Localization and distribution of catecholaminergic structures in the nervous system of Phocanema decipiens (nematoda)

The nervous system of Phocanema decipiens was examined with both the formaldeyhyde-induced and the glyoxylic acid fluorescence histochemical techniques. Green catecholaminergic structures were observed in 4 cephalic papillary nerves, 2 fibres with varicosities in the nerve ring as well as the ventral nerve cord and a pair of lateral nerves.The papillary nerves, extending from the nerve ring to the lips region, have cell bodies which are located anterior or adjacent to the nerve ring. Cell bodies of the lateral nerves are found within the lateral cord tissue posterior to the nerve ring. Each of these neurons has 3 processes—one joins with the nerve ring, the other merges with the ventral nerve cord and the third ends abruptly within the lateral cord.     

Molting in a parasitic nematode, Phocanema decipiens: The role of water uptake

Davey K. G. 1979. Molting in a parasitic nematode. Phocanema decipiens: the role of water uptake. International Journal for Parasitology9: 121–125. The rate of uptake of ³H₂O increases in Phocanema decipiens between 8 and 13 h after it has been activated by exposure to 37°C in 0.9% Nacl containing juvenile hormone (0.4 μl/ml), while worms incubated in the absence of the hormone show no such increase. The exchange volume of an activated worm is greater than that of an unstimulated worm, but direct measurement by dry weight determination shows that both stimulated and unstimulated worms have a similar water content. The uptake of ³H_O into the excretory cell is more rapid in stimulated worms, although there is no increase in uptake into the pseudoceolomic fluid. Moreover, there is an increase in water content of the excretory cell in activated worms. These observations are best explained by postulating that in an unactivated worm two compartments exist and in only one of these is water freely available for exchange. In an activated worm, the water in both compartments is available for exchange.     

Histopathology of Aedes aegypti (Diptera: Culicidae) larvae parasitized by Reesimermis nielseni (Nematoda: Mermithidae)

Histological observations were made of Aedes aegypti larvae parasitized for 2, 4, and 6 days by Reesimermis nielseni. Little difference was detected between the tissues of uninfected and nematode-parasitized larvae 4 days after infection, at which time most hosts were in the early fourth instar and their fat bodies were well developed containing abundant storage materials. Nematodes grew most rapidly between day 4 and day 6 of parasitism, depleting host metabolites, reducing the fat body and other host storage tissues while accumulating storage material in their trophosomes. Development of host imaginal discs was inhibited during this period. The severity of the nematodes upon host tissues depended upon intensity of infection. Dry weight measurements of nematode and host supported histological observations that the nematode developed most rapidly 4–6 days post-infection, thus causing most serious effects upon the host at that time.     

Fasciola hepatica: A light and electron autoradiographic study of shell-protein and glycogen synthesis by vitelline follicles in tissue slices

The incorporation of tritiated amino acids and monosaccharides by the vitelline cells of F. hepatica slices maintained in vitro was studied by light and electron microscope autoradiography.A “pulse-chase” labeling technique was used with tritiated tyrosine, phenylalanine, leucine, and methionine, of which H³-tyrosine was the most readily incorporated into shell-protein globules of immature vitelline cells. The mechanism of protein synthesis appeared to resemble the GER-Golgi mediated mechanism of vertebrates. Young vitelline cells were the most active in protein synthesis, and they matured considerably during the 60 min chase period. Maturing cells, which were carrying out glycogenesis, incorporated no amino acids.An “accumulation” labeling technique was used with H³-galactose and H³-glucose. Both monosaccharides were readily incorporated into glycogen by vitelline cells which had reached the stage of glycogenesis, but mature cells, which were already packed with glycogen, incorporated little monosaccharide. Labeling appeared in the nurse cells of follicles containing many mature vitelline cells. No evidence was found for the involvement of any cell organelle in glycogenesis, but preformed glycogen may have acted as a “template” for further synthesis.     

