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Studies on the ecology of Amblyomma marmoreum Koch 1844 (Acarnia: Ixodidae).

In the Eastern Cape Province of South Africa, larvae and nymphs of Ablyomma marmoreum Koch occur in habitats in which there is tree cover and herbaceous ground cover. Immatures of A. marmoreum are parasitic on reptiles, birds, and mammals. Adults occur only on reptiles. The major host for all stages is the moutain tortoise (Geochelone pardalis), and in the home areas of tortoises the density of ticks is high. Larvae are active in late summer and autumn. The rate of feeding is temperature-dependent, and some larvae which attach on tortoises in late autumn do not complete feeding until the following spring. Nymphs which occur in the home area of a tortoise become active in response to CO2 in early spring. Adults, and nymphs which occur outside the home area of a tortoise, become active in summer in response to rising temperatures. In nymphs which feed in spring, and hence develop into adults in midsummer, the life cycle is completed in 1 year. In nymphs which fed in midsummer, the life cycle is completed in 2 years.

Animals↗

[Aggregation behavior of Blattela germanica].

1. The adult males of the German cockroach Blattella germanica are less strongly aggregated in their resting period than the adult females; they seldom stay below the common hiding place. This tendency decreases in the course of a day.--2. The nymphs aggregate in the first days of their lives below the hiding places of the adults where they had left the oöthecae. Later the nymphs seek hiding places that are better adapted to their body size. An olfactory stimulus (aggregation pheromone) which is going out from the adult induces the nymphs to go back again to the adults in the course of a day. This tendency decreases more when the nymphs become older. At the same time the number of nymphs which are absent from hiding places increases.--3. A positive chemotactic and a positive thigmotactic reaction are responsible for this behaviour of the cockroaches. A phototactic negative reaction is less important.

Activity Cycles↗

[Identification of species of Hyalomma asiaticum group (Ixodidae) in areas of their sympatry based on immature stages].

Morphological characters of immature stages of three closely related tick species, Hyalomma asiaticum Schulze et Schlottke, 1929, H. dromedarii Koch, 1844 and H. schulzei Olenev, 1931, collected mainly in areas of their sympatry (Fig. 1) were investigated. The larvae and nymphs of these three species were collected in Egypt, Iran, Turkmenistan, Uzbekistan, Afghanistan and Tadjikistan: 159 larvae and 137 nymphs of H. asiaticum from 12 localities; 78 larvae and 167 nymphs of H. dromedarii from 5 localities; 30 larvae and 6 nymphs of H. schulzei from one locality. Both qualitative morphological features and measured character (in mkm) were used to discriminate these species. Main discriminant characters for larvae. H. asiaticum (Fig. 3). Scutum: length < 246, width < 389; base of capitulum: width < 158, dorsally hexagonal, apices of lateral projections directed forward; palpae (II and III segments): length < 106, width < 42; hypostome: length < 87, width < 25; the spur of coxa I small, equilateral triangular; patella: length < 154. H. dromedarii (Fig. 4). Scutum: length > 236, width > 379; base of capitulum: width > 158, dorsally almost triangular, apices of lateral projections directed laterally or backward; palpae: length > 110, width < 46; hypostome: length > 87, width < 26; the spur of coxa I large, isosceles triangular; patella: length > 115. H. schulzei (Fig. 5). Scutum: length > 249, width > 407; base of capitulum: width > 162, dorsally hexagonal, apices of lateral projections directed forward; palpae: length > 114, width > 44; hypostome: length > 89, width > 28; the spur of coxa I large, isosceles triangular; patella: length > 164. Main discriminant characters for nymphs: H. asiaticum (Fig. 3). Scutum: small, width < 650, length and width subequal, posterior margin widely rounded, lateral incisions weakly developed; spiracular plates with distinct, pointed dorsal projection, marginal row of perforations distant from the base of dorsal projection, submarginal row with a gap; base of capitulum: lateral projections situated in posterior half of capitulum; palpae (II segment) short and narrow; hypostome short and narrow, width < 69; pore of coxae I-III present. H. dromedarii (Fig. 4). Scutum: large, width > 650, length shorter than width, posterior margin widely rounded, lateral incisions moderately developed; spiracular plates: with distinct and wide dorsal projection, marginal row of perforations distant from the base of dorsal projection, submarginal row present, without gap; base of capitulum: lateral projections situated in the middle part of capitulum; palpae long and narrow; hypostome long and wide, width > 69; coxal pore lacking. H. schulzei (Fig. 5). Scutum: small, width < 630, length larger than width, posterior margin narrow rounded, lateral incisions weakly developed; spiracular plates: with weakly developed dorsal projections, marginal row of perforation situated just behind the base of dorsal projection, submarginal row with a gap; base capitulum: lateral projections situated in posterior half of capitulum; palpae short and wide; hypostome long and narrow, width < 73; coxal pore lacking.

