''Gigantopelta chessoia'' 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 deep

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...

from

hydrothermal vent A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspot ...

s, a marine

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusk Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...

in the family

Peltospiridae Peltospiridae is a small family of gastropods that used to belong to the clade Vetigastropoda (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005), but is now included in the clade NeomphalinaBouchet, P.; Gofas, S. (2010). Pel ...

Taxonomy

The first information about this species, under the name "Peltospiroidea n. sp." or "peltospiroid gastropod", was published on 3 January 2012. Peltospiroidea is the name of a superfamily of gastropods that was used in the

taxonomy of the Gastropoda (Ponder & Lindberg, 1997) The taxonomy of the Gastropoda, as revised by Winston Ponder and David R. Lindberg in 1997, is an older taxonomy of the class Gastropoda, the class of molluscs consisting of all snails and slugs. The full name of the work in which this taxonomy wa ...

. It contained the only extant family

(and some prehistoric gastropod families). However, the

taxonomy of the Gastropoda (Bouchet & Rocroi, 2005) The taxonomy of the Gastropoda as it was revised in 2005 by Philippe Bouchet and Jean-Pierre Rocroi is a system for the scientific classification of gastropod mollusks. (Gastropods are a taxonomic class of animals which consists of snails and ...

does not use the name Peltospiroidea (in that system, the family Peltopiridae is placed within the

Neomphaloidea Neomphaloidea is a Taxonomic rank, superfamily of deep-sea snails or limpets, marine (ocean), marine gastropod mollusc, mollusks. Neomphaloidea is the only superfamily in the order Neomphalida. The order Neomphalida has the largest ''In situ#Bi ...

). It was described as a new species within new genus ''Gigantopelta'' in 2015 and it was classified within the family Peltospiridae. East Scotia Ridge vents map

Distribution

This species is known from two sites near hydrothermal vents in the

East Scotia Ridge The Scotia Plate () is a tectonic plate on the edge of the South Atlantic and Southern oceans. Thought to have formed during the early Eocene with the opening of the Drake Passage that separates South America from Antarctica, it is a minor pla ...

of the south

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

: from 2,394 m depth at the E9 vent site and from the 2,608 m depth at the E2 site.

Description

The color of 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 ou ...

is dark olive. The shell has three to four

whorls A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). Whorls in nature File:Photograph and axial plane floral d ...

. The width of the shell is from 4.21–45.7 mm. Body size of the juvenile snail is 2 mm, while body size of the adult is 50 mm. It has non-papillate tentacles. The

digestive system The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller compone ...

: there is one pair of

radula The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs 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 ...

cartilages. The digestive tract is short and consist of a single loop. The rectum does not penetrate the heart. The radula consist of 1.4% of body volume in juveniles and radula cartilages consist of 2.6% of body volume in juveniles. The

respiratory system The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...

consist of single left bipectinate ctenidium (gill). The

circulatory system The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...

hypertrophied Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It is distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number.Updated by Linda J. ...

: heart is greatly enlarged. The ventricle is 0.42 mm in juvenile animal length of 2.0 mm. The ventricle grows to the size 6 mm in adults. There is a single left auricle. ''Gigantopelta chessoia'' has symbiotic bacteria in its enlarged

oesophageal gland The esophageal glands are glands that are part of the digestive system of various animals, including humans. In humans Esophageal glands in humans are a part of a human digestive system. They are a small compound racemose exocrine glands of the mu ...

. The body of ''Gigantopelta chessoia'' has low values of carbon isotope

δ13C In geochemistry, paleoclimatology, and paleoceanography ''δ''13C (pronounced "delta c thirteen") is an isotopic signature, a measure of the ratio of stable isotopes 13C : 12C, reported in parts per thousand (per mil, ‰). The measure is also ...

. This indicates that

carbon fixation Biological carbon fixation or сarbon assimilation is the process by which inorganic carbon (particularly in the form of carbon dioxide) is converted to organic compounds by living organisms. The compounds are then used to store energy and as ...

in ''Gigantopelta chessoia'' can occur via

Calvin-Benson-Bassham cycle The Calvin cycle, light-independent reactions, bio synthetic phase, dark reactions, or photosynthetic carbon reduction (PCR) cycle of photosynthesis is a series of chemical reactions that convert carbon dioxide and hydrogen-carrier compounds into ...

by endosymbiotic

Gammaproteobacteria Gammaproteobacteria is a class of bacteria in the phylum Pseudomonadota (synonym Proteobacteria). It contains about 250 genera, which makes it the most genera-rich taxon of the Prokaryotes. Several medically, ecologically, and scientifically imp ...

.Reid W. D. K., Sweeting C. J., Wigham B. D., Zwirglmaier K., Hawkes J. A., McGill R. A. R, Linse K. & Polunin N. V. C. (2013). "Spatial Differences in East Scotia Ridge Hydrothermal Vent Food Webs: Influences of Chemistry, Microbiology and Predation on Trophodynamics". ''PLoS ONE'' 8(6): e65553. . The occurrence of endosymbiont bacteria in the oesophageal gland was confirmed by

transmission electron microscopy Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a g ...

in 2017. The oesophageal gland is fused and enlarged to fill the entire ventral side of

mantle cavity The mantle (also known by the Latin word pallium meaning mantle, robe or cloak, adjective pallial) is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of ...