Hybridization studies of Haemonchus contortus (rudolphi, 1803) and H. placei (place, 1893) (Nematoda: Trichostrongylidae)

Hybridization experiments between Haemonchus contortus from sheep and H. placei from cattle indicate that the H. placei vulvar morph type and the inability of the eggs to hatch and develop at 11°C were inherited as dominant traits in the hybrids. The size of the third stage larvae was similar to H. placei in hybrids from the mating of male H. placei × female H. contortus while larvae from the reciprocal mating were intermediate in size. Hybrids produced by the mating of thiabendazole resistant female H. contortus × non-resistant male H. placei were also resistant. The F₁ males of the mating between male H. contortus and female H. placei were sterile. Male sterility did not occur in the reciprocal cross until the F₂ generation. Female hybrids from these generations had a low level of fertility when backcrossed to males of either parent species. Cytological studies of the hybrid males indicated that sterility was due to several kinds of meiotic disturbance and that spermatogenesis stopped during metaphase I. The chromosomes in eggs of unfertilized females did not undergo meiosis and polar body formation; instead they increased in number by a process of endomitosis. Unfertilized eggs in the faeces were characterized by uneven cytoplasmic division and abnormal shape. It is proposed that hybrid sterility can lead to the local eradication of one species of Haemonchus by the other. Furthermore, the outcome of which species is eradicated can be influenced by such variables as initial population sizes, climate, and the local ratio of sheep to cattle.     

Fasciola hepatica: A light and electron microscope autoradiographic study of incorporation of monosaccharides into glycogen and glycoprotein

Incorporation of [³H]galactose and [³H]glucose into the parenchyma, tegument, testis, and muscle of Fasciola hepatica slices was studied by lightand electron-microscope autoradiography. “Accumulation” labeling periods of up to 60 min were used.Both monosaccharides were found to be readily incorporated into glycogen in the parenchymal cells and muscle and [³H]glucose entered the glycogen stores of spermatozoa.No evidence was found for the involvement of any particular cell organelle in glycogenesis, but the demonstration of high synthetic activity in parenchymal evaginations to the base of the surface syncytial tegument supports physiological evidence that glucose enters the fluke mainly across the tegument.Ethylene glycol-dehydrated preparations showed that [³H]galactose was incorporated into glycoprotein by Type I tegumental cells, and perhaps also by sperm morulae. The carbohydrate component seems to be added to the tegumental secretions in the vesicular-lamellar region of the Golgi complex.Following the longest periods of incubation, labeling was observed in the tubules connecting the tegumental cells and syncytium, but not in the surface syncytium itself.     

Megagametogenesis in Halophila johnsonii, a threatened seagrass with no known seeds,and the seed-producing Halophila decipiens (Hydrocharitaceae)

Megagametogenesis, the development of a megaspore into an embryo sac, has been identified in the seagrass Halophila johnsonii, a threatened species with no known sexual reproduction or seeds. Megagametogenesis in H. johnsonii was compared with megagametophyte development in Halophila decipiens, a related species known to readily produce viable seeds. In both species, ovules were structurally similar, megaspore mother cells were seen in premeiotic ovules, and linear tetrads and megagametophytes with two to eight nuclei were present in postmeiotic ovules. However, H. decipiens postmeiotic ovules had a chalazal pouch that was absent in the postmeiotic ovules of H. johnsonii. Late-stage H. decipiens ovules also contained embryos, indicating that they had been fertilized, whereas all late-stage H. johnsonii ovules were degrading and showed no signs of fertilization. These observations suggest that meiosis does occur in H. johnsonii megasporocytes, leading to the formation of viable megagametophytes and egg cells that could be fertilized if pollination occurred. Thus, the lack of seed set is due to a lack of pollination rather than any loss of capacity to produce seeds in this species.     

