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Discovery of new hydrothermal activity and chemosynthetic fauna on the Central Indian Ridge at 18°-20° S.

Nakamura K, Watanabe H, Miyazaki J, Takai K, Kawagucci S, Noguchi T, Nemoto S, Watsuji TO, Matsuzaki T, Shibuya T, Okamura K, Mochizuki M, Orihashi Y, Ura T, Asada A, Marie D, Koonjul M, Singh M, Beedessee G, Bhikajee M, Tamaki K - PLoS ONE (2012)

Bottom Line: In contrast, at the Solitaire field, we observed faunal communities that potentially contained almost all genera found at CIR hydrothermal environments to date, and even identified previously unreported taxa.Moreover, a new morphotype of 'scaly-foot' gastropod has been found at the Solitaire field.Our new findings at the two newly discovered hydrothermal vent sites provide important insights into the biodiversity and biogeography of vent-endemic ecosystems in the Indian Ocean.

View Article: PubMed Central - PubMed

Affiliation: Precambrian Ecosystem Laboratory (PEL), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan. kentaron@jamstec.go.jp

ABSTRACT
Indian Ocean hydrothermal vents are believed to represent a novel biogeographic province, and are host to many novel genera and families of animals, potentially indigenous to Indian Ocean hydrothermal systems. In particular, since its discovery in 2001, much attention has been paid to a so-called 'scaly-foot' gastropod because of its unique iron-sulfide-coated dermal sclerites and the chemosynthetic symbioses in its various tissues. Despite increasing interest in the faunal assemblages at Indian Ocean hydrothermal vents, only two hydrothermal vent fields have been investigated in the Indian Ocean. Here we report two newly discovered hydrothermal vent fields, the Dodo and Solitaire fields, which are located in the Central Indian Ridge (CIR) segments 16 and 15, respectively. Chemosynthetic faunal communities at the Dodo field are emaciated in size and composition. In contrast, at the Solitaire field, we observed faunal communities that potentially contained almost all genera found at CIR hydrothermal environments to date, and even identified previously unreported taxa. Moreover, a new morphotype of 'scaly-foot' gastropod has been found at the Solitaire field. The newly discovered 'scaly-foot' gastropod has similar morphological and anatomical features to the previously reported type that inhabits the Kairei field, and both types of 'scaly-foot' gastropods genetically belong to the same species according to analyses of their COI gene and nuclear SSU rRNA gene sequences. However, the new morphotype completely lacks an iron-sulfide coating on the sclerites, which had been believed to be a novel feature restricted to 'scaly-foot' gastropods. Our new findings at the two newly discovered hydrothermal vent sites provide important insights into the biodiversity and biogeography of vent-endemic ecosystems in the Indian Ocean.

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Morphological differences in the vestigial opercula of ‘scaly-foot’ gastropods.(A) Dorsal surface of the operculum of a juvenile individual. (B) Dorsal surface of the operculum of an adult individual. (C) Outer surface of the sclerite of an adult individual. (D) Ventral surface of the operculum of a juvenile individual. (E) Ventral surface of an adult individual. (F) Inner surface of the sclerite of an adult individual. Scale bar indicates 1 mm.
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pone-0032965-g009: Morphological differences in the vestigial opercula of ‘scaly-foot’ gastropods.(A) Dorsal surface of the operculum of a juvenile individual. (B) Dorsal surface of the operculum of an adult individual. (C) Outer surface of the sclerite of an adult individual. (D) Ventral surface of the operculum of a juvenile individual. (E) Ventral surface of an adult individual. (F) Inner surface of the sclerite of an adult individual. Scale bar indicates 1 mm.

Mentions: It has also been believed that the characteristics of adult ‘scaly-foot’ gastropod are the absence of an operculum with well-developed sclerites covering the foot, although the origin of these sclerites remains uncertain [13], [26]. During the present investigation, a juvenile ‘scaly-foot’ gastropod with a vestigial opercular plate and sparse sclerites on the lateral sides was collected (Figure 8A). Interestingly, about a half (18 of 34 individuals) of the adult ‘scaly-foot’ gastropods in the Solitaire site also had a vestigial opercular plate among the sclerites at the rear of the animal (Figure 8B), and the morphology of the operculum changed during growth, from a rounded shape in juveniles to a curved shape in adults (Figure 9). It seems likely that the sclerites gradually proliferate and fully cover the whole foot for protection, while the operculum loses its protective function as the animal grows. The present observation revealed that opercular plates are not absent in the ‘scaly-foot’ gastropods even in the adult stage, and, based on the morphological similarities, that they may have some relationships to the sclerites.


