APHID BEHAVIOUR ON HEALTHY AND ON YELLOWS-VIRUS-INFECTED SUGAR BEET

Myzus persicae Sulz., M. ascalonicus Doncaster, Aphis fabae Scop, and Aulacorthum solani Kalt., when caged on sugar-beet leaves in the glasshouse preferred yellows-virus-infected leaves to healthy ones; they chose those with the most severe symptoms on which they bred more rapidly and lived longer than on green leaves. M. persicae behaved similarly on whole plants in the glasshouse. The previous host influenced the aphid's preference. Differences between the multiplication rates of aphids on healthy plants of inbred sugar-beet varieties were eliminated or reversed by infection with yellows virus.
Spraying healthy plants with either sugar solutions or hydrolysate of casein increased the multiplication rate of M. persicae , but much less than did virus infection.     

Three new genera and five new species of misophrioid copepods (Crustacea) from anchialine caves on Indo-West Pacific and North Atlantic Islands

Hydra lirosoma sp. nov. is a small, hermaphroditic species possessing broad holotrichous isorhiza nematocysts. The spherical embryo and cobbled embryotheca set it apart from similar species. Hydras with broad holotrichous isorhizas form a distinct cluster of species, but one which was not explicitly represented in the three genera ( Pelmatohydra, Hydra and Chlorohydra ) recognized by Schulze (1917, Archiv für Biontologie, 4(2 ): 29). Schulze failed to recognize this group because of the small number of species known at that time. The hydras that are known now fit naturally into four clusters of species termed, in this paper, the oligactis, vulgaris, viridissima, and braueri groups.     

Modification of the Induction of Photosynthesis in Wheat by Glyphosate, an Inhibitor of Amino Acid Metabolism

Ireland, C. R., Pcrcival, M. P. and Baker, N. R. 1986. Modificationof the induction of photosynthesis in wheat by glyphosate, aninhibitor of amino acid metabolism.—J. exp. Bot. 37: 299–308 The effect of the herbicide glyphosate, an inhibitor of aminoacid metabolism, upon the kinetics of induction of photosynthesiswas investigated in wheat leaves. After treatment with a commercialpreparation of glyphosate the induction period for both photosyntheticcarbon assimilation and chlorophyll fluorescence emission wasincreased approximately by 50% after 2 d and by 100%) after5 d. The quenching of chlorophyll fluorescence became a slowerprocess and the S-M transient was diminished. In the steady-stateneither the rate of carbon fixation nor the level of fluorescenceemission were altered. The changes in induction kinetics precededthe occurrence of visible leaf damage. The fluorescence emissionwas analysed by a technique which estimates the redox stateof the PS2 primary electron acceptor, Q, and the photochemicaland non-photochemical components of fluorescence quenching.Glyphosate produced no fundamental change in the relationshipbetween the steady-state values of these parameters until thetime when extensive leaf damage occurred. Thus there was nodirect effect of glyphosate on the capacity for light captureor on the rate of photosynthetic electron transport. This wasconfirmed by the absence of any effect on the quantum efficiencyof oxygen evolution. The slower rate of fluorescence quenchingduring induction is attributed to a slower generation of thetrans-thylakoid pH. It is proposed that glyphosate affects photosyntheticinduction kinetics by an indirect modification of carbon metabolismwhich limits photosynthetic rate during this phase. The possibilityof screening for rapid effects of non-photosynthetic herbicides,such as glyphosate, by monitoring the kinetics of photosyntheticinduction, is raised. Key words: Photosynthesis, induction, glyphosate (N-phosphonomethyl-glycine), wheat (Triticum aestivum L.)     

The kinetics of photoinhibition of the photosynthetic apparatus in pea chloroplasts

Abstract The kinetics of a range of chlorophyll fluorescence parameters, non-cyclic electron transport and the capacity of the thylakoids to bind Atrazine were examined during photoinhibition treatment of intact pea chloroplasts. Parameters of fluorescence induction of chloroplasts in the presence and absence of 3-(3,4-dichlorophenyl)-1,1-dimethyl urea at 20 °C and at 77 K were determined. The contributions of photochemical and non-photochemical quenching processes to the loss of fluorescence during photoinhibitory treatment were assessed. Two distinct phases of photoinhibitory damage were observed. During the initial 5 min period of exposure to light the minimal fluorescence level (F_o) increased, whilst the maximal fluorescence level (F_P) decreased, both coupled and uncoupled non-cyclic electron transport to methyl viologen decreased and the ability to bind Atrazine to the thylakoids decreased. Fluorescence analyses demonstrated that during this period thylakoids were becoming increasingly less efficient at generating and maintaining a transmembrane proton electrochemical gradient. Photoinhibitory damage that occurred at later times between 5 and 20 min was of a very different nature. Both F_o and F_P declined, a loss of coupled and uncoupled non-cyclic electron transport was observed together with a loss of the capacity to photo-oxidize water. However, no further loss of Atrazine-binding was associated with such changes. A consistent decrease in the quantum yield of non-cyclic electron transport was also observed throughout photoinhibition treatment. The possibility of two distinct mechanisms of photoinhibitory damage to the photosynthetic apparatus is discussed.     