Movement of a non-flagellate spermatozoon: A study of the male gamete of Nematospiroides dubius (Nematoda)

The spermatozoa of Nematospiroides dubius were studied using the scanning electron microscope and time-lapse cinematography. Spermatozoa undergo a profound change in morphology after insemination: they change from an elongate structure, 16–18 μm long, to a more rounded form about 5–10 μm in diameter. Spermatozoa from female worms stuck to, and migrated across a glass surface by the production of pseudopodia, but they adhered more readily to a glass surface coated with egg albumin. The average speed of a sample of six differentiated spermatozoa was 7·3 μm/min. Their locomotion is not considered to be amoeboid but resembles the movement of monopodial neutrophils. A hypothesis for the mechanism of movement is presented, and other possible functions of the pseudopodial region are discussed.     

Inhibition of Rhabditis maupasi (Rhabditidae: Nematoda) maturation and reproduction by factors from the snail host, Helix aspersa

Chemical factor(s) from hemolymph plasma of the snail Helix aspersa inhibit maturation and reproduction of its mantle cavity-inhabiting nematode, Rhabditis maupasi, cultivated in vitro. In liquid cultures, the presence of inhibiting factor(s) interferes with larval development and with differentiation of the reproductive organs in maturing worms. The severity of the inhibition varies directly with concentration of the factor(s). The inhibitor can be separated into two complementary parts: diffusable and nondiffusable. The inhibiting factor(s) is digestible by proteolytic enzymes and precipitates in saturated ammonium sulfate solution, thus indicating its proteinaceous nature. The factor(s) seems to be non-specific since it also inhibits the reproduction of the insect-parasitizing nematode, Neoaplectana glaseri, in vitro.     

Putative neurotransmitters in the annelid central nervous system: Presence of 5-Hydroxytryptamine and octopamine-stimulated adenylate cyclases

1. Annelid (earthworm, Lumbricus terrestris) nervous tissue was analysed for putative neurotransmitter substances using the microdansyl and radiochemical-enzymatic techniques.2. Glutamate, glycine, aspartate, alanine and taurine were the predominant amino acid. 5-Hydroxytrptamine (5-HT) was also demonstrated by the micro-dansyl technique.3. The concentrations of octopamine, dopamine and noradrenaline were 3.6 μg/g, 1.8 μg/g and 0.8 μg/g respectively.4. Earthworm nervous tissue contains both 5-HT- and octopamine-sensitive adenylate cyclases.5. Lysergic acid diethylamide (LSD) in low concentration (1 μM) stimulated adenylate cyclase activity and partially blocked both 5-HT and octopamine.     

Selective Depletion of Dopamine, Octopamine, and 5-Hydroxytryptamine in the Nervous Tissue of the Cockroach (Periplaneta americana)

High-performance liquid chromatography with electrochemical detection was used to measure the concentrations of 3,4-dihydroxyphenylethylamine (dopamine), 5-hydroxytryptamine (5-HT), p-hydroxyphenylethanolamine (octopamine), alpha-methyl-p-tyrosine, and tryptophan in the cerebral ganglia of cockroaches (Periplaneta americana) after peripheral administration of alpha-methyl-p-tyrosine and alpha-methyltryptophan. In addition, the levels of dopamine, 5-HT, octopamine, alpha-methyl-p-tyrosine, and tryptophan were determined after injection of alpha-methyl-p-tyrosine, 6-hydroxydopamine, or 5,7-dihydroxytryptamine directly into the cerebral ganglia by means of microinjection needles. Peripheral administration of alpha-methyl-p-tyrosine (400-1,600 micrograms/insect) caused a reduction in dopamine and 5-HT concentrations in cockroach cerebral ganglia, although the reduction in dopamine concentrations was more pronounced. Peripheral injections of alpha-methyl-p-tyrosine also reduced octopamine levels in the cerebral ganglia. Peripheral injection of alpha-methyltryptophan (400-1,600 micrograms/insect) caused a marked reduction in 5-HT and tryptophan concentrations in cockroach cerebral ganglia without altering dopamine or octopamine concentrations. Central injections of alpha-methyl-p-tyrosine (80 micrograms/insect) reduced dopamine concentrations in the cerebral ganglia. However, neither 6-hydroxydopamine (20 micrograms/insect) nor 5,7-dihydroxytryptamine (20 micrograms/insect) caused reductions in amine levels when applied near or directly into the cerebral ganglia. The results suggest that specific lesions of aminergic neurons in insects by either 6-hydroxydopamine or 5,7-dihydroxytryptamine are impractical. The specific, long-lasting depletion of 5-HT by alpha-methyltryptophan suggests that this chemical may be useful in elucidating the functions of 5-HT in insects.     

