Presentation Title

Distinct Neurochemical Regions Within the Elephant Shark’s (Callorhincus milli) Forebrain Suggest Evolutionary Conservation

Advisor Information

Paul Davis

Location

Dr. C.C. and Mabel L. Criss Library

Presentation Type

Poster

Start Date

7-3-2014 1:00 PM

End Date

7-3-2014 4:00 PM

Abstract

Neurochemical markers are highly conserved across species. Our objective was to test the hypothesis that the forebrain’s major regions have evolved in the ancestors of jawed vertebrates. Using juvenile Callorhinchus brains and various stains, eight major areas of the telencephalon were identified which are also present in bony vertebrates. Five antibodies and one enzyme known to stain specific compartments of other vertebrates’ forebrains were utilized. Within this shark’s brain, major neurochemically distinct regions were present which share expression patterns with those described in mammals, amphibians, and fish: In the subpallium: (1) A rostroventral area comparable to striatum; (2) A rostromedial ventral area comparable to accumbens; (3) A rostromedial dorsal area comparable to the septal area; (4) A caudoventral area comparable to the central amygdala; (5) A caudodorsal area comparable to the medial amygdala. In the pallium: (1) A main olfactory bulb; (2) an accessory olfactory bulb; (3) a dorsomedial pallial area comparable to the hippocampus; (4) a lateral pallial area comparable to olfactory pallium; and (5) an area deep to the lateral pallium comparable to the lateral amygdala. These results indicate that these major regions can be recognized in the Callorhinchus milli’s forebrain, which have analogous characteristics and topology to those in bony vertebrate species. Therefore, these compartments most likely evolved prior to the evolution of jawed vertebrates.

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Mar 7th, 1:00 PM Mar 7th, 4:00 PM

Distinct Neurochemical Regions Within the Elephant Shark’s (Callorhincus milli) Forebrain Suggest Evolutionary Conservation

Dr. C.C. and Mabel L. Criss Library

Neurochemical markers are highly conserved across species. Our objective was to test the hypothesis that the forebrain’s major regions have evolved in the ancestors of jawed vertebrates. Using juvenile Callorhinchus brains and various stains, eight major areas of the telencephalon were identified which are also present in bony vertebrates. Five antibodies and one enzyme known to stain specific compartments of other vertebrates’ forebrains were utilized. Within this shark’s brain, major neurochemically distinct regions were present which share expression patterns with those described in mammals, amphibians, and fish: In the subpallium: (1) A rostroventral area comparable to striatum; (2) A rostromedial ventral area comparable to accumbens; (3) A rostromedial dorsal area comparable to the septal area; (4) A caudoventral area comparable to the central amygdala; (5) A caudodorsal area comparable to the medial amygdala. In the pallium: (1) A main olfactory bulb; (2) an accessory olfactory bulb; (3) a dorsomedial pallial area comparable to the hippocampus; (4) a lateral pallial area comparable to olfactory pallium; and (5) an area deep to the lateral pallium comparable to the lateral amygdala. These results indicate that these major regions can be recognized in the Callorhinchus milli’s forebrain, which have analogous characteristics and topology to those in bony vertebrate species. Therefore, these compartments most likely evolved prior to the evolution of jawed vertebrates.