A COMPARATIVE STUDY OF LACUNA VINCTA AND LACUNA PALLIDULA (GASTROPODA: PROSOBRANCHIA) IN LITTORAL ALGAL TURFS

A comparison is made of the number of individuals of Lacunavincta and L. pallidula associated with several red algae betweenJune 1978 and June 1980 at Cooskeen Cove, Bantry Bay, Ireland.Both are annuals and exhibit similar seasonal cycles of abundance.Planktonic larvae of L. vincta settle between eary May and July,resulting in summer maxima followed by heavy mortality. Survivorshipcurves of L. vincta were similar in both 1978 and 1979. Juvenilemortality is very high resulting in less than 2% of the populationsurviving at commencement of the spawning period in January.In L. pallidula hatching occurs from April to July and populationstructure between April and September in G. stellata indicatesa succession of cohorts which remain for only short periodsbefore moving to the adult habitat, Fucus serratus. Sex-ratioand sexual dimorphism in shell height was investigated in bothspecies. Mean growth rate of penis and shell for male L. vinctabetween October and January was compared for the 1978 and 1979populations. Measurements on L. pallidula are also given. Acomparison of the spawn in both species was made. (Received 20 June 1981;     

<Emphasis Type="Italic">Lacuna vincta</Emphasis> (Mollusca,Neotaenioglossa) herbivory on juvenile and adult <Emphasis Type="Italic">Nereocystis luetkeana</Emphasis> (Heterokontophyta,Laminariales)

Herbivory can be an important factor structuring coastal algal communities. Herbivores may preferentially graze particular algal species or tissue types. Mesograzers, despite their small size, can critically weaken kelp thalli and impact entire kelp beds. We propose that when kelp beds are composed of several kelp cohorts, mesograzers will selectively choose to inhabit younger plants and grazing activities will have a greater impact on younger plants. This study investigated the effects of grazing by the littorinid gastropod, Lacuna vincta, on different age classes of the bull kelp, Nereocystis luetkeana by (1) testing food preference of L. vincta on juvenile, first-year adult, and second-year adult Nereocystis blades in the laboratory, (2) determining substrate (blades of different ages) preference of L. vincta in the laboratory, and by (3) estimating in-situ herbivore abundances and densities on juvenile and adult Nereocystis. Results demonstrated that grazing by L. vincta produced greater damage on juvenile than older Nereocystis tissues. Although L. vincta did not select juvenile versus older kelps as substrate in the laboratory, in situ surveys showed that differences existed between age classes with higher L. vincta densities on juvenile than adult kelp. We conclude that at a local scale, L. vincta can be an important structuring factor in Nereocystis populations due to its high density and grazing ability. Handling editor: K. Martens     

Response of a native,herbivorous snail to the introduced seaweed <Emphasis Type="Italic">Sargassum muticum</Emphasis>

The role of native consumers in mediating biological invasions is poorly understood. In theory, there are reasons to expect both strong and weak effects of native consumers on non-native species. However, non-native ranges may include multiple regions or even continents, each with its own suite of consumers and invader–consumer interactions may play out differently in different places and times. In this Washington State (USA) study we found that the common herbivorous snail Lacuna vincta was 2–9 times more abundant on the non-native seaweed Sargassum muticum, compared to native kelps. Choice feeding trials with fresh tissue and artificial foods both suggest that S. muticum is a preferred food for Lacuna vincta. Lab experiments indicated that L. vincta did not experience diminished predation by two common predators on Sargassum muticum compared to native kelp hosts. Our results suggest that Sargassum experiences considerable herbivory by Lacuna vincta in our study region, a conclusion that is consistent with previous work and our own field observations. In our system, L. vincta and S. muticum have been coexisting in the same habitats for at least 50 years and available data suggest that it acquired a preference for S. muticum more than 30 years after the initial invasion. Comparison of our results to recent work on Sargassum–herbivore interactions in Europe suggests that the response of native consumer communities to S. muticum varies both within and among regions. Geographic and temporal variation in the response of native consumers are likely to be hallmarks of many large-scale invasions.     

