Physiology

Abstract

Effective invasion mechanism aids different worms of parasitic nature to set foot in their host body. Different identifying machineries indicate adaptive features to specific environmental situation of invasion. Active locomotion and movement towards the intermediate or definitive host is achieved by several larval helminth parasites. Active penetration through the epidermal covering of host body helps many parasites to acquire entry to the hosts. Secretion from the anterior glands of apical part of body of the digenean miracidium larva assists to penetrate to their suitable snail host. After noticing and entering into an appropriate host organism, the parasitic individual is to establish itself in a fitted niche for growth, sexual maturity or to attain intermediate stage, such as another larva, which develops in the succeeding host. A period of arrested development or hypobiosis is an adaptive mechanism to cope up with unfavourable environment. Many parasites have complex life history that involves sexual reproduction in one host whereas asexual growth in another. This chapter also deals with the different varieties of sensory organs and neurotransmitters of nematodes in detail.