Natural attachment duration of nymphs of the tick Ixodes uriae (Acari: Ixodidae) on kittiwake Rissa tridactyla nestlings

Daily searches of the plumage of 62 kittiwake (Rissa tridactyla) chicks were carried out for 3 weeks to determine the attachment duration of the tick Ixodes uriae. All ticks recorded were nymphs and their mean duration of attachment was 5.2±1.7 days (n=93). Seventy-four per cent of the ticks survived to engorgement and were assumed to have fed successfully. The mean duration of attachment of successful ticks was 5.8±1.0 days (n=69), significantly longer than that of unsuccessful ticks (3.3±2.1 days, n=24). There was no difference in survival rates to engorgement between ticks attached to feathered and unfeathered parts of the body (78.3 and 79.2%, respectively), but the duration of attachment of successful ticks was significantly longer on unfeathered compared to feathered areas. There were no significant differences in the survival to engorgement or duration of attachment between ticks found on young (c.11 days) and old (>11 days) kittiwake nestlings. The attachment duration was not related to the total number of ticks found on the host or the number of ticks present in the immediate vicinity of the site of attachment. This work provides important data on the parameter of attachment durations of nymphal I. uriae on free-living kittiwakes; the data can be used for incorporation into the application of population modelling.     

Systemic activity of closantel for control of lone star ticks,Amblyomma americanum (L.), on cattle

Cattle were treated once at 5 mg/kg orally or subcutaneously or daily at 0.1–5 mg/kg orally or 0.1–1 mg/kg subcutaneously with closantel, N-[5-chloro-4-[(4-chlorophenyl) cyanomethyl]-2-methylphenyl]-2-hydroxy-3,5-diiodobenzamide, and numbers and weights of engorged females, weights of egg masses and hatch of eggs of lone star ticks,Amblyomma americanum, were recorded.Effectiveness of treatments on reproduction was determined by comparing total estimated larvae (EL) (EL=wt. egg mass×est. % hatch×20000) or ticks from treated cattle with that of ticks from untreated cattle. With certain treatments, we also determined the effect of manure of treated cattle on survival of larvae of the horn fly,Haematobia irritans, or effect on survival and of fecundity of adult horn flies or stable flies,Stomoxys calcitrans, fed on blood from treated animals.The single oral treatment afforded essentially complete control of total EL only of ticks placed on the animal on the day of treatment, while the single subcutaneous treatment afforded >92% control of total EL of ticks placed on animal on treatment day and for 6 weeks posttreatment. Daily treatments of 0.5 mg/kg or greater orally and 0.1 mg/kg or greater subcutaneously afforded essentially complete control of total EL of ticks throughout the treatment period (3–12 weeks) and for 1–7 weeks after treatment was discontinued. An estimated concentration of >9 g/ml of blood was calculated by probit analysis to be necessary to provide >90% control of total EL of lone star ticks; that same concentration also provided >90% control of hatch of eggs laid by treated females. A higher concentration (40 g/ml) was necessary to prevent engorging of the females. No treatments tested were effective against larvae of the horn fly or adult horn flies or stable flies.     

Control of induced infestations of three African multihost tick species with sustained-release ivermectin

The efficacy of ivermectin, released intraruminally from a 28-day-delivery device was evaluated in two titration studies against induced infestations of adultRhipicephalus appendiculatus, R. evertsi andHyalomma truncatum on cattle. Cattle were given a sufficient number of devices to release ivermectin at approximately 20, 40, 60 or 80 g kg^–1 day^–1 at a steady-state rate 7–28 days after administration. Tick mortality was recorded, engorged female ticks were weighed and individually incubated, and reproductive data were recorded to determine a reproductive index for the species at various dose levels. Mortality of male and female ticks compared to that of controls was directly related to the daily dose of ivermectin, as was the number of ticks not engorging. Ticks fed on ivermectin-treated cattle had a smaller mass when engorged and laid smaller egg-masses, both absolutely and as a proportion of engorged mass.The index of reproduction ofR. appendiculatus was reduced by more than 99.9% at 20 g kg^–1 day^–1, and the reproductive indices ofR. evertsi andH. truncatum were reduced by more than 99.9% at dose rates of 40 g kg^–1 day^–1 and above.Practical implications of the application of sustained-release ivermectin for the control of multihost ticks and tick-borne diseases are discussed.     

Does geographic range affect the attractant–aggregation–attachment pheromone of the tropical bont tick, Amblyomma variegatum?

