ArticlePDF Available

# The gut epithelium from feeding to fasting in the predatory soil mite Pergamasus longicornis (Mesostigmata: Parasitidae): one tissue, two roles

Authors:

## Abstract and Figures

A review of acarine gut physiology based on published narratives dispersed over the historical international literature is given. Then, in an experimental study of the free-living predatory soil mite Pergamasus longicornis (Berlese), quantitative micro-anatomical changes in the gut epithelium are critically assessed from a temporal series of histological sections during and after feeding on larval dipteran prey. An argued functional synthesis based upon comparative kinetics is offered for verification in other mesostigmatids. Mid- and hind-gut epithelia cell types interconvert in a rational way dependent upon the physical consequences of ingestion, absorption and egestion. The fasted transitional pseudo-stratified epithelium rapidly becomes first squamous on prey ingestion (by stretching), then columnar during digestion before confirmed partial disintegration (gut ‘lumenation’) during egestion back to a pseudo-stratified state. Exponential processes within the mid- and endodermic hind-gut exhibit ‘stiff’ dynamics. Cells expand rapidly ($$t_{1/2}=$$ 22.9–49.5 min) and vacuolate quickly ($$t_{1/2}=$$ 1.1 h). Cells shrink very slowly ($$t_{1/2}=$$ 4.9 days) and devacuolate gently ($$t_{1/2}=$$ 1.0–1.7 days). Egestive cellular degeneration has an initial $$t_{1/2}=$$ 7.7 h. Digestion appears to be triggered by maximum gut expansion—estimated at 10 min post start of feeding. Synchrony with changes in gut lumen contents suggests common changes in physiological function over time for the cells as a whole tightly-coupled epithelium. Distinct in architecture as a tissue over time the various constituent cell types appear functionally the same. Functional phases are: early fluid transportation (0–1 h) and extracellular activity (10–90 min); through rising food absorption (10 min to $$>1$$ day); to slow intracellular meal processing and degenerative egestive waste material production (1 to $$>12$$ days) much as in ticks. The same epithelium is both absorptive and degenerative in role. The switch in predominant physiology begins 4 h after the start of feeding. Two separate pulses of clavate cells appear to be a mechanism to facilitate transport by increasing epithelial surface area in contact with the lumen. Free-floating cells may augment early extracellular lumenal digestion. Possible evidence for salivary enzyme alkaline-related extra-corporeal digestion was found. Giant mycetome-like cells were found embedded in the mid-gut wall. Anteriorly, the mid-gut behaves like a temporally expendable food processing tissue and minor long-term resistive store. Posteriorly the mid-gut behaves like a major assimilative/catabolic tissue and ‘last-out’ food depot (i.e., a ‘hepatopancreas’ function) allowing the mite to resist starvation for up to 3.5 weeks after a single meal. A ‘conveyor-belt’ wave of physiology (i.e., feeding and digestion, then egestion and excretion) sweeps posteriorly but not necessarily pygidially over time. Assimilation efficiency is estimated at 82%. The total feeding cycle time histologically from a single meal allowing for the bulk of intracellular digestion and egestive release is not 52.5 h but of the order of 6 days ($$\equiv 0.17$$ total gut emptyings per day), plus typically a further 3 days for subsequent excretion to occur. Final complete gut system clearance in this cryptozooid may take much longer ($$>15$$ days). A common physiology across the anactinotrichid acarines is proposed. A look to the future of this field is included.
This content is subject to copyright. Terms and conditions apply.
A preview of the PDF is not available
... For instance, the long lanceolate ventrally curved gnathotectum of eviphidids may assist in the holding or perhaps the piercing of their nematode prey. Salivary enzymes (Bowman 2019) delivered by stylets (Evans 1992;Krantz and Walter 2009) facilitate prey liquefaction. The gnathotectum above the chelicerae together with the palps (Bowman 1984), plus the tritosternum and gnathosomal groove (Wernz and Krantz 1976) can maintain a fluid cylinder extended around the hypostome and mouth (Alberti and Coons 1999). ...
