Digestive System of Invertebrates


Digestion by invertebrates is nominally in two phases: extracellular breakdown of food followed by intracellular digestion; protist invertebrates digest foodstuffs by intracellular means. Invertebrate digestion differs from that of vertebrates in that the former lacks digestive glands opening into the hindgut.

Keywords: invertebrate digestion; symbionts; guts; fluid feeders; microphagous digestion; contact digestion; lysosomal digestion; regulation of digestion; intracellular digestion; extracellular digestion; invertebrate nutrition; symbiosis

Figure 1.

The basic invertebrate gut.

Figure 2.

Secretory cells of the primary ducts of the digestive diverticula of Tridacna gigas. MAS, microapocrine secretion of digestive enzymes.

Figure 3.

Tubule of the digestive diverticula of Tridacna gigas illustrating the digestive cells (top) in various phases of intracellular digestion, and holocrine secretion of excretory spherules. Compound flagella of crypt cells eject excretory spherules from tubule lumen towards the primary ducts, and into stomach. TB, blind‐ended digestive tubule; SD, secondary duct of the digestive diverticula; PD, primary duct of the digestive diverticula.


Further Reading

Barnes RD (1994) Invertebrate Zoology. Philadelphia: Saunders College.

Best EMH and Wells MJ (1983) The control of digestion in Octopus– I: the anticipatory response and the effects of severing the nerves to the gut. Vie et Milieu 33(3/4): 135–142.

Boucaud‐Camou E and Boucher‐Rodari R (1983) Feeding and digestion in Bivalvia. In: Saleuddin A and Wilbur KM (eds) Physiology of Mollusca, vol. 5 Part 2, pp. 149–187. New York: Academic Press.

Brusca RC and Brusca GJ (1990) Invertebrates. Sunderland, MA: Sinauer.

Bumann D and Kuzirian A (1996) Direct observation of contact digestion in inside‐out oriented Aurelia auritapolyps. Biological Bulletin 191: 302–303.

Chapman RF (1995) Mechanics of food handling by chewing insects. In: Chapman RF and de Boer G (eds) Regulatory Mechanisms in Insect Feeding, pp. 3–31. New York: Chapman and Hall.

Eckert R, Randall D and Augustine G (1988) Animal Physiology – Mechanisms and Adaptations. New York: WH Freeman.

Fankboner PV (1971) Intracellular digestion of symbiotic zooxanthellae by host amoebocytes in giant clams (Bivalvia: Tridacnidae), with a note on the role of the hypertrophied siphonal epidermis. Biological Bulletin 141: 222–234.

Fankboner PV and Cameron JL (1985) Seasonal atrophy of the visceral organs in a sea cucumber. Canadian Journal of Zoology 63: 2888–2892.

Fok AK and Allen RD (1990) The phagosome–lysosome membrane system and its regulation in Paramecium. International Review of Cytology 123: 61–94.

Morton B (1983) Feeding and digestion in Bivalvia. In: Saleuddin A and Wilbur KM (eds) Physiology of Mollusca, vol. 5 Part 2, pp. 65–147. New York: Academic Press.

Morton JE (1967) Guts – The Form and Function of the Digestive System. The Institute of Biology's Studies in Biology no. 7. London: Edward Arnold.

Nalepa CA (1994) Nourishment and the origin of termite eusociality. In: Hunt JH and Nalepa CA (eds) Nourishment and Evolution in Insect Societies, pp. 57–104. San Francisco: Westview Press.

Nicol JAC (1967) The Biology of Marine Animals. London: Pitman.

Owen G (1966) Digestion. In: Wilbur KM and Yonge CM (eds) Physiology of Mollusca, vol. II, pp. 53–96. New York and London: Academic Press.

Pearse V, Pearse J, Buchsbaum M and Buchsbaum R (1987) Living Invertebrates. Pacific Grove: Boxwood Press.

Pequignat E (1966) ‘Skin digestion’ and epidermal absorption in irregular and regular urchins and their probable relationship to the outflow of spherule‐coelomocytes. Nature, London 210: 397–399.

Schmidt‐Nielsen K (1997) Animal Physiology – Adaptation and Environment. Cambridge: Cambridge University Press.

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How to Cite close
Fankboner, Peter V(May 2003) Digestive System of Invertebrates. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0003645]