Natural History
 
 

General Structure of Anenomes

• Simple tubular tentacles arranged in one or more ringlets around the oral disk.
• Radial symmetry around oral-aboral axis
• Tissue level organization
• Germ layers-Ectoderm, endoderm and mesodermal layers
• Gastrovascular cavity-single opening for both mouth and anus
• Body wall is made of epidermis and gastrodermis in between is the mesoglea (gelatinous matrix) made of connective tissue and muscle fibers.
• Tentacles around oral disk to aid in food capture
• Simplest Animal to have nerve cells arranged in a nerve net (has no central nervous system).
• Pedal disk at base to attach to rocks or hard substrate
• Simplest Animal to have sense organs
• Statocysts: Organs for equilibrium
• Ocelli: Photosensative organs
• Move by muscular contractions
• Planula larva
• No excretory system
• No coelomic cavity
• Ciliated grooves on oral disk allow water currents to enter, cilia throughout increase the flow to create hydrostatic skeleton to support the anenome
• When disturbed the anenome contracts and withdraws the tentacles and oral disk
• Can reproduce sexually or asexually by pedal lacerations
• Eats dislodged mussels, crabs, sea urchins, fish, and other organisms that contact the tentacles of the anenome.  Have access only to prey that swim or fall in contact with the tentacles.

Picture taken from Kozloff, Eugene (see works cited)

Special Adaptations

• Nematocysts:  a small capsule made of material similar to chitin that contains a tiny coiled tubular filament.  The filament is an extension of the capsule. The end of the capsule is covered by a lid called the operculum.  The capsule shoot the filament to inject prey with a paralyzing toxin.  This tiny weapon bursts at a velocity of 2 meter/sec and 40,000 x gravity. The prey can be stung by hundreds to thousands of nematocysts at at time.  Once they have

• Mechanoreceptors: organs that become sensatized to the vibration of its prey, so that upon tactile stimulation the nematocysts are discharged. The tentacles bend and close.  Certain chemicals also induce the tentacles to bend and for swallowing to occur.

Species Specific Special Adaptations

• Anthopleura xanthogrammica lies in the low intertidal pools and depend on food such as mussels that fall from above.  Seastars are especially important in providing this food because when they open mussesl to digest them pieces of the mussel fall.

 
• Anthopleura elegantissima is often found with shell fragments attached to outside of tentacles to protect from:
• Dessication
• Ultra violet sunlight
• Spawns in mid-June
• Displays a defense mechanism for its communal territory. It has immunological recognition of genetically related individuals.  If the anenome comes in contact with another anenome which is not derived from the same colonizing larva the anenome shows aggresion towards the intruder anenome by raising its tentacles and exposing its acrorhagi which serve to sting the other anenome.   (Lisbeth Francis, 1973)

Picture taken from Kozloff, Eugene (see works cited)
• Anthopleura sola
• Tends to live in relatively sheltered positions and moderate climes.  Quiet pools, rock pockets or crevices
• May also be found with shell fragments
•  Easily detached becuase is only attached by a slender projection from pedal disk
• Predators are certain species of sea stars and nudibranchs
• Because it is larger it can reach farther in depth in comparison to A. elegantissima
• Spawns in mide June
• Has "sunburst design" on oral disk