GRAZING IMPACT OF,AND INDIRECT INTERACTIONS BETWEEN MESOGRAZERS ASSOCIATED WITH KELP (LAMINARIA DIGITATA)1

Little is known about the indirect effects of nonlethal grazing impacts in mesograzer–seaweed interactions. Using laboratory experiments, the effect of grazing by the seasonally abundant kelp‐associated gastropod Lacuna vincta on subsequent kelp consumption by one kelp‐associated (Idotea granulosa) and one nonassociated species of isopod (I. emarginata) was determined. Measurements of the toughness and elemental composition of different parts of the sporophyte of Laminaria digitata (Huds.) J. V. Lamour., as well as grazer‐induced changes in the palatability of the blade, were conducted to explore possible mechanisms of indirect effects. In situ grazing pressure was the highest between July and September, with the blade being the preferred part of the kelp sporophyte, despite missing differences in the elemental composition among kelp parts. The laboratory experiments supported our hypotheses in that kelp consumption by both species of isopods was lower on intact than on L. vincta–damaged areas of the blade. This pattern was not caused by grazing‐induced changes in blade palatability. Instead, the observed increase in isopod consumption following grazing by L. vincta resulted more likely from the combined effects of a reduction in the toughness of L. vincta–damaged kelp blades and some unknown gastropod cue(s). These results suggest that kelp‐associated and nonassociated mesograzers may benefit from the nonlethal grazing impact of L. vincta due to changes in physical traits of the seaweed. Thus, the nonlethal grazing impact by one species of mesograzer can positively modify the trophic interactions between kelp and other potential competitors, suggesting that the interactions among mesograzers might be more complex than previously assumed.     

Epiphyte and herbivore interactions impact recruitment in a marine subtidal system

Marine assemblages are influenced by the rate and timing of species settlement and recruitment. Both abiotic factors and biotic interactions can impact recruitment rates of marine species in a variety of systems. However, the impacts of species which recruit at the same time upon each other are less well understood. We investigated the relationship between the recruitment of Lacuna vincta, a small (<6 mm shell diameter) marine snail, and two species of algal epiphytes, the native Ceramium virgatum and the invasive Neosiphonia harveyi, in the shallow subtidal zone of Narragansett Bay, Rhode Island. All three species exhibit peak recruitment densities during two months in the summer. We found that the presence of algal epiphytes facilitates the recruitment rate of L. vincta, regardless of the epiphyte species composition. We also found a positive relationship between the number of L. vincta present and epiphyte recruitment, which is disproportionately driven by higher recruitment of N. harveyi than C. virgatum. Understanding recruitment dynamics and interactions is vital to effectively mitigate the effects of and adaptations to changes due to the establishment of non-native species.     

Biological aspects and life tables of the predacious mites,Typhlodromips swirskii (Athias-Henriot) and Euseius scutalis (Athias-Henriot) feeding on two scale insect species and plant pollen

Biological aspects and life table parameters of the predacious mites, Typhlodromips swirskii (Athias-Henriot) and Euseius scutalis (Athias-Henriot) (Acari: Phytoseiidae) consuming eggs of the Maskell scale insect, Insulaspis pallidula (Green) and the red date scale insect, Phoenicococcus marlatti Cockerell (Homoptera: Diaspididae, Phoenicococcidae) as well as pollen grains of date palm, Phoenyx dactylifera L. were determined under laboratory conditions. The life cycle and pre-oviposition period of T. swirskii were the shortest, while the oviposition period and female longevity were the longest as well as the egg production was the highest when fed on pollen compared with eggs of I. pallidula and P. marlatti. On the other hand, the life cycle, pre-oviposition and oviposition periods as well as the female longevity of E. scutalis were the best when devoured P. marlatti followed by pollen and I. pallidula. However, the total and daily fecundity of E. scutalis were the highest after consuming pollen compared with eggs of P. marlatti and I. pallidula. The sex ratio of females to total in the progeny of T. swirskii and E. scutalis was the highest when consumed I. pallidula followed by pollen and P. marlatti. Life table parameters were the most favourable for T. swirskii and E. scutalis feeding on date palm pollen compared with eggs of I. pallidula and P. marlatti.     

