Evaluation of performance characteristics of the medicinal leech (Hirudo medicinalis) for the treatment of venous congestion.

Medicinal leeches (Hirudo medicinalis) are a standard treatment for venous congestion, a complication that can occur after reconstructive surgery. If the cause of venous congestion cannot be surgically corrected, then medicinal leeches are used to temporarily increase perfusion levels and maintain physiologic requirements within the congested tissue. Leeches increase perfusion within congested tissue by actively drawing off blood as a bloodmeal. Furthermore, the leech bite continues to bleed and relieve congestion after detachment because of the anticoagulation effects of leech saliva left behind in the bite. In a porcine model, a 10 x 10 cm cutaneous flank flap was congested by clamping the venae comitantes. Four medicinal leeches were allowed to attach to the congested flap, and parameters of active feeding and passive bleeding after detachment were recorded. The average bloodmeal volume for the medicinal leeches was 2.45 ml. Average passive bleeding for the first 2 and 4 hours after leech detachment totaled 2.21 and 2.50 ml, respectively, with 90 percent of passive bleeding occurring within 5 hours after detachment. Laser Doppler imaging indicated that the spatial arrangement of surface perfusion increases were localized to a 1.6-cm-diameter circle around the leech head (bite) and corresponded well with the visual return of normal skin tones to the same area. This study provides a realistic and quantitative estimate of the spatial and volumetric characteristics of leech feeding and passive bleeding using a clinically relevant model of acute, severe congestion.     

Differential effects of lower body negative pressure and upright tilt on splanchnic blood volume

Upright posture and lower body negative pressure (LBNP) both induce reductions in central blood volume. However, regional circulatory responses to postural changes and LBNP may differ. Therefore, we studied regional blood flow and blood volume changes in 10 healthy subjects undergoing graded lower-body negative pressure (-10 to -50 mmHg) and 8 subjects undergoing incremental head-up tilt (HUT; 20 degrees , 40 degrees , and 70 degrees ) on separate days. We continuously measured blood pressure (BP), heart rate, and regional blood volumes and blood flows in the thoracic, splanchnic, pelvic, and leg segments by impedance plethysmography and calculated regional arterial resistances. Neither LBNP nor HUT altered systolic BP, whereas pulse pressure decreased significantly. Blood flow decreased in all segments, whereas peripheral resistances uniformly and significantly increased with both HUT and LBNP. Thoracic volume decreased while pelvic and leg volumes increased with HUT and LBNP. However, splanchnic volume changes were directionally opposite with stepwise decreases in splanchnic volume with LBNP and stepwise increases in splanchnic volume during HUT. Splanchnic emptying in LBNP models regional vascular changes during hemorrhage. Splanchnic filling may limit the ability of the splanchnic bed to respond to thoracic hypovolemia during upright posture.     

Distension of urinary bladder induces exaggerated coronary constriction in smokers with early atherosclerosis

Distension of the urinary bladder causes an increase in efferent sympathetic activity, which can precipitate myocardial ischemia. Smoking has been shown to modulate activities of afferent nerves from the distended urinary bladder and to impair endothelial function in response to sympathetic activation. To assess the effect of bladder distension on coronary dynamics in smokers, we measured epicardial and microvascular responses in 24 patients with early atherosclerosis (< 50% diameter stenosis). Patients were classified into habitual smokers (group 1, n = 14) and nonsmokers (group 2, n = 10). Habitual smokers were randomized into two subgroups on the basis of the use of doxazosin, as follows: subgroup 1A (n = 7), without administration of doxazosin before catheterization; subgroup 1B (n = 7), with dosing doxazosin. In response to bladder distension (mean intravesical pressure 21.5 mmHg), bladder distension significantly decreased coronary diameter at the stenotic segments, coronary blood flow, and increased coronary resistance compared with baseline values, in subgroup 1A patients. In subgroup 1B patients during bladder distension, coronary diameter, coronary blood flow, and coronary resistance did not show significant changes compared with baseline values. There were significant differences of coronary diameter at the stenotic segments, coronary blood flow, and of changes of coronary vascular resistance between subgroup 1A and group 2 during bladder distension, despite similar changes in rate-pressure product. The present study showed that urinary bladder distension caused an abnormal vasomotor response of epicardial vasoconstriction and a concomitant increased coronary resistance, which leads to reduction in coronary blood flow in patients with early atherosclerosis. Smoking may further impair the response, implying that smoking has exaggerated response to sympathetic stimulation of conduit and resistance vessels. The abnormal response was abolished by pretreated administration of doxazosin, suggesting that the involved mechanisms are related to alpha(1)-adrenoceptors.     

