Vertically migrating
            Isoxys
            and the early Cambrian biological pump

The biological pump is crucial for transporting nutrients fixed by surface-dwelling primary producers to demersal animal communities. Indeed, the establishment of an efficient biological pump was likely a key factor enabling the diversification of animals over 500 Myr ago during the Cambrian explosion. The modern biological pump operates through two main vectors: the passive sinking of aggregates of organic matter, and the active vertical migration of animals. The coevolution of eukaryotes and sinking aggregates is well understood for the Proterozoic and Cambrian; however, little attention has been paid to the establishment of the vertical migration of animals. Here we investigate the morphological variation and hydrodynamic performance of the Cambrian euarthropod Isoxys . We combine elliptical Fourier analysis of carapace shape with computational fluid dynamics simulations to demonstrate that Isoxys species likely occupied a variety of niches in Cambrian oceans, including vertical migrants, providing the first quantitative evidence that some Cambrian animals were adapted for vertical movement in the water column. Vertical migration was one of several early Cambrian metazoan innovations that led to the biological pump taking on a modern-style architecture over 500 Myr ago.

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Current understanding on the Cambrian Explosion: questions and answers

PalZ ◽

10.1007/s12542-021-00568-5 ◽

2021 ◽

Author(s):

Xingliang Zhang ◽

Degan Shu

Keyword(s):

Environmental Changes ◽

Size Variation ◽

Progressive Increase ◽

Cambrian Explosion ◽

Time Interval ◽

Early Cambrian ◽

Ecological Processes ◽

Questions And Answers ◽

Evolutionary Event ◽

History Of

AbstractThe Cambrian Explosion by nature is a three-phased explosion of animal body plans alongside episodic biomineralization, pulsed change of generic diversity, body size variation, and progressive increase of ecosystem complexity. The Cambrian was a time of crown groups nested by numbers of stem groups with a high-rank taxonomy of Linnaean system (classes and above). Some stem groups temporarily succeeded while others were ephemeral and underrepresented by few taxa. The high number of stem groups in the early history of animals is a major reason for morphological gaps across phyla that we see today. Most phylum-level clades achieved their maximal disparity (or morphological breadth) during the time interval close to their first appearance in the fossil record during the early Cambrian, whereas others, principally arthropods and chordates, exhibit a progressive exploration of morphospace in subsequent Phanerozoic. The overall envelope of metazoan morphospace occupation was already broad in the early Cambrian though it did not reach maximal disparity nor has diminished significantly as a consequence of extinction since the Cambrian. Intrinsic and extrinsic causes were extensively discussed but they are merely prerequisites for the Cambrian Explosion. Without the molecular evolution, there could be no Cambrian Explosion. However, the developmental system is alone insufficient to explain Cambrian Explosion. Time-equivalent environmental changes were often considered as extrinsic causes, but the time coincidence is also insufficient to establish causality. Like any other evolutionary event, it is the ecology that make the Cambrian Explosion possible though ecological processes failed to cause a burst of new body plans in the subsequent evolutionary radiations. The Cambrian Explosion is a polythetic event in natural history and manifested in many aspects. No simple, single cause can explain the entire phenomenon.

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Decoupled evolution of soft and hard substrate communities during the Cambrian Explosion and Great Ordovician Biodiversification Event

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1523087113 ◽

2016 ◽

Vol 113 (25) ◽

pp. 6945-6948 ◽

Cited By ~ 45

Author(s):

Luis A. Buatois ◽

Maria G. Mángano ◽

Ricardo A. Olea ◽

Mark A. Wilson

Keyword(s):

Late Ordovician ◽

Hard Substrate ◽

Cambrian Explosion ◽

Early Cambrian ◽

Continuous Increase ◽

Late Cambrian ◽

Unconsolidated Sediment ◽

Underlying Causes ◽

Hard Substrates ◽

Shed Light

Contrasts between the Cambrian Explosion (CE) and the Great Ordovician Biodiversification Event (GOBE) have long been recognized. Whereas the vast majority of body plans were established as a result of the CE, taxonomic increases during the GOBE were manifested at lower taxonomic levels. Assessing changes of ichnodiversity and ichnodisparity as a result of these two evolutionary events may shed light on the dynamics of both radiations. The early Cambrian (series 1 and 2) displayed a dramatic increase in ichnodiversity and ichnodisparity in softground communities. In contrast to this evolutionary explosion in bioturbation structures, only a few Cambrian bioerosion structures are known. After the middle to late Cambrian diversity plateau, ichnodiversity in softground communities shows a continuous increase during the Ordovician in both shallow- and deep-marine environments. This Ordovician increase in bioturbation diversity was not paralleled by an equally significant increase in ichnodisparity as it was during the CE. However, hard substrate communities were significantly different during the GOBE, with an increase in ichnodiversity and ichnodisparity. Innovations in macrobioerosion clearly lagged behind animal–substrate interactions in unconsolidated sediment. The underlying causes of this evolutionary decoupling are unclear but may have involved three interrelated factors: (i) a Middle to Late Ordovician increase in available hard substrates for bioerosion, (ii) increased predation, and (iii) higher energetic requirements for bioerosion compared with bioturbation.

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Study on the Motion Stability of the Autonomous Underwater Helicopter

Journal of Marine Science and Engineering ◽

10.3390/jmse10010060 ◽

2022 ◽

Vol 10 (1) ◽

pp. 60

Author(s):

Yuan Lin ◽

Jin Guo ◽

Haonan Li ◽

Hai Zhu ◽

Haocai Huang ◽

...

Keyword(s):

Autonomous Underwater Vehicle ◽

Angle Of Attack ◽

Vertical Movement ◽

Plane Motion ◽

Hydrodynamic Performance ◽

Scale Model ◽

Motion Stability ◽

Movement Stability ◽

Stability Indexes ◽

Drag Ratio

The hydrodynamic performance of a novel hovering autonomous underwater vehicle, the autonomous underwater helicopter (AUH), with an original disk-shaped hull (HG1) and an improved fore–aft asymmetric hull (HG3), is investigated by means of computational fluid dynamics with the adoption of overlapping mesh method. The hydrodynamic performance of the two hull shapes in surge motion with variation of the angle of attack is compared. The results show that HG3 has less resistance and higher motion stability compared to HG1. With the angle of attack reaching 10 degrees, both HG1 and HG3 achieve the maximum lift-to-drag ratio, which is higher for HG3 compared to HG1. Furthermore, based on the numerical simulation of the plane motion mechanism test (PMM) and according to Routh’s stability criterion, the horizontal movement and vertical movement stability indexes of HG1 and HG3 (GHHG1=1.0, GVHG1=49.7, GHHG2=1.0, GVHG3=2.1) are obtained, which further show that the AUH has better vertical movement stability than the torpedo-shaped AUV. Furthermore, the scale model tail velocity experiment indirectly shows that HG3 has better hydrodynamic performance than HG1.

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Brachiopod-dominated communities and depositional environment of the Guanshan Konservat-Lagerstätte, eastern Yunnan, China

Journal of the Geological Society ◽

10.1144/jgs2020-043 ◽

2020 ◽

Vol 178 (1) ◽

pp. jgs2020-043 ◽

Cited By ~ 1

Author(s):

Feiyang Chen ◽

Glenn A. Brock ◽

Zhiliang Zhang ◽

Brittany Laing ◽

Xinyi Ren ◽

...

Keyword(s):

Depositional Environment ◽

Sedimentary Environment ◽

Low Energy ◽

Cambrian Explosion ◽

Early Cambrian ◽

Tissue Preservation ◽

Content Type ◽

Guanshan Biota ◽

Supplementary Material ◽

Later Phase

The Guanshan Biota is an unusual early Cambrian Konservat-Lagerstätte from China and is distinguished from all other exceptionally preserved Cambrian biotas by the dominance of brachiopods and a relatively shallow depositional environment. However, the faunal composition, overturn and sedimentology associated with the Guanshan Biota are poorly understood. This study, based on collections through the best-exposed succession of the basal Wulongqing Formation at the Shijiangjun section, Wuding County, eastern Yunnan, China recovered six major animal groups with soft tissue preservation; brachiopods vastly outnumbered all other groups. Brachiopods quickly replace arthropods as the dominant fauna following a transgression at the base of the Wulongqing Formation. A transition from a botsfordiid-, eoobolid- and acrotretid- to an acrotheloid-dominated brachiopod assemblage occurs up-section. Four episodically repeated lithofacies reveal a relatively low-energy, offshore to lower shoreface sedimentary environment at the Shijiangjun section, which is very different from the Wulongqing Formation in the Malong and Kunming areas. Multiple event flows and rapid obrution are responsible for faunal overturn and fluctuation through the section. A detailed lithofacies and palaeontological investigation of this section provides a better understanding of the processes and drivers of faunal overturn during the later phase of the Cambrian Explosion.Supplementary material: Composition and comparison of the Malong Fauna and the Guanshan Biota is are available at: https://doi.org/10.6084/m9.figshare.c.5080799

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Caught in the act: priapulid burrowers in early Cambrian substrates

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2018.2505 ◽

2019 ◽

Vol 286 (1894) ◽

pp. 20182505 ◽

Cited By ~ 9

Author(s):

Giannis Kesidis ◽

Ben J. Slater ◽

Sören Jensen ◽

Graham E. Budd

Keyword(s):

