Palaeoenvironmental analysis of Early Pleistocene brackish marshes in the Rieti and Tiberino intrapenninic basins (Latium and Umbria, Italy) using ostracods (Crustacea)

Recent palaeontological and sedimentological studies on the Upper Pliocene–Lower Pleistocene continental deposits of the Rieti and Tiberino basins (Latium and Umbria, Italy) showed the existence of brackish marshes influenced by the Early Pleistocene Tyrrhenian sea. The micropaleontological analyses carried out on five sections cropping out in the northern sector of the Rieti Basin and on one section cropping out in the southwestern branch of the Tiberino Basin showed the repeated alternance of two ostracod assemblages. The first is characterized by a very abundant ostracod association dominated by Cyprideis torosa, typical of brackish waters; the second one is less rich in specimens and dominated by several species of freshwater Candoninae. This alternance allowed the recognition of several changes in the water salinity that could be related to many Early Pleistocene sea-level changes. Palaeosalinities were estimated for both the Tiberino and the Rieti Basin using the morphological analysis of the shell of Cyprideis torosa (ornamentation, nodosities and percentages of sieve-type pore canals). The obtained palaeosalinity values, ranging from freshwater to oligohaline, show slightly higher salinities for the Tiberino Basin, located nearer the ancient coastline, than for the Rieti Basin.     

Distribution of Cyprideis torosa (Ostracoda) in Quaternary Athalassic Sediments in Germany and its Application for Palaeoecological Reconstructions

Cyprideis torosa (Jones , 1850) is a very common brackish water ostracod of the German coasts, but, despite empty valves are found occasionally in surface sediments of some modern inland waters, C. torosa could not be found living in modern athalassic waters of Germany so far. During interglacial periods, including the Holocene, however, fossils of this species are quite common in Central Germany, at a distance of more than 300 km away from the coasts of the Baltic and North Seas. All 31 Quaternary localities with C. torosa known so far from Germany are documented. C. torosa is an indicator for brackish waters and widely used as index‐fossil in palaeosalinity reconstructions relying on water chemistry bound morphological changes (nodes, sieve‐pores). The comparisons imply a general underestimation of palaeosalinity in oligo‐ to mesohaline athalassic waters if using nodes and sieve‐pores of C. torosa as proxy. A water chemistry (ionic composition) driven morphological response is assumed instead one by salinity only. Palaeosalinity estimations for athalassic waters, relying on morphological variability alone, should therefore be used with caution. Palaeosalinity trends, however, can be detected. Distinguishing thalassic and athalassic sediments with C. torosa is possible by using the associated ostracod fauna as a discriminator. Regarding the ecology and distribution of C. torosa, permanent, brackish, and shallow water bodies under relatively warm conditions are required for its settlement. The source of the salt are brines originating from Zechsteinian or Triassic underground evaporites. Warm and relatively dry climates could enhance the process for such water bodies of becoming salty, a situation present in Holocene Central Germany. The occurrence of C. torosa can therefore be used for palaeoclimatological studies. The most probable migration path of this ostracod species to athalassic waters is by avian transport. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Trend,signal and noise in the ecology of Ostracoda: information from rare species in low-diversity assemblages

Samples of Ostracoda from nearshore marine environments, where the water is more likely to be brackish or hypersaline, typically have low species diversity and are dominated by such species as Cyprideis torosa. In high-diversity samples from normal-marine environments, rare species are likely to contribute to environmental noise. Evaluation of low-diversity samples from Lake Manzala, Egypt, however, shows that the environmental signal provided by rare species can be masked by the overwhelmingly dominant species, C. torosa. In such instances, the dominant species should be removed from the data set and studies based on a large sample of the rare species.     

Histological peculiarities of the noding process in Cyprideis torosa (Jones) (Crustacea, Ostracoda)

The noding of Cyprideis torosa is investigated. Studies reveal structural changes in the ornamentation and the cellular layers of the epidermis in the noded area. Noding is caused by the inability of the animal to regulate the increasing osmotic pressure during moulting in low saline water. Therefore it must be considered as a phenotypic and not a genetic response.     

