''Bullacta exarata'', common name the Korean mud snail, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of a sea snail or bubble snail, a marine gastropod mollusc in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Haminoeidae Haminoeidae, commonly known as the haminoeid bubble snail family, is a taxonomic family of sea snails, marine opisthobranch gastropod mollusks in the superfamily Haminoeoidea. The name of this family has long been controversial, and used to be ...

, the bubble snails. ''Bullacta exarata'' is a commercially important mollusc which is used as a food item in eastern China.

Taxonomy

''Bullacta exarata'' is the only species in the genus ''Bullacta''. cf. ''Bullacta'' is the type genus of the family Bullactidae Thiele, 1926, as shown in the taxonomy of the Gastropoda by Bouchet & Rocroi (2005). Based on phylogenetic genetic analysis by Malaquias (2010), ''Bullacta exarata'' should be placed in the family

Distribution

''Bullacta exarata'' is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to coastlines of the South and East China Seas from

Hainan Hainan (, ; ) is the smallest and southernmost province of the People's Republic of China (PRC), consisting of various islands in the South China Sea. , the largest and most populous island in China,The island of Taiwan, which is slightly l ...

to the

Bohai Sea The Bohai Sea () is a marginal sea approximately in area on the east coast of Mainland China. It is the northwestern and innermost extension of the Yellow Sea, to which it connects to the east via the Bohai Strait. It has a mean depth of ...

in north-eastern China, the western coast and south coast of Korea and Japan.Ye S.-F. & Lu J.-J. (2001) "Analysis on the spatial distribution of ''Bullacta exarata'' (Mollusca: Gastropoda: Atyidae) population in Yangtze River Estuary, China". '' Zool Res'' 22: 131-136.
abstract
An

ecotype In evolutionary ecology, an ecotype,Greek: ''οίκος'' = home and ''τύπος'' = type, coined by Göte Turesson in 1922 sometimes called ecospecies, describes a genetically distinct geographic variety, population, or race within a specie ...

of this snail introduced from further south has become invasive in

Laizhou Bay Laizhou Bay () is a bay on the southern shore of the Bohai Sea (also known as the ''Bohai Gulf'', or just ''Bo Hai'', which is a large and relatively shallow westward extension of the northern Yellow Sea), bounded by the northwestern coastline of ...

, with population densities of over 160 snails per square meter.

Description

The

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard o ...

is bullate, fairly thick, white, spirally striate, with a well-developed periostracum. There is no

spire A spire is a tall, slender, pointed structure on top of a roof of a building or tower, especially at the summit of church steeples. A spire may have a square, circular, or polygonal plan, with a roughly conical or pyramidal shape. Spires a ...

and no umbilicus. The

columella Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire. His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the wo ...

is smooth and simple. The

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An ...

extends for the whole length of the shell, and is narrower above than below. The apertural lip extends upwards beyond the

apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics), a teenaged super villainess in the Marvel Universe * Ape-X, a super-intelligent ape in the Squadron Supreme universe *Apex, ...

of the shell. The height of the shell is 8 mm and the width of the shell is 6 mm. The animal cannot withdraw itself into the shell, which contains the visceral hump only. The cephalic disc is large and slipper-shaped, feebly emarginate on the dorsal surface behind and with a narrow free margin. The cephalic disc, which is rounded in front, occupies about half of the whole bulk in a contracted state. The edge of the mantle is smooth, without processes of any kind. It, the edge of the mantle (which is slightly retroverted over that of the shell), the foot and the epipodia are (in alcohol) of a pale green colour. The greater part of the mantle, however, under the shell is colourless and transparent. The foot is short, truncate before and behind, and with the epipodia (in much contracted specimens) apparently not well developed. The eyes are minute and quite invisible on the surface. The eyespots are deeply sunk in the tissues. The gill, which is situated far back on the right side, is large and consists of a considerable number of fleshly lobes. Bullacta exarata radula

Digestive system: The mouth is a minute transverse slit in the front of the cephalic disc. The jawss are large, but imperfectly cornified. The jaws are angular and minutely, irregularly serrate. They are composed of numerous minute prismatic rods. On the margin many of these rods are transverse and project slightly, forming a minute serration. The radular sack is small. The radula has the formula 12.1.1.1.12. The central tooth is a simple flat triangular plate. The single lateral tooth is well differentiated from the marginal teeth, from which it is separated by a considerable space, and points in the opposite direction. The marginal teeth are slender, elongate, curved rod-like bodies somewhat expanded at the base. They decrease in size gradually from the second or third marginal, which is slightly larger than the first, outwards. There is a long, narrow, thin-walled

oesophagus The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to th ...

