Spirocysts adhesive found only in the anthozoa 3

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Unformatted text preview: lls – organic molecules from prey •  Cnidocil – “trigger”, modified cilium sensitive to touch Fig 13.4 all Not ^Cnidocytes contain nematocysts Three main types: 1.  Nematocysts – inject toxin for prey capture / defense – found in all classes of Cnidaria 2.  Spirocysts – adhesive, found only in the anthozoa 3.  Ptychocysts – used by Ceriantaria (class of anthozoa) to anchor their bodies in soft substrate (i.e. sand) Firing nematocysts After the proper stimuli… Two forces contribute to firings 1.  Tension -  structural, develop during formation 2.  Osmotic Pressure -  Large concentration gradient in the cnidocyte -  Opening operculum cause water to rush in -  é༎ water volume causes nematocyte to shoot out Fig 13.5 Cnidaria are dimorphic à༎ two morpho types Gastrovascular cavity “blind gut ” à༎medusa have manubrium Epitheliomuscular cells as most of epidermis à༎ extends parallel to tentacles à༎ Contain contractile fibrils Nerve Net à༎ diffuse nervous system à༎ part of neuromuscular system à༎ Rhopalia sense organs in some medusa Fig 13.3 Fig 13.2 Hydrozoa •  •  •  •  Most marine and colonial Both polyp and medusa forms Colonial Obelia have a more typical life cycle of hydrozoa Hydra have an atypical life cycle Tentacle Mouth Hypostome Basal Disc Hydrozoa •  Hydra have an atypical life cycle Asexual à༎ 1.  Bud appears 2.  Grows 3.  Detaches •  Most species are dioecious •  Fall Sexual Ø།  lower temperatures cause temporary gonads to grow Ø།  Tes...
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This document was uploaded on 11/15/2013.

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