Afghanistan↗

[Differentiation of closely related species Hyalomma anatolicum and H. excavatum (Acari: Ixodidae) based on a study of all life cycle stages, throughout entire geographical range].

Species status is stated for Hyalomma anatolicum and H. excavatum, based on numerous material from the territory of their distribution. The differentiation of species is recovered for all stages of the life cycle. Diagnosis of Hyalomma anatolicum. Female: small tick--length of scutum commonly less than 2 mm; width of scutum commonly less than 1.9 mm; color of scutum, gnathosoma and coxae light, yellowish- or reddish-brown; whitish enameled pigment on scutum absent; posterolateral ledges of scutum weakly expressed or absent; cervical and lateral grooves more shallow (than in H. excavatum) (fig. 1); setae of scutum, alloscutum, sternal setae and ventromedian setae of second article of palpae more tapering to the apex, narrow rounded or acute (fig. 2, 1, 2, 5, 8). Male: small tick--length of conscutum, as a rule, less than 4 mm; width of scutum, as a rule, less than 2.3 mm; shape of conscutum marrow oval (fig. 3), widest in the midlevel; color of conscutum, anal shields, gnathosoma and coxae light, yellowish- or reddish-brown; whitish enameled pigment on conscutum absent; caudal depression with less dense and more large punctuations (than in H. excavatum); ridges lateral to caudal field less high and sharp (than in H. excavatum); posteromedian groove separated from parma by contiguous punctuations or smooth non high area; setae of conscutum conus-like, more sharpening (fig. 4, 1-3); posterior dorsal margin of gnathosoma straight or slightly concave (fig. 4, 8); segments of leg IV not swallowed. Nymph: large tick (see description). Scutum more narrow. Dorsal tale of spiracular plates clear expressed, marginal perforations distant from margin of spiracular plates at the base of tale (fig. 5, 3); anterolateral side of basis capituli approximately equal to half of gnathosoma width; ventrally lateral projections of gnathosoma situated in posterior half of capitulum base (fig. 5, 4, 5). Hypostome more longer and narrow (fig. 5, 5). Larva: large tick (see description). Diagnosis of Hyalomma excavatum. Female: large tick--length of scutum commonly more than 2 mm; width of scutum commonly more than 1.9 mm; color of scutum, gnathosoma and coxae dark, reddish- or black-brown; whitish enameled pigment commonly present; posterolateral ledges of scutum clearly expressed; cervical and lateral grooves more dipper (than in H. anatolicum) (fig. 7). Setae of scutum, alloscutum, sternal setae and ventromedian setae of second article of palpae more stick-like, more widely obtuse (fig. 8, 1-5). Male: large tick--length of conscutum more than 4 mm; width of scutum more than 2.3 mm; shape of conscutum wide oval (fig. 9), widest in posterior half of length; color of conscutum, anal shields, gnathosoma and coxae dark, reddish- or black-brown; whitish enameled pigment often present; caudal depression with more dense and more small punctuations (than in H. anatolicum); ridges lateral to caudal field more high and sharp (than in H. anatolicum); posteromedian groove separated from parma by strong elevations fused with paraparmal festoons; setae of conscutum more obtuse, often stick-like (fig. 10, 1, 2); posterior dorsal margin of gnathosoma straight or lightly concave. (fig. 10, 3); segments of leg IV swallowed. Nymph: small tick (see description). Scutum more wide. Dorsal tale of spiracular plates weakly expressed, marginal perforations not distant from margin of spiracular plates at the base of tale (fig. 11, 3); anterolateral side of basis capituli clearly shorter than half of gnathosoma width; ventrally lateral projections situated in the middle of or anterior half of capitulum base (fig. 11, 4, 5). Hypostome more shorter and wider (fig. 5, 5). Larva: small tick (see description). Established taxonomical independence of H. anatolicum and H. excavatum is confirmed by several criteria: external morphology (see diagnoses); morphometrical data (see diagnoses and fig. 12, 13); size inversion: larva and nymph of H. anatolicum are large, but females and males are small; while H. excavatum vise versa--larva and nymph are small, but adults--large; host specialization of immature stages: larvae and nymphs of H. anatolicum, as rule, parasitize larger mammals (cattle, camels), while immature stages of H. excavatum parasitize smaller mammals (rodents, hares); presence of sympatry areas: almost entire area of H. excavatum include in area of H. anatolicum and cattle help to mix its populations.

