Affinity-Purification of Concanavalin A-Binding Ciliary Glycoconjugates of Starved and Feeding Tetrahymena thermophila

Development of mating competency in Tetrahymena thermophila requires starvation for at least 70 min in low ionic strength buffer. Pair formation between conjugating cells is blocked at early stages by the lectin Concanavalin A (Con A). To investigate the role of Con A-binding proteins in this induced cellular change and pairing, and to confirm and extend an earlier study from our laboratory, a method was developed for preparation of Con A-binding proteins from ciliary membrane-rich fractions of T. thermophila. Con A-binding ciliary proteins were prepared from non-starved and starved cells from two wild type strains and a mating mutant, RH179E1. Comparison of these proteins by SDS-PAGE revealed on overall reduction in number of wild-type bands after starvation. In particular, a major band at 28 kDa was present in non-starved cells and absent in starved cells. However, in the mating mutant, no change in banding profile was seen after starvation: the 28 kDa band was present in both non-starved and starved cells. This, Con A-binding ciliary membrane proteins undergo a major change during starvation-induced development of mating competency in wild-type T. thermophila. In contrast, the mutant differed from wild-type in overall composition of its ciliary Con A-binding glycoproteins and in the response of these proteins to starvation, suggesting that it may be deficient in its ability to be initiated by starvation. Our results are consistent with the hypothesis that a change affecting ciliary membrane Con A-binding proteins is essential for the cellular response to mating signals.     

Influence of environmental factors on the wandering phase and pupariation in stable fly, Stomoxys calcitrans, larvae

Abstract. Components of the wandering phase of mature stable fly ( Stomoxys calcitrans L. (Diptera: Muscidae)) larvae were examined. The mean length of the wandering phase was estimated to be 10.6 ± 3.5 h. In a factorial experiment in which wandering larvae were allowed to pupate in media with three levels each of moisture, temperature and light, the mean time to 50% pupariation was delayed and the rate of pupariation was lowest at high moisture levels, but this latter effect was seen only at the moderate light level. Pupae in media with higher moisture contents had significantly higher fresh weights. However, none of the three factors affected dry weight of pupae. A significant interaction was observed between the effects of moisture and temperature on survival; only at highest moisture content and at the highest temperature did a significant decrease in survival occur. In a separate experiment, density was found to have no effect on mean time to 50% pupariation or the rate of pupariation. Puparium formation appeared to be random under a LD 169 h photocycle, showing no apparent circadian rhythm.     

Invasion and development of juveniles of Globodera pallida in hybrids of Solanum vernei x S. tuberosum

Invasion and development of Globodera pallida (Pa 2) were investigated in the susceptible cultivar Pentland Crown and in two Solanum tuberosum S. vernei clones, 8917 b (3) and 12380 abc (2) with respective susceptibilities of 10% and < 1%. The numbers of juveniles per unit length of main root of Pentland Crown and 8917 b (3) did not differ, but the numbers found in the highly resistant clone 12380 abc (2) were significantly lower at all sampling dates except the last. Development of juveniles was substantially retarded in 12380 abc (2) and there was a higher ratio of males to females in both the resistant clones. It is suggested that reduced invasion and establishment can contribute to resistance and tolerance of potatoes to potato cyst-nematode.     

Plasmodium berghei NK65 in the Inbred A/J Mouse: Age Immunity in the Female Retired Breeder A/J Mouse*

SYNOPSIS. Death rates of A/J and CF₁ female mice 4 weeks and 6 months of age were compared after the mice were infected with Plasmodium berghei NK65C deme (population) and NK65RR deme. Death rates were compared also when female A/J retired breeder mice were infected with blood passages 18 and 40 of NK65C. NK65C was found to be less virulent than NK65RR. The 40th blood passage of NK65C was more virulent than the 18th passage, but still not as virulent at the NK65RR deme. A/J retired breeders were clearly more resistant to infection than 4 week old A/J mice, while little difference was found in the different age groups of the CF₁ mice.     

Amplification of tick-borne encephalitis virus infection during co-feeding of ticks

Abstract. Following engorgement of Rhipicephalus appendiculatus larvae on guinea-pigs infected with tick-borne encephalitis (TBE) virus, none of the engorged larvae or emergent nymphs contained detectable infectious virus. However, one of twelve pools, each containing three of the unfed nymphs, was positive when screened by polymerase chain reaction (PCR), indicating a low prevalence of TBE virus infection in the unfed nymphs. After engorgement of the nymphs on four uninfected guinea-pigs, 19/24 (79%) fed nymphs from one guinea-pig and 4/25 (16%) fed nymphs from a second guinea-pig were infected; all the ticks examined from the other two guinea-pigs were uninfected. The results suggest that TBE virus was transmitted from a low proportion of infected nymphs (infected as larvae) to uninfected nymphs as they fed together on an uninfected guinea-pig. Such amplification of the initial infection, at the population level, could play an important role in maintaining TBE virus infections in nature, particularly if there is a low level of vertical transmission from one tick generation to the next.     

