Figure 2. Comparative brain overview in Caridean vent and shallow-water species.

Lateral sketches of the brains of the vent shrimp Rimicaris exoculata (A) and the closely-related shallow-water shrimp Palaemon elegans (B), showing the brain position within the cephalothorax, the position of the main nerves and the subdivision of the brain into three neuromeres called proto-, deuto- and tritocerebrum, plus the visual neuropils. In contrast to P. elegans, R. exoculata does not possess eyestalks and the visual neuropils are fused to the median brain, in a dorsoposterior position behind the lateral protocerebrum. Abbreviations: see text and appendix 1.