COMPARATIVE EMBRYOLOGY OF SPONGES AND ITS APPLICATION FOR PORIFERAN PHYLOGENY

Abstract

On the basis of original and literature data on embryonic development of Porifera, 7 developmental types accompanying sexual reproduction may be found within recent sponges. These types are called by the names of the resulting larvae: I - “trichimella” (Hexactinellida); II - “calciblastula” (Calcinea); III - “amphiblastula” (Calcaronea); IV - “cinctoblastula” (Homoscleromorpha); V - “disphaerula” (Halisarcida); VI - direct development (Tetilla, Spirophorida); VII - “parenchymella” which can be subdivided in to three subtypes: subtype 1 (Dendroceratida, Dictyoceratida, Halichondrida, Hadromerida); subtype 2 (Poecilosclerida); subtype 3 (Haplosclerida). The results of embryological analysis of sponges emphasize the necessity for further investigations of sponge embryology and reevaluation of phylogenetic relationships between some poriferan groups. According to morphological and embryological data the Homoscleromorpha is not subclass of the Demospongiae; this group of sponges shares several characteristics with the Eumetazoa.