User:Jtwsaddress42/Projects/Project 4/Chapters/Chapter 4

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The innovations and challenges of the jawless vertebrates

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Pacific hagfish Myxine

The agnata represent the primitive state.

  • the development of a new adaptive immunity division of the immune system enhances innate immunity via the emergence of variable lymphocyte receptors.[1]
  • the somatic and visceral divisions of the body are only connected at the pharyngeal-hindbrain region and the sacral end.
  • for the autonomic nervous systemn, there is no sympathetic division - only, an un-myelinated division of the para-sympathetic radiating out from the pharyngeal-hindbrain complex and sacral end of the organism.
  • there are no jaws or fins, no myelin.
  • due to lack of a sympathetic fight or flight system, the primary mode of response in the face of uncertainty is catatonic freezing or "feigning death".


  1. Flajnik & Kasahara 2010.