Tube feet

G( = mass velocity in tube, lb/ (sec) (fE of cross-section) FB.(g = Friction loss from part B to part C in tubes, feet liquid... 

The phylum Echinodermata comprises about 7000 living species [177]. Echinoderm means spiny-skinned and these organisms are characterised by the tube feet, which they use to move about. These have suction discs on the ends, which operate by an internal bulb pumping water in and out of the foot, causing expansion and contraction. The phylum is sub-divided into five classes the asteroids (sea stars), the holothurians (sea cucumbers), the crinoids (sea lilies), the echinoids (sea urchins) and the ophiuroids (brittle stars) [178]. As stated in the introduction to this review, sulfated sterols and saponins, which comprise the majority of echinoderm metabolites containing sulfur, are not included here. 

TubE-FEET The small tentacle-like, flexible, tubular processes of starfishes. 

Limpets (Acmaea sp.) raise their shell, rock or wiggle, and then move away at their highest possible speed (1 cm in 5 s) when a tube foot of a starfish contacts them. If the tube feet have succeeded in a tight grip, the limpet twists 90-180° around its vertical axis several times, breaking the grip by the starfish, and then moves away. The abalone, Haliotis sp., shows this response particularly well (Bullock 1953). 

Extracts of tube feet or stomach juice from a starfish release these responses. Extract from a small starfish (Leptasterias sp., 2-3 cm from arm tip to arm tip) triggers escape responses in abalone which is 10 cm or longer ... 

Condensers.—From a thermal standpoint, condensers may be classified as mixing (horizontal independent jet, injector or barometric) and non-mixing (surface) types.. The equations above given for feed-water heaters will apply as an error on the safe side, x may be taken as 1.0. The value of ti is determined by the available supply of cooling water in this latitude under summer conditions, it is rarely below 70°. That of to will be in surface condensers 6 to 10° below tj and that of t2 the same amount below U- The value of to determines the best possible vacuum. Orrok gives k = SfiOr VF, for clean copper tubes, where V = water velocity in tubes, feet per second, r = ratio of partial pressure of steam to total pressure in the condenser. If condensers and vacuum pumps are tight, r == 0.95. 

Fig. 4.5 The tube feet of a starfish are visible on its underside. (Courtesy of Dr. James E McVey, NOAA Sea Grant Program)...

Sand dollars are so flat that at first look they do not resemble their echinoderm relatives. The plates of their skeletons are fused and fixed, and the external surfaces are covered with tiny spines that look like fuzz or a short coat of hair. Sand dollars use their spines to burrow into sand. Once buried, the spines collect small food particles that fall among the spines and transfer them to the mouth. As shown in the upper color insert on page C-7, the common sand dollar (Echinarachnius parma) may be brown with purple or red tints. A five-petal pattern on the sand dollar s dorsal side corresponds to the five legs of a starfish. Holes near the tips of the petals allow the animal to extend tube feet, which are used for respiration. Most specimens measure about 3 inches (7.5 cm) in width. 

Sea cucumbers are a group of tubular echinoderms that he on their sides with their mouth at one end of the tube and anus at the other end. Around the mouth, several tube feet are modified to form tentacles. Some species use these to catch bits of food suspended in water or to pick up food-laden sediment. The respiratory structures of these animals are located alongside the digestive tract. 

The number and arrangement of tube feet on a sea cucumber vary, depending on the species. Usually found clinging to intertidal rocks, the orange-footed sea cucumber (Cucumaria fron-dosa) has tube feet arranged in five distinct bands along the length of its body. However, only the ones on the ventral side... 

Ech inodermata A phylum of marine invertebrates that includes the sea urchins, starfish, brittlestars, and sea cucumbers. Echinoderms have an exoskeleton (test) of calcareous plates embedded in the skin. In many species (e.g. sea urchins) spines protrude from the test. A system of water-filled canals (the water vascular system) provides hydraulic power for thousands of tube feet saclike protrusions of the body wall used for locomotion, feeding, and respiration. Echinoderms have a long history fossils of primi-... 

Fig. 7. Sections of sea cucumber and sea urchin, respectively showing the kteation of the body wall and the catch ligament in these animals. For clarity, the sea urchin is drawn with spines on the right and tube feet on the left in reality, these structures are intermixed over the whole surface. (After Hyman. I9. 55 Banister and Campbell, 1985 Pearse el al., 1987 Lambert. 1997.)...

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