https://web.mit.edu/horvitz/www/assets/publications/sawin2000.pdf

C. elegans Locomotory Rate Is Modulated by the Environment through a Dopaminergic Pathway and by Experience through a Serotonergic Pathway

The egg the exoskeleton growth and moulting the epidermis musculature the nervous system the pseudocoelom the secretory-excretory system the digestive system the reproductive system nematode pathology.

The Structure of Nematodes

Publisher Summary Among animal hormones, juvenile hormone (JH) is distinctive because of its unique structure and the diversity of its effects on insect development and reproduction. This chapter reviews the actions of JH on the fat body, gonads, accessory glands, muscle, and nervous system of adult insects. Whereas the epidermis is a major target of premetamorphic JH action, it has been studied little in adult insects, which generally do not moult. However, since the development of yellow pigmentation that accompanies sexual maturation in adult male locusts is clearly dependent on JH-regulation processes, in which cellular and molecular mechanism are investigated. The rapid recent progress in understanding how ecdysteroids regulate the gene activities has resulted from the opportunities afforded by drosophila melanogaster: mapped and characterized mutants, polytene chromosomes with puffs marking active genes, efficient germ-line transformation. The recognition of two aspects of JH action in the tissues of adult insects is reviewed. A model for understanding some aspects of priming by JH may be found in the action of ecdysteroids, where early genes produce factors needed for the expression of late genes. In structure, thyroxine is very different from JH, but there is considerable resemblance between thyroxine and phenoxyphenoxy carbamate, fenoxycarb. Functionally, there are marked similarities. Thyroxine governs metamorphosis in amphibians, but is remarkably pleiotropic in governing many processes ranging from the maturation of the central nervous system to thermoregulation. The chapter emphasizes the importance of selecting insect systems on the basis of their optimal features for research, rather than historical precedent or economic importance. With selection of appropriate systems and application of the cell and molecular research techniques now available, the elusive problem of JH action should soon yield to enlightenment.

Cellular and Molecular Actions of Juvenile Hormone. II. Roles of Juvenile Hormone in Adult Insects

Summary

1. The process of oosorption in insects is discussed with regard to the chronology of events which occur during resorption of oocytes and the role of their auxiliary cells.



2. A theory of neuroendocrine control of oosorption is put forward, suggesting that cessation of juvenile hormone secretion is the most important factor leading to this degradative process in spite of the fact that oosorption and vitellogenesis can occur simultaneously.



3. The diversity of behavioural, ecological and physiological factors which promote oosorption is discussed with an emphasis on differences and similarities among representatives of major insect groups, and the manner in which oosorption provides an ovipositional strategy.

Oosorption in insects.

temperature-sensitive type II receptor mutant, as well as heat-shock induction experiments, show that the DBL-1 pathway acts during an interval that extends from two to one cell generation before ray neurons are born and begin to differentiate. In a mutant of the AbdominalB class Hox gene egl-5, rays that normally express EGL-5 do not adopt dopaminergic fate and cannot be induced to express DA when DBL-1 is provided by a heat-shock-driven dbl-1 transgene. Therefore, egl-5 is required for making a subset of rays capable of adopting dopaminergic identity, while the function of the DBL-1 pathway signal is to pattern the realization of this capability. SUMMARY

Patterning of dopaminergic neurotransmitter identity among Caenorhabditis elegans ray sensory neurons by a TGFbeta family signaling pathway and a Hox gene.

Mermis nigrescens: physiological relationship with its host, the adult desert locust Schistocerca gregaria.

1. 1. Using polyacrylamide disc electrophoresis, eight soluble protein fractions were demonstrable in measurable amounts within the yolk of Schistocerca gregaria . 2. 2. Female locusts were infected 3 days after their imaginal moult with equal doses of Mermis nigrescens ova and electropherograms of their haemolymph and fat body proteins were compared with a group of uninfected (control) females. Effects of the parasite upon host protein turnover were appraised in relation to the host's gonotropic cycle. 3. 3. The nematode caused only a sporadic depletion of vitellogenic and non-vitellogenic protein fractions before and during the vitellogenesis period of controls (initial 2 weeks' infection). The ability of the terminal oocytes to sequester vitellogenic proteins from the host haemolymph was impaired by the parasite, so vitellogenesis commenced but was not completed in infected hosts. 4. 4. At 3 weeks' infection, haemolymph protein fractions were significantly diminished (cf. controls) by parassitism but were not so depleted 3 days later. Concurrently, terminal and penultimate oocytes of infected locusts were resorbed. 5. 5. Effects of the nematode on the insect's fat body soluble proteins preceded analogous changes in haemolymph protein fractions. Two weeks after infection, ten of seventeen soluble protein fractions were significantly depleted in the fat bodies of infected locusts (cf. controls). Three weeks after infection, only six fat body protein bands were significantly depleted in infected insects (cf. controls) whilst four such protein fractions were present at significantly higher levels than in the controls. 6. 6. The nematode stimulates catabolism and/or suppresses anabolism of proteins by the host fat body, to provide a dietary source of amino acids within the haemolymph. This effect of M. nigrescens parasitism upon protein turnover in the locust is discussed in relation to host vitellogenesis, growth requirements of the developing parasite and possible involvement of the host endocrine system.