Comparative Analysis ◽

Lower Cambrian ◽

Trace Fossil ◽

Considerable Importance ◽

Cambrian Explosion ◽

Early Cambrian ◽

Southern Sweden ◽

Stage 4 ◽

Organic Remains

The fossilized traces of burrowing worms have taken on a considerable importance in studies of the Cambrian explosion, partly because of their use in defining the base of the Cambrian. Foremost among these are the treptichnids, a group of relatively large open probing burrows that have sometimes been assigned to the activities of priapulid scalidophoran worms. Nevertheless, most Cambrian burrows have an uncertain progenitor. Here we report a suite of exceptionally preserved trace and body fossils from sandstones of the lower Cambrian (Stage 4) File Haidar Formation of southern Sweden that can unequivocally be assigned to a scalidophoran producer. We further present the first burrow casts produced via actualistic experiments on living priapulids, and demonstrate the remarkable morphological parallels between these modern and Cambrian fossil equivalents. In addition, co-occurrence of scalidophoran-derived cuticular remains permits a unique synthesis of evidence from trace fossil, body and organic remains. Comparative analysis of these exceptionally preserved fossils supports a scalidophoran producer for treptichnids and by extension suggests a latest Ediacaran origin of the ecdysozoan clade.

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A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1505596112 ◽

2015 ◽

Vol 112 (28) ◽

pp. 8678-8683 ◽

Cited By ~ 47

Author(s):

Jie Yang ◽

Javier Ortega-Hernández ◽

Sylvain Gerber ◽

Nicholas J. Butterfield ◽

Jin-bo Hou ◽

...

Keyword(s):

South China ◽

Cambrian Explosion ◽

Suspension Feeding ◽

Early Cambrian ◽

Early Paleozoic ◽

Crown Group ◽

Morphological Disparity ◽

Stem Group ◽

Velvet Worms ◽

Mode Of Life

We describe Collinsium ciliosum from the early Cambrian Xiaoshiba Lagerstätte in South China, an armored lobopodian with a remarkable degree of limb differentiation including a pair of antenna-like appendages, six pairs of elongate setiferous limbs for suspension feeding, and nine pairs of clawed annulated legs with an anchoring function. Collinsium belongs to a highly derived clade of lobopodians within stem group Onychophora, distinguished by a substantial dorsal armature of supernumerary and biomineralized spines (Family Luolishaniidae). As demonstrated here, luolishaniids display the highest degree of limb specialization among Paleozoic lobopodians, constitute more than one-third of the overall morphological disparity of stem group Onychophora, and are substantially more disparate than crown group representatives. Despite having higher disparity and appendage complexity than other lobopodians and extant velvet worms, the specialized mode of life embodied by luolishaniids became extinct during the Early Paleozoic. Collinsium and other superarmored lobopodians exploited a unique paleoecological niche during the Cambrian explosion.

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Trilobites in early Cambrian tidal flats and the landward expansion of the Cambrian Explosion: REPLY

Geology ◽

10.1130/g35817y.1 ◽

2014 ◽

Vol 42 (9) ◽

pp. e343-e343 ◽

Cited By ~ 1

Author(s):

M. Gabriela Mángano ◽

Luis A. Buatois ◽

Ricardo Astini ◽

Andrew K. Rindsberg

Keyword(s):

Tidal Flats ◽

Cambrian Explosion ◽

Early Cambrian

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Vertical migration in adult Atlantic cod (Gadus morhua)

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f07-135 ◽

2007 ◽

Vol 64 (12) ◽

pp. 1747-1760 ◽

Cited By ~ 25

Author(s):

Espen Strand ◽

Geir Huse

Keyword(s):

Vertical Migration ◽

Gadus Morhua ◽

Atlantic Cod ◽

Pelagic Zone ◽

Neutral Buoyancy ◽

Visual Predation ◽

Trade Offs ◽

Key Factor ◽

Pelagic Prey ◽

Benthic Prey

We investigate the trade-offs associated with vertical migration and swimming speed of Atlantic cod (Gadus morhua) using an adaptive individual-based model. Simulations with varying distribution and occurrence of prey, with and without swimbladder constraints, and visual predation were performed. Most simulations resulted in cod migrations between the bottom and pelagic zones. In simulations with high probability of encountering pelagic prey, the cod spent the daytime in the pelagic zone, moving to the bottom to feed only when no pelagic prey were encountered. At night the cod stayed in the pelagic zone to attain neutral buoyancy. In simulations with low occurrence of pelagic prey or high visual predation pressure, the cod remained at the bottom feeding on the consistently present benthic prey. If the pelagic prey occurred far above the sea floor or there were no benthic prey, the cod abandoned all bottom contact. The study thus predicts that the probability of encountering energy-rich pelagic prey is the key factor in driving vertical migration in adult cod. Buoyancy regulation is further shown to be an important constraint on vertical migration.

