Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

Ultrastructure of Early Embryonic Shell Formation in the Opisthobranch Gastropod Aeolidia papillosa

Linda S. Eyster
Biological Bulletin
Vol. 165, No. 2 (Oct., 1983), pp. 394-408
DOI: 10.2307/1541204
Stable URL: http://www.jstor.org/stable/1541204
Page Count: 15
  • Subscribe ($19.50)
  • Cite this Item
Ultrastructure of Early Embryonic Shell Formation in the Opisthobranch Gastropod Aeolidia papillosa
Preview not available

Abstract

Early shell formation was examined in embryos of the opisthobranch gastropod Aeolidia papillosa. Secretion of the first organic shell material occurs prior to closure of the shell gland lumen, contrary to reports for other molluscan embryos. This difference suggests that in externally shelled gastropods and bivalves initiation of shell secretion may be coincident with narrowing of the shell gland pore rather than with closure of the lumen. The shell growth region was examined ultrastructurally. As no shell material is seen in the shell gland lumen, the shell gland seems not to be actively involved in shell secretion. Initial shell material is secreted only by cells surrounding the shell gland pore. Shell material seems to be added, not in a gap between cells as previously described, but over the apical surface of cells at the growing edge. The growing edge of the shell and the growing edge cells are covered by cytoplasmic extensions arising from the neighboring cells distal to the shell gland. No infoldings of the growing edge cell membranes are seen. The first organic shell material is 20 nm thick, consists of two electron dense layers seperated by an electron lucent layer, and is secreted at least 33 hours (5°C) before shell mineralization, as detected by polarizing microscopy.

Page Thumbnails

  • Thumbnail: Page 
394
    394
  • Thumbnail: Page 
395
    395
  • Thumbnail: Page 
396
    396
  • Thumbnail: Page 
397
    397
  • Thumbnail: Page 
398
    398
  • Thumbnail: Page 
399
    399
  • Thumbnail: Page 
400
    400
  • Thumbnail: Page 
401
    401
  • Thumbnail: Page 
402
    402
  • Thumbnail: Page 
403
    403
  • Thumbnail: Page 
404
    404
  • Thumbnail: Page 
405
    405
  • Thumbnail: Page 
406
    406
  • Thumbnail: Page 
407
    407
  • Thumbnail: Page 
408
    408