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|Title:||Neuroanatomical and Neurophysiological Aspects of Vibrational Processing in the Central Nervous System of Semi-Terrestrial Crabs|
|Author(s):||Hall, Jimmy Cree|
|Department / Program:||Neuroscience|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Fiddler crabs (Uca) use substrate-borne vibrational signals during social interactions. The aims of this study were to determine (1) the central representation of vibrational stimuli in fiddler crabs, and (2) the generality of these findings as they relate to analogous systems in other arthropods.
Neuron response properties and projection areas in U. minax and U. pugilator were determined by extracellular and intracellular recording and staining techniques. Similar anatomical features in two other semi-terrestrial crabs (Ocypode quadrata and Sesarma cinereum) were contrasted with those of the fiddler crabs.
Five types of neurons were identified in U. minax. When presented with pulsed tones two (Phasic-I and Phasic-II) responded to pulse onset with a brief burst of spikes, two (Tonic-I and Tonic-II) responded for the duration of each pulse, and the "spontaneous" activity of one (Inhibited) was suppressed during stimulation. Phasic-I and Phasic-II units functioned as temporal filters with different high-frequency cut-off points. Tonic-II, but not Tonic-I, units functioned as low-pass frequency filters. The combined activity of the neurons encoded all major temporal, but not spectral, features of the crabs vibrational signals. The former are probably critical for communication. Units with similar response properties were described for U. pugilator. Thus, vibrational information is processed in an analogous fashion in both species.
Each response type was correlated with a unique neural geometry. With the exception of Phasic-I units, those with similar response properties showed interspecific differences in structure, probably reflecting their independent evolution in the two species.
The principal projection site of the neurons was the dorso-medial tritocerebral neuropile (DMTN), described here for the first time. A similar structure was also found in O. quadrata (where it is probably a homolog) and S. cinereum (where it is probably an analog). Across-species size comparisons showed the neuropile to be larger in species with a well-developed system of vibrational communication. Hence, the DMTN probably functions as a vibrational neuropile in all these forms.
Similarities between the fiddler crab neurons and their analogs in the insect suggests a remarkable degree of convergence between these groups.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.
|Date Available in IDEALS:||2015-05-14|