Nurse cell-oocyte interaction in the telotrophic ovary

The ultrastructural, immunocytochemical and electrophysiological aspects of the telotrophic ovariole are reviewed, using Rhodnius prolixus as the example. During embryonic development, multiple germ cells become established within each of the 7 ovarioles per ovary. The structural and functional polarity develops during post-embryonic development, resulting in the cytoskeletal-rich adult ovariole. Attention is focused on the cytoskeletal aspects, including microtubules, molecular motors and actin organization. Extracellular electric currents have been mapped using a 2-D vibrating probe. Experiments combining vibrating probe measurements with ion substitutions, channel blockers and inhibitors reveal that sodium and calcium ions are of particular importance. Sodium plays a role in the endocytic pathway essential to vitellogenesis. Calcium appears important to the currents around the tropharium and especially to transient currents at the apical area of the T oocyte. These appear to be associated with closure of the trophic cord. Currents around the T-1 oocyte reverse when the T oocyte loses connection to the tropharium, suggesting the currents may play a significant role in intra-ovariole regulation. Negatively charged and neutral microinjected beads are transported from the tropharium to the oocytes. The value of the telotrophic system to further study cytoplasmic transport and oogenesis is highlighted.