134 Mussel Beds; their Productivity and Maintenance 



The Conditions of Life on the Scars or Seed Areas. 



In his book, Life in the Sea^, J. Johnstone, discussing the views of 

 Putter and others, suggests the possibiUty that the respiratory and other 

 tissues of certain aquatic animals assist in the assimilation of certain 

 foodstuffs held in solution in the medium in which they are bathed. 

 That, in fact, it may be proved in tlie future that such tissues function 

 as the chief means^ in the nutrition of a large number of forms. In the 

 same connection, he calls attention to the relatively large extent of the 

 "so-called respiratory surface of the mollusc or ascidian...," both seden- 

 tary forms in which, as might be supposed, "the respiratory function is 

 much less important than it is in the case of a warm blooded animal," 

 because, in them, metabolism proceeds more slowly. He further dis- 

 cusses the possibility of the "anal respiration" of certain of the micro- 

 crustacea as being, partially at least, nutritive in character. This 

 hypothesis is a fascinating one, but the experiments of Moore, Edie, and 

 Whitley on the nutrition and metabolism of marine animals^ seem to 

 disprove Putter's results. Lobsters (to mention one instance) were 

 kept in seawater, which was regularly renewed, in tightly closed vessels. 

 All plankton was removed from this water before it was introduced into 

 the vessels. The lobsters lived as long as seven months under these 

 conditions. At the end of this time, they frequently registered an in- 

 crease in weight, but this was found to be due to what may be described 

 shortly as a water-logging of the tissues. As an alternative explanation 

 of the large respiratory surface shown by the types mentioned above 

 (sedentary types), among others, the following suggestion is made. The 

 rate of oxidation in many aquatic animals is very low, a fact which has 

 received somewhat belated recognition. Yet, even so, a relatively large 

 volume of water has to be treated by the organism in order to supply its 

 needs. It is fairly certain that, for various reasons, feeding is often 

 interrupted for longer or shorter periods. Therefore, the taking in of 

 food must be so adapted as to allow of a reserve being accumulated to 

 enable the organism to survive during periods when the supply is cut off. 

 This would go far towards explaining the large respiratory surface in 



1 Cambridge University Press. 



- Others regard vegetable detritus as the most important element in the food of J^ytilus 

 and some other forms. 



^ See article in the Report for 1913 of the Lanes, and Western Sea Fisheries Laboratory : 

 "The Nutrition and Metabolism of Marine Animals: the Rate of Oxidation and Output 

 of Carbon-dioxide in Marine Animals in Relation to the Available Supply of Food in Sea- 

 Water," by Professor Benjamin Moore, F.R.S., Edward S. Edie, B.Sc., and Edward 

 Whitley, M.A. 



