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El Albani A, Mazurier A, Edgecombe GD, Azizi A, El Bakhouch A, Berks HO, Bouougri EH, Chraiki I, Donoghue PCJ, Fontaine C, Gaines RR, Ghnahalla M, Meunier A, Trentesaux A, Paterson JR. Rapid volcanic ash entombment reveals the 3D anatomy of Cambrian trilobites. Science 2024; 384:1429-1435. [PMID: 38935712 DOI: 10.1126/science.adl4540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 05/23/2024] [Indexed: 06/29/2024]
Abstract
Knowledge of Cambrian animal anatomy is limited by preservational processes that result in compaction, size bias, and incompleteness. We documented pristine three-dimensional (3D) anatomy of trilobites fossilized through rapid ash burial from a pyroclastic flow entering a shallow marine environment. Cambrian ellipsocephaloid trilobites from Morocco are articulated and undistorted, revealing exquisite details of the appendages and digestive system. Previously unknown anatomy includes a soft-tissue labrum attached to the hypostome, a slit-like mouth, and distinctive cephalic feeding appendages. Our findings resolve controversy over whether the trilobite hypostome is the labrum or incorporates it and establish crown-group euarthropod homologies in trilobites. This occurrence of moldic fossils with 3D soft parts highlights volcanic ash deposits in marine settings as an underexplored source for exceptionally preserved organisms.
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Affiliation(s)
| | - Arnaud Mazurier
- University of Poitiers, UMR CNRS 7285 IC2MP, 86000 Poitiers, France
| | | | - Abdelfattah Azizi
- Laboratory of Geo-resources, Geo-environment and Civil Engineering, Department of Geosciences, Faculty of Sciences and Technics, Cadi Ayyad University, Marrakesh 40000, Morocco
| | - Asmaa El Bakhouch
- Laboratory of Geo-resources, Geo-environment and Civil Engineering, Department of Geosciences, Faculty of Sciences and Technics, Cadi Ayyad University, Marrakesh 40000, Morocco
| | - Harry O Berks
- Bristol Palaeobiology Group, School of Earth Sciences, University of Bristol, Bristol BS8 1TQ, UK
| | - El Hafid Bouougri
- DLGR Laboratory, Department of Geology, Cadi Ayyad University, Faculty of Sciences-Semlalia, Marrakesh 40000, Morocco
| | - Ibtissam Chraiki
- DLGR Laboratory, Department of Geology, Cadi Ayyad University, Faculty of Sciences-Semlalia, Marrakesh 40000, Morocco
| | - Philip C J Donoghue
- Bristol Palaeobiology Group, School of Earth Sciences, University of Bristol, Bristol BS8 1TQ, UK
| | - Claude Fontaine
- University of Poitiers, UMR CNRS 7285 IC2MP, 86000 Poitiers, France
| | - Robert R Gaines
- Department of Geology, Pomona College, Claremont, CA 91711, USA
| | | | - Alain Meunier
- University of Poitiers, UMR CNRS 7285 IC2MP, 86000 Poitiers, France
| | - Alain Trentesaux
- University of Lille, UMR CNRS 8187 LOG, ULCO, 59655 Villeneuve d'Ascq, France
| | - John R Paterson
- Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia
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Nanglu K, Waskom ME, Richards JC, Ortega-Hernández J. Rhabdopleurid epibionts from the Ordovician Fezouata Shale biota and the longevity of cross-phylum interactions. Commun Biol 2023; 6:1002. [PMID: 37821659 PMCID: PMC10567727 DOI: 10.1038/s42003-023-05377-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Accepted: 09/18/2023] [Indexed: 10/13/2023] Open
Abstract
Evidence of interspecific interactions in the fossil record is rare but offers valuable insights into ancient ecologies. Exceptional fossiliferous sites can preserve complex ecological interactions involving non-biomineralized organisms, but most of these examples are restricted to Cambrian Lagerstätten. Here we report an exceptionally preserved cross-phylum interspecific interaction from the Tremadocian-aged Lower Fezouata Shale Formation of Morocco, which consists of the phragmocone of an orthocone cephalopod that has been extensively populated post-mortem by tubicolous epibionts. Well-preserved transverse bands in a zig-zag pattern and crenulations along the margin of the unbranched tubes indicate that they correspond to pterobranch hemichordates, with a close morphological similarity to rhabdopleurids based on the bush-like growth of the dense tubarium. The discovery of rhabdopleurid epibionts in the Fezouata Shale highlights the paucity of benthic graptolites, which also includes the rooted dendroids Didymograptus and Dictyonema, relative to the substantially more diverse and abundant planktic forms known from this biota. We propose that the rarity of Paleozoic rhabdopleurid epibionts is likely a consequence of their ecological requirement for hard substrates for initial settlement and growth. The Fezouata rhabdopleurid also reveals a 480-million-year-old association of pterobranchs as epibionts of molluscs that persist to the present day.