Discovery of new hydrothermal activity and chemosynthetic fauna on the Central Indian Ridge at 18°-20° S.

Nakamura K, Watanabe H, Miyazaki J, Takai K, Kawagucci S, Noguchi T, Nemoto S, Watsuji TO, Matsuzaki T, Shibuya T, Okamura K, Mochizuki M, Orihashi Y, Ura T, Asada A, Marie D, Koonjul M, Singh M, Beedessee G, Bhikajee M, Tamaki K - PLoS ONE (2012)

Morphological differences in the vestigial opercula of ‘scaly-foot’ gastropods.(A) Dorsal surface of the operculum of a juvenile individual. (B) Dorsal surface of the operculum of an adult individual. (C) Outer surface of the sclerite of an adult individual. (D) Ventral surface of the operculum of a juvenile individual. (E) Ventral surface of an adult individual. (F) Inner surface of the sclerite of an adult individual. Scale bar indicates 1 mm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3303786&req=5

pone-0032965-g009: Morphological differences in the vestigial opercula of ‘scaly-foot’ gastropods.(A) Dorsal surface of the operculum of a juvenile individual. (B) Dorsal surface of the operculum of an adult individual. (C) Outer surface of the sclerite of an adult individual. (D) Ventral surface of the operculum of a juvenile individual. (E) Ventral surface of an adult individual. (F) Inner surface of the sclerite of an adult individual. Scale bar indicates 1 mm.
Mentions: It has also been believed that the characteristics of adult ‘scaly-foot’ gastropod are the absence of an operculum with well-developed sclerites covering the foot, although the origin of these sclerites remains uncertain [13], [26]. During the present investigation, a juvenile ‘scaly-foot’ gastropod with a vestigial opercular plate and sparse sclerites on the lateral sides was collected (Figure 8A). Interestingly, about a half (18 of 34 individuals) of the adult ‘scaly-foot’ gastropods in the Solitaire site also had a vestigial opercular plate among the sclerites at the rear of the animal (Figure 8B), and the morphology of the operculum changed during growth, from a rounded shape in juveniles to a curved shape in adults (Figure 9). It seems likely that the sclerites gradually proliferate and fully cover the whole foot for protection, while the operculum loses its protective function as the animal grows. The present observation revealed that opercular plates are not absent in the ‘scaly-foot’ gastropods even in the adult stage, and, based on the morphological similarities, that they may have some relationships to the sclerites.

Bottom Line: In contrast, at the Solitaire field, we observed faunal communities that potentially contained almost all genera found at CIR hydrothermal environments to date, and even identified previously unreported taxa.Moreover, a new morphotype of 'scaly-foot' gastropod has been found at the Solitaire field.Our new findings at the two newly discovered hydrothermal vent sites provide important insights into the biodiversity and biogeography of vent-endemic ecosystems in the Indian Ocean.

View Article: PubMed Central - PubMed

Affiliation: Precambrian Ecosystem Laboratory (PEL), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Kanagawa, Japan. kentaron@jamstec.go.jp

ABSTRACT
Indian Ocean hydrothermal vents are believed to represent a novel biogeographic province, and are host to many novel genera and families of animals, potentially indigenous to Indian Ocean hydrothermal systems. In particular, since its discovery in 2001, much attention has been paid to a so-called 'scaly-foot' gastropod because of its unique iron-sulfide-coated dermal sclerites and the chemosynthetic symbioses in its various tissues. Despite increasing interest in the faunal assemblages at Indian Ocean hydrothermal vents, only two hydrothermal vent fields have been investigated in the Indian Ocean. Here we report two newly discovered hydrothermal vent fields, the Dodo and Solitaire fields, which are located in the Central Indian Ridge (CIR) segments 16 and 15, respectively. Chemosynthetic faunal communities at the Dodo field are emaciated in size and composition. In contrast, at the Solitaire field, we observed faunal communities that potentially contained almost all genera found at CIR hydrothermal environments to date, and even identified previously unreported taxa. Moreover, a new morphotype of 'scaly-foot' gastropod has been found at the Solitaire field. The newly discovered 'scaly-foot' gastropod has similar morphological and anatomical features to the previously reported type that inhabits the Kairei field, and both types of 'scaly-foot' gastropods genetically belong to the same species according to analyses of their COI gene and nuclear SSU rRNA gene sequences. However, the new morphotype completely lacks an iron-sulfide coating on the sclerites, which had been believed to be a novel feature restricted to 'scaly-foot' gastropods. Our new findings at the two newly discovered hydrothermal vent sites provide important insights into the biodiversity and biogeography of vent-endemic ecosystems in the Indian Ocean.

Show MeSH
Related in: MedlinePlus