''Smeagol'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of small air-breathing

sea slug Sea slug is a common name for some Marine biology, marine invertebrates with varying levels of resemblance to terrestrial Slug, slugs. Most creatures known as sea slugs are gastropods, i.e. they are Sea snail, sea snails (marine gastropod moll ...

s of the upper

intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...

.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 They are pulmonate gastropod

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

s related to land slugs and snails. Analysis of DNA sequences has shown that ''Smeagol'' belongs in the family

Ellobiidae Ellobiidae, common name the hollow-shelled snails, is a family of small air-breathing land, marine, and brackish snails; pulmonate gastropod mollusks in the clade Eupulmonata.Bouchet, P. (2012). Ellobiidae. Accessed through: World Register of M ...

, and is therefore closely related to ellobiid snails.

Etymology

The name of the genus is in honour of

Tolkien John Ronald Reuel Tolkien (, 3 January 1892 – 2 September 1973) was an English writer and philologist. He was the author of the high fantasy works ''The Hobbit'' and ''The Lord of the Rings''. From 1925 to 1945, Tolkien was the Rawlinson ...

's fictional character

Gollum Gollum is a Tolkien's monsters, monster with a distinctive style of speech in J. R. R. Tolkien's fantasy world of Middle-earth. He was introduced in the 1937 Fantasy (genre), fantasy novel ''The Hobbit'', and became important in its sequel, ' ...

, who was originally known as Sméagol.

Taxonomy

There are five described species and potentially one undescribed species from

Tasmania Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...

in the genus ''Smeagol'':

Anatomy

''Smeagol manneringi'' has no

tentacles In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

and is a very active blind animal with a size of up to 10 mm. ''Smeagol'' species have no shell. They have a weakly developed

snout A snout is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw. In many animals, the structure is called a muzzle, Rostrum (anatomy), rostrum, beak or proboscis. The wet furless surface around the nostrils of the n ...

. The

radula The radula (; : radulae or radulas) is an anatomical structure used by mollusks for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters ...

is unicuspid and the radular dentition is of the rhipidoglossate type. They have a radular membrane of flexoglossate type. They have no

jaw The jaws are a pair of opposable articulated structures at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth ...

. They have

salivary glands The salivary glands in many vertebrates including mammals are exocrine glands that produce saliva through a system of Duct (anatomy), ducts. Humans have three paired major salivary glands (Parotid gland, parotid, Submandibular gland, submandibula ...

with salivary ducts. The excretory organs are only the left ones, in the pallial cavity. In the

circulatory system In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. It includes the cardiovascular system, or vascular system, that consists of the heart ...

the

haemolymph Hemolymph, or haemolymph, is a fluid, similar to the blood in invertebrates, that circulates in the inside of the arthropod's body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which hemolymph ce ...

circulates as follows: mantle →

nephridium The nephridium (: nephridia) is an invertebrate organ, found in pairs and performing a function similar to the vertebrate kidneys (which originated from the chordate nephridia). Nephridia remove metabolic wastes from an animal's body. Nephridia co ...

or nephridia → heart. These slugs breathe using a pallial lung. They have a contractile

pneumostome The pneumostome or breathing pore is a respiratory opening of the external body anatomy of a pulmonate land slug or land snail. It is a part of the respiratory system of gastropods. It is an opening in the right side of the mantle of a st ...

.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. . They have a

suprapedal gland The suprapedal gland or mucous pedal gland is an anatomical feature found in some snails and slugs. It is a gland located inside the front end of the foot of gastropods.Barker G. M. (2001) "Gastropods on Land: Phylogeny, Diversity and Adaptive Mor ...

. The number of

chromosomes A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most importa ...

is unknown. They have no

sex chromosomes Sex chromosomes (also referred to as allosomes, heterotypical chromosome, gonosomes, heterochromosomes, or idiochromosomes) are chromosomes that carry the genes that determine the sex of an individual. The human sex chromosomes are a typical pair ...

Distribution

The genus ''Smeagol'' is so far restricted to

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

and

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

. ''Smeagol manneringi'' is known from the south coast of

Wellington Wellington is the capital city of New Zealand. It is located at the south-western tip of the North Island, between Cook Strait and the Remutaka Range. Wellington is the third-largest city in New Zealand (second largest in the North Island ...

, and in a possibly genetically distinct form from Kaikōura.

Ecology

These slugs inhabit the upper

gravel Gravel () is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentation, sedimentary and erosion, erosive geological processes; it is also produced in large quantities commercially as crushed stone. Gr ...

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...

. The development of the

veliger A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells. Description The veliger is the characteristic larva of the gastropod, bivalve and scaphopod taxono ...

is completed in the egg (they do not have a

trochophore A trochophore () is a type of free-swimming planktonic marine larva with several bands of cilia. By moving their cilia rapidly, they make a water eddy to control their movement, and to bring their food closer in order to capture it more easily. ...

larval stage).

References

External links

* ''Smeagol'' discussed on

RNZ Radio New Zealand (), commonly known as RNZ or Radio NZ, is a New Zealand public service broadcaster and Crown entity. Established under the Radio New Zealand Act 1995, it operates news and current affairs station, RNZ National, and a classica ...

Critter of the Week ''Critter of the Week'' is a weekly RNZ National programme about endangered and neglected native plants and animals of New Zealand. Beginning in 2015, ''Critter of the Week'' is an approximately 15-minute discussion between Nicola Toki (origi ...

,'
17 September 2015
{{DEFAULTSORT:Smeagol (Gastropod) Gastropods of Australia Gastropods of New Zealand