| title: | Tube formation and bomineralization in annelids, its evolutionary and ecological implications |
|---|---|
| reg no: | ETF6623 |
| project type: | Estonian Science Foundation research grant |
| subject: |
1.10. Geology 1.14. Ecology 1.15. Zoology |
| status: | accepted |
| institution: | TU Faculty of Biology and Geography |
| head of project: | Olev Vinn |
| duration: | 01.01.2006 - 31.12.2008 |
| description: | Calcifying annelids are very important group of animals in the Oceanic calcium sink, especially in temperate sees where they can be major calcifying invertebrates (Mastrangelo & Passeri 1975, Medernach et al. 2000). Some serpulids are economically important due to intensive biofouling of artificial substrates in the sea. Isotopic analyses have been applied to study the stable-isotope composition of serpulid tubes to give insight in calcification processes in marine organisms (Videtich, 1986). Serpulid tubes have been studied with plasma mass spectroscopy (IPC-MS) to analysethe anthropogenitically mobilized metal content (e.g. Al, Cd, Ni, Pb, U, etc.), to estimate the humane impact on the coastal environment in California. Surprisingly, fossil tubes were showing the highest content of metals, interpreted as the result of surface contamination (Reish & Mason, 2003). Skeletal formation and biomineralization has been extensively studied in various invertebrates, but mostly in molluscs and brachiopods (Carter et al. 1990). Very little is known on the biomineralization and skeletal structures in recent calcifying annelids (Neff 1971, Simkiss & Wilbur 1989). The composition of serpulid tubes is thought to be either calcitic, aragonitic or a combination of calcite and aragonite (Simkiss & Wilbur 1989, Vovelle et al. 1991). There are cycles of carbonate sedimentation in the Phanerozoic Ocean corresponding to periods of calcite and aragonite Ocean (Wilkinson & Walker1989). These cycles may or may not be in correlation with the different calcification events of annelids ((Permian?)Triassic-serpulids; Jurassic?- sabellids, Miocene (Late Cretaceous?)-cirratulids)(ongoing research by: O. Vinn & P.D. Taylor). One should study also the possible influence of these cycles of carbonate sedimentation to the dominate mineralogy of serpulids. Biomineralization of serpulid worms is thought to be reflecting the temperature of the environment (Lowenstam, 1954; Lowenstam & Weimer, 1989; Burton & Walter, 1987), however, based on a single species Hydroides gracilis (as Eupomatus). Railsback (1993, 1994) has therefore placed serpulid polychaetes among the bioinduced biomineralizers sensu Lowenstam and Weimer (1989). However, the latter opinion has been questioned by Weedon and Taylor (1994). Overall diversity of possible ways of skeletal formation as well as its structures is not known in recent calcifying annelids, so is potential for the ecological studies or taxonomy. Recently the structure and skeletal formation of cirratulid polychaetes (Fischer et al. 2000) and the only calcifying sabellid polychaete -Calcisabella (Vinn, ten Hove & Mutvei, submitted to ‘Acta Zoologica’) has been described. Numerous new skeletal ultrastructures of serpulid polychaetes have been discovered recently, some not supporting the present understanding of their biomineralization and skeletal secretion (classical Hedley model)(ongoing research by: O. Vinn, H. Mutvei, H.A. ten Hove & P. D. Taylor). New models of their tube formation and biomineralization are in phase of developing (ongoing research by: O. Vinn & H. Mutvei). Serpulid polycheates tubes are not separated externally form the seawater by thick organic layer as the periostracum in molluscs and brachiopods. Some particular structures found in their tubes may be resulted from the short term diagenesis, possible due to activity of micro-organisms inside the tube walls of living worms. Early diagenesis of serpulid tubes may alter their ultrastrucutre (important for taxonomy worm tubes) and chemical as well as isotopical composition (important for applied environmental research). This may cause problems in using the serpulid tubes as the recorders of chemical and isotopic changes in the seawater (ongoing research by: O. Vinn, H.A. ten Hove and Harry Mutvei). Ultrastructure and ontogenesis of problematic Palaeozoic tubeworm-like fossils (e.g. cornulitids, tentaculitids, microconchids (=Palaeozoic ‘spirorbids’), trypanoporids, Tymbochoos, and problematic gastropod-Anticalyptraea) is very different from the Mesozoic and Recent serpulid polychaetes (Weedon 1994, ongoing research by: O. Vinn, H. Mutvei, H.A. ten Hove & P. D. Taylor). According to our hypothesis the Palaeozoic tubeworm-like fossils belong to extinct group of lophophor bearing worms unrelated to annelids and the real serpulid polychaetes first appeared in Early Triassic. The non-annelid ‘Palaeozoic tubeworms’ mostly did not survive Permian-Triassic extinction and finally became gradually extinct by Late Jurassic (Weedon 1991, Vinn & Mutvei 2005, Vinn 2005, Vinn in press, Taylor & Vinn submitted to ‘Geology’, ongoing research by: O. Vinn, H. Mutvei, H.A. ten Hove & P. D. Taylor). The goals of the project are: (1) To map the shell ultrastructure in major groups of extinct calcifying annelids, from each geological periods, in aim to compile preliminary overview on diversity of their structures and reconstruct their phylogeny. (2) To find palaeontological evidence for the first appearance of calcifying annelids (serpulids and sabellids) in the geological record. (3) To map the main skeletal structures of recent calcifying annelids in aim to use it in generic level systematics of worm tubes. (4) To establish new secretion models describing the annelid structures not explained by the classical carbonate slurry model (Hedley model). (5) To study the possibility of early diagenetic changes in serpulid polychaetes tubes structure and mineralogy. (6) To study whether the calcifying annelids gradually took over the ecological niche of Palaeozoic non-annelid worms or their radiation took place after the Permian-Triassic major extinction event. (7) To study whether the skeletizations events of main calcifying annelids are correlated with the major changes in marine chemistry (calcitic versus aragonitic oceans) (8) To use the skeletal ultrastructure and formation for identifying calcifying annelids (serpulids-spirorbids, cirratulids, sabellids) and non-annelid worms (e.g. cornulitids, tentaculitids, microconchids, trypanoporids etc.). |
| project group | ||||
|---|---|---|---|---|
| no | name | institution | position | |
| 1. | Mare Isakar | |||
| 2. | Olev Vinn | Tartu Ülikool | ||