bluuebunny/crossref_metadata_2025 huggingface dataset:
SPECTROGRAPHIC ANALYSIS OF PLANTS AND SOILS
Authors: MITCHELL R. L.
Published: January 2008

Spectrographic methods which are applicable to the analysis of plants and soils include those employing flame, arc and spark excitation. Some seventy elements can be determined spectrographically, the most important exceptions being gaseous and non‐metallic elements.

The most widely used flame emission method is that devised by Lundegårdh, in which the solution under examination is sprayed into an air‐acetylene flame. This method is particularly suited to the determination of the alkali and alkaline earth metals in soil and plant extracts. The Ramage method, in which the material is introduced on a paper spill, has also been used to some extent.

Arc methods are widely employed for the determination of both trace and major constituents, generally with solid material in carbon or graphite electrodes of a shape chosen to suit the object of the investigation. The most sensitive source for most elements is probably the cathode‐layer arc, although the high‐voltage a.c. arc is useful for certain elements in solution. Interrupted arc and spark sources have been less widely used but have advantages for certain purposes, such as the determination of boron.

Some direct photometric methods, omitting the use of a photographic plate, are described.

Spectrographic methods are applicable to qualitative, semi‐quantitative or quantitative determinations. Semi‐quantitative methods generally employ a visual or subjective assessment of the content of an element, and are useful in giving a general indication of the levels of most of the trace constituents present in any sample, with an accuracy of some 30%. When objective photometric measurements are used, figures reproducible to ± 3–10% may be expected, depending on the method employed and the element being determined.

Applications of spectrographic methods to analyses of soils and plants have been along both lines, either the semi‐quantitative survey of as many elements as possible, or the quantitative determination of specific elements. Attention is drawn to the relationship of the soil content to the geological origin of its parent material and to soil effects which may influence plant uptake.
L'ACÉTYLCHOLINE ET L'ADRÉNALINE CHEZ LES INVERTÉBRÉS
Authors: BACQ Par Z. M.
Published: January 2008

1o. Le tableau 2 résume ce que l'on sait sur la présence ďacétylcholine et de cholinestérase chez les Invertébrés, ainsi que sur la sensibilityé. des tissus àľacétylcholine et aux poisons qui paralysent ľaction de cette substance.

2o. La présence de nerfs cholinergiques est démontrée chez les Annélides (Armicolu, Aphrodite, Lumbricus, Hirudo), et les Siponculiens (Sipuncuh), chez les 1 Iolot huries, chez un seul mollusque (Venus mercenaria).

3o. Ľexistence de nerfs cholinergiques est inconcevable chez les Cœntérés.

4o. Chez les Arthropodes (Crustacés, Insectes et Arachnomorphes) tout porte à croire que les nerfs ne transmettent pas ľ'excitation par ľintermédiaire ľacétykholine.

5o. Chez leo Mollusques, àľexception de Venus mercenaria, tous, les essais de démonstration de nerfs cholinergiques ont échoué.

6o. Ľexistence de nerfs adrénergiques chez les Annélides est très probable, mais non encore certaine; de tels nerfs existent vraisemblablement chez les Céphalopodes et chez ľaplysie.

7o. Le cmur et les tissus des Invertébrés manifestent pour ľadrénaline et les amines syrnpathicomimétiques une sensibilityé non spécifique, le plus souvent faibie.
THE STRUCTURE OF THE STRIATED MUSCLE FIBRE
Authors: BARER ROBERT
Published: January 2008

1. The muscle fibre is regarded as a bundle of myofibrils, embedded in a viscous matrix, the sarcoplasm, the whole being surrounded by a delicate sheath, the sarcolemma.

2. The sarcolemma is a thin, apparently structureless membrane. Preliminary study with the electron microscope suggests that it may be less than o‐i /u. thick. No fibrils can be seen with the electron microscope, but a large number of small nodules lie scattered over the membrane. The sarcolemma is probably not collagenous in nature.

3. The sarcoplasm is a viscous, protein‐containing gel which surrounds the myofibrils. Mitochondria, glycogen and fat droplets are scattered throughout the sarcoplasm. Several enzymes have been isolated from what is believed to be the sarcoplasm. This suggests that the latter may be the site of important metabolic activity. The question of sarcoplasmic contractility is not yet settled. There is good evidence that it may occur in certain cells (myoblasts, striated fibres of tadpoles and insect larvae).

4. The evidence in favour of the existence of myofibrils as contractile units is discussed. The fact that individual myofibrils or groups of myofibrils can be made to contract independently, and sometimes asynchronously, is strong support for this view.

5. The electron microscope shows that the myofibrils consist of relatively straight protein chains. Several different striations (A, I, Z, M, N, H) can be recognized. There is no gross difference in orientation between the protein chains in the various bands, nor is there any evidence of a spiral structure.

6. Several aspects of Szent‐Gyorgyi's work are discussed. While this work has led to a better understanding of the muscle proteins, the theories of muscle structure arising from it have found no general acceptance.

7. Other theories attempting to account for the existence of the cross‐striations are reviewed. It is suggested that there is a periodic distribution of different chemical substances in the different bands. This may affect the physical, mechanical, and chemical properties of the myosin in those bands, and may account for the differences in birefringence between the A and I bands.

