Ostracods Research Articles

Comparison and evaluation of methods for distinguishing among several functional classes of zooplankton and fish using acoustic backscatter data at four frequencies

Zooplankton net samples data were collected at 30 locations near the Pribilof Islands, Alaska in September 1999 using a MOCNESS. Simultaneous volume backscatter data were collected with an HTI echosounder system at: 43, 120, 200, and 420 kHz. Three algorithms were compared for their ability to classify acoustic data into the dominant zooplankton functional/size groups (euphausiids, copepods, and ostra cods) and separating them from fish. The algorithms tested include: (1) combining morphological image processing and image differences to identify patches in different size ranges, and using the forward problem calibrated to plankton found in MOCNESS hauls to ascribe size/functional groups to the different patches; (2) application of canonical correlation between acoustics (backscatter volume and target strengths) and plankton biomass captured by the MOCNESS; and (3) application of inverse techniques to estimate the number of individuals in set size classes using multiple theoretical models of backscatter volume compared to plankton biomass captured by a net. Knowledge of the strengths and weaknesses of each technique allows us to better interpret broad-scale acoustic survey results from the same cruise, thus providing a synoptic view of the fish and their plankton prey which are in the size and density range to be acoustically detected.

A LATE TRIASSIC OSTRACOD ASSEMBLAGE FROM THE QUATTERVALS NAPPE (AUSTROALPINE, NORTHERN ITALY)

The up to 1200 m thick Norian succession of the Quattervals Nappe (Central Austroalpine, Italy) documents a tectonically-driven passage from intertidal facies (Dolomia Principale-Hauptdolomit), represented by early-dolomitized bedded to massive gray dolostones, to intraplatform basin sediments (Pra Grata Formation and Quattervals Limestone), consisting of resedimented dark limestones and thin bedded laminated limestones, alternating (mainly in the Pra Grata Formation) with intraformational breccias containing abundant shallow-water facies. The transitional and basinal facies contain an interesting ostracod assemblage, beside bioclastic layers containing shallow-water and upper slope skeletal grains.The ostracod fauna is rich in specimens belonging to few genera, denoting restricted environmental conditions characterized by variations of salinity and low oxygenation. Despite the intense deformation and recrystallization related to the Alpine tectonics, the paleontological analysis of the ostracod assemblage from the base of the Quattervals Limestone, allowed the identification of the two new species of ostracods Rhombocythere dimorphica and Kerocythere quattervalsi in association with other already known forms.

First Permian Ostracode Fauna from the Arabian Plate (Khuff Formation, Sultanate of Oman)

First Permian Ostracode Fauna from the Arabian Plate (Khuff Formation, Sultanate of Oman)

EVIDENCE OF A GUADALUPIAN AGE FOR THE KHUFF FORMATION OF SOUTHEASTERN OMAN: PRELIMINARY REPORT

The Guadalupian succession of the Huqf area (Sultanate of Oman) represents a mega-sequence comprising the fluvial terrigenous Gharif Formation and the overlying marine Khuff Formation. The Khuff Fm. is subdivided into four members and is composed of marls and bioclastic limestones. The Khuff Fm. yields a rich fauna of brachiopods, conodonts, foraminifers, bivalves, gastropods, ostracods and cephalopods. The brachiopod fauna of the Khuff Fm. includes strophomenids, productids, orthids and terebratulids. The associated conodont fauna includes Hindeodus excavatus Behnken, Merrilina sp., M. praedivergens Kozur & Mostler, and Sweetina n. sp. (systematic descriptions of conodonts are given in the Paleontological Appendix). Foraminifers are represented by species of Miliolina and Rotaliina. The Khuff Fm. is given a Wordian age, based on brachiopods and conodonts. The depositional environment of the Khuff Fm. of southeastern Oman corresponds to the outer shelf of a large carbonate platform covering most of the Arabian Platform. The Khuff Fm. is interpreted as a major transgressive-regressive cycle related to differential subsidence.

Ultrastructure of muscle cells in Acetabulostoma (Crustacea, Ostracoda) - mussel shrimp from the Ross Sea (Antarctica)

This paper gives the first ultrastructural description of muscle cells in Acetabulostoma sp., a small (less than 1 mm in length) Antarctic ostracod. All muscle cells showed the same ultrastructural pattern: this consisted of mononucleated cells containing a single thick myofibril which was surrounded by numerous mitochondria. The nucleus and most cytoplasmic organelles were also located in the cell periphery. The myofibril showed the ultrastructural pattern of transversely striated muscle. Myofilaments formed well-defined sarcomeres, delimited by Z lines. The average sarcomere lengths were: total sarcomere 4.6 ± 0.9 μm, A band 2.86 ± 0.45 μm (0.178 ± 0.06 μm corresponded to the H band), and I band 1.72 ± 0.58 μm. The myofilament diameters were 5.8 ± 0.3 nm (thin myofilaments), and 14.8 ± 0.68 nm (thick myofilaments). In the same myofibril and in cross sections, some thick filaments appeared homogeneously dense whereas others showed a tubular appearance. Each thick filament was surrounded by 12 thin filaments, and the thin/thick filament ratio was 6/1. The sarcotubular system was well developed and consisted of both transverse and longitudinal components, both running within the myofibril among the myofilaments. The transverse components consisted of 20- to 22-nm-diameter tubules that originated from invaginations of the plasma membrane (T tubules). They penetrated radially throughout each A-I interband and branched inside the myofibril. The longitudinal components consisted of bundles of parallel-arranged sarcoplasmic reticulum saccules running parallel to the myofilaments. Each bundle comprised from three to six 30 to 35-nm-diameter saccules. At the levels of the A-I interbands, the saccules of some bundles fused together to form triads with the T tubules. In the triad, the distance between the sarcoplasmic reticulum tubules and the T tubules was 10–14 nm. The mitochondria were large, presented numerous transverse cristae, and were joined one to another by electron-dense plaques. The muscle cell tips ending beneath the cuticle were connected to a modified epidermal cell by a specialized intercellular junction of the fascia adherens type. This junction occurred at the level of a Z line, and displayed an irregular outline with numerous interdigitations that formed conical projections. The ultrastructural characteristics of the myofibrillar apparatus, the plentiful sarcotubular system and the abundance of mitochondria in Acetabulostoma muscles suggest that this muscle type is concurrently a developed model of both the fast-twitch type and the fatigue-resistant type.

Evolutionary events of Cainozoic Ostracoda of western Philippine Sea and paleoceanographical implications

The Oligocene ostracod fauna of DSDP Site 292 of the western Philippine Sea was marked by high density, diversity and origination, probably reflecting a favorable period for deep sea Ostracoda; while the sharp decrease in density and diversity as well as the repeatedly occurring extinctions in the Neogene may indicate the deterioration in bottom water environments at that time. Five major faunal changes have been recognized in terms of density, diversity and evolutionary activity (origination and extinction), occurring in the earliest Oligocene (P18), mid Oligocene (P21), earliest Miocene (N4), early Middle Miocene (N8) and late Pliocene (N21), respectively. These changes in ostracod faunas are suggested to represent short term events related to global paleoceanographical changes and to record the Cainozoic cooling history of the West Pacific Ocean and Philippine Sea deep water.

Diversity and endemicity of Recent non-marine ostracods (Crustacea, Ostracoda) from Africa and South America: a faunal comparison

(1998). Diversity and endemicity of Recent non-marine ostracods (Crustacea, Ostracoda) from Africa and South America: a faunal comparison. SIL Proceedings, 1922-2010: Vol. 26, No. 4, pp. 2093-2097.

BIOCHRONOLOGY OF SELECTED MAMMALS, MOLLUSCS AND OSTRACODS FROM THE MIDDLE PLIOCENE TO THE LATE PLEISTOCENE IN ITALY. THE STATE OF THE ART

The Authors have elaborated four range charts of mammalian (large and micro), molluscs and fresh-water and brackish ostracodes faunas, for the selected Plio-Pleistocene fossiliferous localities of the Italy. A new Mammal Age (Aurelian) correlatable to late Middle and Late Pleistocene has been defined. Inside this age two Faunal Units (Torre in Pietra and Vitinia) have been defined as characteristic for Early and Middle Aurelian, while no gisements have been chosen for the late Aurelian. Biochronological units are calibrated on magnetostratigraphic and isotopic scales and by radiometric datings.

Microfossils from loess of the Miaodao Islands, Bohai Sea

Microfossils from the Malan Loess profiles, Miaodao Islands, have been quantitatively studied. The microfauna is composed mainly of benthic foraminifers together with a few planktonic foraminifers, ostracods, gastropods, bivalves and echinoid spines. With the exception of indigenous gastropods, benthic foraminifers, ostracods, bivalves and echinoid spines were transported from the north or northwest of the Bohai Sea in the glacial period by the prevailing winter monsoon, while planktonic foraminifers were probably driven from the Yellow Sea or even the northern East China Sea by southerly winds. The upward decrease of marine microfossil abundance and diversity in the Malan Loess profiles shows that the microfossil transportation occurred mainly at the beginning of the regression.