with a single coil; before entering the muscular gizzard it is considerably dilated. A longitudinal strand of muscular tissue runs up its dorsal surface for a short distance from the gizzard. The gizzard is large and it contains three horn-shaped, transversely ridged

chitinous Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

plates arranged in a triangle. It is maintained in position by a stout transverse muscle on either side, the proximal end of the muscle being fixed to a constriction in the outer wall of the gizzard. The gizzard contains three large, stout chitinous bodies, which are smooth and heart-shaped at their base on its external surface. Internally they are convex, curved and tapering, with stout, somewhat serrate reversed V-shaped transverse ridges. The intestine after leaving the gizzard bears three small, almost spherical, diverticula, one behind the base of each of the chitinous plates. The wall of the intestine is thin and its structure simple; it has a single closely adpressed bend. Bullacta exarata penis-sack

Reproductive system The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are als ...

: The male intromittent organ is provided with an elongate chitinous stylet. The penis is enclosed in an oval sack. When extracted therefrom it is an almost cylindrical organ with two coils, or constrictions, in its course, bluntly pointed at the apex and much contracted proximally. Its walls are highly muscular, but all the muscles are longitudinal and there is no circular muscular bulb. Its outstanding feature is the presence of a long, slender, sharply pointed, scimitar-shaped, black, horny stylet with a saddle-shaped base which is sometimes prolonged into a long, sharply pointed spur. In some individuals, however, the spur is completely absent. The female genitalia include a well-developed

uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The ...

but no

spermatheca The spermatheca (pronounced plural: spermathecae ), also called receptaculum seminis (plural: receptacula seminis), is an organ of the female reproductive tract in insects, e.g. ants, bees, some molluscs, oligochaeta worms and certain other in ...

. The hermaphrodite gland is small in immature specimen.

Nervous system In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes ...

: The

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

closely resembles that of '' Aliculastrum cylindricum''.

Ecology

The habitat for this species includes intertidal flats, including the

supratidal zone The supralittoral zone, also known as the splash zone, spray zone or the supratidal zone, sometimes also referred to as the white zone, is the area above the spring high tide line, on coastlines and estuaries, that is regularly splashed, but not s ...

and subtidal zone. ''Bullacta exarata'' is a

hermaphroditic In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have s ...

species. Its life cycle has been extensively studied: * Vitellogenesis (Ying & Yang, 2001) * Oogenesis (Ying, 2002) * Spermatogenesis (Ying et al., 2002) * Reproductive system (Ying et al., 2002) * Spermatozoa (Ying et al., 2004). ''Bullacta exarata'' feeds on

diatoms A diatom (New Latin, Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group com ...

. It is an important consumer in the

tidal flat Mudflats or mud flats, also known as tidal flats or, in Ireland, slob or slobs, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A global analysis published in 2019 suggested that tidal fl ...

ecosystem.

Bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

identified in the digestive system of ''Bullacta exarata'' include the genera '' Photobacterium'', ''

Bacillus ''Bacillus'' (Latin "stick") is a genus of Gram-positive, rod-shaped bacteria, a member of the phylum '' Bacillota'', with 266 named species. The term is also used to describe the shape (rod) of other so-shaped bacteria; and the plural ''Bacill ...

'', ''

Pseudomonas ''Pseudomonas'' is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 described species. The members of the genus demonstrate a great deal of metabolic diversity and consequently are able t ...

'', ''

Vibrio ''Vibrio'' is a genus of Gram-negative bacteria, possessing a curved-rod (comma) shape, several species of which can cause foodborne infection, usually associated with eating undercooked seafood. Being highly salt tolerant and unable to survive ...

'', some genera from the family Enterobacteriaceae and others. According to the measurement of hygienic indicator bacteria ''

Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Esc ...

'' in 2001, the meat of ''Bullacta exarata'' meets national standards (3 cells of ''Escherichia coli'' in one gram of fresh meat) in

Shanghai Shanghai (; , , Standard Mandarin pronunciation: ) is one of the four direct-administered municipalities of the People's Republic of China (PRC). The city is located on the southern estuary of the Yangtze River, with the Huangpu River flowin ...

province and in most of

Zhejiang Zhejiang ( or , ; , Chinese postal romanization, also romanized as Chekiang) is an East China, eastern, coastal Provinces of China, province of the People's Republic of China. Its capital and largest city is Hangzhou, and other notable citie ...

province.

