Temperature effects on the non-parasitic phase of Amblyomma parvum (Acari: Ixodidae)

The tick Amblyomma parvum has a wide distribution in the Central and South America. Therefore, throughout its distribution range, populations of this tick are exposed to different abiotic factors (e.g., Temperature and humidity). Here, we assess the effect of five temperatures, 18°C, 21°C, 24°C, 27°C, 32°C and 80 ± 10% RH on non-parasitic phases of A. parvum under controlled conditions of laboratory. Our results show that temperature affects all parameters of the non-parasitic phases of A. parvum. Mean periods of premolt and molting of immatures, and mean periods of pre-oviposition, oviposition and incubation of females decreases as temperature increases from 18 °C to at 32 °C. Conversely, the molting success of larvae increased from 18 °C to 32 °C but the percentages were statistically non-significant under 21°C, 24°C and 27°C. The molting success of nymphs was higher than 95% under all temperatures. Mean percentages of egg mass and EPE increases as temperature increase from 18 °C to 27°C, then both decrease at 32 °C. The mean percentage of egg hatching was higher than 90% from 21 to 32 °C. The total non-parasitic phase of A. parvum was completed in an average of 223.4, 150.9, 114.7, 90.2 and 69.0 days, respectively, under temperatures of 18°C, 21°C, 24°C, 27°C and 32°C. The effect of five temperatures studied in this experiment suggest that populations of A.parvum can exhibit different biological and ecological behaviors throughout its distribution range, as expected to occur in ticks with wide range distribution.

The parasitic nematode Strongyloides ratti exists as populations of long-lived asexual lineages.

Nematodes are important parasites of people and animals, and in natural ecosystems they are a major ecological force. Strongyloides ratti is a common parasitic nematode of wild rats and we have investigated its population genetics using single worm, whole genome sequencing. We find that S. ratti populations consist of mixtures of asexual lineages, widely dispersed across the host population. Genes that underly the parasitic phase of its life cycle are hyperdiverse, compared with the rest of the genome. These patterns of parasitic nematode population genetics have not been found before and may also apply to Strongyloides spp. that infect people.

Dermatobiosis in Panthera onca: first description and multinomial logistic regression to estimate and predict parasitism in captured wild animals

Dermatobia hominis is a parasite widely distributed in neotropical regions. The parasitic phase of the cycle is characterized by the formation of a subcutaneous nodule in the host, which can promote infestation by other dipterans and skin infections. The aim of this report is to register parasitism by D. hominis in free-ranging Panthera onca captured in the Brazilian wetland and to determine significant biological and meteorological factors that are likely to influence the presence of larval parasitism in captured wild jaguars. Between 2011 to 2020, 34 jaguars were captured and examined manually by searching for lesions characteristic of myiasis. By manual compression in the subcutaneous nodules, larvae morphologically identified as D. hominis (first and third instars) were collected from 13 jaguars. A multinomial logistic regression showed that adult jaguars had 16.49-fold higher odds of being parasitized than subadults. Thus, jaguars captured in the season of July–September have 34.01- and 11.42-fold higher odds of being parasitized compared to the seasons of October–December and April–June, respectively, which is associated with high total monthly precipitation in the previous season. The present study is the first to describe parasitism by D. hominis larvae in jaguars.

Genetic Diversity of Fusarium Wilt Disease of Banana

Bananas and plantains (Musa spp.) represent the fourth most important crop in the world. In 2017, an area of 5,637,508 hectares and a production of 153 million tons were reported. Fusarium wilt caused by the fungus Fusarium oxysporum f. sp. cubense (Foc), is considered one of the most destructive diseases of bananas and plantains worldwide. The pathogen Foc causes a typical wilt syndrome on infected plants, it has a saprophytic and parasitic phase in its life cycle. Fusarium wilt is a “polycyclic” disease. This pathogen shows a relatively diverse population genetic structure for a fungus apparently of asexual reproduction and is composed of different evolutionary lineages, which has 24 groups of vegetative compatibility (VCGs), two clades and nine clonal linage. Foc is a genetically diverse pathogen, although the available evidence so far indicates that it does not use the mechanisms of sexual reproduction, such as recombination, to increase its genetic diversity. Furthermore, the population of this fungus in Southeast Asia shows a high degree of variation, suggesting that Foc lineages evolved together with their hosts in Southeast Asia. Alternatively, it has been suggested that Foc has multiple independent evolutionary origins, both within and outside of the Musaceae origin center.

ON SOFTWARE IMPROVEMENT OF IMAGE CHANNEL SUPPRESSION IN SDR RECEIVERS WITH ANALOG CONVERSION TO A LOW INTERMEDIATE FREQUENCY

A method for digital signal processing in SDR receivers with analog conversion to a low intermediate frequency is proposed. In contrast to known systems, the proposed approach does not consider parasitic phase and amplitude distortions, but uses the direct method minimizing of the signal of the mirror reception channel. Generally speaking, this can be done simultaneously at several frequencies. It is shown that in computational terms, this is reduced to signal processing by an algorithm similar to a digital non-recursive filter, and to determine its coefficients, it is sufficient to solve a system of linear algebraic equations.

Stylostome formation by parasitic larvae of Allothrombium fuliginosum (Trombidiformes: Trombidiidae): morphology of feeding tubes and factors affecting their size

The morphology and formation of stylostomes (feeding tubes) in hosts’ body during the parasitic phase of Allothrombium fuliginosum (Hermann) larvae were studied for the first time with light microscopy (LM) and transmission electron microscopy (TEM). The stylostomes were observed in three aphids species—Acyrthosiphon pisum (Harris), Elatobium abietinum (Walker), and Macrosiphum rosae (L.)—parasitized by mites under laboratory conditions. They consisted of 2–6 main branches, preliminarily unbranched, then producing secondary and sometimes also tertiary branches as finally formed structures. Their walls were uniformly electron-dense, without any longitudinal and transverse stratifications and showed rather irregular outlines. Distally, the stylostome branches revealed transparent pores and cavities in their walls, connecting the stylostome canal with surrounding haemocoelic space. The total length of stylostomes at the end of the parasitic phase was on average 16× greater than that recorded in the youngest stylostomes. No differences in the overall shape of feeding tubes between host species were stated. The stylostomes formed in different host species did not differ significantly, except their total length, which attained the highest value in tissues of Ac. pisum.