67.8 MB (6.9 MB compressed)
4065 x 5834 pixels
34.5 x 49.3 cm ⏐ 13.6 x 19.4 in (300dpi)
DANTE FENOLIO / SCIENCE PHOTO LIBRARY DANTE FENOLIO / SCIENCE PHOTO LIBRARY
Siphonophores (order Siphonophora) are colonial organisms. The individuals in each colony are genetically identical and are attached to one another; they are called zooids. Each individual zooid has a specialization such as locomotion, food gathering, digestion, reproduction, etc. One group of zooids sting and stun prey items - these are the zooids forming tentacles. The tentacles contain stinging nematocysts. Nematocysts are microscopic structures embedded in the tissues of the tentacles. A nematocyst has a coiled and hollow structure within it; the leading side of the hollow structure has a hardened open end with barbs. A hair-like trigger on the outside of the nematocyst triggers the system. When discharged, the tube shoots from the nematocyst, the end punctures the skin of a prey item, the barbs hold the structure in place, and the system delivers venom into another organism. The venom of siphonophores is strong enough to paralyze prey items. It can also impact humans particularly.
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