The Importance of Water Vapour for the Circulating Air Flow through Nelumbo nucifera

Aquatic vascular plants depend on an adequate oxygen supplyin order to maintain growth and reproduction in anaerobic environments.Nelumbo nucifera is able to survive with a gas transport systemwhich supplies oxygen to the roots and rhizomes submerged inthe anaerobic sediment. It was possible to demonstrate thatthis gas transport system is based on a purely physical phenomenonThermo-osmotic oxygen transport was first demonstrated on freshleaves with the help of an oxygen-sensitive electrode. A definiteenhancement of oxygen flow was obtained through excised leaveswhen a temperature difference between the ambient and lacunarair was present in light. These leaves were then dried to brittlenessand the enhanced oxygen flow was still detectable. This showsthat not only photosynthetic oxygen, but also atmospheric oxygencan be transported to the buried organs. The absolute flow ofoxygen through dry leaves was much lower than through freshleaves, but the thermo-osmotic transport of oxygen still functioned.Furthermore, the process of thermo-osmosis need not rely ona difference in humidity between the two sides of a porous partition,but may be linked causally to the temperature difference andthe pore size. Key words: Nelumbo nucifera, oxygen transport, thermo-osmosis of gases     

Reduced Polyteny of Ribosomal RNA Cistrons in Giant Chromosomes of <Emphasis Type="Italic">Drosophila hydei</Emphasis><Superscript>*</Superscript>

The polytenization of rRNA cistrons in Drosophila species is studied in an attempt to follow the course of under-representation of heterochromatic compared with euchromatic chromosome regions.     

Covariation of morphological characters in the Triassic ammonoid Czekanowskites rieberi

The Triassic ammonoid Czekanowskites rieberi displays a covariation of morphological charac ters, which is rather common in ammonoids. Its morphological spectrum ranges from laterally compressed, involute, weakly ribbed forms to depressed, semiinvolute, strongly ribbed forms. In order to study this covariation, fifteen axially cut specimens have been analyzed by means of image analysis, which allows us to obtain the ontogenetic record of radii, area and perimeter of the individual whorl cross-sections. A logarithmic model of growth has been applied. Our data indicate that, owing to the covariation, the radii from the origin to the venter and to the umbil ical seam of a given whorl section vary inversely in order to maintain the relative position of the center of gravity of the whorl cross-section both throughout the ontogeny of single specimens and within the population. This influences hydrostatic parameters, such as the position of the center of mass and the orientation and stability of the shell. Since the ontogenetic record of the angular length of the body chamber is not known, we have calculated those hydrostatic varia bles using two mutually exclusive assumptions: (1) the angular length of the body chamber was constant throughout ontogeny and (2) the volume of the body chamber grew monotonically with the revolution angle. Fluctuations of the three hydrostatic variables were always less important in the first assumption. In any case, the spectrum of, for example, theoretical orien tations is comparable to those observed in the species of present-day Nautilus. The range of adult body-chamber length observed in C. rieberi is much narrower than the theoretical adult body-chamber length calculated under the second assumption which indicates that a certain control over this parameter existed in the natural population, probably in order to maintain a narrow range in orientation and stability. The excess or deficit in soft-body weight was probably compensated by inverse variations in shell-wall weight. The main conclusion is that, despite the extreme morphological variability, hydrostatic and, possibly, hydrodynamic properties of the population remained within narrow limits.     

Relationships Between Invertebrate Phyla Based on Functional-Mechanical Analysis of the Hydrostatic Skeleton