The tropical bont tick, Amblyomma variegatum, transmits heartwater in sub-Saharan Africa and in the Caribbean. This species has a broad geographic distribution, ranging from Madagascar and other islands in the Indian Ocean through most of sub-Saharan Africa, to several islands in the eastern Caribbean Sea. Blood fed male A. variegatum secrete an attraction–aggregation–attachment (AAA) pheromone which, combined with CO₂, excites host finding and formation of feeding clusters of these ticks. However, it is not known whether the composition of the pheromone varies throughout A. variegatums geographic range. Extracts of fed male ticks were examined for phenols and volatile organic acids by gas chromatography and mass spectrometry to determine whether differences occur in the pheromone components of populations of this species across the geographic range (Guadeloupe, Zimbabwe, Zambia and Rwanda). No significant difference in the chemical composition of the pheromone in relation to geographic range was found. No significant differences in rates of attachment in response to native versus foreign extracts were found in on-host attachment tests comparing ticks from two countries, Guadeloupe (Caribbean) and Zimbabwe (African). This finding was confirmed in more detailed studies with ticks from Guadeloupe and four African countries (Kenya, Rwanda, Zambia and Zimbabwe). On-host attachment assays from these countries did not detect consistent differences in response to extracts from different locations.In an olfactometer bioassay, females were not consistently more attracted to extracts from their native locality than from any of the foreign localities.We conclude that despite the widespread distribution of A. variegatum over both hemispheres, no significant differences in pheromone composition or biological responses to male tick pheromone secretions occur.     

Treatment of clothing with a permethrin spray for personal protection against the western black-legged tick,Ixodes pacificus (Acari: Ixodidae)

The synthetic pyrethroid, permethrin, when applied to clothing with a pressurized spray at an application rate estimated previously to be 4 g a.i./cm², was found to be 100% effective for personal protection against all three parasitic stages of the western black-legged tick,Ixodes pacificus Cooley and Kohls. This tick has been implicated as the primary vector of the Lyme disease spirochete (Borrelia burgdorferi) to humans in the far-western United States. Periods of exposure to permethrin-treated cloth as brief as 10 and 45 seconds incapacitated 100% of subadult and adult ticks, respectively, within 1–3 h post-treatment. Under field conditions, permethrin appareatly does not repel questing adult ticks, though 100% of ticks recovered from treated clothing after exposures as brief as 15 seconds were moribund 1 h later.     

The effect of avermectins on feeding,salivary fluid secretion,and fecundity in some ixodid ticks

We tested the effects of the potent acaricides, avermectin B₁a (AVM) and 22,23-dihydroavermectin B₁ (ivermectin; IVM) when injected directly into partially fed and fully engorged female ticks. When injected into small ticks (Amblyomma hebraeum Koch), neither drug (up to 100 g/kg b.w.) inhibited subsequent engorgement nor affected oviposition latency, weight of total egg mass laid nor viability of laid eggs. At higher concentrations (1000 and 5000 g/kg b.w.), AVM and IVM were markedly toxic. When injected into engorged ticks, both drugs increased oviposition latency, and reduced fecundity at about 75–100 g/kg b.w. Vitellogenesis, as assessed by a spectrophotometric assay of the ovaries, was not inhibited. Also at 50–100 g/kg b.w., AVM and IVM caused paralysis of the abdominal dorso-ventral muscles and the leg muscles. Both drugs, at 7 days post-injection, proved detrimental to salivary gland function in both small and large ticks, but had little effect on salivary gland weight. At concentrations which did not inhibit oviposition (20–50 g/kg b.w.) many of the eggs dried out even though they were kept at high RH. We then demonstrated inAmblyomma americanum, Dermacentor andersoni andD. albipictus that removal of egg wax (by extraction with hexane) induced a marked increase in water permeability. IVM neither increased water permeability ofD. andersoni eggs nor diminished the amount of egg wax deposited on the surface of the eggs, when injected posteriorly through the alloscutum. However, injection of IVM, dimethylsulphoxide (vehicle for IVM) or distilled water through the articulation between the capitulum and scutum (anterior injection), did markedly reduce the wax coating and increased egg permeability. We suggest that anterior injection damages Gené's organ and thus causes the latter effects.     

