Ablation of antennae does not disrupt magnetoreceptive behavioural reaction of the American cockroach to periodically rotated geomagnetic field.

Neither a mode of function nor an exact anatomical localisation of the animal magnetoreceptor have been identified in any organism. Insects' antennae are organs specialized as unique neural input structures for a number of sensory modalities and have also been suggested to play a certain role in magnetoreception. In the present study, we used the American cockroach Periplaneta americana and tested the impact of amputation of both its antennae on the spontaneous magnetosensitive behaviour. By means of a full-laboratory assay we registered a non-specific unlearned movement reaction to the changing magnetic environment within the frame of the natural time and intensity parameters of the field. We report no loss of the magnetoreceptive behaviour in antennaeless cockroaches. Our finding narrows the spectrum of the insects' magnetite-rich nerve structures which might potentially be involved in magnetoreception.

Exploring with damaged antennae: do crayfish compensate for injuries?

Appendages are important sources of sensory information for all animals that possess them but they are commonly damaged in nature. We describe how the tactile system of the crayfish Cherax destructor functioned when subjected to the kind of damage found in wild-caught or cultured animals. Touch information was methodically varied by the removal of antennae and chelae. The resulting behaviour was analysed in a T-maze. Crayfish with a single antenna ablated turned toward the intact appendage, however, those with only a partial ablation did not, suggesting that a tactile information threshold exists for normal behaviour. When exposed to the same environment after an antennal ablation but with no prior experience in that terrain, crayfish also turned toward the side of the intact antenna. By contrast, when animals with experience obtained in a previous trial with intact antennae were tested after ablation of one antenna, they did not turn into one arm of the maze more than the other. These two outcomes indicate that behaviour is affected by an interaction between the time at which an injury occurs and an animal's knowledge of the topography, and that an injury may affect learning. We also tested to see if other appendages could provide tactile information to compensate for antennal loss. Input from the chelae did not affect the turning behaviour of crayfish in the maze.

Somatosensory cortex: structural alterations following early injury to sense organs.

In mouse somatosensory cortex there are discrete cytoarchitectonic units, called "barrels." Each barrel is related to one sensory vibrissa on the muzzle. Individual vibrissae were carefully injured at birth; 12 to 43 days later, the corresponding barrels proved to be absent. Evidently the sensory periphery has an important influence on the structure of the somatosensory cortex.