Coracidium

The egg is essentially the only developmental stage (except a coracidium in certain orders) which is exposed to the external environment. A number of morphological and physiological adaptations allow the egg to survive in this hazardous environment - and at the same time respond sensitively to those stimuli which enable it to hatch in the appropriate place in the appropriate host. 

Fig. 8.1. Scanning electron micrograph of a coracidium of Bothriocephalus acheilognathi 5 h after hatching. The coracidium has swollen as a result of water absorption and the cilia are coiled and non-functional. The surface is covered by numerous protruberances of unknown function. Scale bar = 4.9 (iin. (After Pool, 1984.)...

Fig. 8.3. Bothriocephalus acheilognathi effect of temperature on infectivity (i.e. the period a coracidium remains infective) and longevity. (After Pool, 1985.)...

THE CORACIDIUM/PROCERCOID TRANSFORMATION The ultrastructural changes which take place during the coracidium/ procercoid transformation have been studied largely in the Pseudo-phyllidea 265, 461, 485), but some limited data are available for the... 

A major morphological change which occurs during the coracidium/procercoid transformation is the elongation of the body and the separation of the hooks into a distinct appendage, the cercomer. The nature of this structure and especially its... 

Guttowa, A. Moczon, T. (1974). Oxidoreductase histochemistry in larval stages of pseudophyllidean cestodes. I. Coracidium. Acta Parasitologica Polonica, 22 1-7. 

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