Transmission of Lyme disease spirochetes (Borrelia burgdorferi)

The field and laboratory evidence incriminating nymphalIxodes dammini as the main vectors ofBorrelia burgdorferi is substantial. Furthermore, other members of theIxodes (Ixodes) ricinus complex, includingI. ricinus, I. persulcatus, I. pacificus, andI. scapularis, are competent vectors of the Lyme disease spirochete. Although ticks in other genera are also naturally infected withB. burgdorferi, experimental evidence suggests thatAmblyomma andDermacentor ticks are inefficient vectors of these spirochetes. Current research on the kinetics ofB. burgdorferi growth within ticks demonstrates that Lyme disease spirochetes are dramatically influenced by physiological events during the tick's life-cycle.     

Role of Rusa deer Cervus timorensis russa in the cycle of the cattle tick Boophilus microplus in New Caledonia

Two field experiments were conducted to evaluate the efficiency of Rusa deer in the development of the cattle tick Boophilus microplus in comparison with that of steers in the same pastures and under the same conditions of infestation. No difference was noted between a mixed steer/deer herd and a pure steer or pure deer herd in the infestation pattern of each host, suggesting that attachment to the alternative host is mechanical and not affected by the simultaneous presence of the primary host on the pasture. Deer are capable of producing engorged viable females, with weight and reproductive performances similar to or even better than females fed on steers. For moderate levels (1 million larvae per hectare) and high levels (32 million larvae per hectare) of pasture infestation, tick burdens on steers were not very different (e.g. average 1911 and 2681ticks per m² skin, respectively, on day 24). This may be because of saturation of steer skin sites at the moderate larval dose. Deer harboured 2.7–33 times fewer ticks than steers and produce no engorged females at the moderate larval level and 32 times fewer engorged females than steers at the high larval level. Infestation of deer was dosedependent with averages of 12 and 399ticks per m² skin on day 25 at the moderate and high larval levels, respectively. At a high infestation level of the environment, Rusa deer may contribute, but to a limited extent, to infestation of pastures and, consequently, of cattle. However, their role in sustaining a viable tick population requires further investigation.     

Mating reaction in Saccharomyces cerevisiae

A diffusible sex-specific substance called substance-I (S-I) was isolated from culture filtrate of type strains of the yeast Saccharomyces cerevisiae. The isolated S-I, an oligopeptide, induced sexual cell agglutinability in inducible a type strains and enhanced the agglutinability in constitutive a type strains. The induction of sexual agglutinability was detected in 30 min and reached maximum in 90 min, when 0.2 g/ml of S-I was added to inducible a type cells. The a type-specific factor responsible for sexual cell agglutination, called a type agglutination factor (aAF), was shown to be produced during the induction or the enhancement of agglutinability of a type cells by S-I. The aAF produced in response to S-I was not different in the susceptibility to proteolytic enzymes and disulfide-cleaving agents from those produced constitutively in the absence of S-I.     

Allomonal defence secretions of the American dog tick Dermacentor variabilis (Acari: Ixodidae) promote clustering

The release of the defence secretion from the large wax glands (sensilla sagittiformia) of Dermacentor variabilis ticks modifies the behaviour of other ticks by inducing clustering. A coating of natural tick secretion onto test objects (delipidized ticks, glass beads or filter paper discs) also elicits a clustering response, but a topically applied squalene, its major component, does not have this effect. The clustering response appears to be species specific: D. variabilis cluster on conspecific ticks that secreted but they fail to cluster on Amblyomma americanum or Ixodes scapularis ticks unless coated with secretions from D. variabilis. Volatile components in the defence secretion are involved in recruiting conspecific ticks to those that secreted. When attacked by predatory fire ants, Solenopsis invicta, D. variabilis clustered on individuals that had released the defence secretion. This suggests that the secretion protects ticks from predation by functioning as an alarm pheromone. If confirmed, this is the first report of an alarm pheromone and its glandular source in ticks. The terminology applicable to the integumental glands of ticks is discussed.     

Comparative susceptibility and possible detoxification mechanisms for selected miticides in banks grass mite and two-spotted spider mite (Acari: Tetranychidae)

