Killer cones
by Bruno Mathé
Original source (in French): http://perso.wanadoo.fr/zonatus/Cones_tueurs.htm Edited and translated by Bruce Livett [using Google Translate (BETA) & Gist-In-Time]
One often speaks about them without knowing them. The poisonous cones however represent a fascinating group. Let us re-examine these frightening molluscs, with a magnifying glass ... and with gloved hands.
Conus aulicus attacking scutus inguis, Mauritius
Among some 50 000 species of shells listed in the world, the family Conus (Cone Shells) is without doubt one of the most attractive and most interesting. The occasional collector is attracted to them by their variety of geometrical patterns and delicate colours. The experienced collectors seek the rarest species like Conus pergrandis or Conus gauguini - in addition to Conus gloriamaris, which though relatively common, remains one of the most sought after species. As for the malacologists, they find another reason to be attracted to cone shells: the presence in most cones of a poisonous venom apparatus.
Poison dart
In the complex classification of Molluscs, the cones belong to the class Gastropoda, subclass Posobranchia, order Neogastropoda and to the super-family Conacea. This group includes Turridae (turrides), Terebridae (terebrate) and Conidae, the nearest relatives and which count among the most highly evolved species of all shells. To capture their prey, these carnivores use a poison dart. When the prey is located and is sufficiently close, a hollow, barbed poison dart (a kind of harpoon - or 'radula' as it is known) which is attached to the end of the proboscis, is impaled into the hapless victim. The venom contains a cocktail of toxins, called conotoxins (one is similar in its actions to curare), which target the nerve centres bringing about a total or partial paralysis of the prey. The harpoon is tethered by a fine thread (like a fishing line) and enables the predator to 'reel in' the immobilised prey into its now dilated mouth to be consumed.
20 dangerous species
While térèbres and turrides are relatively harmless to humans, it is not so for the cones. The latter can be classified according to three large groups according to their food preferences: certain species (vermivores) find nourishment in worms which they find in the sand, others (molluscivores) eat molluscs (sometimes their own Conus species), still others (piscivores) eat fish. Of the 500 to 600 species of cones listed in the world, only about twenty are dangerous to humans - mainly molluscivores and piscivores. Their venom has to be powerful enough to immobilise prey of significant size and capable of being effectively delivered.
2 to 6 hours
The most poisonous species are without question Conus geographus, Conus tulipa and Conus striatus. All three are piscivores. Among the other cones, those dangerous to humans include Conus pennaceus, Conus textile, Conus aulicus, Conus magus and Conus marmoreus. The stings of the vermivorous species can be painful but do not present a real danger to the man, except perhaps for those of larger size like Conus leopardus or Conus quercinus. As for the other predatory cones, there does not appear to be a relationship between the size of the species and the potency of its venom. On the other hand it is likely that the seriousness of sting is related to the duration of exposure to the venom. In this connection, it is known that the cone has several tens of poisonous darts (in a radula sack containing a 'quiver of darts'): the stings can thus be multiple. The careless collector could expect to feel an initial sharp pain, followed by a progressive paralysis that may result in death within 2 to 6 hours
Precautions
When searching for shells in tropical waters, in particular for cone shells, it is prudent to heed certain rules of caution. Please, never search the sand or under stones with bare hands, but use gloves to protect yourself, to a certain extent, from coming in contact with dangerous marine creatures - eg. sea urchins, stinging coral, stone fish, etc. When you find a cone, seize by the base of the shell (with the broadest dimensions) and keep a watchful eye on the cone. Certain species, notably Conus striatus, can show a surprising fighting spirit. Be aware that the poison harpoon can pierce fine layers of fabrics or plastic and has been known to penetrate the skin through the thickness of a wetsuit. Whatever the species of cone collected, and even if its identity is not in any doubt, take precautions all the same. It is often difficult to distinguish a cone that looks inoffensive from a poisonous one, particularly when its shell is encrusted by limestone; in addition, certain species are regarded as considered as harmless due to the lack of data about to their behaviour.
No antidote
In the event of a sting, some advocate using an aspirating device such as the Aspivenin type (but you would need to carry one with you). [ASPIVENIN® is a syringe style mini-pump that sucks out venom in the case of toxic bites and stings]. Above all, remain calm. The most important thing is to immobilise the part stung (to slow down the dispersion of venom in the blood) and to apply a pressure bandage. Alert others and seek help. Preserve the cone that has stung you to show it to the doctors. There is no antidote to the venom of the cones, or to be more precise, to the molecules responsible for its toxicity, the conotoxins. The treatment is thus symptomatic. To fight the pain of the sting, an injection of analgesic is recommended (eg. Solumedrol, a "glucocorticoïd"). In all the cases, even if the pain is not strong and the sting seems harmless, seek medical help.
Hidden in sand
Having said all that above, there is no need for paranoia. In spite of the extremely poisonous nature of certain cones, accidents remain very limited - as far as one can judge from the cases reported. Some dozen mortal stings, at most, are listed in the medical literature. Certainly, the dangerous species are not rare, as for example the common Conus textile. But their habitat and behaviour limits the possibilities of accidental encounters. In the daytime, one finds them buried in sand or hidden under stones. These animals are nocturnal, and go out of their shelters only during the night to feed. One never sees Conus textile inadvertently by walking in the shallows above it. Only those that seek carefully and deliberately find these cones.
Surprises
The area of distribution of poisonous cones extends throughout the Indo-Pacific region. The only species found in the Mediterranean Sea is Conus ventricosus, and is known by as many names as there are regions where one collects it. It is totally harmless. As for the Caribbean region, there is no record of poisoning of humans by any of the cones found there. However, caution is still required as new species are being discovered every year. Cones, not satisfied to offer us just attractive and tempting shells, may still reserve a few unpleasant surprises for the unwary.
(c) Zonatus.com. This article first appeared in the January / February, '95 edition of the monthly magazine Apnéa.
To know more about venomous cone shells : for a very complete site on poisonous cones, in particular on current research being carried out on possible medical applications of conotoxins, see :
Cone Shell and Conotoxins.
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