Freshwater Leech Research Articles

The life-cycle and feeding of the African freshwater leechHelobdella conifer(Glossiphoniidae)

The life-cycle, breeding and feeding of the freshwater leech Helobdella conifera were examined in the laboratory. The life-cycle is annual with the young brooded by the parent for the first two months after hatching. Sexual maturity is attained two months after leaving the parent when the first batch of eggs are produced and the young brooded. The number of broods ranges from one to four with the majority producing three. A few young leeches fed on the snail Helisoma duryi while still attached to the parent but the majority did not feed until 11 days after leaving the parent with 12–23 small (4.0–7.0 mm) snails consumed before producing their first batch of eggs. The life time consumption of small snails ranged from 26–60 with no correlation between the numbers of snails consumed and the numbers of broods or the numbers of progeny. Leeches only fed on small, live H. duryi and did not feed on large (10.0–13.0 mm) individuals although they fed as scavengers on dead large snails. A strong preference was exhi...

Inter-population genetic variation in the freshwater leech Nephelopsis obscura in relation to environmental heterogeneity

Genetic variation among three populations of the freshwater leech, Nephelopsis obscura was examined. Fixed genetic differences occurred among populations at four protein-coding genes. Despite the higher probability of dispersal between Stephenson's Pond in the Alberta prairie-foothills zone and the Alberta Rocky Mountain pond (80 km apart) and the lower probability of dispersal between these two ponds and the Uinta Mountain population in Utah (1 200 km away), the Alberta Rocky Mountain population differed from the Utah Uinta Mountain population at only one locus while both populations differed at five loci from the Stephenson's Pond population. All four enzymes showing differences between populations are involved in anaerobic pathways. It is hypothesized that genetic similarities and differences are correlated with the dissolved oxygen regimes acting as a selective force rather than geographical distance between populations.

Activity and Foraging Behaviour in the Predatory Freshwater Leech Nephelopsis obscura (Erpobdellidae)

1. The hypotheses tested were that foraging behavioural responses (number of meals consumed, the number of encounters with prey and feeding time) and activity (swimming time) of the freshwater predatory leech Nephelopsis obscura were higher in the dark than in the light, increased with the size of the predator and increased with the length of the starvation period prior to feeding. 2. While swimming activity was longer in the dark, not all the foraging behaviour variables followed this pattern. There was an inverse relationship between swimming time and the number of meals consumed and the poor correspondence between swimming time and number of prey encounters indicates that swimming is not always directly associated with increased foraging and might be related to movements between micro-habitats. 3. The effect of body size on feeding is complicated by its interaction with hunger levels and the ability of the predator to handle prey.

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.

The effects of temperature and feeding regime on hermaphroditism and gametogenesis of Nephelopsis obscura, a freshwater predatory leech

The effects of temperature (15 and 20 °C) and food ration (feeding 33, 23, or 13 per week (ad libitum)) on hermaphroditism and gametogenesis of Nephelopsis obscura were investigated in the laboratory. Animals fed 33 and 23 a week reached an asymptotic biomass and reproductive maturity at approximately the same time (41–43 weeks) at both 15 and 20 °C. However, none of the leeches fed 13 a week attained the final stages of reproductive maturity, even though they reached an asymptotic biomass. Regardless of temperature or food ration, testisacs were initiated when N. obscura reached 62–87 mg and ovisac initiation always occurred 3 weeks after the first occurrence of the testisacs. In contrast to the field, where N. obscura is protandrous, in the laboratory N. obscura is protogynous because of the increase from 2–5 to 15–22 weeks between stages 4 and 5 of spermatogenesis.

The bioenergetic costs of specific dynamic action and ammonia excretion in a freshwater predatory leech Nephelopsis obscura

The energy utilized by the predatory freshwater leech for specific dynamic action (SDA) and exogenous excretion, and the proportion of absorbed energy available for growth and/or activity were determined at 5,10,15, 20 and 25°C. SDA and exogenous ammonia excretion increased with increases in temperature to 20°C but decreased at 25°C. The duration of SDA decreased from 19 hr at 5°C to 11 hr at 25°C, while the duration of exogenous excretion decreased from 22 hr at 5°C to 11 hr at 25°C. The proportion of absorbed energy utilized for SDA and exogenous excretion decreased from 5°C to 15°C and increased at 25°C; however the energy available for growth and activity increased from 7.4 J/day at 5°C to a maximum of 32.6 J/day at 15°C, decreasing to 12.7 J/day at 25°C.

