. Animal ecology. Animal ecology. 76 ANIMAL ECOLOGY fox dies, and this is also brought about by the food-cycle. For the tapeworm produces vast numbers of eggs which pass out with the excretory products of the fox ; some of these eggs contaminate the vegetation which the rabbit is eating, or in some other way get in with its food, and are then able ultimately to grow up into more bladderworms in the body of the rabbit. The diagram in Fig. 6 shows the way in which the food-cycle PLANTS --EggD-- ^RABBIT Larvae- +»POX Adult Fig. 6. acts as a means of conveyance for the parasites, throughout its li
. Animal ecology. Animal ecology. 76 ANIMAL ECOLOGY fox dies, and this is also brought about by the food-cycle. For the tapeworm produces vast numbers of eggs which pass out with the excretory products of the fox ; some of these eggs contaminate the vegetation which the rabbit is eating, or in some other way get in with its food, and are then able ultimately to grow up into more bladderworms in the body of the rabbit. The diagram in Fig. 6 shows the way in which the food-cycle PLANTS --EggD-- ^RABBIT Larvae- +»POX Adult Fig. 6. acts as a means of conveyance for the parasites, throughout its life-cycle. 7. This was a fairly simple case. There is always this tendency for parasites to get transferred from one stage in a food-chain to the next, like passengers on a railway. Many parasites get out at the first station—in other words, they have a direct Hfe-history, with no alternate host. An example of this is a tapeworm {Hymenolepis) which occurs in mice, and which has the larval and adult stages in the same host, although in different parts of the body.^^ Or the parasite may get out at the second station, like the rabbit tapeworm described above. Or again, it may travel as far as a third host. The broad tape- worm {Diphyllohothrium latum), which occurs occasionally in man, causing severe ansemia, gets into the gut of some small fresh-water copepod { Cyclops strenuus or Diaptomus WATER- 'COPEPOD- , Egg ^—Larva ->- Larva—^—. Fig. 7. gracilis) with the food of the latter, is then eaten by fish in which it exists in the form of bladderworm cysts, and is finally eaten by some carnivore or by man.^* The diagram (Fig. 7) sums up this Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Elton, Charles S. (Charles Sutherland), 1900-. New York, Macmillan Co.
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