. It is occupying 0.6% of visceral mass volume in juveniles, while it is increasing

allometric Allometry is the study of the relationship of body size to shape, anatomy, physiology and finally behaviour, first outlined by Otto Snell in 1892, by D'Arcy Thompson in 1917 in ''On Growth and Form'' and by Julian Huxley in 1932. Overview Allom ...

ally up to 9% visceral mass volume in adults. Blood sinuses are large, but few and fixed in position. The

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 th ...

has ganglia. The

sensory organs A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of stimuli. (For example, in the human body, the brain which is part of the central nervous system rec ...

of ''Gigantopelta chessoia'' include

statocyst The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, ctenophorans, echinoderms, cephalopods, and crustaceans. A similar structure is also found in ''Xenoturbella''. The statocyst cons ...

s with statolith. The

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 ...

has fully developed gonads in juveniles at body size 2.0 mm.

Ecology

This gastropod is generally found in dense aggregations up to ~1,000 m⁻². Small limpets ''Lepetodrilus'' sp. East Scotia Ridge are sometimes found on the shells of ''Gigantopelta chessoia''. Other marine fauna, such as actinostolid

sea anemone Sea anemones are a group of predation, predatory marine invertebrates of the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemones are classifi ...

s (family

Actinostolidae Actinostolidae is a family of sea anemones in the order Actiniaria. Members of this family are deep sea species, with some occurring at hydrothermal vents. Genera The following genera are recognised by the World Register of Marine Species Th ...

), crabs in the genus '' Kiwa'', and the pycnogonid arthropod or "sea spider" cf. ''

Sericosura ''Sericosura'' is a genus of sea spiders in the family Ammotheidae. Species within this genus have been found living at depths from 106 to 3,690 meters below sea level. Species * '' Sericosura bamberi'' Arango & Linse, 2015 * '' Sericosura coc ...

'', can be found living together with this species. ''Gigantopelta chessoia'' may be a

mixotroph A mixotroph is an organism that can use a mix of different sources of energy and carbon, instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other. It is estimated that mixotrophs comp ...

in juvenile life and shifting to obligate symbiotrophy as an adult. ''Gigantopelta chessoia'' is

gonochoristic In biology, gonochorism is a sexual system where there are only two sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric. Gonochorism c ...

(they have distinct males and females).

References

This article incorporates Creative Commons (CC-BY-2.5) text from the referenceRogers A.D., Tyler P.A., Connelly D.P., Copley J.T., James R., Larter R.D., Linse K., Mills R.A., Garabato A.N., Pancost R.D., Pearce D.A., Polunin N.V., German C.R., Shank T., Boersch-Supan P.H., Alker B.J., Aquilina A., Bennett S.A., Clarke A., Dinley R.J., Graham A.G., Green D.R., Hawkes J.A., Hepburn L., Hilario A., Huvenne V.A., Marsh L., Ramirez-Llodra E., Reid W.D., Roterman C.N., Sweeting C.J., Thatje S. & Zwirglmaier K. (2012). "The Discovery of New Deep-Sea Hydrothermal Vent Communities in the Southern Ocean and Implications for Biogeography". ''PLoS Biology'' ''10''(1): e1001234. . and CC-BY-4.0 text from the reference

External links

* Heywood J. L., Chen C., Pearce D. A. & Linse K. (2017). "Bacterial communities associated with the Southern Ocean vent gastropod, ''Gigantopelta chessoia'': indication of intergenerational, horizontal symbiont transfer". ''

Polar Biology ''Polar Biology'' is a monthly peer-reviewed scientific journal covering the biology of the polar regions. It is published by Springer Science+Business Media. According to the ''Journal Citation Reports'', the journal has a 2015 impact factor T ...

''. . * Marsh L., Copley J. T., Huvenne V. A. I., Linse K., Reid W. D. K., Rogers A. D., Sweeting C. J. & Tyler P. A. (2012). "Microdistribution of faunal assemblages at deep-sea hydrothermal vents in the Southern Ocean". ''PLoS ONE'' 7: e48348. * Reid W. D. K., Sweeting C. J., Wigham B. D., McGill R. A. R. & Polunin N. V. C. (2016). "Isotopic niche variability in macroconsumers of the East Scotia Ridge (Southern Ocean) hydrothermal vents: What more can we learn from an ellipse?" ''

Marine Ecology Progress Series The ''Marine Ecology Progress Series'' is a peer-reviewed scientific journal that covers all aspects of marine ecology. History The journal was founded by Otto Kinne. Its original concept was based on ''Marine Ecology'', also once edited by Kin ...

'' 542: 13-24. {{Taxonbar, from=Q7161772 Peltospiridae Gastropods described in 2015