Determining Magnetic Sensitivity of Armina californica; and of Neurons Homologous to those in Tritonia tetraquetra (a.k.a. T. diomedea)

Abstract

The gastropod nudibranch Tritonia tetraquetra is a convenient model organism for neurobiologists. It appears unique among nudibranchs in its ability to detect and orient to the magnetic field of Earth, which makes it an interesting basis for comparison. In our study, we assess the potential of magnetoreception in another nudibranch that shares a similar geography and lifestyle, Armina californica. We examine the neurons in Armina that are reported to be homologous to the known neural correlates of magnetoreception in Tritonia, and attempt to observe changes in activity while providing magnetic stimuli. Furthermore, we look for potential behavioral clues in the reorientation of displaced animals in natural and unnatural magnetic fields. Our results demonstrated that although A. californica and T. tetraquetra lead similar lives, Armina exhibited no significant responses to magnetic stimuli, either in neurophysiological or behavioral assays. These results suggest that Tritonia may be more unique than previously thought, and that magnetoreception may be limited to a very specific subset of gastropods.