Developmental Changes in Hemocyanin Expression in the Dungeness Crab, Cancer magister

The copper-based respiratory protein hemocyanin undergoes a developmental shift in subunit composition and function analogous to that seen in many hemoglobins. We studied hemocyanin gene expression in the Dungeness crab (Cancer magister) by Northern blot analysis. Animals were raised under controlled conditions, and total RNA was isolated from 13 developmental stages as well as from six tissue types in the adult animal. RNA was run on formaldehyde-agarose gels, blotted onto nylon membranes, and probed with 32P-labeled cDNA probes specific for C. magister adult hemocyanin. Results indicate that adult hemocyanin biosynthesis occurs in hepatopancreas tissue only. Analysis of developmental stages shows that expression of adult-type hemocyanin, as indicated by the appearance of hemocyanin subunit 6 mRNA, begins during the sixth juvenile instar.