Scaly-foot gastropod

Scaly-foot Gastropod.
The three known populations of
Chrysomallon squamiferum:
Kairei, Longqi, Solitaire (left to right).
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
(unranked): clade Neomphalina
Superfamily: Neomphaloidea
Family: Peltospiridae
Genus: Chrysomallon
Species: C. squamiferum
Binomial name
Chrysomallon squamiferum
Chen et al., 2015[1]

Chrysomallon squamiferum, common name the scaly-foot gastropod, is a species of deep-sea hydrothermal vent snail, a marine gastropod mollusc in the family Peltospiridae.[2] This vent endemic gastropod is known only from deep-sea hydrothermal vents in the Indian Ocean, where it has been found at depths of about 2,400 m (1.5 mi). The shell is of a unique construction with three layers; the outer layer consists of iron sulphides, the middle layer is equivalent to the organic periostracum found in other gastropods, and the innermost layer is made of aragonite. The foot is also unusual, being armored with iron-mineralised sclerites. The snail's tissues house a symbiotic gammaproteobacteria from which it appears to obtain its nourishment.

Taxonomy

According to WoRMS, "the name Chrysomallon or Crysomallon squamiferum was used in several databases and academic papers prior to 2015. However, the name was first validly published in the sense of the International Code of Zoological Nomenclature by Chen et al. (2015)".[3]

Habitat

The 'scaly-foot gastropod' is an iconic vent endemic gastropod known only from the deep-sea hydrothermal vents of Indian Ocean, around 2,400 metres (1.5 mi) to 2,800 metres (1.7 mi) deep.[1] This species was discovered in 2001, living on the bases of black smokers at the Kairei hydrothermal vent field, on the Central Indian Ridge, just north of the Rodrigues Triple Point and about 2,420 metres (7,940 ft) below the surface.[4] It has subsequently also been found in Solitaire field, Central Indian Ridge (off Mauritius) [5] and Longqi (aka. Dragon) field, Southwest Indian Ridge.[6][7] Longqi field serves as the type locality and all type material have originated from this vent field.[1]

Description

With shell length that averages at around 35 millimetres (1.4 in) and exceeds 45 millimetres (1.8 in) in large individuals, it is a very large peltospirid compared to most others which are below 15 millimetres (3⁄5 in) in shell length.[1] The snail's foot is very unusual in that it is armored with iron-mineralised sclerites, composed of iron sulphides[8] greigite and pyrite.[9] No other animal is known to use iron sulfides in this way.

two varieties of Scaly-foot gastropod

The Solitaire population has white sclerites instead of black due to lack of iron in them, most likely due to differences in the vent fluid composition. The purpose of sclerites has been speculated to be protection or detoxification,[10] but their true function is yet unknown. The sclerites of Kairei population is strongly magnetic due to the greigite (sulfur equivalent of magnetite) content and stick to magnets.

The snail's shell is also unusual. The shell structure is composed of three layers. The outer layer is about 30 μm thick, and is also made of iron sulphides, containing greigite Fe3S4. This makes this gastropod the only metazoan known so far that employs such material in its skeleton. The middle layer is equivalent to the organic periostracum found also in other gastropods, and is also the thickest of the three (about 150 μm). The innermost layer is made of aragonite, a form of calcium carbonate that is commonly found both in the shells of molluscs and in various corals.[2] Each layer appear to contribute to the effectiveness of the snail's defence in different ways. The middle organic layer appears to absorb the mechanical strain and energy generated by a squeezing attack (as by the claws of a crab), making the shell much tougher. The organic layer also acts to dissipate heat.[11] The United States military is currently funding research on the armor of the snail in hopes of developing insights into new military armor designs.[11]

It is a chemosymbiotic holobiont hosting a thioautotrophic (i.e., sulfur-oxidising) gammaproteobacterial endosymbiont in a much enlarged oesophageal gland, and appear to rely on these for nutrition.[12][13] The surface of sclerites also host a diverse variety of epibionts.[12]

