Cestoda or Cestoidea

[Xylander]

Hi Mike,

Ehlers (1985, Das Phylogenetische System der Plathelminthen, Fischer Verlag,
Stuttgart) used "Cestoda" for all tapeworms including the monozoic taxa (!)
(Gyrocotylidea, Caryophyllidea and Amphilinidea) which together share a high
number of autapomorphies with the "Cestoidea", e. g.:
* all stages without an intestine
* epidermis of larvae syncytial
* 10 larval hooks
* anterior pit developed in the first intermediate host
* 2-host-life-cylcle
* first canal cell of the protonephridia without a cell gap and desmosome
* protonephridial system of mature stages reticulate
* cellbodies of nephrioducts located underneath the surrounding basal lamina
* neodermis with regularly shaped microvilli with a small electron dense cap
* occurrence of calcareous corpuscles
* large body dimensions

Ehlers (l. c.) named those taxa "Cestoidea" which have the following
autapomorphies (see Xylander 2000 and some older papers for reference):
* six hooked larva
* larva without a cerebrum and sensory structures
* these larva do not infect their hosts actively but have to be eaten ("passive
larva")
* numbers of terminal organs of protonephridia and glands reduced in the larva
* neodermis with microvilli with a large electron dense tip (microtriches)
* cercomer (hook-bearing part of the body) is shed after infection of the
definitve host
* spermatozoa without mitochondria
* attachment of postlarval stages with the anterior body end

So to answer your question in short: The Cestoidea are a subtaxon of the
Cestoda.

Best wishes

Willi Xylander

Michael Balsai schrieb:
> Can someone tell me which is correct? Cestoda or Cestoidea, and if the
> latter why?
>
> Mike Balsai