... If the evolutionary origin of body sclerotisation in the uropodoids was like that of turtle armour (Yong 2016;Black 2020;Schoch and Sues 2020), where evolutionarily the fossorial habit engendered first ventral strengthening between the legs for facilitating burrowing (through increased locomotory stability), before a secondary dorsal carapace was developed, then a key ancestral mechanical innovation in mesostigmatids could have been the ventral sternal shield and 'coxal' strengthening (as the worm-like ancestral body shrank under segmental consolidation). Given this: the position of the coxal gland openings (Bowman 1984) which debouch excess fluid ventrally; the ventral deuterosternal groove on the infracapitulum with the tritosternum (Wernz and Krantz 1976); the gnathosomal groove; and, the gnathotectum etc then all would facilitate liquid recycling needed for predation on watery prey (Bowman 2014(Bowman , 2017b(Bowman , 2019 when burrowing, delving into and excavating soil pores for food or shelter. Coxae in arachnids are discussed in Van der Hammen (1977a) where he points out that some of the most primitive arachnid members have been found in the deeper layers of soil. ...
Article
Full-text available
A model based upon mechanics is used in a re-analysis of historical acarine morphological work augmented by an extra seven zoophagous mesostigmatid species. This review shows that predatory mesostigmatids do have cheliceral designs with clear rational purposes. Almost invariably within an overall body size class, the switch in predatory style from a worm-like prey feeding (‘crushing/mashing’ kill) functional group to a micro-arthropod feeding (‘active prey cutting/slicing/slashing' kill) functional group is matched by: an increased cheliceral reach, a bigger chelal gape, a larger morphologically estimated chelal crunch force, and a drop in the adductive lever arm velocity ratio of the chela. Small size matters. Several uropodines (Eviphis ostrinus, the omnivore Trachytes aegrota, Urodiaspis tecta and, Uropoda orbicularis) have more elongate chelicerae (greater reach) than their chelal gape would suggest, even allowing for allometry across mesostigmatids. They may be: plesiosaur-like high-speed strikers of prey, scavenging carrion feeders (like long-necked vultures), probing/burrowing crevice feeders of cryptic nematodes, or small morsel/fragmentary food feeders. Some uropodoids have chelicerae and chelae which probably work like a construction-site mechanical excavator-digger with its small bucket. Possible hoeing/bulldozing, spore-cracking and tiny sabre-tooth cat-like striking actions are discussed for others. Subtle changes lead small mesostigmatids to be predator–scavengers (mesocarnivores) or to be predator–fungivores (hypocarnivores). Some uropodines (e.g., the worm-like prey feeder Alliphis siculus and, Uropoda orbicularis) show chelae similar in design to astigmatids and cryptostigmatids indicating possible facultative saprophagy. Scale matters—obligate predatory designs (hypercarnivory) start for mesostigmatids with chelal gape > 150 μm and cheliceral reach > 350 μm (i.e., about 500–650 μm in body size). Commonality of trophic design in these larger species with solifugids is indicated. Veigaia species with low chelal velocity ratio and other morphological strengthening specialisms, appear specially adapted in a concerted way for predating active soft and fast moving springtails (Collembola). Veigaia cerva shows a markedly bigger chelal gape than its cheliceral reach would proportionately infer suggesting it is a crocodile-like sit-and-wait or ambush predator par excellence. A small chelal gape, low cheliceral reach, moderate velocity ratio variant of the worm-like feeding habit design is supported for phytoseiid pollenophagy. Evidence for a resource partitioning model in the evolution of gnathosomal development is found. A comparison to crustacean claws and vertebrate mandibles is made. Alliphis siculus and Rhodacarus strenzkei are surprisingly powerful mega-cephalics for their small size. Parasitids show a canid-like trophic design. The chelicera of the nematophagous Alliphis halleri shows felid-like features. Glyphtholaspis confusa has hyaena-like cheliceral dentition. The latter species has a markedly smaller chelal gape than its cheliceral reach would suggest proportionately, which together with a high chelal velocity ratio and a high estimated chelal crunch force matches a power specialism of feeding on immobile tough fly eggs/pupae by crushing (durophagy). A consideration of gnathosomal orientation is made. Predatory specialisms appear to often match genera especially in larger mesostigmatids, which may scale quite differently. Comparison to holothyrids and opilioacarids indicates that the cheliceral chelae of the former are cutting-style and those of the latter are crushing-style. A simple validated easy-to-use ‘2:1 on’ predictive algorithm of feeding habit type is included based on a strength-speed tradeoff in chelal velocity ratio for ecologists to test in the field.
