Barbafera carnica Senowbari-Daryan, 1980: A Triassic worm-tube

Summary Barbafera carnica Senowbari-Daryan (1980), a Carnian reef fossil of uncertain systematic position, is redescribed based on extraordinarily preserved material from Carnian reef boulders of the Cassian Formation of the Southern Alps (Dolomites/Italy).Barbafera is interpreted as a worm tube characterized by a complicated wall structure.Barbafera may belong to the family SerpulidaeRafinesque.     

The Endothelin ETA Receptor Exists in the Caudal Solitary Tract Nucleus of the Rat Brain

1. The receptor autoradiographic method done on the rat lower brain stem and cerebellum plus ¹²⁵I-endothelin-1, BQ-123, an antagonist for the endothelin ET_A receptor, and sarafotoxin S6c, an agonist for the ET_B receptor, revealed minute amounts of the ET_A receptor coexisting with the ET_B receptor in the caudal solitary tract nucleus of the rat lower brain stem.2. The ET_B receptor is present predominantly in other parts of the lower brain stem.3. Knowledge of the heterogeneous distribution of the central endothelin receptor subtypes aids in understanding the neurophysiology of endothelins.     

‘Stromatolites’ built by sponges and microbes – a new type of Phanerozoic bioconstruction

Two ‘stromatolites’ from Carboniferous and Triassic carbonates previously regarded as microbial bioconstructions are analysed and reinterpreted as sponge‐microbial build‐ups. The automicritic aggregations in these build‐ups are similar to the previously reported fossils of keratose demosponges in showing moulded anastomosing filamentous structures. All the studied columnar or domal constructions were formed in turbulent water with high sedimentation rate. The Carboniferous build‐ups were constructed in the shallow subtidal zone of an open shelf or a ramp. The laminations within the stromatolite‐like columns are composed of alternating dark micritic laminae of sponge fossils and pale laminae of neomorphic microspars. The accretion of these columns is probably related to the repeated cycles of sponge growth, rapid lithification after burial, re‐exposure and erosion, and settlement of new generations. The Triassic rocks are presumed to have been precipitated in a slightly evaporitic environment based on lithological features. They show a transition from planar laminae, which were formed under the influence of microbial mats, to stromatolitic columnar or domal build‐ups, which are dominated by stacked micritic clumps of probable sponge fossils. The sponge–microbe alternation may have been controlled by variation of salinity. Comparable with a recent study, this work shows that sponge‐related bioconstructions can be morphologically similar to microbialites in the level of mega‐ and mesostructures.     

Separating the contribution of the upper and lower mesophyll to photosynthesis in Zea mays L. leaves

The appearance of transverse sections of maize leaves indicates the existence of two airspace systems serving the mesophyll, one connected to the stomata of the upper epidermis and the other to the stomata of the lower surface, with few or no connections between the two. This study tests the hypothesis that the air-space systems of the upper and lower mesophyll are separated by a defined barrier of measurable conductance. A mathematical procedure, based on this hypothesis, is developed for the quantitative separation of the contributions made by the upper and lower halves of the mesophyll to carbon assimilation using gasexchange data. Serial paradermal sections and three-dimensional scanning-electron-microscope images confirmed the hypothesis that there were few connections between the two air-systems. Simultaneous measurements of nitrous-oxide diffusion across the leaf and of transpiration from the two surfaces showed that the internal conductance was about 15% of the maximum observed stomatal conductance. This demonstrates that the poor air-space connections, indicated by microscopy, represent a substantial barrier to gas diffusion. By measuring the CO₂ and water-vapour fluxes from each surface independently, the intercellular CO₂ concentration (c _i) of each internal air-space system was determined and the flux between them calculated. This allowed correction of the apparent CO₂ uptake at each surface to derive the true CO₂ uptake by the mesophyll cells of the upper and lower halves of the leaf. This approach was used to analyse the contribution of the upper and lower mesophyll to CO₂ uptake by the leaf as a whole in response to varying light levels incident on the upper leaf surface. This showed that the upper mesophyll was light-saturated by a photon flux of approx. 1000 mol·m^-2·s^-1 (i.e. about one-half of full sunlight). The lower mesophyll was not fully saturated by photon fluxes of nearly double full sunlight. At low photon fluxes the c _i of the upper mesophyll was significantly less than that of the lower mesophyll, generating a significant upward flux of CO₂. At light levels equivalent to full sunlight, and above, c _i did not differ significantly between the two air space systems. The physiological importance of the separation of the air-space systems of the upper and lower mesophyll to gas exchange is discussed.Abbreviations and symbols A net leaf CO₂ uptake rate - A _upper ^app. and A _lower ^app. net rates of CO₂ uptake across the upper and lower surfaces - A _upper and A _lower derived net rates of CO₂ uptake by the upper and lower mesophyll - A _upward net flux of CO₂ from the lower to upper mesophyll - c _a, c _{a, upper} and c _{a, lower} the CO₂ concentrations in the air around the leaf above the upper surface and below the lower surface - c _N2O the concentration of N₂O in the air around the leaf - c _i, c _{i, upper} and c _{i, lower} the mesophyll intercellular CO₂ concentration of the whole leaf, the upper mesophyll and the lower mesophyll - g _i leaf internal conductance to CO₂ - g _s, g _{s, lower} and g _{s, upper} the stomatal conductance of the whole leaf, the lower surface and the upper surface - g the total conductance across the leaf - Q the photosynthetically active photon flux density     