SYNOPSIS. The phylogeny of the major groups of deuterostomecoelomates—the chordates,hemichordates and echinoderms—isdiscussed based on a mechanical-functional analysis of the hydrostaticskeleton and associated structures. The basic approach is tofirst establish transformation series of individual featuresand of functional complexes of features and secondto determinetheir "Lesrichtung" by showing the direction of increased economy(i.e., better adaptation) with respect to environmental factors.It is argued that a metameric coelom is primitive with respectto an oligomeric one and that the ancestral form of the deuterostomecoelomates is a metameric, coelomate worm-like animal with acomplex set of circular, transverse andlongitudinal body muscles.The coelom plus the complex body musculature formed the hydrostaticskeleton.The sequence of structural modifications leading to chordatesis: (a) appearance of the notochord; (b) specialization of thedorsal longitudinal muscles with a reduction and disappearanceof the transverse and circular muscles; (c) simultaneous appearanceof the dorsal hollow nerve cord; (d) development of a postanaltail; and (e) appearance and specialization of the branchialbasket with gill slits as a filter feeding apparatus. The primitivechordate would be most similar to the lancelet (Acrania). Tunicatesare advanced chordates specialized forsessile life and lostmost chordate features in the adult, but retained them in thelarvae as adaptations for active dispersal. Enteropneusts (acornworms) are another advanced group specialized for burrowingin fine sediments and that evolved the anterior proboscis asa peristaltic burrowing organ. The notochord was lost as wasthe dorsal nerve cord and segmented conditionof the coelom.A collar originated as a means to prevent discharged water fromre-entering themouth. Pterobranchs arose from enteropneustlikeforms; their major structural changes are reduction of the branchialbasket and modification of the collar into tentacles which areassociated with life in a closed tube. Finally, echinodermsarose from a pterobranch-like ancestor by specializing for sessilelife and feeding with tentacles and by final loss of the branchialbasket. Groups such as the tunicates, hemichordates and echinodermscould be eliminated as ancestral forms within the deuterostomecoelomates because the evolution of acraniates and vertebratesfrom each of these groups would involve the appearance of gillslits before the notochord and/or the evolution of a metamericcoelom from an oligomeric one, both of which are exceedinglyimprobable. Central to the methods used to establish the transformationseries of features and their direction of evolutionary change(Lesrichtung) are functional (mechanical) analysis and adaptiveinterpretation of features; hence, functional-adaptive analysesare an integral and essential part of the methodology of phylogeneticinvestigation.     

Gnathostomulida from Fiji, Tonga and New Zealand

Of 54 species of Gnathostomulida known to date, only six have been reported from the Pacific Ocean. This paper describes 18 species of Gnathostomulida from the Pacific islands of Fiji. Tonga and northern New Zealand. Of these, three are species previously described from the northeastern Atlantic and Mediterranean: Haplognathia ruberrima (Sterrer 1966), or the northwestern Atlantic: Haplognathia rosacea (Sterrer 1970) and Pterognathia ctenifera (Sterrer 1970). Fifteen species are new to science, including three that represent two new genera: Cosmognathia arcus gen. et sp.n., Cosmognathia bastillae sp.n., Pterognathia crocodilus sp.n., Pterognathia vilii sp.n., Agnathiella sp., Tenuignathia vitiensis sp.n., Ratugnathia mukuluvae gen . et sp.n., Gnathostomula salotae sp.n., Gnathostomula raji sp.n., Gnathostomula maorica sp.n., Austrognathia singatokae sp.n., Austrognathia nannulifera sp.n., Austrognathia novaezelandiae sp.n., Austrognatharia homunculus sp.n., and Austrognatharia pecten sp.n.     

Subcellular compartmentation of elements in non-mycorrhizal and mycorrhizal roots of Pinus sylvestris: an X-ray microanalytical study. II. The distribution of calcium, potassium and sodium

The inter- and intracellular distribution of the elements calcium, potassium and sodium in non-mycorrhizal and mycorrhizal roots of Pinus sylvestris dependent on different external nutrient supply conditions was detected by energy-dispersive X-ray microanalysis after cryofixation, freeze-drying and pressure infiltration of the material. In non-mycorrhizal and mycorrhizal roots, calcium was mainly detectable in the apoplastic regions. The levels in vacuoles and cytoplasm were near the limits of detection by X-ray microanalysis. Incubation with high concentrations of potassium and sodium, or mycorrhizal infection with Suillus bovinus and Pisolithus tinctorius reduced the amounts of calcium detectable in the roots, especially in the apoplast of cortical cells. The studies revealed that: potassium is mainly localized in cytoplasm and cell walls; the cytoplasmic content is regulated over a wide range of external potassium concentrations; potassium levels in the inner parts of roots are higher than in the outer parts. Mycorrhizal infection with Suillus bovinus had no effect on the inter- and intracellular distribution of potassium in roots but, if the external supply was low, the potassium content in shoots was reduced. In non-mycorrhizal pine roots and those infected with Paxillus involutus an increase in the sodium content of all cell compartments was observed after treatment with high external concentrations of NaH₂PO₄. However, an increase in sodium content in mycorrhizas of S. bovinus was not detected. The X-ray microanalytical results are discussed in relation to the apoplastic movement of nutrients in non-mycorrhizal and mycorrhizal fine roots of pine and to the demand for these nutrients in different intracellular compartments.     