Heterochrony of the ostracod hingement and its significance for taxonomy

Heterochrony of the ostracod hingement and its significance for taxonomy

Uptake of fenvalerate by the ostracod Chrissia halyi (Ferguson).

Uptake of fenvalerate by the ostracod Chrissia halyi (Ferguson).

Determination of Sr/Ca and Mg/Ca ratios in ostracod shells with inductively coupled plasma atomic emission spectrometry

沉积物中介形类壳体的Sr/Ca和Mg/Ca比值可用于湖泊古盐度和古温度的重建。本文从双通道顺序扫描式ICP-AES的特点出发,对μg级介形类样品中的低含量元素Sr和Mg选择最灵敏谱线和最佳通道,对各项条件进行最优化。Sr和Mg的检测限分别为1.1μg╱L和1.4μg/L。本文以此法准确测定了介形类样品中Sr/Ca比值和Mg/Ca比值,回收率实验结果令人满意。;Sr/Ca and Mg/Ca ratios of ostracod shells in lacustrine sediments can be used to reconstruct the palaeotemperature and palaeosalinity of lakes.According to the characteristics of the double channel sequential scan inductively coupled plasma atomic emission spectrometry (ICP-AES), the most sensitive emission lines and optimum channels are chosen to determine trace Sr and Mg of gamma grade ostracod shells sample,while all determined conditions are optimized.The detection limits of Sr and Mg are 1.lμg/L and 1.4/μg/L respectively.In this paper,Sr/Ca and Mg/Ca ratios are accurately determined, and the recovery test is satisfactory.

A note on the Occurrence of Fresh Water Ostracods in the Siwalik Group of Surai Khola Section, Western Nepal

The occurrence of fresh water ostracodes-Candona lactea Baird, Cypria ophthalmica (Jurine), Cyprinotus sp., Jlyocypris gibba (Ramdohr), Limnocythere sp., and Potamocypris sp- is recorded from the Siwalik Group of Surai Khola Section, southeast of Dang in West Nepal.

THE MIDDLE-UPPER TRIASSIC OF THE SAN DONATO UNIT AUCT. (NORTHERN CALABRIA): STRATIGRAPHY, PALEOGEOGRAPHY AND TECTONIC IMPLICATIONS

In this paper are presented stratigraphic and sedimentological data on the carbonate successions occurring in the Cozzo del Pellegrino massif (Cosenza), generally considered as pertaining to the metamorphic San Donato Unit. The successions start with thick phyllites and intercalated carbonate lenses containing Anisian-lower Ladinian algae. To the phyllites follows the informally defined calcari formation, locally occurring also as its lateral equivalent. The calcari formation consists of two members, the first of which (Piano del Minatore Mbr.)consists of black, often marly limestones, showing nodular and bioturbated textures, with a scarce and banal fauna represented by ostracods, gastropods and bivalves. Algal mounds, with porostromata and crinoids are locally intercalated in these facies. In the upper part of the formation the black limestones pass laterally to a reef complex (Monte Caramolo Mbr.) of Ladino-Carnian age, consisting mainly of boundstones with sponges and biogenic crusts, as well as of fore-reef breccias. These lithotypes have been interpreted as deposited on a carbonate ramp evolving to a restricted, poorly oxygenated lagoonal area, bordered by bioconstructed margins. In the lower Carnian a carbonate-marly horizon, containing traces of evaporites, whose thickness is decreasing toward the east, allows a lithostratigraphic correlation betweenmost of the studied successions. The calcari formation is followed by the Scifarello formation, mainly outcropping in the eastern parts of the studied area. It consists generally of tidal dolomites with some tempestites deposited on an shallow open shelf, followed by dolomites and laminated, often marly, dolomitic limestones, deposited in a subtidal, restricted environment. On the basis of foraminifers and bivalves data, the upper part of the Scifarello formation has been ascribed to the upper Carnian-Norian. Moreover, a strong tectonic activity of Lower Norian age is evidenced by the presence of mass-flows and sedimentary dikes in the more easterly areas of the massif. The general paleoenvironmental evolution, in the period spanning between Anisian and Early Norian, can be envisaged firstly in a carbonate sedimentation on a wide shelf, grading toward the east to deeper, possibly basinal areas, whose location was controlled by the Ladinian and/or Norian synsedimentary tectonics. This shelf was bordered on the west by a peri-continental area, with silicoclastic to evaporitic deposits, better represented in the Cetraro area. Finally, the Norian dolomites pertaining to the Verbicaro Unit, usually considered as have been thrusted onto rhe Triassic carbonates of the San Donato Unit, have been often observed to occur in normal stratigraphical superposition over the latter. Therefore, also considering the ambiguous evidence presented in the literature on the Jurassic-Miocenic evolution of the San Donato Unit AUCT, we interpret the Norian Verbicaro dolomites as being the most natural evolution of the Anisian-Lower Norian San Donato lithotypes. It follows that for a really valid paleogeographic reconstruction a complete redefinition of the tectonic units in the whole area is needed.