Über die Kalkausscheidungen beiMonophyllaea horsfieldii (Gesneriaceae)

The lower surface of the leaf (macrocotyledon) ofM. horsfieldii is heavily calcified. SEM investigations reveal that the cristalline depositions of CaCO₃ (mainly needles, but also clump-like structures) are excreted by the head cells of two-cellular trichomhydathodes. First, a cap-like structure is formed. As the excretion continues, the cap takes on the shape of a hat with wide brim. Thus, the dense layer of CaCO₃ depositions is composed of hat-like structures whose brims at least partially touch. There is no evidence for the excretion of CaCO₃ by cells other than trichomhydathodes.

     

The phylogenetic significance of sperm morphology in the Platyhelminthes

The phylogenetic significance of flatworm sperm morphology is discussed against the background of general spermatology. The modified type of spermatozoon of the Nemertodermatida, a group of primitive flatworms, indicates that the Platyhelminthes evolved from forms characterized by the primitive type of metazoan sperm and by the primitive mode of fertilization, implying the release of sperm freely into sea water.The occurrence of aberrant types of spermatozoa in most platyhelminths is obviously a consequence of early evolution of the internal mode of fertilization, which characterizes all true members of this group. It can be concluded, from the ultrastructure of these aberrant spermatozoa that higher metazoans cannot have evolved from seriated flatworms related to the recent Seriata (Proseriata and Tricladida). Even the seemingly primitive Acoela have such aberrant spermatozoa that evolution of higher metazoans from acoels related to the recent Acoela seems highly improbable.The ultrastructure of the spermatozoa of the parasitic groups of flatworms (Monogenea, Digenea, Cestoda) is very similar to that found in the Kalyptorhynchia, a further indication that the parasitic groups are related to the rhabdocoel turbellarians.     

Tooth function and replacement in early Mesozoic ornithischian dinosaurs: implications for aestivation

Thulborn (1978, Leihaia II ) suggests that ornithischian dinosaurs of the upper Stormberg Series (Late Triassic-Early Jurassic) of southern Africa underwent aestivation during an annual dry season. His argument, based on an interpretation of tooth function and replacement in heterodontosaurids, is: (1) unequivocal evidence of tooth replacement is not seen, and (2) piecemeal replacement of the dentition would be incompatible with maintenance of a fore-aft grinding function of the teeth; therefore, the entire dentition must have been rapidly replaced as a unit during periods of non-feeding, i.e. during aestivation. However, study of tooth wear patterns in Lanasaurus, Lycorhinus , and Heterodontosaurus show that jaw movements during mastication were orthal (open-and-close) and lateral to medial, not forwards and backwards. Differences in degree of tooth wear would not interfere with masticatory movements. Patterns of differential wear indicate that tooth replacement was not periodic but continuous, as in other reptiles. Zahnreihen , with a Z-spacing of about 3.0, are recognizable. Replacement ceased in mature individuals. The dentition shows adaptations for prolonging its effective life despite heavy wear. Differential tooth wear is incompatible with the idea of replacement of the entire dentition as a unit during an hypothesized period of aestivation. Thulborn's suggestion of aestivation in fabrosaurid ornithischians is also shown to be unlikely.     

广西凤山、西林等地中三叠统上部双壳类分带研究*

讨论广西西部中三叠统上部的双壳类生物地层序列,建立5个化石带;并附述黔南和滇东南晚三叠世1个双壳类带.这些带自下而上为:(1) Daonella (Longidaonella) producta-D. americana 带,属晚安尼早中期;(2) D. moussoni 高峰带,属晚安尼晚期;(3) D. rieberi-D. indica 带,属早拉丁期;(4) D. kotoi-D. jilongensis 带,属晚拉丁早期;(5) Halobia subcomata-D. varifurcata带,属晚拉丁晚期;(6) H. rugosoides-H. bifurcata 带,属早卡尼期.文内简要描述了各带的主要标志化石23种.     

Hydrological Response of Populus euphratica Olve. Radial Growth in Ejinaa Banner, Inner Mongolia

Populus euphratlca Olve. is a dominant tree species in Ejlnaa Oasis of the lower reaches of the Helhe River, inner Mongolia, China. In recent years, the population of this species has shown signs of degradation that are suggested to be probably associated with the decrease of surface water. In this study, the history of river runoff In this region was examined with a dendrochronological study of P. euphratica from four sites. It Is found that tree-ring widths In the all sites have negative correlation with runoffs of all months at the Zhengylxla hydrological station. Principal component （PC） analysis of the tree-ring chronologies shows that the first PC （PC1） accounts for 49.98% of the total variances. The first PC Is found to have a significantly negative correlation with runoffs In March and April （- 0.52 and - 0.43, respectively, P 〈 0.05）. This negative correlation might be related to variations In the depth of underground water.