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The Ciliary Mechanisms on the Gill and the Mode of Feeding in Amphioxus, Ascidians, and Solenomya togata

Published online by Cambridge University Press:  11 May 2009

J. H. Orton
J. H. Orton
Affiliation:
Naturalist in the Plymouth Laboratory.
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Summary

The mode of feeding in Amphioxus is effected by–

(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.

Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 10 , Issue 1 , November 1913 , pp. 19 - 49
Copyright
Copyright © Marine Biological Association of the United Kingdom 1913

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References

* The observations recorded in this paper were made on the species Branchiostoma lanceolatum. the general similarity in structure of the species of this genus, however, renders it highly probable that the processes here described will apply to all the group.

* I am indebted to Mrs. Orton for the drawing for this figure, and also for assistance with Figures 6, 8, and 9.

* It was found the most convenient for t his examination to view the animal laid on its right side. Thus in this view the main current passes from the reader's right to the left.

* I am indebted to Mr. L. R. Crawshay for the lettering in this figure, and also for that in Figures 2, 3, and 5.

† The short cilia figured by Benham (15, Plate 6) have not yet been seen in the living filament, although they have been carefully looked for. Further observations, however, will be made on this point.

* See Appendix on page 45 for an accosunt of Andrew's work on feeding in Amphioxus.

* If a stronger solution of methylene blue is used the whole ofthe whool organ as well as the pharynx stains a deep blue, anda surprising amount of detail can be made out over the whole of the body.

* Since this account was sent to the printer, a paper by E.S. Morse on Solonomya in the current number of the Biological Bulletin, Woods Hole, has come to hand. This paper gives an account of observations on living Solenomya velum and S. borealis Morse has observed the palps being used for transferring food from the gill to the mouth, which fact, added to those given above, completes our knowledge of the feeding in Solenomya.