Interaction between Neoaplectana carpocapsae (Nematoda: Steinernematidae) and Apanteles militaris (Hymenoptera: Bracondiae), a parasitoid of the armyworm, Pseudaletia unipuncta

The DD-136 strain of Neoaplectana carpocapsae adversely affected the development of immature stages of Apanteles militaris, a gregarious internal parasitoid of the armyworm, Pseudaletia unipuncta. The adverse effect of the nematode-bacterium complex was indirect, i.e., the infection by the nematode killed the host before A. militaris could complete its development. However, if armyworms containing 10- or 11-day-old A. militaris were exposed to dauer juveniles in Petri dishes, 48.1 and 94.4%, respectively, produced normal cocoons. If hosts containing 9- or 10-day-old A. militaris were fed dauer juveniles, 42.6 and 73.4% of the armyworms, respectively, produced A. militaris which formed normal cocoons. Cocoon-spinning A. militaris larvae were infected by the nematode. After cocoon formation was completed, the dauer juveniles could not penetrate the cocoon and infect the pupa. However, pupae in cocoons which had been deliberately cut open at one end became infected. A. militaris adults were infected when exposed to dauer juveniles in Petri dishes. After 3 days of exposure to dauer juveniles, 25.0, 44.2, and 7.0% of the adults in three trials were alive, whereas 100, 100, and 96.7% of the control adults were alive. Examination of dead adults in the nematode treatment showed that 67.6% contained nematodes. N. carpocapsae developed and reproduced in unparasitized armyworms, in armyworms containing 9-day-old A. militaris, and in those from which A. militaris had emerged. Production of dauer juveniles was significantly higher in unparasitized armyworms and in armyworms containing 9-day-old A. militaris than in those from which A. militaris had emerged.     

Mastophorus muris (Nematoda: Spirurina): Ultrastructure of somatic muscle development

Hamada G. S. and Wertheim G. 1978. Mastophorus muris (Nematoda: Spirurina): ultrastructure of somatic muscle development. International Journal for Parasitology8; 405–414. The ultrastructure of the somatic muscle cells of the adult and six developmental stages of Mastophorus were studied. In all stages the cells consisted of a contractile region containing myofibrils separated by dense bands and a noncontractile region with nuclei, mitochondria, glycogen, lipid droplets and vesicles. Two sizes of myofilaments were present. The dense band contained T tubules and sarcoplasmic reticulum, and, in more advanced stages, support filaments, glycogen and dense bodies. The contractile region of the adult muscle cell consisted of several hundred irregularly shaped myofibrils arranged in a random pattern. This pattern of myofibrils was defined as irregular-coelomyarian. The third stage larva had a shallow-coelomyarian myofibril configuration, which changed to coelomyarian in the late third stage through the addition of new myofibrils at the apical contractile border. In the fourth stage larvae, the subdivision of existing myofibrils changed the pattern to irregular-coelomyarian.     

The nervous system of the chicken proventriculus: an immunocytochemical and ultrastructural study