Further Discussion on the Major Conditions of the Existence of Ostracoda——Taking Hongze Lake in China as Example

Further Discussion on the Major Conditions of the Existence of Ostracoda——Taking Hongze Lake in China as Example

Sub-recent Ostracodes of the Tamandaré Bay, Northeastern Brazil - A Preliminary Report on Biofacies

O estudo dos ostracodes sub-recentes da Baía de Tamandaré, localizada no Estado de Pernambuco, permitiu a determinação de uma associação constituída de trinta gêneros e dezenove espécies e o registro de dois gêneros e vinte e seis espécies indeterminados. Loxocorniculum, Xestoleberis e Kotoracythere, abundantes em recifes orgânicos e ambientes associados, também ocorrem. Por outro lado, Triebelina e Paranesidea, citados por outros autores como característicos de recifes, são muito raros. Esta associação possibilitou a definição de duas biofácies que foram comparadas com três biofácies definidas anteriormente com foraminíferos, para a mesma área.

Post Miocene Ostracodes From Pelotas Basin, Southern Brazil. Taxonomy - Part I

O estudo taxonômico dos ostracodes do intervalo Pós-Mioceno, contidos em sete perfurações, 2-MO-1-RS, 2-CI-1-RS, 2-CA-1-RS, 2-PS-1-RS, 2-PN-1-RS, 2-GA-1-RS e 2-GA-2-RS realizadas pela Petróleo Brasileiro S.A., PETROBRAS, na Bacia de Pelotas no Rio Grande do Sul, permitiu a determinação de Brasilicythere reticulispinosa gen. et sp. nov. e de nove outras espécies novas: Argenticytheretta levipunctata, A. variabilis, Caudites posdiagonalis, Ambostracon crucicostatum, Coquimba bertelsae, Bradleya pelotensis, Henryhowella rectangulata e H. spinosa. Permitiu, ainda, registrar a ocorrência de Cytheretta punctata, Coquimba tenuireticulata, Callistocythere litoralensis e C. marginalis. São apresentadas, também, duas espécies indeterminadas, Protocytheretta sp. e Quadracythere sp.

STRATIGRAPHY, PALEOGEOGRAPHY AND GENETIC MODEL OF LATE CARNIAN CARBONATE BRECCIAS (CASTRO FORMATION, LOMBARDY, ITALY)

The stratigraphic and paleogeographic analysis of the Carnian-Norian boundary succession in central Lombardy allows the recognition of a new unit, the Castro Formation. This unit, 100-250 m thick, is represented by carbonatic intraformational breccias and associated limestones. Two lithozones have been recognized in the Castro Fm.: the lower one, heteropic with the S.Giovanni Bianco Fm., with dark dolomitic limestones and breccias intercalations, and the upper lithozone, massive, with amalgamated calcareous breccias. Microfacies, recrystallized and often tectonized, consist of mudstones, wackestones and fine packstones, locally rich in ostracods. Geochemical analyses show differences between the Castro Fm. and the overlying and underlying units, possibly because of early diagenetic meteoric imprint. The Castro Fm. depositional setting is represented by coastal ephemeral lakes with periodic emersions and erosional, tectonically controlled phenomena in a monsoonal regime.

Muskelfelder eines kirkbyiden Ostracoden aus dem Perm - Beschreibung und Analyse

Muskelfelder eines kirkbyiden Ostracoden aus dem Perm - Beschreibung und Analyse

On Isocypris Beauchampi (Paris) (Ostracoda) and Some Suggestions On the Taxonomy of the Genus

Une population d'Isocypris beauchampi a ete trouvee dans le Lago Campotosto (Italie). C'est la seconde fois que le genre est signale en Italie, apres que Fox a attribue la population du Lago Maggiore a une nouvelle espece, Isocypris nocentiniae. L'analyse comparative de ces populations a conduit a la conclusion qu'I. nocentiniae devait etre considere comme un synonyme d'I. beauchampi. A la suite de l'examen d'autres especes du meme genre, on peut egalement placer I. arnoldi dans la synonymic d'I. beauchampi.