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Settling aggregates transport organic matter from the ocean surface to the deep sea and seafloor. Though plankton communities impact carbon export, how specific organisms and their interactions affect export efficiency is unknown. Looking at 15 years of eDNA sequences (18S-V4) from settling and sedimented organic matter in the Fram Strait, here we observe that most phylogenetic groups were transferred from pelagic to benthic ecosystems. Chaetoceros socialis, sea-ice diatoms, Radiolaria, and Chaetognatha are critical components of vertical carbon flux to 200 m depth. In contrast, the diatom C. socialis alone is essential for the amount of organic carbon reaching the seafloor. Spatiotemporal changes in community composition show decreasing diatom abundance during warm anomalies, which would reduce the efficiency of a diatom-driven biological carbon pump. Interestingly, several parasites are also tightly associated with carbon flux and show a strong vertical connectivity, suggesting a potential role in sedimentation processes involving their hosts, especially through interactions with resting spores, which could have implications for pelagic-benthic coupling and overall ecosystem functioning. Examining 15 years of data in the Arctic, this study shows that plankton, including diatoms and parasites, play key roles in exporting carbon to the seafloor. Species like Chaetoceros socialis are crucial for carbon flux and pelagic-benthic coupling. [ABSTRACT FROM AUTHOR]

This study investigates the depositional environments and soft sediment deformation within the Early Jurassic Ammonitico Rosso Formation in the External Ionian Basin (Western Greece), focusing on its biostratigraphy, sedimentology, and tectonic activity. This research provides new insights into the depositional environment of the Ammonitico Rosso Formation and its transitions with the underlying and overlying formations. Syn-rift tectonics at the time of deposition formed half-grabens, which influenced sedimentary processes and created conditions for seabed slumping. Detailed field mapping and microfacies analysis revealed two distinct depositional environments: deep-water to open-shelf settings and platform-margin reefs. The entire Ammonitico Rosso Formation is allochthonous, deposited as repetitive slices of little-disturbed stratified sediments capped by debrites near the toe of a complex submarine landslide. The presence of well-preserved fossils, such as planktonic and benthic foraminifera, Radiolaria (both Spumellaria and Nassellaria), and ammonites, allowed precise age determinations, suggesting that the first appearance of Globuligerina might predate previous records, occurring first in the Pliensbachian rather than the Toarcian. These findings contribute to the ongoing debate on the depth and conditions of Ammonitico Rosso deposition, supporting the hypothesis of a relatively deep, open-shelf environment influenced by slope instability. [ABSTRACT FROM AUTHOR]

A new species of the genus Takemuraella (Radiolaria)–T. favosifluida sp. nov. has been described from deposits of the Upper Jurassic Bazhenov Formation based on materials from the Sredne-Balykskaya Borehole in Western Siberia (Parvicingula jonesi–P. excelsa Zone). The new species was also found in the South Tambeyskaya Borehole in the Russian Arctic, in the Upper Jurassic Parvicingula antoshkinae–P. blowi radiolarian Zone. [ABSTRACT FROM AUTHOR]

The geological structure was studied and the age of a number of tectonostratigraphic units in the Koryak Highlands was established for the first time. Radiolarian associations have been established that existed in various paleogeographic provinces and were combined in single tectonostratigraphic complexes. Cases of redeposition of radiolarians in siliceous rocks observed in accretionary prisms and olistostrome strata in the Koryak Highlands have been recorded. New localities of radiolarians have been discovered, which have made it possible to expand the scope of geographic distribution for some taxa. A bipolar distribution has been established for some representatives of radiolarians, first encountered in the northern hemisphere in Chukotka. The stratigraphic range of distribution for some species in the North-East of Russia and the age of a number of regional and local stratigraphic units have been clarified. A division scheme for the Middle Jurassic-Berriasian according to radiolarians for the Koryak Highlands is proposed. [ABSTRACT FROM AUTHOR]

The diversity of radiolarian species of the family Carpocaniidae Haeckel, 1881, emend. Riedel, 1967, from the surface sediments of the Emperor Seamount Chain (Nintoku, Jingū, Ojin, Koko and Yuryaku guyots) is analyzed. Five new species of the genus Carpocanium Ehrenberg, 1847, emend. nov.: C. rotundum sp. nov., C. fragaria sp. nov., C. alabastrum sp. nov., C. tulipa sp. nov., and C. fungus sp. nov. are described. The identification of the new species is based on their morphology, which differs from that of other species of the genus Carpocanium. It is proposed to restore Carpocanarium Haeckel, 1887 to a valid genus, and transfer it back into the family Carpocaniidae, based on the overall correspondence of its morphology to the diagnosis of this family. [ABSTRACT FROM AUTHOR]

Anthropogenic induced climate perturbations are seen in changes in oceanic circulation patterns, and Arctic water masses defined by salinity are vulnerable to change. Biogeography of marine microbial eukaryotes is expected to be impacted by changes in local environmental conditions and advective processes, but tracking the extent of plankton distribution requires understanding routes for both active and passive tracers. To identify such tracers, we focused on samples collected in the western (Canada Basin) and eastern (Nares Strait); extremes of the Canadian High Arctic that are connected by an east flowing current north of Canada. Sequencing of the V4 region of 18S rRNA revealed that Acantharia, a taxonomically and functionally diverse group of large planktonic protists, were particularly common. Arctic acantharians in our study were dominated by two clades belonging to cyst-forming groups. The distribution of one clade suggested successful advective transport from the Pacific sourced water in the Beaufort Gyre to southern Nares Strait, with cells transported along the northern shelf of the Canadian Arctic. A second clade appeared to be a resident taxon of the Canada Basin whose distribution correlated to local environmental conditions, and detection in deeper samples would be consistent with swarmer formation enabling reestablishment the following year. [ABSTRACT FROM AUTHOR]

This study investigates the intricate dynamics of siliceous plankton species within the open marine regions of the Greek Seas, focusing on their seasonal and spatial variability. For this purpose, vertical export fluxes of diatoms (DtF), silicoflagellates (SF), and radiolaria (RF) were analyzed in three sediment trap time series obtained from the North Aegean, Cretan, and Ionian Seas. Special attention was given to diatom assemblages, resulting in the estimation of the DtF community structure and diversity for each studied site. Diatom flux values reached 353.9 × 103 valves m−2 day−1, 77.7 × 103 valves m−2 day−1, and 42.4 × 103 valves m−2 day−1 in the North Aegean, Ionian, and Cretan Seas, respectively. SF maxima were 1309.8 × 103 skeletons m−2 day−1 in the North Aegean Sea, 35.2 × 103 skeletons m−2 day−1 in the Ionian Sea, and 11.9 × 103 skeletons m−2 day−1 in the Cretan Sea (South Aegean Sea). RF values reached 13.9 × 103 radiolaria m−2 day−1, 11.9 × 103 radiolaria m−2 day−1, and 5.4 × 103 radiolaria m−2 day−1 in the North Aegean, Ionian, and Cretan Seas, respectively. The North Aegean Sea exhibited significantly higher mean total fluxes, particularly for diatoms, driven by the north-to-south oligotrophy gradient, which was influenced by riverine inflows and the nutrient-rich Black Sea water. In the Cretan and Ionian Seas, convective mixing and atmospheric deposition, especially during increased rainfall (precipitation) events, were identified as primary drivers for the increased siliceous plankton fluxes recorded in the late winter–spring months. Diatom communities were dominated by Naviculales and Fragilariales; the prevalence of the former in the North Aegean Sea is likely linked to the higher nutrient levels in its upper photic zone, as Naviculales includes species with a high affiliation to nutrient enrichment. [ABSTRACT FROM AUTHOR]

