Does body size difference in the leeches Glossiphonia complanata (L.) and Helobdella stagnalis (L.) contribute to co-existence?

The effect of predator and prey body size on the feeding success of the British lake-dwelling leeches Glossiphonia complanata and Helobdella stagnalis was examined in the laboratory, and any involvement of size difference between the leeches in allowing coexistence in the field assessed. G. complanata breeds in advance of H. stagnalis and maintains a body size advantage throughout their annual life-cycle. In experiments, conducted at 14 °C and a photoperiod of 16 hrs L: 8 hrs D, three size classes of leeches of each species were each exposed to each of three size classes of each of five prey species, viz. Tubifex sp., Chironomus sp., Asellus aquaticus, Lymnaea peregra and Potamopyrgus jenkinsi. For each prey species, three different types of experiments were performed: one leech exposed to four prey individuals; four leeches of the same species with sixteen prey; and two leeches of each species with sixteen prey. In the first experiment, all sizes of G. complanata were capable of feeding on all sizes of the prey types offered; the same was true for H. stagnalis with exceptions of feeding on large A. aquaticus and large L. peregra. For both species, but especially for G. complanata, there was a trend within each size class of leech for decreasing proportions of fed leeches with increasing prey size, and within each size class of prey for an increasing proportion of fed leeches with increasing leech size; however there were several exceptions to these trends. Both leeches fed extensively on Tubifex sp. but there were significant differences in the proportions feeding on other prey types; G. complanata fed more on A. aquaticus and the two snail species, and less on Chironomus, than H. stagnalis. The effect of increasing the number of leech individuals from one to four individuals, of the same or mixed species, had little effect on the proportion of leeches which had fed. It is concluded that large G. complanata will have access to large individuals of certain prey taxa denied H. stagnalis, which may lessen the intensity of interspecific competition.     

Winter sites and cold-hardiness of two gastropod species in a boreal river

Summary The overwintering sites and cold-hardiness of Gyraulus acronicus and Valvata piscinalis were investigated in a northern Swedish river subject to wide seasonal fluctuations in water-level and ice-cover. More than 95% of the population of young and older G. acronicus overwintered in the frozen hydrolittoral zone. No specimens of V. piscinalis were found in the frozen zone. The cold-hardiness in G. acronicus in unfrozen sites was maximal in November and early December. V. piscinalis was not cold-hardy at any time of the year. These interspecific differences in cold-hardiness accord with the differences in overwintering habitats.     

Diversity in Reproduction and General Morphology between Two Glossiphonia Species (Hirudinea) in Lake Esrom,Denmark*

According to Bennike (1943) the leech fauna in Lake Esrom, Denmark, includes two types of Glossiphonia complanata (L.), namely G. complanata typica Bennike, 1943 and G. complanata concolor (Apáthy, 1888). The results of the present investigation, which were based on material collected in 1975, 1976, and 1980, strongly indicated that we are dealing with two species in Lake Esrom, namely Glossiphonia complanata (L.) and G. (Clepsine) concolor (Apáthy). The two species have a rather similar life history, but G. complanata is on average larger than G. concolor. Differences in reproduction included size of eggs and timing of breeding, but the number of offspring seemed to be similar. Tank experiments revealed that all offspring of G. complanata had a conspecific parent, and likewise for G. concolor. The general appearance of the two species is significantly different, and the average ratio of body width to body height (W/H ratio) was ca. 30% higher for preserved individuals of G. complanata than for G. concolor. The ecological distribution of the two types, and the reliability of pigmentation as a diagnostical tool in leech systematics are discussed. Characters used for the identification of the species are included.     

Comparing the low‐salinity tolerance of Ulva species distributed in different environments

The green macroalgal genus Ulva (Ulvales, Ulvophyceae, Chlorophyta) is distributed worldwide from marine to freshwater environments. Comparative analyses of hyposalinity tolerance among marine, brackish, and freshwater Ulva species were performed by fluorescein diacetate viability counts. The subtidal marine species Ulva sp., collected from a depth of 30 m, showed the poorest tolerance to low salinity. This species died in 5 practical salinity units (PSU) artificial seawater or freshwater within 1 day. Its closely related species U. linza L. (an intertidal species) and U. prolifera Müller (a brackish species) showed varying tolerances to low salinity. After 7 days of freshwater exposure, the viability of U. linza L. decreased to approximately 20%, while U. prolifera Müller showed nearly 100% viability. The freshwater species U. limnetica Ichihara et Shimada, not yet found in coastal areas, was highly viable in seawater.     