The susceptibility and possible detoxification mechanisms of the Banks grass mite (BGM), Oligonychus pratensis (Banks), and the two-spotted spider mite (TSM), Tetranychus urticae Koch, to selected miticides were evaluated with and without synergists. BGM was 112-fold more susceptible to the organophosphate dimethoate, and 24-fold more susceptible to both the pyrethroids bifenthrin and -cyhalothrin than TSM. The synergist triphenyl phosphate (TPP) enhanced the toxicities of bifenthrin and -cyhalothrin against BGM by 3.0- and 4.2-fold, respectively, and enhanced the toxicities of bifenthrin, -cyhalothrin, and dimethoate against TSM by 6.2-, 1.9-, and 1.7-fold, respectively. The synergist diethyl maleate (DEM) enhanced the toxicities of bifenthrin and -cyhalothrin against BGM by 2.2- and 2.9- fold, respectively, and enhanced the toxicity of bifenthrin against TSM by 4.1-fold. On the other hand, the synergist piperonyl butoxide (PBO) increased the toxicities of bifenthrin and -cyhalothrin by 6.0- and 2.6-fold, respectively, against BGM, and by 4.5- and 1.9-fold, respectively, against TSM. The significant synergism with these pyrethroids of all three tested synergists (except for DEM with -cyhalothrin against TSM) suggests that esterases, glutathione S-transferases, and cytochrome P450 monooxygenases all play important roles in their detoxification. However, the toxicity of dimethoate was not enhanced by these synergists in either mite species (except for TPP against TSM). Apparently, these metabolic enzymes play less of a role in detoxification of this organophosphate in these mites.     

Biodegradation of beta-cyfluthrin by <Emphasis Type="Italic">Pseudomonas stutzeri</Emphasis> strain S1

-Cyfluthrin [-cyano-4-fluoro-3-phenoxybenzyl-3(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylate] pesticide has been in agricultural use in the recent years for controlling Lepidopteran pests affecting solanaceous crops. The extensive use of synthetic pyrethroids like -cyfluthrin has resulted in wide spread environmental contamination. The purpose of this study was to isolate bacteria from soil and to determine their ability to degrade -cyfluthrin and identify the intermediates in culture broth using spectroscopy. An aerobic bacterium capable of degrading -cyfluthrin was isolated by enrichment culture. The 16S ribosomal DNA sequence of the isolate (strain S1) had 100% identity to the sequence from Pseudomonas stutzeri. Finally products formed during degradation of -cyfluthrin have been identified as -cyano-4-fluoro-3-phenoxybenzyl-3(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylate (M.W. 341); 4-fluoro-3-phenoxy--cyanobenzyl alcohol (M.W. 243) and 3(2,2-dichlorovinyl)-2,2-dimethyl cyclopropanecarboxylic acid (M.W. 208).     

Life Cycle of the Tick Haemaphysalis Leporis-palustris (Acari: Ixodidae) Under Laboratory Conditions

The life cycles of two separate populations (colonies A and B) of the rabbit tick, Haemaphysalis leporis-palustris, were studied under laboratory conditions. Domestic New Zealand rabbits, Oryctolagus cuniculus, and wild rabbits, Sylvilagus brasiliensis, were used as hosts for ticks from colony B and only O. cuniculus rabbits were used as hosts for ticks from colony A. Developmental periods were observed in an incubator at 27±1°C and RH 90±5%. Larvae from colonies A and B fed for 8.0±3.7 days and 8.5±1.3 days, respectively, on O. cuniculus. On S. brasiliensis larvae from colony B fed for 7.2±1.3 days. Nymphs from colony A fed for 8.1±1.4 days on O. cuniculus and nymphs from colony B fed for 8.1±1.0 days on S. brasiliensis. Only one engorged nymph from colony B was recovered from O. cuniculus. Females from colony A fed for 20.9±5.9 days on O. cuniculus and females from colony B fed for 18.6±2.4 days on O. cuniculus and 18.7±3.7 days on S. brasiliensis. Engorged larvae from colony A required 13.7±3.7 days to molt while engorged larvae from colony B required 11.8±3.0 and 11.5±1.8 days to molt, after having fed on O. cuniculus and S. brasiliensis, respectively. Engorged nymphs from colonies A and B required 16.3±1.9 days and 14.7±1.4 days to molt, respectively. Engorged females from colonies A and B required 4–7 and 3–5 days, respectively, to start oviposition. Mean egg incubation periods lasted for 33–34 days. For ticks from colony B, host species accounted for significant differences (p<0.05) in larval and nymphal feeding periods, oviposition weights and CEIs. Significant differences (p<0.05) between the two colonies when ticks fed on O. cuniculus were observed for larval and nymphal feeding and premolt periods, engorged female and oviposition weights and conversion efficiency indexes (CEI). S. brasiliensis were always a more suitable host for H. leporis-palustris than O. cuniculus. Significantly more larvae and nymphs engorged and molted when fed on S. brasiliensis (p<0.001). Females fed S. brasiliensis were more successful to lay fertile eggs and showed the highest engorged and egg mass weights, and the highest CEIs. Data of H. leporis-palustris fed on wild rabbits (one of its natural host species) are reported for the first time.     