Mermithid parasitism, protein turnover and vitellogenesis in the desert locust, Schistocerca gregaria Forskåi.

Adult desert locusts were experimentally infected with a dose of 50 M. nigrescens ova and larval nematodes removed 14, 17, 21 and 24 days afterwards for in vitro radiotracer studies. These nematodes were incubated under controlled conditions either in a nutrient medium or in insect saline, which contained the appropriate 14 C or 3 H-labelled radioisotope. The rate of incorporation of the radioisotope into the proteins of the nematode was measured. The rate of incorporation of 14 C-leucine into proteins was greatest for the 17- day-old larvae and this accorded with the in vivo growth pattern of the nematode. This isotope was incorporated less rapidly into proteins by the 14-, 21 and 24-day- old larvae, which synthesized proteins at approximately the same rates as each other. A non-linear rate of incorporation was manifest for each of the larval stages. Total dry weight and protein determinations showed that the nematode synthesizes relatively large quantities of non-proteinaceous reserves during the third week of infection, whilst proteins are preferentially synthesized between the 21st and 24th days of infection. The 17-day-old nematode larvae were able to incorporate six 14 C-amino acids into proteins to varying degrees. Leucine was incorporated most effectively into nematode proteins, whilst glutamic acid was the least incorporated of the six amino acids. These nematode larvae could not effectively metabolize the 3 H-dipeptide histidyl-leucine and incorporate its component amino acid residues into proteins. Similarly, a preparation of 3 H-haemolymph proteins were not significantly metabolised and incorporated into proteins by the nematode. However, the nematode metabolized and incorporated an exogenous source of 14 C-glucose into proteins at relatively high levels. Incorporation of 14 C-luecine into proteins was seven times more rapid for nematodes incubated in buffered insect saline than for those incubated in a more complete nutrient medium. The dietary requirements of the nematode for protein synthesis were discussed in relation to their associated effects upon the host metabolism and an active transport of dietary amino acids into the nematode was postulated. We wish to thank Dr H. L. Speer and Dr K. K. Nair for their helpful suggestions regarding radioisotope techniques. Thanks are also due to the National Research Council of Canada for providing financial assistance (Grant No. A4679).

Nutritional requirements for protein synthesis during parasitic development of the entomophilic nematode Mermis nigrescens.

Swnmary - Four isolates (= three species) of steinernematids were propagated at 25, 20 and when possible, 15 and 10°C for 2 years, then their capacities for tolerating high temperatures and freezing determined. In all isolates, the temperature at which 50 % of the infective juveniles died (LT50) increased with an increase in maintenance temperarure. Sleinernema riobravis had the highest LT 50 values, Sleinernemafeltiaestrains the lowest, while Sleinernema carpocapsae Ali strain displayed an intermediate degree of tolerance to high temperatures. Tolerance to freezing, as measured by times at which 50 % of the infective juveniles were killed by a -5 oC regime, was diminished at higher maintenance temperatures. The infectiviry of nematodes that survived freezing was at least 90 % that of unfrozen nematodes (controIs) . Two strains of S. feltiae were the most cold tolerant of the four isolates, but their capacities to withstand freezing were diminished by propagation at warmer temperatures. (\) Elsevier ­ ORSTOM

https://horizon.documentation.ird.fr/exl-doc/pleins_textes/fan/010017567.pdf

Effect of propagation temperatures on temperature tolerances of entomopathogenic nematodes

Newly hatched Aedes aegypti larvae were experimentally infected with controlled levels of infection of the mermithid nematode Reesimermis nielseni and the development of the parasite was recorded The nematode increased in length by 18-fold and in width by 16-fold during a relatively short 6- to 8-day parasitic phase Most of the nematode's growth was restricted to the latter half (3 days) of the infective period A cuticularized tube, extending posteriorly from the stoma, was present throughout parasitic development After 3 days infection, the nematode possessed a membrane-bound stichosome containing 16 stichocytes, and a cellular trophosome with storage nutrient granules beginning to accumulate in the intercellular spaces Between 3 and 4 days infection, the parasite probably molted as its growth rate suddenly increased, its stylet was lost, and a caudal appendage acquired The stichosome, trophosome, and genital rudiment continued to develop for the rest of the infective period A discrete granular bo

Roger Gordon

Papers

Mermis nigrescens: physiological relationship with its host, the adult desert locust Schistocerca gregaria.

Mermithid parasitism, protein turnover and vitellogenesis in the desert locust, Schistocerca gregaria Forskåi.

Nutritional requirements for protein synthesis during parasitic development of the entomophilic nematode Mermis nigrescens.

Effect of propagation temperatures on temperature tolerances of entomopathogenic nematodes

Parasitic development of the mermithid nematode Reesimermis nielseni in the larval mosquito Aedes aegypti