Regulation of urinary thromboxane B2 in man: Influence of urinary flow rate and tubular transport

Thromboxane B₂ (TxB) is excreted in human urine, but the mechanism of renal excretion and the quantitative relationship of urinary TxB to the active parent compound, thromboxane A₂, of renal or extrarenal origin is not established. To determine the effects of vasoactive hormones, uricosuric agents and urinary flow rate on TxB excretion, urinary TxB was measured by radioimmunoassay and mass spectrometry, and renal metabolism of blood TxB was determined by radiochromatography of urine after i.v. [³H]-TxB infusions. Basal TxB was 6.7 ± 1.1 ng/h during an oral water load, and TxB fell with s.q. antidiuretic hormone (to 3.4 ± 0.4 ng/h, P<0.01) and with fluid restriction (to 2.6 ± 0.5 ng/hr, P=0.001) in parallel with urinary volume. Urinary excretion of unmetabolized [³H]-TxB also fell (by 56%) with fluid restriction, implicating altered metabolism rather than synthesis as the mechanism of the urinary flow effect. Angiotensin II infusions slightly reduced both TxB and urine volume, consistent with a flow effect. In contrast, probenecid did not alter urine volume, but increased urinary uric acid (by 244%), TxB (from 5.6 ± 0.9 to 11.1 ± 2.9 ng/h) and urinary excretion of blood [³H]-TxB (by 243%) by similar amounts (all P<0.05), suggesting that TxB is actively reabsorbed in the proximal tubule, similarly to uric acid. Thus, urinary excretion of TxB of renal and extrarenal origin is regulated by proximal and distal tubule factors.     

Serotonergic mechanisms of the lateral parabrachial nucleus in renal and hormonal responses to isotonic blood volume expansion

This study investigated the involvement of serotonergic mechanisms of the lateral parabrachial nucleus (LPBN) in the control of sodium (Na+) excretion, potassium (K+) excretion, and urinary volume in unanesthetized rats subjected to acute isotonic blood volume expansion (0.15 M NaCl, 2 ml/100 g of body wt over 1 min) or control rats. Plasma oxytocin (OT), vasopressin (VP), and atrial natriuretic peptide (ANP) levels were also determined in the same protocol. Male Wistar rats with stainless steel cannulas implanted bilaterally into the LPBN were used. In rats treated with vehicle in the LPBN, blood volume expansion increased urinary volume, Na+ and K+ excretion, and also plasma ANP and OT. Bilateral injections of serotonergic receptor antagonist methysergide (1 or 4 microg/200 etal) into the LPBN reduced the effects of blood volume expansion on increased Na+ and K+ excretion and urinary volume, while LPBN injections of serotonergic 5-HT(2a)/HT(2c) receptor agonist, 2.5-dimetoxi-4-iodoamphetamine hydrobromide (DOI; 1 or 5 microg/200 etal) enhanced the effects of blood volume expansion on Na+ and K+ excretion and urinary volume. Methysergide (4 microg) into the LPBN decreased the effects of blood volume expansion on plasma ANP and OT, while DOI (5 microg) increased them. The present results suggest the involvement of LPBN serotonergic mechanisms in the regulation of urinary sodium, potassium and water excretion, and hormonal responses to acute isotonic blood volume expansion.     

