chemoautotrophic potential.
(^) Vents in the so-called back-arc systems of the northwestern Pacific are dominated
by provannid snails (Ifremeria and Alviniconcha), as are the hydrothermal areas of the
southwest Pacific. These two areas are mostly distinctive at the species level. The
vents on the Central Indian Ridge initially studied by Hashimoto et al. (2001) share
elements (families and genera) with both the southwest Pacific vent province
(provannid snails) and the Mid-Atlantic Ridge (distinctive Rimicaris). Simplifying a
quote from an early paper (Van Dover et al. 2001) describing the Indian Ocean vent
fields (called Kairei and Edmond) on the east side of its rift valley wall around 24°N:
(^) “The invertebrate community of the Kairei Field is characterized by an abrupt
transition between ... black smokers dominated by dense swarms of shrimp
(Rimicaris sp.) in 10° to 20°C fluids and an ambient-temperature (1° to 2°C)
peripheral zone dominated by anemones (Marianactis sp.) ... . At the base of
shrimp swarms, mussels, hairy gastropods [Alviniconcha n. sp.], and “scaly-foot”
gastropods [see section on charismatic invertebrates below] occur in separate
clusters of up to several hundred individuals. Brachyuran crabs (Austinograea n.
sp.), turbellarian flatworms, nemerteans, and a second shrimp species
(Chorocaris n. sp.) occur in sometimes dense but isolated patches in the narrow
transition zone separating anemones and swarming shrimp. Other gastropods
(limpets and ... snails), large ... polychaetes, and clusters of stalked ... barnacles
(Neolepas n. sp.) were observed frequently in this transition zone. ... Vesicomyid
shells [like Calyptogena] were collected within 1 km of the Kairei Field, but no
live clams have been observed.”
(^) [Bracketed comments are ours.]
(^) As you may or may not imagine, finding a massive diversity of reasonably large
animals “new to science” and all abundantly packed in one place (color photos in Van
Dover et al.) causes an explosion of joy, a dopamine flood, in the mind of a biologist.
They get to name new species after colleagues (e.g. Alviniconchia hessleri for Robert
Hessler) and to study details of their biology. For example, A. hessleri has been shown
to have endosymbiont epsilonproteobacteria in its gills (Suzuki et al. 2005).
(^) There is exchange at long ranges, but it is also limited. Possibly, shallow venting, as
in the Azores, and related cold-seep and whale-bone faunas (e.g. Osedax) have served
as sources of animals adapted for symbioses with chemosynthetic bacteria to new vent
fields.