Smeagol (gastropod)

Smeagol
Smeagol climoi on seaweed buried in gravel, Houghton Bay, Wellington
Scientific classification
Kingdom:
Animalia
Phylum:
Mollusca
Class:
Gastropoda
(unranked):
clade Heterobranchia

clade Euthyneura
clade Panpulmonata

clade Eupulmonata
Superfamily:
Otinoidea
Family:
Ellobiidae

Pfeiffer, 1854
Genus:
Smeagol

Climo, 1980[1]
Diversity
5 or 6 species

Smeagol is a genus of small air-breathing[2] sea slugs of the upper intertidal zone.[3] They are pulmonate gastropod mollusks related to land slugs and snails.

Analysis of DNA sequences has shown that Smeagol belongs in the family Ellobiidae, and is therefore closely related to ellobiid snails.[4]

Etymology

Smeagol was named after Gollum, a fictional character from Tolkien's legendarium

The name of the genus is in honour of Tolkien's fictional character Gollum, who was originally known as Sméagol.[1]

Taxonomy

There are five described species[5] and potentially one undescribed species from Tasmania[6] in the genus Smeagol:[5]

Anatomy

Smeagol manneringi has no tentacles and is a very active blind animal with a size of up to 10 mm.[1]

Smeagol species have no shell. They have a weakly developed snout.[2] The radula is unicuspid[1] and the radular dentition is of the rhipidoglossate type.[2] They have a radular membrane of flexoglossate type.[2] They have no jaw.[1][2] They have salivary glands with salivary ducts.[2]

The excretory organs are only the left ones, in the pallial cavity.[2] In the circulatory system the haemolymph circulates as follows: mantle → nephridium or nephridia[clarification needed] → heart.[2]

These slugs breathe using a pallial lung.[1] They have a contractile pneumostome.[2]

They have a suprapedal gland.[2]

The number of chromosomes is unknown.[2] They have no sex chromosomes.[2]

Distribution

The genus Smeagol is so far restricted to New Zealand and Australia.[1] Smeagol manneringi is known from the south coast of Wellington, and in a possibly genetically distinct form from Kaikoura.[7]

Ecology

These slugs inhabit the upper intertidal zone on gravel substrate.[5]

The development of the veliger is completed in the egg (they do not have a trochophore larval stage).[2]

References

  1. ^ a b c d e f g Climo, F. M. (1980). "Smeagolida, a new order of gymnomorph mollusc from New Zealand based on a new genus and species". New Zealand Journal of Zoology. 7 (4): 513–522. doi:10.1080/03014223.1980.11760683.
  2. ^ a b c d e f g h i j k l m Barker G. M. (2001) Gastropods on Land: Phylogeny, Diversity and Adaptive Morphology. 1-146. In: Barker G. M. (ed.) (2001) The biology of terrestrial molluscs. CABI Publishing, Oxon, UK, cited pages: 52, 127-134. ISBN 0-85199-318-4.
  3. ^ Marshall, B.; Rosenberg, G. (2016). Smeagol Climo, 1980. In: MolluscaBase (2017). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=551549 on 2017-09-13
  4. ^ Dayrat, Benoît; Conrad, Michele; Balayan, Shaina; White, Tracy R.; Albrecht, Christian; Golding, Rosemary; Gomes, Suzete R.; Harasewych, M.G.; Martins, António Manuel de Frias (2011). "Phylogenetic relationships and evolution of pulmonate gastropods (Mollusca): New insights from increased taxon sampling". Molecular Phylogenetics and Evolution. 59 (2): 425–437. doi:10.1016/j.ympev.2011.02.014. PMID 21352933.
  5. ^ a b c Tillier, S.; Ponder, W. F. (1992). "New species of Smeagol from Australia and New Zealand, with discussion of the affinities of the genus (Gastropoda: Pulmonata)". Journal of Molluscan Studies. 58 (2): 135–155. doi:10.1093/mollus/58.2.135.
  6. ^ West R. (February 2009). Proposed determination Smeagol hilaris, a marine slug, as a critically endangered species. Fisheries Scientific Committee, Ref. No. PD43, File No. FSC 09/01, 3 pp., PDF.
  7. ^ "Rare 'gravel maggot' found on remote West Coast beach". 1 News. 13 May 2022. Retrieved 2022-05-16.

Further reading

  • Haszprunar, G.; Huber, G. (1990). "On the central nervous system of Smeagolidae and Rhodopidae, two families questionably allied with the Gymnomorpha (Gastropoda: Euthyneura)". Journal of Zoology. 220 (2): 185–199. doi:10.1111/j.1469-7998.1990.tb04302.x.
  • Romero, P. E.; Pfenninger, M.; Kano, Y.; Klussmann-Kolb, A. (2016). "Molecular phylogeny of the Ellobiidae (Gastropoda: Panpulmonata) supports independent terrestrial invasions". Molecular Phylogenetics and Evolution. 97: 43–54. doi:10.1016/j.ympev.2015.12.014. PMID 26724408.
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