This group includes some of the most colourful creatures on earth. In the course of their evolution, nudibranchs have lost their shell while developing alternative defence mechanisms. Some species evolved an external anatomy with textures and colours that mimicked surrounding sessile invertebrate animals (often their prey sponges or soft corals) to avoid predators. Other nudibranchs, as seen especially well on chromodorids, have an intensely bright and contrasting colour pattern that makes them especially conspicuous in their surroundings.
Natural defenses of the pufferfish
The puffer's unique and distinctive natural defenses help compensate for its slow locomotion. It moves by combining pectoral,dorsal,anal and caudal fins. This makes it highly maneuverable, but very slow, and therefore a comparatively easy predation target. Its tail fin is mainly used as a rudder, but it can be used for a sudden evasive burst of speed that shows none of the care and precision of its usual movements. The puffer's excellent eyesight, combined with this speed burst, is the first and most important defense against predators.
Its backup defense mechanism, used if successfully pursued, is to fill its extremely elastic stomach with water (or air when outside the water) until it is much larger and almost spherical in shape. Even if they are not visible when the puffer is not inflated, all puffers have pointed spines, so a hungry predator may suddenly find itself facing an unpalatable, pointy ball rather than a slow, tasty fish. Predators which do not heed this warning (or which are "lucky" enough to catch the puffer suddenly, before or during inflation) may die from choking, and predators that do manage to swallow the puffer may find their stomachs full of tetrodotoxin, making puffers an unpleasant, possibly lethal, choice of prey. This neurotoxin is found primarily in the ovaries and liver, although smaller amounts exist in the intestines and skin, as well as trace amounts in muscle. It does not always have a lethal effect on large predators, such as sharks, but it can kill humans.
A diver stumbles across a whale shark trapped in a commercial fishing line. Sensing the diver is there to help, the goliath lies still while the rope is cut.
Jelly fish are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles. The bell can pulsate for locomotion, while stinging tentacles can be used to capture prey.
Jellyfish are found in every ocean, from the surface to the deep sea. Scyphozoans are exclusively marine, but some hydfrozoans live in freshwater. Large, often colorful, jellyfish are common in coastal zones worldwide. Jellyfish have roamed the seas for at least 500 million years, and possibly 700 million years or more, making them the oldest multi-organ animal.
Check out this vdo of an octopus fighting of an moray eel
Hunting techniques of the banded sea krait
Banded sea kraits are often seen in large numbers in the company of hunting parties of giant travelly (Caranx ignobilis) and goatfish Their cooperative hunting technique is similar to that of the moray eel, with the kraits flushing out prey from narrow crevices and holes. Kraits need to drink fresh water and regularly come onto land for that purpose.
While probing crevices with their head and thus unable to observe approaching predators, banded sea kraits can fool their potential enemies to believe that their tail is the head. This is based on both colouration and tail movements, such that the lateral aspect of tail corresponds to the dorsal view of the head.
Colorful nudibranche at the Similan islands
Nudibranchs occur in seas worldwide, including both the tropics and Antarctica.
Nudibranchs live at virtually all depths of salt water, from the intertidal zone to depths of well over 700 m (2,300 ft). The greatest diversity of nudibranchs is seen in warm, shallow reefs, although a new nudibranch species was discovered at a depth near 2,500 m (8,200 ft).
Anemone fish at the Similan islands
Anemonefish and sea anemones have a symbiotic , mutualistic relationship, each providing a number of benefits to the other. The individual species are generally highly host specific, and especially the genera Heteractis and Stichodactyla, and the species Entacmaea quadricolor are frequent anemonefish partners. The sea anemone protects the anemonefish from predators, as well as providing food through the scraps left from the anemone's meals and occasional dead anemone tentacles. In return, the anemonefish defends the anemone from its predators, and parasites. The anemone also picks up nutrients from the anemonefish's excrement, and functions as a safe nest site.The nitrogen excreted from anemonefish increases the amount of algae incorporated into the tissue of their hosts, which aids the anemone in tissue growth and regeneration. It has been theorized that the anemonefish use their bright coloring to lure small fish to the anemone, and that the activity of the anemonefish results in greater water circulation around the sea anemone. Studies on anemonefish have found that anemonefish alter the flow of water around sea anemone tentacles by certain behaviours and movements such as "wedging" and "switching." Aeration of the host anemone tentacles allows for benefits to the metabolism of both partners, mainly by increasing anemone body size and both anemonefish and anemone respiration.
Corals and other "slow life" do move, though we often think of them as very nearly static. In order to see their movement, you need to change your perspective -- slow way down, photograph in time lapse, and then carefully assemble the result so that humans can understand what that motion looks like from the perspective of such a slow creature. Photographer Daniel Stoupin has done just that with his short film Slow life, three and a half minutes of time lapse that took nine months to create.