Leech predation on juvenile freshwater snails: effects of size,species and substrate

Summary The leechGlossiphonia complanata does not appear to have substantial impact on snail populations, but this may be due to most studies focusing on adult snails rather than juvenile snails. In this study I investigated how predation rates ofG. complanata feeding on newly-hatched and juvenile snails was affected by snail species, snail size, snail density and substrate, in a laboratory experiment. Number of snails eaten increased with increasing density resulting in a type II functional response curve. Predation rates were higher when leeches were feeding onLymnaea emarginata than onPhysa gyrina, whereas there was no significant difference in predation rates when they were feeding onL. emarginata andHelisoma anceps. Sandy substrates and greater snail size resulted in decreased predation rates. Sand reduced movement speed ofG. complanata, which probably reduced encounter rates. Thus, there was a comparatively large effect of leech predation on newly-hatched snails, due to a high probability of encounter and high predation rates, but spatial and temporal refuges probably reduce the importance of leech predation as a structuring force in freshwater snail assemblages.     

Relative Desiccation Survival Potential of Two Root-Knot Nematode Species,Meloidogyne Incognita and M. Triticoryzae and Relationship With Their Habitat and Cuticle Characteristics*

Abstract

Horsfall, J. G. (Ed.): Annual Review of Phytopathology. Vol. 4. VII + 423 S. Palo Alto, 1966: Annual Reviews, Inc. Leinen, 9,00 $. Reviewed by K. Naumann.

Gregory, P. H. und Monteith, J. L. (Ed.): Airborne microbes. Seventeenth Symposium of the Society for General Microbiology held at the Imperial College, London April 1967. XII + 385 S., mit Abb. u. Tab. London, 1967: Cambridge University Press, Leinenrücken, 75 s. Reviewed by H. J. Müller.

Raper, J. R.: Genetics of sexuality in higher fungi. VIII + 283 S., mit Abb. u. Tab., New York, 1966: The Ronald Press Company, Leinen, 12,00 $. Reviewed by M. Schmiedeknecht.

Albrecht, F. O.: Polymorphisme phasaire et biologie des acridiens migrateurs. X + 194 S., 52 Abb. Paris, 1967: Masson et Cie, Éditeurs, karton., 50 F. Reviewed by R. Fritzsche.

Wigglesworth, V. B.: Insect physiology. VII + 134 S., 12 Abb., London, 1966: Methuen &; Co Ltd., brosch., 10 s 6 d. Reviewed by G. Schäller.

Machlis, L. (Ed.): Annual Review of Plant Physiology. Vol. 18. VIII + 480 S., mit Abb. u. Tab., Palo Alto, Ca., 1967: Annual Reviews, Inc., Leinen, 9,00 $. Reviewed by H. Wolffgang.

Newton, B. A. und Reynolds, P. E. (Ed.): Biochemical studie of antimicrobial drugs. (Sixteenth symposium of the Society for General Microbiology held at the Royal Institution, London, April 1966). X + 349 S., mit Abb. u. Tab., London, 1966: Cambridge University Press, Halbleinen, 60 s. Reviewed by H. J. Müller.

Pilet, P.-É.: La cellule, structure et fonctions. 406 S., 310 Abb.; 32 ganzs. Abb., Paris 1966: Schwarz-Weiß-Tafeln. Masson et Cie, Editeurs, brosch. 38 F. Reviewed by K. Schmelzer.

Ciba (Ed.): Dimecron 257 S. Basle, Switzerland, 1967: P.O. Box — CIBA — Kunststoff Reviewed by Horst Beitz.

Bellamy, L. J.: Ultrarot-Spektrum und chemische Konstitution. 2. Auflage, 325 S., 11 Abb., 23 Tab. Darmstadt, 1966: Dr. Dietrich Steinkopff Verlag, kart., 28,— DM Reviewed by Volker Müller.

Bahr, G. F.; Zeitler, E. H. (Ed.): Quantitative electron microscopy. 1965, VIII + 605 (1340) S., mit Abb. u. Tab., Leinen, 16,00 $, Baltimore (Md.), The Williams &; Wilkins Company. Reviewed by H. B. Schmidt.     

