NEW JELLYFISH TAXA FROM THE UPPER JURASSIC LITHOGRAPHIC LIMESTONES OF CERIN (FRANCE): TAPHONOMY AND ECOLOGY

Abstract:  Abundant well-preserved jellyfish impressions are described from the Cerin Lagerstätte (Ain, eastern France). The enclosing sediments are lithographic limestones deposited in a Late Kimmeridgian lagoon lying on an emergent reef complex. Two new taxa of Scyphozoa are proposed: Paraurelia cerinensis gen. et sp. nov. (abundant) and Paraurelia sp. A (rare), and two new taxa of Cubozoa: Bipedalia cerinensis gen. et sp. nov. (rare) and Paracarybdea lithographica gen. et sp. nov. (very rare). Rapid covering by a microbial mat helped the preservation of the animals. Many specimens of Paraurelia cerinensis are deformed by slippage down the palaeoslope, which characterizes the margin of the lagoon. Their resultant morphology and their orientation clearly indicate the downslope direction. Tentacles of Bipedalia cerinensis and Paracarybdea lithographica are also orientated according to the palaeoslope. The jellyfish were probably dead individuals occasionally introduced into the Cerin lagoon. However, another hypothesis may be considered with reference to the model of the present-day jellyfish lakes in Palau (Caroline Islands, Western Pacific). Jellyfish could have lived in the more oxygenated upper layer of water of the Cerin lagoon that allowed pelagic life. This situation could have corresponded to short periods of easier communication between the open sea and the lagoon. Jellyfish are only found in the lower beds of the lithographic limestones and their distribution illustrates the supposed evolution of the Cerin lagoon. Initially, it was deep, mainly flooded, with possibly autochthonous jellyfish and allochthonous animals indicating clear marine influence. Later, the lagoon shallowed and its sediments often emerged with marginal marine burrows and plants indicating increasing terrestrial influence.     

Test structure and evolution in the Foraminifera

For about a decade shell structures have formed the basis of the main taxonomic subdivision of the Foraminifera. Recent investigations have shown that within the monolamellar nodosariaceans no evolution with respect to wall structure has taken place since the Permian. The bilamellar aragonitic forms have remained stable at least since the Jurassic (Triassic?). The bilamellar calcitic forms have remained stable since the Jurassic (Triassic?). The wall structure of the non-lamellar porcellaneous forms has shown no change since the Carboniferous. The non-lamellar monocrystalline forms first occurred in the Upper Carboniferous and appear to have remained stable ever since. The microgranular Foraminifera, first appearing in the Cambrian, disappeared in the Triassic. Their primary structure is not known. The agglutinated forms seem to have started in the Cambrian, if not before. Evolutionary development leading to a higher degree of complexity of shell structure seems to be present (agglutinated—porcellaneous—monocrystalline—monolamellar and bilamellar), and may culminate in a more phylogeny-oriented systematic subdivision than the one we have today.     

VARIABILITY OF THE GENITAL SYSTEM OF HELIX POMATIA L., 1758 AND H. LUCORUM L., 1758 (GASTROPODA: STYLOMMATOPHORA)

This paper examines the variability of the genital characters ofHelix pomatia and H. lucorum. Some of these characters are commonlyused to distinguish the two closely related species. Variationswithin and between populations are also investigated. The highvariability of these characters can frequently lead to identificationerrors, especially in eastern Europe. Correct identificationof these edible snails is also of commercial importance, differentspecies having a different price. The reciprocal nature of themale parts of the genitalia and the bursa stalk and diverticulumcomplex is pointed out. A possible function of the diverticulumis suggested on the basis of size relations between genitalsystem features. (Received 12 August 1999; accepted 11 April 2000)     

Phosphorus recycling in photorespiration maintains high photosynthetic capacity in woody species

Leaf photosynthetic CO₂ responses can provide insight into how major nutrients, such as phosphorus (P), constrain leaf CO₂ assimilation rates (A_net). However, triose‐phosphate limitations are rarely employed in the classic photosynthesis model and it is uncertain as to what extent these limitations occur in field situations. In contrast to predictions from biochemical theory of photosynthesis, we found consistent evidence in the field of lower A_net in high [CO₂] and low [O₂] than at ambient [O₂]. For 10 species of trees and shrubs across a range of soil P availability in Australia, none of them showed a positive response of A_net at saturating [CO₂] (i.e. A_max) to 2 kPa O₂. Three species showed >20% reductions in A_max in low [O₂], a phenomenon potentially explained by orthophosphate (P_i) savings during photorespiration. These species, with largest photosynthetic capacity and P_i > 2 mmol P m^?2, rely the most on additional P_i made available from photorespiration rather than species growing in P‐impoverished soils. The results suggest that rarely used adjustments to a biochemical photosynthesis model are useful for predicting A_max and give insight into the biochemical limitations of photosynthesis rates at a range of leaf P concentrations. Phosphate limitations to photosynthetic capacity are likely more common in the field than previously considered.     

