I. Annelida Polychaeta (cont'd)
Parasites. Symbiosis. Distribution.
The annelids are subject to many parasitic inroads, as by Gregarinoe, Opalinoe, and Nematoids, internally; various vegetable growths, zoophytes, Loxosomoe, and the crustaceans Selius, Selenium, Nereicola, Terebellicola, Sabelliphilus, Chonephilus, and Sabellecheres, externally. Commensalism is likewise not uncommon; thus Polynoe scolopendrina haunts the tubes of Terebella nebulosa, and it also alternates with Harmothoe marphysoe in the tunnels of Marphysa sanguinea; Acholoe astericola frequents the ambulacral rows of Astropecten, Malmgreniacastanea, the peri-oral region of Spatangus purpureus, and Nereilepas fucata associates itself with the hermit-crab in Buccinum; while Alciopina parasitica lives in the interior of Pleurobrachia, and one of the Amphinomidae in the respiratory cavity of Lepas.
The Polychaeta are all marine, and distributed over the whole surface of the globe,-often at very great depths, - as earlyshown by General Sabine, and recently by the Norwegian dredgings, and those of the celebrated "Porcupine" and "Challenger" expeditions. Many species are common to the entire North Sea, and extend to the south as far as Gibraltar, while some northern forms enter the Mediterranean in considerable numbers. The British species are common to the North Sea, and many range to the shores of North America. The size of some of the forms greatly increases in the Arctic Sea. The tropical waters abound with lustrous and splendidly tinted specimens, especially amongst the Amphinomidae. The borers in shell, limestone, coral, and Melobesia, seem cosmopolitan, and the swimming Tomopteris is likewise widely distributed. The forms frequenting the bottom of the sea live in mud or sand, or lurk under stones, in chinks of rocks, shells, and seaweeds. Many specially affect mud or muddy sand, e.g., the Lumbriconereidae, Nephthydidrae, Glyceridae, and the Terebellidae; while some prefer hard or stony ground, e.g., the Polynoidae and Sigalionidae. Between tide-marks they abound in fissures of rocks, under stones in pools, under tangle-roots, and in sand or sandy mud. Many live in captivity several years, but the duration of their existence generally is unknown.
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Annelida - Table of Contents