Africa↗

[Susceptibility of Ornithodoros papillipes (Argasidae) ticks to the rickettsia Coxiella burnetii].

A definition of susceptibility of an arthropod to an infectious or invasional agent is given. The susceptibility means a capacity of the arthropod for infection in a result of which the agent either completes a part of its life cycle in the organism of its invertebrate host or reproduces repeatedly in the organs and tissues of its internal medium causing or not causing a noticeable damage. On the model of the tick O. papillipes and Q. fever agent there were shown differences in the resistance of arthropods to Rickettsiae depending on the developmental phase of the invertebrate host. Under otherwise equal conditions the susceptibility of nymphs of O. papillipes to C. burnetii was in nymph II 146 times, in nymph I 280 times and in larvae 50 000 times less than in nymph IV. It has been established that nymphs I, II, and IV engorge blood only 2.5, 14 and 50 times more respectively than larvae. It shows that the success of infection depends to a larger extent on the degree of susceptibility of an arthropod to a corresponding agent than on the quantity of engorged infected blood. The formula of estimation of agent concentration necessary for successful infection of 50 per cent of ticks is given.

Animals↗

Immature Ixodes scapularis (Acari: Ixodidae) parasitizing lizards from the southeastern U.S.A.

Preserved museum specimens of 13 lizard and 3 snake species common in the southeastern U.S.A. were examined for immature Ixodes scapularis Say ticks. Five Eumeces and 4 Ophisaurus lizard species yielded an infestation prevalence of 17.8% for species of Eumeces and 29.0% for species of Ophisaurus. Mean intensity of larvae and nymphs was 7.1 and 2.7, respectively, for species of Eumeces, and 6.3 and 1.4, respectively, for species of Ophisaurus. Collection dates of the lizards ranged from January through December, but most were collected from March through October. The maximum number of immatures found on a single specimen was 193 larvae and 11 nymphs on a specimen of Eumeces and 75 larvae and 7 nymphs on a specimen of Ophisaurus. For species of Eumeces, 75.2% of all nymphs observed were attached in the shoulder area. Larvae were most abundant on the rear legs (53.3%), followed by the front legs (26.3%) and shoulders (12.9%). Larvae and nymphs on species of Ophisaurus were found almost exclusively in the lateral groove area (84.0% and 94.4%, respectively). Three other lizard species (Anolis carolinensis, Sceloporus undulatus, Scincella lateralis) had only a few ticks or none. A fourth species, Cnemidophorus sexlineatus, hosted a total of 3 larvae on 3 specimens (infestation prevalence, 10.7%). Three snake species (Diadophis punctatus, Virginia striatula, Crotalus adamanteus) had none.

Animals↗

Transmission of the Lyme disease spirochete, Borrelia garinii, between infected and uninfected immature Ixodes persulcatus during cofeeding on mice.

The ixodid tick, Ixodes persulcatus, serves as a vector for the Lyme disease spirochete, Borrelia garinii, in Japan. Transmission of the spirochete from infected nymphs to uninfected larvae during their cofeeding on mice was studied under laboratory conditions. Using feeding chambers, infected nymphs and uninfected larvae were allowed to cofeed on heads of normal BALB/c mice. In another group of mice, we separately exposed nymphs to the head and larvae to the back. The resultant engorged larvae were reared and the molted nymphs were examined for spirochetes. Spirochetal infections were found only in ticks that had fed together with infected ticks. The data strongly suggest that spirochetes can migrate from infected feeding ticks to their uninfected neighbors by way of host skin. Moreover, nymphs that had become infected through the cofeeding process could transmit spirochetes to mice.

Animals↗

Lyme disease: self-regulation and pathogen invasion.