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Affiliation(s)
- Karma Nanglu
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA.
| | - Madeleine E Waskom
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
| | - Jared C Richards
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA
| | - Javier Ortega-Hernández
- Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA.
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Spatially associated or composite life traces from Holocene paleosols and dune sands provide evidence for past biotic interactions. THE SCIENCE OF NATURE - NATURWISSENSCHAFTEN 2023; 110:9. [PMID: 36809360 PMCID: PMC9944729 DOI: 10.1007/s00114-023-01837-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 02/05/2023] [Accepted: 02/06/2023] [Indexed: 02/23/2023]
Abstract
Biotic interactions (e.g., predation, competition, commensalism) where organisms directly or indirectly influenced one another are of great interest to those studying the history of life but have been difficult to ascertain from fossils. Considering the usual caveats about the temporal resolution of paleontological data, traces and trace fossils in the sedimentary record can record co-occurrences of organisms or their behaviours with relatively high spatial fidelity in a location. Neoichnological studies and studies on recently buried traces, where direct trophic links or other connections between tracemakers are well-known, may help interpret when and where overlapping traces represented true biotic interactions. Examples from Holocene paleosols and other buried continental sediments in Poland include the tight association between mole and earthworm burrows, forming an ichnofabric representing a predator-prey relationship, and that of intersecting insect and root traces demonstrating the impact of trees as both ecosystem engineers and the basis for food chains. Trampling by ungulates, which leaves hoofprints and other sedimentary disturbances, may result in amensal or commensal effects on some biota in the short term and create heterogeneity that later trace-making organisms, such as invertebrate burrowers, can also respond to in turn, though such modified or composite traces may be challenging to interpret.
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Nanglu K, Caron JB. Symbiosis in the Cambrian: enteropneust tubes from the Burgess Shale co-inhabited by commensal polychaetes. Proc Biol Sci 2021; 288:20210061. [PMID: 34034516 DOI: 10.1098/rspb.2021.0061] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The in situ preservation of animal behaviour in the fossil record is exceedingly rare, but can lead to unique macroecological and macroevolutionary insights, especially regarding early representatives of major animal clades. We describe a new complex ecological relationship from the middle Cambrian Burgess Shale (Raymond Quarry, Canada). More than 30 organic tubes were recorded with multiple enteropneust and polychaete worms preserved within them. Based on the tubicolous nature of fossil enteropneusts, we suggest that they were the tube builders while the co-preserved polychaetes were commensals. These findings mark, to our knowledge, the first record of commensalism within Annelida and Hemichordata in the entire fossil record. The finding of multiple enteropneusts sharing common tubes suggests that either the tubes represent reproductive structures built by larger adults, and the enteropneusts commonly preserved within are juveniles, or these enteropneusts were living as a pseudo-colony without obligate attachment to each other, and the tube was built collaboratively. While neither hypothesis can be ruled out, gregarious behaviour was clearly an early trait of both hemichordates and annelids. Further, commensal symbioses in the Cambrian may be more common than currently recognized.
