Feeding behavior of the cirratulid Cirriformia filigera (Delle Chiaje, 1825) (Annelida: Polychaeta).

Observations of the feeding behavior of Cirriformia filigera (Delle Chiaje, 1825) (Annelida: Polychaeta) from the intertidal zone of S?o Francisco and Engenho D'água beaches (S?o Sebasti?o, State of S?o Paulo) were made in the laboratory. This species, like other cirratulids, is a deposit feeder, feeding mainly on sediment surface with the aid of its grooved and ciliated palps, which are used to capture food particles. The worm lies just beneath the substrate surface in a J-shaped tube. When feeding, it extends up to 4 palps over the sediment surface, capturing food particles which pass down the groove of each palp directly to the mouth. Only fine sand grains are ingested. The worm frequently extends 4 branchial filaments into the overlying water for aeration. When it moves with the prostomium sideways, it collects and transports sand grains that pass backwards along its ventral region until reaching the middle part of its body. Next, the parapodia and palps move the sand grains to the dorsal posterior end of the animal, covering this area with sand. Some sand grains are also ingested as the worm moves.     

Sucrose Release into the Endosperm Cavity of Wheat Grains Apparently Occurs by Facilitated Diffusion across the Nucellar Cell Membranes

Nutrients required for the growth of the embryo and endosperm of developing wheat (Triticum aestivum L.) grains are released into the endosperm cavity from the maternal tissues across the nucellar cell plasma membranes. We followed the uptake and efflux of sugars into and out of the nucellus by slicing grains longitudinally through the endosperm cavity to expose the nucellar surface to experimental solutions. Sucrose uptake and efflux are passive processes. Neither was sensitive to metabolic inhibitors, pH, or potassium concentration. p-Chloromercuribenzene sulfonate, however, strongly inhibited both uptake and efflux, although not equally. Except for p-chloromercuribenzene sensitivity, these characteristics of efflux and the insensitivity of Suc movement to turgor pressure are similar to those of sucrose release from maize pedicels, but they contrast with legume seed coats. Although the evidence is incomplete, movement appears to be carrier mediated rather than channel mediated. In vitro rates of sucrose efflux were similar to or somewhat less than in vivo rates, suggesting that transport across the nucellar cell membranes could be a factor in the control of assimilate import into the grain.     

Ooids from Turkey and Egypt in the Eastern Mediterranean and a love-story of Antony and Cleopatra

Summary Cleopatra’s beach is one of the most famous in Turkey for its distinctive white sand, composed largely of ooids. Legend has it that the Roman leader, Mark Antony, had this sand shipped from Alexandria in Egypt to create a beach for his lower Cleopatra, on Sedir Island in G?kova Bay, SE Aegean Sea. This study examines the reality of this leagend from a comparison of the oolitic sand from Cleopatra’s beach in Turkey with oolitic sand from the coast west of Alexandria in Egypt, the home city of Cleopatra, and only place in the Mediterranea where Holocene ooids occur in abundance. The ooids on Cleopatra’s beach gave a pale browncreamy colour and dull surface texture. Most grains are spherical, with nuclei of terrigenous grains, peloids and bioclasts. The Cleopatra ooids have all the features typical of high-energy, shallow-marine ‘classic” ooids, but they occur in a very low energy bay and shown evidence of being out place there (microborings, discolouration, dull surface). In terms of size, shape, cortex fabric and mineralogy, the Cleopatra ooids show great similarities to those from the northern coast of Egypt, west of Alexandria. The Alexandria ooids examined have a white-cream colour with a high polish, although there are fewer silicate nuclei compared to the Cleopatra ooids. On the basis of textures and microfabrics, the hydrographic conditions at G?kova bay, the relatively small quantity of oolitic sand in this tiny pocket beach and the absence of this type of sand any-where else in Turkey, it is concluded that the oolitic sand was brought to Cleopatra’s beach from somewhere else, and that the northern Egyptian coast was the most likely source. This lends credence to the Antony and Cleopatra story. Calculations suggest that some 15 Roman corn barges would have been required to transport the quantity of sand now present on the beach in Turkey.     

