Studies on the feeding of larval Argas persicus Oken

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

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 ([Formula: see text] 22.9-49.5 min) and vacuolate quickly ([Formula: see text] 1.1 h). Cells shrink very slowly ([Formula: see text] 4.9 days) and devacuolate gently ([Formula: see text] 1.0-1.7 days). Egestive cellular degeneration has an initial [Formula: see text] 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 [Formula: see text] day); to slow intracellular meal processing and degenerative egestive waste material production (1 to [Formula: see text] 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 ([Formula: see text] 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 ([Formula: see text] days). A common physiology across the anactinotrichid acarines is proposed. A look to the future of this field is included.

The mitochondrial genomes of Nuttalliella namaqua (Ixodoidea: Nuttalliellidae) and Argas africolumbae (Ixodoidae: Argasidae): estimation of divergence dates for the major tick lineages and reconstruction of ancestral blood-feeding characters

Ixodida are composed of hard (Ixodidae), soft (Argasidae) and the monotypic Nuttalliellidae (Nuttalliella namaqua) tick families. Nuclear 18S rRNA analysis suggested that N. namaqua was the closest extant relative to the last common ancestral tick lineage. The mitochondrial genomes of N. namaqua and Argas africolumbae were determined using next generation sequencing and de novo assembly to investigate this further. The latter was included since previous estimates on the divergence times of argasids lacked data for this major genus. Mitochondrial gene order for both was identical to that of the Argasidae and Prostriata. Bayesian analysis of the COI, Cytb, ND1, ND2 and ND4 genes confirmed the monophyly of ticks, the basal position of N. namaqua to the other tick families and the accepted systematic relationships of the other tick genera. Molecular clock estimates were derived for the divergence of the major tick lineages and supported previous estimates on the origins of ticks in the Carboniferous. N. namaqua larvae fed successfully on lizards and mice in a prolonged manner similar to many argasids and all ixodids. Excess blood meal-derived water was secreted via the salivary glands, similar to ixodids. We propose that this prolonged larval feeding style eventually gave rise to the long feeding periods that typify the single larval, nymphal and adult stages of ixodid ticks and the associated secretion of water via the salivary glands. Ancestral reconstruction of characters involved in blood-feeding indicates that most of the characteristics unique to either hard or soft tick families were present in the ancestral tick lineage.

Age-dependent immune response of chickens to feeding by Argas persicus larvae

Chickens of the dwarf Velsum breed acquired immunity to Argas persicus larvae during repeated infestations with 100 larval ticks in 2-week intervals, when primarily infested at the age of 10 weeks. This immunity was manifested by 74.6% and 75.9% rejection of larvae during secondary and tertiary infestations (P < 0.01), respectively, in relation to controls. The mean weight reductions observed were 16.5% and 12.2% in secondary and tertiary infestations, respectively (P < 0.05). Weak immunity also occurred after secondary and tertiary infestations in chickens infested first at the age of 6 and 8 weeks, but not in chickens aged 2 or 4 weeks at first infestation. No changes were observed in mean feeding periods of larvae engorged on chickens of all age groups (P > 0.05). A significant increase in the leucocyte counts in peripheral blood (P < 0.01 or P < 0.05), mostly of lymphocytes and heterophil granulocytes, followed each infestation in chickens of all age groups. Specific anti-tick circulating antibodies were detected by ELISA in the sera of 10-week-old chickens after primary infestations, in the 4-8-week chicken groups following secondary infestations when aged 6-10 weeks, and in the 2-week chicken group only after tertiary infestations, when the chickens reached the age of 6 weeks. A 53 kDa protein was recognized in the whole-body extract of larval ticks by immune serum during immunoblotting. This was probably the antigenic protein responsible for eliciting the circulating antibodies. The acquired immunity to ticks seen in chickens aged 6 weeks or more may be connected with maturation of the bursa of Fabricius and the development of complete immunocompetence, which is believed to occur in chickens at the age of 4-5 weeks.