Response properties of the electrosensory neurons in hindbrain of the white sturgeon,Acipenser transmontanus

Objective The passive electrosense is a primitive sensory modality in the Chondrostei, which include sturgeon and paddlefish. Using electroreceptors, these fish detect the weak electric fields from other animals or geoelectric sources, and use this information for prey detection or other behaviors. The primary afferent fibers innervating the electroreceptors project to a single hindbrain target called the dorsal octavolateral nucleus （DON）, where the electrosensory information is first processed. Here, we investigated the electrophysiological properties of DON neurons. Methods Extracellular recording was used to investigate the response properties of DON neurons to dipole electric fields with different amplitudes and frequencies in the white sturgeon, Acipenser transmontanus. Results The DON neurons showed regular spontaneous activity and could be classified into two types： neurons with a low spontaneous rate （〈10 Hz） and those with a high spon- taneous rate （〉10 Hz）. In response to sinusoidal electric field stimuli, DON neurons showed sinusoidally-modulated and phase-locked firing. In addition, neurons showed opposite phase responses corresponding to the different directions of the dipole. Conclusion The response properties of DON neurons match the electrosensory biological function in sturgeon, as they match the characteristics of the electric fields of its prey.

Exquisite structure of the lateral line system in eyeless cavefish Sinocyclocheilus tianlinensis contrast to eyed Sinocyclocheilus macrophthalmus(Cypriniformes:Cyprinidae)

In this study,the lateral line systems in Chinese cavefish eyeless Sinocyclocheilus tianlinensis and eyed Sinocyclocheilus macrophthalmus were investigated to reveal their morphological changes to survive in harsh environments.Compared with the eyed cavefish S.macrophthalmus(atypical),the lateral line system in the eyeless cave-fish S.tianlinensis(typical)has certain features to adapt to the dark cave environments:the superficial lateral line system in the eyeless species possesses a higher number of superficial neuromasts and more hair cells within an individual neuromast,and the trunk lateral line canal system in S.tianlinensis exhibits larger canal pores,higher canal diameter and more pronounced constrictions.Fluid–structure interaction analysis suggested that the trunk lateral line canal system in the eyeless S.tianlinensis should be more sensitive than that in the eyed S.macrophthalmus.These morphological features of the lateral line system in the eyeless S.tianlinensis probably enhance the functioning of the lateral line system and compensate for the lack of eyes.The revelation of the form–function relationship in the cavefish lateral line system provides inspiration for the design of sensitive artificial flow sensors.