n All adult forms are endoparasites inhabiting the gut or gut derivative of a vertebrate.
n They have no ciliated epidermis and no alimentary canal (gut).
n The adult form is divided into segments known as proglottids.
n The anterior end, the ‘head’, is known as the scolex and has well developed adhesive
organs.
n With the exception of one family all are hermaphrodites.
n They all have a free-living stage and more than one host in their life-cycle.
n 3.4 TREMATODES (COMMONLY KNOWN AS FLUKES)
These are entirely ecto- or endo-parasites.
n No cilia on outer layer. The outer layer is known as tegument and is a living layer that
helps to absorb nutrients.
n Body is undivided and has a mouth opening into a pharynx, oesophagus and then gut
with a bilobed blind-ending diverticula (alimentary canal).
n Most species are hermaphrodites except for the Schistosomatidae.
n All have well developed adhesive organs.
n Two main orders: the Digenea and the Monogenea.
n 3.5 NEMATODES (COMMONLY KNOWN AS
ROUND WORMS)
These organisms have three body layers with a body cavity known as the pseudo-
coelome. The body cavity is fluid-filled and forms a hydrostatic skeleton.
n Cylindrical body shape, non-ciliated outer layer known as a cuticle.
n Sexes are separate; the gonads are tubular and with their ducts form a continuous
structure.
n Worldwide distribution; occupying both terrestrial and aquatic habitats.
n 3.6 NEMATOMORPHA (COMMONLY KNOWN AS
LARVIFORM WORMS)
These are non-segemented long thread-like free-living worms occurring in soil and
water.
n Sexes are separate; adults are free-living but the larvae are parasitic in arthropods.
n 3.7 ACANTHOCEPHALA (COMMONLY KNOWN AS
THE SPINY-HEADED WORMS)
These are unsegmented cylindrical worms, with a protrusible proboscis.
n No gut; pseudocoele; sexes are separate.
n Inhabit mainly the gut of vertebrates.
n 3.8 TAPEWORMS (EUCESTODA)
There are two main sub-classes of cestodes (see sections 3.8.2 and 3.8.3).
PLATYHELMINTHS