The Cephalic Morphology Of Morinoia Japonica (Talitridae, Amphipoda, Malacostraca) And Its Implications Of Terrestrial Adaptation And Phylogeny

The cephalic anatomical structures of Morinoia japonica were examined using X-ray micro-computed tomography (micro-CT), 3D reconstruction and scanning electron microscopy (SEM), to improve understanding of terrestrial adaptation and phylogenetic inferences. The cerebral nerves, skeletons and musculatures were described in detail based on the observation results. As observed with other terrestrial amphipoids, M. japonica has a reduction in size of the olfactory lobes in the small deutocerebrum and the antenna 1 nerve (in short antennae 1), which might be the apomorphies of Talitridae. Organ of Bellonci is absent in M. japonica. The unfused tentorial arms of M. japonica might be a plesiomorphic state in Amphipoda. The fusion of both peduncular articles 1 and 2 of antenna 2 is another apomorphy of Talitridae, which is also the taxonomic diagnosis of the family. The cephalic musculatures of M. japonica, another amphipod species Gammarus minus (Gammaridae), Daphnia (Branchiopoda), Godzilliognomus frondosus (Remipedia) and Dicondylia (Insecta) were homologized. The markedly reduced foregut muscles of M. japonica are suggested to be associated with its feeding on soft moss. (c) 2021 Elsevier GmbH. All rights reserved.