REGENERATION IN A TROPICAL EARTHWORM PERIONYX EXCAVATUS E. PERR

Open Access
Publisher Website
Google Scholar
Abstract
1. P. excavatus, an earthworm occurring in large numbers in dung heaps and soil rich in decomposing organic matter in Rangoon has a regenerative capacity very much higher than any known at present from megadrilous Oligochæta with the single exception of the limnic Criodrilus lacuum Hoffm., from Europe. The rate at which regeneration is completed is rapid. 2. Posterior portions can replace the anterior segments lost if the number of metameres removed is seventeen or less. When more than seventeen segments are removed only ten to fifteen metameres were regenerated. 3. The posterior limit of head regeneration lies somewhere in the last third of the length of the worm. 4. Spermathecal apertures and female reproductive pores may develop on regenerating anterior ends. 5. Anterior pieces of twenty segments or more may regenerate tails. 6. A heteromorphic head may be regenerated at the posterior end of a very short anterior piece. 7. A heteromorphic tail may be regenerated at the anterior end of a very short tail piece. 8. A piece of twenty or more segments from the middle of the worm may regenerate at one end a tail and at the other end a head. 9. Regenerated heads may be normal, hypomeric, or hypermeric. Hypomeric and hypermeric regeneration is considered an adequate explanation of the origin of abnormalities described as anterior or posterior dislocation of the reproductive organs. 10. In collections made in various quarters of the town a high percentage of the individuals secured had been mutilated by the amputation of a head, a tail, or both. Many of the mutilated specimens were regenerating the lost parts when collected. 11. One or more pieces both anteriorly and posteriorly are very frequently autotomized after operation by posterior portions. Sometimes the whole tail portion fragments into pieces six to ten millimeters in length. Anterior ends have not been observed to autotomize. 12. A fly A. scalaris Lw. has been bred from portions of P. excavatus. Parasitism by this insect may possibly be responsible for the mutilated specimens and for the autotomy following operation.

This publication has 0 references indexed in Scilit: