Form of the trilobite digestive system: alimentary structures in Pterocephalia

1994 ◽  
Vol 68 (2) ◽  
pp. 294-305 ◽  
Author(s):  
Brian D. E. Chatterton ◽  
Zerina Johanson ◽  
George Sutherland
Keyword(s):  
British Columbia ◽  
Digestive System ◽  
Alimentary Tract ◽  
Feeding Habits ◽  
Complex Mixture ◽  
Energy Dispersive ◽  
Sister Taxon ◽  
Energy Dispersive Analysis ◽  
Upper Cambrian ◽  
Order Of Magnitude

Three types of alimentary canals (=midgut) occur in the Annelida and non-trilobite Arthropoda: 1) a sagittal tube with metamerically paired diverticula related to the number of somites; 2) a tube that is constricted slightly between somites; and 3) a simple tubular gut that may taper slightly backwards to the anus. At least two of these three types (1 and 3) occur in the Trilobita. Pterocephalia and Olenoides share the first type with the probable sister taxon to the Trilobita, Naraoia (Nectaspida), and this is probably the plesiomorphic condition for the class. Varying feeding habits may well have made this character homoplastic within each of these groups. The preservation of parts of the alimentary tract in specimens of Upper Cambrian Pterocephalia n. sp. (McKay Group, British Columbia) was probably a function of taphonomic and/or very early diagenetic changes that resulted from the type of food preferred by that trilobite. Other trilobites from the same beds do not have their soft parts preserved. The alimentary structures are preserved in a different fashion from, apparently unattached to, and an order of magnitude larger than genal caeca that occur in this taxon. Thus, genal caeca are regarded as imprints of circulatory rather than alimentary structures.Energy dispersive analysis of a fragment of preserved alimentary tract of Pterocephalia n. sp. showed the presence of Ca, Si, Al, Fe, P, K, Na, and Cl. These alimentary tracts are composed of a complex mixture of minerals that probably includes clays, detrital quartz, carbonates, phosphates, and oxides or hydroxides. The structure of these dark fillings is microcrystalline. The presence of detrital minerals as part of this mixture would suggest that this trilobite was a deposit feeder.

Electron-Probe Quantitative Energy-Dispersive Analysis of Trace Magnesium Concentrations in Ag-Mg Alloys

1996 ◽  
Vol 54 ◽  
pp. 510-511
Author(s):  
R. B. Marinenko
Keyword(s):  
Electron Probe ◽  
Energy Dispersive Spectrometry ◽  
Mg Alloys ◽  
Energy Dispersive ◽  
Energy Dispersive Analysis ◽  
High Tc ◽  
Alloy Wire ◽  
High Tc Superconductor ◽  
Eds Analysis ◽  
Superior Mechanical Properties

Internally oxidized Ag-Mg alloys are used as sheaths for high Tc superconductor wires because of their superior mechanical properties. The preparation and characteristics of these materials have been reported. Performance of the sheaths depends on the concentration of the magnesium which generally is less than 0.5 wt. percent. The purpose of this work was to determine whether electron probe microanalysis using energy dispersive spectrometry (EDS) could be used to quantitate three different Ag-Mg alloys. Quantitative EDS analysis can be difficult because the AgL escape peak occurs at the same energy (1.25 keV) as the Mg Kα peak. An EDS spectrum of a Ag-Mg alloy wire is compared to a pure Ag spectrum in Fig. 1.

scholarly journals Morphohistology of the Digestive Tract of the Damsel FishStegastes fuscus(Osteichthyes: Pomacentridae)

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Bhaskara Canan ◽  
Wallace Silva do Nascimento ◽  
Naisandra Bezerra da Silva ◽  
Sathyabama Chellappa
Keyword(s):  
Digestive Tract ◽  
Transition Region ◽  
Digestive System ◽  
Feeding Habits ◽  
Northeastern Brazil ◽  
Muscular Layer ◽  
Pyloric Caeca ◽  
Anterior Intestine ◽  
The Mean ◽  
Tidal Pools

