A study of the patterns of embryonic development in South African onychophorans (Peripatopsidae) - Volume 1
thesisposted on 2014-12-15, 10:33 authored by Beverley. Sherbon
The process of segment formation during embryonic development in Peripatopsis capensis Grube 1886 follows a similar pattern to that seen in other Onychophora previously examined, except for Opisthopatus cinctipes Purcell 1899. In P. capensis and all other species described, the paired lateral halves of the embryo develop as thickened bands of blastoderm. The bands differentiate paired segmental swellings, each containing a mesodermal somite, which later form the rudimentary limb buds. The body elongates by the sequential addition of segments from a posterior growth zone.;In O. cinctipes the embryo elongates without any visible internal or external boundaries. After elongation, the transitory mesodermal somites form simultaneously within each segment. This coincides with the external appearance of the rudimentary limb buds. There is no separation of the embryo halves by extra-embryonic ectoderm. The different pattern of development seen in O. cinctipes is considered to be a "long germ band" type of development, compared to the "short germ band" type of development seen in all other species of Onychophora in which development has been described. This pattern of development has evolved since the separation of Opisthopatus from Peripatopsis 30 million years ago.;Techniques used to examine the two different patterns of development exhibited by P. capensis and O. cinctipes, include SEM, light microscopy of wax and resin sections, TEM, chromosome preparations, and antibody staining.
Date of award2000-01-01
Awarding institutionUniversity of Leicester