Phyla Cnidaria and Ctenophora, Basic Animal Development ...

Phyla Cnidaria and Ctenophora, Basic Animal Development &
Introduction to Nervous Systems 5.12
Lab #5 - Biological Sciences 102 – Animal Biology
Discharge of nematocysts involves the following events:
1. molecules released from prey may sensitize the cnidocytes, but tactile stimulation causes
the nematocysts to discharge
2. discharge is due to tensional forces created by a very high osmotic pressure within the
nematocyst
3. when triggered the high osmotic pressure causes water to rush in to the capsule.
3. the build of water (increased hydrostatic pressure) forces the filament out and it turns
inside out at the same time
4. the barbs are then exposed and, if present, poison is injected into the prey
Nematocysts of most cnidarians are not harmful to humans, but the stings of Physalia and
some true jellies are painful and can be dangerous – particularly if the individual is allergic to
the organic poison.
The instructor will remove the tip of a tentacle from Corynactis californica or similar species
and prepare a slide by squashing the tip under a cover slip.
Label the undischarged and sketch a discharged nematocyst below.
UNDISCHARGED NEMATOCYST DISCHARGED NEMATOCYST
Subclass Ceriantipatharia
Order Ceriantharia (tube anemones)
Observe the specimens and/or diagrams of the following species.
Record the descriptive information requested at the end of the lab for these species.
The available ceriantharian such as Pachycerianthus fimbriatus
Subclass Octocorallia
Under a dissecting scope, observe the polyp morphology of Lophogorgia chilensis or Renilla
kollikeri to identify the unique features of an octocorallian polyp.
Record the descriptive information requested at the end of the lab for these species.