OBSERVATIONS ON THE NUTRITION OF MONOGENETIC TREMATODES

¹ Department of Zoology, The University of Leeds, England

1. A comparative study has been made of the food, feeding mechanism, gut structure and digestive processes in representatives of the two sub-orders of the Trematoda Monogenea.

2. The two sub-orders differ fundamentally as regards the dominant components of the diet, the Monopisthocotylea feeding on the epidermis and associated mucoid secretions of the host while the Polyopisthocotylea feed primarily upon the host's blood. In some instances the Polyopisthocotylea supplement the diet with small amounts of host tissue and mucus.

3. The feeding mechanism in both groups consists basically of a muscular pharynx, and ingestion is the result of muscular suction, aided in some cases by histolytic secretions produced in pharyngeal or esophageal glands and used to erode the host tissues.

4. The two sub-orders differ considerably with regard to the structure of the gastrodermis, that of the Monogenea being a continuous cellular structure as in most other animals while in the Polyopisthocotylea it is a discontinuous and deciduous structure whose cells contain varying amounts of the pigment hematin.

5. Digestion in both the Monopisthocotylea and Polyopisthocotylea is effected by a combination of extra-and intracellular processes, but in the Polyopisthocotylea intracellular degradation of hemoglobin results in the accumulation within the gastrodermal cells of insoluble hematin, and the elimination of this substance results in the deciduous gastrodermis characteristic of the sub-order.