Competitive interactions between the lake-dwelling leeches Glossiphonia complanata and Helobdella stagnalis: an experimental investigation of the significance of a food refuge

The glossiphoniid leeches Helobdella stagnalis and Glossiphonia complanata co-exist on the stony shores of British lakes. Because both species have a similar life-style and are food limited, the question arises as to how coexistence persists. Laboratory experiments investigated if either leech has a competitive advantage on three foods, viz. oligochaete worms (Tubifex sp.), snails (Lymnaea peregra), and a worm-plus-snail mixture. A variety of densities with a range of ratios of the two leeches, and monospecific controls were used. The level of feeding ensured increasing food shortage with rising leech density. Experiments, conducted at 14° C, lasted 3 months. Regression values for growth against density in the controls indicated the occurrence of intraspecific competition in both leech species. Light mortality occurred at the highest densities. G. complanata gained significantly less weight in mixed leech cultures than in monospecific cultures at some of the highest densities when fed worms, but more weight when fed on snails. The opposite was true for H. stagnalis. When both prey types were provided, no differences at any density were observed for either leech. Differences in bodysize and feeding strategy between the leeches may be implicated in determining their feeding success on the prey types. Because the anti-predatory responses (e.g. shaking) exhibited by L. peregra are less when encountering an inactive than an active leech, the sit-and-wait strategy of G. complanata may aid snail capture. In contrast, the seek-out strategy of H. stagnalis, coupled with its relatively smaller size, may result in fewer successful captures. The active hunting strategy of H. stagnalis may be advantageous for the capture of oligochaetes which are relatively less mobile than snails. Offering both prey types simultaneously would have had an ameliorating influence on interactions between the two leeches. Findings provide support for the hypothesis that long-term co-existence between the two glossiphoniids in British lakes may depend, in part at least, on the occurrence of a snail food refuge for G. complanata.     

On the identities of some neglected species of Grimmiaceae from Îles Kerguelen

Taxonomic status of five species of Grimmia Hedw. (G. minuta Müll.Hal., G. suborthotrichacea Müll.Hal., G. defoliata Müll.Hal., G. genuflexa Müll.Hal., and G. orthotrichacea Müll.Hal.) is appraised. All these species correctly belong within the genus Bucklandiella Roiv. They are actually inseparable from one another and represent a single species for which B. orthotrichacea (Müll.Hal.) Bednarek-Ochyra & Ochyra is chosen as the final name. The remaining four names are considered its synonyms, all but G. genuflexa being new. All the names are lectotypified and some details of the leaves of G. minuta and G. defoliata are illustrated.     

The freshwater fauna of Macquarie Island, including a redescription of the endemic water-flea Daphnia gelida (Brady) (Anomopoda: Crustacea)

The freshwater invertebrate fauna (excluding the Protozoa) of Macquarie Island is collated. This includes two Platyhelminthes, two Gastrotricha, three Tardigrada, 41 rotifera, at least eight Nematoda, nine Annelida, and 21 Arthropoda. The latter comprises six species of Anomopoda, two Copepoda, two Ostracoda, an Isopoda, five Acarina, and at least five species of Insecta with aquatic or semi-aquatic larvae. The freshwater Anomopoda (Cladocera) of Macquarie Island are re-evaluated, six species are now recognized and the largest, identified as Daphnia gelida (Brady), is redescribed. The records of both Alona weinecki Studer and Pleuroxus macquariensis Frey are confirmed, while that of Macrothrix hirsuticornis Norman and Brady is accepted with some reservations. Alona quadrangularis (O.F. Müller) is re-instated and records of Chydorus sphaericus O.F. Müller ascribed to C. patagonicus Ekman.     

Mitochondrial morphogenesis and ultrastructure of basidiomycetes from genera Agaricus and Pleurotus