Introduction. Radiolarians are an important group of marine planktonic protists. The polycystines (Phylum Radiozoa, Class Polycystina) are a group of radiolarians whose skeletons are made of opal (amorphous silica) and form the basis for their taxonomic classification. There are few recent studies of radiolarians in Costa Rica. Objective. This research seeks to create the first taxonomic guide of radiolarians present in Holocene sediments (from 11 000 years ago to the present) of the Costa Rican Pacific seabed. Methods. Between late 2018 and early 2019, two oceanic expeditions: Rock Hits and Costa Rica Deep-Sea Connections, respectively, collected 13 sediment cores from the Costa Rican Pacific seabed. Using a modified methodology created for these investigation, 64 samples were obtained from which radiolarian remains were extracted for taxonomic analysis. Obtained radiolarians were mounted for taxonomic analysis using optical and scanning electron (SEM) microscopy. Results. A total of 119 species of Polycystina were identified, distributed among 15 families belonging to the orders Collodaria (one family and eight species), Spumellaria (seven families and 62 species), and Nassellaria (seven families and 49 species). Conclusion. This study identifies several taxa (119) like those reported in studies conducted near the Pacific coast of Costa Rica, but less than half of those reported from the Eastern Equatorial Pacific (EEP). [ABSTRACT FROM AUTHOR]

Numerous representatives of the genus Foremanina Empson-Morin, 1981, emend. nov. were studied from the Upper Cretaceous (Maastrichtian) of the Lefkara Formation (Cyprus). The diagnosis of the genus Foremanina is emended. The new species F. macropora sp. nov., F. coronata sp. nov. and F. ornata sp. nov. are described. F. macropora sp. nov. is recorded for the first time in the Campanian of Sakhalin. The paleogeographic distribution of genus Foremanina is expanded to include the Tethyan Realm and Pacific Realm including the Mid-Pacific Mountains and Hokkaido–Sakhalin paleobasin. The latest representatives of Foremanina were found for the first time in the upper Maastrichtian of Cyprus. The stratigraphic range of the genus Foremanina is expanded. [ABSTRACT FROM AUTHOR]

Accretionary complexes in the Japanese Islands preserve material from parts of the oceanic plates of Panthalassa that have subducted and are now lost. The age of the oceanic plate that is incorporated into the Jurassic accretionary complex of Japan has been previously estimated from scant data on Carboniferous bedded chert. In this study, we investigated a Carboniferous to Permian basalt-chert sequence in the Jurassic accretionary complex of the North Kitakami-Oshima belt in Northeast Japan. The sequence is composed of basaltic rocks, red bedded chert and grey bedded chert in ascending order. The basaltic rocks at the base contain red cherty nodules that yielded conodonts indicating the Bashkiran to early Moscovian, the latter age being more likely (late Carboniferous). The red bedded chert yielded middle Sakmarian (early Permian) radiolarians. The grey bedded chert yielded conodonts indicating the latest Kungurian to earliest Roadian. Thus, our study section demonstrates a formation of the oceanic plate in the late Carboniferous and a following deposition of pelagic siliceous sediments. This is the first time that basaltic rocks within the Jurassic accretionary complex of Japan are directly dated. While previous data need careful reviewing, our results demonstrate that the oldest part of the oceanic plate within the Jurassic accretionary complex is Serpukhovian or older and the youngest part may be as young as the Sakmarian. [ABSTRACT FROM AUTHOR]

Radiolarian biochronology of radiolarites associated with ophiolitic lavas in northern Armenia provides important age constraints for the geodynamic reconstruction of Tethys in an area that makes the link between the Lesser Caucasus and the Eastern Pontides. We present results obtained from a moderately well-preserved radiolarian assemblage extracted from radiolarian cherts that crop out in the Bazoum Horst (between Stepanavan and Amasia). The age of these radiolarites may be restricted to the late Valangingian-Hauterivian based on the co-occurrence of the radiolarian species Archaeodictyomitra pseudoscalaris (Tan), Crolanium bipodium (Parona), Pseudodictyomitra suyarii Dumitrica and Tethysetta ovoidala Dumitrica. The dated radiolarites lie stratigraphically ca. 7-8 m above basaltic lavas that have a subduction-related geochemical signature. In combination with results from the Amasia ophiolite, this indicates the presence of a subduction-related island arc at the scale of the Amasia-Stepanavan oceanic realm that was active during Valanginian to Barremian times. [ABSTRACT FROM AUTHOR]

Major environmental, climate and sealevel changes occurred in the Western Tethyan Realm during the late Sinemurian to early Pliensbachian time interval. Here, we examine how these changes affected the taxonomic composition of radiolarian fauna. Radiolarian assemblages were collected on Mount Rettenstein (Northern Calcareous Alps) from a siliceous limestone and marl succession, deposited in a well‐oxygenated basin a few hundred metres in depth on the continental shelf at the western edge of the Neotethys Ocean. Radiolarian research was complemented with elemental and isotope geochemistry on bulk carbonate samples. The siliceous microfaunas below and above the stage boundary consist of more than 80% sponge spicules and less than 20% radiolarians, with a strong predominance of the Order Spumellaria. The Nassellaria to Spumellaria abundance ratio ranges from 1:5 to 1:3. At the Sinemurian–Pliensbachian transition, a significant drop in diversity occurred, accompanied by a substantial change in relative abundances of radiolarian taxa. The most severely affected groups were surface‐dwelling radiolarians (Angulobrachiidae, Hagiastridae, Pantanelliidae; mostly Gorgansium, Poulpidae and Ultranaporidae), which almost or completely disappeared. In contrast, Archaeocenosphaera, Praeconocaryomma, Zhamoidellum and Lantus became abundant and were apparently the most resistant to environmental stress. The changes in radiolarian assemblages were local and probably induced by the end‐Sinemurian sealevel drop that transformed the area into a semi‐enclosed basin with restricted ocean circulation. The exchange of water masses and thus radiolarian faunas with the open sea was reduced and their productivity may have been lowered by the lower inflow of fertile waters from the ocean. [ABSTRACT FROM AUTHOR]

