Neurosecretory system of the earwig Labedura riparia, and the rôle of the aorta as a neurohaemal organ

The neurosecretory system of Labedura riparia has been described from sections and whole mounts using a variety of techniques. The pars intercerebralis contains two clusters of medial neurosecretory cells (MNC), each cluster consisting of 8 to 10 A-cells and occasional B-cells. The lateral sides of the brain have a few B-cells. The axons of the median neurosecretory cells terminate in the cephalic aorta (AO), whereas the axons of the lateral neurosecretory cells (LNC) terminate in the corpora cardiaca (CC). It appears that the neurosecretory material (NSM) elaborated in the MNC is stored in the cephalic aorta and that elaborated in the LNC is stored in the corpora cardiaca, which are two oval or elongate bodies composed of large chromophobe and small chromophil cells. Posteriorly there is the oval or elongate corpus allatum (CA) attached to the CC by thick nerves. The CA consists of one cell type only. Both CC and CA contain no A-cell neurosecretory material. It has been suggested that the neurosecretory system of L. riparia is composed of two complexes. One is formed by the medial neurosecretory cells for which the aorta functions as a neurohaemal organ, and the other is formed by lateral neurosecretory cells-lateral neurosecretory pathways-nervi corporis cardiaci-II in which the corpora cardiaca function as a neurohaemal organ.     

The rôle of ecdysone in pupation of Manduca sexta

Slow infusions of β-ecdysone are more effective in eliciting a normal physiological response than are discrete injections of the hormone. Infusion of β-ecdysone into final instar larvae in the presence of juvenile hormone (JH) induces apolysis and the deposition of a normal larval cuticle. In the absence of JH larvae display the prodromal symptoms of pupation (exposure of the heart, purging of the gut, etc.) in response to a β-ecdysone infusion. The occurrence of certain covert physiological events that accompany the exposure of the heart are evidently necessary to prepare a larva for pupation. An infusion of β-ecdysone can induce apolysis and pupal cuticle deposition only after the prodromal signs of pupation have become evident. Of the two pulses of ecdysone that normally precede pupation in Manduca, the first is apparently responsible for the genetic switchover from larval to pupal development whereas the second one triggers apolysis and the subsequent events that lead to pupation. Results obtained from infusion experiments in which the dose and exposure time were varied independently are consistent with the idea that ecdysone has to be present for a certain minimum time above a threshold concentration to induce a physiological response. The requisite exposure time is apparently not dose-dependent.     

The rôle of amino acids in diet intake and selection and the utilization of dipeptides by Aphis fabae

Eight amino acids considered essential for the growth of Aphis fabae were investigated in relation to their rôle in protein synthesis and phagostimulation. When either alanine, histidine, methionine, proline, or serine were omitted from synthetic diets, intake was lower than that of the complete diet over a 4 day period. The omission of cysteine, phenylalanine, or tyrosine failed to reduce diet intake. Histidine and methionine were considered essential for protein synthesis and did not act as phagostimulants; alanine and proline, however, appeared to act primarily as phagostimulants. When subjected to choice chamber tests aphid larvae had a severely limited ability to select between complete diets and ones deficient in a single amino acid. If methionine and glycine were replaced by either glycyl l-methionine or l-methionyl glycine the size attained by larvae during growth was less than that of aphids reared on a complete diet but greater than that of aphids reared on diets deficient in both dipeptides and methionine.     

Rôle of the midgut,crop, and maxillae of Bombyx mori in the production of cocoon-digesting enzyme

The rôle of the midgut, crop, and maxillae in the production and utilization of the cocoon-digesting enzyme was investigated in the silkworm, Bombyx mori.About a sixtyfold purified preparation of midgut protease was obtained by ammonium sulphate precipitation and column chromatography.Immunological studies by the agar diffusion method of Ouchterlony revealed that the crop and midgut proteases of the pharate adult are antigenically identical whereas that of the maxillary protease is different.From the results of extirpation experiments and previous studies it was shown that the midgut, crop, and maxillae play important rôles in the escape of moths from their cocoons.     

The rôle of the spermathecal gland of the boll weevil,Anthonomus grandis

Spermatozoa were relatively inactive and did not enter the spermatheca of female boll weevils, Anthonomus grandis, whose spermathecal glands were removed as teneral adults. However, these females were able to lay fertile eggs for a 2 week period. When the spermathecal gland was removed from older females, spermathecal filling occurred, and although the spermatozoa retained their fertilizing capacity for extended periods, spermathecal emptying did not occur. Spermatozoa gradually lost their motility and fertilizing capacity, indicating that spermathecal secretions are effective in very small amounts. Spermatozoa were not activated by any of the materials contained in the normal male ejaculate. These materials alone did not effect spermathecal filling nor were they capable of maintaining the fertilizing capacity of the spermatozoa for very long. Sperm economy is low with less than 1 fertile egg laid per 100 spermatozoa used.     

