The central nervous tissues of these organisms have proved amenable to both radiolabelled- ligand-binding studies and single-cell electrophysiology of identifiable neurones. Synchronized action potentials in the cercal nerve of the cockroach Periplaneta americana in response to auditory stimuli. Academic Press, London and New York. Large mitochondria with perforated cristae are scattered throughout the cytoplasm. Little is known of the composition of the saliva of the blood-suckers, however.
It then also becomes possible to correlate meaningfully the neuroanatomy of these systems with their learning and memory abilities. The former is totally inactive whereas the latter is capable of stimulating secretion although both the affinity and intrinsic activity are reduced. This chapter examines the diversity of sensillum types and the diversity of transduction mechanisms used by them. The control of hormone and enzyme release will be described in greater detail later. Aspects of Learning and Memory in the cockroach. The final target both of the environmental cues and of the maternal switch mechanisms is the endocrine system of the embryo or young larva. Because of their small size and cryptic habits, a number of thrips species are easy to invade into new areas.
From Smith and Friend, 1971. When set up in control saline salivary glands secrete very slowly 0. The main feature of this control system concerns the transduction of hormonal information arriving at the cell into internal chemical signals which can be recognized by the various effector mechanisms responsible for carrying out the actions of the hormone. Electromyographic recordings in freely moving animals have provided a detailed description of stridulatory patterns in terms of neurophysiological events at the level of individual motor units. Cyclic guanosine monophosphate is totally inactive even though this compound has been identified in various vertebrate tissues Hardman et aL, 1971. The saliva of Hemiptera is by no means a simple secretion: in addition to the usual salivary functions of moistening food and mixing it with hydrolytic enzymes before ingestion, the saliva of phytophagous species plays an important physiochemical role during the mechanical penetration of plant tissues by the piercing and sucking mouthparts and, in accomplishing this task, the saliva may vary in its chemical composition and physical consistency from one moment to the next.
Animals possessing choline oxidase can, in turn, oxidise it to betaine which can furnish methyl-groups for the synthesis of methionine. Chitin formation and hydrolysis are complex, multi-faceted, interconnected and highly harmonized intracellular and extracellular cascades of biochemical and biophysical transformations. These are all examples of functional conservation in the absence of homeostasis. The mechanisms of insect excretory systems. A number of studies have been made following the change of phospholipid pattern during development but little has been achieved in understanding the metabolic role of the phospholipid.
Other salivary enzymes have also been found. Ion transport across an epithelium usually generates an electrical potential which can be used to analyse the nature of the underlying ionic events. The understanding of caste differentiation has developed rapidly in recent years. They include such techniques as: 1 injecting pharmacological agents of various kinds in animals and observing their influences on learning and memory storage; 2 extraction of brain tissue after learning and comparing its various chemical contents to that existing in such a brain before learning; 3 extracting brain components from trained animals and injecting them in various places in untrained animals and observing effects on learning in the recipient animals; 4 injecting radio-labelled isotopes in untrained animals and observing uptake in various parts of the brain after learning and 5 using autoradiographic techniques in conjunction with electron microscopy to correlate macromolecular changes with various anatomical sites within and between nerve cells before and after a learning procedure. Recent results have provided a reference point for tubule studies for insect physiologists and a unique resource for developmental and genetic analysis of fundamental questions of differentiated cell function. Phosphorylated choline-analogues have been demonstrated in Phorrnia regina larvae when fed on diets containing dimethylethyl- 68 R.
The amounts present show some dependence on the stage of development and, in the case of the housefly, on the amount of choline available to the insect in its diet. The stylets are pushed first one way and then another for periods of up to two hours when Oncopeltus feeds on milkweed-seeds or Dysdercus on cotton seeds Saxena, 1963. So far studies with choline analogues have been carried out almost entirely with the three related species of Diptera. These various feedback mechanisms may be considered as sophisticated devices to ensure that the rapid changes in cell activity produced by hormonal stimuli are orderly and regulated. It is therefore safe to conclude that all the soluble metabolites that occur in the haemolymph, be they salts, amino acids, sugars or the precursors of lipids e.
The first event appears to be an increase in intracellular calcium concentration which may arise through a change in the calcium permeability of the basal plasma membrane. This natural-mode sensing hypothesis: 1 explains why insects should want to sense changes in state rather than absolute state; 2 predicts what specific directions of motion they should sense, and 3 specifies how sensory input from different modalities should be combined. In this way insoluble materials are brought into solution Saxena, 1963 or viscous solutions diluted Miles, 1959b. Control of Secretion-A Model of Hormone Action. In sound emission, the mechanical impedance of the transmitter the vibrating parts of the insect should be low, compared with that of the air the radiation impedance.
Choline is found in almost all living cells, predominantly or exclusively in a combined form, largely in the phospholipid fraction. Thus a large part of labelled cysteine injected into a pentatomid subsequently appeared in the salivary glands and secretions; Hagley 1 969 noted a disproportionately large amount of phenylalanine in the salivary glands of the cercopid Aeneolamia compared with the composition of the haemolymph. Recent progress on the biochemistry and mechanics of sclerotized structures from non-arthropod invertebrates such as mussels, polychaetes and squid suggests that this premise is too simple and needs to be more closely scrutinized. The chapter also discusses the generation of lift and thrust, the kinematics of wing motion, stability in flight, and the motor mechanism of flight reflexes. } Lipsitz and McFarlane 1 970 Crone and Bridges 1 963 Fast 1 966 Fast 1 967 Allais et al.