Diverticulum (mollusc)

As applied to mollusks, the New Latin term diverticulum is an anatomical feature. The term is most often encountered in the plural form as "diverticula", "hepatic diverticula", or "digestive diverticula", which are anatomical terms for organs which are visible from the outside of the body in a clade of sea slugs known as aeolid nudibranchs, marine opisthobranch gastropod molluscs.[1]

This article is about structures in seaslugs. For the medical term, see Diverticulum.
The aeolid nudibranch Flabellina lineata with enlargement of the cerata to show the coloured hepatic diverticula.

The term is also applied to mollusk anatomy in other contexts: land slugs such as Lehmannia marginata have a caecal diverticulum and there is also a diverticulum in the stomach of certain Bivalvia.

Description and functions

In the Aeolidida

Individual animals within the nudibranch clade Aeolidida have an array of long protruding structures called cerata on their dorsal surface. Located within the cerata of these nudibranchs are hepatic diverticula, which are an outgrowth of the digestive gland or hepatopancreas of the animal. The cerata are translucent, and thus the contents of the diverticula are easily visible from the outside of the animal. Because of this, an aeolid nudibranch automatically takes on the colour of whatever substrate and food source it is living on and feeding on (for example, sea anemones or hydroids). Visually the animal is camouflaged when it is on its food source. The diverticula also serve another important purpose because they pass along to the tips of the cerata any intact nematocysts that have been ingested from the food source. These stinging cells then serve to defend the nudibranch against predation.[2][3]

gollark: Ah, so they're just magicking it and it's not a problem according to you, I ße.
gollark: Computing those significantly in advance probably requires computing basically the entire state of the world, while as a person who presumably actually exists in said world you can just look them up.
gollark: You can annoy the predictor and make them need more CPU time by basing your prediction on facts like "what is the least significant bit of the latest block on the bitcoin blockchain" and "what is the value of [SOME STOCK MARKET PARAMETER]", depending on how early they fill the boxoids.
gollark: Regardless of what choice you make, the contents of the boxes are fixed, thus pick mildly more money. This probably sounds unsmart to you, which is either because you (and the server generally) are/is right, or because you fell into one side and now think it's obvious.
gollark: As I said, in general apparently both sides are split pretty evenly, have fairly convincing arguments each way, and both think that their answer is obvious and the other is wrong.

References
  1. Nudibranch.com.au website, Nudibranch Glossary, Definitions of terms relating to Opisthobranchs, Accessed 2014-9-6
  2. The Cephalopod page.org, Marine Invertebrates of Bermuda, Neapolitan Spurilla (Spurilla neopolitana) by Shaunte Henry, and James B. Wood and Abel Valdiia (Eds), Accessed 2014-9-6
  3. principles and Applications of Electron Microscopy, An Ultrastructural Study on the Transportation and Intracellular Incorporation of Coelenterate Nematocysts in the Predatory Nudibranch Mollusc Hermissenda crassicornis, by Michelle Johnson and Misty Borja Accessed 2014-9-6
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