The rôle of the plastome in evolution of the genusOenothera

In the subgenusEuoenothera, five plastid types can be identified. The same major groups of genome complexes as established byCleland, stand out when attention is focused on the co-operation between genomes and plastomes.Experiments on plastid competition and plastid-genotype compatibility lead to an unambiguous interpretation of phylogenetic relations within the subgenus.Based on a paper read at the XI International Congress of Genetics, The Hague, of which an abstract has been published in theProceedings, Vol. I, p. 131–132 (1963).     

Rôle of single amino acids in phagostimulation,growth, and survival of Acyrthosiphon pisum

Twelve amino acids and amides at 0·1 to 0·75 or 1·0% in 35% sucrose solution were individually tested for their rôle in phagostimulation, growth, and survival in Acyrthosiphon pisum. Leucine and phenylalanine were phagostimulatory at all concentrations tested, tryptophan and valine at 0·1, 0·2, and 0·5%, and threonine at 0·1% only. Methionine was reported earlier by us to be phagostimulatory at 0·05 to 0·5%. Histidine and isoleucine had no effect, whereas arginine and lysine HCl reduced uptake when compared to sucrose alone. The non-essential amino acids, canavanine sulphate and glutamine, reduced uptake at all concentrations, whereas homoserine was phagostimulatory at 0·1 and 0·75%.Arginine, canavanine sulphate, glutamine, histidine, homoserine, isoleucine, leucine, and valine increased weight and prolonged survival, whereas lysine HCl, phenylalanine, threonine, and tryptophan neither promoted growth nor increased survival. Radioactive leucine (¹⁴C(U)) was incorporated into the protein fraction of the larval body and exuviae indicating that it took part in protein synthesis. This seems to be the first report in insects where peptide or protein synthesis occurred from single amino acids in sucrose.     

Rôle of phagostimulants of cotton leaves in the feeding behaviour of Spodoptera littoralis

Petroleum ether extract of cotton leaves was the most attractive to the hatched larvae of Spodoptera littoralis, and it remained so even after removal of the chlorophyll and other pigments. Steam distillation of this filtrate gave a volatile oil which also proved highly attractive to the larvae. In this fraction, 12 components were identified by thin-layer chromatography. Of these components, α-terpineol, citronellol and α-pinene were the most attractive, whereas humulene and linalool were less attractive. The remaining non-volatile lipid fraction was also attractive to the larva. In this fraction the unsaponifiable matter contained the attractive ingredients. This fraction proved to be a hydrocarbon. The infrared spectrum and nuclear magnetic resonance showed only typical hydrocarbon bonds.     

Rôle of labelled dietary fatty acids and acetate in phospholipids during the metamorphosis of Pieris brassicae

The incorporation of labelled dietary palmitic, linoleic, and linolenic acids into neutral (NL) and phospholipids (PL) during the metamorphosis of Pieris brassicae was studied, and the ability of the fat body to incorporate acetate into PL determined. Thirty-three per cent of total lipid in early fifth instar larvae (minus haemolymph) is PL, while the corresponding value in female 4-day pupae is 13·0 per cent and in the fat body of 4-day pupae 6·3 per cent. Incorporation of label into PL was studied more closely and in all cases the label was recovered from phosphatidylcholine (PTC) and phosphatidylethanolamine (PTE). The label from palmitate was also found in sphingomyelin and possibly phosphatidylserine. Specific activity of PL in the case of palmitic and linolenic acids was greatest in late fifth instar larvae. In early fifth instar larvae on palmitic acid-1-¹⁴C 39·0 per cent of label was in PTC, 52·8 per cent in PTE, and 2·0 per cent in sphingomyelin. In late fifth instar 45·0 per cent was in PTC, 45·5 per cent in PTE, and 6·5 per cent in sphingomyelin, while in 4-day female pupae 45·2 per cent was in PTC, 41·3 per cent in PTE, and 13·5 per cent in sphingomyelin. The label from linolenic acid only varied a little from early fifth instar to 4-day pupae, 51·8 per cent being in PTC and 48·2 per cent in PTE in early fifth instar larvae. The label from linoleic acid is incorporated in fat body PL almost exclusively in PTC and PTE, 55·8 and 43·2 per cent respectively in 4-day female pupae. Injected acetate is distributed after 1 hr between PTC (58·6 per cent), PTE (24·4 per cent), and sphingomyelin (17·0 per cent). It was concluded that the polyunsaturated acids are proportionately more common in PTE than in other PL types, and that the fatty acids of sphingomyelin are mainly those that the insect is capable of synthesizing from acetate. Palmitic acid is desaturated by Pieris to palmitoleic acid and the latter possibly utilized in PTE to compensate for a deficiency of linolenic acid in the artificial diet. No saturation of linoleic or linolenic acid was found. The rates of PL and NL synthesis during development and the rôle of the investigated fatty acids in the biosynthesis of PL are discussed.     