The biology and adaptations of the hippopotamus leech Placobdelloides jaegerskioeldi (Glossiphoniidae) to its host

The specificity of the association between the freshwater leech Placobdelloides jaegerskioeldi and the hippopotamus was confirmed both by collections from the Kruger National Park and by laboratory experiments. Placobdelloides jaegerskioeldi is established as the only leech showing species specificity for a mammal. Forty sexually mature leeches were collected free-living and 2260 mature and immature leeches were collected from 40 of 53 culled hippopotami. In the field P. jaegerskioeldi was never found on any of the alternative hosts, and none fed in the laboratory when offered a range of potential hosts. A combination of unique attributes, including mode of locomotion, anatomical features, and feeding behaviour, makes it possible for this leech to utilize the hippopotamus as a host. Evidence suggests that mating in P. jaegerskioeldi is restricted to the rectum of the hippopotamus.

Incidence of the Leech Actinobdella pediculata on Freshwater Drum in Lake Erie

Actinobdella pediculata (Glossiphoniidae), a freshwater leech, was found attached to freshwater drum ( Aplodinotus grunniens) from western Lake Erie during 1991 through 1993. The animal was first observed during routine examinations of freshwater drum collected in May 1991. The leeches were usually attached to the inside, lower portion of the opercula near the isthmus. Incidence of attachment increased with freshwater drum age and length. No noticeable adverse effects on the fish from attachment by the leech were noted.

Bioenergetic responses to the initiation of winter and glycerol formation in the leech Nephelopsis obscura

Changes in glycogen, total lipid, glycerol, triacylglycerols, and active phosphorylase were examined in the freshwater leech Nephelopsis obscura during acclimation from summer (20 °C) to winter (4 °C) temperatures, during exposure to winter temperatures, and after return to summer temperatures, with oxygen maintained at saturation. Total lipids, triacylglycerols, and glycogen did not increase significantly until the temperature dropped to 7 °C, and glycerol concentrations did not increase until after exposure to 4 °C for 3 days. Thus, while decreased temperature triggered increased energy storage, glycerol synthesis required a cold stress. Shifting cold-stressed N. obscura back to 20 °C resulted in rapid resynthesis of glycogen coupled with a decrease in glycerol, but no changes in total lipid and triacylglycerols.

Freshwater leeches from Yemen

The occurrence of freshwater leeches in ten different wadis in Yemen was determined. Four species were recorded for the first time: Batracobdelloides tricarinatus, Helobdella conifera, Limnatis nilotica and Placobdelloides multistriatus. These species, typically found in Africa, are recorded in Yemen on the border of two biogeographical regions.

Physicochemical features and oxygenation properties of extracellular hemoglobin from the leech, Macrobdella decora

1. 1. Extracellular hemoglobin from the freshwater leech Macrobdella decora has a sedimentation coefficient of 57 S. Under the electron microscope, the molecule displays a two-layered hexagonal structure, characteristic of annelid extracellular hemoglobins, with dimensions 29.9 ± 1.8 nm (across the hexagon) and 19.2 ± 1.2 nm (height). M. decora hemoglobin contains one heme per 24,000 g of protein. 2. 2. The oxygen binding properties of this high molecular weight hemoglobin are characterized as a function of pH, cations and temperature. 3. 3. The oxygenation properties are affected by protons. At near-physiological cation concentrations, the oxygen affinity and cooperativity rise concomitantly with increasing alkalinity. At pH ∼ 8.0 and 20°C both these parameters attain maximal values of P 50 = 3.0 mm Hg and n 50 = 3.1. A normal alkaline Bohr effect ( φ = −0.33) at the pH range 6.5–7.5 is observed. 4. 4. The oxygen binding characteristics are also extremely sensitive to cations. At pH 7.75 and 20°C both oxygen affinity and cooperativity rise with increasing cation concentrations. Divalent cations such as Ca 2+ and Mg 2+ produce a larger effect than monovalent ones. They start to be effective at concentrations as low as 0.05 mM.

