The oesophageal pouches (also known as sugar glands)[1] are a pair of pouches connected to the oesophagus of all molluscs, and represent a synapomorphy of the phylum.[2]

Morphology

Usually forming a pair of lateral structures, oesophageal pouches take various forms, but usually account for a fair portion of the anterior volume of the creeping molluscs and scaphopods.[3][4][5][6][7] There is a single pouch ventral to the rear of the radula in some nudibranch sea slugs.[6] The pouches are lined with ciliated secretory cells.[8]

Function

The pouches contain digestive enzymes that break down starch and other polysaccharides,[1] and also extrude mucus.[6]

Occurrence

The features are considered ancestral to molluscs[2] and are present in monoplacophorans,[9] but have been secondarily lost in the Heterobranchia.[10] However, it is not certain that all oesophageal diverticulae are homologous.[11][12]

References

  1. ^ a b "The Distribution of Cellulases and Related Enzymes in Mollusca". Journal of Molluscan Studies. 1958. doi:10.1093/oxfordjournals.mollus.a064810.
  2. ^ a b Sturm, Charles F; Pearce, Timothy A; Valdés, Ángel (July 2006). The mollusks: a guide to their study, collection, and preservation. ISBN 978-1-58112-930-4.
  3. ^ Haszprunar, G. (1987). "Anatomy and affinities of cocculinid limpets (Mollusca, Archaeogastropoda)". Zoologica Scripta. 16 (4): 305–324. doi:10.1111/j.1463-6409.1987.tb00077.x. S2CID 222189563.
  4. ^ Haszprunar, G. (1989). "The Anatomy of Melanodrymia aurantiaca Hickman, a Coiled Archaeogastropod from the East Pacific Hydrothermal Vents (Mollusca, Gastropoda)". Acta Zoologica. 70 (3): 175–186. doi:10.1111/j.1463-6395.1989.tb01068.x.
  5. ^ Ruthensteiner, B.; Schropel, V.; Haszprunar, G. (2010). "Anatomy and affinities of Micropilina minuta Warén, 1989 (Monoplacophora: Micropilinidae)". Journal of Molluscan Studies. 76 (4): 323–332. doi:10.1093/mollus/eyq013.
  6. ^ a b c Crampton, D. M. (2010). "Functional anatomy of the buccal apparatus of Onchidoris bilamellata (Mollusca: Opisthobranchia)". The Transactions of the Zoological Society of London. 34: 45–86. doi:10.1111/j.1096-3642.1977.tb00372.x.
  7. ^ Urgorri, V.; García-Álvarez, O.; Luque, Á. (2005). "Laevipilina Cachuchensis, A New Neopilinid (Mollusca: Tryblidia) from off North Spain". Journal of Molluscan Studies. 71: 59–66. doi:10.1093/mollus/eyi008.
  8. ^ Morton, J. E. (2009). "The habits and feeding organs of Dentalium entalis" (PDF). Journal of the Marine Biological Association of the United Kingdom. 38 (2): 225–238. doi:10.1017/S0025315400006032. S2CID 86547255.
  9. ^ Ruthensteiner, B.; Schropel, V.; Haszprunar, G. (2010). "Anatomy and affinities of Micropilina minuta Warén, 1989 (Monoplacophora: Micropilinidae)". Journal of Molluscan Studies. 76 (4): 323–332. doi:10.1093/mollus/eyq013.
  10. ^ Ponder, W. F. (1991). "Marine Valvatoidean Gastropods—Implications for Early Heterobranch Phylogeny". Journal of Molluscan Studies. 57: 21–32. doi:10.1093/mollus/57.1.21.
  11. ^ Lobo-Da-Cunha, A.; Oliveira, E.; Alves, Â.; Coelho, R.; Calado, G. (2010). "Light and electron microscopic study of the anterior oesophagus of Bulla striata (Mollusca, Opisthobranchia)". Acta Zoologica. 91 (2): 125–138. doi:10.1111/j.1463-6395.2009.00392.x.
  12. ^ Mikkelsen PM (1996). "The evolutionary relationships of Cephalaspidea S.L. (Gastropoda: Opisthobranchia): A phylogenetic analysis". Malacologia. 37: 375–442.
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