Supravital study of rhodamine-stained mitochondria in cells of aerial and submerged micelium of 31 strains from 9 species from genus Agaricus (A. arvensis Schaeff., A. bisporus (Lange) Imbach, A. bitorquis (Quel.) Sacc., A. campestris L., A. excellens, (F.H. Müller) F.H. Müller, A. macrocarpus (F.H. Müller) F.H. Müller, A. silvaticus Schaeff., A. silvicola (Vittad.) Peck, A. xanthodermus Genev) and of 2 strains from 2 species from genus Pleurotus (P. ostreatus (Jacg.) P. Kumm., P. pulmonarius (Fr.) Quel.) was carried out. Mitochondrial morphogenesis in micelial cells of species from Agaricus and Pleurotus genera has many common features in distribution of mitochondria in micelial cells both under the favorable growth conditions and during chondriom reorganization (fission and fragmentation of mitochondria to small subunits) under unfarovable growth conditions and during aging. During the balanced growth of mycelium of heterokaryotic strains from genera Agaricus and Pleurotus for 7–14 days on agar media as well as during cultivation of mycelium of oyster mushroom and several strains of field mushroom in submerged culture, distribution of mitochondria by the type 1 (small granular mitochondria in the apical zone—1, long rod-like mitochondria in the subapical zone—2 and short rod-like and granular mitochondria formed as a result of fragmentation of rod-like mitochondria in mature mycelium cells—3) was observed. Under unfarovable growth conditions (starvation), in mycelium cells of homokaryotic strains of champignon, during long cultivation of all strains and species from the studied genera and during cultivation on liquid wort, for majority of champignon, distribution of mitochondria by the type 2 was observed (sphere-like mitochondria in all cells of the studied mycelium zones). Mitochondrial profiles at ultrastructural level had specific features, such as associations of the outer mitochondrial membrane with cytoplasmic ribosomes and changes in cristae structure. The preliminary test for apoptosis-like phenotype of the submerged mycelium cells of Bs94 champignon that hardly grows in the submerged culture gave positive result. Thus, mitochondrial morphogenesis in mycelium cells of Agaricus and Pleurotus species under different conditions and terms of cultivation occurs similarly and is determined by a complex of physiological and biochemical processes reflecting the state of mycelium cells.     

Distribution Patterns and Habitat Characterization of Elmidae and Hydraenidae (Insecta: Coleoptera) in the Weidlingbach Near Vienna,Austria

A total of 870 adult and 831 larval Elmidae and Hydraenidae were caught from September 1995 to September 1996 at the Weidlingbach, a fourth order tributary of the Danube near Vienna, Austria, using a Heß sampler at 14 sampling stations from source to mouth. Elmis maugetii (Latreille ) and Riolus subviolaceus (Müller ) accounted for 66.3% of the total, whereas Hydraena gracilis (Germar ) was the most abundant Hydraenidae species. Based on head width, instars 1–6 were collected in E. maugetii, instars 2–6 in R. subviolaceus and instars 3–6 in Limnius volckmari (Panzer ) and Riolus cupreus (Müller ); from the remaining species, only instars 4–6 were sampled. E. maugetii was most abundant on coarse, moss-covered substrates (median = 22.2 mm) exposed to high water velocity (median = 69.4 cm/s; range = 6.0–117.6 cm/s); the latter was also true for R. subviolaceus although it favoured smaller sediment grain sizes (median = 10.7 mm). Sites exposed to only moderate flow and with abundant filiform algae were preferred by Esolus parallelepipedus (Müller ) and L. volckmari, whereas the Hydraenidae species, Esolus angustatus (Müller ), R. cupreus and Oulimnius tuberculatus (Müller ) were collected mostly at sites with moderate current speed and abundant moss-covered pebbles of various size. Species richness and population density increased from source to mouth. At the spring sampling site Elmidae and Hydraenidae were completely lacking.     

A revision of the moss genus Gymnostomiella Fleisch.

Abstract

A taxonomic revision of the moss genus Gymnostomiella Fleisch. recognizes five species and one variety, viz. G. burmensis Bartr., G. erosulum (C. Müll. ex Dus.) Arts, G. longinervis Broth., G. monodii P. Yarde, G. vernicosa (Harv.) Fleisch. var. vernicosa and G. vernicosa var. tenerum (C. Müll. ex Dus.) Arts. Gymnostomiella tenerum (C. Müll. ex Dus.) Arts is reduced to a variety of G. vernicosa and G. tanganyikae De Sloover is reduced to synonomy with G. erosulum.     

Cingula globuloides sp.n. (Gastropoda, Prosobranchia) from Northern Atlantic

Warén, A. (Department of Zoology, University of Gothenburg, Göteborg, Sweden.) Cingula globuloides sp.n. (Gastropoda, Prosobranchia) from northern Atlantic. Zool. Scripta 1(3–4): 191–192, 1972. –Cingula globuloides sp.n. is described from the northern Atlantic. This species has earlier been confused with Cingula globulus (Möller, 1842). The distinctive characteristics and distribution of C. globulus are given.     

Bestimmung von Chloratrückstanden im Boden

Abstract

Kozubov, G. M.; Danilova, M. F.: Atlas ultrastruktury rastitel nych kletok 295 S., 142 Tafeln. Petrozavodsk: 1972. Reviewed H. M. Müller.

