Irukandji jellyfish are small and extremely venomous jellyfish that inhabit marine waters of Australia. But according to a National Geographic documentary on jellyfish the species has been found in waters as far north as the British Isles, Japan, and the Floridacoast of the United States. They are able to fire their stingers into their victim, causing symptoms collectively known as Irukandji syndrome. The Irukandji syndrome is produced by a small amount of venom and induces excruciating muscle cramps in the arms and legs, severe pain in the back and kidneys, a burning sensation of the skin and face, headaches, nausea, restlessness, sweating, vomiting, an increase in heart rate and blood pressure, and psychological phenomena such as the feeling of impending doom. The symptoms last from hours to weeks, and victims usually require hospitalisation. The size of the Irukandji jellyfish is roughly a cubic centimetre (1 cm3). There are 4 known species of Irukandji. photo credits: wikipedia, deadlylist, life-sea
Egyptian Sea Star (Gomophia egyptiaca)
…a species of Ophidiasterid sea star which despite its common name is widely distributed throughout the Indo-Pacific (including the Red Sea). Like other sea stars Gomophia egyptiaca is omnivisrous feeding a range of sessile/slow moving organisms ranging from snails and sponges to algae.
Image: Alexander Vasenin
Sea cucumbers extract oxygen from water through a pair of “respiratory trees” that branch off the cloaca just inside the anus. Therefore, they “breathe” by drawing water in through the anus and then expelling it. The trees consist of a series of narrow tubules branching from a common duct, and lie on either side of the digestive tract.
Some species of coral-reef sea cucumbers within the order Aspidochirotida can defend themselves by expelling their sticky cuvierian tubules (enlargements of the respiratory tree that float freely in the body cavity) to entangle potential predators. When startled, these cucumbers may expel some of them through a tear in the wall of the cloaca in a process known as evisceration. The release of these tubules can also be accompanied by the discharge of a toxic chemical known as holothurin, which has similar properties to soap. This chemical can kill animals in the vicinity and is one more way in which these sedentary animals can defend themselves.