8. Evidence is presented against the existence of a Z ‘ membrane’ or other transverse membranes uniting the myofibrils. No structural connexion is believed to exist between the sarcolemma and the underlying sarcoplasm and myofibrils. The relationship may be a purely viscous or frictional one.

9. Reasons are suggested for the perfect alinement of the striations in neighbouring myofibrils. A full explanation may only be possible as a result of a better understanding of intermolecular and colloidal forces.
CAROTENOIDS AND REPRODUCTION
Authors: GOODWIN T. W.
Published: January 2008

.After a brief discussion of the essential chemical properties of carotenoids, the identification, occurrence and distribution of the pigments in the gonads and related organs of plants and animals have been reviewed. The information available concerning the metabolism of carotenoids in reproductive tissues and their possible function in reproduction has also been reviewed systematically.

In the higher plants, as maturation proceeds the carotenoid content of the tissues decreases, owing probably to the redirection of carotenoid synthesis into the reproductive organs. Further, the synthetic mechanism itself must be altered in some way because new carotenoids, never encountered in leaves, are produced in the reproductive organs. There is no evidence that carotenoids are involved in fertilization. In fact, many pollens contain no carotenoids.

Differential distribution of carotenoids in male and female gametes is encountered in some species of both algae and fungi, but whereas nothing is known about carotenoid metabolism and function in relation to reproduction in fungi, it is claimed that appropriate mixtures of stable and labile crocetin dimethyl esters stimulate both male and female gametogenesis in the alga Chlamydomonas.

In aquatic animals carotenoids are actively mobilized into the gonads during sexual reproductive activity, and in some cases are rendered water‐soluble by attachment to proteins. Carotenoids do not appear to be necessary for normal embryonic development, but one report indicates their possible importance as fertilization hormones. Carotenoids may be present in the gonads to ensure that the larvae are adequately equipped for chromatophore responses. Changes in general coloration associated with sexual activity are also often mediated through carotenoids; in the case of the fish Cyclopterus lumpus, for example, astaxanthin appears in the skin in large amounts during the summer spawning period. Similar changes can be observed in some insects, for instance, the bright yellow colour of sexually mature locusts is due to accumulation of β‐carotene in the cuticle.

In mammals which store carotenoids, these pigments undergo metabolic changes associated with parturition, but as not all mammals store carotenoids, and since many similar changes occur with vitamin A, it is doubtful whether the carotenoids are of significance per se.

Although carotenoids appear to be unnecessary for the normal development of birds in both the pre‐ and post‐embryonic stages, they are actively mobilized into birds' eggs. They may, however, be necessary for optimum conditions of fertilization by increasing the sperm competitive ability of cocks, i.e. when hens are inseminated with an equal mixture of spermatozoa from cocks on an adequate diet and those on a lutein‐deficient diet, a larger proportion of offspring are produced from the normal group than from the lutein‐deficient group.
CEPHALOPOD PHYLOGENY AND CLASSIFICATION
Authors: DONOVAN D. T.
Published: January 2008

1. A mode of origin of cephalopod buoyancy, by withdrawal of the animal from the apex of the shell followed by withdrawal of liquid from the resulting space, is suggested.

2. Buoyancy, once evolved, gave cephalopods an immediate advantage over contemporary animals and evolutionary radiation in the early Ordovician was a consequence of this.

3. The earliest cephalopods probably had curved (cyrtocone) shells. Tightly coiled shells evolved from cyrtocones in at least two separate lineages and were in the first place adapted to a benthonic existence. Straight shells (orthocones) were adapted for efficient swimming. They usually had apical counterweights to maintain a horizontal position, but in forms without counterweights, liquid‐filled chambers could have served the same purpose.

4. Six evolutionary branches are described, which were distinct by the end of the Canadian (Lower Ordovician). Each branch is believed to be monophyletic, and up to a point each is characterized by certain structures or trends.

5. Increased efficiency in jet propulsion became possible in one orthocone group, consequent on loss of the ventral wall of the body‐chamber, so that the mantle cavity wall could become muscular and contractile. This group gave rise to the living di‐branchiates, or Coleoidea.

6. The primitive septum, which was concave forwards, remained standard in most orthocones and in some coiled shells. Folded septal edges, giving rise to more or less complex septal sutures, evolved independently in a number of coiled lineages. Their significance is unknown.

7. The siphuncle is simple and small in all coiled shells and in some orthocones. In some cyrtocones and other orthocones large siphuncles of complex structure were evolved. They usually contain deposits which are interpreted as counterweights.

8. Existing classifications of cephalopoda stem from subdivisions recognized in the nineteenth century when knowledge of fossils was inadequate. They are ill‐balanced and should be abandoned.

9. A classification based on phylogeny is now possible. The six branches already described may be regarded as major subdivisions. In addition, it may be desirable to subdivide branches on the basis of important evolutionary changes. The strongest case is for the separation of Coleoidea on the grounds of the loss of the shell.
THE SURVIVAL OF FUNGAL SCLEROTIA UNDER ADVERSE ENVIRONMENTAL CONDITIONS
Authors: WILLETTS H. J.
Published: January 2008

1. Sclerotia have been found to survive under adverse environmental conditions for long periods. Their viability is retained at low and subzero temperatures, while it is progressively reduced at temperatures above about 15° C. Dry conditions and lack of competition from other organisms favour survival. Depletion of food reserves results in loss of resistance to environmental factors.

