The development of the ventral papillae of Notocotylus triserialis (Digenea: Notocotylidae).

The development of the ventral papillae of Notocotylus triserialis was studied by light and electron microscopy. The median row papillae first appeared on 2-day-old worms and the lateral rows on 4-day-old worms. The papillae grew in size and in number and size of constituent cells, with rapid development occurring between days 5 and 8. This rapid growth corresponded with the time of onset of egg production by the worm. Electron microscopy indicated that the papillae of 3- and 4-day-old worms contained numerous undifferentiated cells with little cytoplasm and extensive Golgi bodies. By days 5 and 6 most of these cells contained developing mitochondria; only a few undifferentiated cells were visible. Muscles and nervous tissue also became more prominent at this time. The ultrastructure of the papillae of 7- and 8-day-old worms was similar to that of papillae from adult worms. After day 9 or 10, the size and number of cells per papilla remained constant until the death of the worm.