The proventriculus constitutes the glandular region of the chicken stomach. This organ is innervated by two parasympathetic networks, the myenteric and submucous plexus, and here we present a systematic study of this system by immunohistochemistry and electron microscopy. All the neurons and fibres were positive for the neural markers, protein gene product 9.5 and the amidating enzymes. Immunoreactivities for the constitutive neuronal isoform of the enzyme nitric oxide synthase and the vasoactive intestinal peptide were present in neuronal bodies suggesting an intrinsic origin for the similarly immunoreactive fibres found in the proventriculus. On the other hand, immunoreactivity to gastric inhibitory peptide was only found in varicose fibres making contact with the blood vessels and the glandular epithelium, but never in the neuronal somas, suggesting that this substance may be provided by an extrinsic nervous system whose neuronal bodies are located elsewhere. Electron microscopy revealed frequent neuromuscular and neuroepithelial connections in the muscle layers, the wall of the blood vessels and the epithelium. In addition, synapsis-like structures were identified in the proximity of cells belonging to the diffuse endocrine system, providing a new example of neuroendocrine contacts. No positivity was found for antibodies against other neural substances including somatostatin, peptide histidine–isoleucine, peptide tyrosine–tyrosine, neuropeptide tyrosine, bombesin, met-enkephalin, serotonin, substance P, galanin, calcitonin gene-related peptide and S-100 protein.     

Comparative study of the structure of the reproductive system of dwarfish males of Glyphina betulae (Linnaeus, 1758) and Anoecia (Anoecia) corni (Fabricius, 1775) (Hemiptera, Aphididae)

The morphology and ultrastructure of the male reproductive system of dwarfish males of the monoecious aphid species Glyphina betulae (subfamily Thelaxinae) and the heteroecious species Anoecia (Anoecia) corni (subfamily Anoeciinae) are described. The testicular follicle of these species has the form of a single sac, the proximal parts of the vasa deferentia are slightly (G. betulae) or strongly (A. (A.) corni) expanded, the accessory glands are sack-shaped, and in G. betulae asymmetric and strongly elongated, whereas the ejaculatory duct is short.In both species only mature spermatozoa have been found within the testicular follicles, i.e. the consecutive stages of spermatogenesis have not been observed in adult males. Our studies also show that the testicular follicle, vasa deferentia, accessory glands and ejaculatory duct are histologically very simple. They are composed of more-or-less flattened epithelium of a secretory type, and thin muscle fibres. The epithelial cells are rich in rough endoplasmic reticulum, mitochondria and small vacuoles. The vasa deferentia, especially in G. betulae, are filled with an electron-dense secretion which, as was shown by histochemical staining, contains proteins and polysaccharides. We suggest that the maximum secretory activity of these epithelial cells occurs, as does spermatogenesis, during larval stages, so that the short living adult males are immediately ready for copulation as in other aphids with normal-sized males.     

The structure of the egg-shell of gLobodera rostochiensis (Nematoda: Tylenchida)

Perry R. N., Wharton D. A. and Clarke A. J. 1982. The structure of the egg-shell of Globodera rostochiensis (Nematoda: Tyienchida). International Journal for Parasitology12: 481–485. The ultrastructure and histochemistry of the egg-shell of Globodera rostochiensis are described. The eggshell consists of an outer vitelline layer, a chitinous layer and an inner lipid layer. The vitelline layer is not unit membrane-like and has strands of particulate material attached to its outer surface. The chitinous layer is made up of fibres consisting of a chitin microfibril core, surrounded by a protein coat. The lipid layer contains lipoprotein membranes. These vary in number, the most commonly observed pattern being two or three membranes loosely associated with the inner surface of the egg-shell.     

The structure of the egg-shell of Porrocaecum ensicaudatum (Nematoda: Ascaridida)

Wharton D. A. 1979. The structure of the egg-shell of Porrocaecum enslcaudatum (Nematoda: Ascaridida). International Journal for Parasltology9: 127–131. The egg-shell of Porrocaecum ensicaudatum is oval with an opercular plug at either end. The shell consists of three layers: an inner lipid layer, a middle chitinous layer and an outer vitelline layer. The vitelline layer has strands of particulate material attached to its outer surface. The chitinous layer consists of 8.5 nrn fibrils which are made up of a chitin microfibril core surrounded by a protein coat. The fibrils are oriented randomly or in parallel, there being no indication of helicoidal architecture.The chitinous layer varies in thickness to form a pattern of interconnecting ridges on the surface of the egg. This pattern presumably increases the shell's structural strength.