A New Approach to the Immunological Analysis of Invertebrate Diets

Abstract

taneously analysing the gut contents of small invertebrates for the presence of up to eight prey species. Despite what would seem to be the obvious potential of the processes, immunological techniques have been relatively little used as ecological tools. The principal users have been Brook & Proske (1946), Hall et al. (1953), Dempster (1960), Young, Morris & Reynoldson (1964) and Davies (1967). However, most of the methods used by these authors have been designed and used to identify a single prey species in the guts of a variety of predators, and this aim and limitation may have retarded development of the principle as an ecological tool. A method has therefore been devised which has as its emphasis the detection of a number of different prey in the gut of a single predator. The essence of the technique is the miniaturization of the Ouchterlony plate principle (Ouchterlony 1948) in order that individual small invertebrates with volumes of as little as 0-01 ml can be tested. Although there is an enormous amount of clinical immunological literature, it proved impossible to discover any rules to serve as guidance in the development of the technique to be described. Much of the present work, therefore, is the result of trial and error based on such relevant information as could be discovered in the literature or by personal communication with persons who are engaged in work of a similar or allied nature. The process which will be set out here is therefore essentially a rule-of-thumb method which has as its chief recommendation the fact that it has survived exhaustive testing, proved virtually fool-proof once the basic mechanics have been mastered, and made possible a more complete analysis of the diets of small invertebrates. Most of the details of the development of the process will not be discussed here, but key references will be given to earlier work in this field from which it will become apparent what modifications have been introduced. All the examples given here are taken from the analysis of the diet of the planarian D. tigrina, but it will be apparent that only slight modifications of minor details are required to make the process suitable for analysis of any carnivorous invertebrate for a variety of prey organisms.