W.B.C.S. Notes – Zoology – Ciliary Mode Of Feeding.
The mode of feeding in Amphioxus is effected by.Continue Reading W.B.C.S. Notes – Zoology – Ciliary Mode Of Feeding.
(1) The maintenance of a stream of water through the pharynx by rows of lateral cilia on the gill-bars.
(2) The throwing out of mucus from the endostyle on to the gill-bars to serve for entrapping food-particles.
(3) The collection of food-particles by rows of cilia on the pharyngeal surface of the gill-bars; these cilia woraSkip the foodparticles with mucus into cylindrical masses and transport such masses dorsally into the dorsal groove which carries the collected masses backwards into the digestive tract.
Thus the ciliary mechanisms on a gill-bar of Amphioxus are exactly the same as those on the gill-filaments of some Lamellibranchs, as Pecten, and some Gastropods, as Crepidula.
A subsidiary mode of food-collection is effected in the buccal cavity of Amphioxus by the ciliated tract known as the wheel organ, and Hatchek’s pit, which supplies mucus for entrapping food-particles. These particles are passed on to the peri-pharyngeal bands which, conduct them in turn into the dorsal groove.
The gill of Amphioxus functions mainly as a feeding organ and a water pump, and probably not at all as an organ for aerating the blood.
The mode of feeding in Ascidians is almost exactly the same as that described above for Amphioxus. Food-collection, however, in Ascidians is effected by cilia on the papillae and similar outgrowths on the gill, and is also helped in some forms by transverse waving of the longitudinal bars, by which process the food is pushed as well as lashed towards the dorsal region of the pharynx.
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