On the Innervation and Homologues of the Cephalic Appendages of the Aphroditacea (Polychaeta)

Abstract

Abstract Earlier papers dealing with the innervation and homologues of the anterior end appendages of some aphroditacean families were re‐studied. However valuable these earlier works may be, in some respects they proved to be insufficient for detailed comparisons with other polychaete families and some of their statements are quite contradictory. This prompted a re‐investigation of the central‐most parts of the nervous system of representatives of the families Polynoidae, Sigalionidae, Aphroditidae and Acoetidae. In the present paper, the brain commissures and the innervation of, inter alia , the antennae, the palps and the ommatophores (when present) in Lepidonotus squamatus, Harmothoe longisetis, Leanira (Sthenolepis) tetragona, Laetmonice producta benthaliana , and Panthalis oerstedi are described. Special attention is paid to the much‐debated question about the presence or absence of a palp ganglion. The results, summarized in schematic diagrams, are compared with corresponding observations of the brains of, above all, the ‘spiomorphic’ polychaetes. Using the first Remanian criterion for identifying homologies, equivalents in the aphroditacean brain and the central nervous system of ‘sedentary’ families are proposed. By this a broader base is established for the discussion regarding the fundamental constitution of the anterior end of the polychaetes and the structure and homologues of their cephalic appendages.