Ecological interactions underlying the epidemic of Lyme disease involve a spirochete, a tick (with larval, nymph and adult stages), and two (or more) vertebrate hosts. Juvenile ticks ordinarily feed on mice; adult ticks feed on deer. Mice acquire the spirochete from infected nymphs and then pass the infection to larvae of the next tick generation. Lyme disease may result when a human is inadvertently bitten by an infectious nymph. Our model of the Lyme phenomenon counts the total number of ticks in each stage, the numbers of infected ticks by stage, and the number of infected mice. We fix the total population sizes of deer and mice, assume the ticks self-regulate, and solve the homogeneous-mixing case for equilibrium abundances. A local stability analysis identifies a condition where extinction of the spirochete is stable. Reversing this condition implies that the spirochete can invade the system of ticks and vertebrate hosts. When the spirochete can invade, a positive equilibrium number of infected organisms is locally stable. Spirochete invasion is promoted by a sufficient density of mice suffering low mortality, high susceptibility to infection in both mice and ticks, a high attack rate of ticks on mice, a high density of larval ticks, and low mortality among tick nymphs. Low mouse mortality allows the frequency of infection among nymphs to approach an individual tick's susceptibility when feeding on an infected mouse.

Animals↗

Resistance in cattle against Rhipicephalus appendiculatus with an assessment of cross-resistance to R. pulchellus (Acari: Ixodidae).

A comparison of the yield of engorged nymphs of Rhipicephalus appendiculatus and R. pulchellus was carried out between cattle highly resistant to R. appendiculatus but susceptible to R. pulchellus, and cattle and rabbits susceptible to both species. Resistant cattle yielded fewer and smaller R. appendiculatus nymphs than either susceptible cattle or rabbits. More nymphs of both tick species dropped from susceptible cattle but no differences were detected in the mean weight of engorged R. pulchellus nymphs fed on R. appendiculatus-resistant and susceptible cattle, although resistant animals yielded more nymphs of R. pulchellus than of R. appendiculatus. An acute inflammatory reaction, accompanied by intense pruritus and grooming, was observed in the ears of the resistant cattle infested with R. appendiculatus, but no reaction was detected in the opposite ears where R. pulchellus was feeding. The low cross-resistance between these two closely related tick species suggests that different antigens may be involved in the development of resistance in cattle to different tick species.

Animals↗

Water vapour uptake from subsaturated atmospheres by engorged immature ixodid ticks.

Contrary to current opinion, fully engorged and detached larvae and nymphs of some ixodid ticks consistently take up substantial amounts of atmospheric water vapour and thereby display their regulative capacity for maintaining water balance in subsaturated air. Net uptake of vapour generally begins some days after detachment and the capability persists until shortly after initiation of apolysis, a period which in diapausing specimens may extend up to several months. This was shown for Ixodes ricinus, Haemaphysalis punctata, and the North American I. dammini. Apparently, some other engorged ixodid immatures fail to exhibit net vapour uptake, as was shown for both larvae and nymphs of Dermacentor marginatus and nymphs of Hyalomma anatolicum excavatum. But there is some evidence for engorged nymphs of D. marginatus that active uptake of vapour does occur, masked by spiracular transpiration. Net uptake of vapour is apparently not possible during the pharate phases. In I. ricinus both teneral nymphs and adults are capable of achieving net water gains by active vapour uptake on the first day following ecdysis. There is new evidence from fully engorged I. ricinus immatures for the decisive role of agranular alveoli in the production of the salivary secretion involved in vapour uptake.

Absorption↗

The development of Babesia (Theileria) equi (Laveran, 1901) in the gut and the haemolymph of the vector ticks, Hyalomma species.

The development of the piroplasm Babesia equi was studied by light microscopy in the gut and the haemolymph of three different Hyalomma species during and after the nymphs had engorged on parasitaemic horses. The stock of B. equi used was isolated from a horse imported from Turkmenistan (CIS) in 1991. The existence of gamogony was identified by the occurrence of gamonts and gametes in the gut contents of the nymphs at between 3 and 4 days after infestation of the nymphs, before the ticks dropped off the experimentally infected horses. Zygotes and kinetes were observed in the intestinal cells from day 4 until day 7 after infestation i.e. 2 days prior to engorgement until repletion of the nymphs. Simultaneously, kinetes could also be seen in the haemolymph of engorged nymphs. The morphology and the sequence of the developmental stages of B. equi identified in the gut and the haemolymph of the vector ticks were identical in all three Hyalomma species. They resembled typical developmental stages of bovine Theileria species. Because of the close similarity of the developmental cycle of B. equi in Hyalomma species to the life cycle of Theileria species and due to the differences to the other Babesia species, a discussion about classifying B. equi into the family of Theileriidae now seems to be justified.

Animals↗

Toxicological studies on the long-term effects of heavy metals (Hg, Cd, Pb) in soil on the development of Aiolopus thalassinus (Fabr.) (Saltatoria: Acrididae).