The Contribution of TRPV4-Mediated Calcium Signaling to Calcium Homeostasis in Endothelial Cells

A large variety of cation transport systems are involved in the regulation of calcium homeostasis in endothelial cells. The focus of the present study is to determine the contribution of nonselective cation channels from the TRP (transient receptor potential) family to cellular calcium homeostasis of porcine aortic endothelial cells (PAEC). One member of the TRPV (vanniloid) subfamily, TRPV4, has previously been shown to be involved in cation transport induced by a large variety of stimulations including osmolarity, temperature, mechanical stress, and phosphorylation. Here, we demonstrate the existence of several TRP proteins, including TRPV4, in PAEC using RT-PCR. To test whether this channel is functional, we performed FURA-2 calcium measurements and whole-cell patch-clamp experiments. We observed the induction of large calcium signals following mechanical stress, altered extracellular temperature, and the selective TRPV4 activator 4-α -PDD. These effects were diminished in the presence of the TRPV4 inhibitor miconazole, suggesting the involvement of this channel in mediating endothelial calcium signals. The large amounts of transported calcium and the short signaling ways suggest a potentially important role of this channel in many physiological processes.     

Ultrastructure of Acrasis rosea,a Cellular Slime Mold,During Development*

SYNOPSIS. An ultrastructural study of the myxamoebae of Acrasis rosea in the vegetative, aggregative and culminative stages was made. An intracytoplasmic system of microfibrillar bundles develops as the cells enter the aggregative stage and commence the morphogenetic sequence leading to the construction of a fruiting body. The fibrillar bundles disappear in the cells of the mature fruiting body. No relevant ultrastructural differences were observed between spores, stalk cells and microcysts. Each of these cells is surrounded by a single-layered coat of fibrillar material that is oriented parallel to the cell surface. Tubular structures were observed between the plasma membrane and the cell coat. The tubules may be layered along the cell periphery or they may be recessed in pockets formed by the plasma membrane. They resemble lomasomes typical of fungal cells. The myxamoebae of A. rosea clearly differ from the Dictyostelium-type myxamoebae in mitochondrial structure, the presence of lamellate structures in the nucleolus and the absence of prespore vacuoles.     

Spatio-temporal population genetics of the Danish pine marten (Martes martes)

A spatio-temporal study of genetic variation in the Danish pine marten ( Martes martes ) populations from the Jutland peninsula and from the island of Sealand was performed using 11 microsatellite markers. Samples obtained from 1892 to 2003 were subdivided into historical (prior to 1970) and recent (from 1970) groups. As compared with the historical samples, there was a significant loss of genetic variation in the recent Jutland population, but not in Sealand. Effective population sizes were estimated using Bayesian-based software (TMVP). Historical effective population sizes were 5897 (90% highest probability density, HPD, limits: 1502–6849) in Jutland and 1300 (90% HPD limits: 224–5929) in Sealand, whereas recent effective population sizes were 14.7 (90% HPD limits: 10.9–23.5) in Jutland and 802 (90% HPD limits: 51.8–5510) in Sealand. Significant genetic differentiation ( F _ST) was found between the two historical samples, between the two recent samples, and between the historical and the recent sample in Jutland; whereas the F _ST value between the historical and the recent sample in Sealand was not significant. The significant genetic differentiation between the historical and the recent samples indicates changes in the genetic compositions over time, and the higher F _ST values between the two recent samples, as compared with the two historical samples, indicates that the populations in Sealand and Jutland have drifted apart within a short time span. No deviation from Hardy–Weinberg equilibrium was found within populations, indicating no further substructuring.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 457–464.     

Composition and dispersal of riverine and lake phytoplankton communities in connected systems with different water retention times

1. Lake phytoplankton community structure may be influenced by both internal factors (predation, competition, resource constraints) and external ones, such as dispersal of materials and cells between connected habitats. However, little is known about the importance of cell dispersal for phytoplankton community structure in lakes. 2. We investigated the abundance and dispersal of phytoplankton cells between connected rivers and lakes, and analysed whether similarities in phytoplankton community composition between rivers and lakes were primarily related to cell import rates or to characteristics of the local habitat. We focused on lakes along a gradient of theoretical water retention times (TWRT). Two data sets from Swedish lakes were used; a seasonal study of two connected boreal forest lakes, differing in TWRT, and a multi‐lake study of 13 lakes with a continuous range of TWRTs. 3. Phytoplankton cells were transported and dispersed in all investigated rivers. In the seasonal study, cell import rates and similarities in phytoplankton community composition between the lake and its inlet(s) were much higher in the lake with a shorter TWRT. Phytoplankton community structure in different habitats was associated with total organic carbon (TOC). This indicates that local habitat characteristics may be important in determining lake phytoplankton community composition, even in the presence of substantial cell import. 4. The multi‐lake study also showed a negative relationship between TWRT and similarities in phytoplankton community composition between inlets and lakes. Moreover, similarity in community structure was related to both cell import rates from inlet to lake and differences in habitat characteristics between inlet and lake. However, the variable most strongly correlated with community structure was TOC, indicating that species sorting rather than a mass effect was the most important mechanism underlying the correlation between community structure and retention time. 5. Overall, our data suggest that local habitat characteristics may play a key role in determining community similarity in this set of lakes covering a large range of habitat connectedness. Due to the strong co‐variations between cell dispersal and TOC, it was hard to unequivocally disentangle the different mechanisms; hence, there is a need for further studies of the role of dispersal for phytoplankton community structures.