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Phylum Nematomorpha

Phylum Nematomorpha. By Sheryl Francisco. Likely related to the nematodes Known as the “horsehair worms” Can grow to be 1 m long but only a few mm wide Roughly 325 described species known so far (world wide) Divided into two classes:

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Phylum Nematomorpha

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  1. Phylum Nematomorpha By Sheryl Francisco

  2. Likely related to the nematodes • Known as the “horsehair worms” • Can grow to be 1 m long but only a few mm wide • Roughly 325 described species known so far (world wide) • Divided into two classes: • Class Nectonematoda: the only members are in the genus Nectonema. Are the only known marine species of nematomorphs. Parasitize crustaceans. • Class Gordioda: Consists of the rest of the fresh water and semi-terrestrial species. Parasitize arthropods.

  3. Nematomorph Larvae Biology of the Invertebrates, 4th edition p. 431

  4. Adult Worm www.inhs.uiuc.edu/chf/pub/surveyreports/mar-apr95/page4.html

  5. Life Cycle • Female releases long string of eggs into the water (1+ million eggs). • Larvae hatch after 15-80 days. • Come into contact with either an appropriate host or a transport host. Enters the host either by ingestion or penetration. • Begins developing if in the appropriate host. Encysts if in a transport host until it is in an appropriate one (possibly 1+ years if needed). • Enters into the digestive tract and feeds off of nutrients attained by the host. • 4-20 weeks later the juvenile has developed into an adult.

  6. Life Cycle (cont.) • Once the host is in an aquatic environment, the adult nematomorph breaks through the hosts body wall and kills it. • Sexual mating occurs in many species. The male and female become intertwined with their gonopores pressed together.

  7. Juvenile Facts • Larvae have a spined introvert proboscis which it can use for attachment purposes. • Posses a complete digestive tract which becomes nonfunctional in the adults. • Doesn’t grow by uetely – grows by increase in cell number. • Excretes a collagenous cuticle from the epidermis which is molted as they grow. • Takes 4-20 weeks for the larvae to fully mature to the adult stage.

  8. Adult Facts • Theorized that adult nematomorphs are able to manipulate their host to seek out water. • Once in an aqueous environment, the worm breaks through the host’s body wall, killing it in a miserable manner. • The adult lives off of the nutrients it acquired while in the host. • They live very sedentary lives and the majority of the females energy goes toward egg production. • Adults die within 2-4 weeks of leaving the host’s body.

  9. General Physiology • Only posses longitudinal muscles – can move by sinusoidal motion. • No distinct respiratory surfaces • No excretory system. • Nervous system consists of an anterior brain which surrounds the nonfunctional pharynx. • Nerve cord is connected to brain and runs down the entire length of the body. • Marine species have both a dorsal and ventral nerve cord. • All other species only have the ventral cord. • Separate sexes – males have a bilobed posterior end and females have a trilobed posterior end.

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