Metabolic adaptations by the leech Nephelopsis obscura during long‐term anoxia and recovery

AbstractMetabolic adaptations to long‐term (40 day) anoxia were determined in two size groups (small and large) of the freshwater leech Nephelopsis obscura. Neither size group accumulated the lactic acid during anoxia; rather succinate and alanine were the major end products. Glycogen and amino acids were the primary energy reserves utilized with lipid also utilized by small N. obscura. After 40 days of anoxia glycolytic flux was reduced by 99.8% in small and 99.7% in large N. obscura. Cellular energy status adenosine triphosphate/adenosine diphosphate (ATP/ADP) also declined significantly in small (79%) and large (69%) leeches. After return to normoxia the energy charge in small N. obscura was restored within 6 hours and glycogen, malate, succinate, alanine, and aspartate restored within 24 hours. Large N. obscura utilized lower proportions of their energy reserves than small N. obscura. © 1993 Wiley‐Liss, Inc.

Assessment of Activity-Specific Metabolism of Aquatic Organisms: An Improved System

An improved flow-through respirometer capable of assessing activity-specific metabolism of aquatic organisms is presented and assessed. The system is highly sensitive and versatile, since it continuously monitors and records activity-specific oxygen consumption readings for periods up to 72 h and is capable of detecting differences in metabolism of individual specimens of similar weight. Using this system, we demonstrated individual variation and intraspecific differences in metabolism between two size classes of the freshwater leech Nephelopsis obscura and interspecific differences between N. obscura and another freshwater leech, Erpobdella montezuma, and compared these findings with the metabolism of the amphipod Hyalella montezuma.

The effects of different dissolved oxygen regimes on the growth of a freshwater leech

The growth rates of two size classes of Nephelopsis obscura, a freshwater predatory leech, were determined at five different dissolved oxygen regimes (three constant 10%, 100%, 300%. and two diel cyclical 10‐100% and 100‐300%) at 15°C Both small and large N obscura showed highest growth rates in the diel 100‐300% regime and the lowest in the constant 10% or diel 10‐100% regimes These differences in growth rate affect the predicted time to reach the minimum size for reproduction, e g 42 8 d m constant 10% and 315dm diel 100‐300% regimes for small and 67 9 d and 8 8 d respectively for large N obscura These differences determine whether individuals surviving winter reach maturity and produce cocoons in the spring or the autumn and whether individuals hatched in the spring can reach mature size the same summer

The life-cycle, ecology and host specificity of the freshwater leech Alboglossiphonia polypompholyx (Glossiphoniidae) in Egypt

Alboglossiphonia polypompholyx spends most of its life cycle endoparasitic in the mantle cavity of the snail Bulinus truncatus — possibly its only host. Adult A. polypompholyx leaves the snail about one month before the commencement of egg-laying. Hatching occurred after about 15 d and after brooding on the venter of the parent for 7–10 d, the young briefly become free-living before entering the mantle cavity of B. truncatus. Within the mantle cavity, A. polypompholyx feeds and grows for 16–20 weeks before leaving the snail as adults. In the field and in laboratory experiments, adult leeches left the snails in August/September and January with cocoons produced in October/November and February/March, respectively. Free-living adult leeches do not feed and die 1–2 months after the cessation of brooding.

The effects of different oxygen regimes on the feeding and vertical distribution of Nephelopsis obscura (Hirudinoidea)

The feeding rates and vertical distribution of the freshwater leech Nephelopsis obscura, fed on different densities of third instar Chironomus riparius, were determined in the laboratory at three different constant dissolved oxygen regimes (10%, 100%, 300% saturation) at 15 °C. The rate of feeding increased linearly with prey density up to maximal field prey densities, with no satiation response. Analysis of covariance showed that the rate (slope) at which prey were consumed was not significantly different among oxygen regimes but the amount eaten at any given prey density was higher in higher dissolved oxygen saturations. Analysis of the vertical distribution of N. obscura at different oxygen saturations and prey densities showed a higher proportion of N. obscura on or in the mud substrate compared to the water column at 100% and 300%. No correlation was found between prey density and the vertical distribution of N. obscura, but the numbers of prey eaten were correlated with the proportion of N. obscura on the mud substrate. These results indicate that higher percentage dissolved oxygen regimes increase the feeding of N. obscura and are of potential importance in explaining the seasonal depth distribution and microdistribution patterns recorded for N. obscura.