Rôle of eyes,optic lobes,and pars intercerebralis in locomotory and stridulatory circadian rhythms of Teleogryllus commodus

Locomotory and stridulatory activity rhythms of male crickets (Teleogryllus commodus) were assayed simultaneously following various experimental procedures. These included (a) severing the pathways between the ocelli and the brain, between the ommatidia and the optic lobes, or between the optic lobes and the brain, and (b) RF cauterization of the pars intercerebralis. The results indicate that (1) light-dark cycles which entrain both rhythms are perceived by the compound eyes and not by the ocelli; (2) loss of connexion between the brain and the optic lobes leads to arrhythmicity in both behaviours, but a single optic lobe can maintain rhythmicity; (3) absence of neurosecretory cells in the pars intercerebralis is correlated with loss of stridulatory activity and arrhythmicity in locomotory behaviour. It is suggested that the pars intercerebralis serves as a site of coupling between a circadian pacemaker and various overt behaviours. However, intermediate control by the pars intercerebralis is assumed to be exerted via channels that can be either hormonal or purely neuronal in nature.     

Cryptic species and systematics of the hynobiid salamanders of the Liua–Pseudohynobius complex: Molecular and phylogenetic perspectives

Using mitochondrial DNA sequencing and allozyme electrophoresis, we examined 18 populations of the Liua–Pseudohynobius complex, endemic to China. Based on their phylogenetic affiliation and exhibited fixed allelic differences, the complex comprises at least six species, two of which are previously unknown cryptic species. The complex is clearly divided into two groups, genus Liua including Liua shihi and Liua tsinpaensis, and genus Pseudohynobius including Pseudohynobius flavomaculatus, Pseudohynobius shuichengensis and the two new species. The previously often used genus name Ranodon is inappropriate, because the type species of the genus, Ranodon sibricus, is distantly related to this complex. The species diversity among Chinese hynobiid salamanders are far from being recognized and further effort should be directed at extensive field collection in central and western China.     

Growth indices — Their rôle in understanding the growth,structure and distribution of Australian vegetation

Summary Growth indices, relating the relative growth of the photosynthetic canopy to light, temperature, moisture and soil nutrients, are described. Monthly values of these growth indices are multiplied, together with the foliage projective cover of the canopy, to give an estimate of the net photosynthetic index of the photosynthetic canopy.An exponentially-increasing respiration index adjusts for the loss of photosynthates by respiration in stems and roots, thus allowing for an estimate of a Current Annual Growth Index and a Total Growth Index, at maturity.A translocation index enables the partitioning of photosynthates between tops and roots to be estimated.These growth indices are examined in relation to the structure, growth and distribution of Australian woody vegetation.Dedicated to Prof. M. Evenari, in appreciation of his stimulation to physiological ecology in mediterranean-type and arid-zone ecosystems     

Phonolic components of the primary cell wall and their possible rôle in the hormonal regulation of growth

The insoluble cell wall polymers of cultured spinach cells contained esterified ferulic acid at 2–5 mg g^-1 dry weight. Gibberellic acid (GA₃, 10^-11–10^-6 M) promoted the expansion of these cells and simultaneoulsy suppressed peroxidase secretion, reduced the activity of cellular phenylanine ammonia-lyase and favoured the accumulation of wall-esterified ferulate and of extracellular soluble phenolic aglycones. When growth was prevented with 0·7 M sorbitol, GA₃ still evoked the phenolic and peroxidase effects. It is suggested that peroxidase restricts growth by rigidifying the cell wall in two ways: (a) covalently by catalysing the conversion of feruloyl side-chains into diferuloyl cross-links and (b) non-covalently by catalysing the conversion of soluble phenolics into hydrophobic quinones (or polymers). GA₃ is hypothesised to prevent this rigidification by inhibiting peroxidase secretion.Abbreviations A ₂₈ absorbance at 280 nm - a _1cnt ^1% absorptivity coefficient - 2,4-D 2,4-dichlorophenoxyacetic acid - EtOAc ethylacetate - GA₃ gibberellic acid - mol wt molecular weight - PAL phenylalanine ammonia-lyase - PCV packed cell volume - sh shoulder or inflection - TLC thin-layer chromatography - UV ultra-violet - wavelength - IAA indoleacetic acid     

Early successional mechanisms in the rocky intertidal: the rôle of direct and indirect interactions

Indirect interactions during succession have received relatively little attention compared with direct interactions. The direct and indirect interactions among barnacles, algae, and herbivores in a rocky intertidal boulder field were evaluated. A factorial experimental design manipulating barnacle and limpet densities on cleared plots was employed. Barnacle density and percent cover of alage were monitored fortnightly for 5 months. The removal of a fine algal mat by herbivores led to higher recruitment of barnacles. The herbivores also prevented the establishment of algae in the absence of barnacles. The barnacles provided a refuge from herbivores for the algae by inhibiting the grazing activities of the limpets. In the absence of herbivores, the barnacles did not have a detectable effect on the algae which grew in thick mats. Through direct and indirect interactions, both barnacles and herbivores may have negatively affected their own performance. This suggests that indirect interactions may be important ecologically, but they need not always feed back positively for a species or group of species.     

The rôle of vitamins in plant development

The Botanical Review -