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Affiliation(s)
- Karma Nanglu
- Department of Paleobiology, Smithsonian National Museum of Natural History, 10th Street and Constitution Avenue NW, Washington, DC 20560, USA
| | - Jean-Bernard Caron
- Department of Natural History Palaeobiology, Royal Ontario Museum, Toronto, Ontario, Canada M5S 2C6.,Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada M5S 2J7.,Department of Earth Sciences, University of Toronto, Toronto, Ontario, Canada M5S 3B1
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Słowiński J, Surmik D, Duda P, Zatoń M. Assessment of serpulid-hydroid association through the Jurassic: A case study from the Polish Basin. PLoS One 2020; 15:e0242924. [PMID: 33296393 PMCID: PMC7725407 DOI: 10.1371/journal.pone.0242924] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 11/11/2020] [Indexed: 11/25/2022] Open
Abstract
The coexistence of sessile, tube-dwelling polychaetes (serpulids) and hydroids, has been investigated. Serpulid tubes bearing traces after hydroids are derived from different stratigraphic intervals spanning the Middle and Upper Jurassic, the rocks of which represent the diverse paleoenvironments of the Polish Basin. Although fossil colonial hydroids classified under the species Protulophila gestroi are a commonly occurring symbiont of these polychaetes during the Late Cretaceous and Cenozoic, they seem to be significantly less frequent during the Jurassic and limited to specific paleoenvironments. The hydroids described here are represented by traces after a thin stolonal network with elongated polyp chambers that open to the outer polychaete tube's surface with small, more or less subcircular apertures. Small chimney-like bulges around openings are an effect of the incorporation of the organism by in vivo embedment (bioclaustration) within the outer layers of the calcareous tube of the serpulid host. Considering the rich collection of well-preserved serpulid tubes (>3000 specimens), the frequency of bioclaustrated hydroids is very low, with an infestation percentage of only 0.6% (20 cases). It has been noticed that only specimens of the genus Propomatoceros from the Upper Bajocian, Lower Bathonian, Middle Bathonian, and Callovian have been found infested. However, the majority of bioclaustrated hydroids (17 cases) have been recorded in the Middle Bathonian serpulid species Propomatoceros lumbricalis coming from a single sampled site. Representatives of other genera are not affected, which is congruent with previous reports indicating that Protulophila gestroi was strongly selective in the choice of its host. A presumably commensal relationship is compared with the recent symbiosis between the hydroids of the genus Proboscidactyla and certain genera of sabellid polychaetes.
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Affiliation(s)
- Jakub Słowiński
- Institute of Earth Sciences, University of Silesia in Katowice, Sosnowiec, Poland
| | - Dawid Surmik
- Institute of Earth Sciences, University of Silesia in Katowice, Sosnowiec, Poland
| | - Piotr Duda
- Faculty of Computer Science and Materials Science, University of Silesia in Katowice, Chorzów, Poland
| | - Michał Zatoń
- Institute of Earth Sciences, University of Silesia in Katowice, Sosnowiec, Poland
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Zhang Z, Strotz LC, Topper TP, Chen F, Chen Y, Liang Y, Zhang Z, Skovsted CB, Brock GA. An encrusting kleptoparasite-host interaction from the early Cambrian. Nat Commun 2020; 11:2625. [PMID: 32488075 PMCID: PMC7266813 DOI: 10.1038/s41467-020-16332-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 04/28/2020] [Indexed: 12/30/2022] Open
Abstract
Parasite–host systems are pervasive in nature but are extremely difficult to convincingly identify in the fossil record. Here we report quantitative evidence of parasitism in the form of a unique, enduring life association between tube-dwelling organisms encrusted to densely clustered shells of a monospecific organophosphatic brachiopod assemblage from the lower Cambrian (Stage 4) of South China. Brachiopods with encrusting tubes have decreased biomass (indicating reduced fitness) compared to individuals without tubes. The encrusting tubes orient tightly in vectors matching the laminar feeding currents of the host, suggesting kleptoparasitism. With no convincing parasite–host interactions known from the Ediacaran, this widespread sessile association reveals intimate parasite–host animal systems arose in early Cambrian benthic communities and their emergence may have played a key role in driving the evolutionary and ecological innovations associated with the Cambrian radiation. Parasitic interactions are difficult to document in the fossil record. Here, Zhang et al. analyze a large population of a Cambrian brachiopod and show it was frequently encrusted by tubes aligned to its feeding currents and that encrustation was associated with reduced biomass, suggesting a fitness cost.
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Affiliation(s)
- Zhifei Zhang
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, 710069, Xi'an, China.
| | - Luke C Strotz
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, 710069, Xi'an, China.
| | - Timothy P Topper
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, 710069, Xi'an, China. .,Department of Palaeobiology, Swedish Museum of Natural History, SE-10405, Stockholm, Sweden.