2. The majority of sclerotia consist of an outer layer of thickened, close‐fitting, often pigmented cells that form a rind over a tissue of closely interwoven hyphae. A cortex and medulla is often discernible.

3. Features of sclerotia that are important in overcoming the harmful effects of desiccation and extremes of temperature include: the presence of a rind and sometimes an additional covering of either fungal or host tissue; the compact nature of the sclerotium; miscellaneous protectants on the surface of and in the hyphae; melanized hyphal walls; high intracellular osmotic concentrations; slow air‐drying to lower moisture content. Also the buffering action of the soil and the protection afforded by vegetation and plant debris are important.

4. The active exudation of water, the accumulation and secretion of soluble carbohydrates during sclerotium development and maturation, and the formation of large amounts of mucilage are of significance in resistance to desiccation, extremes of temperature and radiations.

5. The nature and the pigmentation of the rind together with the site of sclerotium development may give protection against harmful radiations.

6. The loss of sclerotium viability caused by toxic chemicals in the soil and atmosphere or by the enzymic activities of other organisms is reduced by the rind and the melanization of hyphal walls.

7. Survival under starvation conditions is achieved by the accumulation of abundant food reserves (lipids and/or carbohydrates) and a low level of metabolic activity. In the presence of a compatible host exogenous sources of energy are sometimes used.

8. Although the sclerotium is highly adapted to survive adverse conditions for long periods, sometimes micro‐environmental conditions may be so severe that only a few sclerotia can retain their viability. However, even a few such comparatively large bodies, rich in food reserves, have a considerable inoculum potential.
SIALIC ACID AND THE SOCIAL BEEIAVIOUR OF CELLS
Authors: LLOYD CLIVE W.
Published: January 2008

1. It is suggested that specific carbohydrate side‐chains of membrane glycoproteins are the sites for cell recognition or adhesion when the terminal sugar, sialic acid, is absent.

2. It is suggested that sialic acid plays a ‘protective’ or ‘blocking’ role in cell interactions so that addition of sialic acid to asialo side‐chains converts them to forms inactive for recognition. This principle of ‘blocking’ by sialic acid has been observed in other situations as in covering tumour antigens and in protecting glycoproteins from uptake by the liver. It is here extended to cell‐cell adhesions.

3. It is to be expected that specific ‘protective’ actions of sialic acid in membrane‐bound glycoproteins will be difficult to detect. As a charged residue, sialic acid is likely to have a strong influence both on the glycoproteins on which it is borne and on their interactions with each other at the cell surface. Removal of sialic acid by enzymes could therefore perturb the structure of the cell surface in several ways and so obscure the ‘protective’ effects of sialic acid. Sialic acid is therefore suggested to have a structural role also.

4. Evidence is assembled in favour of a model in which sialysation of specific adhesive receptors affects the social behaviour of cells. This may be an effect associated with growing cells since the contact properties of mitotic cells (and populations rich in dividing cells) are decreased by the increased sialysation of receptors. One of the factors associated with malignant behaviour could be that adhesive receptors are permanently blocked by sialic acid.

5. A schematic representation of some of the points is given in Fig. 4.
GENETIC STUDIES OF NITRATE ASSIMILATION IN ASPERGILLUS NIDULANS
Authors: COVE D. J.
Published: January 2008

(1) In Aspergillus nidulans, at least 16 genes can mutate to affect the reduction of nitrate to ammonium, a process requiring two enzymes, nitrate reductase and nitrite reductase.

(2) niaD is the only gene whose effects on enzyme structure are confined to nitrate reductase alone. It specifies a core polypeptide, one or more of which form the basic subunit of nitrate reductase, molecular weight 50000.

(3) At least five cnx genes together specify a molybdenum co‐factor, necessary for the activity of nitrate reductase, and of xanthine dehydrogenases I and II. The cnxH gene specifies a polypeptide component of this co‐factor, and the cnxE and F gene products are involved in co‐factor elaboration, The role of the remaining cnx genes is at present unknown.

(4) Functional nitrate reductase has a molecular weight of 200000 and is likely to consist of four subunits, together with one or more molecules of the cnx‐specified co‐factor.

(5) The co‐factor plays a catalytic role in the aggregation of nitrate‐reductase subunits.

(6) The niiA gene is the structural gene for nitrite reductase.

(7) Other genes affecting nitrate assimilation are either regulatory or bring about their effects indirectly.

(8) Of the genes affecting nitrate assimilation, close linkage is found only between the niiA and niaD genes.

(9) Nitrate and nitrite reductases are subject to control by nitrate induction and ammonium repression.

(10) Nitrate induction is mediated by the nirA gene whose product must be active for the niiA and niaD genes to be expressed. Since most niaD mutants produce nitrite reductase constitutively, it is likely that the nirA gene product is normally inactivated by nitrate reductase, but only when the latter is not complexed with nitrate,

(11) Ammonium repression is mediated by the areA gene, whose product must be active for the expression of the niiA and niaD genes, and which is inactive in the presence of ammonium.

(12) The tamA gene may function similarly to the areA gene, both gene products being necessary for the expression of the niiA and niaD genes.

