DEVELOPMENT IN VITRO OF MESOCESTOIDES (CESTODA) FROM ONCOSPHERE TO YOUNG TETRATHYRIDIUM

Oncosperes of Mesocestoides, hatched in vitro, developed axenically to procercoid-like organisms and thence to stages resembling small tetrathyridia. Sequence of development included cercomer formation, differentiation of an anterior protrusible cone, appearance of a spiny cuticle and apical organ, loss of cercomer, and beginning of sucker formation. At 8 weeks of growth, tissues and organs present were: cuticle, subcuticular cells and muscles, excretory ducts with flame cells, calcareous corpuscles, and an apical organ apparently secretory in function. Many different cell types were present. After 8 weeks of culture (at 25 to 30 C) the largest individuals were 0.5 mm in length, and in structure and motility resembled small tetrathyridia. These were infective to and multiplied asexually in laboratory mice.