Structure and Dynamics of Anaerobic Bacterial Aggregates in a Gas-Lift Reactor

Anaerobic mixed-culture aggregates, which converted glucose to acetic, propionic, butyric, and valeric acids, were formed under controlled conditions of substrate feed (carbon limitation) and hydraulic regimen. The continuous-flow system used (anaerobic gas-lift reactor) was designed to retain bacterial aggregates in a well-mixed reactor. Carrier availability (i.e., liquid-suspended sand grains) proved necessary for bacterial aggregate formation from individual cells during reactor start-up. Electron microscopic examination revealed that incipient colonization of sand grains by bacteria from the bulk liquid occurred in surface irregularities, conceivably reflecting local quiescence. Subsequent confluent biofilm formation on sand grains proved to be unstable, however. Substrate depletion in the bulk liquid is assumed to weaken deeper parts of the biofilm due to cellular lysis, after which production of gas bubbles and liquid shearing forces cause sloughing. The resulting fragments, although sand free, were nevertheless large enough to be retained in the reactor and gradually grew larger through bacterial growth and by clumping together with other fragments. In the final steady state, high cell densities were maintained in the form of aggregates, while sand had virtually disappeared due to sampling losses and wash-out. Numerical cell densities within aggregates ranged from 10¹²/ml at the periphery to very low values in the center. The cells were enmeshed in a polymer matrix containing polysaccharides; nevertheless, carbon sufficiency was not a prerequisite to sustain high hold-up ratios.     

Fine structure of Pyramimonas octopus sp. nov., an octoflagellated benthic species of Pyramimonas (Prasinophyceae), with some observations on its ecology

A new octoflagellated species of Pyramimonas is described from three localities in Denmark. It is characterized by its ecology, being a marine psammophilic species associated with sand grains, and by details of the scaly covering on the cell surface. In the scale cover there are similarities to P. amylifera and to P. tetrarhynchus. P. octopus is distinguished by the possession of circular body scales of a type not previously found in the genus.
The general fine structure of the new species is described with emphasis on scale structure, the internal structure of the cell body and the flagella.     

A new encrusting interstitial marine fauna from Brazil

Abstract. This paper reports the second occurrence of a sand‐grain encrusting interstitial epifauna dominated by bryozoans and polychaetes at a site thousands of kilometers from the first described occurrence of such a fauna 20 years ago. Such faunas seem to have gone almost unrecorded in the marine ecological literature, but they are potentially geographically widespread and ecologically significant, deserving recognition and further study by benthic ecologists. Although rooted‐erect and free‐living lunulitiform bryozoans can be abundant in soft‐bottom habitats, the presence of encrusting forms was, until recently, considered to be limited to patches of hard substrata. In 1985 and 1988, a new and seemingly unique habitat for encrusting bryozoans and other organisms on single grains of shell or sand was reported from the coastal waters of Florida, USA. Here we report a second discovery of an interstitial encrusting fauna from the continental shelf off the state of São Paulo, Brazil. In addition to the cupuladriid Discoporella umbellata, several species of bryozoans (9 cheilostomes, 3 ctenostomes, and 1 cyclostome) were found encrusting on or boring into sand grains from the 4 stations examined. Four species were found exclusively on sand to gravel size grains. The most abundant colonies, with ～1300–1500 colonies m^?2, belonged to a new species of Cleidochasma. New species of Trypostega and Reginella, each with up to 200–300 colonies m^?2, were also discovered. The grain‐encrusting bryozoans were characterized by their small size, and by the fact that sexual reproduction was initiated very early in colony growth; brood chambers (for the development of embryos into larvae) occurred in colonies having only a few zooids. Colonies of boring ctenostome and cheilostome bryozoans were even more abundant than those of grain encrusting forms, being present in almost every piece of shell (～5000–5500 colonies m^?2). The fauna also included representatives of other groups of encrusting organisms, especially tubeworms (11,000–13,000 tubes m^?2). Planned work on samples from additional stations on the São Paulo shelf will no doubt yield a larger number of species from various taxa and perhaps show some overlap in sand fauna species between the Brazilian and Floridian sites. In addition to the unique species of single grain encrusters, colonies of bryozoan species characteristic of larger subtidal hard substrata were also found on sand or gravel size grains, indicating that an interstitial refuge may be available to some epifaunal taxa and suggesting that this interstitial refuge, which remains almost completely unknown to benthic ecologists, may play a large role in determining distributions of those taxa.     