Growth and respiration of Cyprideis torosa Jones 1850 (Crustacea Ostracoda)

Summary The ostracod Cyprideis torosa Jones 1850 is a dominant species in brackish water habitats. To assess its importance, growth and respiration were measured. The shells form an increasing part of total weight as the animals grow but there is no correlation between shell weight and soft parts weight in the adults, indicating that tissue growth is a continuous process in these ostracods.Respiration was measured at 20° C. The slope of the log-log regression of respiration on dry weight was 0.746, showing that Cyprideis torosa follows the general rule for this relationship. The respiration rate per unit biomass was 0.246 nl O₂ g^-1 h^-1, which is low but well within the range of observed meiobenthic respiration rates.The Q₁₀, expressing the temperature dependence of respiration, was 2.15. The general validity of Price and Warwick's (1980) hypothesis relating Q₁₀ to stability of food supply is questioned.     

Noding of Cyprideis torosa valves (Ostracoda) – a proxy for salinity? New data from field observations and a long‐term microcosm experiment

Cyprideis torosa (Jones , 1850) (Ostracoda, Crustacea) is one of the most common marginal marine ostracod species in the Northern hemisphere. We investigate the relationship between variable noding of its valves and salinity as well as Ca²⁺ concentration in the ambient water, analysing populations from an in vitro experiment and field data from the southern Baltic Sea coast. There is a clear negative linear correlation between the proportion of noded individuals from our microcosms and salinity. Deficiency of Ca²⁺ causes heavier noding in laboratory cultures. The same effect can be seen in the field, however, the increase of noded individuals with falling salinity appears to be stepped, not linear. This pattern probably reflects the ability of the animals to wait some time until better salinity conditions occur within the highly variable conditions of estuaries and lagoons. At the southern Baltic Sea coast, proportions of more than 20% noded valves within a C. torosa population indicates salinities of up to 2 psu, up to 10% noded valves indicate salinities between 2 and 7 psu, and the lack of noded valves salinities > 7 psu. Stable salinity conditions as in the studied microcosms cause a shift of these salinity limits to 5 and 14 psu approximately but in a linear relationship between salinity and proportion of noded individuals. Hence, athalassic populations from more stable water bodies should be used for continuous and more detailed salinity trend reconstructions. Deficiency of Ca²⁺ (approximately < 120 mg/l) effects up to about 20% more noded individuals than in water with same salinity but with higher Ca²⁺ concentrations. The reproduction rates within the microcosms indicate a salinity optimum of C. torosa eggs of 8 psu whereas the optimum of the adults seems to be at least 14 psu (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Size and environmental salinity in the modern euryhaline ostracod Cyprideis torosa (Jones, 1850), a biometrical study

Samples from living populations of the ostracod Cyprideis torosa, taken at various inland brackish-water localities in The Netherlands, are biometrically analyzed. A negative correlation is found between the mean size of the carapace (adult females) and the salinity level of the environment. The results are discussed and compared with published data on the size-salinity relationship in ostracods.     

Genetic variation in two widespread species of salamanders,Taricha granulosa and Taricha torosa

Two species of the genus Taricha are widely distributed. T. granulosa ranges from southern Alaska to central California. T. torosa is comprised of two described subspecies, T. t. torosa, which occupies much of the coast ranges of California, and T. t. sierrae, which inhabits the western slopes of the Sierra Nevada Mountains. A starch gel electrophoretic survey for genetic variation at 34 loci in four population samples of T. granulosa and at 40 loci in five population samples of T. torosa reveals differences among these taxa both in amounts of intrapopulational variability and in patterns of geographic variation. Average observed heterozygosity is 9.6%±0.3% in T. granulosa, 3.3%±0.5% in T. t. torosa, and 7.2%±1.2% in T. t. sierrae. Average numbers of alleles per locus and proportions of polymorphic loci are also highest in T. granulosa, intermediate in T. t. sierrae, and lowest in T. t. torosa. Oregon and California granulosa are genetically nearly as different as the subspecies of torosa, but geographic variation is continuous in the former. T. torosa on the other hand is comprised of three distinct gene pools—T. t. sierrae and northern and southern races of T. t. torosa. Strikingly different amounts of intrapopulational genetic variation and patterns of geographic variation may be explained by steadystate species differences, but historical causes may also exist.This work was supported by AEC Research Contract AT(04-3)34 and NSF Grant GB-42246 to F. J. Ayala and by an NIH predoctoral traineeship administered by the Department of Genetics, U.C. Davis.     

