|Cnidosac morphology in dendronotacean and aeolidacean nudibranch molluscs: from expulsion of nematocysts to use in defense?|Martin, R.; Heß, M.; Schrödl, M.; Tomaschko, K.-H. (2009). Cnidosac morphology in dendronotacean and aeolidacean nudibranch molluscs: from expulsion of nematocysts to use in defense? Mar. Biol. (Berl.) 156(3): 261-268. hdl.handle.net/10.1007/s00227-008-1080-2
In: Marine Biology. Springer: Heidelberg; Berlin. ISSN 0025-3162, more
|Authors|| || Top |
- Martin, R.
- Heß, M.
- Schrödl, M.
- Tomaschko, K.-H.
Nudibranchs (Mollusca, Gastropoda) feeding on tentacles and polyps of Cnidaria thereby ingest both latent and discharged nematocysts (NCs) along with the food mass. In eolid nudibranchs (Opisthobranchia, Aeolidacea), many of the undischarged NCs are transported to terminal cnidosacs in their body appendages (cerata) and incorporated as kleptocnidae for defense. In the present report, the occurrence and fate of NCs in the digestive tracts of eolids is compared with hydrozoan-feeding dendronotacean nudibranchs (Opisthobranchia, Dendronotacea), which may show more basic stages in the evolution of cnidosacs. Tomographic reconstructions of the distal tips of cerata were composed from series of semithin light microscopic sections, utilizing 3D-surface rendering software. Doto acuta (Dendronotacea, Dotidae) does not have cnidosacs; transmission electron micrographs show that the NCs are digested in lysosomes of digestive gland cells. In contrast, species of the genus Hancockia (Dendronotacea, Hancockiidae) have several small cnidosacs in each ceras; they accumulate NCs in the digestive cells, as well as in the cnidosacs. Many of the cnidosacs were found open to the exterior with NCs in the process of expulsion. These and other structural details suggest assigning a function of expelling the NCs to the Hancockia spp. cnidosacs. It is proposed that cnidosacs similar to those of Hancockia spp. provide a clue to understanding how the defensive function of eolid cnidosacs may have evolved.