Granular Chitin in the Epidermis of Nudibranch Molluscs

Abstract

Chitin is usually found in stiff extracellular coatings typified by the arthropod exoskeleton, and is not associated with the soft, flexible mollusc skin. Here, we show, however, that chitin in nudibranch gastropods (Opisthobranchia, Mollusca) occurs as intracellular granules that fill the epidermal cells of the skin and the epithelial cells of the stomach. In response to nematocysts fired by tentacles of prey Cnidaria, the epidermal cells of eolid nudibranchs (Aeolidacea) release masses of chitin granules, which then form aggregates with the nematocyst tubules, having the effect of insulating the animal from the deleterious action of the Cnidaria tentacles. Granular chitin, while protecting the animal, does not interfere with the suppleness and flexibility of the skin, in contrast to the stiffness of chitin armor. The specialized epidermis enables nudibranchs to live with and feed on Cnidaria.

Characterization of Organics Consistent with β-Chitin Preserved in the Late Eocene Cuttlefish Mississaepia mississippiensis

“…Because chitin antibodies and IHC have been used to successfully detect chitin in extant organisms [18], [19], IHC (Text S1) was used here to further elucidate the specific nature of biomolecules found in M . mississippiensis .…”

Three-dimensional chitin-based scaffolds from Verongida sponges (Demospongiae: Porifera). Part I. Isolation and identification of chitin

“…In some cases, there is a diversity of chitin aggregation within one and the same organism. For example, chitin appears in three different organs in shell-free eolid nudibranchs (Mollusca): (1) in the radular teeth; (2) in cuticles of the head alimentary tract; and (3) as intracellular granules in the epidermal cells of the skin and the gut epithelium, known as the spindles [41]. Despite the structural similarity at the nanoand microlevel between the chitin of sponges and that of other invertebrates, the pathways of the chitin biosynthesis as well as the principles of the chitin nano-and microfibril assembly in sponges are unknown yet.…”

Acquisition and use of nematocysts by cnidarian predators

“…For example, behaviors that limit contact with the prey (Grosvenor, 1903; Todd, 1981) could protect the nudibranch predator from nematocyst discharge. In addition, cuticular gut linings (Edmunds, 1966; Martin et al, 2007a), protective epithelia (Graham, 1938; Martin and Walther, 2003; Martin et al, 2007b), and mucus secretions (Mauch and Elliot, 1997; Greenwood et al, 2004) all serve to protect nudibranchs while feeding.…”