Tuesday, 2 May 2017

Kuphus polythalamia: Can a giant, free-living Shipworm help to explain the evolution of chemotrophic symbiosis in hydrothermal vent communities.

Many Bivalves and other Animals living around deep-sea hydrothermal vents are host to communities of chemotrophic Bacteria, which produce bio-available carbon by the reaction of bicarbonate (dissolved carbon dioxide) with hydrogen sulphide compounds. These Animals are not unique and exotic creatures that have evolved separately from the fauna of the rest of the oceans, but rather members of common and widespread groups, suggesting the presence of a mechanism by which members of different groups can rapidly (in evolutionary terms) acquire the ability to host such endosymbiotic Bacteria.

One possibility that has been suggested is that symbiotic species found around hydrothermal vents have repeatedly evolved from wood-consuming species. Very few animals are able to directly consume wood, though a wide variety of species have adapted to a wood-based diet, relying on symbiotic Bacteria to break down the tough cellulose of which wood is composed. This not only leads to animals already adapted to hosting symbiotic Bacteria, but presents an opportunity for a switch to hydrogen sulphide consuming Bacteria, as rotting wood is a good source of such compounds. This could potentially also help to explain the distribution of hydrothermal vent communities (which are often very widely separated), as wood often drifts for very long distances between entering the sea and finally sinking to the ocean floor, so that wood-falls are very widely distributed in the oceans, and hydrogen sulphide producing rotting wood patches could provide stepping stones between distant hydrothermal vents. However, in the absence of any intermediate forms (i.e. animals which appear to be in the process of evolving from a wood-consuming lifestyle to a hydrogen sulphide absorbing one), this remains only an interesting hypothesis.

In a paper published in the Proceedings of the National Academy of Sciences of the United States of America on 17 April 2017, a team of scientists led by Daniel Distel of the Ocean Genome Legacy Center at Northeastern University, describe the lifestyle and endosymbiotic community of the Giant Shipworm, Kuphus polythalamia, and discuss whether it might represent an intermediate state between wood-consuming and hydrogen sulphide absorbing forms.

Shipworms, Teredinidae, are highly-modified, Worm-like Bivalve Molluscs which dwell inside wood that has fallen into the ocean (or, since Humans began to travel the seas, been used to construct vessels). The shells of these Molluscs are much reduced, forming a pair of opposable rasping ‘jaws’ at the mouth end of the animal, and a long, vermiform (Worm-shaped) body, which enables an elongate gut where wood is digested, using enzymes produced by Bacteria which live in specialized cells in the Mollusc’s gills.

The Giant Shipworm, Kuphus polythalamia, differs from other members of the group in two notable and obvious ways, it is much larger, reaching tens of centimetres in length, and it is not a wood-borer, being found either in rotten wood or organic rich muddy sediments. Closer examination of the Shipworms shows that the shell has become modified to form a calcareous cap, which completely covers the mouthparts, preventing feeding by ingesting food. 

Comparative anatomy and life position of Kuphus polythalamia and Lyrodus pedicellatus. (A) Fresh specimen of Kuphus polythalamia removed from its calcareous tube, (B) calcareous tube of Kuphus polythalamia removed from sediment, (C) diagram depicting the anatomy and life position of Kuphus polythalamia in sediment, and (D) Inset from box in (C) depicting the anatomy and life position of the woodfeeding Shipworm Lyrodus pedicellatus in wood. Scale bars: (A)–(C), 5.0 cm; (D), 0.5 cm.) b, bacteria; c, cecum; g, gill; HS−, hydrogen sulfide; m, mouth; p, pallet; s, siphon; t, calcareous tube; v, valve (shell); vm, visceral mass. Distel et al. (2017).

Distel et al. extracted Bacteria from the gills of Kuphus polythalamia in order to sequence their genomes and determine their relationships to other endosymbionts in Shipworms and other organisms. While some of these Bacteria proved to be very closely related to Bacteria found in other Shipworms, there were also species found that were closely related to Bacteria found in the hydrothermal vent Gastropods Crysomallon squamiferum and Alvinoconcha hessleri, as well as the marine Ciliate Protozoan Zoothamnium niveum

Kuphus polythalamia is clearly unable to ingest and digest wood, and lives either on rotten wood or organic rich much, rich in hydrogen sulphide compounds. It appears to ‘feed’ (gain organic carbon) by the action of hydrogen sulphide processing Bacteria, housed in structures present in other members of the group, and used to house wood-digesting endosymbionts in those species. This shows a clear shift from a wood-consuming to a hydrogen sulphide processing ecology, using existing structures for housing endosymbiotic Bacteria, in this species. This lends weight to the theory that this is a more widely followed path, that has enabled a variety of different species from widely separate groups to adopt to a hydrogen sulphide processing lifestyle in this way.