Increased blood flow causes coordinated upregulation of arterial eNOS and biosynthesis of tetrahydrobiopterin

Shear stress, imposed on the vascular endothelium by circulating blood, critically sustains vascular synthesis of nitric oxide (NO). Endothelial NO synthase (eNOS) activity is determined by heat shock protein 90 (HSP90), caveolin-1, and the cofactor tetrahydrobiopterin (BH4). To determine whether increased blood flow concomitantly upregulates eNOS and GTP cyclohydrolase I (GTPCH I, the rate-limiting enzyme in BH4 biosynthesis), an aortocaval fistula model in the rat was employed wherein aortic blood flow is enhanced proximal but decreased distal to the fistula. Eight weeks after the creation of the aortocaval fistula, the proximal and distal aortic segments were harvested; sham-operated rats served as controls. Vasomotor function was assessed by isometric force recording. Expression of eNOS, HSP90, caveolin-1, Akt, phosphorylated eNOS (eNOS-Ser1177), and GTPCH I were determined by Western blot analysis. Biosynthesis of BH4 and GTPCH-I activity was examined by HPLC. In the aortic segments exposed to increased flow, contractions to KCl and phenylephrine were reduced, whereas endothelium-dependent relaxations were not affected compared with sham-operated or aortic segments with reduced blood flow. Expression of eNOS, caveolin-1, phosphorylated Akt, and eNOS-Ser1177 was enhanced in aortas exposed to increased blood flow. High flow augmented levels of cGMP and BH4 and increased expression of GTPCH I. In aggregate, these findings provide the first demonstration in vivo that coordinated vascular upregulation of eNOS, and GTPCH I accompanies increased blood flow. This induction of GTPCH I increases BH4 production, thereby optimizing the generation of NO by eNOS and thus the adaptive, vasorelaxant response required in sustaining increased blood flow.     

Dose response relation of the renal effects of PGA1, PGE2, and PGF2α in dogs

The effects of the three prostaglandins A₁, E₂, and F_2α on renal blood flow, glomerular filtration rate (GFR), fluid excretion, and urinary output of Na, K, Ca, Cl, and solutes were evaluated at a dose range of 0.01 – 10 μg/min. The prostaglandins were infused into the renal artery of dogs. GFR was not significantly altered by the PGs. PGA₁ increased renal blood flow by approximately of the control at 0.01 μg/min without dose dependence at higher infusion rates. It had only little effects which were not dose dependent on fluid and electrolyte output. The effects of PGE₂ on renal blood flow, fluid, sodium, and chloride excretion were dose dependent with a steep slope of the dose response curve between 0.1 and 1.0 μg/min. Blood flow was increased maximally by 80 %, urine volume by more than 400 %. PGF_2α had no effect on renal blood flow, whereas urinary output was increased to approximately the same maximal level as by E₂ although ten times higher doses were needed. Potassium excretion was less influenced than the excretion of Na and Cl and osmolar clearance was less increased than urine volume by all three prostaglandins.It is concluded that if a PG is involved in the regulation of the renal fluid or electrolyte excretion it is likely to be of the PGE-type. A PGA could only be involved in regulation of renal hemodynamics, whereas PGF although effective in the kidney exerts its effects at doses too high to have physiological significance.     

Persistent splanchnic hyperemia during upright tilt in postural tachycardia syndrome

Previous investigations have allowed for stratification of patients with postural tachycardia syndrome (POTS) on the basis of peripheral blood flow. One such subset, comprising "normal-flow POTS" patients, is characterized by normal peripheral resistance and blood volume in the supine position but thoracic hypovolemia and splanchnic blood pooling in the upright position. We studied 32 consecutive 14- to 22-yr-old POTS patients comprising 13 with low-flow POTS, 14 with normal-flow POTS, and 5 with high-flow POTS and 12 comparably aged healthy volunteers. We measured changes in impedance plethysmographic (IPG) indexes of blood volume and blood flow within thoracic, splanchnic, pelvic (upper leg), and lower leg regional circulations in the supine posture and during incremental tilt to 20 degrees, 35 degrees, and 70 degrees. We validated IPG measures of thoracic and splanchnic blood flow against indocyanine green dye-dilution measurements. We validated IPG leg blood flow against venous occlusion plethysmography. Control subjects developed progressive vasoconstriction with incremental tilt. Splanchnic blood flow was increased in the supine position in normal-flow POTS, despite marked peripheral vasoconstriction, and did not change during incremental tilt, producing progressive splanchnic hypervolemia. Absolute hypovolemia was present in low-flow POTS, all supine flows and volumes were reduced, there was no vasoconstriction with tilt in all segments, and segmental volumes tended to increase uniformly throughout tilt. Lower body (pelvic and leg) flows were increased in high-flow POTS at all angles, with consequent lower body hypervolemia during tilt. Our main finding is selective and maintained orthostatic splanchnic vasodilation in normal-flow POTS, despite marked peripheral vasoconstriction in these same patients. Local splanchnic vasoregulatory factors may counteract vasoconstriction and venoconstriction in these patients. Lower body vasoconstriction in high-flow POTS was abnormal, and vasoconstriction in low-flow POTS was sustained at initially elevated supine levels.     