| | - Feiyang Chen
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, 710069, Xi'an, China.,Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
| | - Yanlong Chen
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, 710069, Xi'an, China
| | - Yue Liang
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, 710069, Xi'an, China
| | - Zhiliang Zhang
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, 710069, Xi'an, China.,Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
| | - Christian B Skovsted
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, 710069, Xi'an, China.,Department of Palaeobiology, Swedish Museum of Natural History, SE-10405, Stockholm, Sweden
| | - Glenn A Brock
- State Key Laboratory of Continental Dynamics, Shaanxi Key Laboratory of Early Life & Environments and Department of Geology, Northwest University, 710069, Xi'an, China.,Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
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Audo D, Robin N, Luque J, Krobicki M, Haug JT, Haug C, Jauvion C, Charbonnier S. Palaeoecology of Voulteryon parvulus (Eucrustacea, Polychelida) from the Middle Jurassic of La Voulte-sur-Rhône Fossil-Lagerstätte (France). Sci Rep 2019; 9:5332. [PMID: 30926859 PMCID: PMC6441058 DOI: 10.1038/s41598-019-41834-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 03/18/2019] [Indexed: 11/08/2022] Open
Abstract
Exceptional and extremely rare preservation of soft parts, eyes, or syn-vivo associations provide crucial palaeoecological information on fossil-rich deposits. Here we present exceptionally preserved specimens of the polychelidan lobster Voulteryon parvulus, from the Jurassic of La Voulte-sur-Rhône Fossil-Lagerstätte, France, bearing eyes with hexagonal and square facets, ovaries, and a unique association with epibiont thecideoid brachiopods, giving insights onto the palaeoenvironment of this Lagerstätte. The eyes, mostly covered in hexagonal facets are interpreted as either apposition eyes (poorly adapted to low-light environment) or, less likely, as refractive or parabolic superposition eyes (compatible with dysphotic palaeoenvironments). The interpretation that V. parvulus had apposition eyes suggests an allochthonous, shallow water origin. However, the presence of thecideoid brachiopod ectosymbionts on its carapace, usually associated to dim-light paleoenvironments and/or rock crevices, suggests that V. parvulus lived in a dim-light setting. This would support the less parsimonious interpretation that V. parvulus had superposition eyes. If we accept the hypothesis that V. parvulus had apposition eyes, since the La Voulte palaeoenvironment is considered deep water and had a soft substrate, V. parvulus could have moved into the La Voulte Lagerstätte setting. If this is the case, La Voulte biota would record a combination of multiple palaeoenvironments.
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Affiliation(s)
- Denis Audo
- Yunnan Key Laboratory for Palaeobiology, Yunnan University, North Cuihu road 2#, 650091, Kunming, China.
- MEC International Joint Laboratory for Palaeobiology and Palaeoenvironment, Yunnan University, Kunming, China.
| | - Ninon Robin
- Centre de Recherche en Paléontologie - Paris (UMR 7207), CNRS-MNHN-Sorbonne Université, Muséum national d'Histoire naturelle, Département Origines & Evolution, (CP 38), 8, rue Buffon, F-75005, Paris, France
| | - Javier Luque
- Department of Geology and Geophysics, Yale University, New Haven, CT, 06520-8109, USA
- Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada
| | - Michal Krobicki
- Department of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, Mickiewicza 30, 30-059, Kraków, Poland
| | - Joachim T Haug
- LMU Munich, Department of Biology II and GeoBio-Center, Großhaderner Str. 2, 82152, Martinsried-Planegg, Germany
| | - Carolin Haug
- LMU Munich, Department of Biology II and GeoBio-Center, Großhaderner Str. 2, 82152, Martinsried-Planegg, Germany
| | - Clément Jauvion
- Centre de Recherche en Paléontologie - Paris (UMR 7207), CNRS-MNHN-Sorbonne Université, Muséum national d'Histoire naturelle, Département Origines & Evolution, (CP 38), 8, rue Buffon, F-75005, Paris, France
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC, UMR 7590), Muséum National d'Histoire Naturelle, Sorbonne Université, CNRS, IRD, 57 rue Cuvier, F-75005, Paris, France
| | - Sylvain Charbonnier
- Centre de Recherche en Paléontologie - Paris (UMR 7207), CNRS-MNHN-Sorbonne Université, Muséum national d'Histoire naturelle, Département Origines & Evolution, (CP 38), 8, rue Buffon, F-75005, Paris, France
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Leung TLF. Fossils of parasites: what can the fossil record tell us about the evolution of parasitism? Biol Rev Camb Philos Soc 2015; 92:410-430. [PMID: 26538112 DOI: 10.1111/brv.12238] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 10/09/2015] [Accepted: 10/12/2015] [Indexed: 01/20/2023]
Abstract
Parasites are common in many ecosystems, yet because of their nature, they do not fossilise readily and are very rare in the geological record. This makes it challenging to study the evolutionary transition that led to the evolution of parasitism in different taxa. Most studies on the evolution of parasites are based on phylogenies of extant species that were constructed based on morphological and molecular data, but they give us an incomplete picture and offer little information on many important details of parasite-host interactions. The lack of fossil parasites also means we know very little about the roles that parasites played in ecosystems of the past even though it is known that parasites have significant influences on many ecosystems. The goal of this review is to bring attention to known fossils of parasites and parasitism, and provide a conceptual framework for how research on fossil parasites can develop in the future. Despite their rarity, there are some fossil parasites which have been described from different geological eras. These fossils include the free-living stage of parasites, parasites which became fossilised with their hosts, parasite eggs and propagules in coprolites, and traces of pathology inflicted by parasites on the host's body. Judging from the fossil record, while there were some parasite-host relationships which no longer exist in the present day, many parasite taxa which are known from the fossil record seem to have remained relatively unchanged in their general morphology and their patterns of host association over tens or even hundreds of millions of years. It also appears that major evolutionary and ecological transitions throughout the history of life on Earth coincided with the appearance of certain parasite taxa, as the appearance of new host groups also provided new niches for potential parasites. As such, fossil parasites can provide additional data regarding the ecology of their extinct hosts, since many parasites have specific life cycles and transmission modes which reflect certain aspects of the host's ecology. The study of fossil parasites can be conducted using existing techniques in palaeontology and palaeoecology, and microscopic examination of potential material such as coprolites may uncover more fossil evidence of parasitism. However, I also urge caution when interpreting fossils as examples of parasites or parasitism-induced traces. I point out a number of cases where parasitism has been spuriously attributed to some fossil specimens which, upon re-examination, display traits which are just as (if not more) likely to be found in free-living taxa. The study of parasite fossils can provide a more complete picture of the ecosystems and evolution of life throughout Earth's history.