This study investigated the morphohistology of the digestive tract and the mean intestinal coefficient of the damsel fishStegastes fuscuscaptured from the tidal pools of Northeastern Brazil. The wall of the digestive tract ofS. fuscusis composed of the tunica mucosa, tunica muscularis, and tunica serosa. The esophagus is short with sphincter and thick distensible wall with longitudinally folded mucosa. Mucous glands are predominant, and the muscular layer of the esophagus presented striated fibers all along its extension. The transition region close to the stomach shows plain and striated muscular fibers. Between the stomach and intestine, there are three pyloric caeca. The intestine is long and thin with four folds around the stomach. The anterior intestine presents folds similar to those of pyloric caeca. The estimated mean intestinal coefficient and characteristics of the digestive system ofS. fuscuspresent morphological adequacy for both herbivorous and omnivorous feeding habits.

scholarly journals Magnitude and frequency of landslides triggered by a storm event, Loughborough Inlet, British Columbia

2004 ◽  
Vol 4 (3) ◽  
pp. 475-483 ◽  
Author(s):  
R. H. Guthrie ◽  
S. G. Evans
Keyword(s):  
British Columbia ◽  
Power Law ◽  
Storm Event ◽  
Data Sets ◽  
Landslide Occurrence ◽  
Physical Conditions ◽  
Pareto Model ◽  
Order Of Magnitude ◽  
Storm Cells ◽  
Coastal British Columbia

Abstract. One hundred and one landslides were documented across 370km2 following a rainstorm that swept the British Columbia coastline on 18 November 2001. Despite the regional nature of the storm, the landslides were spaced close together, even within the study area. Landslide clustering is attributed to high intensity storm cells too small to be recorded by the general hydrometric network. The evidence nicely corroborates previous historical studies that reached similar conclusions, but against which there was no modern analog analyzed for coastal British Columbia. Magnitude-cumulative frequency data plotted well on a power law curve for landslides greater than 10000m2, however, below that size several curves would fit. The rollover effect, a point where the data is no longer represented by the power law, therefore occurs at about 1.5 orders of magnitude higher than the smallest landslide. Additional work on Vancouver Island has provided evidence for rollovers at similar values. We propose that the rollover is a manifestation of the physical conditions of landslide occurrence and process uniformity. The data was fit to a double Pareto distribution and P-P plots were generated for several data sets to examine the fit of that model. The double Pareto model describes the bulk of the data well, however, less well at the tails. For small landslides (<650m2) this may still be a product of censoring. Landscape denudation from the storm was averaged over the study area and equal to 2mm of erosion. This is more than an order of magnitude larger than the annual rate of denudation reported by other authors for coastal British Columbia, but substantially less than New Zealand. The number is somewhat affected by the rather arbitrary choice of a study area boundary.

X.—On the Feeding Mechanism of a Mysid Crustacean, Hemimysis Lamornæ

1927 ◽  
Vol 55 (1) ◽  
pp. 219-253 ◽  
Author(s):  
H. Graham Cannon ◽  
S. M. Manton
Keyword(s):  
Digestive System ◽  
Feeding Habits ◽  
Great Length ◽  
Gastric Mill ◽  
General Biology ◽  
Feeding Mechanism ◽  
In Captivity ◽  
Fish Tanks

