. The biology of marine animals. Marine animals; Physiology, Comparative. RESPIRATION 147 by modified sucker-like neuropodia and maintains a flow of water through the tube by the co-ordinated beating of three large fans of the middle region (Figs. and ). The water-current serves both for respiration and feeding, and gaseous exchange takes place over the entire integument (161). An echiuroid worm Urechis caupo creates a feeding and respiratory cur- rent through its U-shaped burrow by means of peristaltic contractions of the body wall (Fig. ). Another worm inhabiting a U-shaped burrow
. The biology of marine animals. Marine animals; Physiology, Comparative. RESPIRATION 147 by modified sucker-like neuropodia and maintains a flow of water through the tube by the co-ordinated beating of three large fans of the middle region (Figs. and ). The water-current serves both for respiration and feeding, and gaseous exchange takes place over the entire integument (161). An echiuroid worm Urechis caupo creates a feeding and respiratory cur- rent through its U-shaped burrow by means of peristaltic contractions of the body wall (Fig. ). Another worm inhabiting a U-shaped burrow is the lugworm Arenicola marina found on sandy shores (Fig. ). The tail end of the gallery opens to the surface, while the head shaft is filled with loosened sand which continually settles down as the animal Fig. Sea Urchin Echinocardium cordatum in its Burrow Water is pumped through the burrow from the tail to the head shaft by regular waves of contraction which pass anteriorly along the body (head- ward irrigation, Fig. ). The resultant flow of water provides a respira- tory current and also serves to keep the sand in the head shaft loosened. When the tide recedes the burrow may be left exposed and partly filled with stagnant water deficient in oxygen. Under these conditions the lug- worm sometimes shows another behaviour pattern, in which the hind-end is coiled and thrust above the surface of the water and is then withdrawn with a trapped bubble of air. This is brought into contact with the gills and replenishes the oxygen supply of the animal. Other worms which create respiratory currents through tubes and burrows are nereids, terebellids and sabellids. Some sabellid worms, Sabella and Branchiomma, form firm tubes which are partially buried in the substratum. The oral end of the tube extends above the ground, and. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration
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Keywords: ., bookcentury1900, booksubjectmarineanimals, booksubjectphysiology
