Frenulata, "beard worms", is a clade of Siboglinidae, "tube worms". They are one of four lineages with numerous species.[1][2] They may be the most basal clade in the family.[3] Despite being the first tube worms to be encountered and described, they remain the least studied group. This is because of their slender shape, they often get destroyed as a result of being caught as bycatch or poor preservation. They are found primarily in deep, muddy sediments, cold seeps, and anoxic firth sediments.[4][5]
| Frenulata | |
|---|---|
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Annelida |
| Clade: | Pleistoannelida |
| Clade: | Sedentaria |
| Order: | Sabellida |
| Family: | Siboglinidae |
| Clade: | Frenulata |
Anatomy
editFrenulata are typically long and slender, they have been described as "thread-like".[5] They typically range from 0.1–3 mm in diameter.[6] Like other Siboglinidae, they have distinct segments: a plume, a vestimentum, and a trophosome. The vestimentum is used to retract the organism in and out of its tube. The trophosome is unique to tube worms. It was found to house bacterial symbiotes in Riftia.[7] Like other tube worms, they lack a digestive tract.[8] In order to survive, it holds endosymbiotic bacteria that supply the worm with nutrients. The bacteria nourishes the worm by oxidizing sulfur from its surrounding environment, with one methanotrophic exception being Siboglinum poseidoni.[5] The inorganic compounds are delivered to the trophosome by both the vascular and coelomic systems. Frenulata are unique in that they all have a mid-trunk girdle, spermatophores, sparse peg-like chaetae, and a tube with the posterior end open.[9][10] The tube serves to provide structure for this soft-bodied animal as well as place the organism in an optimal position to obtain nutrients.[11]
Ecology
editFrenulata are one of four clades of Siboglinidae, they are also the most diverse.[12] Despite that, the endosymbiotic bacterial diversity remains largely unknown due to their small size and difficult to reach habitats. They often serve as environmental engineers with their tubes, changing the composition of the sediment.[13] There is evidence that they are symbiote-flexible, meaning they can utilize different species of bacteria in order to best adapt to their environments. This however is still a contested theory with conflicting reports.[5][11]
References
edit- ^ Southward, Eve C.; Schulze, Anja; Gardiner, Stephen L. (2005). "Pogonophora (Annelida): form and function". Hydrobiologia. 535–536 (1): 227–251. doi:10.1007/s10750-004-4401-6. ISSN 0018-8158. S2CID 2057727.
- ^ Kubota, Norihiro; Kanemori, Masaaki; Sasayama, Yuichi; Aida, Masato; Fukumori, Yoshihiro (2007). "Identification of Endosymbionts in Oligobrachia mashikoi (Siboglinidae, Annelida)". Microbes and Environments. 22 (2): 136–144. doi:10.1264/jsme2.22.136. hdl:2297/12422. ISSN 1342-6311. S2CID 84629870.
- ^ Hilário, Ana; Capa, María; Dahlgren, Thomas G.; Halanych, Kenneth M.; Little, Crispin T. S.; Thornhill, Daniel J.; Verna, Caroline; Glover, Adrian G. (2011). "New Perspectives on the Ecology and Evolution of Siboglinid Tubeworms". PLOS ONE. 6 (2): e16309. Bibcode:2011PLoSO...616309H. doi:10.1371/journal.pone.0016309. PMC 3038861. PMID 21339826.
- ^ Rodrigues, Clara F.; Hilário, Ana; Cunha, Marina R.; Weightman, Andrew J.; Webster, Gordon (2011-06-01). "Microbial diversity in Frenulata (Siboglinidae, Polychaeta) species from mud volcanoes in the Gulf of Cadiz (NE Atlantic)". Antonie van Leeuwenhoek. 100 (1): 83–98. doi:10.1007/s10482-011-9567-0. ISSN 1572-9699. PMID 21359663. S2CID 10224623.
- ^ a b c d Meunier, Cédric; Andersen, Ann C.; Bruneaux, Matthieu; Le Guen, Dominique; Terrier, Peran; Leize-Wagner, Emmanuelle; Zal, Franck (2010-01-01). "Structural characterization of hemoglobins from Monilifera and Frenulata tubeworms (Siboglinids): First discovery of giant hexagonal-bilayer hemoglobin in the former "Pogonophora" group". Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology. 155 (1): 41–48. doi:10.1016/j.cbpa.2009.09.010. ISSN 1095-6433. PMID 19770067.
- ^ Pleijel, Fredrik; Dahlgren, Thomas G.; Rouse, Greg W. (2009). "Progress in systematics: from Siboglinidae to Pogonophora and Vestimentifera and back to Siboglinidae". Comptes Rendus Biologies. 332 (2–3): 140–148. doi:10.1016/j.crvi.2008.10.007. PMID 19281947.
- ^ Katz, Sigrid; Klepal, Waltraud; Bright, Monika (2011). "The Osedax Trophosome: Organization and Ultrastructure". The Biological Bulletin. 220 (2): 128–139. doi:10.1086/BBLv220n2p128. ISSN 0006-3185. PMID 21551449. S2CID 20054373.
- ^ Rouse, Greg W. (2001). "A cladistic analysis of Siboglinidae Caullery, 1914 (Polychaeta, Annelida): formerly the phyla Pogonophora and Vestimentifera". Zoological Journal of the Linnean Society. 132 (1): 55–80. doi:10.1111/j.1096-3642.2001.tb02271.x. S2CID 85356739.
- ^ Halanych, Kenneth M. (2005). "Molecular phylogeny of siboglinid annelids (a.k.a. pogonophorans): a review". Hydrobiologia. 535–536 (1): 297–307. doi:10.1007/s10750-004-1437-6. ISSN 0018-8158. S2CID 16022909.
- ^ Karaseva, N. P.; Rimskaya-Korsakova, N. N.; Ekimova, I. A.; Gantsevich, M. M.; Kokarev, V. N.; Kremnyov, S. V.; Simakov, M. I.; Udalov, A. A.; Vedenin, A. A.; Malakhov, V. V. (2021-11-05). "A new genus of frenulates (Annelida: Siboglinidae) from shallow waters of the Yenisey River estuary, Kara Sea". Invertebrate Systematics. 35 (8): 857–875. doi:10.1071/IS20075. ISSN 1445-5226. S2CID 244151933.
- ^ a b Lee, Dh; Kim, Jh; Lee, Ym; Jin, Yk; Paull, C; Kim, D; Shin, Kh (2019-10-10). "Chemosynthetic bacterial signatures in Frenulata tubeworm Oligobrachia sp. in an active mud volcano of the Canadian Beaufort Sea". Marine Ecology Progress Series. 628: 95–104. Bibcode:2019MEPS..628...95L. doi:10.3354/meps13084. ISSN 0171-8630. S2CID 201194903.
- ^ Schulze, Anja (2003). "Phylogeny of Vestimentifera (Siboglinidae, Annelida) inferred from morphology". Zoologica Scripta. 32 (4): 321–342. doi:10.1046/j.1463-6409.2003.00119.x. ISSN 0300-3256. S2CID 84679292.
- ^ Lee, Yung Mi; Noh, Hyun-Ju; Lee, Dong-Hun; Kim, Jung-Hyun; Jin, Young Keun; Paull, Charles (2019). "Bacterial endosymbiont of Oligobrachia sp. (Frenulata) from an active mud volcano in the Canadian Beaufort Sea". Polar Biology. 42 (12): 2305–2312. Bibcode:2019PoBio..42.2305L. doi:10.1007/s00300-019-02599-w. ISSN 0722-4060. S2CID 207987760.