The β-Galactosidase Activity in <Emphasis Type="Italic">Kluyveromyces marxianus</Emphasis> CBS6556 Decreases by High Concentrations of Galactose

In this paper we report on the effect of different concentrations of lactose and galactose in the production of β-galactosidase by Kluyveromyces marxianus CBS6556. The results clearly demonstrate a decrease in enzyme specific activity during cultivation at high concentrations of L-lactose or D-galactose, despite the fact that these carbohydrates are normally used for induction of the β-galactosidase activity. Therefore, maximum induction of β-galactosidase in K. marxianus batch cultures was obtained at low concentrations of the inducer carbohydrates, in the range between 0.5 to 15 mM. Those informations can help to design low cost medium with higher β-galactosidase productivity by K. marxianus cells. Received: 8 August 2001 / Accepted: 15 October 2001     

Neospora caninum in cattle: experimental infection with oocysts can result in exogenous transplacental infection, but not endogenous transplacental infection in the subsequent pregnancy

Whilst it is presumed that infection of pregnant cattle with Neospora caninum oocysts can provoke abortion and is the likely cause of epidemic abortion outbreaks, only two previous experiments have involved inoculation of pregnant cows with oocysts (and only one abortion was provoked in 22 pregnancies). Here, we describe the oral oocyst challenge of 18 cows synchronously bred and inoculated precisely at 70 (n = 6), 120 (n = 6) and 210 (n = 6) days in pregnancy with a nominal dose of 40,000 oocysts. Only one abortion occurred (at the 120 days challenge) which could be definitively ascribed to N. caninum and no transplacental infection (TPI) was detected in any of the other 11 calves born in the 70 and 120 day challenge groups. In contrast, 4/5 live calves born to cattle challenged at 210 days were transplacentally infected. When cows which had transplacentally infected their calves in the first pregnancy were rebred, no TPI occurred. The results show that the timing of challenge influences clinical and parasitological outcomes and that cattle in late pregnancy are exquisitely sensitive to oocyst challenge leading to exogenous TPI and congenitally infected calves. However, cattle which were indisputably systemically infected in their first pregnancy did not induce endogenous TPI in their subsequent pregnancy. This confirms previous results with experimental tachyzoite challenge and suggests that post-natal infection does not lead to persisting infections which can recrudesce in pregnancy.     

Parasitism capacity of Trichogramma pratissolii Querino & Zucchi (Hymenoptera: Trichogrammatidae) on alternative hosts, under different temperatures

The successful use of Trichogramma as biocontrol agent depends on its mass production in laboratory, a fundamental step for any biological control program among other factors. This work investigated the parasitism capacity of Trichogramma pratissolii Querino & Zuchi (Hymenoptera: Trichogrammatidae), a new recorded Trichogramma species, parasitizing eggs of Anagasta kuehniella (Zeller) and Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) under the temperatures of 15, 18, 21, 24, 27, 30 and 33 degree Celsius. Eggs of these hosts were offered to newly emerged females during 24h. This procedure was repeated daily for each female and each temperature up to female death, in order to estimate daily and accumulated parasitism, and female longevity. On both hosts, the daily parasitism decreased as function of the female age. Under all temperatures studied and both hosts the highest rate of parasitism was observed during the first 24h of host exposure, and reached 80% of total parasitism in the 4th and 3rd days when parasitizing A. kuehniella and C. cephalonica, respectively. On both hosts, the highest parasitism rate was observed under temperatures from 21 degree Celsius to 27 degree Celsius. Average longevities of T. pratissolii females deprived of food emerging from A. kuehniella and C. cephalonica lived for 1.0 and 8.9 days when reared at 15 degree Celsius e 33 degree Celsius, respectively. The results indicate that eggs of A. kuehniella and C. cephalonica and temperatures from 21 degree Celsius to 27 degree Celsius were appropriate to rear T. pratissolii.     