Therapeutic and persistent efficacy of a single injection treatment of ivermectin and moxidectin against Boophilus microplus (Acari: Ixodidae) on infested cattle

The effectiveness of a single treatment with either ivermectin or moxidectin was determined by administering a single subcutaneous injection of each endectocide at 200 g per kg body weight to cattle infested with all parasitic developmental stages (adults, nymphs, and larvae) of Boophilus microplus (Canestrini). The percentage reduction in the number of females that reached repletion following treatment (outright kill) was 94.8 and 91.1% for ivermectin and moxidectin, respectively. In addition, the reproductive capacity of the females that did survive to repletion was reduced by >99%, regardless of the endectocide. Based on these two factors, the therapeutic level of control obtained against ticks on the cattle at the time of treatment was 99.0 and 99.1% for ivermectin and moxidectin, respectively. Engorged females recovered from either group of treated cattle weighed 3-times less than untreated females, and the egg masses produced by treated females weighed 5–8-times less than egg masses produced by untreated females. Partitioning of data into three separate 7-d post-treatment intervals allowed for an estimation of the efficacy of each endectocide against each individual parasitic development stage (adult, nymph, and larva). Results indicated that both endectocides were 99.7% effective against ticks that were in either the adult or nymphal stage at the time of treatment. However, the level of control against ticks in the larval stage of development at treatment was significantly lower at 97.9 and 98.4% for ivermectin and moxidectin, respectively. Analysis of the persistent (residual) activity of the two endectocides indicated that neither material provided total protection against larval re-infestation for even 1-wk following treatment. Against larvae infested 1–4 wk following treatment, the level of control with moxidectin ranged from 92.4% (1 wk) to 19.5% (4 wk). These control levels were higher at each weekly interval than for ivermectin, which ranged from 82.4% (1 wk) to 0.0% (4 wk). The potential for the use of these injectable endectocide formulations in the US Boophilus Eradication Program is discussed.This paper reports the results of research only. Mention of a commercial or proprietary product in this paper does not constitute an endorsement by the U.S. Department of Agriculture. In conducting the research described in this report, the investigators adhered to protocol approved by the USDA-ARS Animal Welfare Committee. The protocol is on file at the USDA-ARS, Knipling-Bushland U.S. Livestock Insects Laboratory, Tick Research Unit, Kerrville, TX. The U.S. Governments right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged.This revised version was published online in May 2005 with a corrected cover date.     

Antioxidant and Sensorial Properties of Linden Honey with Dried Apricots

The total phenol (TPh) and flavonoid contents (TFd), and antioxidant and sensorial properties of linden honey (LH) with dried apricots (20, 30, and 40%) were evaluated. TPh increased 4.3 times for LH40 (from 23.96 to 102.87 mg gallic acid equiv./100 g honey), while increase of TFd was slightly lower, ca. 2.9‐fold for LH40 (from 18.11 to 51.72 mg rutin equiv./100 g honey). Based on HPLC analysis, the most dominant phenolic compound was gallic acid (11.14 mg/100 g honey in LH and 42.65 mg/100 g honey in LH40). In three different assays, the antioxidant activity increased with increasing concentration of apricots in honey. The values varied from 13.36 for LH to 7.06 mg/ml for LH40; the values ranged from 189.83 for LH to 11.23 mg/ml for LH40; the RP_0.5 (reducing power) values ranged from 169.00 for LH to 27.60 mg/ml for LH40. Based on the correlation analysis, it is obvious that TPh and TFd were associated with the antioxidant activities of honey samples. A high degree of correlation existed between antioxidant activities of honey samples and TPh (R from 0.945 to 0.996) and TFd (R from 0.805 to 0.934). Obtained scores for individual sensory properties indicated very good quality of honey with dried apricots.     

NMR‐based conformation and dynamics of a tetrasaccharide‐repeating sulfated fucan substituted by different counterions