The Impact of Increased Bladder Blood Flow on Storage Symptoms after Holmium Laser Enucleation of the Prostate

In order to investigate how holmium laser enucleation of the prostate (HoLEP) improves urinary storage symptoms, we assessed blood flow in the urinary bladder mucosa of patients with benign prostatic hyperplasia (BPH) before and after laser surgery. Seventy-four consecutive patients with BPH (median age 69 years, range; 53–88) underwent HoLEP at our institution and are included in this study. We prospectively assessed the International Prostate Symptom Score (IPSS), IPSS-QOL Score, the Overactive Bladder Symptom Score (OABSS), uroflowmetry, and blood flow in the urinary bladder, before and after surgery. Blood flow in the bladder mucosa was measured using the OMEGA FLOW (OMEGAWAVE, Tokyo, Japan) laser Doppler flowmeter. The median volume of the enucleated adenomas was 45.0 g (range: 25.0 to 83.2). The median IPSS improved significantly from 20 (range: 6–35) to 3 (0–22) (p<0.001; Wilcoxon signed-rank test), as did the storage symptoms score, which decreased from 13 (2–20) to 3 (1–8) (p<0.001). Median bladder blood flow increased at the trigone from 9.57±0.83 ml/sec to 17.60±1.08 ml/sec. Multiple regression analysis for the improved storage symptom score eliminated all explanatory variables except increased bladder perfusion. The data suggest that HoLEP improves blood flow in the bladder mucosa, which independently leads to the improvement of storage symptoms.     

Contrasting mortality in young freshwater leeches and triclads

A guild of leeches and triclads coexist and are the most numerous invertebrate predators on the stony shores of productive British lakes. Populations of all species are food-limited. Mortality of recruited young is considerably higher in leech than in triclad populations, and this paper investigates reasons for this. In particular, the feeding success of young leeches and triclads in relation to prey species, prey size, prey condition (alive or crushed), spatial heterogeneity (with or without the presence of stones or gravel), and the presence or absence of other young or adults predators (leeches or triclads) of the same or different species are investigated in the laboratory. Feeding success by young leeches and triclads on crushed prey without the presence of stones was high, but declined dramatically in leeches but not triclads when stones were present. Young leeches and triclads were inept at capturing live prey, of a small or large size, with the exception of soft-bodied prey such as oligochaetes. Feeding success by young predators on live prey was not increased by the presence of other young predators of the same or different species. With only a few exceptions, the presence of adult leeches, and to a much lesser extent adult triclads, increased the feeding success, growth and survival of young leeches and triclads. It is concluded that the high mortality of young leeches, compared to triclads, in field populations is due to their inability to locate damaged food in an environment with spatial heterogeneity due to a poorly developed chemosensory system. High and low levels of juvenile morality are accompanied by high and low reproductive rates in leech and triclad populations, respectively. It is unusual for a food limited population to have a high level of recruitment, but it is speculated that the characteristically high reproductive output in parasitic leeches, from which predaceous leeches are derived or have affinities, has been retained to counterbalance high juvenile mortality rates.     

Leeches run cold, then hot

Food processing is costly, potentially limiting the energy and time devoted to other essential functions such as locomotion or reproduction. In ectotherms, post-prandial thermophily, the selection of a warm environmental temperature after feeding, may be advantageous in minimizing the duration of this elevated cost. Although present in many vertebrate taxa, this behaviour had not previously been observed in invertebrates. Sanguivorous leeches ingest large blood meals that are costly to process and limit mobility until excess fluid can actively be expelled to reduce body volume. When presented with a temperature gradient from 10°C to 30°C, leeches select a temperature that is significantly warmer (24.3 ± 0.9°C, n = 6) than their acclimation temperature (T(a), 21°C). Unfed leeches preferred temperatures that were significantly cooler than ambient (12.8 ± 0.9°C, n = 6). This behavioural strategy is consistent with minimizing the time course of elevated post-feeding energy costs and reducing energy expenditure during fasting. Our observations raise the possibility that thermoregulatory behaviour of this type is an unrecognized feature of other invertebrate taxa.     