Red white and blue – bright light effects in a diurnal rodent model for seasonal affective disorder

Despite the common use of bright light exposure for treatment of seasonal affective disorder (SAD), the underlying biology of the therapeutic effect is not clear. Moreover, there is a debate regarding the most efficacious wavelength of light for treatment. Whereas according to the traditional approach full-spectrum light is used, recent studies suggest that the critical wavelengths are within the range of blue light (460 and 484 nm). Our previous work shows that when diurnal rodents are maintained under short photoperiod they develop depression- and anxiety-like behavioral phenotype that is ameliorated by treatment with wide-spectrum bright light exposure (2500 lux at the cage, 5000 K). Our current study compares the effect of bright wide-spectrum (3,000 lux, wavelength 420- 780 nm, 5487 K), blue (1,300 lux, wavelength 420-530 nm) and red light (1,300 lux, wavelength range 600-780 nm) exposure in the fat sand rat (Psammomys Obesus) model of SAD. We report results of experiments with six groups of sand rats that were kept under various photoperiods and light treatments, and subjected to behavioral tests related to emotions: forced swim test, elevated plus maze and social interactions. Exposure to either intense wide-spectrum white light or to blue light equally ameliorated depression-like behavior whereas red light had no effect. Bright wide-spectrum white light treatment had no effect on animals maintained under neutral photoperiod, meaning that light exposure was only effective in the pathological-like state. The resemblance between the effects of bright white light and blue light suggests that intrinsically photosensitive retinal ganglion cells (ipRGCs) are involved in the underlying biology of SAD and light therapy.     

Behaviour and local distribution of the freshwater oligochaete Nais pardalis Piguet (Fam. Naididae)

1. Nais pardalis Piguet, a small freshwater oligochaete, lives in the surface few cm of sandy sediments in Loch Leven, County of Kinross, Scotland. 2. It forms branching passageways or tubes in the sediment not by any active constructional behaviour, but by the secretion of a material which sticks the sand grains together. 3. The sand grains making up the tubes are exactly the same size as those in the surrounding sediment. 4. Animals select the smallest grains in their environment for ingestion. 5 In the laboratory, rates of ingestion of sand grains measured on different animals vary from 5 to 60 grains/hour and rates of excretion from 3 to 6/hour, but these figures should be viewed with caution. 6. Analysis of the rate of ingestion of sand grains indicates that grains are not ingested randomly in time. Having eaten one grain, an animal is less likely to eat another within the next 10 seconds.     

Optical dating of dune sand from Blombos Cave,South Africa: II--single grain data

A sequence of optically stimulated luminescence measurements was made on each of 8,961 grains from three sand samples from Blombos on the southern Cape coast. One sand unit overlay Middle Stone Age deposits in Blombos Cave. The measurement sequence, the single aliquot regenerative dose protocol, was used to obtain values for the total effective radiation dose to which each grain had been exposed since burial. A series of checks was carried out on each grain to ensure that the luminescence signals were reproducible, and that they were derived from quartz. This led to acceptance of less than 5% of the grains. An estimate of the radiation dose for the sand unit was obtained by combining the values using the central age model. In order to use a larger number of grains that might be representative of the sand unit, the radiation dose was also estimated by using the signal from the above grains, combined with the signals from those grains that had lower signals, but nonetheless contributed to the total light sum; this utilised between 9 and 18% of the grains. This enables us to obtain estimates of the ages as 67.3+/-3.8 ka, 65.6+/-2.8 ka and 68.8+/-3.0 ka for the three samples. These values agree with ages obtained using the single aliquot regenerative dose protocol for aliquots composed of several hundred grains.     

The development of the retinomotor reactions in larval plaice (Pleuronectes platessa, L.) and turbot (Scophthalmus maximus, L.)

The development of the retinomotor reaction was examined histologically in the larvae of plaice (Pleuronectes platessa, L.) and turbot (Scophthalmus maximus, L.). In plaice retinal pigment migration is present from hatching, but, in turbot, does not occur until just before metamorphosis. In both species rods first develop at metamorphosis. Plaice show cone migration, but this does not occur in turbot. During dark-adaptation retinal pigment contraction started at ≈ 100 lux in all stages of plaice. Before metamorphosis pigment was fully contractedimmediately below 1000 lux, but after metamorphosis full contraction did not occur until the light intensity had fallen to < 1.0 lux. The thresholds for cone migration in plaice showed similar changes, although the actual light intensities were about an order of magnitude lower. In turbot there was always an abrupt transition between light- and dark-adaptation; the thresholds for this fell from ≈ 10 lux at the start of metamorphosis to between 1.0 and 10 lux at the end. The lower threshold light intensities in turbot compared to plaice may indicate that vision is of greater importance in the feeding of the former species.     

