An effect of eyestalk ablation on antennular function in the spiny lobster, Panulirus argus

1. Unilateral removal of the eyestalk (optic ganglia and medulla terminalis) in the Bermuda spiny lobster, Panulirus argus , disrupts normal initiation of feeding activity via chemo-tactile stimulation of the antennule on the side of the ablation. This deficit may be permanent for it has lasted without apparent remission for over five months and two molts. Unilateral eyestalk ablation also produces a temporary increase in antennular cleaning activity directed toward the antennule on the side of the ablation. This effect seems to last for less than 16 days. Unilateral eyestalk ablation does not appreciably disturb spontaneous antennular movements or responses to mechanical stimulation of the antennule on either side. Nor does it destroy the ability of the lobster to give differential responses to mechanical and chemo-tactile stimuli. Most lobsters recover normal sensory and motor functions in antennules that regenerate after amputation of the distal segment and sensory flagellae. In about 1/3 of the animals, however, some form of sensory or motor abnormality is evident in the regenerated antennule. These deficits are ascribed to occasional failure of regenerating neurons to reform appropriate central connections. They do not resemble the deficits following eyestalk ablation. The medulla terminalis is tentatively proposed as the portion of the nervous system critical for normal antennular function that is removed by eyestalk ablation. There seem to be similarities between the effects of eyestalk ablation in the Crustacea as described here and the effects following destruction of portions of the corpora pedunculata in insects. 1. Einseitige Entfernung des Augenstieles (optische Ganglien und Medulla terminalis) bei der Bermuda-Stachellanguste, Panulirus argus , unterbricht auf der operierten Seite den Beginn der normalen Freß-tätigkeit, die durch chemische und taktile Reizung der Antennula eingeleitet wird. Diese Störung kann irreversibel sein, denn sie überdauerte in über 5 Monaten zwei Häutungen.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47096/1/359_2004_Article_BF00340474.pd

Brain architecture in the terrestrial hermit crab Coenobita clypeatus (Anomura, Coenobitidae), a crustacean with a good aerial sense of smell

<p>Abstract</p> <p>Background</p> <p>During the evolutionary radiation of Crustacea, several lineages in this taxon convergently succeeded in meeting the physiological challenges connected to establishing a fully terrestrial life style. These physiological adaptations include the need for sensory organs of terrestrial species to function in air rather than in water. Previous behavioral and neuroethological studies have provided solid evidence that the land hermit crabs (Coenobitidae, Anomura) are a group of crustaceans that have evolved a good sense of aerial olfaction during the conquest of land. We wanted to study the central olfactory processing areas in the brains of these organisms and to that end analyzed the brain of <it>Coenobita clypeatus </it>(Herbst, 1791; Anomura, Coenobitidae), a fully terrestrial tropical hermit crab, by immunohistochemistry against synaptic proteins, serotonin, FMRFamide-related peptides, and glutamine synthetase.</p> <p>Results</p> <p>The primary olfactory centers in this species dominate the brain and are composed of many elongate olfactory glomeruli. The secondary olfactory centers that receive an input from olfactory projection neurons are almost equally large as the olfactory lobes and are organized into parallel neuropil lamellae. The architecture of the optic neuropils and those areas associated with antenna two suggest that <it>C. clypeatus </it>has visual and mechanosensory skills that are comparable to those of marine Crustacea.</p> <p>Conclusion</p> <p>In parallel to previous behavioral findings of a good sense of aerial olfaction in C. clypeatus, our results indicate that in fact their central olfactory pathway is most prominent, indicating that olfaction is a major sensory modality that these brains process. Interestingly, the secondary olfactory neuropils of insects, the mushroom bodies, also display a layered structure (vertical and medial lobes), superficially similar to the lamellae in the secondary olfactory centers of <it>C. clypeatus</it>. More detailed analyses with additional markers will be necessary to explore the question if these similarities have evolved convergently with the establishment of superb aerial olfactory abilities or if this design goes back to a shared principle in the common ancestor of Crustacea and Hexapoda.</p