Variable noding in Cyprideis torosa (Ostracoda,Crustacea): an overview,experimental results and a model from Catastrophe Theory

Various anomalohaline ostracod species will, under certain conditions, develop hollow, outward flexions of the lateral surface of their carapace that are called nodes. While the potential positions on the shell surface of such nodes are normally fixed, their number and relative strength are variable. This phenomenon, which is called variable noding, is best known in Cyprideis torosa (Jones, 1850) but it actually features in several more species of Cyprideis and other cytherideinid genera, both Recent and fossil. Alternately explaining it as ecophenotypic or genotypic, nearly all primary sources in the literature associate variable noding with low environmental salinity. Culturing results confirm that the phenomenon reflects a direct physiological response rather than a genotypic adaptation. From the cultures, it also appears, however, that there is yet another factor active, in addition to and interfering with environmental salinity. This factor is provisionally called `factor X'. The experiments suggest that factor X may represent either the pH or the CO₂ content of the ambient water, and hence be directly related to dissolved CaCO₃. With two interfering factors, variable noding can possibly be described by the cusp model of Catastrophe Theory with salinity and factor X as the controls and noding capability as the resultant reaction surface. Lacking sufficient calibration, the model must remain qualitative for the time being. Further experimentation and careful observation in the field should allow its quantification, thus clearing the path for palaeoecological application.     

Distribution and population dynamics of ostracodes (Crustacea,Ostracoda) in a karstic lake: Lake Banyoles (Catalonia,Spain)

Qualitative and quantitative benthic samples were collected monthly between December 1986 and December 1987 from several stations at various depths and basins in the karstic Lake Banyoles (Catalonia, Spain), to study the spatial distribution and seasonality of ostracodes. A total of eight ostracode species were found in the lake. Of these, Candona neglecta Sars, Isocypris beauchampi Paris and Cypria ophtalmica Jurine were the most common ostracodes at all depth stations. Darwinula stevensoni Brady & Robertson, Ilyocypris species (I. bradyi Sars and I. gibba (Ramdohr)), Cyprideis torosa (Jones) and Cyclocypris ovum Jurine, on the other hand, were confined to sublittoral and littoral areas of the lake.Substrate and organic matter content appeared to be relevant factors determining the distribution of ostracode species at the different stations. The highest abundance of ostracodes were in the sublittoral (Basin IV–7 m and Basin I-5 m) where the substrate was coarse and sediment had a high organic matter content (>35% LOI). Low oxygen levels in the hypolimnetic waters (i.e. < 1 mg l^–1) may explain the absence of ostracodes at deeper zones in stations where the anoxic period lasts more than four months. On the other hand, low temperatures seem to favour the development of C. neglecta and D. stevensoni, while with higher temperatures I. beauchampi, C. torosa and C. ovum increased their abundances. However, no clear pattern can be observed, so ostracode species in Lake Banyoles, apparently, have non-seasonal life histories.     

Les Ostracodes et le Quaternaire d’Aigion (golfe de Corinthe, Grèce)

The Upper Pleistocene and the Holocene of Aigion have delivered an abundant microfauna with 35 ostracode species. The Pleistocene from Aigion borehole generally provides Ostracodes from oligohaline environment with Cyprideis torosa, Candona angulata and Tyrrhenocythere amnicola while, in the Holocene, marine infralittoral species dominate with Cytheridea neapolitana, Carinocythereis whitei, Loxoconcha ovulata and Cytherois frequens. The marine sedimentation occurred at depth from some meters to some tens of meters. In the Aghios Constantinos section, the lagoonal marls are characterised by Euxinocythere schuldtae and a dwarf species of Xestoleberis. Then, a drastic environmental change occurs around the Pleistocene-Holocene boundary and presumably affected the whole Corinth gulf.     

The genus Cyprideis Jones, 1857 (Crustacea,Ostracoda) in the Neogene of Italy: A geometric morphometric approach

As a result of the use of geometric morphometrics, multivariate statistics and classical morphological observations the authors propose a taxonomic revision of the Neogene Italian Cyprideis species. On this basis, the Cyprideis valves collected in Tortonian, Messinian and Pliocene brackish deposits of Italy are referred to 12 species, six of which are new: Cyprideis alexandri nov. sp., Cyprideis arvedoi nov. sp., Cyprideis lepianensis nov. sp., Cyprideis rooki nov. sp., Cyprideis strollae nov. sp., and Cyprideis toscana nov. sp. Some species are rather widespread in the Italian Peninsula (Cyprideis ruggierii Decima and Cyprideis crotonensis Decima) or even in the whole Palaeomediterranean (Cyprideis agrigentina Decima and Cyprideis anlavauxensis Carbonnel). For C. ruggierii, C. agrigentina and C. crotonensis, a phyletic relation is suggested. The new species are confined both geographically and stratigraphically in several Tuscan athalassic brackish basins, suggesting endemic speciation similar to those occurring in ancient lakes.     

Population fluctuations of Heterodera rostochiensis Woll. when susceptible potato varieties are grown continuously

When seven potato varieties susceptible to Heterodera rostochiensis were grown every year on the same small plots for 6 years with precautions to minimize soil movements, yields were inversely proportional to the number of larvae in the soil before cropping in the first year only. With all the varieties, numbers of larvae after harvest fluctuated around mean values and the fluctuations became smaller in successive years. Although conditions from year to year were as uniform as possible, there were differences in weather, incidence of potato blight (Phytophthora infestans), seed size and quality, and in planting dates. Analysis of soil temperatures and of heat accumulation did not suggest that conditions after planting caused the fluctuations. The smaller fluctuations with repeated cropping probably reflect the influence of population density on the size of the root system and are what would be expected from the curve relating pre- to post-cropping numbers, which reaches a maximum before the reproductive rate decreases to unity. A resistant potato hybrid ex andigena, also grown every year, usually outyielded the susceptible varieties and, by the sixth year, yielded at least twice as much as the mean of the six susceptible varieties.     

YEAR-TO-YEAR CHANGES IN PHENOTYPIC GENDER IN A MONOECIOUS CUCURBIT,APODANTHERA UNDULATA

Year-to-year variation in phenotypic gender in the monoecious cucurbit, Apodanthera undulata Gray was investigated. Small plants produce no flowers. Larger plants produce only staminate flowers (“male” plants), while a somewhat greater threshold size is necessary for pistillate flower production (cosexual plants). Approximately 85% of the plants that bloomed did not change gender group between years. Two measures of phenotypic gender were used: prospective femaleness, a measure standardized to the population floral ratio, and morphological femaleness, an unstandardized measure. Femaleness of cosexes between years was positively correlated; r values were somewhat greater when using morphological femaleness values. Plants that opened only staminate flowers one year were likely to open only staminate flowers the next year. Similarly, cosexes were likely to be cosexes again the following year, with similar femaleness values. Beyond the threshold size for pistillate flower production, plant size was not correlated with femaleness. These patterns suggest that all plants are male until they reach a certain size and that plants in their cosexual phase may have an intrinsic femaleness tendency due to either genotype or microsite effects.     

Late Glacial and Holocene Ostracoda of the Gulf of Gdańsk,the Baltic Sea,Poland

To trace environmental changes in water hydrology and salinity in the Late Glacial to Holocene of the Gulf of Gdańsk, a south‐eastern bay of the Baltic Sea within the maritime zone of Poland, the distribution of ostracod valves was studied in 20 sediment cores collected from both the shallow‐ and deep‐water zones (depth 10.9–67.5 m). The studied sediment sequences yielded ca. 3000 valves of 21 ostracod species, of which only five are known to live today in the Gulf, which has a present maximum depth of 118 m and water salinity up to 7–8‰. The majority of the studied sediment layers that contained ostracod valves corresponded to the period of the Late Glacial to Mid‐Holocene and was dominated by non‐marine species, of which the most common were Candona neglecta (present in 17 cores), Cytherissa lacustris (15 cores) and Candona candida (14 cores). By clustering classification five major ostracod assemblage types were recognised in the studied cores. Initial assemblage types dominated mostly by inhabitants of the profundal/sub‐littoral zones of modern oligo‐mesotrophic lakes (C. lacustris and C. neglecta) in some sediment sequences were replaced in stratigraphical order by the assemblages dominated by brackish‐water species (Cyprideis torosa or Cytheromorpha fuscata). The structure and species composition of the distinguished ostracod assemblage types as well as their successional transitions indicate that the studied sediments were deposited initially in the Late Glacial in freshwater lacustrine conditions, and subsequently, during the Holocene marine transgression, covered by marine sands. The present results confirm and consolidate inferences based on previously published data on ostracods from the western part of the Gulf of Gdańsk as well as on other biotic (molluscs, diatoms) and abiotic (seismoacoustic) indices from this area (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Coastal evolution and Holocene ostracods in Melides lagoon (SW Portugal)