Allozyme analysis ofLuzula sect.Luzula (Juncaceae) in Ireland: Evidence of the origin of tetraploids

Luzula campestris, L. pallidula and tetraploi plants of this section from Ireland were studied electrophoretically. A hypothesis of alloploid origin for the Irish tetraploids from a hybrid betweenL. campestris andL. pallidula, based on the morphology, and karyology of the relevant taxa, has been tested. The presumed parental taxa are divergent in several loci,L. pallidula being highly homozygous andL. campestris moderately heterozygous. The Irish tetraploid combines the alleles of the putative parents, has no unique alleles, and exhibits a high frequency of heterozygotes, inAdh-2 andGpi-1, with invariably additive patterns. The Irish tetraploid has a low genotype diversity. The allozyme data support the hypothesis of alloploid origin for the Irish tetraploid withL. campestris andL. pallidula as possible parents.     

RADULAR PRODUCTION RATES IN TWO SPECIES OF LACUNA TURTON (GASTROPODA: LITTORINIDAE)

The molluscan radula is a dynamic organ, both in terms of itsuse and production. New rows of teeth are constantly producedat the posterior end of the radula, while older, worn teethare shed anteriorly, producing a dynamic equilibrium. We useda cold-shock to mark the radular ribbon and measure tooth rowproduction rates in two gastropod species, Lacuna vincta (Montagu)and L. vanegata Carpenter. We found that the average tooth rowproduction rate at 10–11°C did not differ betweenthese two species, and was 2.94 (SE = 0.002) rows per day forLacuna vincta and 2.97 (SE = 0 002) for L. vanegata Inter-individualvariability in production rate was very low, and was correlatedwith shell length, smaller individuals had slightly higher productionrates. The total length of the radular nbbon varied greatlyamong individuals, ranging from 47 to 94 (2.57 to 5.68 mm) rowsin L vincta and 53 to 99 rows (2.80 to 7.14 mm) in L vanegata,and was only somewhat correlated with the length of the shelLThis great variability will result in large differences amongindividuals in the time it takes to replace the radula totally,from 14.96 to 35.44 days in L vincta and from 17 43 to 39 69days in L. vanegata. (Received 1 September 1995; accepted 20 November 1995)     

Isolation and characterization of microsatellite loci in Monolepta vincta Gerstaecker, 1871 (Coleoptera,Chrysomelidae, Galerucinae)

Nine polymorphic microsatellite markers of Monolepta vincta Gerstaecker, 1871 (Coleoptera, Chrysomelidae) have been characterized. An analysis of 140 individuals demonstrated the high degree of polymorphism for these loci with a mean number of 10.6 alleles per locus. Primer sets were also tested in M. usambarica Weise, 1903, M. vilis Weise, 1924 and an as yet undescribed Monolepta sp. Some primer sets yielded amplification products in these closely related species with a detectable degree of polymorphism. The markers will be used for a population genetic study of M. vincta populations in the Kakamega Forest, Kenya.     