UNEP The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on ...

, Qu J., Xu Z., Long Q., Wang L., Shen X., Zhang J. & Cai Y. (2005)
''East China Sea, GIWA Regional assessment 36.''
University of Kalmar, Kalmar, Sweden. 81 pp. + annexes. page 29, Heavy metals in the tissues of ''Bullacta exarata'' from the

Yangtze The Yangtze or Yangzi ( or ; ) is the longest river in Asia, the third-longest in the world, and the longest in the world to flow entirely within one country. It rises at Jari Hill in the Tanggula Mountains (Tibetan Plateau) and flows ...

Estuary were measured by Lu et al. in 2001. In Shanghai, the coast is seriously polluted and measured pollutants in the meat of ''Bullacta exarata'' were in 2003 as follows: * 20.70 mg of

petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...

hydrocarbons in one kg of wet weight (exceeds grade I of biological standard) * 13.10 mg of

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

in one kg of wet weight * 33.60 mg of

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

in one kg of wet weight (exceeds grade II of biological standard)

Human use

''Bullacta exarata'' is a commercially important mollusc in eastern China. Common names in

Mandarin Chinese Mandarin (; ) is a group of Chinese (Sinitic) dialects that are natively spoken across most of northern and southwestern China. The group includes the Beijing dialect, the basis of the phonology of Standard Chinese, the official language ...

include Tutie () and Niluo (). It is exported as a food source to Hong Kong, Macau, Taiwan and to

Southeast Asia Southeast Asia, also spelled South East Asia and South-East Asia, and also known as Southeastern Asia, South-eastern Asia or SEA, is the geographical south-eastern region of Asia, consisting of the regions that are situated south of mainlan ...

. It is also used in

traditional Chinese medicine Traditional Chinese medicine (TCM) is an alternative medical practice drawn from traditional medicine in China. It has been described as "fraught with pseudoscience", with the majority of its treatments having no logical mechanism of acti ...

and there were isolated various compounds with pharmacological activities from ''Bullacta exarata''. Mass mortalities of ''Bullacta exarata'' in Zhejiang in 1995 caused economic losses. The species is being cultivated in mariculture, especially in

Province, where there was a cultivated area of 8,000 ha in 1999. For example, ''Bullacta exarata'' was the main farming species at the farming area of about 10 100 mu (6.73266 km²) in the

Cixi City Cixi (), alternately romanized as Tzeki, is a county-level city under the jurisdiction of the sub-provincial city of Ningbo, in the north of Zhejiang province, China. As of the 2020 census, its population was 1,829,488. Its urban agglomeration bui ...

, with an estimated annual output of 15 million

RMB The renminbi (; symbol: ¥; ISO code: CNY; abbreviation: RMB) is the official currency of the People's Republic of China and one of the world's most traded currencies, ranking as the fifth most traded currency in the world as of April 2022. ...

.People's Republic of China, Ningbo Municipal Government, The World Bank (2005)
"Ningbo Water Environment Project Design Review And Advisory Services Environmental Assessment Volume 2: Summary EA"
accessed 17 December 2010. ''Bullacta exarata'' has high

nutrition Nutrition is the biochemical and physiological process by which an organism uses food to support its life. It provides organisms with nutrients, which can be metabolized to create energy and chemical structures. Failure to obtain sufficient ...

value. There is high amount of

omega-3 fatty acid Omega−3 fatty acids, also called Omega-3 oils, ω−3 fatty acids or ''n''−3 fatty acids, are polyunsaturated fatty acids (PUFAs) characterized by the presence of a double bond, three atoms away from the terminal methyl group in their chem ...

s in the canned meat of ''Bullacta exarata'' (there is 600 mg of

eicosapentaenoic acid Eicosapentaenoic acid (EPA; also icosapentaenoic acid) is an omega-3 fatty acid. In physiological literature, it is given the name 20:5(n-3). It also has the trivial name timnodonic acid. In chemical structure, EPA is a carboxylic acid with a 20-c ...

in 100 g of meat).Siriamornpun S., Bhulaidok S., Sihamala O., Yang L. F. & Li D. (2006). "Composition of lipids and fatty acids of ''Bullacta exarata''". ''Asia Pacific Journal of Clinical Nutrition'' 15(Supplement 2): 129
PDF
.

References

This article incorporates public domain text from the reference