Palaeoctopus pelagicus from the Turonian of Mexico reinterpreted as a coelacanth (Sarcopterygian) gular plate

Abstract: The supposed vestige of a cephalopod gladius from Turonian platy limestones at Vallecillo, north‐east Mexico, named Palaeoctopus pelagicus by Fuchs et al. in 2008, is reinterpreted and shown to be a gular plate of a coelacanth fish, possibly of the genus Megacoelacanthus. In addition to the gular plate, two extrascapulars and fin rays of all fins are preserved on one slab and its counterpart. This is the first record of a coelacanth from these lower Turonian strata at Vallecillo, which are rich in fish.     

On the potential for ocean acidification to be a general cause of ancient reef crises

Anthropogenic rise in the carbon dioxide concentration in the atmosphere leads to global warming and acidification of the oceans. Ocean acidification (OA) is harmful to many organisms but especially to those that build massive skeletons of calcium carbonate, such as reef corals. Here, we test the recent suggestion that OA leads not only to declining calcification of reef corals and reduced growth rates of reefs but may also have been a trigger of ancient reef crises and mass extinctions in the sea. We analyse the fossil record of biogenic reefs and marine organisms to (1) assess the timing and intensity of ancient reef crises, (2) check which reef crises were concurrent with inferred pulses of carbon dioxide concentrations and (3) evaluate the correlation between reef crises and mass extinctions and their selectivity in terms of inferred physiological buffering. We conclude that four of five global metazoan reef crises in the last 500 Myr were probably at least partially governed by OA and rapid global warming. However, only two of the big five mass extinctions show geological evidence of OA.     

Bioenergy production potential of global biomass plantations under environmental and agricultural constraints

We estimate the global bioenergy potential from dedicated biomass plantations in the 21st century under a range of sustainability requirements to safeguard food production, biodiversity and terrestrial carbon storage. We use a process‐based model of the land biosphere to simulate rainfed and irrigated biomass yields driven by data from different climate models and combine these simulations with a scenario‐based assessment of future land availability for energy crops. The resulting spatial patterns of large‐scale lignocellulosic energy crop cultivation are then investigated with regard to their impacts on land and water resources. Calculated bioenergy potentials are in the lower range of previous assessments but the combination of all biomass sources may still provide between 130 and 270 EJ yr^?1 in 2050, equivalent to 15–25% of the World's future energy demand. Energy crops account for 20–60% of the total potential depending on land availability and share of irrigated area. However, a full exploitation of these potentials will further increase the pressure on natural ecosystems with a doubling of current land use change and irrigation water demand. Despite the consideration of sustainability constraints on future agricultural expansion the large‐scale cultivation of energy crops is a threat to many areas that have already been fragmented and degraded, are rich in biodiversity and provide habitat for many endangered and endemic species.     

Hesperotestudo (Testudines: Testudinidae) from the Pleistocene of Bermuda, with comments on the phylogenetic position of the genus

A recently discovered fossil land tortoise (Testudines: Testudinidae) is described from the Pleistocene of Bermuda. Its morphology is sufficiently well preserved to allow assignment to the extinct North American genus Hesperotestudo. However, several features of this tortoise are unique and it is named Hesperotestudo bermudae sp. nov. A review of the phylogenetic relationships of the better known genera of the Testudinidae suggests that the affinities of Hesperotestudo lie with other North American tortoises (Gopherus) and not with Geochelone or other testudinines; thus, Hesperotestudo is reassigned to the Xerobatinae. This is at least the fifth documentation of a testudinid dispersing over open ocean to an oceanic island (the first for Hesperotestudo) and it corroborates the hypothesis that members of this family are well suited to over-water dispersal.