Complex sentence: In respect to drosophila, nurse cells are polytenic germline cells that contribute to the development of the drosophila oocyte, producing about 250-500 nuclei, all 15 of them in all oocytes creating 5000 nuclei in total.
Split into simpler sentences: In respect to invertebrates, nurse cells are polytenic germline cells that contribute to the development of the oocyte, producing multiple nuclei. For example, in fruit flies (drosophila), about 250-500 nuclei, all 15 of them in all oocytes creating 5,000 nuclei in total.