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Plankton ecology and the Proterozoic-Phanerozoic transition

Paleobiology ◽

10.1017/s009483730001681x ◽

1997 ◽

Vol 23 (2) ◽

pp. 247-262 ◽

Cited By ~ 148

Author(s):

Nicholas J. Butterfield

Keyword(s):

Plant Biomass ◽

Marine Ecology ◽

Trophic Levels ◽

Cambrian Explosion ◽

Significant Shift ◽

Early Cambrian ◽

Cascade Process ◽

Key Innovation ◽

Large Animals ◽

Net Phytoplankton

Most modern marine ecology is ultimately based on unicellular phytoplankton, yet most large animals are unable to graze directly on even relatively large net phytoplankton; the repackaging effected by herbivorous mesozooplankton thus represents a key link in marine metazoan food chains. Despite the deep taphonomic biases affecting plankton fossilization, there is a clear record of phytoplankton from at least 1800 m.y ago. Proterozoic plankton are represented by small-to medium-sized sphaeromorphic acritarchs and probably do not include many/most of the unusually large acritarchs that characterize the Neoproterozoic. The first significant shift in phytoplankton diversity was therefore the rapid radiation of small acanthomorphic acritarchs in the Early Cambrian. The coincidence of phytoplankton diversification with the Cambrian radiation of large animals points compellingly to an ecological linkage between the two, particularly in light of recently discovered filter-feeding mesozooplankton in the Early Cambrian. The introduction of planktic filter feeders would have established the second tier of the Eltonian pyramid, potentially setting off the “self-propagating mutual feedback system of diversification” now recognized as the Cambrian explosion (Stanley 1973, 1976).By consuming significant percentages of net phytoplankton and suspending it as animal biomass and non-aggregating fecal pellets, mesozooplankton cause a net reduction in export production; a general introduction of zooplankton would therefore have reduced carbon burial and moderated the bloom and bust cycle that must have characterized Proterozoic populations of net phytoplankton. The effect of added trophic levels in Early Cambrian ecosystems can be viewed as a serial application of the trophic cascade process observed in modern lakes, whereby the introduction of higher trophic levels determines the accumulation of plant biomass at the base of the system. As such, the major biogeochemical perturbations that mark the onset of the Phanerozoic might be considered a consequence, rather than a cause, of the Cambrian explosion; reduced C export due to zooplankton expansion explains the otherwise anomalous drop in δ13C at the base of the Tommotian.Cambrian acanthomorphic acritarchs likely derived from planktic leiosphaerids exposed to mesozooplanktic grazing pressure, the ornamentation effectively increasing vesicle size without compromising buoyancy or surface-area:volume ratios. Alternatively, they may represent an escape into the plankton through a miniaturization of the much larger Neoproterozoic acanthomorphs. An invasion of small benthic herbivores into the water column to exploit the phytoplankton accounts for the origin of the mesozooplankton and may have been the key innovation in the Cambrian explosion.

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Vertical Migration of Pelagic and Mesopelagic Scatterers From ADCP Backscatter Data in the Southern Norwegian Sea

Frontiers in Marine Science ◽

10.3389/fmars.2020.542386 ◽

2021 ◽

Vol 7 ◽

Author(s):

Boris Cisewski ◽

Hjálmar Hátún ◽

Inga Kristiansen ◽

Bogi Hansen ◽

Karin Margretha H. Larsen ◽

...

Keyword(s):

Vertical Migration ◽

Complex Dynamics ◽

Atlantic Water ◽

Vertical Movement ◽

Light Cycle ◽

Photic Zone ◽

Calanoid Copepods ◽

Near Surface ◽

Norwegian Sea ◽

Deep Layers

Records of backscatter and vertical velocity obtained from moored Acoustic Doppler Current Profilers (ADCP) enabled new insights into the dynamics of deep scattering layers (DSLs) and diel vertical migration (DVM) of mesopelagic biomass between these deep layers and the near-surface photic zone in the southern Norwegian Sea. The DSL exhibits characteristic vertical movement on inter-monthly time scales, which is associated with undulations of the main pycnocline between the warm Atlantic water and the underlying colder water masses. Timing of the DVM is closely linked to the day-night light cycle—decent from the photic zone just before sunrise and ascent immediately after sunset. Seasonal variations are also evident, with the highest DVM activity and lowest depth averaged mean volume backscatter strength (MVBS) during spring. This suggests that both oceanographic and optical conditions are driving the complex dynamics of pelagic and mesopelagic activity in this region. We hypothesize that the increased abundance of calanoid copepods in the near-surface layer during spring increases the motivation for vertical migration of pelagic and mesopelagic species, which therefore can explain the increased DVM activity during this season.

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