulinding coral, each polyp excretes an exoskeleton near the base. Over many generations, the colony creates a skeleton characteristic of the species which can measure up to several meters in size.
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Although jellyfish can propel themselves with rhythmic motions of their umbrella, they are basically at the mercy of the currents of the sea. Most live for only a few weeks, and the bodies of most range in size from about 2 to 40 cm (1 to 16 inches) in diameter.
Jellyfish consist of almost 99 percent water making them perfectly camouflaged. The body of a jellyfish exhibits radial symmetry and is divided into three main parts: the umbrella, the oral arms (around the mouth) and the stinging tentacles. They have an internal cavity, in which digestion is carried out. This cavity has a single aperture which functions both the mouth and the anus.
Most feed on copepods, fish larvae, and other small animals that they catch in their tentacles, which have stinging cells (nematocysts)
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Lobsters are large bottom dwelling, marine crustaceans most of which are nocturnal. They are mostly scavengers. They have long bodies with muscular tails, and live in crevices or burrows on the sea floor.
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About 1,900 species of starfish occur on the seabed in all the world's oceans, from warm, tropical zones to frigid, polar regions. They are found from the intertidal zone down to abyssal depths, at 6,000 m below the surface.
Starfish are marine invertebrates. They typically have a central disc and usually five arms, though some species have a larger number of arms. Many species are brightly coloured in various shades of red or orange, while others are blue, grey or brown.
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Marine Invertebrates

Anemones

Cephalopods

Fanworm

Nudibranchs

Crabs

Sea Urchins

Coral

Jellyfish

Lobsters

Other Marine Invertebrates

Starfish

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