Neodermata

• From Greek ‘neos’, new + derma, skin
• Syncytium a continuous layer of fused cells
• Tegument provides protection against a host’s enzymes and immune system
• Class Trematoda

  (Greek trematodes, perforated form)

  • Also known as flukes, which describes their flat, leaf-like shape.

  • Almost all adult flukes are parasites of vertebrates.
• Subclasses of Trematoda

  • Aspidogastrea endoparasites of molluscs, fish or turtle.

  • Digenea medically important parasitic species.

  Monoecious, life cycles are complex and varied involving at least two and often three host
• Definitive host harbors sexually reproducing parasite

  Intermediate host harbors developmental stage of parasite
• Miracidium the ciliated, free-swimming, first-stage larva of a digenean trematode that undergoes further development in the body of a snai
• Sporocysts an asexual stage of development in some digenean trematodes that arises from a miracidium and gives rise to rediae.
• Redia a larval, digenetic trematode produced by asexual reproduction within a miracidium, sporocyst, or mother redia
• Cercaria juvenile digenetic trematode produced by asexual reproduction within a sporocyst or redia. Cercariae are free swimming and have a digestive tract, suckers, and a tail. They develop into metacercariae.
• Metacercaria stage between the cercaria and adult in the life cycle of most digenetic trematodes. Usually encysted and quiescent.
• Class Monogenea

  • Monogetic flukes one generation in their life cycle

  • Mostly external parasites (ectoparasites) of freshwater and marine fish.

  • Opisthapor – a large, posterior organ, facilitates attachment to gills.

  • Oncomiracidium – a ciliated larva hatches from the egg and swims to another host fish, eventually develops into adult
• Class Cestoda

  From Greek kestos’, girdle From Greek kestos’, girdle

  • Tapeworms are endoparasites.

  • Lack a mouth and digestive tract.

  • Most consist of a series of repeating units called proglottids
• Subclass Eucestoda

  • Scolex located at one end and a holdfast structure, it contains circular leaflike suckers called rostellum

  . • Transverse constrictions in the scolex give rise to the third body region called strobila

  • Outer body wall is composed of tegument

  • Monoecious – each proglottids has one or two complete sets of reproductive structures
• Oncosphere The larva of the tapeworm contained within the external embryonic envelope and armed with six hooks and cilia. Typically referred to as a coracidium when released into the water
• Cysticercus Metacestode developing from the oncosphere. Usually has a tail and a well-formed scolex and is characterized by a fluid-filled oval body with an invaginated scolex.
• Coracidia Larva with a ciliated epithelium hatching from the egg of certain cestodes. A ciliated, free swimming oncosphere
• Procercoid larvae Cestode developing from a coracidium in some orders. It usually has a posterior cercomer. Developmental stage between oncosphere and plerocercoid
• Plerocercoid larvae Metacestode that develops from a procercoid larva. It usually shows little differentiation.