Spatio‐temporal patterns and interactions with honeydew‐producing Hemiptera of ants in a Mediterranean citrus orchard

• 1 The role of ants in the citrus agro‐ecosystem is controversial and understanding their ecology may help to clarify their function. The present study determined the daily and seasonal foraging patterns, the spatial distribution, the feeding sources and the associations with honeydew‐producing Hemiptera of three ant species that forage in citrus canopies.
• 2 The dominant ants Pheidole pallidula (Nylander) (Myrmicinae) and Lasius grandis Forel (Formicinae) foraged in mutually exclusive territories within the field, although they both shared their territory with the subordinate Plagiolepis schmitzii Forel (Formicinae), a distribution pattern known as ‘ant mosaic’.
• 3 The observed mean overlap for the spatial distribution was significantly lower than the generated by null models, providing strong evidence of spatial interspecific competition, especially between the two dominants.
• 4 Ants ascended to the canopies from April until November. Colony nutritional requirements and temperature probably shape their seasonal foraging patterns. The daily activity pattern of P. schmitzii was strictly diurnal, whereas L. grandis and P. pallidula were active during the entire day.
• 5 The ants' diet in the canopies consisted principally of hemipteran honeydew, whereas citrus nectar and predation/scavenging did not represent important food sources. More than 60% of the total honeydew sources and 100% of the citrus mealybug Planococcus citri colonies were tended by ants during spring and summer.

     

Diversity and structure of ant communities associated with oak,pine, eucalyptus and arable habitats in Portugal

Summary In central Portugal, 28 species of ants were found in oak, 25 in pine, 35 in eucalyptus and 12 in arable habitats, a total of 43 species. They include five numerically dominant species, the exotic Argentine ant.Linepithema (Iridomyrmex) humile and four native species,Crematogaster scutellaris, Pheidole pallidula, Tapinoma nigerrimum andTetramorium hispanicum. L. humile occurred in 34% of sampled sites. When present, it was abundant in all three arboreal habitats, where it was associated with strikingly decreased ant species richness and equitability. Such diversity was greater inL. humile-colonised arable habitats, where the ant was much less abundant than in the arboreal habitats.WhereL. humile was absent,C. scutellaris andP. pallidula were usually co-dominants in oak and pine, andT. nigerrimum andT. hispanicum in the arable habitat, but all were absent or rare in eucalyptus. Ants were numerically least abundant in eucalyptus but, in the absence ofL. humile, species richness was greater and the community more equitable than in the other habitats.L. humile-absent arable habitats supported the poorest and least equitable ant community.     

Tetraploids inLuzula multiflora (Juncaceae) in Ireland: Karyology and meiotic behaviour

Populations ofLuzula multiflora s.l. in Ireland were examined karyologically. Plants from 14 populations were invariably tetraploid with 2n=24. Chromosomes of the tetraploid are of AL type (true tetraploidy). Meiosis of the tetraploids is of the same type as described for otherLuzula taxa in the literature. In meiosis, 12 bivalents are regularly formed. A hypothesis based on the morphological and allozyme data, that the tetraploids are of alloploid origin, is supported by the present results. Meiosis in an artificial hybrid between the presumed parental taxa,L. campestris andL. pallidula, was studied; a certain tendency towards chromosome doubling was observed. The geographical distribution of theL. multiflora cytotypes is also discussed.     

Contents of the poison apparatus of some species of Pheidole ants

Four Old World species of Pheidole ants contain different mixtures of farnesene-type hydrocarbons in their poison apparatus, and the mixture is different between the minor and major workers within a species. A bishomofarnesene (C₁₇H₂₈) provides approximately half of the secretion of the Dufour glands of minor workers of Pheidole pallidula. (Z,E)-α-Farnesene constituted 96% of the Dufour secretion of major workers of P. pallidula, but only 20% of that of minors. The Dufour glands of minor workers of Pheidole sinaitica contain a mixture of farnesene homologues with (Z,E)-α-farnesene and the bishomofarnesene also found in P. pallidula predominant. The mixture in major workers was similar but had, in addition, a small amount of (E)-β-farnesene. The Dufour glands of Pheidole teneriffana minors contain chiefly the same bishomofarnesene found in P. pallidula and P. sinaitica while major workers contain (Z,E)-α-farnesene. Pheidole megacephala minor workers contained small amounts of eight farnesenes, while major workers contained essentially no farnesenes. The poison glands of minor workers of P. pallidula contain 3-ethyl-2,5-dimethylpyrazine. No pyrazine compounds were found in the major workers of P. pallidula or the minor workers of P. sinaitica. The poison glands of the major workers of P. sinaitica contained larger amounts of tetra-substituted pyrazines. No pyrazines were found in the poison reservoirs of major or minor workers of P. teneriffana or P. megacephala.     