A multidisciplinary study covering sedimentology (texture, carbonate and organic matter content, clay mineralogy), geochemistry (major, minor and trace elements, isotopes), palaeoecolgy (ostracods) and isotopic dating (¹⁴C) has been carried out on two long cores (MB-40.0 m and MIGM-34.0 m) retrieved from the barrier and the alluvial plain margining the Melides lagoon (south-western coast of Portugal). The interpretation of the whole data set allowed the establishment of an evolutionary model for this lowland since the Late Glacial. This model includes four stages. It starts with a fluvial terrestrial environment, replaced by an estuarine to fully marine one (circa 9500 cal BP), due to the rapid rise in sea level recorded during the first phase of the Holocene transgression. The deceleration of sea level rise favoured the emplacement of a sandy barrier (circa 5900 cal BP) that promoted the differentiation of a coastal lagoon which has been progressively filled with fluvial sediments.The ostracod fauna in both locations includes 38 species of littoral to sublittoral/phytal marine forms (mainly Urocythereis britannica, Carinocythereis whitei, Loxoconcha rhomboidea, Pontocythere elongata, Semicytherura sella, Semicytherura acuta, Basslerites cf. berchoni, Hiltermannicythere emaciata) and brackish water forms (Cyprideis torosa, Loxoconcha elliptica), which clearly characterize the signature of both the marine and lagoonal episodes, respectively.     

Palaeoecological evidences from foraminifers and ostracods on Late Quaternary sea-level changes in the Ombrone river plain (central Tyrrhenian coast,Italy)

The multidisciplinary study of borehole Ombrone S1, sampled in the Grosseto plain, near the Ombrone river mouth, provides new data about sea-level changes during the Holocene in central Tyrrhenian Sea. The palaeontological analysis of the borehole highlights data concerning the foraminifers and ostracods useful to the palaeoenvironmental interpretation. Moreover, geochemical analyses (δ¹³C and δ¹⁸O) were performed on Ammonia parkinsoniana tests and Cyprideis torosa valves. Integrating the results of the palaeontological, lithological and geochemical data, it is possible to single out the environments related to the transgressive trend. Borehole Ombrone S1 is characterised by basal deposits of continental settings, which includes some brackish water marsh, may be related to a slight sea-level oscillation, followed by fluvial gravel ones testifying the deltaic progradation of the Palaeo-Ombrone river. Above, two distinct trangressive events, which were divided by a phase of still-stand, took place. The first one, above the gravel, was responsible for the establishment of the brackish water conditions due to the presence of a barrier-lagoon system, which was finally filled up by terrigenous input. The second one produced, at first, lagoon settings near the sea and, successively, deltaic-related settings for the submersion of the barrier. The littoral sandy bar at 10 m of core-depth represents the first sure evidence of the alluvial plain progradation, which develops up to the core-top.     

Ostracods and the Holocene palaeolimnology of Lake Qarun, with special reference to past human–environment interactions in the Faiyum (Egypt)

We present an ostracod record covering the past two millennia from an 8.25-m core taken from Lake Qarun, in the Faiyum Depression of Egypt. The occurrence of ostracod species in the lake is controlled primarily by variations in solute composition, which are in turn related to shifts in catchment land use. At times when the Faiyum Depression supported thriving agriculture, lake water contained Na⁺–Cl^? brine, and Cyprideis torosa dominated the ostracod assemblage. When the Faiyum Depression experienced periods of environmental and economic decline, lake water contained Na⁺–HCO₃ ^? brine, and Limnocythere inopinata dominated. The relative abundance of other ostracod species provides additional information about past conditions in Lake Qarun including salinity and lake level changes. Overall, the ostracod assemblages provide evidence for human influences in the Faiyum, which extend back before instrumental or detailed observational records began.     

Very long diapause and extreme resistance to population disturbance in a galling insect

1. Some insects have a prolonged diapause – a dormancy that extends over more than 1 year. In most species prolonged diapause involves one or a few extra years, but in extreme cases diapause may surpass 10 years. Few cases of very long diapause have been described, and very little is known about the population consequences of the temporal refuge formed by the diapausing individuals. 2. The gall midge Contarinia vincetoxici Kieffer galls the flowers of a long‐lived herb Vincetoxicum hirundinaria Med. After completing development, larvae leave the galls for the ground where they enter diapause. Extending an earlier published inoculation experiment, we show that the diapause may last up to at least 13 years, with a median duration of at least 6 years. 3. The gall midge is attacked by two parasitoid species. Dissections of gall midge larvae for presence of parasitoids revealed that Omphale salicis Haliday had a maximum 2 year diapause and Synopeas acuminatus Kieffer a maximum 4 years. The very long diapause of the gall midge may thus provide a temporal refuge from these enemies. 4. In a 15‐year field experiment all galls were removed every year from six isolated habitat patches. Density changes in experimental populations were not statistically different from control populations for over a decade. After 14–15 years a modest decline could be observed. This slow response illustrates that prolonged diapause in C. vincetoxici provides a very strong population buffer against mortality during the galling stage.