I have been working on various aspects of arthropod neurobiology for more than 30 years. Within this area, the focus is chemoreception of decapod crustaceans which comprise shrimp, spiny lobsters, clawed lobsters, crayfish, true crabs and hermit crabs.
In various species I have studied the physiology of receptor neurons, their projection to processing areas in the central nervous system in particular the brain, and the functional organization of brain pathways processing chemosensory information.
The deeper question driving my research is why chemoreception in crustaceans is differentiated into two morphologically distinct ‘chemical senses’. One of these chemical senses is olfaction (the sense of smell) which is mediated by specialized chemosensory hairs (aesthetasc sensilla) on the first pair of antennae called antennules and a dedicated olfactory pathway in the brain. The other chemical sense is ‘distributed chemoreception’ which is constituted by numerous other chemosensory sensilla that cover the body and all appendages and the associated regions of the ventral nerve cord and brain to which these sensilla send their input. My research question originates from the fact that in contrast to land-living animals where the two main chemical senses are specialized to detect physically different molecules (olfaction detects volatiles whereas taste detects water-soluble molecules) crustaceans are aquatic animals and therefore are exposed to water-soluble molecules only. Since aquatic animals predate terrestrial ones, the evolutionary origin of olfaction can have nothing to do with a specialization for detecting volatiles (which is a later adaptation to terrestrial life) and thus there must be different reason that caused the evolution of the sense of smell. Contributing to elucidate this ‘true’ reason for the evolutionary origin of olfaction is the aim of my work.
Schmidt M. 2014. Adult neurogenesis. In: Derby CD, Thiel M, editors. The Natural History of the Crustacea – Volume 3. Crustacean Nervous Systems & their Control of Behavior. New York: Oxford University Press (in press).
Tadesse T, Derby CD, Schmidt M. 2014. Mechanisms underlying odorant-induced and spontaneous calcium signals in olfactory receptor neurons of the spiny lobster, Panulirus argus. J Comp Physiol [A] 200:53-76.
Schmidt M, Derby CD. 2011. Cytoarchitecture and ultrastructure of neural stem cell niches and neurogenic complexes maintaining adult neurogenesis in the olfactory midbrain of spiny lobsters, Panulirus argus. J Comp Neurol 519:2283-319.
Schmidt M, Mellon D, Jr. 2011. Neuronal processing of chemical information in crustaceans. In: Breithaupt T, Thiel M, editors. Chemical Communication in Crustaceans. New York, Dordrecht, Heidelberg, London: Springer Science + Business Media, LLC; p 123-47.
Shahbazi M, Schmidt M, Carruth LL. 2011. Distribution and subcellular localization of glucocorticoid receptor-immunoreactive neurons in the developing and adult male zebra finch brain. Gen Comp Endocrinol 174:354-61.
Tadesse T, Schmidt M, Walthall WW, Tai PC, Derby CD. 2011. Distribution and function of Splash, an achaete-scute homolog in the adult olfactory organ of the Caribbean spiny lobster Panulirus argus. Dev Neurobiol 71:316-35.
Chien H, Tadesse T, Liu H, Schmidt M, Walthall WW, Tai PC, Derby CD. 2009. Molecular cloning and characterization of homologs of Achaete-Scute and Hairy-Enhancer of Split in the olfactory organ of the spiny lobster Panulirus argus. J Mol Neurosci 39:294-307.
Song C-K, Johnstone LM, Edwards DH, Derby CD, Schmidt M. 2009. Cellular basis of neurogenesis in the brain of crayfish, Procambarus clarkii: neurogenic complex in the olfactory midbrain from hatchlings to adults. Arthrop Struct Dev 38:339-60.
Horner AJ, Schmidt M, Edwards DH, Derby CD. 2008. Role of the olfactory pathway in agonistic behavior of crayfish, Procambarus clarkii. Invert Neurosci 8:11-8.
Schmidt M. 2007a. Identification of putative neuroblasts at the base of adult neurogenesis in the olfactory midbrain of the spiny lobster, Panulirus argus. J Comp Neurol 503:64-84.
Schmidt M. 2007b. The olfactory pathway of decapod crustaceans – an invertebrate model for life-long neurogenesis. Chem Senses 32:365-84.
Song C-K, Johnstone LM, Schmidt M, Derby CD, Edwards DH. 2007. Social domination increases neuronal survival in the brain of juvenile crayfish Procambarus clarkii. J Exp Biol 210:1311-24.
Johnson PM, Kicklighter CE, Schmidt M, Kamio M, Yang H, Elkin D, Michel WC, Tai PC, Derby CD. 2006. Packaging of chemicals in the defensive secretory glands of the sea hare Aplysia californica. J Exp Biol 209:78-88.
Schmidt M, Chien H, Tadesse T, Johns ME, Derby CD. 2006. Rosette-type tegumental glands associated with aesthetasc sensilla in the olfactory organ of the Caribbean spiny lobster, Panulirus argus. Cell Tissue Res 325:369-95.
Schachtner J, Schmidt M, Homberg U. 2005. Organization and evolutionary trends of primary olfactory brain centers in Tetraconata (Crustacea+Hexapoda). Arthrop Struct Dev 34:257-99.
Schmidt M, Derby CD. 2005. Non-olfactory chemoreceptors in asymmetric setae activate antennular grooming behavior in the Caribbean spiny lobster Panulirus argus. J Exp Biol 208:233-48.
Hansen A, Schmidt M. 2004. Influence of season and environment on adult neurogenesis in the central olfactory pathway of the shore crab, Carcinus maenas. Brain Res 1025:85-97.