THE EGG MASS OF LITTORINA OBTUSATA AND LACUNA PALLIDULA (GASTROPODA : PROSOBRANCHIA)

The egg masses of Littorina obtusata and of Lacuna pallidulahave been compared with regard to size, shape, egg number, eggsize and substratum. The structure and histochemistry of thespawn of the two species has been investigated and observationson the laying process in L. obtusata are also recorded. ^* Present address: Portway School, Penpole Lane, Shirehampion,Bristol, BS11 0EB. (Received 12 October 1977;     

Effect of park age,size, shape and isolation on ant assemblages in two cities of Southern Spain

In the context of conservation biology, we have searched for the most influential characteristics of urban parks on ecological diversity. In this study, therefore, we studied the ant community of 24 parks in two cities of Southern Spain (Cordoba and Seville). In total, 46 species were found. Abundant and widely distributed species were synanthropic ones, such as Lasius grandis, Pheidole pallidula or Tapinoma nigerrimum, and exotic species such as Cardiocondyla mauritanica. However some parks also harbored natural habitat‐preferring species. Park size, shape and distance to city outskirts were the most important predictors of species richness and diversity. Likewise, park age influenced the composition of the ant fauna.     

Interactional behaviors of the parasitic beetle Paussus favieri with its ant host Pheidole pallidula: the mimetic role of the acoustical signals

The social parasitic beetle Puussus favieri(Coleoptera,Carabidae,Paussini)performs different types of stridulations,which sclectively mimic those emitted by dif-ferent ant castes of its host Pheidole pallidula(Hymenoptera,Formicidae,Myrmicinae).However,the significance of this acoustical mimicry for the success of the parasitic strat-egy and the behaviors elicited in the host ants by stridulations was unknown.We reared Paussus favieri in Pheidole pallidula colonies and filmed their interacting behaviors.We analyzed in slow motion the behavior of ants near a stridulating beetle.We analyzed sep-arately trains of pulse(Pa+Pb,produced by repeated rubbings)and single pulse(Pc,produced by a single rubbing)of stridulations,clearly recognizable from the shaking up and down of the beetle hind legs.and associated them with differcent ant responscs.The full repertoire of sounds produced by P:favieri elicited benevolent responses both in workers and soldiers.We found that different signals elicit different(sometimes multiplc)bchaviors in ants,with different frequency in the two ant castes.However,Pc(alone or in conjunction with other types of pulses)appears to be the type of acoustic signal mostly responsible for all recorded behaviors.These results indicate that the acoustic channel plays a pivotal role in the host-parasite interaction.Finding that a parasite uses the acoustical channel so intensively,and in such a complicated way to trigger ant bchaviors,indicates that acoustic signals may be more important in ant societies than commonly recognized.     

An Ecological Study of the Fauna Inhabiting the Sublittoral Marine Alga Saccorhiza polyschides (Lightf.) Batt.

Summary The animals found on the fronds of the laminarian alga Saccorhiza polyschides are described. The sporophytes supported a fauna which was distinct from that of the surrounding rock, but was basically similar to that of other laminarian algae. Several animal species were however, much more abundant on S. polyschides than on other laminarians. A number of species were found to have a localised distribution on the host plant. The distribution of the epifauna on the alga seems to be chiefly the result of factors in the external environment particularly the degree of water movement and of silting. The epifauna varied in abundance and composition at different sites. In localities exposed to excessive water turbulence only a few species survived, although the gastropods Patina pellucida and Lacuna vincta were at their most abundant in such localities. Marked seasonal variations in the composition of the epifauna were found at Port Erin, Isle of Man, over a period of two years. The variations were related to both the seasonal behaviour of the animal species and to the annual cycle of growth and decay exhibited by the host plant. It is clear that the plant and its epifauna are each an important factor in the ecology of the other.