New records of freshwater leeches (Annelida: Hirudinea) from Quebec

New records of freshwater leeches (Annelida: Hirudinea) from Quebec

Mycoflora associated with five species of freshwater leeches

Twenty-two species belonging to 11 genera of zoosporic fungi were collected from 10 freshwater sites and from five species of leeches on sesame and hemp seeds, maize grains and Pinus pollen grains as baits at 22 degrees C. Dictyuchus, Achlya, Pythium, Allomyces and Saprolegnia were the most common genera. The highest population of zoosporic fungi was estimated from Batracobdelloides tricarinata, the lowest from Barbronia assiuti. In addition fifty-three species and 1 variety representing 23 terrestrial fungal genera were identified on glucose (17 genera and 41 species) and cellulose (20 genera and 34 species + 1 variety) Czapek's Dox agar at 28 degrees C. The most common species on the two media were Aspergillus niger, A. fumigatus, A. flavus, Trichoderma harzianum, Gibberella fujikuroi and Penicillium chrysogenum. Some fungi were common only on cellulose agar medium such as Botryotrichum atrogriseum, Chaetomium bostrychodes, Dactylella alaskana and Drechslera halodes. Batracobdelloides tricarinata was the richest with terrestrial fungi whereas Salifa delicata was the poorest. Five leech species, namely Alboglossiphonia polypompholyx, Batracobdelloides tricarinata, Helobdella conifera, Barbronia assiuti and Salifa delicata were used during this investigation.

Experimental observations on the specificity of Apatemon (Australapatemon) minor (Yamaguti 1933) (Digenea: Strigeidae) toward leech (Hirudinea) second intermediate hosts

The infectivity of Apatemon (Australapatemon) minor cercariae to 7 species of freshwater leech was examined under laboratory conditions. The leech species exposed to infection were; Erpobdella octoculata, Helobdella stagnalis, Glossiphonia heteroclita, Glossiphonia complanata, Hemiclepsis marginata, Piscicola geometra, and Theromyzon tessulatum. Five species were capable of acting as second intermediate hosts. Despite this broad specificity only Erpobdella octoculata and Helobdella stagnalis could be considered to show a high degree of compatibility with the parasite. In these 2 leech species more than 38% of the cercariae successfully penetrated and established metacercarial cyst infections. The leeches Piscicola geometra and Theromyzon tessulatum did not become infected. Close parallels were found between the species order of host utilization determined experimentally and that revealed by a range of field surveys in Britain, Eastern Europe and Russia. This suggests that the order of second intermediate host utilization in the natural environment has, at least in part, a physiological basis. The degree to which different leeches are utilized as hosts may relate to the opportunity which they afford for transmission of A. minor to wildfowl definitive hosts.

Foraging activity of two species of predatory leeches exposed to active and sedentary prey.

The foraging activity of the freshwater leeches Nephelopsis obscura and Erpobdella punctata during acclimation to active or sedentary prey, starvation and refeeding was examined by filming over a 24 h cycle. For both species, the time of activity of individual leeches and the total number of leeches active were significantly correlated. Activity in the dark was significantly higher than in the light with the activity of N. obscura in the dark 16.2 times higher in terms of time and 6.7 times higher in terms of numbers of individuals moving than E. punctata. Large N. obscura were significantly more active than medium or small individuals and encountered more sedentary prey. With lower levels of activity E. punctata encounters and feeds on more active prey, and in lotic ecosystems its lower exposure to fish predation and drift is, at least partially, responsible for its numerical abundance over N. obscura. There were no significant differences in the activity of N. obscura or E. punctata fed on active or sedentary prey during either subsequent starvation of 1 to 10 d, or after refeeding, suggesting that unchanged foraging activity provides the optimun net energy gain during periods of change in prey type and availability.