A new inexpensive suction apparatus for sampling arthropods in grassland

Abstract.

• 1 We describe a new technique for sampling arthropods from grassland and other vegetation, using a modified petrol-driven suction apparatus called a‘Blow & Vac’.
• 2 The new apparatus was tested by comparing its efficiency in extracting arthropods from vegetation with that of a conventional Dietrick, or‘D-Vac’, suction sampler.
• 3 Unimpeded air velocity inside the suction tube was approximately 4 times that of the D-Vac.
• 4 In field trials on semi-natural grasslands, the Blow & Vac caught more individuals of most spider and certain beetle species compared to the D-Vac and approximately equal numbers of Auchenorrhyncha.
• 5 We conclude that the‘Blow & Vac’has considerable potential for sampling arthropod populations. Its low cost and weight make it a suitable alternative to the conventional D-Vac apparatus.

     

Citrus abscission and Arabidopsis plant decline in response to 5-chloro-3-methyl-4-nitro-1H-pyrazole are mediated by lipid signalling

The compound 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP) is a pyrazole-derivative that induces abscission selectively in mature citrus (Citrus sinensis) fruit when applied to the canopy and has herbicidal activity on plants when applied to roots. Despite the favourable efficacy of this compound, the mode of action remains unknown. To gain information about the mode of action of CMNP, the effect of application to mature citrus fruit and Arabidopsis thaliana roots was explored. Peel contact was essential for mature fruit abscission in citrus, whereas root drenching was essential for symptom development and plant decline in Arabidopsis. CMNP was identified as an uncoupler in isolated soybean (Glycine max) mitochondria and pea (Pisum sativum) chloroplasts and an inhibitor of alcohol dehydrogenase in citrus peel, but not an inhibitor of protoporphyrinogen IX oxidase. CMNP treatment reduced ATP content in citrus peel and Arabidopsis leaves. Phospholipase A₂ (PLA₂) and lipoxygenase (LOX) activities, and lipid hydroperoxide (LPO) levels increased in flavedo of citrus fruit peel and leaves of Arabidopsis plants treated with CMNP. An inhibitor of PLA₂ activity, aristolochic acid (AT), reduced CMNP-induced increases in PLA₂ and LOX activities and LPO levels in citrus flavedo and Arabidopsis leaves and greatly reduced abscission in citrus and delayed symptoms of plant decline in Arabidopsis. However, AT treatment failed to halt the reduction in ATP content. Reduction in ATP content preceded the increase in PLA₂ and LOX activities, LPO content and the biological response. The results indicate a link between lipid signalling, abscission in citrus and herbicidal damage in Arabidopsis.     

Effects of Sucrose on Petiolar Carbohydrate Accumulation and Photosynthesis in Excised Sinapis Cotyledons

Petioles of Sinapis cotyledons cultured in 6x10^–2 M sucrosein the light increased 28-fold in total carbohydrate contentover a 7-d period compared with an 8-fold increase in petiolesof cotyledons cultured on water. The starch and reducing sugarfractions were the major components of this accumulation. Labelledsucrose applied to the petiole base moved quickly up the petioleand into the main veins of the lamina. Some basipetal redistributionoccurred subsequently and after 24 h radioactivity accumulatedstrongly at the petiole base. Culture in sucrose reduced basalaccumulation and increased acropetal movement of the label. Fixation of ¹⁴CO₂ by petioles remained constant when cotyledonswere cultured in water, whereas in sucrose, fixation fell by50 per cent during the first 2 d. The pattern of inhibitionof fixation matched the pattern of sucrose distribution in thepetiole. Petiolar chlorophyll content remained constant in controlsbut fell rapidly after 4 d culture in sucrose. The results are discussed in relation to the role of petiolarcarbohydrate accumulation in the regulation of CO₂ fixation,primordium development, and senescence in this system.     

An Improved Method for the Isolation of Highly Polymerized Native Deoxyribonucleic Acid from Certain Protozoa*

A relatively simple phenol extraction method, with EDTA as the nuclease inhibitor, is described for the isolation of purified, highly polymerized native DNA from Trichomonas vaginalis, Trichomonas gallinae, and Tritrichomonas foetus; it is applicable also to Tetrahymena pyriformis. RNase Tl, RNase A (Worthington's R), pronase, and α-amylase digestions constitute important steps in obtaining satisfactory yields of DNA. High degree of polymerization of the isolation product was estimated by hyperchromicity at O.D.₂₆₀ after DNase treatment and by CsCl gradient analysis. The double-stranded condition of the DNA samples was estimated by the latter method and by denaturation with NaOH, and the molecular weight by sucrose gradient analysis. Purity of the samples was determined spectrophotometrically and by chemical analyses for protein and glycogen. DNA percent recovery was estimated by the diphenylamine reaction.     

The control of fungal seed–borne diseases by means of a thiram seed soak

A method of soaking seeds in an 0·2% aqueous suspension of thiram for 24 h at 30 °C, which had previously been shown to eradicate infection by several fungi, was tested against a further thirteen seed-borne pathogens. Eleven of these were completely controlled, one was almost completely controlled and one was not adequately controlled by the treatment. The thiram soak treatment was much more effective than dust treatments with fungicides for the control of many internal fungal pathogens. It was also generally more effective and less damaging than hot-water treatment. The ways of applying the method commercially have been investigated and it is being adopted for the treatment of celery, brassicas and red beet.     

Vairimorpha invictae N. Sp. (Microspora: Microsporida), a Parasite of the Red Imported Fire Ant,Solenopsis invicta Buren (Hymenoptera: Formicidae)12

ABSTRACT. Vairimorpha invictae n. sp. infects the red imported fire ant, Solenopsis invicta Buren, in Brazil. The parasite is dimorphic, producing two morphologically distinct types of spores, which develop sequentially in the same fat cells or oenocytes in the fat body. The binucleate free spores develop from disporous sporonts; the uninucleate octospores develop from multinucleate sporonts within a sporophorous vesicle. Infected cells are transformed into large sacs which contain both types of spores in mature adult hosts. Mature free spores are often present by the time the larvae pupate, but mature octospores are found only in adult hosts. Masses of spores may be seen through the intact cuticle by low power phase-contrast microscopy; there are no other physical signs and no behavioral signs of infection. Attempts to transmit the infection in the laboratory failed.     

Encystation of Entamoeba invadens IP-1 Is Induced by Lowering the Osmotic Pressure and Depletion of Nutrients from the Medium1

ABSTRACT. Trophozoites of Entamoeba invadens IP-1 can be induced to encyst in simple solutions composed of semipermeable constituents (buffer, salts, or sugars) provided that their osmotic pressure is in the range of 60–160 mosmol/kg. Optimal yield of mature cysts was obtained when the osmotic pressure of the medium was 110 mosmol/kg. Encystation could be obtained in the absence of serum although higher yields were obtained in its presence. No difference in the yield of mature cysts was found when either dialyzed or full serum was used. High yields of encystation were obtained (>70%) in the presence of 5% serum in solutions of NaCl, KCl, or MgSO₄, suggesting that the mechanism of encystation is not induced via sodium or potassium channels. Cysts were obtained in the presence of 72 mM glucose, indicating that depletion of a carbon source is not the only requirement for encystation. A rapid change in the density of the Entamoeba cells was observed upon transfer of trophozoites (density 1.061–1.073 g/ml) from growth medium to the low osmotic pressure encystation solutions. Within the first 2 min their density decreased (to 1.050 g/ml), but it soon increased, reaching within 30 min a density higher than 1.120 g/ml. As the encystation process continued to completion, the density of the cells gradually decreased, the mature cysts reaching a density of 1.049–1.061 g/ml.     

The Ultrastructure of Spores (Protozoa: Microsporida) from Lophius americanus,the Angler Fish1

ABSTRACT. Spinal and cranial ganglia of American angler fish, Lophius americanus, are often infected with microsporidia. This protozoon elicits the formation of large, spore-filled, hypertrophied host cells, cysts. Previous reports of microsporidia in European lophiids identify the parasite as Spraguea lophii, a genus which has recently been shown to be dimorphic. The spores from L. americanus are monomorphic (2.8 × 1.5 μm) and uninucleate. Each spore contains a polar tube that forms six to nine coils. Spraguea lophii differs from the microsporidium described in L. americanus in several ways. Spraguea lophii has two spore types: a large spore (4.0 × 1.25 μm) containing a diplokaryon and three to four polar tube coils and a smaller uninucleate spore (3.5 × 1.5 μm) with five to six polar tube coils. Because of these major differences, the microsporidium from L. americanus is removed from the genus Spraguea and returned to its original genus, Glugea, as a new species, G. americanus n. sp. Other ultrastructural characteristics of G. americanus are included: the posterior vacuole encloses two distinct membranous structures; one is tubular and resembles a “glomerular tuft” and the second is lamellar and composed of concentric membrane whorls, additionally, the straight or manubroid portion of the polar tube proceeds beyond the posterior vacuole before it turns anteriorly and begins to coil.     

Ultrastructural Study of the Development of Pleistophora schubergi Zwölfer, 1927 (Protozoa,Microsporida) in Larvae of the Spruce Budworm,Choristoneura fumiferana and Its Subsequent Taxonomic Change to the Genus Endoreticulatus

This study demonstrates that Pleistophora schubergi Zwölfer, 1927, a microsporidium originally isolated from the midgut epithelium of Nygmia phaeorrhoea Don (Euproctis chrysorrhoea L.) and Porthetria dispar L., and subsequently reported in several other insects including the spruce budworm, Choristoneura fumiferana (the host used in this investigation), does not belong in the genus Pleistophora Gurley, 1893. Pleistophora schubergi lacks the major features that are characteristic of Pleistophora typicalis, the type species of this genus. A comparison of ultrastructural observations reported for the type species of the genus Pleistophora, P. typicalis, and our observations of P. schubergi revealed significant differences. A thick (0.5 μm) amorphous coat, derived from parasite secretions and deposited external to the parasite plasmalemma, surrounds all developmental stages in P. typicalis. Double membranes, derived from host rough endoplasmic reticulum cisternae encircle the parasite plasmalemma of all developmental stages in P. schubergi. The sporophorous vesicle encases the spores in P. typicalis, and originates from the parasite-secreted coat that is present around meronts. In P. schubergi, the host endoplasmic reticulum cisternae form the envelope that surrounds the meronts. Moreover, the sporophorous vesicle envelope in P. typicalis persists around groups of spores, while in P. schubergi this envelope breaks easily to release the spores in the host cytoplasm. By comparing the characteristics of the microsporidium found in the spruce budworm with those of the recently created polysporous genera that sporulate within a vesicle, we found that P. schubergi does belong in the new genus Endoreticulatus Brooks et al. 1988, and consequently rename it Endoreticulatus schubergi (Zwölfer, 1927) n. comb.