(13) Although the niiA and niiD genes are probably contiguous, they are not likely to be organized into a structure equivalent to a bacterial operon.

(14) Whereas the areA and nirA genes regulate the synthesis of nitrate and nitrite reductases, it is probable that at least nitrate reductase is also subject to post‐translational control, the presence of active enzyme being correlated with high levels of NADPH.

(15) The regulation of the pentose‐phosphate pathway, of mannitol‐I‐phosphate dehydrogenase and of certain activities required for the catabolism of some nitrogen‐containing compounds appears to be connected with that of nitrate assimilation. In all cases, it is probable that the nirA gene and nitrate reductase itself are involved.
MYCORRHIZAS OF AUTOTROPHIC HIGHER PLANTS
Authors: SMITH SALLY S. E.
Published: January 2008

(1) The range of mycorrhizal types is briefly compared, with respect to structure and nutritional mode of the symbionts. Ectotrophic, vesicular‐arbuscular and erica‐ceous mycorrhizas of autotrophic plants are selected for further consideration, both because the symbionts have nutritional similarities, and because recent experimental work provides a basis for useful comparisons.

(2) A generalized, qualitative model of interactions between the symbionts is presented, with the aim of providing a framework for discussion of the similarities and differences between the mycorrhizas of autotrophic plants. The model describes the distribution of biomass and the flow of carbon and mineral nutrients, together with the effects of distribution of fungal inoculum and environmental conditions.

(3) Experimental work pertaining to the model is discussed with emphasis on experimental problems, growth depressions, changes in root: shoot ratio and nitrogen nutrition, as well as the more frequently discussed increases in growth and improved phosphorus nutrition.

(4) Nitrogen is considered with respect not only to its uptake, but also in relation to the possible involvement of mycorrhizas in pH regulation and the absorption of cations by plants.

(5) The importance of mycorrhizas in forestry and agriculture is briefly discussed.

(6) It is concluded that more research into the physiology and ecology of mycor‐rhizal associations is required, in order to provide a basis for effective management of the symbioses in agricultural and natural ecosystems.
REGULATION OF HAEMOPOIESIS IN ALTERED GRAVITY
Authors: Economos Ancelos C.
Published: January 2008

(1) The aetiology of one of the most striking physiological changes occurring during space‐flight, the loss of red blood cells, remains unknown, and its precise time‐pattern in flight has not yet been studied.

(2) It is suggested that the changes during space‐flight responsible for loss of red blood cells in man are (a) loss of plasma volume resulting from disappearance of hydrostatic pressure in the circulation during weightlessness and (b) reduced energy expended in maintenance of form, posture and locomotion resulting from elimination of the usual gravitational load on the muscles. Quadrupeds, like rats, would be expected to suffer minimal blood shifts in weightlessness and therefore have an unchanged plasma volume. However, since in weightlessness the activity‐related energy expenditure by the muscles is reduced, the accompanying reduced oxygen demand by the tissues would cause a reduction in erythropoietin levels and so in the production of red blood cells, and a progressive lowering of the total red blood cell mass toward a new steady‐state level.

(3) Loss of plasma volume alone does not explain the observed loss of red blood cells in astronauts because, in the three manned Skylab missions, as the duration of the missions increased, loss of red blood cell mass decreased, whereas loss of plasma volume increased. This discrepancy is, however, well accounted for by the above hypothesis by taking into consideration the increased level of exercise of the astronauts as the duration of the mission increased.

(4) Though water submersion of human subjects does mimic the effects of weightlessness, such effects were overriden in sea mammals because of adaptation to other factors associated with a life in the sea.

(5) From the presented analysis of haemopoietic changes observed in spaceflight, an experiment can be designed for a future flight to uncover the causes and mechanisms of these changes and provide a basis for developing protective measures. Thus, the space environment can be used as an investigative tool to enhance the knowledge of the function of the haemopoietic system, which is a major homeostatic system of man and other vertebrates.
PROPERTIES OF AVIAN EGG SHELLS AND THEIR ADAPTIVE VALUE
Authors: BOARD R. G.
Published: January 2008

I. An arbitrary classification of avian eggshells is proposed.

2. The role of the eggshell in conserving the water in eggs at oviposition is discussed. There is as yet no correlation between this property and the pore systems in avian eggshells.

3. The pore systems may act as diffusion pathways and the hypothesis has been advanced that in many eggs the shells are adapted so that restriction of gaseous diffusion by mud, preening oils and nest debris is prevented.

4. The mechanical properties of the shell are considered in the novel context of defence against (a) attrition that could lead to the pores being blocked with dust, and (b) cracking that would destroy the diffusion pathways noted in 3.

5. The overall objective of the review was to discuss the concept that avian eggshell are adapted to fit an egg to the nest environment.
CALCIUM BALANCE AND MOULTING IN THE CRUSTACEA
Authors: GREENAWAY PETER
Published: January 2008

1. Crustaceans have a high content of calcium, which is chiefly located in the skeleton as calcium carbonate. Calcium is generally the most abundant cation in the body.

2. During intermoult, the exoskeleton is usually fully calcified and the animal is in calcium equilibrium with its environment.