Fritzsch, W.; Bremer, R.: Bienengesundheitsdienst, 1. Aufl. 200 S., 62 Abb. Jena: VEB Gustav Fischer, 1975. Reviewed W. Lehmann.

Schumakow, I. M.; Fedorintschik, N. S.; Gussew, G. W.: Biologische Pflanzenschutzimittel. 205 S., 13 Abb., Berlin, VEB Dt. Landwirtschaftsverl., 1976. Reviewed Th. Wetzel

Grimstone, A. V.; Skaer, R. J.: A guidebook to microscopical methods 134 S., 3 Abb. London: Cambridge Univ. Press, 1972. Reviewed H. M. Müller.     

Length–weight relationship of Rhinobatos horkelii Müller & Henle, 1841 and Zapteryx brevirostris (Müller & Henle, 1841) off Brazil,southwestern Atlantic Ocean

This study reports the length–weight relationships (LWRs) for two elasmobranch species, Rhinobatos horkelii Müller & Henle, 1841 and Zapteryx brevirostris (Müller & Henle, 1841) collected from the southwestern Atlantic, off Brazil. Both are considered endangered species. The LWR data can be taken into consideration for further management and conservation plans.     

Development of a zooplankton community including <Emphasis Type="Italic">Heterocope saliens</Emphasis> Lillijeborg in an experiment with hydrophytes

The influence of the submerged plants Ceratophyllum demersum L. and Elodea canadensis Michx. and the floating plant Hydrocharis morsus-ranae L. on the species composition and quantitative parameters of a zooplankton community was studied experimentally. Among submerged vegetation, the development of the predaceous calanid Heterocope saliens Lilljeborg was suppressed. An increase in the number of zooplankter species was observed in all experimental ecosystems with hydrophytes. The species similarity of zooplankton was higher between communities with plants of the same ecological group than with plants of different groups. The highest average zooplankton biomass, as determined by the abundance of Daphnia longispina O.F. Müller and Simocephalus vetulus (O.F. Müller), was observed in experiments with Elodea. The highest average abundance over the experimental period was recorded among Ceratophyllum, where the abundance of Rotifera, chydorids, and copepods common in hydrophyte beds was higher than in other versions of the experiment.     

The relationship between ethnology and social anthropology 1

African Miniatures. The Goldweights of the Ashanti. Margaret Webster Plass. Lund Humphries, London 1967. 26 pp., 166 ill.

Anthropologists in the Field. Edited by D. G. Jongmans and P. C. W. Gutkind. Series: Non‐European Societies, nr 6. Royal van Gorcum &; Comp. N. V. Assen 1967. 277 pp. Price cloth Hf 32.50.

Races of Africa. C. G. Seligman. 4 ed. Opus 9 (Oxford Paperbacks University Series). Oxford University Press, London. 1966. 177 pp.

Hausa ba dabo ba ne. A collection of 500 Proverbs translated and annotated by A. H. M. Kirk‐Greene. Ibadan. Oxford University Press London 1966 84 pp. Price 5/3 d.

Human Evolution. An Introduction to Man's Adaptations. Bernard G. Campbell. Aldine Publishing Company, Chicago 1966. 425 pp., 135 ill. Price $ 8.95.

Human Evolution. Readings in Physical Anthropology (2nd cd.) Noel Korn and Fred W. Thompson (editors). Holt, Rinehart and Winston, Inc., New York 1967, 466 pp. figs. $ 4.95.

Caste and Race: Comparative Approaches. A Ciba Foundation Volume. Ed. by Anthony de Reuck and Julie Knight. J. &; A. Churchill Ltd., London 1967. 348 pp. Price 60 s.

The American Negro. A Study in Racial Crossing. Melville J. Hersko‐vits. A Midland Book, Indiana University Press, Bloomington 1964. 92 pp. Price $ 1.65.

Strangers to the City: Urban Man in Jos, Nigeria. Leonard Plotnicov. University of Pittsburgh Press, Pittsburgh 1967. 320 pp. Price hardbound $ 6.95, paperbound $ 2.95.

Ozeanien. Paul Collaer. Musikgeschichte in Bildern, Hrsg. von Heinrich Besseler und Max Schneider, Band I: Musikethnologie, Lieferung 1. VEB Deutscher Verlag für Musik, Leipzig 1965. 234 S., 178 Abb.