EFFECT OF STARVATION ON LIPOPHORIN DENSITY IN FIFTH INSTAR LARVAL Manduca sexta

Lipophorin (Lp) is a major insect lipoprotein and is responsible for lipid transport between organs. In this study, the effect of starvation on Lp properties was analyzed in larval Manduca sexta during the fifth instar. Lp hemolymph concentrations in larvae at days 1 and 2 were around 2–3 mg/ml and at day 3 it increased to 8 mg/ml. When larvae were starved for 24 h, they did not grow, but their body mass and hemolymph volume did not decrease significantly. Differences in Lp densities were observed. In fed larvae, from days 1 to 4, two major Lp populations were found with densities of 1.124 ± 0.002 (high density Lp‐larval₁, HDLp‐L₁) and 1.141 ± 0.002 g/ml (HDLp‐L₂). When larvae were starved for 24 h, only one Lp population was present, with density 1.114 ± 0.001 g/ml (HDLp‐L_s). When larvae were abdominally ligated at day 1 or 2 of fifth instar, only HDLp‐L_s was found after 24 h, indicating that the formation of this HDLp population was not dependent on any factor released by head. On the other hand, larvae that were ligated at day 3 showed the same Lp populations as the fed ones. In 24‐h starved larvae, lipid load in Lp was higher as compared to the fed controls. In 24‐h ligated larvae Lp lipid content increased when ligation was performed on day 1 or 2, but not on day 3. So, different responses to starvation can be observed depending on the developmental phase of the same larval instar.     

A review of the status of the coconut mite, Aceria guerreronis (Acari: Eriophyidae), a major tropical mite pest

The coconut mite (CM), Aceria guerreronis Keifer, has spread to most coconut production areas worldwide and it has been considered one of the most notorious and important pests of coconut fruits in many countries. Although CM has been reported to damage coconuts for over 40 years in the Americas and Africa it continues to cause considerable losses in countries of these continents, and in the last 15 years it has also reached countries from southeast Asia—India and Sri Lanka. Several other countries of southeast Asia are also major coconut producers and the impact by the mite in currently affected areas suggests that the dispersion of CM to these major producers could lead to very heavy losses. Great advances about our knowledge on CM and its control have been achieved, especially in the last decade, after its introduction into Asia. However, much remains to be known to allow the design of efficient strategies to it. This paper brings together information on CM invasive history, distribution, hosts, morphology, biology, dispersal, colonization process, population dynamics, symptoms and injury, estimated losses, sampling techniques, control strategies and new perspectives for its control.     

Efficiency of Phytoseiulus longipes Evans as a control agent of Tetranychus evansi Baker & Pritchard (Acari: Phytoseiidae: Tetranychidae) on screenhouse tomatoes

The spider mite Tetranychus evansi Baker & Pritchard can cause severe damage to tomato crops. The predatory mite Phytoseiulus longipes Evans was recently reported in association with T. evansi in Uruguaiana, Rio Grande do Sul State, Brazil. The objective of the present study was to evaluate the effects of P. longipes on the population of T. evansi on tomatoes under screenhouse condition. The study consisted on four experiments, in each of which 80 potted plantlets were distributed in two plots of 40 plantlets each. Two weeks later, each plantlet of both plots was infested with eight adult females of T. evansi; one week after, four adult females of P. longipes were released onto each plant of one plot. The population levels of T. evansi and the damage caused by these mites were significantly lower (P < 0.05; linear mixed-effect model) in the plots where P. longipes had been released. The results indicate the potential of this predator as a candidate for classical biological control of T. evansi by inoculative releases on tomato plants.     

Biology, thermal requirements and fertility life table of the broad mite Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae) in grape (Vitis vinifera L.) cv. Italia

The mite Polyphagotarsonemus latus (Banks) constitutes one of the main pest of grape crop at the Submédio S?o Francisco Valley. The objective of this work was to study the biology of the broad mite Polyphagotarsonemus latus (Banks), to determine its thermal requirements and its fertility life table in grape (Vitis vinifera L.) cv. Italy. Acclimatized chambers (BOD) were used, adjusted to the temperatures of 18, 22, 25, 28 and 32 degrees C, relative humidity of 65 +/- 10% and alternated light of 12h. Egg-adult period was 3.4 and 6.8 days for males and 3.5 and 7.4 days for females, respectively at 32 degrees C and 18 degrees C. At the temperatures of 18, 25 and 32 degrees C, each female deposited, respectively, 16.5, 44.3 and 13.3 eggs. The stages of egg, larva and pupa and egg-adult period presented, respectively, thermal thresholds of 11.23, 9.45, 12.19, and 9.71 degrees C and thermal constant of 28.51, 14.59, 8.33, and 62.73 degrees-day. The mean duration of one generation (T) was 25.6, 10.8 and 8.2 days, respectively, at the temperatures of 18, 25 and 32 degrees C. The net reproductive rate (R0) at the temperature of 25 degrees C was the highest, corresponding to an increase of 30.12 times at each generation. The intrinsic rate of population increase (rm) was 0.10 (18 degrees C), 0.31 (25 degrees C) and 0.12 (32 degrees C) and the finite ratio of population increase (lambda) was 1.10 (18 degrees C), 1.36 (25 degrees C) and 1.13 (32 degrees C). According to the mean temperature values, P. latus can have 95 and 99 generations/year, respectively, for the municipal districts of Petrolina, PE and Juazeiro, BA.     