The impact of vertebrate and invertebrate predators on a stream benthic community

I assessed the impact of both vertebrate and invertebrate predators on a lotic benthic community in a 1-month-long experiment, using enclosures containing cobble/gravel bottoms, with large-mesh netting that allowed invertebrates to drift freely. Brown trout (Salmo trutta) and leeches (Erpobdella octoculata) were used as predators and four treatments were tested: a predator-free control, leeches only, trout only, and leeches and trout together. A density of 26.7 leeches/m² (20 leeches/enclosure) and 1.3 trout/m² (one trout per enclosure) was stocked into the enclosures. The total biomass of invertebrate prey was significantly lower in the trout and trout plus leech treatments than in the leech and control treatments, which were due to strong negative effects of trout on Gammarus. On the individual prey taxon level, both trout and leeches affected the abundance of Asellus , Baetis and Ephemerella, whereas the abundance of Gammarus was only affected by trout, and the abundance of Orthocladiinae and Limnephilidae was only affected by leeches. In the treatment with trout and leeches together, the abundance of Ephemerella and Baetis was higher than when trout or leeches were alone, which was probably due to predator interactions. Leeches and trout had no effects on prey immigration but did affect per capita emigration rates. Both trout and leeches indirectly increased periphyton biomass in enclosures, probably due to their strong effects on grazers. Both trout and leeches were size-selective predators, with trout selecting large prey, and leeches selecting small prey. Size-selective predation by trout and leeches affected the size structure of five commonly consumed prey taxa. Trout produced prey populations of small sizes owing to consumption of large prey as well as increased emigration out of enclosures by these large prey. Leech predation produced prey assemblages of larger size owing to consumption and increased emigration of small prey. These results suggest that in lotic habits, predatory invertebrates can be as strong interactors as vertebrate predators. Received: 23 June 1997 / Accepted: 4 May 1998     

Cannibalism in a Population of the Medicinal Leech (<Emphasis Type="Italic">Hirudo medicinalis</Emphasis> L.)

Medicinal leeches (Hirudo medicinalis L.) were maintained in large ponds in a commercial leech farm at Biebertal, Germany. The feeding of hungry adult leeches was performed on representative individuals that were placed on cloth soaked with mammalian blood obtained from a local butchery (pig, Sus scrofa). In a second set of experiments, cane toads (Bufo marinus) were used as host organisms. The leeches rapidly attached to the toads, explored the body and sucked blood. After feeding, the fully engorged leeches were placed into the pond or an aquarium. In this artificial habitat, the satiated leeches were attacked by hungry conspecifics, sucked off, and killed. This observation demonstrates that H. medicinalis must be classified as a cannibalistic annelid.     

On the origin of leeches by evolution of development

Leeches are a unique group of annelids arising from an ancestor that would be characterized as a freshwater oligochaete worm. Comparative biology of the oligochaetes and the leeches reveals that body plan changes in the oligochaete-to-leech transition probably occurred by addition or modification of the terminal steps in embryonic development and that they were likely driven by a change in the feeding behavior in the ancestor of leeches. In this review article, developmental changes that are associated with the evolution of several leech-specific traits are discussed. These include (1) the evolution of suckers, (2) the loss of chaetae, (3) the loss of septa, and (4) a fixed number of segments. An altered developmental fate of the teloblast is further proposed to be a key factor contributing to the fixation of the segment number, and the evolutionary change in teloblast development may also account for the loss of the ability to regenerate the lost body segments in the leech.     