... Since our tested scorpions have been maintained exclusively on a diet of crickets prior to the beginning of the treatment, cricket permanence in the mid-gut and its consequent detection may be a result of prolonged exposure to that prey type in the past. Alternatively, as already observed in mites, the mid-gut is readily filled with food along its length, but the distribution of nutrients in the absorbing and storing tissues is not totally synchronous, and the most caudal portions of the mid-gut may be the last to be emptied (Bowman, 2017(Bowman, , 2019. ...
Article
Full-text available
Molecular analysis of gut content is one of the widest used methods to investigate diet in arthropods. Stomach content analysis in some arthropods is particularly difficult, e.g., in arachnids, because they have external digestion and a low foraging frequency. Scorpions have a particularly low feeding frequency, and their diet information is scarce. In this work we explore a DNA metabarcoding approach to detect prey DNA in Vietnamese forest scorpions (Heterometrus laoticus) under a controlled diet regime. A different type of prey (crickets, mealworms, and cockroaches) was offered once every 3 weeks for a total of 9 weeks. To assess the most suitable part of the digestive system and extraction method to use for molecular diet analysis, we separately analyzed three different portions of the digestive tract of scorpions (mid-gut, hepatopancreas, and hindgut) using two different extraction methods (salt-out method and a customized beads-based protocol). We calculated the detectability half-life of the prey DNA for each digestive tract section. We detected all three targeted prey items, showing that in scorpions multiple predation events can be distinguished in the same specimen within its last 9 weeks of foraging activity. The hepatopancreas was the portion of the digestive tract that provided the best prey detection and the longest DNA detectability half-life (51 days), followed by the mid-gut (22 days) and the hindgut (16 days). We found no significant difference between the extraction methods used. However, the salt-out method was less effective in some of the PCRs and is therefore not recommended for molecular diet analysis. © 2022 The Authors. Environmental DNA published by John Wiley & Sons Ltd.
Article
Full-text available
Histochemical staining of histological sections of Varroa destructor (Anderson and Trueman, 2000) mites reveal the internal body plan and are used to contrast the internal organs associated with feeding and reproduction of starved versus recently fed female mites. The gnathosoma is comprised of a powerful sucking pharynx, which employs 11 alternating dilator and constrictor muscles, the chelicerae, the salivary ducts, and the salivarium. Coronally, the esophagus is visible through the synganglion between its supraesophageal and subesophageal regions and connects posteriorly to the midgut. The midgut is devoid of food particles in starved mites, but in fed mites, the midgut epithelial cells are filled with innumerable globular spheroids replete with lipoproteins, including polyunsaturated lipids, whereas the lumen is filled with saturated lipids or other unidentified nutrients. In the opisthosomal body region of the fed female, the bilobed lyrate organ lies adjacent to the midgut on one side and the ovary on the opposite side, with very close cell to cell linkages that appear to form a syncytium. The fed female ovary contains an enormously enlarged ovum, and numerous elongated nurse cells extending from the lyrate organ. Dyes staining selectively for lipoproteins suggests rapid incorporation of neutral and polyunsaturated lipids and lipoproteins. Also evident near the ovary in fed females is the spermatheca filled with elongated, fully capacitated spermatozoa. The histological and histochemical findings reported in this study provide a fresh insight into the body structure, nutrition, and reproductive activity of the female of this harmful honey bee parasite and disease vector.
Article
Full-text available
The ability of several acaridid species to colonize and feed in diff erent nutritional substrates, such as grain crops, oil seeds, damaged vegetables, mixed fodder, hay and straw from the mangers and litter of livestock keeping places, litter, ambrosia and dead bees from beehive bottoms, is investigated. Species-specifi c diff erences in indices of domination and occurrence, and of Sorensen and Jaccard coeffi cients of similarity of species compositions on diff erent substrates are related not only to the nutritional inequality of these substrates, but also to the mite ability to grind them and to absorb these substrates through intracellular, contact and cavitary digestion using certain hydrolytic enzymes.
