Glomerular organization in developing olfactory and accessory lobes of American lobsters: Stabilization of numbers and increase in size after metamorphosis

Abstract

Olfactory glomeruli are columnar and radially arranged at the periphery of the primary chemosensory areas, the olfactory lobes (OLs), in the American lobster Homarus americanus. The number of olfactory glomeruli reaches nearly 100/lobe in midembryonic life, increases rapidly during larval life, and stabilizes at about 200 in juvenile and adult lobsters. The accessory lobes (ALs), higher order integration areas, are composed of cortical columns and of spherical glomeruli. Two populations of spherical glomeruli are defined, the cortical glomeruli located at the bases of the columns, and the medullary glomeruli scattered throughout the ALs. Both cortical columns and spherical glomeruli are seen for the first time in the second larval stage. There are about 1000 cortical columns and 1700 glomeruli/AL in the postlarva and these numbers remain constant during the life of the lobster. In both OLs and ALs, it is the size of the interglomerular spaces and of the glomeruli themselves that increases. Therefore, the data suggest that in both OLs and ALs the glomeruli were already generated when the lobster metamorphoses (stage III to IV) and switches from a planktonic to a benthic existence, and that the new sensory neurons that are formed at each molt in the antennulae grow into existing olfactory glomeruli. Stability of the glomerular population in the primary olfactory centers, once the full complement of glomeruli is acquired, has also been reported in insects, fish, and mammals. © 1996 John Wiley & Sons, Inc.

Early embryonic development of the central nervous system in the Australian crayfish and the Marbled crayfish (Marmorkrebs)

“…Our study therefore supplements previous studies that have focussed on other malacostracan species, on later embryonic or larval stages, or on the ontogeny of specific sub-systems of the CNS, such as the olfactory system or neurotransmitter systems (e.g. Elofsson 1969;Beltz et al 1990;Sandeman and Sandeman 1990;Beltz et al 1992;Whitington et al 1993;Helluy et al 1993Helluy et al , 1995Helluy et al , 1996Schneider et al 1996;Harzsch et al 1997), but in which the earliest neurogenetic events especially in the brain have not been screened. We present here for the first time a systematic analysis of how the primordial scaffold of the CNS unfolds in crayfish embryos, a group of organisms that are important models in crustacean neuroscience as a recent special issue devoted to the crayfish nervous system edited by Tierney (2003) shows.…”

Brain architecture of the largest living land arthropod, the Giant Robber Crab Birgus latro (Crustacea, Anomura, Coenobitidae): evidence for a prominent central olfactory pathway?

“…One hypothesis is that these may be precursor structures of the glomeruli. Previous studies in the American lobster Homarus americanus Weber, 1795 have, however, shown that the number of olfactory glomeruli is almost stable in adult specimens [75]. From developmental studies in Cherax destructor is known that the number of glomeruli is set in early development and that the synaptic area increases with growth (Sandeman R. unpublished).…”

Effects of serotonin depletion on local interneurons in the developing olfactory pathway of lobsters

“…Glomerular formation and presumably synaptogenesis in the accessory lobes occur during larval life (Helluy et al, 1996). In contrast, in the olfactory lobe, glo-…”