Activity patterns of insectivorous bats and birds in northern Scandinavia (69° N), during continuous midsummer daylight

Previous studies suggest that many species of insectivorous bats are nocturnal, despite the relatively low availability of their insect prey at night, because of the risk of predation by diurnal predatory birds. We hypothesised that if this was the case bats living above the arctic circle would alter their feeding behaviour during midsummer because there would no longer be any benefit to restricting their activity to the period when their prey are least abundant. Alternatively, if bats were more influenced by competition from aerial insectivorous birds they would continue to feed at 'night' to avoid such competition. In northern Norway (69°  N), during continuous midsummer daylight, insectivorous sand martins ( Riparia riparia ) concentrated their aerial feeding activity when aerial insects were most abundant. The birds stopped feeding between 23:00 and 07:00 when aerial insects were least abundant. In contrast, northern bats ( Eptesicus nilssonii ), fed mostly between 22:00 and 02:00, coinciding with the lowest aerial insect availability, and with the period when light levels were lowest (ca 1000 lux). Bat activity patterns were closest to those predicted by the avian competition hypothesis. The low densities of both sand martins and Northern bats in the study area, however, were less consistent with this hypothesis. Possibly populations of both species were higher historically and the observed patterns reflected historical competition. Bat activity was most closely correlated to ambient light levels. This raised two alternative explanations that we could not eliminate. Perhaps there was differential predation risk, between the brightest and darkest parts of the day, because the visual capacities of falcons are strongly dependent on luminance. Alternatively the bats may have been entrained to emerge at given light levels by their behaviour at other times of year.     

Parasitism and the burrowing depth of the beach hopper Talorchestia quoyana (Amphipoda: Talitridae)

Talitrid amphipods spend their days burrowed in sand to avoid predators as well as desiccation and heat stress, although other factors may influence burrowing depth. We investigated the potential role of mermithid nematode parasites in determining burrowing depth in the amphipod Talorchestia quoyana. Mermithids grow as parasites inside amphipods until they reach adulthood, when they must emerge from their host into moist sand to complete their life cycle and reproduce. When allowed to burrow to a depth of their choice in experimental situations, large amphipods burrowed deeper than small ones. In addition, deep-burrowing amphipods were more likely to be infected by mermithid nematodes, and harboured longer worms, on average, than amphipods that burrowed close to the sand surface. This last result is not an artefact of the larger size of deep-burrowing amphipods: the increase in worm length with increasing depth was found after statistical correction for host size. In other words, amphipods that burrowed deeper harboured longer worms than expected based on their body size, whereas those that stayed near the surface of the sand column harboured worms shorter than one would expect based on host size. This implies that the greater burrowing depth of infected amphipods is a consequence, and not a cause, of infection. These results emphasize the importance of parasitism as a determinant of the small-scale spatial distribution of their hosts.     