Biology and thermal requirements Trichogramma pratissolii Querino & Zucchi (Hymenoptera: Trichogrammatidae) on alternative hosts

The objective of this work was to study the biology and determine the thermal requirements of Trichogramma pratissolii Querino & Zucchi reared on Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) and Corcyra cephalonica Stainton (Lepidoptera: Pyralidae) at 15, 18, 21, 24, 27, 30 and 33 masculineC. The highest percentage of emergence of T. pratissolii was obtained at 27 masculineC on A. kuehniella and from 24 masculineC to 30 masculineC on C. cephalonica. The lower threshold temperature (Tb) and the thermal requirement (K) of T. pratissolii were 12.59 masculineC (Tb) and 122.85 degree-days (K) when reared on A. kuehniella and 11.73 masculineC (Tb) and 139.80 degree-days (K) on C. cephalonica. These results indicate that both A. kuehniella and C. cephalonica are suitable hosts for T. pratissolii mass rearing. The optimal temperature for the immature development and emergence of T. pratissolii on A. kuehniella was 27 masculineC and 24 masculineC to 30 masculineC on C. cephalonica.     

Exploration of the acarine fauna on coconut palm in Brazil with emphasis on Aceria guerreronis (Acari: Eriophyidae) and its natural enemies

Coconut is an important crop in tropical and subtropical regions. Among the mites that infest coconut palms, Aceria guerreronis Keifer is economically the most important. We conducted surveys throughout the coconut growing areas of Brazil. Samples were taken from attached coconuts, leaflets, fallen coconuts and inflorescences of coconut palms in 112 localities aiming to determine the occurrence and the distribution of phytophagous mites, particularly A. guerreronis, and associated natural enemies. Aceria guerreronis was the most abundant phytophagous mite followed by Steneotarsonemus concavuscutum Lofego & Gondim Jr. and Steneotarsonemus furcatus De Leon (Tarsonemidae). Infestation by A. guerreronis was recorded in 87% of the visited localities. About 81% of all predatory mites belonged to the family Phytoseiidae, mainly represented by Neoseiulus paspalivorus De Leon, Neoseiulus baraki Athias-Henriot and Amblyseius largoensis Muma; 12% were Ascidae, mainly Proctolaelaps bickleyi Bram, Proctolaelaps sp nov and Lasioseius subterraneus Chant. Neoseiulus paspalivorus and N. baraki were the most abundant predators on attached coconuts. Ascidae were predominant on fallen coconuts, while A. largoensis was predominant on leaflets; no mites were found on branches of inflorescences. Leaflets harboured higher mite diversity than the attached coconuts. Mite diversity was the highest in the state Pará and on palms surrounded by seasonal forests and Amazonian rain-forests. Neoseiulus paspalivorus, N. baraki and P. bickleyi were identified as the most promising predators of A. guerreronis. Analyses of the influence of climatic factors revealed that dry ambient conditions favour the establishment of A. guerreronis. Neoseiulus paspalivorus and N. baraki have differing climatic requirements; the former being more abundant in warm and dry areas, the latter prevailing in moderately tempered and humid areas. We discuss the significance of our findings for natural and biological control of A. guerreronis.     

Chickens (Gallus domesticus) are natural intermediate hosts of Neospora caninum

Neospora caninum naturally infects many mammal species, but has not previously been demonstrated in birds. We examined sera for N. caninum antibodies from 200 outdoor chickens and from 200 chickens confined indoors in the state of Bahia, Brazil. Seroprevalence was greater in outdoor chickens (23.5% versus 1.5%, P<0.001). PCR testing for N. caninum was positive in six of 10 seropositive chickens. Amplicons from two of these were sequenced and had 97-98% nucleotide identity with N. caninum. This finding extends the list of intermediate hosts of N. caninum to include birds and may have important epidemiological consequences.