Long-term effects of soil treated with 0.12-12 ppm HgCl2, 2-100 ppm CdCl2 and 25-500 ppm PbCl2 on the development, reproductive capacity and viability of Aiolopus thalassinus (Fabr.) (grasshoppers) during two successive generations were studied. The hatching rate of nymphs developed from eggs laid in treated soil was significantly reduced. Mercury was the most effective in reducing the hatching rate followed by cadmium and lead. The newly hatched nymphs, which developed in the heavy-metal-treated soil, were transferred to and reared in separate cages in order that toxicological effects could be followed through the next two generations without any further treatment. No significant increase was observed in percent mortality during both the F1 and F2 nymphal stages resulting from Hg, Cd and Pb treatment. The nymphs were more tolerant than the eggs and adults to the cumulative effect of heavy metals. The mean durations of the F1 and F2 nymphal stages were prolonged in all Hg and Cd treatments, but such a prolongation in the Pb treatments was found only in F1 nymphs, those developed from the two highest soil PbCl2 concentrations (250 and 500 ppm). The adult fresh weight of the F1 and F2 generations was significantly low in the case of the Hg and Cd treatments. The lifespan of the F1 and F2 adults developed from eggs laid in Hg-, Cd- and Pb-treated soil was significantly shortened and thus the number of egg pods was reduced in comparison with the control. The hatchability of nymphs developed from eggs laid by the F1 generation was significantly lower than that of the untreated control. No significant decrease in the hatching rate was found for the eggs laid by the F2 generation, except at the highest soil concentrations of the three metals. The metal content of eggs laid by the F1 generation increased significantly with increasing soil concentrations of the three metals. In the F2 generation eggs the heavy metal content was reduced in all cases; this indicates a dilution of the metal concentration in successive generations if no further exposure takes place.

Animals↗

Influence of the nutritional state of Triatoma infestans over the insecticidal activity of DDT.

1. The influence of nutritional state over topical insecticidal activity of DDT in nymph II of Triatoma infestans was analyzed. 2. DDT LD50 for starved nymph II was more than 150 micrograms/insect, while for nymph II fed to repletion on artificial feeder, was 0.79(0.50-3.13) micrograms/insect and a similar result was obtained for nymph II fed on pigeons (1.09(0.36-7.55) micrograms/insect). 3. A very slow penetration rate of 14C-DDT was obtained in non fed insects (4.4% penetrated 46 hr after treatment) in correspondence with 0% of mortality. 8.5% of 14C-DDT was not recovered from the cuticle 2 hr after topication of fed nymph in correspondence with a 100% of mortality at 24 hr.

Animal Nutritional Physiological Phenomena↗

Hormonal control of body-color polymorphism in Locusta migratoria: interaction between

The effects of injection of [His(7)]-corazonin and juvenile hormone (JH) III on the body color in L. migratoria were investigated using albino and normal (pigmented) nymphs. Most albino nymphs turned green in the fourth instar if injected with JH III during the last 2 days of the previous instar. When albino third instar nymphs injected with 10 pmol of [His(7)]-corazonin on different days were treated with 100 µg of JH III on day 3.5, they developed various body colors in the following nymphal instar: those injected with [His(7)]-corazonin during the first 2 days developed very dark green or black color, whereas some of those injected after this period turned green and their legs and ventral side of the body were variously pigmented, the coloration being similar to green solitary individuals often found in the field. Field-collected brown solitary nymphs injected with 1 nmol of [His(7)]-corazonin and kept individually, turned reddish without any black spots in the following nymphal instar when the ecdysis occurred within 1 day after injection. Injection of [His(7)]-corazonin 2 days before the following ecdysis induced black patterns on an orange background color, the coloration characteristic of gregarious forms. Similar injections into field-collected green solitary nymphs also induced black patterns but the rest of their body remained green. These results may indicate that the temporal changes in the hemolymph titers of [His(7)]-corazonin and JH play an important role in the control of body-color polymorphism in this locust.

Journal Article↗

Absence of insect juvenile hormones in the American dog tick, Dermacentor variabilis (Say) (Acari:Ixodidae), and in Ornithodoros parkeri Cooley (Acari:Argasidae).

