Genus of gastropods From Wikipedia, the free encyclopedia
Alviniconcha is a genus of deep water sea snails, marine gastropod mollusks in the family Paskentanidae.[1] These snails are part of the fauna of the hydrothermal vents in the Indian and Western Pacific Ocean.[2] These and another genus and species within the same family (Ifremeria nautilei) are the only known currently existing animals whose nutrition is derived from an endosymbiotic relationship with a member of bacteria from phylum Campylobacterota (formerly Epsilonproteobacteria) and Gammaproteobacteria, occurring as endosymbionts within the vacuoles of Alviniconcha ctenidia (or molluscan gills).[3] All species of Alviniconcha are thought to be foundational species found near hydrothermal venting fluid supplying their bacterial endosymbionts with vent derived compounds such as hydrogen sulfide. These snails can withstand large variations in temperature (5–33 °C (41–91 °F)),[4] pH, and chemical compositions.
| Alviniconcha | |
|---|---|
| |
| Two preserved specimens of Alviniconcha hessleri | |
| Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Gastropoda |
| Subclass: | Caenogastropoda |
| Family: | Paskentanidae |
| Subfamily: | Alviniconchinae |
| Genus: | Alviniconcha Okutani & Ohta, 1988 |
| Type species | |
| Alviniconcha hessleri Okutani & Ohta, 1988 | |
| Species[1] | |
| |
The size of the shell varies between 20 mm (0.79 in) up to 60 mm (2.4 in) in height. The surface of the shell is studded with hairs on the periostracum, which ranges from a yellow/green to brown coloring. However, this thin periostracum is often missing or degraded due to high temperatures and chemical reductants found in nearby venting fluid. While Alviniconcha has been considered cryptic for many years, morphoanatomy studies on A. boucheti, A. kojimai, and A. strummeri have found distinguishing characteristics of the shell and head-foot regions.[5] These three species are the only ones known to cohabitate vent fields, all other species are found in isolated basins in the NW Pacific and Indian Oceans. Morphoanatomy has not been studied for A. adamants, A. hessleri, or A. marisindica, thus shell variation or morphology does not yet correspond to individual species.[2]
Knowledge gaps remain in the life history of Alviniconcha, however adult shell anatomy resembles planktotrophic development.[4] Unlike the sister genus Ifremeria whose development includes a novel "Waren's" larval form, held within a brood pouch (absent in Alviniconcha).[6]
Until 2014, Alviniconcha consisted solely of the species Alviniconcha hessleri, described in 1988. In 2014, increased recognition of genetic differences between populations resulted in the formal description of five cryptic species within the former A. hessleri that were believed to be morphologically indistinguishable from each other but that have consistent differences in mitochondrial DNA sequences.[2] New research also suggests distributions of Alviniconcha in the SW Pacific are linked to geochemical gradients and endosymbiont chemical requirements.[7]
Species within the genus Alviniconcha include:
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