Effects of ectoparasites on the Sand Martin Riparia riparia nestlings

The effects of ectoparasites on the body mass of Sand Martin Riparia riparia nestlings were experimentally tested. Chicks from nests treated with a pesticide to kill arthropod ectoparasites were heavier than chicks from control nests, indicating that ectoparasitism may be a cost for Sand Martins.     

The pathogenicity determinant of Citrus tristeza virus causing the seedling yellows syndrome maps at the 3'-terminal region of the viral genome

Citrus tristeza virus (CTV) (genus Closterovirus , family Closteroviridae ) causes some of the more important viral diseases of citrus worldwide. The ability to map disease-inducing determinants of CTV is needed to develop better diagnostic and disease control procedures. A distinctive phenotype of some isolates of CTV is the ability to induce seedling yellows (SY) in sour orange, lemon and grapefruit seedlings. In Florida, the decline isolate of CTV, T36, induces SY, whereas a widely distributed mild isolate, T30, does not. To delimit the viral sequences associated with the SY syndrome, we created a number of T36/T30 hybrids by substituting T30 sequences into different regions of the 3' half of the genome of an infectious cDNA of T36. Eleven T36/T30 hybrids replicated in Nicotiana benthamiana protoplasts. Five of these hybrids formed viable virions that were mechanically transmitted to Citrus macrophylla , a permissive host for CTV. All induced systemic infections, similar to that of the parental T36 clone. Tissues from these C. macrophylla source plants were then used to graft inoculate sour orange and grapefruit seedlings. Inoculation with three of the T30/T36 hybrid constructs induced SY symptoms identical to those of T36; however, two hybrids with T30 substitutions in the p23-3' nontranslated region (NTR) (nucleotides 18 394–19 296) failed to induce SY. Sour orange seedlings infected with a recombinant non-SY p23-3' NTR hybrid also remained symptomless when challenged with the parental virus (T36), demonstrating the potential feasibility of using engineered constructs of CTV to mitigate disease.     

Sex pheromone blend discrimination in two races and hybrids of the European corn borer moth, Ostrinia nubilalis

Abstract. The response specificity of males of two races, and hybrids, of the European corn borer moth, to a large series of doses/ratios of E- and Z11-14:OAc, was determined in a sustained-flight tunnel. For both races an area of peak response was determined, which included the natural ratio eliciting peak levels of source contact, and other treatments eliciting response profiles over the behavioural sequence not significantly different from the peak. Consistent with studies on other moth species response specificity was controlled by two threshold effects, one affecting locking-on to odour plumes of lower doses and off-ratios containing lower proportions of the E or Z isomer than the natural blend, and the other resulting in arrestment of upwind flight to higher doses and off-ratios containing higher proportions of the E or Z isomer man the natural blend. A comparison of the size of the areas of peak response showed that males of the univoltine Z race (UZ) using a 3:97 E:Z mix displayed greater specificity and sensitivity than did males of the bivoltine E race (BE) responding to a 99:1 E:Z pheromone mix. At doses higher than those eliciting peak response (<100 μg) response specificity was lower for both races, but especially for the BE race, with increased levels of upwind flight and source contact occurring to off-ratios. Finally, consistent with a previous behaviour/genetic study on this species, F₁ hybrid males displayed peak levels of source contact not only to their natural isomer ratio (65:35 E:Z), but also to an expanded range of doses of ratios ranging from 2% to 98% E.     

Ultrastructural Localization of Acid Phosphatase in Feeding Tokophrya infusionum*

A combined cytochemical and electronmicroscopic study of feeding Tokophrya revealed that it has 2 sources of acid phosphatase. One is from the prey, Tetrahymena, supplying newly formed food vacuoles with large amounts of enzyme. The other source is in Tokophrya itself, the enzyme being found in small vesicles, small dense elongate bodies surrounded by a membrane, or in residue vacuoles. It seems that the 2 former small structures contain insignificantly small amounts of phosphatase; however, large deposits of lead phosphate are present in residue vacuoles, former food vacuoles. Since Tokophrya has no cytopyge these vacuoles are not excreted. On the contrary, when feeding is resumed, they merge with food vacuoles, presumably supplying them with acid phosphatase. Whether this enzyme ultimately is derived from the prey Tetrahymena and persists undegraded in the residue vacuoles, or whether it is synthesized by Tokophrya cannot be determined from present work.     

Effect of Water Stress on Pigment Formation in Quercus Species

The effect of water stress in three Quercus species belongingto different habitats is investigated. Chlorophyll concentrationdecreased in all Quercus species with the greatest decreaseoccurring in Quercus robur. An increase of total carotenoidcontent was observed in Quercus coccifera and Quercus ilex,while in Q. robur water stress effected a carotenoid contentreduction. Anthocyanins increased with decreasing relative watercontent in the three Quercus species, the largest increase occurringin Q. coccifera. A correlation between xerophytic characterand pigment concentration is discussed.     

Alkylation Treatment of the Mexican Axolotl: An Approach to the Isolation of New Mutations

SYNOPSIS. Most of the known mutants of the axolotl were uncoveredby R. R. Humphrey through inbreeding laboratory stock or wildanimals imported from Mexico. All are spontaneous in origin.We believe that chemical mutagenesis may be useful for increasingboth the frequency and variety of new mutations. For our experiments,we have chosen the alkylating agent ethyl methanesulfonate (EMS),because its mode of action is reasonably well understood. Thoughwe were unable to establish a lethal dose of EMS by intraperitonealinjection, we were successful when we administered the compounddirectly in the water. In the weeks immediately after treatment,females administered sublethal doses did not ovulate, exceptin response to large injections of follicle stimulating hormone.Recovery took several months. Treated males showed more normalperformance, in terms of courtship and the number of spermatophoresproduced. At low doses, and short intervals after treatment,embryos from spawnings with treated males survived nearly aswell as controls. Survival reached a minimum about a month afterthe male had been treated, then improved again. This depressionand recovery may be correlated with the stage of sperm maturationat the time of treatment. Treatment of mature sperm from spermatophoresaffected only their ability to fertilize eggs in an artificialinsemination; fertile eggs developed normally. The most promisingprocedure would, therefore, seem to be treatment of the male.Following mutagenesis, we propose that gynogenesis be used toaid in the rapid identification of new recessive mutations.