title for learn-about sections for chitons in A SNAIL'S ODYSSEY
  Symbionts
 
Research study 1
 

photograph of gumboot chiton Cryptochiton stelleriA distinctive feature of gumboot chitons Cryptochiton stelleri is that their dorsal surfaces are generally free of epibiotic growths. Those growths that are present usually owe to wounds being colonised by algae or barnacles.  Based on a study done at Friday Harbor Laboratories, Washington, the explanation seems to lie in the dorsal surface being comprised of many tufts of fine spicules of calcium carbonate. The spicules originate from bulbous structures in the skin and protrude through small openings in the form of flattened rosettes. The authors speculate that protection is conferred in 2 ways.  First, the rosette shapes of the spicules may physically prevent algal spores, larvae, and other small animals from settling and taking up residence. Second, the spicule tufts appear to hold a protective layer of mucus in place.  If fine planktonic matter is placed on the dorsal surface, mucous glands in the skin secrete a photograph of close view of skin structure in a gumboot chiton Cryptochiton stelleri1-2mm thick layer that is held in place by the rosettes.  When the mucous layer disintegrates, it washes away and carries entrapped organic material with it.  MacGinitie & MacGinitie 1968 Veliger 11: 59.


Closer view ofspicule tufts
on dorsal surface 3X

 
Research study 2
 

Examination of gumboot chitons Cryptochiton stelleri in the Monterey Peninsula, California discloses 2 common symbionts inhabiting the pallial grooves.  The polynoid polychaete Arctonoe vittata lives in the front part of a groove, facing into the respiratory stream, while the pea crab Opisthopus transversus lives anywhere in the pallial groove, generally facing towards the midline of the host’s body.  Incidence of occurrence of the 2 species on chitons collected in October-December is 22-60% for Arctonoe and 20-40% for Opisthopus. An individual chiton may host 2-3 pea crabs, but never photograph of gumboot chiton with a commensal scaleworm in its pallia groove Arctonoe vittatamore than a single worm.  Often both types of symbionts live on an individual chiton.  Benefits for the symbionts include protection from wave surge, predators, drying and, because Arctonoe is known to eat detritus, possibly provision of food in the respiratory stream.  Simple Y-tube tests in the laboratory show a strong and significant attraction of the worm to a host for both species (Arctonoe: 34:6 for host-containing vs. empty arm of the Y-tube; Opisthopus: 33:11), suggesting the presence of a diffusible chemical attractant for both symbionts.  Webster 1968 Veliger 11: 121.

NOTE if more than one worm is present, do they fight?


When this gumboot chiton Cryptochiton
stelleri
was overturned by a SCUBA diver,
its commensal worm Arctonoe vittata
emerged from the chiton's pallial groove 0.7X

 
  RETURN TO TOP