A Study of Polyandry. H. R. H. Prince Peter of Greece and Denmark. Mouton &; Co. The Hague 1963. 606 pages, 44 photographs, 4 figs., 2 sketches, 6 maps, 48 genealogical tables. Cloth. Price: Glds. 68.‐(=ab. US $ 19.00, £ 6.16.‐, DM 75.50, 94.50 F).

African Music. A Briefly Annotated Bibliography. Compiled by Darius L. Thieme. Library of Congress, Reference Department, Music Division, Washington 1964. 55 pp. 45 cents.

Tribes and forms in African Art. William Fagg. Methuen &; Co. Ltd., London 1965. 122 Pl. 6 Guineas net.     

Book reviews

Social Anthropology in Melanesia. A. P. Elkin. (166 pp., 1 map. Oxford University Press, London 1953. A. £. 27/6).

Social Anthropology in Polynesia. Felix M. Keesing. (126 pp. Oxford University Press, London 1953. A. £. 27/6).

Field Notes on Indonesia: South Celebes, 1949–50. Raymond Kennedy. (269 pp., 1 fig., 7 maps and plans. Published by Human Relations Area Files, New Haven 1953. $ 2.00).

Die Erscheinungsformen des Männerhauses und das Klubwesen in Mikro‐nesien. Eine ethno‐soziologische Untersuchung. Erhard Schlesier. (208 pp., 1 map. Mouton & Co., ‘s‐Gravenhage 1953.)

Changing Lapps. A Study in Culture Relations in Northernmost Norway. Gutorm Gjessing. (Monographs on Social Anthropology, No. 13. London 1954.)

Ausstellung Bauernwerk der alten Weh. Europa‐Asien‐Afrika. Katalog (Veröffentlichungen zum Archiv für Völkerkunde, Band 2. 112 pp. Wien 1954).     

Vittia salina L.Hedenäs & J.Muñoz,sp. nov., a new moss from Argentina

Abstract

A survey of the species of Campylopus Brid. reported from Sri Lanka (Ceylon) is presented. Of the 34 species that have been reported from this Island 16 are accepted at present. Campylopus nilghiriensis (Mitt.) Jaeg. is identical partly with C. goughii (Mitt.) Jaeg., partly with C. zollingerianus (C. Müll.) Bosch &; Lac., C. pseudogracilis Card. &; Dix. with C. goughii (Mitt.) Jaeg., C. caudatus (C. Müll.) Mont., C. reduncus (Reinw. &; Hornsch.) Bosch &; Lac. and C. trachythecius (C. Müll.) Jaeg. with C. comosus (Reinw. &; Hornsch.) Bosch &; Lac., C. herzogii Broth., C. subtricolor Lor. and probably also C. nodijlorus (C. Müll.) Jaeg. with C. aureus Bosch &; Lac., C nietneri (C. Müll.) Jaeg. with C. involutusz (C. Müll.) Jaeg., C. subgracilis Ren. &; Card. ex Gangulee and C. latinervis (Mitt.) Jaeg. with C. gracilis (Mitt.) Jaeg., and C. laetus (Mitt.) Jaeg. with C. savannarum (C. Müll.) Mitt. C. pterotoneuron (C. Müll.) Jaeg. is reduced to a variety of C. umbellatus (Arn.) Par. The occurrence of C. exasperatus Brid. on Sri Lanka could not be confirmed. Campylopus flagelliferus (C. Müll.) Jaeg. is reported as new to Sri Lanka.     

Interactions between the leech Glossiphonia complanata and its gastropod prey

Summary Predator-prey interactions between the predatory leech, Glossiphonia complanata, and its gastropod prey were investigated in laboratory experiments, including behavioural observations with the aid of time-lapse video technique. Six gastropod species were investigated, viz. Lymnaea peregra, Planorbis planorbis, Physa fontinalis, Ancylus fluviatilis, Bithynia tentaculata, and Theodoxus fluviatilis. The species studied exhibited anti-predator defences, which had their maximum efficiency at different stages of encounter with G. complanata. The activity of B. tentaculata decreased with increasing leech activity, but was relatively higher when food was present than when not. Handling times were dependent on the time elapsed since the previous meal was captured (intercatch interval), which in turn was related to the size of the previous prey. Handling time was also related to the size of both predator and prey. The capture efficiency was high for small prey and the leeches spent more time in patches with higher yield. They were, however, unable to discriminate between patches of different prey density.