Measurement of bronchial arterial blood flow and bronchovascular resistance in sheep

We studied the bronchial arterial blood flow (Qbr) and bronchial vascular resistance (BVR) in sheep prepared with carotid-bronchial artery shunt. Nine adult sheep were anesthetized, and through a left thoracotomy a heparinized Teflon-tipped Silastic catheter was introduced into the bronchial artery. The other end of the catheter was brought out through the chest wall and through a neck incision was introduced into the carotid artery. A reservoir filled with warm heparinized blood was connected to this shunt. The height of blood column in the reservoir was kept constant at 150 cm by adding more blood. Qbr was measured, after interrupting the carotid-bronchial artery flow, by the changes in the reservoir volume. The bronchial arterial back pressure (Pbr) was measured through the shunt when both carotid-bronchial artery and reservoir Qbr had been temporarily interrupted. The mean Qbr was 34.1 +/- 2.9 (SE) ml/min, Pbr = 17.5 +/- 3.3 cmH2O, BVR = 3.9 +/- 0.5 cmH2O X ml-1 X min, mean pulmonary arterial pressure = 21.5 +/- 3.6 cmH2O, and pulmonary capillary wedge pressure (Ppcw) = 14.3 +/- 3.7 cmH2O. We further studied the effect of increased left atrial pressure on these parameters by inflating a balloon in the left atrium. The left atrial balloon inflation increased Ppcw to 25.3 +/- 3.1 cmH2O, Qbr decreased to 21.8 +/- 2.4 ml/min (P less than 0.05), and BVR increased to 5.5 +/- 1.0 cmH2O.ml-1.min (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Studies on the mechanism of non-oliguric experimental acute renal failure.

Although acute renal failure, caused either by renal ischemia or nephrotoxic agents, is usually characterized by oliguria, a severe fall in glomerular filtration rate, and a fall in renal blood flow, some patients and experimental models display a non-oliguric pattern of renal injury. The present study was designed to evaluate the mechanism of preservation of high urinary flow rate under this condition. Following the administration of the aminoglycoside gentamicin to rats for five days, a decrease in concentrating ability was demonstrated, caused by impaired vasopressin-mediated water transport. Further treatment resulted in a fall in Cin to 15 percent of control, although RBF was reduced to only 67 percent of control, and urine flow rate rose above control levels. Induction of acute and renal failure with dichromate was associated with variable high or low urinary flow rates according to pre-injury intake of sodium. Urine volume correlated directly with cortical blood flow. These data suggest that the non-oliguric pattern of acute renal injury is caused by preservation of cortical perfusion in the setting of severe tubular injury.     

Splanchnic hyperemia and hypervolemia during Valsalva maneuver in postural tachycardia syndrome

Prior work demonstrated dependence of the change in blood pressure during the Valsalva maneuver (VM) on the extent of thoracic hypovolemia and splanchnic hypervolemia. Thoracic hypovolemia and splanchnic hypervolemia characterize certain patients with postural tachycardia syndrome (POTS) during orthostatic stress. These patients also experience abnormal phase II hypotension and phase IV hypertension during VM. We hypothesize that reduced splanchnic arterial resistance explains aberrant VM results in these patients. We studied 17 POTS patients aged 15-23 yr with normal resting peripheral blood flow by strain gauge plethysmography and 10 comparably aged healthy volunteers. All had normal blood volumes by dye dilution. We assessed changes in estimated thoracic, splanchnic, pelvic-thigh, and lower leg blood volume and blood flow by impedance plethysmography throughout VM performed in the supine position. Baseline splanchnic blood flow was increased and calculated arterial resistance was decreased in POTS compared with control subjects. Splanchnic resistance decreased and flow increased in POTS subjects, whereas splanchnic resistance increased and flow decreased in control subjects during stage II of VM. This was associated with increased splanchnic blood volume, decreased thoracic blood volume, increased heart rate, and decreased blood pressure in POTS. Pelvic and leg resistances were increased above control and remained so during stage IV of VM, accounting for the increased blood pressure overshoot in POTS. Thus splanchnic hyperemia and hypervolemia are related to excessive phase II blood pressure reduction in POTS despite intense peripheral vasoconstriction. Factors other than autonomic dysfunction may play a role in POTS.     

