Abstract
BackgroundMany insects can regenerate limbs, but less is known about the regrowth process with regard to limb injury type. As part of our neurophysiology education experiments involving the removal of a cockroach leg, 1) the ability of Blaberus discoidalis cockroaches to regenerate a metathoracic leg was examined following autotomy at the femur/trochanter joint versus severance via a transverse coxa-cut, and 2) the neurophysiology of the detached legs with regard to leg removal type was studied by measuring spike firing rate and microstimulation movement thresholds.Leg Regrowth ResultsFirst appearance of leg regrowth was after 5 weeks in the autotomy group and 12 weeks in the coxa-cut group. Moreover, regenerated legs in the autotomy group were 72% of full size on first appearance, significantly larger (p<0.05) than coxa-cut legs (29% of full size at first appearance). Regenerated legs in both groups grew in size with each subsequent molt; the autotomy-removed legs grew to full size within 18 weeks, whereas coxa-cut legs took longer than 28 weeks to regrow. Removal of the metathoracic leg in both conditions did not have an effect on mortality compared to matched controls with unmolested legs.Neurophysiology ResultsAutotomy-removed legs had lower spontaneous firing rates, similar marked increased firing rates upon tactile manipulation of tibial barbs, and a 10% higher electrical microstimulation threshold for movement.SummaryIt is recommended that neurophysiology experiments on cockroach legs remove the limb at autotomy joints instead of coxa cuts, as the leg regenerates significantly faster when autotomized and does not detract from the neurophysiology educational content.
Highlights
Our research group studies insect neurophysiology for educational applications, where typical experiments involve cutting the leg off of a cockroach through a transverse coxa-cut, inserting electrodes into the coxa and tibia/tarsus joint, and monitoring the neural activity over a number of hours in the still-living detached leg [1,2,3]
As part of our neurophysiology education experiments involving the removal of a cockroach leg, 1) the ability of Blaberus discoidalis cockroaches to regenerate a metathoracic leg was examined following autotomy at the femur/trochanter joint versus severance via a transverse coxa-cut, and 2) the neurophysiology of the detached legs with regard to leg removal type was studied by measuring spike firing rate and microstimulation movement thresholds
Regenerated legs in the autotomy group were 72% of full size on first appearance, significantly larger (p
Summary
Our research group studies insect neurophysiology for educational applications, where typical experiments involve cutting the leg off of a cockroach through a transverse coxa-cut, inserting electrodes into the coxa and tibia/tarsus joint, and monitoring the neural activity over a number of hours in the still-living detached leg [1,2,3]. Invertebrates are famous for their regenerative abilities, notable examples including the sea star and the planarian. This is no different for insects, with many using leg autotomy as a defense mechanism against predators [4]. As part of our neurophysiology education experiments involving the removal of a cockroach leg, 1) the ability of Blaberus discoidalis cockroaches to regenerate a metathoracic leg was examined following autotomy at the femur/trochanter joint versus severance via a transverse coxa-cut, and 2) the neurophysiology of the detached legs with regard to leg removal type was studied by measuring spike firing rate and microstimulation movement thresholds
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