An analysis of anemotactic flight in female moths stimulated by host odour and comparison with the males' response to sex pheromone

ABSTRACT. The flight pattern of mated female navel orangeworm moths, Amyelois transitella (Walker), responding to odour from potential larval hosts is zigzagging upwind flight. However, at times these moths are capable of flying nearly directly upwind towards the odour source (track angles near 0). This response indicates that these females are capable of very accurate anemotactic control of their heading or course angle, since small angular errors in this measure would translate into larger deviations from direct upwind flight. Males of this species exhibit flight patterns similar to those of females, including track angles clustered about 0 when flying upwind to a source of the female-produced pheromone, but under these experimental conditions they flew with a higher average airspeed than the females. When females lose contact with an odour plume they initiate a well-defined programme of cross-wind counterturning or casting, which may normally increase their chances of retrieving contact with that plume when the wind direction shifts. The resultant track angles of females increase significantly by 0.8 s after plume loss, indicating that the female has initiated changes in both her course angle and airspeed. By 1 s after plume loss the females' track angles are no longer unimodally distributed about 0, but are bimodally distributed about -90 and +90. Males responded more rapidly to the loss of a pheromone plume, demonstrating a significant change in track angle 0.4 s after plume loss. Overall, female and male A.transitella exhibited remarkably similar anemotactic flight manoeuvres during upwind flight to odour sources as well as after plume loss.     

Human Albinism and Animal Models of Albinism

Ten phenotypic forms of oculocutaneous albinism (OCA) and four forms of ocular albinism (OA) have been identified in man. All have optic neuronal decussation defects at the optic chiasm. Thus any proposed animal model for these disorders must share optic neuronal decussation defects in addition to hypopigmentation. Three, tyrosinase-negative (ty-neg), yellow mutant (ym), and platinum (pt), OCA appear to be allelic in humans. Two, ty-neg and pt, OCA appear to be analogous to c-locus mutants c/c and c^p/c^p in mice, but no homologue is known in mice for ym OCA. Tyrosinase-positive (ty-pos) OCA, which is nonallelic with ty-neg OCA, shares many morphological and biochemical features with pink-eyed mice. Chediak-Higashi syndrome (CHS) and Hermansky-Pudlak syndrome (HPS) appear to be due to genes acting extrinsic to the melanin pathway. CHS is homologous with beige in mice. HPS was investigated in northwestern Puerto Rico, where it affects approximately 1 in 2,000 persons. Approximately 68% of 37 deceased HPS patients died from sequelae of ceroid storage disease, restrictive lung disease between ages 35 and 46 years (43%), and granulomatous colitis (8%) or hemorrhage (16%). The most accurate and consistent diagnostic feature of HPS is lack of platelet dense bodies. HPS patients with ceroid storage disease had high urinary levels of long-chain isoprenoid alcohols, dolichols, similar to that seen in the neuronal-ceroid lipofuscinoses (Batten disease). Dolichols are constituents of lysosomes, and their elevation in HPS suggests that this syndrome carries a lysosomal defect. There is no degradative pathway for ceroid and dolichols, which are eliminated by exocytosis. The exocytic process is thought to involve a thioendoproteinase. Pale-ear mice have been proposed as a model for HPS; their platelets lack dense bodies, and they are depigmented. Leupeptin, a thioendoproteinase inhibitor, administered to 100-day-old pale-eared and black wild-type C57 mice for 10 days resulted in the accumulation of ceroid in tissues in the same pattern as that in HPS, but granulomas of gut or fibrosis of lungs were not seen. Determinations of homology between mice and men at the molecular level is now possible with the isolation of mouse tyrosinase by Yamamoto et al. and isolation by Kwon et al. of human tyrosinase mapping at the c-locus in mice.     

Effects of previous diet and frequency of feeding on development of larval damselflies

SUMMARY. 1. Food availability during instar F-3 affected duration of instar F-3 of larval Ischnura vertiealis (Say) maintained in the laboratory but did not affect the increase in head width at the moult to instar F-2.
2. Food availability during instar F-2 altered both duration in instar F-2 and weight per unit head width of newly moulted F-l larvae, but not the increase in head width at the moult to instar F-1.
3. Food availability during instar F-3 had no effect on instar duration, weight per unit head width, or increase in head width of F-2 larvae at the moult to instar F-l.
4. Survival of larval Coenagrion resolution (Hagen) reared in the laboratory was dependent on mean number of Daphnia offered per day. In addition, larvae fed less frequently, but on the same mean number of Daphnia per day. had lower survival rates than larvae fed more frequently.     

Rare Mollusca from the Lower Devonian Hunsrück Slate of southern Germany

Only ten gastropods have been recovered and a single hyolith found in the radiographic study of the Hunsrück fauna. Four gastropods are interpreted as retaining soft parts: the radula may be identified in one and perhaps the liver and digestive organs in the others. These gastropods may have moved into the area on floating vegetation. The hyolith probably lived on the bottom. Soft parts are present within its shell, but they are not readily interpreted. A tentacular mass anterior to a possible mantle cavity is present, with the bulk of the shell being filled by enigmatic tissue. ▭ Gastropoda, Hyolitha, soft parts, radula, pyritization.     

The logseries distribution and Mountford's similarity index as a basis for the study of stream benthic community structure

SUMMARY. 1. Of the various approaches to studying species-abundance patterns in aquatic ecosystems (particularly streams) the logseries distribution is the most appropriate. The distribution parameter, α, is readily estimated and goodness-of-fit of the model to the data can be estimated.
2. A method exists which uses a to calculate an index of similarity from which cluster dendrograms can be constructed and the clusters tested for significant differences. Assumptions and calculations are presented.
3. Procedures are illustrated, with examples from Idaho streams, and approaches to interpreting the results are included.
4. Studies of stream macro invertebrates can fulfill the assumptions of the logseries distribution but cannot meet those of commonly used diversity indices.