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Zusammenfassung Die Tiere, die auf den Wedeln der Laminaria-Alge Saccorhiza polyschides gefunden wurden, werden beschrieben. Die Sporophyten ern?hrten eine Fauna, die sich von der auf dem benachbarten Gestein unterschied, aber im Grunde der anderer Laminaria-Algen ahnelte. Verschiedene Tierarten waren jedoch viel zahlreicher auf S. polyschides als auf anderen Laminaria. Eine Reihe von Arten fanden sich an einzelnen Stellen auf dem Wirt. Die Verbreitung der Epifauna auf der Alge scheint in erster Linie das Ergebnis von Faktoren der Umwelt zu sein, v.a. des Grades der Wasserbewegung und der Verschlammung. Die Epifauna ver?nderte sich in Fülle and Zusammensetzung an verschiedenen Stellen. In Lokalitaten, die ausserordentlicher Wasserturbulenz ausgesetzt waren, überlebten nur ein paar Arten, obwohl die Gastropoden Patina pellucida und Lacuna vincta in solchen Lokalit?ten am h?ufigsten vorkamen. Deutliche jahreszeitliche Ver?nderungen in der Zusammensetzung der Epifauna fanden sich in Port Erin, auf der Insel Man, über einen Zeitraum von zwei Jahren. Die Ver?nderungen standen im Zusammenhang mit dem jahreszeitlichen Verhalten der Tierarten und dem Jahreszyklus von Wachstum and Zerfall, der von der Wirtpflanze gezeigt wird. Es ist klar, dass die Pflanze and ihre Epifauna beide einen wichtigen Faktor in der ?kologie der Anderen darstellen.

     

A revision of West Palaearctic species of the Micropsectra atrofasciata species group (Diptera: Chironomidae)

Phylogenetic relations among selected Micropsectra (Diptera: Chironomidae) species are inferred using mitochondrial COII gene sequences and morphological characters. Both maximum parsimony and Bayesian analyses indicate a monophyletic atrofasciata species group. However, some species morphologically similar to M. atrofasciata (Kieffer) in the adult male, i.e. M. appendica sp. nov. and M. logani (Johannsen), are placed outside the atrofasciata group in the gene trees. The phylogenetic hypotheses based on parsimony analyses of the combined molecular and morphological data sets weakly support a monophyletic atrofasciata group including M. appendica sp. nov. and M. logani if third positions in the COII gene sequences are excluded. In the taxonomic part of this study, adult males, pupae and larvae of Micropsectra aristata Pinder, M. atrofasciata, M. bavarica sp. nov., M. klinki sp. nov., M. logani, M. pallidula (Meigen) and M. schrankelae sp. nov. , and adult males and pupae of M. appendica sp. nov. and M. sofiae sp. nov. as well as adult males of M. andalusiaca Marcuzzi, M. calcifontis sp. nov., M. freyi Storå, M. longicrista sp. nov., M. robusta sp. nov. , and M. zernyi Marcuzzi are described and diagnosed. Micropsectra bidentata (Goetghebuer), M. jokaquarta Sasa & Ogata, M. miki Marcuzzi, M. pallida Goetghebuer, M. subnitens Goetghebuer, M. suecica (Kieffer) and M. shouharasima Sasa are new junior synonyms of M. atrofasciata; Micropsectra groenlandica Andersen and M. utonaitertia Sasa are new junior synonyms of M. logani; Micropsectra candida Chaudhuri & Datta, M. franzi Goetghebuer and M. viridiscutellata Goetghebuer are new junior synonyms of M. pallidula. Comments on the ecology, distribution and systematics of each species are provided. Keys to all known life stages are presented, as well as an annotated list of species morphologically similar to species in the atrofasciata group and nomina dubia in the atrofasciata group. Chironomus mimulus Holmgren is transferred to the genus Micropsectra. © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society, 2006, 146 , 165–225.     