Population size, weight distribution and food in a persistent population of the rare medicinal leech, Hirudo medicinalis

1. It is important for species recovery and conservation management projects to know the minimum viable population size for rare and endangered species, such as the medicinal leech, Hirudo medicinalis. Therefore, using a catch‐removal method, this study estimated every two years (1986, 1988, 1990, 1992) the total number of medicinal leeches in a tarn in the English Lake District, and the number of mature adults in the population. 2. Four samples were taken each year in June and July, when water temperatures exceeded 20 °C. Population size was estimated both by maximum likelihood and regression methods. All leeches were weighed alive and size groups were separated by polymodal frequency analysis. A small sample of the blood meal in each leech gut was taken before the leeches were returned to the tarn, and was used to estimate the proportion of mammalian and non‐mammalian blood in the meals. 3. Both methods of estimation produced similar values, increasing confidence in the population estimates. Values for the total population in June and July varied among years from 248 to 288, the maximum value being only 16% higher than the minimum. Values for the number of mature leeches varied from 48 to 58 (19–20% of the total population), and this was an estimate of the effective population size. 4. There were four size groups. The largest mature leeches (live weight >5 g) in group IV formed only 1% of the population, and the smallest (0.02–0.5 g) in group I 14–17%. Most leeches were in two overlapping groups of immature (64–67% of population) and mature (18%) leeches with size ranges of 0.4–3.4 g and 2.5–5 g respectively. The percentage of leeches in each size group was very consistent among years. Blood meals were found in 38–44% of the leeches in group I, 45–50% in group II, 70–75% in group III, and 100% in group IV, but mammalian blood was present only in larger mature leeches (>3.5 g). 5. Medicinal leeches were first detected in the tarn in 1980 and are still present in 2007, so the population has persisted for at least 27 years. Compared with minimum viable population sizes for other species, including many endangered species, values for this medicinal leech population are extremely low, but may be typical of some rare freshwater invertebrates in isolated habitats.     

Leeches as a source of mammalian viral DNA and RNA—a study in medicinal leeches

Surveillance of wild vertebrates can be challenging in remote and inaccessible areas such as tropical rainforests. Blood-feeding parasites, such as leeches, can facilitate wild vertebrate monitoring by targeting residual DNA from the animals the leeches feed on. Successes in detecting host DNA from leeches suggest that host viruses may also be detectable. To systematically test this hypothesis, we performed a proof of concept study using quantitative PCR (qPCR) to detect DNA viruses (bovine herpesvirus [BHV], human adenovirus [HAdV]) and RNA viruses (influenza A [InfA] and measles morbillivirus [MeV]) from nucleic acids extracted from medicinal leeches fed with blood spiked with each virus. All viruses except BHV showed a gradual decline in concentration from day 1 to 50, and all except BHV were detectable in at least half of the samples even after 50 days. BHV exhibited a rapid decline at day 27 and was undetectable at day 50. Our findings in medicinal leeches indicate that leeches collected in the wild might be an untapped resource for detecting vertebrate viruses and could provide new opportunities to study wildlife viral diseases of rare species in challenging environments, where capturing and handling of animals is difficult.     

Activity of selected hydrolytic enzymes from leeches (Clitellata: Hirudinida) with different feeding strategies

Hydrolase activities of extracts from different parts of the bodies of parasitic (Theromyzon tessulatum, Piscicola geometra) and predatory (Erpobdella octoculata, Glossiphonia complanata) leeches were examined. The highest activity was detected in the extracts from sections containing the intestine. Hydrolase activities in the crop and intestine of parasitic leeches were higher than in predatory leeches. The high activity of most of hydrolases in those segments may indicate the intensity of digestion and absorption processes in leeches. A lack of trypsin activity and low chymotrypsin activity are likely to result from the presence of inhibitors of these enzymes. The high activity of the majority of the analyzed hydrolases in extracts derived from the head segment of predatory leeches enables, through digestion of tissues, their easy access to physiological fluids of a host. In turn, in extracts from the head segment of predatory leeches, only four hydrolases were shown to be active. Lipase activity was not found in any of the samples, while α-galactosidase activity was found only in extracts from the head segment of T. tessulatum and P. geometra. Trypsin activity was detected in the extract from the intestine contents of H. sanguisuga and in the extract from the head segment of P. geometra. The results demonstrate the presence of majority of hydrolases occurring in other animals in the alimentary tract of leeches. The study also shows that the crop of leeches is not only a food reservoir, but also the site where digestion and absorption processes take place.