Free amino acid patterns and the classification of the Demospongiae

Abstract

An investigation of the free amino acid patterns of 67 species representing 50 genera of West Indian Demospongiae has been undertaken to examine the value of this biochemical approach in adding another parameter to phylogenetic inquiries. Two-dimensional thin-layer electrophoresis and chromatography were used to separate mixtures of naturally occurring ninhydrin-positive compounds. Individual components were identified as far as possible, and the fingerprints or patterns of the species studied were used as a basis for evaluating relationships. The subclass Ceractinomorpha is a relatively homogeneous group, with free amino acid patterns characterized by a consistent representation of protein amino acids and by the absence of compounds other than taurine and hypotaurine in the neutral region of the chromatogram. Two variants of this general pattern can be recognized, one found in the orders Dictyoceratida and Poecilosclerida, the other occurring in the order Haplosclerida and the family Halichondriidae of the order Halichondrida. Unexpected results within this subclass are the wide separation of the dictyoceratid families Spongiidae and Verongiidae, the anomolous patterns of the genera Agelas and Iotrochota and of the family Callyspongiidae, and the suggestive affinities of the family Hymeniacidonidae with the order Hadromerida. The subclass Tetractinomorpha appears to represent a polyphyletic assemblage in which 5 recognizable patterns can be distinguished. These represent the orders Homosclerophorida, Choristida, Spirophorida, Hadromerida and Axinellida. Of interest are the suggestions that the order Choristida is in itself a heterogeneous group, and that certain genera now placed in the order Axinellida may in fact be more closely related to the Poecilosclerida.