(25-01-10) We know that many fishes and cnidarians (jellyfish and actiniae) are dangerous for human health if we touch them, but many divers unknow the danger of touching some very common species of molluscs, porifera and echinoderm.
Most of the animals living in our seas and oceans are, in theory, harmless for human being. However, they have their methods of self-defense, and can be very painful and even lethal for us.
 From the smallest and lethal jellyfish such as the sea wasp (Chironex flecheri) or the portuguese man o' war (Physalia physalis), to the fearsome great white shark (Carcharodon carcharias) or the beautiful red lionfish (Pterois volitans), are known species by general public because of their danger and greed, which they only show when man invades their habitat and contacts with them directly.
But the sea world is home for many more unhealthy species in case we touch them. Both diving and enjoying a bath in a sandy beach, we can find beautiful animals, apparently harmless but potentially dangerous because of their bites, bones, filaments and, in general, poisons that can cause much more than pain.
 Within the group of molluscs there is a family of lovely sea snails called cone snails (Conidae) of which about 700 species have been catalogued. We can find many of them empty, usually in surf zones of beaches, when the tide goes out. But there are about twenty species that are dangerous when they are alive, because they live buried in the sand and can inadvertently stepped on or touched when digging.
Cone snails can be divided in three big groups according to their eating habits: some species feed on warms in the beach (vermivora), others on molluscs (some times on their own partners) and others finally on fishes (piscivorous).
ONLY TWO SPECIES ARE REALLY DANGEROUS
 Bites of vermivora species can de painful, but are not a real danger for human being excepting those big such as como Conus leopardus or Conus quercinus. In fact, of the species of cones in the world, only twenty are dangerous. They are those which eat molluscs or fishes, whose poison is strong enough to immediately immobilize preys of considerable size and often to be able to defend them effectively.
 The most poisonous species are undoubtedly Conus geographus, Conus tulipa and Conus striatus, all piscovorous. Among the dangerous cones for human being we can mention Conus pennaceus, Conus textile, Conus aulicus, Conus magus and even Conus marmoreus.
These carnivores use a real poison dart to capture their preys. When they find a prey and it is located close enough, a kind of harpoon (jagged dart) is fired through the tube and plunges into the victim. The poison contains a mixture of toxins (conotoxins, one of which has an effect similar to the one of the curare) that affect the nerve centres, producing a total or partial paralysis of the prey almost immediately.
The harpoon is attached to a filament (like a fishing line) that allows the predator to pull its immobilized to its long snout for eating it. A cone has several dozens of poisonous stings so the stings can be multiple.
Like in other predators, it seems that there is no relationship between the size of the specimen and its danger. Rather, it seems that the severity of the bites is more related to contact time, since the amount of poison available after a bite is almost the maximum.
WE HAVE TO ACT, BUT AT THE SAME TIME SEEK MEDICAL ASSISTANCE
 In case of bite, the affected feels heavy pain at the beginning, followed by a progressive paralysis that can lead to death in 2 to 6 hours. The first thing to do is to use a suction device (Aspivenin). Over all, it is important to keep calm, immobilize the affected area as possible and make a tourniquet to slow the spread of the poison in the blood and, during this process seeking for medical assistance.
Try also to keep the cone to show it to the doctors. There is no antidote against their poisonous, exactly against the molecules responsible for its toxicity, and the treatment therefore is symptomatic. For pain it is recommended to use an injection of analgesic. In all the cases, even if the pain is not strong and the bite does not look dangerous, we always must seek medical assistance.
 Sea sponges are the most simply animals existing. They live mostly in the sea, on the rocks or the floor, and they have many holes called incurrent pores, and a hole that connects the body cavity with the exterior and serves as mouth and anus and its name is osculum. Sponges hold thanks to a skeleton composed of spicules.
They feed by filtering. To do so, they have specialised cells called choanocytes that create a water stream that enters it by the pores and exit through an opening on the top called osculum. Reproduction can be sexual, it is by gamotes, and asexual, from a fragment of its own body.
According to their many forms, sponges can be tubular, flat, fan, lobular, etc. Their bodies are porous and of very different colours. Some of them can even be toxic, like the Fibulia nolitangere (poisonous bun or do-not-touch-me), the Tedania ignis (fire sponge) and the Microciona prolifera (red moss sponge).
 There are sponges and fire corals that have a structure quite similar to a crossbow loaded with toxins poison darts for hunting. When they are shot, by contact, cause itching, burning and redness of the area. Protect oneself with a suit and gloves and avoid the contact is enough not to suffer from the effect of the dreaded nematocysts.
 Some sponges in the tropics can also give surprises like this, not because they are equipped with this type of cells, but because they accumulate substances such as halitoxina and okadaic acid. In contact they cause burning and pain. So, if we do not known to discriminate between harmless sponges and a fire sponge, one must follow the rule number one: do not touch!
THE SMALLEST OCTOPUS IS THE DEADLIEST IN THE WORLD
Of course, there is a sea animal to which we must not approach to see it better because it is very small, and obviously not to touch it. We are talking about the blue-ringed octopus (Hapalochlaena maculosa), the smallest in the world and also the deadliest. We also must be far from its relatives Hapalochlaena lunulata (greater blue-ringed octopus) and Hapalochlaena fasciata (blue-lined octopus).
 Bites of octopuses are usually slight, a simple wound. They usually do not become more serious. In contrast, the blue octopus bite is different. Maybe you do not feel its bite. The first symptom is a small whitish area that immediately becomes inflamed and can quickly lose blood in abundance.
Then, they appear the first symptoms of paralysis, difficulty breathing and speaking, vision problems, vomiting, etc. until suffering from a complete paralysis. Be careful with these paralysis, the person can not move, but he or she is aware at all times.
As among corals and sponges, there are also fire urchins, which painfully puncture with their quills like the rest of urchins, and also have the ability to inoculate poison. Just touching them with bare skin pain can be excruciating.
Also, among the echinoderms, the great crown-of-thorns starfish, common in the Indo-Pacific, is the only venomous starfish. Its skin has toxins that cause pain and irritation.
There are two known poisonous starfish: Acanthaser planci (crown-of-thorns starfish) and Acanthaser Elisi of Indo-Pacific and East regions respectively. The outer surface of its body is covered with large, sharp spines that are soft calcareous structures that break when penetrating, so they are very difficult to extract from the wounds. These starfishes are so large that it is almost impossible not to avoid them when one pays some attention.
Text: Guadalupe Romero
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