References

  1. 1 2 3 4 Chen C, Linse K, Copley JT, Rogers AD (2015). "The ‘scaly-foot gastropod’: a new genus and species of hydrothermal vent-endemic gastropod (Neomphalina: Peltospiridae) from the Indian Ocean". Journal of Molluscan Studies 81: 322–334. doi:10.1093/mollus/eyv013.
  2. 1 2 Yao, H., Dao, M., Imholt, T., Huang, J., Wheeler, K., Suresh, S., and C. Ortiz (2010). "Protection Mechanisms Informed by the Unique Iron-Plated Armor of a Deep Sea Hydrothermal Vent Gastropod". PNAS 107: 987–992. doi:10.1073/pnas.0912988107.
  3. ↑ Bouchet, P. (2014). Chrysomallon squamiferum. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=736932 on 2015-04-22
  4. ↑ Van Dover CL, Humphris SE, Fornari D, Cavanaugh CM, Collier R, Goffredi SK, Hashimoto J, Lilley MD, Reysenbach AL, Shank TM, Von Damm KL, Banta A, Gallant RM, Gotz D, Green D, Hall J, Harmer TL, Hurtado LA, Johnson P, McKiness ZP, Meredith C, Olson E, Pan IL, Turnipseed M, Won Y, Young CR 3rd, Vrijenhoek RC (2001). "Biogeography and ecological setting of Indian Ocean hydrothermal vents". Science 294 (5543): 818–23. doi:10.1126/science.1064574. PMID 11557843.
  5. ↑ Nakamura, Kentaro; Watanabe, Hiromi; Miyazaki, Junichi; Takai, Ken; Kawagucci, Shinsuke; Noguchi, Takuro; Nemoto, Suguru; Watsuji, Tomo-o; Matsuzaki, Takuya; Shibuya, Takazo; Okamura, Kei; Mochizuki, Masashi; Orihashi, Yuji; Ura, Tamaki; Asada, Akira; Marie, Daniel; Koonjul, Meera; Singh, Manvendra; Beedessee, Girish; Bhikajee, Mitrasen; Tamaki, Kensaku; Schnur, Joel M. (14 March 2012). "Discovery of New Hydrothermal Activity and Chemosynthetic Fauna on the Central Indian Ridge at 18°–20°S". PLoS ONE 7 (3): e32965. doi:10.1371/journal.pone.0032965.
  6. ↑ Tao, C.; Lin, J.; Guo, S.; Chen, Y. J.; Wu, G.; Han, X.; German, C. R.; Yoerger, D. R.; Zhou, N.; Li, H.; Su, X.; Zhu, J. (23 November 2011). "First active hydrothermal vents on an ultraslow-spreading center: Southwest Indian Ridge". Geology 40 (1): 47–50. doi:10.1130/G32389.1.
  7. ↑ Chen, Chong; Copley, Jonathan T.; Linse, Katrin; Rogers, Alex D.; Sigwart, Julia (April 2015). "How the mollusc got its scales: convergent evolution of the molluscan scleritome". Biological Journal of the Linnean Society 114 (4): 949–954. doi:10.1111/bij.12462.
  8. ↑ Warén A, Bengtson S, Goffredi SK, Van Dover CL (2003). "A hot-vent gastropod with iron sulfide dermal sclerites". Science 302 (5647): 1007. doi:10.1126/science.1087696. PMID 14605361.
  9. ↑ Pickrell, John (2003-11-07). "Armor-Plated Snail Discovered in Deep Sea". National Geographic News.
  10. ↑ SUZUKI, Y; KOPP, R; KOGURE, T; SUGA, A; TAKAI, K; TSUCHIDA, S; OZAKI, N; ENDO, K; HASHIMOTO, J; KATO, Y (15 February 2006). "Sclerite formation in the hydrothermal-vent "scaly-foot" gastropod—possible control of iron sulfide biomineralization by the animal". Earth and Planetary Science Letters 242 (1-2): 39–50. Bibcode:2006E&PSL.242...39S. doi:10.1016/j.epsl.2005.11.029.
  11. 1 2 "Snail's iron armour eyed by military". CBC News. 2010-01-19.
  12. 1 2 Goffredi, S. K.; Waren, A.; Orphan, V. J.; Van Dover, C. L.; Vrijenhoek, R. C. (5 May 2004). "Novel Forms of Structural Integration between Microbes and a Hydrothermal Vent Gastropod from the Indian Ocean". Applied and Environmental Microbiology 70 (5): 3082–3090. doi:10.1128/AEM.70.5.3082-3090.2004. PMC 404406. PMID 15128570.
  13. ↑ Nakagawa, Satoshi; Shimamura, Shigeru; Takaki, Yoshihiro; Suzuki, Yohey; Murakami, Shun-ichi; Watanabe, Tamaki; Fujiyoshi, So; Mino, Sayaka; Sawabe, Tomoo; Maeda, Takahiro; Makita, Hiroko; Nemoto, Suguru; Nishimura, Shin-Ichiro; Watanabe, Hiromi; Watsuji, Tomo-o; Takai, Ken (8 August 2013). "Allying with armored snails: the complete genome of gammaproteobacterial endosymbiont". The ISME Journal 8 (1): 40–51. doi:10.1038/ismej.2013.131.

Further reading

External links

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