The corpora pedunculata of Sphinx Ligustri L. and other Lepidoptera: an anatomical study

Abstract

The corpora pedunculata, or mushroom bodies, are paired lobes of neuropile present in the protocerebrum or dorsal brain of all insects. They are divisible into three parts: calyx, stalk and roots. The latter usually comprise two simple lobes, the a and ft lobes. The corpora pedunculata of a variety of Lepidoptera were examined. All had a double calyx-cup. Each ‘cup-cavity’ is composed of ‘globuli’ cell bodies. The broad stalk, a tract of fibres and neuropile, leads from the calyx to the complex ‘roots’—a, g and y lobes. A third group of globuli cells near the calyx gives rise to a tract leading to a second lobe-system—the tripartite Y-lobe—in the roots. As neither the Y tract nor the Y lobe has been described before in any insect, their possible homologues are unknown. The two lobe systems in the roots are closely intertwined, yet have no interaction except in the y lobe. A number of different neuron types with branches in the mushroom bodies has been described from Golgi preparations. Some (intrinsic cells) divide in the calyx and again in the roots, but do not pass out of the mushroom bodies. Others (extrinsic cells) branch in the mushroom bodies and in other areas of the brain, thus connecting two regions. Intrinsic cells arise from cell bodies in the calyx-cups or posterior to them. There are two types: one has extensive spine-covered branches in the calyx, while the second has claw-like terminals covering a narrow cylindrical field. Processes from these cells run to the a, j>and y lobes via the stalk. A wide-field accessory cell, which arises from the third group of globuli cell bodies, also has claw-like endings in the calyx. A process of this cell runs in the Y-tract to the Y-lobe. Extrinsic terminals in the calyx arise from cells branching in the antennal lobe, in an accessory optic area in the protocerebrum, in the ‘undifferentiated’ protocerebral neuropile, or in the suboesophageal lobes. The antennal terminals in the calyx are knob-like. It is proposed that they form the centre of the ‘glomeruli’ typically present in calycal neuropile. The claws of the bunched intrinsic and accessory cells probably fit around these knobs. Within the stalk, different subvarieties of intrinsic cells have been distinguished on the basis of the distribution of the side-branches and spines which they bear. The stalk is thought to be the site of extensive postsynaptic interaction between intrinsic cells. Fibres in the stalk run in bundles or groups. All the fibres in one bundle are of the same subvariety. In the roots, the subvarieties of intrinsic cells have different branching patterns. The a and B lobes are not homogeneous, but are divided into sublobes. Extrinsic fibres ramify only within one sublobe generally, though some have very large fields. The connexions of the roots are obscure. Some extrinsic fibres branch again in the ‘undifferentiated’ protocerebral neuropile; others, from the B lobe, may run to the suboesophageal lobes. There are profound differences between the internal organization of the mushroom bodies in Hymenoptera (Kenyon 1896; Goll 1967) and Lepidoptera. The functional implications of the Lepidopteran form are discussed.

Complete mapping of glomeruli based on sensory nerve branching pattern in the primary olfactory center of the cockroach Periplaneta americana

“…Similar sensory afferents have been reported in orthopteran (Ignell et al, 2001), dipteran (yellow fever mosquito, Aedes aegypti: Ignell et al, 2005) and lepidopteran insects (Pearson, 1971), including the larval moth Manduca sexta (Kent and Hildebrand, 1985), and are thought to be mechanosensory neurons (Ignell et al, 2001. Detailed observation by confocal microscopy in the cockroach, however, has shown that the sub-tract consists of several dozen thin axons and axon terminals having numerous microglomerular structures.…”

Brain Size: A Global or Induced Cost of Learning?

“…The mushroom bodies of Pieris consist of the calyx, consisting of two fused saucer-like structures located posterior and dorsal in the butterfly brain, and the anteriorly-located lobes [Nordlander and Edwards, 1968;Pearson, 1971;Ali, 1974]. These two parts are connected by a thin stalk, which can be seen in figure 1 b, but which was not included in our measurements because of its small size.…”

“…Our measurements focused on the calyces and the lobes, which were the most easily delineated parts of the mushroom body. Mushroom body lobes have several parts in the Lepidoptera [e.g., alpha, beta, gamma; Pearson, 1971;Ali, 1974], but are not easy to discriminate, thus we measured the lobes together.…”

Development of cricket mushroom bodies

“…Recently, Schü rmann et al (2000) described differences in the glutamatelike immunoreactivity in subpopulations of cricket Kenyon cells. The structure of the lobes also reflects Kenyon cell heterogeneity in different insect species (Goll, 1967;Pearson, 1971;Schä fer et al, 1988;Schü rmann and Erber, 1990;Bicker, 1991;Elphick et al, 1995;Brotz et al, 1997;Strambi et al, 1998;Strausfeld and Li, 1999;Strausfeld et al, 2000;Farris and Strausfeld, 2001;Sinakevitch et al, 2001). However, extensive studies demonstrating the development of the laminar organization in mushroom bodies are still rare.…”