Evolution of thioester-containing proteins revealed by cloning and characterization of their genes from a cnidarian sea anemone, Haliplanella lineate.

To elucidate the evolutionary origin of genes encoding thioester-containing proteins (TEPs), TEP genes were isolated from a cnidarian, a sea anemone, Haliplanella lineate. Phylogenetic tree analysis of the four identified cnidarian TEP genes and various TEP genes of many metazoa, indicated that they could be classified into two subfamilies: the alpha-2-macroglobulin (A2M) subfamily encodining A2M, CD109 and insect TEPs, and the C3 subfamily encoding complement C3, C4 and C5. Two of the four cnidarian TEP genes belonged to the A2M subfamily, showing a close similarity to human A2M and CD109, respectively and thus were termed HaliA2M and HaliCD109. The other two genes belonged to the C3 subfamily, and were termed HaliC3-1 and HaliC3-2. Cnidarian TEPs retained the basic domain structure and functionally important residues for each molecule, and their mRNA were detected at different parts of the sea anemone body. These results suggest that gene duplication and subsequent functional differentiation among C3, A2M and CD109 were very ancient events predating the divergence of the cnidaria and bilateria.

Avoidance learning in the crayfish (Procambarus clarkii) depends on the predatory imminence of the unconditioned stimulus: a behavior systems approach to learning in invertebrates.

Signaled avoidance learning in crayfish (Procambarus clarkii) was investigated when the crayfish were not confined, by indexing two types of locomotive movement to the escape compartment. Mild shocks, which induced tail flipping in the crayfish, and light illumination were used as unconditioned and conditioned stimuli, respectively. In Experiment 1, two groups of crayfish were trained in a one-way shuttle box. The crayfish in Group Forward were placed in the start compartment facing the escape compartment and they were able to escape/avoid shocks by walking forward, while the crayfish in Group Backward were placed in the compartment facing the opposite direction and they were able to escape by tail flipping. Avoidance learning was achieved only by walking, and not by tail flipping despite the fact that consistent tail flipping allowed the crayfish to avoid shocks. In Experiment 2, the experimental conditions were switched by using the ABA design. In this experiment, we confirmed that avoidance behavior was restricted to walking. These results are readily explained by the behavior systems approach.