3. In the premoult stages calcium is resorbed from the skeleton and may be lost to the environment or stored within the body. Typically, losses are high and storage is small in aquatic species, whilst most terrestrial forms store much larger amounts of calcium and losses are reduced. Loss of calcium in soluble form by aquatic species must be by outward transport across the gills.

4. Calcium is stored in a variety of different ways, usually with a common taxonomic theme. The main forms are as calcium phosphate granules in cells of the midgut gland (Brachyura), gastroliths (Astacidea and some Brachyura), the haemocoel (some Brachyura) the posterior midgut caeca (Amphipoda) and the ventral portion of the body generally in the Isopoda.

5. At ecdysis, the skeleton is shed and the calcium remaining in it is lost from the body.

6. Recalcification begins immediately, or shortly after, ecdysis using calcium mobilized from the stores. Simultaneously, or when the stores are exhausted, other sources of calcium are utilized. These are calcium in the water (aquatic species), the food (aquatic and terrestrial species) and the exuviae (chiefly terrestrial species).

7. Marine species store little calcium and must obtain the bulk of their requirement (ca. 95%) from the water. Fresh‐water species also store little calcium but have, seemingly, adapted to the lower availability of calcium by increasing the affinity of the calcium‐absorbing mechanism. The rates of uptake of calcium are consequently similar in marine and fresh‐water species.

8. A high degree of storage is essential for terrestrial crustaceans as they do not have access to a large aquatic reservoir of calcium. These large reserves enable the animals to reach an advanced stage of calcification, allowing the resumption of foraging and feeding necessary for completion of calcification.

9. The control of calcium metabolism during the intermoult cycle is poorly under stood. β Ecdysone appears to control the resorption of calcium and the formation of calcium stores during premoult, but the mechanism of control of calcium metabolism during postmoult and intermoult is unknown.

10. The concentration of calcium in the haemolymph of most species is high, but a large proportion of this is in non‐ionized form. In premoult, total calcium levels rise as a result of calcium resorption but little change occurs in the concentration of ionized calcium. Postmoult generally sees a fall in blood calcium, sometimes below the intermoult value.
CLOTTING PROCESSES IN CRUSTACEA DECAPODA
Authors: DURLIAT MICHÈLE
Published: January 2008

1. In Limulidae, all the factors involved in the coagulation processes are located inside the amoebocytes. The cellular coagulogen is a single 20,000‐polypeptide‐chain protein. It is converted into a non‐covalently crosslinked gel by a serine protease enzyme which cleaves a single peptide bond, releasing peptice C.

2. Pro‐clotting enzyme can be activated by two independent pathways: coagulation is induced by either LPS or 1,3‐β‐D‐glucan, both of which result in gel formation. The two pathways comprise a complex enzyme cascade with several limited protein proteolyses.

3. In Decapoda, clotting factors are found in both the cell‐free plasma and haemocyte compartments. Analogous factors are present in Insecta.

4. Plasma coagulogen is a 400,000 molecular weight protein with both lipid and carbohydrate moieties. Its soluble polymers are converted into covalently crosslinked polymers of coagulin by Ca2+‐dependent transglutaminase. In crayfish, it is also found in other tissues such as soft integument and calcified cuticle. Its concentration varies greatly with the species investigated. It seems to possess many diversified functions such as plasma coagulation, protein transport of tanning agents, lipid and sugar transport and protein storage, and resembles fibronectin.

5. A type of cellular coagulogen seems to be present in the haemocytes of Decapoda. It can be converted to a gel by a serine protease pro‐clotting enzyme. This pro‐enzyme can be activated by either LPS or 1,3‐β‐D‐glucans. The mechanism of LPS action is not entirely clear. 1,3‐β‐D‐glucans also activate the prophenoloxidase system and cause phenoloxidase attachment to foreign surfaces of haemocyte lysates. The latter system is restricted to semi‐granular and granular haemocytes, and plays an important part in host‐defence reactions.

6. The evolutin of clotting processes throughout the phylogenetic tree is discussed.
THE AVIAN SALT GLAND
Authors: HOLMES W. N. , PHILLIPS J. G.
Published: January 2008

1. Since the electrolyte concentrating capacity of the avian nephron is insufficient to excrete all of the ingested electrolyte when the bird consumes hyperosmotic drinking water, an extra‐renal pathway is necessary to maintain homeostasis.

2. In birds living in coastal and estuarine environments, and in terrestrial environments where the available drinking water is also hyperosmotic with respect to their body fluids, paired salt glands situated in the orbits have evolved as extra‐renal excretory organs.

3. These excretory organs wax and wane functionally in species that migrate between these environments where there is an abundance of freshwater.

4. This functional development of the glands involves the synthesis of new protein and the differentiation of additional excretory tissue that is reflected in the overall growth of the gland.

5. When activated, the glands secrete a fluid containing high concentrations of Na+, Cl‐ and K+ and during prolonged periods of exposure to hypertonic drinking water the birds are able to excrete sufficient quantities of these ingested ions to permit them to remain in positive water balance.

