The foregut of the Mysida (Crustacea, Peracarida) and its phylogenetic relevance

Abstract

The foreguts of the mysids Antarctomysis maxima , A. ohlinii , Hansenomysis antarctica , Heteromysis formosa , Mesopodopsis slabberi , Neomysis integer , Paramysis kessleri , Praunus flexuosus , and Siriella jaltensis were examined by maceration methods, histological techniques, and scanning electron microscopy. Their morphology, their connection with the midgut glands, and probable function are described and summarized. Previous stomach investigations on mysids and the results of the present study are tabulated; a list of foregut characters, common to all Mysida, is presented. The phylogenetic relevance of these characters within the Malacostraca, especially within the Peracarida, is discussed. Most features are inherited from the ground pattern of the Malacostraca or Eumalacostraca. The bulbous cardia with its dorsal fold, the armature of the lateralia, and the construction of the funnel region are apomorphies for the Mysida. The results suggest that characters of mysidan and other peracaridan foreguts might also be useful in the elucidation of the phylogeny of the Mysida and Peracarida, respectively.