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Carapace and mandibles ontogeny in the Dendrobranchiata (Decapoda), Euphausiacea, and Mysidacea (Crustacea): a phylogenetic interest

2002; NRC Research Press; Volume: 80; Issue: 2 Linguagem: Inglês

10.1139/z02-011

1480-3283

Bernadette Casanova, Laetitia De Jong, Xavier Moreau,

Fish Biology and Ecology Studies

The ontogeny of the carapace and the mandibles has been studied for one species of Dendrobranchiata (Decapoda), four species of Euphausiacea, and three species of Mysidacea (one species of Lophogastrida and two species of Mysida). The protocephalic origin of the carapace, which arises from the antennar tergite, is confirmed. During larval development the progressive dorsal insertion of the carapace leads to the opening of the tergites of both cephalic and thoracic segments. The opening of the eight thoracic segments (TS) occurs in Euphausiacea and Decapoda only, and is done in three steps (TS1; TS1–TS3 or TS1–TS4; TS1–TS8). In adult Mysidacea, the insertion of the carapace exhibits two levels of evolution (opening of TS1 in Gnathophausia species and of TS1–TS4 in the others). Thus, in the larvae of Euphausiacea and Decapoda, the most evolved taxa, the progressive insertion of the carapace corresponds to the carapace locations in the adults of the most ancient taxa, i.e., Mysidacea. The location of the internal musculature of the mandibles, which is known for certain to characterize the different parts of the arthropodial segment, and their development, shows that the gnathal part of each mandible is prolonged by a pleural part and half the residual tergite of the mandibular segment.