6. The mechanisms responsible for producing the characteristic hyperoosmotic fluid discharged by the activated salt glands appear to be located at two sites: (a) in the principal cells of the secretory tubules, where there is a ouabain‐sensitive Na+‐K+‐dependent ion transporting system located in the basolateral membranes and a furosemide‐sensitive Na+ and Cl‐ co‐transport mechanism located in the basal membrane, and (b) in the complex system of collecting ducts into which the secretory tubules discharge their fluid; the cells lining the duct also possess a ouabain‐sensitive ion transporting system.

7. In the activated gland the Na+‐transporting system operates intermittently to produce excretory fluid only during periods immediately following the ingestion of hyperosmotic drinking water, and secretion ceases when the bird has gained sufficient osmotically‐free water to maintain homeostasis.

8. The initiation and continuation of salt gland secretion occurs in response to the stimulation of an osmoreceptor, probably located in the cardiac vasculature.

9. Sensory impulses arriving in the central nervous system are relayed via parasympathetic motor neurones to muscarinic receptors in the cells of the secretory tubules; the Na+‐K+ dependent ATP‐ase system located in the basolateral membranes is then activated by a cyclic GMP‐mediated mechanism.

10. Sustained salt gland secretion is also dependent upon activation of the pituitary‐adrenal axis. The corticosteriod hormones secreted as a result of this activation interact with specific cytosolic and nuclear receptor macromolecules in the cells of the secretory tubule. Transcriptional changes are presumed to be necessary for sustained extrarenal excretion.

11. Thyroid hormones and prolactin may also be involved indirectly to support continued extrarenal excretion via the salt glands.
THE CORTICAL MAGNIFICATION FACTOR AND PHOTOPIC VISION
Authors: POINTER JONATHAN S.
Published: January 2008

1. The concept of a topographical representation of sensory surfaces on the mammalian cerebral cortex is now well established. Furthermore, there is claimed an expanded representation for those sensory surfaces associated with behavioural specializations.

2. In the case of the visual system, the field of view associated with the retina is projected on to the striate cortex, with the central fovea or point of most acute vision occupying a disproportionately large area of representation.

3. The term ‘cortical magnification factor’, denoted by M, has been introduced to indicate, for a given eccentricity and meridian, the linear distance in mm along the primary visual cortex concerned with each degree of visual field.

4. The quantitative accuracy of this function subsequently has been improved and a relationship established between cortical magnification and visual acuity in man.

5. On the basis of spatio‐temporal investigations across the visual field under levels of photopic adaptation, visual scientists have utilized retino‐cortical magnification to reconcile aspects of structure and function in the human visual system.
THE ROLE OF HETEROCHRONY IN THE EVOLUTION OF CAMBRIAN TRILOBITES
Authors: McNAMARA K. J.
Published: January 2008

1. Renewed interest in the role of changes to developmental regulation in organisms has highlighted the importance of heterochrony in the evolution of the Metazoa.

2. Beecher's interpretation of the evolution of the Trilobita as having been principally by peramorphosis is examined, as is the view of later workers, principally Stubblefield and Hupé, that paedomorphosis was a dominant factor in trilobite evolution.

3. Both peramorphosis and paedomorphosis are considered to have been important in trilobite evolution.

4. The role of paedomorphosis in the evolution of major morphological novelties is critically examined. Its importance in changes to the structure of the glabella is discussed and new terms proposed to describe the ontogenetic and phylogenetic state of the glabella.

5. The highly variable nature of early Cambrian trilobites, in particular the large degree of ontogenetic change, is considered, along with possible poor developmental control of the growth and moulting hormonal systems, to have been significant in providing a high degree of intrapopulational morphological variability. Selection of these heterochronic variants was responsible for the rapid diversification of the Trilobita during the Cambrian.
OPERATION OF THE PURINE NUCLEOTIDE CYCLE IN ANIMAL TISSUES
Authors: WAARDE AREN VAN
Published: January 2008

1. The operation of the purine nucleotide cycle, consisting of the enzymes adenylate deaminase (E.C. 3.5.4.6), adenylosuccinate synthetase (E.C. 6.3.4.4) and adenylosuccinate lyase (E.C. 4.3.2.2), has been reviewed with reference to its metabolic function in animal tissues.

2. Abundant evidence, both from in vitro and in vivo studies, suggests that the purine nucleotide cycle serves to stabilize the adenylate ‘energy charge’ (or ‘phosphorylation potential’) in the cytoplasm of vertebrate cells during a temporary imbalance between ATP‐consumption and ATP‐production. This stabilization, however, is absent or much less efficient in tissues of invertebrates.

3. The hypothesis that AMP‐deaminase is involved in the regulation of glycolysis is not supported by recent work. In a variety of cell types, including skeletal muscle and blood platelets, blocking of AMP‐deaminase activity (due to a genetic defect or to pharmacological inhibition) is without effect on the glycolytic rate. Detailed kinetic and histochemical analysis of energy metabolism shows lack of correlation between AMP‐deaminase activity and glycolysis in skeletal muscle during exercise.

4. The purine nucleotide cycle appears to control the level of citric acid cycle intermediates in skeletal muscle. Pharmacological inhibition of adenylosuccinate lyase or adenylosuccinate synthetase leads to a reduced availability of four‐carbon ‘sparker’ molecules to the Krebs cycle with a concomitant impairment of aerobic energy production during muscular work.

5. The cycle appears to be a major pathway for amino acid deamination in skeletal muscle and brain of vertebrates, but not in kidney or liver.
MATING FREQUENCY AND FECUNDITY IN INSECTS
Authors: RIDLEY M.
Published: January 2008

1. The paper summarizes the published evidence on the relation between mating frequency and fecundity in insects. There is experimental evidence of varying quality for 63 species and non‐experimental evidence for about 60.

2. Repeated mating may be universally necessary for full fecundity and fertility in female insects (in species in which the females normally mate more than once).

3. The evidence is remarkably poor. We need more properly designed experiments (and not just observations of natural variation), with sufficient sample sizes and statistics, and measurements of the fecundities and fertilities of singly and multiply mated females, when the multiple matings are separated by many days or weeks. Most of the existing experiments of this sort are defective in some way.

4. In species with greater total fecundity and longevity, multiple mating may be more likely to enhance fertility than in species with small fecundity and short life span.

5. Females in naturally monandrous species do not show increased fecundity or fertility with repeated mating, whereas females of polyandrous species do.

6. There is no obvious connexion between paternal investment, in so far as we know about it, and the increase of fecundity by repeated mating.

7. There is a small tendency for females to breed more quickly and be shorter lived if they mate repeatedly.
AN ACCOUNT OF THE HATCHING STRATEGIES OF BIRDS
Authors: BOND G. M. , BOARD R. G. , SCOTT V. D.
Published: January 2008

1. Three basic hatching methods are described together with one subsidiary method. The symmetrical method is characterized by rotation of the chick in the egg during hatching climax; a line of damage around the circumference of the egg is evident at the beginning of a pushing phase which causes a fairly symmetrical cap to be broken from the shell. The asymmetrical method is used by a few long‐billed species; it involves little or no rotation of the chick in the egg, and produces asymmetrical shell remains. The megapodes have developed a unique hatching method in response to their unusual incubation conditions. Parental assistance has been observed in some species, but only as an auxiliary to either the symmetrical or asymmetrical method. Approximately 150 species have been categorized according to the hatching method(s) they use.

2. Among those species adopting the symmetrical method, there is considerable variability as to how far the chick turns in the egg during hatching climax. On this basis, a spectrum of behaviour, expressed in terms of angle of rotation (θ), has been proposed. At one end lie species such as the bobwhite quail and little owl (θ≥ 360°), and at the other, the ostrich and rhea (θ≤ 90°).

3. The theory that, with the exception of the megapodes, there is only one basic hatching method is examined. The tenets of this theory are found to be inconsistent with recent observations of species differences in hatching behaviour. It is concluded that hatching behaviour is governed by an intrinsic species‐specific programme, in turn influenced by mechanical or other external factors.

4. The literature contains several suggestions as to the external factors that might influence hatching technique, but only one detailed investigation. It is proposed that interspecific differences in the mechanical properties of the egg integument (the shell and its underlying membranes) can be regarded as forming a spectrum from very brittle to comparatively tough. The amount of climax rotation by the chick is seen as an adaptive response to brittleness or toughness of the egg integument. The hatching technique of the chick is further modified as a response to the effect of moisture content on the integument.

5. The selective pressures leading to the evolution of the symmetrical and asymmetrical hatching methods are discussed. The previous model for the development of the asymmetrical method is amended to account for those species of gull which may adopt either method.
CHEMICAL COMMUNICATION IN INSECT COMMUNITIES: A GUIDE TO INSECT PHEROMONES WITH SPECIAL EMPHASIS ON SOCIAL INSECTS
Authors: ALI MAHMOUD FADL , MORGAN E. DAVID
Published: January 2008

Chemical communication plays an important part in the lives of insects, and particularly in lives of those that live in groups or social organizations.

Chemicals which are used in communication in the general sense are called semiochemicals, and there are a number of subdivisions recognized under this title.

Pheromones are a category of semiochemicals which are used for communication between individuals of the same species.

Pheromones are in turn subdivided into primer and releaser pheromones. The former produce a relatively long‐lasting physiological change in the receiver, and the latter stimulate the receiver to some immediate behavioural response.

Far more is known about releaser pheromones at present because they are easier to study.

Nine categories of releaser pheromone are recognized here, used by both social and non‐social insects.

Sex pheromones are widely used to bring the sexes together for mating, and they have been extensively studied in Lepidoptera.

Invitation pheromones, encouraging the species to feed or oviposit at an explored site, are not extensively known.

Aggregation pheromones are designed to bring individuals together into groups which may be temporary in sub‐social insects, or permanent in social insects.

Dispersal or spacing pheromones are used by other species to reduce intraspecific competition for scarce resources.

Alarm pheromones are a broad and sometimes unclearly defined group which communicate alarm or attack, chiefly in colonial species.

Trail pheromones, applied to a surface by an individual, to be followed by another, are confined to Hymenoptera, Isoptera and a few Lepidoptera as far as is known.

Territorial and home range pheromones may be widely distributed, but as yet few of them have been recognized.

Surface and funeral pheromones are even less well known. Surface pheromones may play a large part in species or colony recognition.

We can expect the number and complexity of pheromones to be much greater in social insects, a part of the subject which until now has received relatively less attention.

