Nettle Animals

NETTLE ANIMALS, or Cnidaria, are representatives of the phylum Coelenterata, typical forms of which are the freshwater hydra, jellyfish, and sea anemone. Coelenterates often form colonies, as for example the polyp stage of hydroids and coral polyps. A solitary individual typically represents a two-layered sac consisting of an outer layer (ectoderm) and an inner layer (endoderm), which are separated from each other by a thin supporting lamella or a more or less thick layer of gelatinous tissue (mesoglea) in which connective tissue cells or skeletal structures differentiate. In jellyfish, this layer is very strongly developed, consisting of a water-rich gelatinous substance with a very small number of cells. Highly characteristic of nettle animals are stinging, or nettle, cells (cnidocytes). In their protoplasm, a capsule of various shapes differentiates, inside of which a spirally wound thread is inverted. On the free surface of the cell there is a sensory process (cnidocil). When touched, in response to the irritation experienced, the spiral thread is rapidly ejected outward and pierces the integument of the animal that made contact, pulling the capsule along with it. The thread and capsule contain a poisonous substance that has various effects on humans and animals: small fish are paralyzed by the action of the stinging cells, while humans experience a sensation precisely like a nettle burn (hence the name nettle animals). The greatest effect on human skin is exerted by certain jellyfish and siphonophores. It is possible that symptoms of poisoning are also compounded by phenomena of anaphylaxis. This can explain those cases when people bathing in the sea repeatedly develop a general shock-like reaction upon contact with a jellyfish. Sponge divers develop a peculiar occupational disease due to frequent contact with sea anemones sitting on the sponges that must be torn from the bottom by hand. Initially, itching and severe burning are felt in the affected areas of the skin, followed by the formation of papules. Depending on the degree and duration of the poisoning, the reddened skin darkens, becomes cyanotic, and then turns black. The necrotic skin suppurates. Among the general symptoms of poisoning, fever, chills, headache, and malaise are noted (Zervos). Experiments by E. Pavlovsky and A. Stein on rubbing the tentacles of the Black Sea Actinia equina into human skin showed that due to the action of their stinging cells, acute skin inflammation develops, manifested by edema, vasodilation, and the formation of infiltrates from lymphocytes and polynuclears. From the body of the siphonophore Physalia, Portier and Richet isolated hypnotoxin, which causes death from respiratory paralysis, and from the tentacles of sea anemones—thalassine, which causes skin itching, urticaria, and sneezing upon intravenous injection, and congestin, which kills dogs upon intravenous injection in a dose of 0.0045 g per 1 kg of weight, with phenomena of bloody diarrhea, hyperemia of the digestive tract mucosa, and a comatose state leading to rapid death from respiratory paralysis. Congestin causes phenomena of anaphylaxis; it relates to thalassine in the same way as an antitoxin relates to a toxin. Ackermann and coworkers isolated from Actinia equina a curare-like active substance tetramine [tetramethylammonium hydroxide (CH₃)₄N-OH]. Thus, the toxicity of various nettle animals finds pharmacological justification. The vast majority of nettle animals live in the seas. There have been attempts to use the stinging properties of nettle animals for therapeutic purposes. Jellyfish (Cyanea capillata) are mixed with sea mud for therapeutic procedures in neuralgia and paralysis (Haapsalu).