Article
Full-text available
The two-spotted spider mite (TSSM), Tetranychus urticae Koch (Acari: Tetranychidae), is one of the most polyphagous herbivores, feeding on more than 1,100 plant species. Its wide host range suggests that TSSM has an extraordinary ability to modulate its digestive and xenobiotic physiology. The analysis of the TSSM genome revealed the expansion of gene families that encode proteins involved in digestion and detoxification, many of which were associated with mite responses to host shifts. The majority of plant defense compounds that directly impact mite fitness are ingested. They interface mite compounds aimed at counteracting their effect in the gut. Despite several detailed ultrastructural studies, our knowledge of the TSSM digestive tract that is needed to support the functional analysis of digestive and detoxification physiology is lacking. Here, using a variety of histological and microscopy techniques, and a diversity of tracer dyes, we describe the organization and properties of the TSSM alimentary system. We define the cellular nature of floating vesicles in the midgut lumen that are proposed to be the site of intracellular digestion of plant macromolecules. In addition, by following the TSSM's ability to intake compounds of defined sizes, we determine a cut off size for the ingestible particles. Moreover, we demonstrate the existence of a distinct filtering function between midgut compartments which enables separation of molecules by size. Furthermore, we broadly define the spatial distribution of the expression domains of genes involved in digestion and detoxification. Finally, we discuss the relative simplicity of the spider mite digestive system in the context of mite's digestive and xenobiotic physiology, and consequences it has on the effectiveness of plant defenses.
Article
Full-text available
Ticks endure stressful off-host periods and perform as vectors of a diversity of infectious agents, thus engaging pathways that expectedly demand for autophagy. Little is known of ticks’ autophagy, a conserved eukaryotic machinery assisting in homeostasis processes that also participates in tissue-dependent metabolic functions. Here, the autophagy-related ATG4 (autophagin-1), ATG6 (beclin-1) and ATG8 (LC3) mRNAs from the human diseases vector Amblyomma sculptum and the cattle-tick Rhipicephalus microplus were identified. Comparative qPCR quantifications evidenced different transcriptional status for the ATG genes in the salivary glands (SG), ovaries and intestines of actively feeding ticks. These ATGs had increased relative transcription under nutrient-deprivation, as determined by validation tests with R. microplus embryo-derivative cells BME26 and A. sculptum SG explants incubations in HBSS. Starvation lead to 4–31.8× and ~ 60–500× increments on the ATGs mRNA loads in BME26 and A. sculptum SG explants, respectively. PI3K inhibitor 3MA treatment also affected ATGs expression in BME26. Some ATGs were more transcribed in the SGs than in the ovaries of cattle-ticks. Amblyomma sculptum/R. microplus interspecific comparisons showed that ATG4 and ATG6 were 0.18× less expressed in A. sculptum SGs, but ~ 10–100× more expressed in their ovaries when compared to R. microplus organs. ATG4 and ATG8a transcript loads were ~ 120× and ~ 40× higher, respectively, in A. sculptum intestines when compared to cattle-ticks of similar weight category. ATGs expression in A. sculptum intestines increased with tick weight, indicating Atgs contribution to intracellular blood digestion. Possible roles of the autophagy machinery and their organ-specific expression profile on vector biology are discussed.
Article
Full-text available
Mid- and hind-gut lumenal changes are described in the free-living predatory soil mite Pergamasus longicornis (Berlese) from a time series of histological sections scored during and after feeding on fly larval prey. Three distinct types of tangible material are found in the lumen. Bayesian estimation of the change points in the states of the gut lumenal contents over time is made using a time-homogenous first order Markov model. Exponential processes within the gut exhibit ‘stiff’ dynamics. A lumen is present throughout the midgut from 5 min after the start of feeding as the gut rapidly expands. It peaks at about 21.5 h–1.5 days and persists post-feeding (even when the gut is contracted) up until fasting/starvation commences 10 days post start of feeding. The disappearance of the lumen commences 144 h after the start of feeding. Complete disappearance of the gut lumen may take 5–9 weeks from feeding commencing. Clear watery prey material arrives up to 10 min from the start of feeding, driving gut lumen expansion. Intracellular digestion triggered by maximum gut expansion is indicated. Detectable granular prey material appears in the lumen during the concentrative phase of coxal droplet production and, despite a noticeable collapse around 12 h, lasts in part for 52.5 h. Posterior midgut regions differ slightly from anterior regions in their main prey food dynamics being somewhat faster in processing yet being slightly delayed. Posterior regions are confirmed as Last-In-Last-Out depots, anterior regions confirmed as First-In-First-Out conveyor belt processes. Evidence for differential lability of prey fractions is found. A scheme is presented of granular imbibed prey material being first initially rapidly absorbed ($$t_{\frac{1}{2}}$$ = 23 min), and also being quickly partly converted to globular material extra-corporeally/extracellularly ($$t_{\frac{1}{2}}$$ = 36 min)—which then rapidly disappears ($$t_{\frac{1}{2}}$$ = 1.1 h, from a peak around 4 h). This is then followed by slow intracellular digestion ($$t_{\frac{1}{2}}$$ = 6.9 h) of the resultant resistant prey residue matching the slow rate of appearance of opaque pre-excretory egestive refractive grains (overall $$t_{\frac{1}{2}}$$ = 4.5 days). The latter confirmed latent ‘catabolic fraction’ (along with Malpighian tubule produced guanine crystals) drives rectal vesicle expansion as ‘faeces’ during the later phases of gut emptying/contraction. Catabolic half-lives are of the order of 6.3–7.8 h. Membraneous material is only present in the lumen of the gut in starving mites. No obvious peritrophic membrane was observed. The total feeding cycle time may be slightly over 52.5 h. Full clearance in the gut system of a single meal including egestive and excretory products may take up to 3 weeks. Independent corroborative photographs are included and with posterior predictive densities confirm the physiological sequence of ingestion/digestion, egestion, excretion, defecation, together with their timings. Visually dark midguts almost certainly indicate egestive refractive grains (xanthine?) production. Nomograms to diagnose the feeding state of P. longicornis in field samples are presented and show that the timing of these four phases in the wild could be inferred by scoring 10–12 mites out of a sample of 20. Suggestions to critically confirm or refute the conclusions are included.