The sulfated fucan from the sea urchin Lytechinus variegatus is composed of the repetitive sequence [‐3)‐α‐l ‐Fucp‐4( )‐(1‐3)‐α‐l ‐Fucp‐2,4‐di( )‐(1‐3)‐α‐l ‐Fucp‐2( )‐(1‐3)‐α‐l ‐Fucp‐2( )‐(1‐]_n. Conformation (of rings and chains) and dynamics of this tetrasaccharide‐repeating sulfated fucan substituted by Na⁺, Ca²⁺, and Li⁺ as counterions have been examined through experiments of liquid‐state nuclear magnetic resonance spectroscopy. Scalar coupling and nuclear Overhauser effect (NOE)‐based data have confirmed that all composing units occur as ¹C₄ chair conformer regardless of the cation type, unit position within the repeating sequence, and sulfation type. Chain conformation determined by NOE signal pattern assisted by molecular modeling for a theoretical octasaccharide has shown a similar linear 3D structure for the three differently substituted forms. Data derived from spin‐relaxation measurements have indicated a contribution of counterion type to dynamics. The calcium‐based preparation has shown the highest mobility while the sodiated one showed the lowest mobility. The set of results from this work suggests that counterion type can affect the physicochemical properties of the structurally well‐defined sulfated fucan. The counterion effect seems to impact more on the structural mobility than on average conformation of the studied sulfated glycan in solution.     

Adaptation of the rat cardiac proteome in response to intensity‐controlled endurance exercise

Endurance training improves cardiac function and protects against heart disease. The rodent intensity‐controlled running model replicates endurance exercise in humans and can be used to investigate molecular adaptations in the heart. Rats (n = 6, 280 ± 3 g) performed exercise tests to measure their peak oxygen uptake ( ) and training was prescribed at 70–75% for 30 min, 4 days/wk. Hearts were isolated 4 h after a final test and left ventricle proteomes compared to weight‐matched control animals (n = 6, 330 ± 2 g) using differential analysis of 2‐D gels. Proteins were identified by searching MS and MS/MS spectra against Swiss‐Prot using MASCOT (www.matrixscience.com). Average increased 23% (p = 0.008) over the 6‐week regimen and 23 gel spots differed (p<0.05) between exercised and control hearts. Expression of myofibrillar proteins (e.g. α‐myosin heavy chain and cardiac α‐actin) and proteins associated with fatty acid metabolism (e.g. heart fatty acid binding protein, acetyl coenzyme A dehydrogenase and mitochondrial thioesterase‐1) increased. In addition, this work discovered a novel increase in phosphorylation of heat shock protein 20 at serine 16. Previously this modification has been associated with improved cardiomyocyte contractility and protection against apoptosis.     

Ivermectin is not an agonist at a GABA receptor in tick salivary glands

The avermectins, broad-spectrum anti-parasitic agents which are effective against ticks, act principally by stimulating -aminobutyric acid (GABA) receptors directly or indirectly. GABA is known to potentiate dopamine-induced fluid secretion in the salivary glands of female ixodid ticks. We thus tested wheter 10 M ivermectin would have an effect similar to GABA in the isolated salivary gland preparation ofDermacentor andersoni. Ivermectin was not an agonist at this GABA receptor.     

Diversity of the mouse T cell receptor Cγ1 gene: structural analysis in C57BL/Ka

We have isolated an unusual T cell receptor chain cDNA clone (7.1) from a library made from RNA derived from adult thymus of C57BL/Ka mice. This cDNA clone corresponds to the appropriately processed C1 constant region exons preceded by 1.5 kb of J-C1 intron. The 7.1 coding region is extremely homologous to the C1 gene of BALB/c mice, differing at the protein level by a single deletion (alanine 139) and a single substitution. This latter change eliminates the sole N-linked sugar attachment site, providing a basis for strain-specific glycosylation patterns. The J-C1 intronic region contains two DNA segments (termed J1 and J2) that are highly reminiscent of joining (J) segments; both have potentially functional recombination and donor splice sequences flanking an open reading frame. Northern analysis suggests that 7.1 may be derived from a large, variable region-containing precursor.     

Tip-recording from ixodid tick olfactory sensilla: Responses to tick related odours

Summary The tip-recording technique was used to obtain electrophysiological responses from the tarsal olfactory sensilla, md3 and apl, in ixodid ticks,Rhipicephalus appendiculatus andAmblyomma variegatum. Stimuli tested were phenolic compounds, 2,6-dichlorophenol,P-cresol, phenol and salicylaldehyde, reported to act as sex pheromone of various ixodid ticks. Certain cells responded to vapours from cartridges charged with as little as 0.04ng of 2,6-dichlorophenol while at least 200 g of any of the other compounds was required to exert the minimum effect. Response patterns of cells in sexually immature and mature males were similar but response levels were higher among sexually immature males. Vapours fromn-hexane washings of adult and larval ticks or from live virgin females contained potent stimuli which caused response patterns similar to those evoked by 2,6-dichlorophenol. The chemical identity and behavioural significance of those stimuli are still under investigation.