Figure 1. — Posterior view of king crab showing arrangement of carapace and 

 abdominal segments. (After Marukawa, 1933*) 1> posterior 

 border of carapace; 2, isthmus between carapace and body; 3> 

 first abdominal segment; 4-6, second abdominal segments; me- 

 median plate, la- lateral plate, ma- marginal plate. 



carapace and abdomen). The carapace and 

 abdominal segments then started to part, 

 thus tearing the membrane further and 

 opening a large gap. The tear in the 

 membrane extended completely along the 

 anterior margin of the abdominal segments, 

 vertically up the isthmus between the 

 carapace and body, and completely across 

 the posterior margin of the carapace. As 

 the membrane continued to tear, the open- 

 ing grew larger and the soft-shelled crab 

 backed out of the old shell. During the 

 only occasion when a crab was timed cast- 

 ing its shell, four minutes were required 

 to back out of the old shell. 



Many females examined during trawl- 

 ing operations were found with the membrane 

 along the first abdominal segment split 

 and this section open. 



POSTMOLTING OBSERVATIONS 



Seven of the nine cast shells re- 

 mained intact. The membranes connecting 

 the sides of the carapace to the body 

 shell did not separate (fig. 2), except 

 for the section between the carapace and 

 abdominal segments. In the other two, 

 the thin membranes in other parts of the 

 cast shells were torn and parts lost. 



The outer layers of the antennae, 

 eyes, gills, stomach, and mouth parts were 

 entirely left with the old shells; the 

 tendons of the legs were also left in the 

 cast shells. One specimen sloughed off 

 its left fourth leg at the basal segment 

 and left it in the cast shell. This crab 

 would probably regenerate a new leg. 