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Affiliation(s)
- Tommy L F Leung
- Department of Zoology Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, New South Wales 2351, Australia
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Topper TP, Strotz LC, Holmer LE, Zhang Z, Tait NN, Caron JB. Competition and mimicry: the curious case of chaetae in brachiopods from the middle Cambrian Burgess Shale. BMC Evol Biol 2015; 15:42. [PMID: 25886965 PMCID: PMC4477600 DOI: 10.1186/s12862-015-0314-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 02/23/2015] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND One of the first phyla to acquire biomineralized skeletal elements in the Cambrian, brachiopods represent a vital component in unraveling the early evolution and relationships of the Lophotrochozoa. Critical to improving our understanding of lophotrochozoans is the origin, evolution and function of unbiomineralized morphological features, in particular features such as chaetae that are shared between brachiopods and other lophotrochozoans but are poorly understood and rarely preserved. Micromitra burgessensis and Paterina zenobia from the middle Cambrian Burgess Shale are among the most remarkable examples of fossilized chaetae-bearing brachiopods. The form, functional morphology, evolutionary and ecological significance of their chaetae are studied herein. RESULTS Like in Recent forms, the moveable but semi-rigid chaetae fringe both the dorsal and ventral mantle margins, but in terms of length, the chaetae of Burgess Shale taxa can exceed twice the maximum length of the shell from which it projects. This is unique amongst Recent and fossil brachiopod taxa and given their size, prominence and energy investment to the organism certainly had an important functional significance. Micromitra burgessensis individuals are preserved on hard skeletal elements, including conspecific shells, Tubulella and frequently on the spicules of the sponge Pirania muricata, providing direct evidence of an ecological association between two species. Morphological analysis and comparisons with fossil and extant brachiopod chaetae point to a number of potential functions, including sensory, defence, feeding, defouling, mimicry and spatial competition. CONCLUSIONS Our study indicates that it is feasible to link chaetae length to the lack of suitable substrate in the Burgess Shale environment and the increased intraspecific competition associated with this. Our results however, also lend support to the elongated chaetae as an example of Batesian mimicry, of the unpalatable sponge Pirania muricata. We also cannot discount brachiopod chaetae acting as a sensory grille, extending the tactile sensitivity of the mantle into the environment, as an early warning system to approaching predators.
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Affiliation(s)
- Timothy P Topper
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, SE - 752 36, Uppsala, Sweden.
- Department of Palaeobiology, Swedish Museum of Natural History, P.O. Box 50007, , SE-104 05, Stockholm, Sweden.
| | - Luke C Strotz
- Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia.
| | - Lars E Holmer
- Department of Earth Sciences, Palaeobiology, Uppsala University, Villavägen 16, SE - 752 36, Uppsala, Sweden.
| | - Zhifei Zhang
- Early Life Institute and Department of Geology, State Key Laboratory for Continental Dynamics, Northwest University, Xian, 710069, China.
| | - Noel N Tait
- Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia.
| | - Jean-Bernard Caron
- Department of Natural History (Palaeobiology Section), Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, M5S2C6, Canada.
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, M5S3B2, Canada.
- Department of Earth Sciences, University of Toronto, 22 Russell Street, Toronto, Ontario, M5S3B1, Canada.
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