Seasonal variation in a low shore Fucus serratus (Fucales,Phaeophyta) population and its epiphytic fauna

Seasonal variation in a Fucus serratus assemblage was studied on the Isle of Man, UK over a 13-month period. Algal cover varied greatly, related to shedding reproductive fronds and winter storms. Peak reproduction was recorded in the autumn. There was little change in density of plants, the population was dominated by a bank of germlings (<20 cm) and an adult mode between 50–70 cm. An indistinct third component of recruiting juveniles was present when gaps in the canopy formed. Seasonal variation in the algae was reflected in the population dynamics of the mobile epiphytes such as Littorina mariae and Lacuna pallidula, which exhibited annual life histories. Sessile species (such as bryozoans) utilized the algae year round, dominating the perennial stipes and lower fronds, which were not shed. Other species utilized the algae in a transient fashion: some feeding on the algae (e.g. Idotea), or other epiphytic animals (e.g. Nucella). Fucus serratus, therefore, provides a variety of spatially and temporally variable niches that explain the diversity of epiphytic animal species that exploit this alga.     

Predation on meiobenthic assemblages: resource use of a tanypod guild (Chironomidae, Diptera) in a gravel stream

1. Three predatory chironomid species constituted numerically 8.8% (± 95% CL 2.2) of the macro- and meiobenthic community at the sediment surface and in the hyporheic zone of Oberer Seebach, a gravel stream in Lower Austria. Larvae of Thienemannimyia geijskesi (Goetghebuer) and Nilotanypus dubius (Meigen) occurred in higher densities in sediment depths between 10 and 40 cm, whereas Conchapelopia pallidula (Meigen) achieved higher densities at the sediment surface. The three species completed one generation in a year. 2. A total of ninety-seven prey species and instars were identified by gut analyses, of which forty-one benthic rotifer species constituted 69.5% of individuals and twenty-three chironomid species and their instars, 22.9%. The three tanypod species showed shifts from mainly rotifer species in early instars to chironomids and diverse other meio- and macrofaunal taxa in later instars. Rather than shifting towards larger prey sizes, growing predators expanded their upper size thresholds and continued to include smaller prey species in their diet. The extent to which tanypod instars fed on similar prey size classes declined with increasing larval size. Predation by tanypods amounted to 2.2% (± 95% CL 0.1) of the combined prey densities and prey consumption averaged 1.32 (bootstrap 95% CL 1.26–1.39) individuals per predator individual. 3. Preferences for microhabitat flow differed between predator species and in the prey assemblage. Prey densities and densities of T. geijskesi and C. pallidula were highest in pool areas, whereas N. dubius achieved high densities in riffle sites. 4. Tanypod larvae fed non-selectively among prey types. To test the significance of observed size(instar)-specific spatial and dietary overlap values amongst tanypod species, simulations were generated from random models for pairs of intra- and interspecific associations of individuals and groups of prey and predator species. Groups and individuals of tanypod instars fed near randomly on groups of prey types and a high proportion (P > 0.60) of prey individuals are quasi-randomly chosen by tanypods in those patches. Tanypod instar-pairs did not show a sustained trophic resource partitioning in time, thus reducing the degree of competitive interactions for food in this predator guild. Spatially segregated and non-segregated tanypod instars formed random aggregations independent of each other at different flow microhabitats. 5. Species-rich prey assemblages such as benthic rotifers and larval chironomids increased the probability of non-selective feeding upon a wide spectrum of prey species by tanypods. Prey choice was governed by prey availability and tanypod individuals fed on many species at rather even proportions independent of each other.