Paleontological remains from the Bazhenovo Horizon of Western Siberia (Tithonian–Berriasian) are represented by macro- and microfossils. The Horizon had a marine genesis and the basis of ecosystem of this paleobasin composed of pelagic organisms-producers (phytoplankton: prasinophytes, coccolithophorids, dinoflagellates, as well as brown algae) and consumers (zooplankton: radiolarians, invertebrate larvae, crustaceans; and nekton: pelagic bony fish, ammonites, belemnites, paleosquids-teutids and marine dinosaurs; and, in addition, benthic bivalves, foraminifera, and ostracods). Among microfossils, radiolarians are the leading importance, phytoplankton (dinoflagellates, coccolithophorids) and microbenthos (foraminifera, sponge spicules) are less common. Radiolarians, dinoflagellates, coccolithophorids, and foraminifera are used for biostratigraphic subdividing of sections and their correlation, and, in addition, together with sponge spicules, for reconstruction the paleoenvironments. In literature, a several paper indicated the presence of other siliceous microfossils in paleobiota of the Bazhenovo paleosea – diatoms, silicoflagellates, and acantharians. The article summarized data on radiolaria, coccolithophorids, dinophyta and critically reviewed reports of other microobjects. It is shown that the information about diatoms, silicoflagellates and acantharians from Bazhenovo Horizon and Bazhenovo Formation is probably unreliable.

Diverse and well-preserved radiolarian assemblages were recovered from the middle Eocene sedimentary sequences drilled at Ocean Drilling Program Site 1051 (Leg 171B; western subtropical Atlantic). In addition to biostratigraphically important species, several unknown morphotypes were observed in this material, leading to the description of three new spumellarian species and 18 new nassellarian species. Described herein are: Periphaena petrushevskayae n. sp. (Phacodiscidae), Stylodictya oligodonta n. sp. (Trematodiscidae), Excentrosphaerella delicata n. sp. (Heliodiscidae), Eucyrtidium granatum n. sp. (Eucyrtidiidae), Dictyoprora echidna n. sp., Spirocyrtis matsuokai n. sp. (Artostrobiidae), Elaphospyris cordiformis n. sp., Elaphospyris quadricornis n. sp. (Cephalospyrididae), Ceratocyrtis oconnori n. sp. (Lophophaenidae), Botryocella? alectrida n. sp., Pylobotrys? bineti n. sp. (Pylobotrydidae), Lychnocanium cheni n. sp., Lychnocanium cingulatum n. sp., Lychnocanium croizoni n. sp., Lychnocanium forficula n. sp. (Lithochytrididae), Apoplanius hyalinus n. sp., Apoplanius cryptodirus n. sp. (Lophocyrtiidae), Albatrossidium messiaeni n. sp., Phormocyrtis microtesta n. sp., Cryptocarpium? judoka n. sp. (Pterocorythidae), and Thyrsocyrtis kamikuri n. sp. (Theocotylidae). Biostratigraphic information is provided for each new species. In addition, we re-describe and illustrate the morphological variability of a remarkable Pterocyrtidium species formerly published by Bütschli (1882a). UUID: http://zoobank.org/a01f7f03-73b0-458a-af7b-b85dc4666cc2 [ABSTRACT FROM AUTHOR]

Micropaleontology can give important insights into the provenance and paleoenvironmental conditions in terrestrial sedimentary archives. For the current study, 84 samples representing a 2.6 km thick sedimentary profile from the Simply Folded Zagros Mountain Belt were investigated. They span ca. 10.2 my from the late Middle Miocene (Serravallian) to the earliest Pleistocene (Gelasian), and comprise floodplain sediments and saline mudstones with an aeolian contribution. The samples revealed a unique Cretaceous radiolarian assemblage comprising largely of cryptothoracic nassellarians and spherical spumellarians. This record highlights the reworking of sediments derived from Cretaceous Qulqula-Kermanshah radiolarian claystones and radiolarites in the Imbricated Zagros Belt into distal Neogene Zagros foreland sediments in Lurestan (Lurestan Arc). The high abundance of Holocryptocanium barbui (Dumitrica) and other cryptothoracic taxa compared to the Qulqula-Kermanshah radiolarian claystones and radiolarites potentially indicates a preferred erosion of softer units such as the Red Radiolarian Claystone Unit (RRCU) compared to harder radiolarian cherts. The observation of a reworked largely cryptothoracic assemblage might also point to additional sorting effects during fluvial and aeolian transport as well as during redeposition, depending on the morphology and hydrodynamic properties of individual radiolarian taxa. [ABSTRACT FROM AUTHOR]

Numerous representatives of the genus Pseudodictyomitra Pessagno, 1977 were studied from the Upper Cretaceous of the Perapedhi Formation (Cyprus). The new species P. venusta sp. nov. is described. The description and stratigraphic range of P. crassa Bragina, 2013 are emended. [ABSTRACT FROM AUTHOR]

For science communication purposes, we projected three-dimensional (3D) models of radiolarians, obtained through X-ray micro-CT for scientific research, onto a planetarium dome. The represented models possessed a high 3D feeling that enabled easy recognition of radiolarian morphology. Radiolaria have a high affinity with fulldome projection owing to their scale, form, and historical background. We organized a project to promote radiolaria projection as planetarium content in more planetariums. This project would promote the use of planetariums as a visualization and expression medium for 3D data produced in scientific research. [ABSTRACT FROM AUTHOR]

Radiolarians hold a high academic value (e.g., geological, paleontological, and biological); however, they are not well known to the public worldwide. In conjunction with the InterRad XV in Niigata 2017 (Fifteenth Inter-Rad, international conference of radiolarians), certain outreach activities were conducted to raise the profile of radiolarians. Changes in the Google Trends of "Radiolaria" in Japanese were analyzed to evaluate the publicity effect. The search frequency of the term "..." (Radiolaria in Japanese) increased in the first half of 2017 when the outreach activities were conducted. Image search frequency increased noticeably in September 2019 when a picture book featuring radiolarians was published with related photograph exhibitions. Outreach activities related to InterRad XVachieved the desired effect of raising the radiolarian profile. Furthermore, the release of the picture book and the organization of the photograph exhibitions may have attracted the interest of people in radiolarian images. [ABSTRACT FROM AUTHOR]

Radiolaria is a valuable age index fossil through the Phanerozoic. This article describes the characteristics of the non-taxonomic names of closed nassellarian radiolarians, that is, di-segmented closed nassellarian (DiCN), tri-segmented closed nassellarian (TrCN), tetra-segmented closed nassellarian (TeCN), and multi-segmented closed nassellarian (MuCN), based on the number of segments. This article points out a potential as a practical age index for DiCN and TrCN. The TrCN occurrence indicates a Jurassic-Cretaceous age. In particular, the waterdrop-shaped TrCN-dominant occurrence suggests a Middle-Late Jurassic age; the spherical TrCN-dominant occurrence suggests a Cretaceous age. DiCN occurrence indicates a Jurassic-Cretaceous age, and abundant in the Middle Jurassic-Cretaceous. [ABSTRACT FROM AUTHOR]

This paper is a continuation of a previous one in which I described and revised different Middle Triassic nassellarian Radiolaria from the Alps and Carpathians illustrated with drawings. On the present paper, are described two new groups of Middle Triassic dicyrtid Nassellaria with bell-shaped shell from the same area to enrich the inventory of these microfossils. Two new families (Gorispelidae and Humerocyrtiidae), five new genera (Silicotintinnabulum, Colpotrelus, Gorispela, Pozsvartia and Humerocyrtis) and 30 new species are described from these genera and illustrated with drawings [ABSTRACT FROM AUTHOR]

DNA metabarcoding on a single organism is a promising approach to clarify the biological interactions (e.g., predator–prey relationships and symbiosis, including parasitism) of difficult‐to‐culture protists. To evaluate the effectiveness of this method, Radiolaria and Phaeodaria, which are ecologically important protistan groups, were chosen as target taxa. DNA metabarcoding on a single organism focused on the V9 region of the 18S rRNA gene revealed potential symbionts, parasites and food sources of Radiolaria and Phaeodaria. Previously reported hosts and symbionts (parasites) were detected, and newly recognized combinations were also identified. The contained organisms largely differed between Radiolaria and Phaeodaria. In Radiolaria, members of the same order tended to contain similar organisms, and the taxonomic composition of possible symbionts, parasites, and food sources was fixed at the species level. Members of the same phaeodarian family, however, did not contain similar organisms, and body part (i.e., the central capsule or the phaeodium) was the most important factor that divided the taxonomic composition of detected organisms, implying that the selection of appropriate body part is important when trying to ascertain contained organisms, even for unicellular zooplankton. Our results show that DNA metabarcoding on a single organism is effective in revealing the biological interactions of difficult‐to‐culture protists. [ABSTRACT FROM AUTHOR]

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The aim of this report is to 1) to formally describe Austral and Subtropical Gyre Radiolaria recovered from ODP Hole 123-765C), 2) to compare them with published records of Southern Hemisphere "non-Tethyan" assemblages and 3) to discuss radiolarian paleobiogeography of the Southern Hemisphere and its implications for global climate change during the Jurassic-Cretaceous transition. The Tithonian to Aptian/early Albian radiolarian record recovered from Hole 765C, Cores -62R to -36R in the Argo Abyssal Plain (AAP) is unique in its density of well-preserved samples and in its faunal contents. Radiolaria recovered from claystones yielded the low diversity, ecologically tolerant "Crypto-Archaeo" Assemblage, (chiefly cryptocephalic and cryptothoracic nassellarians and Archeodictyomitra spp.) interpreted herein as originated in the Subtropical Gyre (STG). In contrast, assemblages extracted from radiolarite layers, interpreted as pelagic turbidites derived from the deeper Australian margin, are dominated by Austral taxa. Neotethyan taxa are very rare to absent before the late Hauterivian/Barremian, when they gradually gain in diversity and abundance. Described Austral and STG taxa include 10 families, of which Fusitanellidae n. fam. and Windaliinae n. subfam. are new. Of 18 genera 7 are new (Nodosphaera, Praewindalia, Pachycingula, Archaeotanella, Morchella, Fusitanella, Argofusus) and of 55 species 30 new ones are formally described and 14 new ones are left in open nomenclature. The southern hemisphere Late Jurassic to Early Cretaceous radiolarian biogeography is defined from low- to high latitude: 1. the Neotethyan (NT) and 2. the Central Panthalassan (CP) realms, 3. Eastern Boundary Current (EBC) realm, 4. the Subtropical Gyre (STG) and the Austral (A) circum south-polar realm. Radiolarian biogeography and plate tectonic models support a scenario of palaeoceanographic and global climatic change during the Jurassic-Cretaceous transition related to progressive Pangea break-up with the following consequences: 1. an increased heat transfer to the Southern hemisphere which caused cooling of Neotethyan regions during the Late Tithonian dry event. 2. Anorthward shift of the southern summer Intertropical Convenience Zone reduced the Neotethyan monsoon area and allowed the establishment of a southern Neotethyan subtropical gyre documented by the "Crypo-Archaeo" Assemblage. 3. The south-polar West Wind Drift may have forced a circum Antarctic-Australian cold current through the epicontinental rift between India and Antarctica-Australia since the Berriasian (140 my), transporting Austral Radiolaria into the AAP where they accumulated in radiolarite layers. [ABSTRACT FROM AUTHOR]

Upper Triassic to Lower Cretaceous stratigraphic successions deposited on the passive continental margin of Adria microplate facing the Neotethys Ocean were investigated on Ivanščica Mt. (NW Croatia). This area represents a transitional area between the Alps and the Dinarides. After a short Middle Triassic pelagic episode related to the rifting of the Neotethys, progradation of the carbonate platform over newly formed grabens resulted in formation of stable shallow-water depositional environment during the Late Triassic. Tectonically induced subsidence pulse at the Triassic/Jurassic boundary affected SE part of the investigated area resulting in the deposition of pelagic limestones, shale, marls, and calcarenites above Upper Triassic platform carbonates. At the same time, NW part of the investigated area was still characterized by shallow-water sedimentation until the Pliensbachian. This second subsidence phase was manifested by formation of neptunian dykes within Lower Jurassic platform limestones and deposition of the Middle Jurassic pelagic limestones. These two Early Jurassic subsidence events are likely related to the rifting of the Alpine Tethys. Radiolarian cherts were deposited in both areas in the late Middle and Late Jurassic. Radiolarians from the SW Ivanščica Mt. indicate late Bathonian to Early Tithonian age of the radiolarian cherts. Uppermost Jurassic to Lower Cretaceous Aptychus limestone is found across the entire investigated area. These limestones were deposited from the Late Tithonian to the Valanginian when synorogenic mixed carbonate–siliciclastic turbidites started to fill the basin indicating a prominent compressional tectonic phase widely recorded in the Alps and the Dinarides. [ABSTRACT FROM AUTHOR]

Several sections of the upper part of the Kannaviou Formation in southwest Cyprus are described. All sections are characterized by planktonic microfossil groups that include foraminifera and radiolarians. The presence of the key species Hendersonites carinatus makes it possible to identify the middle–upper Campanian stratigraphic interval in deep-marine facies. Identification of Contusotruncana plummerae and H. carinatus allows us to recognize the C. plummerae–H. carinatus Beds (middle–upper Campanian). Radiolaria from the Kannaviou, Vretsia and Armou sections (upper part of the Kannaviou Formation) are represented by characteristic assemblages of the lower part (upper part middle–upper Campanian) of the Amphipyndax tylotus Zone (upper part middle/upper Campanian–Maastrichtian). A more accurate identification of the lower boundary of the A. tylotus Zone is based on the integrated planktonic foraminiferal and radiolarian biostratigraphy. [ABSTRACT FROM AUTHOR]

We present new biostratigraphic results from two ophiolite outcrops in Armenia. The discovery of upper Tithonian–lower Berriasian diagnostic radiolarian species (Vallupus gracilis Li and Sashida) in the lower radiolarites of the Dali section allows to date more accurately submarine lava eruptions of transitional to alkaline composition. The radiolarian results also indicate that blocks of shallow-water carbonates slid into the basin during this time interval. At Vedi, upper Coniacian–Santonian calcareous nannofossils identified in marls of the post-obduction sedimentary cover refine previous age data. Synthesis of the existing bio-chronostratigraphic constraints in Armenia and Karabagh sheds light to the depositional and magmatic history of Tethys in the Lesser Caucasus and highlights the age constraints of fossils on the timing of ophiolite obduction in the region.

Research in extreme environments has substantially expanded our understanding of the ecology and evolution of life on Earth, but a major group of organisms has been largely overlooked: microbial eukaryotes (i.e., protists). In this Perspective, we summarize data from over 80 studies of protists in extreme environments and identify focal lineages that are of significant interest for further study, including clades within Echinamoebida, Heterolobosea, Radiolaria, Haptophyta, Oomycota, and Cryptophyta. We argue that extreme environments are prime sampling targets to fill gaps in the eukaryotic tree of life and to increase our understanding of the ecology, metabolism, genome architecture, and evolution of eukaryotic life. The ecology and evolution of eukaryotic microbes in extreme environments are poorly understood. In this Perspective, Rappaport and Oliverio summarize data from over 80 studies of protists in extreme environments and identify lineages of particular interest as targets for future research. [ABSTRACT FROM AUTHOR]

Numerous representatives of the genus Patellula Kozlova, 1972 were studied from the Upper Cretaceous deposits of Perapedhi, Kannaviou and Lefkara formations (Cyprus). Two new species were described: Patellula mangaleniensis sp. nov. and Patellula solaris sp. nov. The species P. mangaleniensis was found in Crimea within the Afens perapediensis Zone (upper part of the Upper Santonian). The earliest representatives of Patellula euessceei Empson-Morin, 1981 were for the first time found in the Upper Cretaceous of Crimea, within the Actinomma (?) belbekense Zone (upper part of the Middle Turonian–Upper Turonian), while the latest representatives of P. euessceei were for the first time detected in the Maastrichtian of Cyprus. The stratigraphic ranges of Patellila euessceei and the genus Patellula are expanded. [ABSTRACT FROM AUTHOR]

The genus Triaenosphaera Deflandre, 1973 is revised and its diagnosis is emended. Four new radiolarian species from the Lower Tournaisian, Lower Carboniferous of the Volga-Ural Basin and the Upper Kasimovian, Upper Carboniferous of the South Urals are described: Entactinia zaitsevae sp. nov., Triaenosphaera fortunatovae sp. nov., T. spiroacus sp. nov., and Spongentactinia oraia sp. nov. [ABSTRACT FROM AUTHOR]

The time series of downward particle flux at 3000 m at the Porcupine Abyssal Plain Sustained Observatory (PAP-SO) in the Northeast Atlantic is presented for the period 1989 to 2018. This flux can be considered to be sequestered for more than 100 years. Measured levels of organic carbon sequestration (average 1.88 gm−2 y−1) are higher on average at this location than at the six other time series locations in the Atlantic. Interannual variability is also greater than at the other locations (organic carbon flux coefficient of variation = 73%). We find that previously hypothesised drivers of 3,000 m flux, such as net primary production (NPP) and previous-winter mixing are not good predictors of this sequestration flux. In contrast, the composition of the upper ocean biological community, specifically the protozoan Rhizaria (including the Foraminifera and Radiolaria) exhibit a close relationship to sequestration flux. These species become particularly abundant following enhanced upper ocean temperatures in June leading to pulses of this material reaching 3,000 m depth in the late summer. In some years, the organic carbon flux pulses following Rhizaria blooms were responsible for substantial increases in carbon sequestration and we propose that the Rhizaria are one of the major vehicles by which material is transported over a very large depth range (3,000 m) and hence sequestered for climatically relevant time periods. We propose that they sink fast and are degraded little during their transport to depth. In terms of atmospheric CO2 uptake by the oceans, the Radiolaria and Phaeodaria are likely to have the greatest influence. Foraminifera will also exert an influence in spite of the fact that the generation of their calcite tests enhances upper ocean CO2 concentration and hence reduces uptake from the atmosphere.

The current study deals with microfacies and the depositional environment of the Lower Cretaceous Sarmord Formation at selected sections in Sulaimani and Erbil Governorates, northern Iraq. The Sarmord Formation alternates rhythmically between yellowish grey marly limestones and grey black marls. These lithologies are observed in all studied sections of Sarmord Formation in northern Iraq. Petrographic investigation of this study based on 240 thin sections demonstrated that the carbonate constituents are mainly composed of skeletal and non-skeletal grains. The skeletal grains include a variety of foraminiferas (planktonic and benthonic), bioclasts, calcispheres, ostracods, radiolaria, echinoderms, sponge spicules, ammonoids and belemnites. The non-skeletal grains consist of rare intraclasts. Based on field observations, two major lithofacies are recognized in the studied sections, namely marly limestone and marl lithofacies. Depending on the detailed microfacies analysis, two main microfacies, which in turn are divided into four sub-microfacies, were identified. These facies were subdivided upon their environmental interpretation into two types of facies associations: deep shelf and basinal. From the results of petrographic, facies, and textural analyses, it is concluded that Sarmord Formation in the studied sections was deposited at a rimmed carbonate platform. With a gradual shallowing of the basin from basinal sediments at the lower part overlying by deep shelf sediments in the uppermost part of the formation in the studied sections. [ABSTRACT FROM AUTHOR]

In this paper we present new data on the Jurassic radiolarian assemblages collected in seven sections of the sedimentary cover of the Mirdita ophiolites in Albania. These ophiolites form an outstanding NNW-SSE trending ophiolitic belt representing the remnants of the Mesozoic Neo-Tethyan oceanic lithosphere in the Mediterranean area. The studied sections were sampled in the sub-ophiolitic mélange of the Western Mirdita ophiolites (Rubik Complex) and in the Eastern Mirdita ophiolitic sequences. In the sub-ophiolitic mélange the oldest ages of radiolarians associated with the basalts are referable to the UAZ 4-5 (late Bajocian to latest Bajocian-early Bathonian) and UAZ 5 (latest Bajocian-early Bathonian). In the radiolarian cherts belonging to the Eastern Mirdita ophiolites similar ages were found: from UAZ 5 (latest Bajocian-early Bathonian) to UAZ 5-7 (latest Bajocian-early Bathonian to late Bathonian-early Callovian). These new biostratigraphic ages are consistent with the tectono-magmatic evolution of the Jurassic Neo-Tethys. In fact, the UAZ 4-5 and UAZ 5 correspond to the very early stages of subduction initiation, whereas the slightly younger UAZ 5 and UAZ 5-7 ages found in the Eastern Mirdita ophiolites could correspond to the subsequent mature stage of the subduction. [ABSTRACT FROM AUTHOR]

ABSTRACT Mitochondria originated from an ancient bacterial endosymbiont that underwent reductive evolution by gene loss and endosymbiont gene transfer to the nuclear genome. The diversity of mitochondrial genomes published to date has revealed that gene loss and transfer processes are ongoing in many lineages. Most well-studied eukaryotic lineages are represented in mitochondrial genome databases, except for the superphylum Retaria—the lineage comprising Foraminifera and Radiolaria. Using single-cell approaches, we determined two complete mitochondrial genomes of Foraminifera and two nearly complete mitochondrial genomes of radiolarians. We report the complete coding content of an additional 14 foram species. We show that foraminiferan and radiolarian mitochondrial genomes contain a nearly fully overlapping but reduced mitochondrial gene complement compared to other sequenced rhizarians. In contrast to animals and fungi, many protists encode a diverse set of proteins on their mitochondrial genomes, including several ribosomal genes; however, some aerobic eukaryotic lineages (euglenids, myzozoans, and chlamydomonas-like algae) have reduced mitochondrial gene content and lack all ribosomal genes. Similar to these reduced outliers, we show that retarian mitochondrial genomes lack ribosomal protein and tRNA genes, contain truncated and divergent small and large rRNA genes, and contain only 14 or 15 protein-coding genes, including nad1, -3, -4, -4L, -5, and -7, cob, cox1, -2, and -3, and atp1, -6, and -9, with forams and radiolarians additionally carrying nad2 and nad6, respectively. In radiolarian mitogenomes, a noncanonical genetic code was identified in which all three stop codons encode amino acids. Collectively, these results add to our understanding of mitochondrial genome evolution and fill in one of the last major gaps in mitochondrial sequence databases. IMPORTANCE We present the reduced mitochondrial genomes of Retaria, the rhizarian lineage comprising the phyla Foraminifera and Radiolaria. By applying single-cell genomic approaches, we found that foraminiferan and radiolarian mitochondrial genomes contain an overlapping but reduced mitochondrial gene complement compared to other sequenced rhizarians. An alternative genetic code was identified in radiolarian mitogenomes in which all three stop codons encode amino acids. Collectively, these results shed light on the divergent nature of the mitochondrial genomes from an ecologically important group, warranting further questions into the biological underpinnings of gene content variability and genetic code variation between mitochondrial genomes.

Analysis of the morphology of radiolarian skeletons from the Lower Permian of the South Urals made it possible to revise the taxonomic assignment of Helioentactinia uralica Kozur et Mostler, 1989 and two different morphotypes of Helioentactinia sp. and assign them to three species within the new genus Alexialeks gen. nov.: A. uralicus (Kozur et Mostler, 1989), A. alius sp. nov. and A. distinctus sp. nov. Three pathways are recognized in the evolution of Alexialeks gen. nov. in the Asselian, Sakmarian, Artinskian, and Kungurian (Early Permian). The diagnoses of the genus Multisphaera Nazarov et Afanasieva in Afanasieva, 2000, emend. nov. and subfamily Multisphaerinae Nazarov et Afanasieva in Afanasieva, 2000, emend. nov. are emended. The validity of the subfamily Multisphaerinae Nazarov et Afanasieva in Afanasieva, 2000, emend. nov. is confirmed. A hypothesis is proposed that a primary inner sphere with a rudimentary four-ray spicule and numerous rod-like spines may represent a transitional form of the internal skeleton framework from an n-ray spicule to a true microsphere. [ABSTRACT FROM AUTHOR]

Radiolarians of the order Latentifistularia are described from strata of the Roadian Stage (Guadalupian Series, middle Permian) exposed in a small roadside quarry (Quarry section) in the Guadalupe Mountains, West Texas. The families Cornellidae Kozur andMostler and Ishigaidae Kozur and Mostler are discussed. The genus Pseudotormentus is reassigned to the family Latentifistulidae. The genus Octatormentum and species Latentifistula patagilaterala, Quinqueremis robusta, Ormistonella minima, Tetratormentum nitidus and Octatormentum cornelli are revised. The species Tormentum delicatum assigned to the genus Rectotormentum. One genus, Nabespecha, is reinstated herein. Three new genera, Murcheyella, Sashitonishella and Quadrulites, and 17 new species: Latentifistula crassa, L. macilenta, L. coniformis, Murcheyella marginata, Latentibifistula dellensis, Pseudotormentus ornatus, Cauletella caridroiti, Praedeflandrella insueta, Quinqueremis pentagonus, Q. porosus, Sashitonishella rara, Polyfistula composita, Ormistonella aetheria, O. decurvata, Tetragregnon delawarus, Tormentum lobatum, and Grandetortura sashidai are described. [ABSTRACT FROM AUTHOR]

Interest in the study of microplanktonic organisms in the Arctic has increased owing to their direct participation in the process of sedimentation and sensitive response to changes in environmental and climatic factors. This study presents new data on the taxonomic diversity and content of radiolarian skeletons and agglutinated tintinnid ciliate loricae in the Upper Holocene sediments of the Laptev Sea, East Siberian Sea, and the adjacent part of the Arctic Ocean. We traced the spatial distribution of representative microfauna of these groups in surface sediments and sediment cores. Radiolarian skeletons were found in the surface sediments of the continental slope of the Laptev Sea and adjacent parts of the Arctic Ocean. These belong to the following six species: Stylatractus (?) sp., Actinomma leptoderma leptoderma, Actinomma leptoderma longispina, Streblacantha circumtexta, Spongotrochus glacialis, and Cycladophora davisiana. The radiolarian fauna detected was in deep sea and close to the fauna of the Nansen Basin (Central Arctic). Furthermore, we found tintinnid ciliate loricae belonging to the following seven species: Tintinnopsis ventricosoides, Tintinnopsis fimbriata, Tintinnopsis turbo, Tintinnopsis nitida, Tintinnopsis sp. cf. fusus (?), Tintinnopsis sp., and Stenosemella nivalis. In the study area, the tintinnid ciliate loricae of these species were discovered for the first time and traced mainly in the coastal shelf zone, which can be explained by their ecology. The only exception is that of T. nitida, which was found only on the continental slope of the Laptev Sea. Our findings advance knowledge on the biodiversity of Arctic seas and can be used to monitor ecological and paleoceanographic changes in the Arctic region. [ABSTRACT FROM AUTHOR]

To determine the present-day community composition of siliceous Rhizaria (Radiolaria and Phaeodaria) in Norwegian fjords, plankton tows were conducted in south-western and northern Norwegian fjords in September 2016. The mean total abundance of radiolarians was 306 m–3 in the Sognefjord complex, which was the southern research site, and, in the north, 945 m–3 in Malangen and 89 m–3 in Balsfjord, both above the Arctic Circle. Sticholonche zanclea was the most abundant radiolarian in the Sognefjord complex and Malangen, accounting for 78–100% (mean 89%) of radiolarian abundance. The mean total abundance of phaeodarians was 1554 m–3 in the Sognefjord complex, 51 m–3 in Malangen and 11 m–3 in Balsfjord. Medusetta arcifera was the most abundant phaeodaria in the Sognefjord complex, accounting for >99% of phaeodarian abundance, but was absent in Malangen and Balsfjord, where Protocystis tridens accounted for >96% of phaeodarian abundance. The carbon biomass of S. zanclea and M. arcifera was 188 and 438 µg C m–3, respectively, which is similar to and 8.6 times higher than, respectively, that of phaeodarians >1 mm in the western North Pacific, suggesting that M. arcifera contributes to organic carbon transport in the Sognefjord complex. Amphimelissa setosa (Nassellaria, Radiolaria), which was a dominant species in the study area in 1982–83, was absent in the present study in all sampled fjords. This could have been caused by the approximately 2 °C increase in water temperature that has occurred since 1990 and can be taken as evidence of a climate-change-associated local temperature rise linked to the warming of advected Atlantic Water. [ABSTRACT FROM AUTHOR]

The technique proposed herein reveals the internal morphology of calcareous and agglutinated foraminifers in transmitted light, aiding in taxonomic identifications. It involves eliminating air bubbles inside tests through the application of a vacuum or high heat during oil immersion, and the subsequent mounting of the oil-clarified tests in compatibleQSMMthermoplastics. The technique is rapid, nondestructive, allows internal viewing of large tests and is especially useful for small tests that are difficult to thin section. The technique has been used for mounting other microfossils, such as polycystine radiolarians. [ABSTRACT FROM AUTHOR]

Ocean circulation and the formation and upwelling of water masses in the Southern Ocean play a critical role in the exchange of heat and carbon with the atmosphere over glacial-interglacial cycles, but the history of the subsurface water masses is poorly understood. Radiolarians inhabit the water column from the surface to the bottom of the ocean, and their distribution is known to be associated with water masses. We use radiolarian abundance census data from the SO-RAD core top dataset to explore the relationship between radiolarian distribution and surface and subsurface water mass structure of the Southwest Pacific Sector of the Southern Ocean. The species distribution was first explored using non-Metric Multidimensional Scaling. Then Multivariate Regression Tree (MRT) analysis was used to understand the relationship between radiolarian distributions and parameters of water mass boundaries (using isopycnal depths) and upwelling (using nutrient data). We identified a series of indicator species associated with oceanographic zones which were used to develop the Southern Ocean Water Mass Index. The contribution of the Index Species Groups provided further information on water column structure and the relative influence of the various water masses. The index was then applied to the radiolarian assemblage data from 2 previously published cores, Y8 and Y9, from the Subantarctic Zone east of New Zealand. The results of the Southern Ocean Water Mass Method showed changes in water mass structure through the last glacial-interglacial cycle at both core sites. The results agree with other proxy data from the region. The SOWM Method provides a new tool for understanding the history of changes in the water mass structure and circulation in the Southern Ocean. [Display omitted] • A new proxy for water masses was developed using radiolarian assemblages. • 5 water mass groups were identified in the SW Pacific using statistical analyses. • The new proxy identified changes in water masses over the last glacial cycle. [ABSTRACT FROM AUTHOR]

Haeckel's 'art book', Kunstformen der Natur , is likely familiar to most protistologists as it is probably Haeckel's best known work, and it prominently featured protists. No doubt many of us have used some of the images from it in our lectures. Most familiar are perhaps the often-reproduced images of nassularian radiolaria, but plates were also devoted to phaeodarians, acantharia, foraminifera, ciliates, diatoms, dinoflagellates and desmids. Despite the fame of Kunstformen der Natur , there are aspects of the work that have received little attention, and are of potential interest to protistologists. These include the overall importance of protists in the work, compared to other taxa, the surprisingly under appreciated role of Haeckel's collaborator, Adolph Giltsch in creating the figures, the disputed fidelity of the illustrations of protists, and Haeckel's discrete inclusion of many descriptions of new species of protists, forcing us to consider Kunstformen a scientific publication. Here these aspects, and the 20 plates featuring protists will be reviewed. The goal of this review is to familiarize protistologists with the most famous work featuring protists, and point out the many particular figures of protists we may wish to avoid showcasing, as the illustrations are questionable. A supplemental file is provided listing the currently accepted names of the protist taxa (for names found in a database), and the reasons for considering some illustrations as questionable. [ABSTRACT FROM AUTHOR]

New perspectives in the archaeometric investigation of the chert used in lithic tool assemblages allow us to learn more about the socio−economic behavior of prehistoric human groups. The case study presented here is from the Artofago Cave in South Tuscany, Italy. Among other findings, an Upper Paleolithic lithic complex was excavated from a large fireplace near the entrance. The purpose of this study is to gather data aimed at determining the raw material used in the production of these lithic tools, thereby enhancing research into its geographic source area. Here we highlight the significance of the geological age of the rock as one of key factors enabling us to formulate hypotheses about its geological provenance. It showcases a successful application of radiolarian biostratigraphy in dating cherts from the archaeological record. Specifically, 67 chert samples from the Upper Paleolithic lithic complex of the Artofago cave were treated with HF to isolate the radiolarian assemblages. The samples had been carefully chosen in advance between broken chert pieces (chert debris) in the waste material given that the analysis is partially destructive. Chert samples can be assigned to a Middle − Late Jurassic age, more specifically middle Callovian−early Oxfordian to late Kimmeridgian−early Tithonian (UAZ 8-11). These ages are comparable with those of the Diaspri di Monte Alpe Formation of the Ligurian Vara Unit, the uppermost tectonic unit of the Northern Apennines. [ABSTRACT FROM AUTHOR]

Reconstructing ocean plate stratigraphy (OPS) and revealing the places of origin and ages of oceanic rocks of the Jurassic–Early Cretaceous accretionary complex in Eastern Asia are important to clarify the accretion process and the paleogeography and tectonic setting of the Panthalassa Sea during the Paleozoic to Mesozoic times. In this context, many geological investigations of the Middle Jurassic–Early Cretaceous units of the Northern Chichibu accretionary complex (except for an Early Jurassic one) and Mikabu Unit have been performed. In this study, geological mapping, faunal analysis of radiolarians, and geochemical analysis of basaltic rocks were conducted for the Hebiki Unit of the Northern Chichibu accretionary complex to obtain prime geological information such as its stratigraphy, ages, and origin of basaltic rock. The Early Jurassic Hebiki Unit consists of chaotic mélange, which contains sandstone, siliceous shale, chert, and basaltic rocks as blocks in a highly sheared shale matrix. Late Permian and Late Triassic radiolarians were newly identified from chert blocks in this study. Based on the radiolarian evidence from this study and previous ones that identified Jurassic radiolarians from siliceous shale, the OPS of the Hebiki Unit are reconstructed as follows: Upper Permian and Upper Triassic (upper Carnian to Rhaetian) chert, and Lower Jurassic (Pliensbachian) siliceous shale in ascending order. Meanwhile, the basaltic rocks of the Hebiki Unit are divided into two types in terms of the major and trace element composition and REE profiles: low and high Nb/Zr types. The low and high types are interpreted as oceanic island basalt (OIB) and mid-ocean ridge basalt (MORB), respectively. Considering the reconstructed OPS of the four tectonostratigraphic units (Kashiwagi, Kamiyoshida, Sumaizuku, and Hebiki) of the Northern Chichibu accretionary complex, the four units are considered to have accreted successively. [ABSTRACT FROM AUTHOR]

Oceanic Anoxic Event 2, spanning the Cenomanian/Turonian boundary (93.9 Ma), was an episode of major perturbations in the global carbon cycle. To investigate the response of biota and the paleoceanographic conditions across this event, we present data from International Ocean Discovery Program sites U1513 and U1516 in the Mentelle Basin (offshore SW Australia; paleolatitude 59°–60°S in the mid‐Cretaceous) that register the first complete records of OAE 2 at southern high latitudes. Calcareous nannofossils provide a reliable bio‐chronostratigraphic framework. The distribution and abundance patterns of planktonic and benthic foraminifera, radiolaria, and calcispheres permit interpretation of the dynamics of the water mass stratification and provide support for the paleobathymetric reconstruction of the two sites, with Site U1513 located northwest of the Mentelle Basin depocenter and at a deeper depth than Site U1516. The lower OAE 2 interval is characterized by reduced water mass stratification with alternating episodes of enhanced surface water productivity and variations of the thickness of the mixed layer as indicated by the fluctuations in abundance of the intermediate dwelling planktonic foraminifera. The middle OAE 2 interval contains lithologies composed almost entirely of radiolaria reflecting extremely high marine productivity; the low CaCO3 content is consistent with marked shoaling of the Carbonate Compensation Depth and ocean acidification because of CaCO3 undersaturation. Conditions moderated after deposition of the silica‐rich, CaCO3‐poor rocks as reflected by the microfossil changes indicating a relatively stable water column although episodes of enhanced eutrophy did continue into the lower Turonian at Site U1516. Key Points: Documentation of first complete record of the Late Cretaceous Oceanic Anoxic Event 2 (OAE 2) at southern high latitudes (60°S) in the Indian OceanDynamics of the water mass stratification inferred from distribution patterns of foraminifera, radiolaria, calcispheresOAE 2 is characterized by alternating episodes of enhanced surface water productivity and variations of the thickness of the mixed layer [ABSTRACT FROM AUTHOR]

Adetailed study on radiolarian biostratigraphy and paleoecology has been carried out from three outcrops on Havelock Island, belonging to theRitchie'sArchipelago of Andaman and NicobarGroup of islands. Though most of the radiolarian taxa aremoderately preserved, it was possible to demarcate an age ranging from late early to early middleMiocene based on index radiolarians of RN4 andRN5 zones. An attempt has been made to correlate the radiolarian events recorded hereinwith earlier reports on radiolarians from differentDSDP, ODP, and IODPsites of the Indian Ocean and the onshore sections of different islands of theAndaman and NicobarBasin.A total of 119 radiolarian taxa belonging to 70 genera have been recorded in the present study, out of which 4 species are being reported for the first time from the northeastern part of the Indian Ocean. Diversity analyses were performed to deduce the Shannon Diversity Index, Simpson Index, Margalef Richness, and Pielou's Evenness. TheWater Depth Ecology index (WADE) has been analyzed for a better understanding of the paleoecological perspectives, and the Nassellaria-Spumellaria ratio of each outcrop has been calculated to ascertain the water depth. Comparison of the data obtained from diversity analysis andWADE index provides a clear picture of the environment during the late early to early middleMiocene. The overwhelming dominance of warm species of radiolarians may be linked to the Miocene Climate Optimum (MCO) event. [ABSTRACT FROM AUTHOR]

Summary: Ribosomal RNA (rRNA) genes are known to be valuable markers for the barcoding of eukaryotic life and its phylogenetic classification at various taxonomic levels. The large‐scale exploration of environmental microbial diversity through metabarcoding approaches has been focused mainly on the V4 and V9 regions of the 18S rRNA gene. The accurate interpretation of such environmental surveys is hampered by technical (e.g. PCR and sequencing errors) and biological biases (e.g. intra‐genomic variability). Here we explored the intra‐genomic diversity of Nassellaria and Spumellaria specimens (Radiolaria) by comparing Sanger sequencing with Illumina and Oxford Nanopore Technologies (MinION). Our analysis determined that intra‐genomic variability of Nassellaria and Spumellaria is generally low, yet some Spumellaria specimens showed two different copies of the V4 with <97% similarity. Of the different sequencing methods, Illumina showed the highest number of contaminations (i.e. environmental DNA, cross‐contamination, tag‐jumping), revealed by its high sequencing depth; and MinION showed the highest sequencing rate error (~14%). Yet the long reads produced by MinION (~2900 bp) allowed accurate phylogenetic reconstruction studies. These results highlight the requirement for a careful interpretation of Illumina‐based metabarcoding studies, in particular regarding low abundant amplicons, and open future perspectives towards full‐length rDNA environmental metabarcoding surveys. [ABSTRACT FROM AUTHOR]