Article
Full-text available
Background Spiders are predaceous arthropods that are capable of subduing and consuming relatively large prey items compared to their own body size. For this purpose, spiders have evolved potent venoms to immobilise prey and digestive fluids that break down nutrients inside the prey’s body by means of extra-oral digestion (EOD). Both secretions contain an array of active proteins, and an overlap of some components has been anecdotally reported, but not quantified. We systematically investigated the extent of such protein overlap. As venom injection and EOD succeed each other, we further infer functional explanations, and, by comparing two spider species belonging to different clades, assess its adaptive significance for spider EOD in general. ResultsWe describe the protein composition of the digestive fluids of the mygalomorph Acanthoscurria geniculata and the araneomorph Stegodyphus mimosarum, in comparison with previously published data on a third spider species. We found a number of similar hydrolases being highly abundant in all three species. Among them, members of the family of astacin-like metalloproteases were particularly abundant. While the importance of these proteases in spider venom and digestive fluid was previously noted, we now highlight their widespread use across different spider taxa. Finally, we found species specific differences in the protein overlap between venom and digestive fluid, with the difference being significantly greater in S. mimosarum compared to A. geniculata. Conclusions The injection of venom precedes the injection with digestive fluid, and the overlap of proteins between venom and digestive fluid suggests an early involvement in EOD. Species specific differences in the overlap may reflect differences in ecology between our two study species. The protein composition of the digestive fluid of all the three species we compared is highly similar, suggesting that the cocktail of enzymes is highly conserved and adapted to spider EOD.
Article
Full-text available
Background The argasid tick Ornithodoros moubata is the main African vector of the human relapsing fever agent Borrelia duttoni and the African swine fever virus. Together with saliva, the tick midgut forms part of the host-tick-pathogen interface, and numerous midgut proteins play key functions in the blood digestion-related process and the infection and transmission of pathogens. This work explores the composition of the midgut proteome of unfed and fed O. moubata females with the aim to complete the biological information already obtained from the midgut transcriptome and provide a more robust and comprehensive perspective of this biological system. Methods Midgut tissues taken from females before feeding and 48 h after feeding were subjected to LC/MS-MS analysis. After functional characterization and classification of the proteins identified, the differences in the proteome between unfed and fed females were analysed and discussed. Additionally, a detailed analysis of particular groups of proteins that are involved in the processes of nutrient digestion and responses to the oxidative stress was carried out. Results1491 non-redundant tick proteins were identified: 1132 of them in the midgut of unfed ticks, 1138 in the midgut of fed ticks, and up to 779 shared by both physiological conditions. Overall, the comparative analysis of the midgut proteomes of O. moubata females before and after feeding did not reveal great differences in the number or class of proteins expressed, enzymatic composition or functional classification. Conclusions The hemoglobinolytic system in ixodids and argasids is very similar in spite of the fact that they display very different feeding and reproductive strategies. Although the main source of nutrients in ticks are proteins, lipids and carbohydrates also constitute significant nutritional sources and play an important part in the process of blood digestion. The genes and proteins involved in intracellular transport mechanisms, defensive responses, detoxifying responses and stress responses seem to be closely regulated, highlighting the complexity and importance of these processes in tick biology, which in turn assigns them a great interest as targets for therapeutic and immunological interventions.