Synganglia, salivary gland, midgut, ovary, fat body and muscle alone and in combination from the ixodid tick, Dermacentor variabilis (Say), or the argasid tick, Ornithodoros parkeri Cooley, were incubated in vitro in separate experiments with L-[methyl-(3)H]methionine and farnesoic acid or with [1-(14)C]acetate. Life stages examined in D. variabilis were 3 and 72 h old (after ecdysis) unfed nymphs, partially fed nymphs (18 and 72 h after attachment to the host), fully engorged nymphs (2 d after detachment from host), 3 and 72 h old (after eclosion) unfed females, partially fed unmated females (12-168 h after attachment to host) and mated replete females (2 d after detachment from the host). Those from O. parkeri were third and fourth stadium nymphs and female O. parkeri, 1-2 d after detachment. Corpora allata from Diploptera punctata, Periplaneta americana and Gromphadorina portentosa were used as positive controls in these experiments. No farnesol, methyl farnesoate, JH I, JH II, JH III, or JHIII bisepoxide was detected by radio HPLC from any tick analysis while JH III, methyl farnesoate, and farnesol were detected in the positive controls. To examine further for the presence of a tick, insect-juvenilizing agent, Galleria pupal-cuticle bioassays were conducted on lipid extracts from 10 and 15 d old eggs, unfed larvae (1-5 d after ecdysis), unfed nymphs (1-7 d after ecdysis), and partially fed, unmated female adults (completed slow feeding phase) of D. variabilis. Whole body extracts of fourth stadium D. punctata and JH III standard were used as positive controls. No juvenilizing activity in any of the tick extracts could be detected. Electron impact, gas chromatography-mass spectrometry of hemolymph extracts from fed, virgin (forcibly detached 7 d after attachment) and mated, replete (allowed to drop naturally) D. variabilis and fully engorged (1-2 d after detachment) O. parkeri females also failed to identify the common insect juvenile hormones. The same procedures were successful in the identification of JH III in hemolymph of fourth stadium D. punctata. Last stadium nymphal (female) O. parkeri implanted with synganglia from second nymphal instars underwent normal eclosion to the adult. The above studies in toto suggest that D. variabilis and O. parkeri do not have the ability to make the common insect juvenile hormones, and these juvenile hormones do not regulate tick metamorphosis or reproduction as hypothesized in the literature.

Journal Article↗

Detection of four Borrelia burgdorferi genospecies and first report of human granulocytic ehrlichiosis agent in Ixodes ricinus ticks collected in central Italy.

The presence of Borrelia burgdorferi s.l. and of Ehrlichia phagocytophila group was sought by PCR in Ixodes ricinus collected in a protected area of central Italy. Nymphs (n = 1475, gathered in 295 pools of 5 nymphs each) and adult ticks (n = 28) were examined. B. burgdorferi s.l. was detected in 13.8% of the nymph pools; of these, 63.4% were infected by B. valaisiana, 26.8% by B. afzelii, 7.3% by B. garinii, and 2.5% by B. burgdorferi s.s. Only a single adult male tick proved to host B. afzelii. The agent of human granulocytic ehrlichiosis (HGE) was detected in 2.7% of the nymph pools. Two HGE agent-positive nymph pools were also found to be positive for B. garinii and for B. afzelii, respectively. This is the first report from central Italy of the finding of the HGE agent in ticks.

Animals↗

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 degrees 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.

Animals↗

Changes of zeatin riboside content in rice plants due to infestation by Nilaparvata lugens (Homoptera: Delphacidae).

The effect of Nilaparvata lugens (Stål) (Homoptera: Delphacidae), infestation on the content of zeatin ribosides (ZR) in rice plants was investigated with enzyme-linked immunosorbent assay. Hydroponics experiments were conducted on 'Zhendao 2' rice, in which plants were subjected to N. lugens infestation at three nonhopperburn-causing densities (15, 30, and 60 nymphs per hill) for 2, 4, 6, and 8 d and at one hopperburn-causing density (240 nymphs per hill) for 2, 4, and 6 d, respectively. When rice plants were infested at the nonhopperburn-causing densities, ZR content in leaves varied significantly with the infestation density. Compared with the control plants, ZR content in rice leaves decreased significantly after infestation by 60 nymphs per hill for 2 d, but it tended to increase due to prolonged infestation at all the nonhopperburn-causing densities. In contrast, ZR content in rice roots significantly reduced after the plants being infested at the density of 15 nymphs for 2 d and at all densities for prolonged duration, except for the plants infested by 60 nymphs for 6 and 8 d, in which the ZR content increased or did not change significantly. However, infestation at the hopperburn-causing density caused significant reduction in ZR content in rice roots, regardless of infestation duration, and in rice leaves from the plants subjected to 2-d infestation. These results are discussed in relation to the possible physiological reaction of rice plants to N. lugens infestation and the resultant severe damage or hopperburn.

Adenosine↗