Studies on the antennal sensilla of selected blackflies (Diptera: Simuliidae)

The types, numbers, and distribution of the antennal sensilla of male and female Simulium rugglesi and S. baffinense, and female S. venustum and S. euryadminiculum have been determined. Seven sensillar types, including olfactory receptors, contact chemoreceptors, and mechanoreceptors, were distinguished on all specimens examined. The results are discussed with regard to the feeding habits of the various species.

Rapid degeneration of ampullary electroreceptor organs after denervation

Electroreceptors (ampullary organs) of the transparent catfish (Kryptopterus bicirrhus) lie in the epidermis, and contain spherical receptor cells that receive purely afferent innervation from the lateral line nerve. Section of this nerve causes rapid degenerative changes to occur in the receptors. Fine structural alterations occur in the receptor cell synapses and nerve fiber 6-12 h postoperatively. Disruption of the receptor cells begins by 18 h and most are lost by 48 h. By 72 h supporting cells and secretory cells also show marked degeneration, and by 96 h they may be totally lost. The rapid degeneration of the electroreceptor organs of Kryptopterus should make them a useful preparation for analysis of neurotrophic functions.

An Analysis of the Types of Sensory Unit Present in the PD Proprioceptor of Decapod Crustaceans

1. The PD organs of various decapod crustaceans were stimulated by elongation and relaxation of the strand, and single-unit recordings were made from the different types of sensory unit.

2. The sensory units can all be placed in one or other of three categories: unidirectional movement cells, position cells and intermediate cells.

3. Unidirectional movement cells are large, phasic units which respond either to elongation or relaxation of the strand. Some are pure movement-sensitive units, which reach saturation at very low movement velocities and fire over most or all of the range of movement. Other units show velocity sensitivity and differential range sensitivity in varying degrees.

4. Position cells are small tonic units and are usually maximally sensitive at one end of the range of movement. Their firing pattern is asymmetric in that the frequency of impulses is dependent on the direction of movement by which a given position is achieved.

5. Intermediate cells have large phasic and tonic components which may or may not show a direct relationship to each other.

6. The importance of the detailed information produced by the PD organ is discussed and suggestions made as to how it could be utilized by the central nervous system.