See also...

http://sciencythoughts.blogspot.co.uk/2013/12/a-new-species-of-giant-clam.htmlhttp://sciencythoughts.blogspot.co.uk/2013/09/opportunistic-bivalves-during-early.html
http://sciencythoughts.blogspot.co.uk/2013/06/a-new-species-of-pea-clam-from-miocene.htmlhttp://sciencythoughts.blogspot.co.uk/2012/09/the-evolution-of-galeommatoid-bivalves.html
http://sciencythoughts.blogspot.co.uk/2012/09/symbiosis-and-success-of-galeommatoid.htmlhttp://sciencythoughts.blogspot.co.uk/2012/06/new-species-of-scallop-from-western.html
Follow Sciency Thoughts on Facebook. 

1 comment:

  1. SAYA INGIN BERBAGI CERITA KEPADA SEMUA ORANG BAHWA MUNKIN AKU ADALAH ORANG YANG PALING MISKIN DIDUNIA DAN SAYA HIDUP BERSAMA ISTRI DAN 3 BUAH HATI SAYA SELAMA 10 TAHUN DAN 10 TAHUN ITU KAMI TIDAK PERNAH MERASAKAN YANG NAMANYA KEMEWAHAN,,SETIAP HARI SAYA SELALU MEMBANTIN TULANG BERSAMA SUAMI SAYA UNTUK KELUARGA SAYA NAMUN ITU SEMUA TIDAK PERNAH CUKUP UNTUK KEBUTUHAN HIDUP KELUARGA SAYA..AKHIRNYA AKU PILIH JALAN TOGEL INI DAN SUDAH BANYAK PARA NORMALYANG SAYA HUBUNGI NAMUN ITU SEMUA TIDAK PERNAH MEMBAWAKAN HASIL DAN DISITULAH AKU SEMPAT PUTUS ASA AKHIRNYA ADA SEORANG TEMAN YANG MEMBERIKAN NOMOR AKI ALIH,,SAYA PIKIR TIDAK ADA SALAHNYA JUGA SAYA COBA LAGI UNTUK MENGHUBUNGI AKI ALIH DAN AKHIRNYA AKI ALIH MEMBERIKAN ANGKA GHOIBNYA DAN ALHAMDULILLAH BERHASIL..KINI SAYA SANGAT BERSYUKUR MELIHAT KEHIDUPAN KELUARGA SAYA SUDAH JAUH LEBIH BAIK DARI SEBELUMNYA,DAN TANDA TERIMAH KASIH SAYA KEPADA AKI ALIH SETIAP SAYA DAPAT RUANGAN PASTI SAYA BERKOMENTAR TENTAN AKI ALIH …BAGI ANDA YANG INGIN SEPERTI SAYA SILAHKAN HUBUNGI AKI ALIH: 082==313==669==888

    KLIK BOCORAN ANGKA GAIB 2D 3D 4D 5D 6D


    Sekian lama saya bermain togel baru kali ini saya
    benar-benar merasakan yang namanya kemenangan 4D dan alhamdulillah saya dpat Rp 150 juta dan semuaini
    berkat bantuan angka dari AKI ALIH]
    karena cuma Beliaulah ang memberikan angka
    goibnya yg di jamin 100% tembus awal saya
    bergabung hanya memasang 100 ribu karna
    saya ngak terlalu percaya ternyatah benar-benar
    tembus dan kini saya ngak ragu-ragu lagi untuk memasang
    angkanya,,,,buat anda yg butuh angka yang dijamin tembus
    hubungi AKI ALIH] DI 082==313==669==888
    insya allah beliu akan menbatu k40esusahan
    anda apalagi kalau anda terlilit hutang trima kasih.

    ReplyDelete