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Title: A study of autotomy in decapod crustacea
Author: Findlay, Ian
ISNI:       0000 0001 3465 027X
Awarding Body: University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1977
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Autotomy is the process whereby an animal can discard a part of its body from a preformed breakage plane. This study examines the natural occurrence of limb autotomy in the crab Carcinus maenas in the Yealm estuary, Devon; and the nervous control of limb autotomy in the hermit crab Pagurus bernhardus and the shore crab Carcinus maenas. Of the crabs caught in the Yealm estuary in monthly samples between February 1976 and January 1977, 13.2% had lost one or more limbs, with males showing a greater incidence of autotomy (14.5%) than females (12.2%). There is a significant positive relationship between crab's size and incidence of autotomy and seasonal changes in the incidence of autotomy can be explained in terms of alterations of the mean size of crabs caught in each monthly sample. Limb autotomy in Pagurus and Carcinus results from limb injury and coactivation of the two BI levator muscles. The smaller posterior levator muscle (PL) rotates to direct isometric force from the large anterior levator muscle (AL) onto a plug in the breakage plane which encircles the BI and cause autotomy. During normal locomotion, although the PL muscle is electrically active it's tendon does not rotate and AL force is directed away from the plug in the breakage plane. The nervous control of limb autotomy is a combination of injury induced central command and feedback from a peripheral sense organ. Injury causes high frequency excitation of AL motor neurones and inhibition of PL motor neurones. The PL muscle rotates, as during autotomy, when the sense organ CSD1 is stimulated by strong isometric contractions of the AL muscle. This investigation shows that PL rotation at autotomy results from such stimulation of CSD1 and not central nervous command. Accidental autotomy in inappropriate circumstances is prevented when CSD 1 inhibits AL contraction, inhibition which is avoided by injury induced excitation of AL motor neurones to cause autotomy.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Physiology