Final answer:
Sequestering the germline ensures genetic consistency across generations. Drosophila employs a preformation strategy for germline specification via predetermined pole cells from a germ plasm, while C. elegans uses an epigenesis strategy, specifying germline cells through cellular interactions later in development.
Step-by-step explanation:
The rationale for sequestering the germline stems from the need to maintain the integrity and consistency of genetic information passed on to future generations. In organisms, two main strategies of germline specification are observed: preformation, where germ cells are specified early in development, and epigenesis, where germ cells are specified later through inductive signals from surrounding tissues.
In Drosophila, germline specification is an example of preformation. Germ cells are formed from a distinct set of cells known as the pole cells, which are determined by the germ plasm located at the posterior pole of the egg. This germ plasm contains determinants that are essential for the development of the germline and are physically segregated from the start.
Conversely, in C. elegans, germline specification follows the epigenesis mode. Germ cells are not predetermined by a localized germ plasm but are instead specified by inductive interactions during various stages of development. Their fate is not fixed until a particular set of cells (Z2 and Z3) receive signals from surrounding somatic gonad cells. This system demonstrates how crucial cellular interactions are for germline specification in C. elegans.
The main difference between the two lies in the initial establishment of their germline cells, which is preformed in Drosophila via the germ plasm, and induced in C. elegans through cell interactions.