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INTERRELATIONSHIPS AND TAXONOMY OF THE DIGENETIC TREMATODES
Author(s) -
STUNKARD HORACE W.
Publication year - 1946
Publication title -
biological reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.993
H-Index - 165
eISSN - 1469-185X
pISSN - 1464-7931
DOI - 10.1111/j.1469-185x.1946.tb00321.x
Subject(s) - biology , digenea , taxonomy (biology) , evolutionary biology , morphology (biology) , zoology , trematoda , helminths
Summary The purpose and objective of classification is to portray genetic relations by taxonomic symbols. Adoption by trematodes of a parasitic mode of life has induced changes in nutrition, physiology, morphology, life cycles and development. These adaptive modifications have resulted in both convergent and divergent evolution. Criteria for determining genetic relations must be assessed with caution and no single measure can be accepted as reliable or adequate. Although certain features appear to be correlated, they may have developed independently and the evaluation and interpretation of diagnostic characters is very difficult. Types of adhesive organs and the extent of their development may be associated with the site of infection, but life histories and the type of development afford more significant information concerning genetic relations. Consideration of morphological and developmental data lead to the conviction that in the Digenea, the higher taxonomic units have little phylo‐genetic or systematic significance. It is proposed therefore, to suppress the orders Gasterostomata and Proso‐stomata, and in the latter the suborders, Amphistomata, Distomata, Monostomata, Strigeata, Bucephalata, Schisto‐somata and Clinostomata. Although superfamily groups may be recognized, their limits and interrelations are not yet clearly defined and their erection should await more complete information. Former systems for classification of adults were based on morphological features, some of which have proved unreliable, and life‐history data are yet too meagre for final evaluation and application. Classifications of larval stages, based on types of asexual generations or on larval structures such as form of tails, presence of stylets, etc., have proved more unsound than classifications of adults. Only an analysis, evaluation and correlation of all data can produce a truly natural system. Such a system must be based on and portray the evolutionary history of the trematodes. Phylogenetic considerations are reviewed and applied to taxonomic problems.