Diverticulum (mollusc anatomy)

Last updated
The aeolid nudibranch Flabellina lineata with enlargement of the cerata to show the coloured hepatic diverticula. Hepatic diverticula.jpg
The aeolid nudibranch Flabellina lineata with enlargement of the cerata to show the coloured hepatic diverticula.

As applied to mollusks, the Neo-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]

Contents

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]

Related Research Articles

<span class="mw-page-title-main">Nudibranch</span> Order of gastropods

Nudibranchs are a group of soft-bodied marine gastropod molluscs that shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to match, such as "clown", "marigold", "splendid", "dancer", "dragon", and "sea rabbit". Currently, about 3,000 valid species of nudibranchs are known.

<span class="mw-page-title-main">Sea slug</span> Group of marine invertebrates with varying levels of resemblance to terrestrial slugs

Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails that over evolutionary time have either completely lost their shells, or have seemingly lost their shells due to having a greatly reduced or internal shell. The name "sea slug" is most often applied to nudibranchs, as well as to a paraphyletic set of other marine gastropods without obvious shells.

<span class="mw-page-title-main">Metarminoidea</span> Superfamily of gastropods

Metarminoidea is a provisional taxonomic superfamily of colourful sea slugs, aeolid nudibranchs, marine opisthobranch gastropod molluscs in the clade Nudibranchia.

<i>Glaucus marginatus</i> Species of gastropod

Glaucus marginatus is a species of small, floating, blue sea slug; a pelagic (open-ocean) aeolid nudibranch; a marine opisthobranch gastropod mollusc in the family Glaucidae. This species is closely related to Glaucus atlanticus, and is part of a species complex along with Glaucus bennettae, Glaucus thompsoni, and Glaucus mcfarlanei. Like Glaucus atlanticus, it is commonly known as a blue dragon.

<span class="mw-page-title-main">Cerata</span> Anatomical structures found in nudibranch sea slugs

Cerata, singular ceras, are anatomical structures found externally in nudibranch sea slugs, especially in aeolid nudibranchs, marine opisthobranch gastropod mollusks in the clade Aeolidida. The word ceras comes from the Greek word "κέρας", meaning "horn", a reference to the shape of these structures.

<i>Aeolidia papillosa</i> Species of gastropod

Aeolidia papillosa, known as the common grey sea slug, is a species of nudibranch in the family Aeolidiidae.

<i>Paraflabellina funeka</i> Species of gastropod

The purple lady nudibranch, Paraflabellina funeka, is a species of aeolid nudibranch, and is a very colourful sea slug. It is a marine gastropod mollusc in the family Flabellinidae.

<i>Fjordia capensis</i> Species of gastropod

The white-edged nudibranch, Fjordia capensis, is a species of sea slug, specifically an aeolid nudibranch, a very colourful sea slug. It is a marine gastropod mollusc in the family Flabellinidae.

<i>Trinchesia speciosa</i> Species of gastropod

Trinchesia speciosa, common name the "candy nudibranch", is a species of sea slug, an aeolid nudibranch, a marine gastropod mollusc in the family Trinchesiidae.

<span class="mw-page-title-main">Phyllodesmium</span> Genus of gastropods

Phyllodesmium is a genus of predatory sea slugs, aeolid nudibranchs, marine gastropod molluscs in the family Facelinidae.

The black-dot nudibranch, Caloria sp. 1, as designated by Gosliner, 1987, is a species of sea slug, specifically an aeolid nudibranch. They are marine gastropod molluscs in the family Facelinidae.

The yellow-tipped nudibranch, Caloria sp. 2, as designated by Gosliner, 1987, is a species of sea slug, specifically an aeolid nudibranch, a marine gastropod mollusc in the family Facelinidae.

<i>Pteraeolidia ianthina</i> Species of gastropod

Pteraeolidia ianthina is a sea slug, an aeolid nudibranch in the family Facelinidae. It is known as a blue dragon, a name it shares with Glaucus atlanticus and Glaucus marginatus.

<i>Berghia</i> Genus of gastropods

Berghia is a genus of sea slugs, aeolid nudibranchs. They are shell-less marine gastropod molluscs in the family Aeolidiidae. They are covered in cerata which give them their unique tentacle look and color. Berghia are commonly found in shallow waters and their diet consists of strictly Aiptasia Anemone. This genus is now commonly used commercially to fight off Anemone populations in fish tanks.

<i>Coryphella verrucosa</i> Species of gastropod

Coryphella verrucosa, is a species of sea slug, an aeolid nudibranch, a marine gastropod mollusc in the family Coryphellidae.

<i>Cratena peregrina</i> Species of gastropod

Cratena peregrina, commonly called the pilgrim hervia, is a species of sea slug, an aeolid nudibranch, a marine gastropod mollusc in the family Facelinidae.

<span class="mw-page-title-main">Cnidosac</span>

A cnidosac is an anatomical feature that is found in the group of sea slugs known as aeolid nudibranchs, a clade of marine opisthobranch gastropod molluscs. A cnidosac contains cnidocytes, stinging cells that are also known as cnidoblasts or nematocysts. These stinging cells are not made by the nudibranch, but by the species that it feeds upon. However, once the nudibranch is armed with these stinging cells, they are used in its own defense.

<i>Tenellia phoenix</i> Species of gastropod

Tenellia phoenix is a species of sea slug, an aeolid nudibranch, a marine gastropod mollusc in the family Fionidae.

<i>Spurilla neapolitana</i> Species of gastropod

Spurilla neapolitana, the Neapolitan spurilla, is a species of sea slug, an aeolid nudibranch, a marine gastropod mollusk in the family Aeolidiidae. It is native to the western Atlantic Ocean, the Caribbean Sea and the Mediterranean Sea. This species was first described as Eolis neapolitana by the Italian naturalist Stefano delle Chiaje in 1841. However, although some authorities quote the year as 1823, the species does not appear in the first volume of delle Chiaje's memoirs, which was published that year. The species was later reassigned to the genus Spurilla.

<i>Phyllodesmium poindimiei</i> Species of gastropod

Phyllodesmium poindimiei is an Alcyonacea feeding, aeolid nudibranch Gastropod belonging to the family Facelinidae. Cerata are important in this clade in terms of their physical defense and efficient metabolic processes. This species is spread sporadically along tropical coastal regions such as Australia, Hawaii, and the Indo-Pacific living in diverse marine habitats such as coral reefs. Unlike other species in the Opisthobranch Mollusca clade, P. poindimiei’s lush pink cerata are used for defensive purposes other than Nematocyst (dinoflagellate) capture and toxin release. Organismal ties within these thriving, tropical ecosystems can be determinants of environment change, which affects massive coral ecosystems. Continuously changing marine ecosystems, such as coral reefs, are directly linked to the evolution of organisms that live and thrive in the tropics such as the soft nudibrach P. poindimiei.

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