Opaline gland ultrastructure in Aplysia californica (Gastropoda: Anaspidea)

Jeffrey S. Prince

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Secretions released from the ink and opaline glands of Aplysia californica protect this shell-less mollusc from predators in several ways; the most recently discovered, phagomimicry, stimulates the feeding behaviours of the predator, distracting it from the sea hare. The structure of the ink gland has been reported, but little is known about the opaline gland. This paper compares the structure of the opaline gland of A. californica with that of its ink gland, as well as two additional vesicle types found in the epidermis. The opaline gland consists of single large cells, the vesicle cells, each with an enlarged nucleus, the maximum size of both exceeding that of respective structures in the ink gland. Opaline vesicles, like ink vesicles, are enclosed by an external layer of muscle. Opaline vesicles, unlike ink vesicles, are not immersed in additional cells, but are free within the haemolymph and are, therefore, the probable site for the synthesis of their protein contents. The necks of individual opaline vesicles are fused into a central canal, but short necks connecting each vesicle to the central canal remain; these are filled with epithelial cells, but lack a muscular release valve like that in the long necks of ink vesicles. Mucous cells contain circular arrays and are structurally distinct from opaline vesicles; mucous cells, though enlarged, are smaller than opaline or ink vesicle cells; they lack an external layer of muscle and a multicellular neck and, therefore, more closely match another vesicle type in the skin of A. californica, the white vesicle, which is involved with excess calcium excretion.

Original languageEnglish (US)
Pages (from-to)199-204
Number of pages6
JournalJournal of Molluscan Studies
Issue number2
StatePublished - May 2007

ASJC Scopus subject areas

  • Aquatic Science
  • Animal Science and Zoology


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