Article
Full-text available
The occurrence of refractive crystals (aka guanine) is characterised in the Malpighian tubules of the free-living predatory parasitiform soil mite Pergamasus longicornis (Berlese) from a temporal series of histological sections during and after feeding on larval dipteran prey. The tubular system behaves as a single uniform entity during digestion. Malpighian mechanisms are not the 'concentrative' mechanism sought for the early stasis in gut size during the second later phase of prey feeding. Nor are Malpighian changes associated with the time of 'anal dabbing' during feeding. Peak gut expansion precedes peak Malpighian tubule guanine crystal occurrence in a hysteretic manner. There is no evidence of Malpighian tubule expansion by fluid alone. Crystals are not found during the slow phase of liquidised prey digestion. Malpighian tubules do not appear to be osmoregulatory. Malpighian guanine is only observed 48 h to 10 days after the commencement of feeding. Post digestion guanine crystal levels in the expanded Malpighian tubules are high-peaking as a pulse 5 days after the start of feeding (i.e. after the gut is void of food at 52.5 h). The half-life of guanine elimination from the tubules is 53 h. Evidence for a physiological input cascade is found-the effective half-life of guanine appearance in the Malpighian tubules being 7.8-16.7 h. Crystals are found present at all times in the lumen of the rectal vesicle and not anywhere else lumenally in the gut at all. No guanine was observed inside gut cells. There is no evidence for the storage in the rectal vesicle of a 'pulse' of Malpighian excretory products from a discrete 'pulse' of prey ingestion. A latent egestive common catabolic phase in the gut is inferred commencing 12.5 h after the start of feeding which may cause the rectal vesicle to expand due to the catabolism of current or previous meals. Malpighian tubules swell as the gut contracts in size over time post-prandially. There is evidence that at a gross level the contents of the rectal vesicle are mechanically voided by the physical mechanism of overall gut expansion altering the effective idiosomal volume available during prey ingestion. A complete cycle of feeding, digestion, egestion and excretion is approximately 9 days. Hunger/starvation likely commences at 10 days after the start of feeding. Up to 15 days may be needed to completely clear the idiosoma of excretory material. Nomograms for predicting the likely feeding time of mites from observations of idiosomal guanine in field samples indicate that as few as 5-6 mites scoring positive for Malpighian tubule guanine out of 20 infers a high probability that the typical time from start of feeding in a population sample was about 6 days (range 3-8 days) ago.
Article
By searching nucleotide databases for the North American Lyme disease vector, Ixodes scapularis, we have complemented the previously characterized European Ixodes ricinus legumain IrAE1 with a full set of nine analogous genes (isae1-9). Six of these were PCR confirmed as genes present in all tick genomes tested. The absolute mRNA copy number examined by quantitative (q)PCR enabled expression profiling and an absolute comparison of mRNA levels for individual I. scapularis (Is)AEs in tick tissues. Four IsAEs (1, 2, 4, 9) were expressed solely in the gut and thus are proposed to be involved in host blood digestion. Expression qPCR profiling over developmental stages confirmed IsAE1, the direct analogue of previously characterized I. ricinus IrAE1, as the principle legumain transcript in partially engorged females, and demonstrated its strong regulation by on-host feeding in larvae, nymphs and females. In contrast, IsAE2 was the predominant gut legumain in unfed nymphs, unfed females and males. In-silico, IsAE1 and IsAE2 protein three-dimensional structural models displayed minimal differences in overall proenzyme structures, even in comparison with recently resolved crystal structures of mammalian prolegumain. Three functional studies were performed in I. ricinus with IsAE1/IsAE2 analogues: double IrAE1/IrAE2 RNA interference silencing, feeding of ticks on IrAE1+IrAE2 immunized hosts and in vitro membrane tick feeding on blood containing a legumain-specific inhibitor. The latter experiment led to reduced weights of fully engorged ticks and limited oviposition, and indicated the potential of legumain inhibitors for novel anti-tick interventions.
Article
The presence of NAD-speciric malic dehydrogenase was demonstrated in the two-spotted spider mite. The Michaelis–Menten constant (K m ) of the enzyme for malate was found to be 1.25 × 10 ⁻³ M and for oxalacetate 5.0 × 10 ⁻⁵ M.