EFFECTS OF CHIRONOMID (INSECTA: DIPTERA) TUBE-BUILDING ACTIVITIES ON STREAM DIATOM COMMUNITIES1,2

Chironomid retreats, constructed out of sand grains upon submerged wood debris, increase the surface area available for diatom colonization. The three dimensional substratum afforded by chironomid tubes supports up to twelve times the diatom biavolume found upon adjacent, unmodified substratum in a northern Michigan stream. Diatom enumeration within scrapings from small defined areas on artificial substrata, combined with examination of intact natural substrata through scanning electron microscopy (SEM), reveals distinct, microdistribution patterns. The larval retreats of two major taxa of tube-dwelling chironomid's (Micropsectra sp. and Pseudodiamesa cf. pertinax Garrett) display significantly different diatom communities relative to adjacent masonite substratum. Substratum without chironomid tubes is primarily colonized by Achnanthes minutissima Kütz. and Cocconeis placentula Ehr., exhibiting the lowest species diversity of microhabitats examined. The diatom flora upon sand tubes of Micropsectra sp. is dominated by Opephora martyi Herib., as is the flora of sand grains collected from the stream sediment load. These two micro-habitats exhibit a high community similarity (SIMI). The SIMI index also suggests that the flora of P. pertinax tubes is highly similar to that of sand grains. Diversity, however, is almost three times greater on P. pertinax tubes and SEM observations reveal that this microhabitat is characterized by a more spatially complex flora; Nitzschia and Navicula spp. dominate the upperstory, and O. martyi is located on underlying sand grains. Results indicate that tube-building chironomids in Carp Creek affect diatom microdistribution by: (1) stabilizing sand grains and associated flora within their retreats, (2) providing a ‘refugium’ for upperstory diatom taxa from the mayfly grazer, Baetis vagans McDunnough (Insecta: Ephemeroptera), and (3) through local nutrient enrichment.     

A model that uses the induction phase of lux gene-dependent bioluminescence in Pseudomonas fluorescens HK44 to quantify cell density in translucent porous media.

A cooled charge-coupled device (CCD) camera was used to follow the kinetics of induction of lux gene-dependent bioluminescence in Pseudomonas fluorescens HK44 held either in aqueous suspensions minus sand, saturated or unsaturated translucent sand (0.348 and 0.07 cm(3) H(2)O/cm(3) of sand, respectively), and at cell densities ranging between 1 x 10(6) and 8.5 x 10(8) cells/ml. Before O(2) availability became a limiting factor, the rate of light emission (L) increased with the square of time (t) and linearly with increasing cell density (c). A nonlinear model was developed that contains a "rate of increase in light emission" constant, B', which is determined directly from the slope of a plot of radical L/c against t. The model predicted the behavior of lux induction in HK44 under a variety of conditions. Similar B' values were determined [49.0-57.6 x 10(-10) light units/(cell min(2))] for cell suspensions held in aqueous medium minus sand, in saturated or unsaturated 40/50 grade sand (0.36 mm grain diameter) and in two other textural classes of translucent sand. Although both the growth phase, and the presence of glucose during lux induction affected the first detectable time (FDT) of bioluminescence by HK44 in sand, the kinetics of induction of light emission were similar among treatments (stationary phase cells plus glucose, B'=61.6+/-3.2, log phase cells plus glucose, B'=63.2+/-7.2). The potential exists to use a combination of a CCD camera system, an inducible lux gene containing bioluminescent bacterium, and a light transmission chamber to nonintrusively visualize and quantify in real time the interactions between bacterial growth and unsaturated flow of water and solutes in porous media.     

Fine Structure of a Silica-Biomineralizing Testate Amoeba,Netzelia tuberculata1

The fine structure of the cytoplasm and the intracytoplasmic origin of siliceous granules and surrounding cement plaques used in constructing the shell wall of Netzelia tuberculata are described. These organisms construct their test from biogenic siliceous particles and sand grains or other foreign particles (including starch grains apparently from algal prey) coated with biogenic silica. The smooth surface texture of the grains, compared to those of other particle-gathering testate amoebae, can be expalained by the deposition of a thin surface layer of silica on the foreign particles incorporated into the wall.     

Shell structure in Difflugia Lobostoma observed by scanning and transmission electron microscopy

Observations by scanning and transmission electron microscopy provide information about shells of Difflugia lobostoma which suggests a complex activity in shell construction. As observed by scanning microscopy, the shell consists of a single layer of sand grains which are organized into rosettes. The sand grains of the rosettes are different in size from those of flat areas between rosettes suggesting that the organism sorts these stones and places them according to size. Hydrofluoric acid treatment dissolves the sand but leaves a web of cement material intact. Examination of such acid treated specimens by transmission microscopy shows structure in the cement material of the shell, and granules of similar structure in the cell body. The rosette pattern observed differs from shell patterns in other species of Difflugia, and this suggests that shell structure may be species specific.     