Analysis of Mitochondrial DNA Variation as an Approach to Systematic Relationships in the Genus Acanthamoeba1

Classification at the species level has been difficult in the genus Acanthamoeba. The taxonomic designations of a number of strains are in doubt and new approaches to classification are needed. We describe the use of electrophoretic patterns obtained with restriction enzyme digests of mitochondrial DNA as a basis for one new approach. Results from analysis of ten strains of A. castellanii, two of A. polyphaga and one of A. astronyxis are discussed. Examples both of nucleotide sequence diversity and of sequence conservation have been found among strains with the same species designation. Five strains from Europe, North America and New Zealand had identical digestion phenotypes with five enzymes; consequently, very similar nucleotide sequences are predicted. All are pathogenic to humans or mice. The mtDNA sequences of eight remaining strains are predicted to differ from this cluster and, in most cases, from each other at least as much as in sibling species of Paramecium aurelia.     

Transmission of louping ill virus between infected and uninfected ticks co-feeding on mountain hares

Abstract. Most of the data on oral infection of ticks by louping ill virus have been obtained from experiments in which animals were infected by syringe inoculation with infectious material. Using infected ticks to mimic the natural situation, we have demonstrated that louping ill (LI) virus transmission can occur from infected to uninfected Ixodes acinus feeding in close proximity on mountain hares (Lepus timidus). Under these conditions the hares developed either low or undetectable viraemias. Highest prevalence of LI virus infection was observed in recipient nymphs which had fed to repletion between days 3 and 7 post-attachment of virus-infected adults; following engorgement, 56% of nymphs acquired virus. These results demonstrate the efficient transmission of LI virus between co-feeding ticks on naive mountain hares. However, when ticks were allowed to co-feed on virus-immune hares a significant reduction in the frequency of infection was observed. Neither red deer (Cervus elaphus) nor New Zealand White rabbits supported transmission of LI virus. The significance of virus transmission between cofeeding ticks on LI virus epidemiology is discussed.     

Characterization and isolation of DNA microsatellite primers in the spiny dogfish (Squalus acanthias)

The North Atlantic spiny dogfish (Squalus acanthias) population has been declining since the 1980s. Proper management of this population is essential as dogfish are prone to rapid collapse based on the unique biology of this species. We characterized eight microsatellite loci for spiny dogfish to use in determining the genetic structure of this species along the Atlantic coast of the USA.     

Spatial predictability and resource specialization of bees (Hymenoptera: Apoidea) at a superabundant, widespread resource

For reciprocal specialization (coevolution) to occur among floral visitors and their host plants the interactions must be temporally and spatially persistent. However, studies repeatedly have shown that species composition and relative abundance of floral visitors vary dramatically at all spatial and temporal scales. We test the hypothesis that, on average, pollen specialist bee species occur more predictably at their floral hosts than pollen generalist bee species. Taxonomic floral specialization reaches its extreme among species of solitary, pollen-collecting bees, yet few studies have considered how pollen specialization by floral visitors influences their spatial constancy. We test this hypothesis using an unusually diverse bee guild that visits creosote bush (Larrea tridentatd), the most widespread, dominant plant of the warm deserts of North America. Twenty-two strict pollen specialist and 80 + generalist bee species visit Larrea for its floral resources. The sites we sampled were separated by 0.5 to > 1450 km, and spanned three distinct deserts and four vegetation zones. We found that species of Larrea pollen specialist bees occurred at more sites and tended to be more abundant than generalists. Surprisingly, spatial turnover was high for both pollen specialist and generalist bee species at all distances, and species composition of samples from sites 1–5 km apart varied as much as repeat samples made at single sites. Nevertheless, the pattern of bee species turnover was not haphazard. As distance among sites increased faunal similarity of sites decreased. Faunal similarities among sites within 250 km of each other were generally greater than if randomly distributed over all sites (the null model). No single ecological category of species (widespread, localized, Larrea pollen specialist, floral generalist) accounted for this spatial predictability. Evidently, concordant local distribution patterns of many ecologically diverse species contribute to the non-random spatial pattern. The ecological dominance of creosote bush does not confer obvious ecological advantages to its specialist floral visitors. Spatial turnover is comparable to that found for bee guilds from other biogeographic regions of the world and is not therefore limited to those bee species that inhabit highly seasonal climates, such as deserts. Philopatry and differences in bloom predictability among sites are probably more important causes for spatial turnover of bee species than are interspecific competition for nest sites or floral resources.