The general biology of the Mysids has recently been studied at great length by Blegvad (1922) at Copenhagen. His paper, containing a very complete literature list, deals with Mysis inermis, Rathke, Mysis flexuosa, Müller, and Mysis neglecta, Sars. His comments on feeding are limited, and refer chiefly to the nature of the food that the animals ate in captivity. Gelderd's work (1909) on the digestive system of the Schizopoda describes the course taken by the food through the gastric mill, the masticatory functions of this apparatus, and the method by which the masticated food and digestive juices are brought together, but does not deal with the manner in which the food reaches the stomach. An account, then, of the method by which a mysid collects its food would fill a gap in our knowledge of these forms. The only description, as far as we are aware, of the feeding habits of a mysid is that of Depdolla (1923), who worked on Praunus [Mysis] flexuosus, but his account is superficial and in our opinion very inaccurate. The following paper deals with the feeding habits of a small mysid, Hemimysis lamornœ, about 8 mm. long, which has established itself in the larger fish-tanks at the M.B.A. laboratory at Plymouth. It breeds freely all the year round, and can be obtained from the tanks in abundance, although it is stated to be only a rare visitor in the Plymouth district.

IX.—The Structure and Function of the Alimentary Canal of Æolid Molluscs, with a Discussion on their Nematocysts

1938 ◽  
Vol 59 (2) ◽  
pp. 267-307 ◽  
Author(s):  
Alastair Graham
Keyword(s):  
Alimentary Canal ◽  
Digestive System ◽  
Feeding Habits ◽  
Structure And Function ◽  
Gastropod Mollusc ◽  
Food And Feeding ◽  
The Moment ◽  
Almost All ◽  
And Function ◽  
Great Advance

During recent years there has been a very great advance in our knowledge of the minute structure and function of the various regions and glands of the alimentary canal of the prosobranch and pulmonate gastropods, without any corresponding increase in our understanding of the opisthobranch and, in particular, of the nudibranch gut. That the emphasis should be laid on the streptoneurous and the land-living forms is obviously due to their abundance and to the fact that they include almost all the familiar types of gastropod mollusc, but it is disappointing that, at the moment of writing, there exists only one account of the histology and function of the digestive system of either a dorid or an æolid—to confine attention to the two main types of nudibranch molluscs which occur in British waters—that of Millott (1937b). This is perhaps more noticeable when it is recalled that the nudibranchs have specialised along distinctly unusual lines, many of which are intimately associated with the food and feeding habits which the animals have adopted. The æolids, it is true, have attracted a lively interest in connexion with their possession of nematocysts, but the majority of investigators have apparently been content to trace these into the cnidosacs without concerning themselves over the other constituents of the animal's food.

scholarly journals Trace metal concentration in wild avian species from Campania, Italy

2011 ◽  
Vol 9 (1) ◽  
pp. 86-93 ◽  
Author(s):  
Annalisa Zaccaroni ◽  
Camilla Niccoli ◽  
Giulia Andreani ◽  
Dino Scaravelli ◽  
Maria Ferrante ◽  
...  
Keyword(s):  
Metal Accumulation ◽  
Southern Italy ◽  
Feeding Habits ◽  
Trace Metal Concentration ◽  
Insectivorous Birds ◽  
Prey Fish ◽  
Cd Accumulation ◽  
Metal Levels ◽  
Order Of Magnitude ◽  
Trace Element Levels

AbstractThis study was conducted to determine heavy metals concentrations in tissues of 94 birds belonging to different species from coastal areas of Naples and Salerno (Southern Italy) in order to provide baseline data concerning trace element levels in wild birds living in or close to an area characterized by high anthropogenic impact. Additional aim of this study was to verify if diet influenced metal accumulation, so birds were classified as birds of prey, fish eating birds and insectivorous birds. Kidney was the primary organ for Cd accumulation in all groups considered, Pb was accumulated preferentially in bone, whereas Hg showed high values in liver of fish eating birds. Zn showed the highest mean concentrations, while Cu levels were one order of magnitude less. The variance analysis with respect to feeding habits disclosed only a lower accumulation of Hg in insectivores with respect to the other groups. For all metals, the concentrations measured in tissues should be considered indicative of chronic exposure to low, “background” environmental levels and/or to the presence of low bioavailable metals in the environment. In addition, metal levels were not of toxicological concern, being always well below the toxic thresholds defined for each metal.

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