Phylogenetic analysis of the incidence of lux gene horizontal transfer in Vibrionaceae

Horizontal gene transfer (HGT) is thought to occur frequently in bacteria in nature and to play an important role in bacterial evolution, contributing to the formation of new species. To gain insight into the frequency of HGT in Vibrionaceae and its possible impact on speciation, we assessed the incidence of interspecies transfer of the lux genes (luxCDABEG), which encode proteins involved in luminescence, a distinctive phenotype. Three hundred three luminous strains, most of which were recently isolated from nature and which represent 11 Aliivibrio, Photobacterium, and Vibrio species, were screened for incongruence of phylogenies based on a representative housekeeping gene (gyrB or pyrH) and a representative lux gene (luxA). Strains exhibiting incongruence were then subjected to detailed phylogenetic analysis of horizontal transfer by using multiple housekeeping genes (gyrB, recA, and pyrH) and multiple lux genes (luxCDABEG). In nearly all cases, housekeeping gene and lux gene phylogenies were congruent, and there was no instance in which the lux genes of one luminous species had replaced the lux genes of another luminous species. Therefore, the lux genes are predominantly vertically inherited in Vibrionaceae. The few exceptions to this pattern of congruence were as follows: (i) the lux genes of the only known luminous strain of Vibrio vulnificus, VVL1 (ATCC 43382), were evolutionarily closely related to the lux genes of Vibrio harveyi; (ii) the lux genes of two luminous strains of Vibrio chagasii, 21N-12 and SB-52, were closely related to those of V. harveyi and Vibrio splendidus, respectively; (iii) the lux genes of a luminous strain of Photobacterium damselae, BT-6, were closely related to the lux genes of the lux-rib(2) operon of Photobacterium leiognathi; and (iv) a strain of the luminous bacterium Photobacterium mandapamensis was found to be merodiploid for the lux genes, and the second set of lux genes was closely related to the lux genes of the lux-rib(2) operon of P. leiognathi. In none of these cases of apparent HGT, however, did acquisition of the lux genes correlate with phylogenetic divergence of the recipient strain from other members of its species. The results indicate that horizontal transfer of the lux genes in nature is rare and that horizontal acquisition of the lux genes apparently has not contributed to speciation in recipient taxa.     

POLLEN ALLELOPATHY—A NEW PHENOMENON

SUMMARY
White dust spread on the leaves and stigmatic surface of Crotalaria pellida L. and Desmodium heteracarpon (L.) DC var. strigosum Meeuwen growing in the midst of a Parthenium hysterophorus L. stand was found to be clusters of Parthenium pollen. The fruit set in those species was poor. It was found that Parthenium pollen grains contained growth inhibitors which inhibited fruit set in many test species when artificially dusted on the stigmatic surface. In culture conditions the germination and pollen tube growth of the test species were inhibited in the presence of Parthenium pollen or their extract. The plant produces on an average 3375 million pollen grains per square metre areas of the stand. The pollen grains disperse in dusters of 600 to 800 each and are carried great distances by wind. Pollen grains deposited on leaves in large quantity also reduce the chlorophyll content in these species.     

Scanning electron microscopy of microorganisms on the roots of wheat

The scanning electron microscope was used to study the microorganisms on wheat roots grown in both soil and sand. Bacteria became common on the root surface only in the root hair region of young roots; nearer the tip of the root they were rare. Older roots had relatively high populations of bacteria. Bacteria were sometimes embedded in mucilage, of either plant or microbial origin, which seemed to bind the bacteria firmly to the root surface. Mineral grains on or near the roots of wheat were generally free of mucilage.     

Development of mass blooms of Thiocapsa roseopersicina on sheltered beaches on the Orkney Islands

Abstract Mass developments of the purple sulfur bacterium Thiocapsa roseopersicina in the surface layers of sandy beaches on the Orkney Islands were examined with respect to microcolony formation on sand grains, vertical distribution of viable cells and the ability to colonize beach surfaces. It was observed that microcolonies of the non-motile phototrophic bacterium cemented individual sand grains to each other and that the resulting aggregates could withstand severe wave action and may play a decisive role in the stabilization of these sandy beaches.
After removal of the top layer similar population densities of T. roseopersicina were recorded within seven days. It was calculated that the net specific growth rate initially was 0.53 day⁻¹ (0.022 h⁻¹).
Laboratory studies strongly suggest that the populations of T. roseopersicina on sheltered beaches on the Orkney Islands were growing phototrophically in the light even when the microenvironment was oxic. Bacteriochlorophyll a synthesis was repressed by oxygen and occurred during periods with low light intensities when the microenvironment was anoxic and contained sulfide.