As our understanding of the subject grows we may expect other categories to be added to this list.
EVOLUTION OF MONOGAMY IN TERMITES
Authors: NALEPA CHRISTINE A. , JONES SUSAN C.
Published: January 2008

Two hypotheses have been proposed to explain the origin of lifetime monogamy in the Isoptera. The classic explanation is that (1) the male must be present to continually provide sperm for the vast number of eggs produced by the queen (Snyder, 1924: Brian, 1983). Thornhill & Alcock (1983) proposed that (2) synchrony in the availability of receptive females necessitates mate guarding; males subsequently gain if they improve the relative reproductive success of their sole partner.

Our review of the literature on termite flight behaviour, courtship behaviour, and incipient colony development indicates that neither of these two hypotheses satisfactorily explains the evolution of monogamy in termites. Because incipient colonies of lower termites exhibit a very low fecundity, it is doubtful that the continued presence of the male initially was due to the need for a continuous supply of spermatozoa. It is possible, however, that sperm requirements for the fertilization of numerous eggs over an extended period of time may be a factor in the persistence of the termites' monogamous mating system. Female alates are much more dispersed in time than implied by Thornhill & Alcock (1983) and there is no evidence of mate guarding. The importance of mate assistance is, however, supported by the literature. We propose a third hypothesis that incorporates the mate assistance element of the Thornhill & Alcock hypothesis: (3) the monogamous mating system of termites was structured by ecological constraints, namely, the low quality and scattered nature of their food/nesting material and the high costs of searching for a mate.
THE OCCURRENCE AND ADAPTIVE SIGNIFICANCE OF NOCTURNAL HABITS IN WATERFOWL
Authors: McNEIL RAYMOND , DRAPEAU PIERRE , GOSS‐CUSTARD JOHN D.
Published: January 2008

This paper reviews the occurrence of nocturnal activity, particularly foraging, in wildfowl (Anseriformes) and shorebirds (Charadrii), and discusses its significance. Many duck species are mainly active at night while others regularly feed during both the day and night. Some ducks and geese are normally day feeders and occasionally forage during darkness. In a few duck species, courtship also has been observed at night. Most shorebirds forage both by day and night, in temperate and in tropical latitudes. Some are mainly crepuscular and nocturnal feeders and also display at dusk and at night. Some species may use their daytime territory at night.

A few shorebird species, including some visual peckers and long‐billed tactile probers, use the same foraging method to detect and capture food by night as by day. However, some long‐billed species that forage visually during daytime modify their feeding techniques and rely completely or partly on tactile means for detecting prey at night. Large eyes seem an advantage to plovers and other sight feeders for night feeding. Numerous touch‐sensitive corpuscles in the bill of ducks and many scolopacid species favour tactile feeding. Some ducks, geese and shorebirds may especially use moonlit nights for feeding though, in a few species, moonlight seems to have no effect. The possible role of bioluminescence is also discussed.

Nocturnal activity may occur for two reasons. The night may be preferred because foraging is more profitable or safest from predators. Alternatively, birds may be forced to forage at night because they fail to collect all their food requirements during the day. The evidence for both hypotheses is reviewed. Nocturnal activity does appear to allow wildfowl, and perhaps shorebirds, to avoid diurnal predators (including man). Shorebirds, and some ducks also seem to take advantage of prey that are more abundant and/or accessible at night. The main evidence for the supplementary feeding hypothesis comes from studies of seasonal variations in the occurrence of nocturnal feeding, about which rather little is known at present. The increasing availability of modern night‐viewing equipment may help to fill this gap.

There are two important implications arising from the widespread occurrence of nocturnal activity in wildfowl. Most knowledge on time and energy budgets is based on daytime studies, and so may need to be revised. Wintering dabbling ducks and shorebirds, at least in some regions, may use different habitats by day and by night. If confirmed, there would be a need to preserve some wintering habitats which, although little used by ducks and shorebirds during the day, may be intensively used at night.
THE ORIGIN OF THE LAND PLANT SPOROPHYTE: AN INTERPOLATIONAL SCENARIO
Authors: HEMSLEY By ALAN R.
Published: January 2008

The origin of terrestrial plants from a charophycean ancestor is assumed as a basis for the consideration of the origin of life histories amongst this group. Charophycean algae are vegetatively gametophytic, thus requiring the interpolation of the multicellular sporophytic stage. The model presented here derives the sporophyte and typical sporangial contents from the zygospore produced from the reproductive structure of a hypothetical charophycean land plant ancestor. The presence of monads, dyads, and various forms of tetrads in the fossil record of presumed land plants add support to this model. In addition, such spore types suggest that the temporal relationship of meiosis to sporopollenin deposition was less strictly controlled than in extant land plants.
ALTERNATION OF GENERATIONS IN FERNS: MECHANISMS AND SIGNIFICANCE
Authors: SHEFFIELD By E.
Published: January 2008

Arguments against the compiling of generalized life cycles summarizing alternation of generations in ferns are presented, and some common misconceptions about breeding systems addressed. What little is known or can be deduced about time frames, mechanisms and significance of alternation events in the lives of two species: bracken fern (Pteridium) and Killarney fern (Trichomanes speciosum) is presented. Evidence is provided that gametophytes may play a more important role in survival of both these species than previously suspected, and the need for more long‐term studies and experiments/measurements of ferns in natural conditions/populations is stressed.