Interspecific and intraspecific diversity in oak powdery mildews in Europe: coevolution history and adaptation to their hosts

Quercus has been reported as the genus with the largest number of attacking powdery mildews. In Europe, oak powdery mildew was rarely reported before 1907, when severe outbreaks were observed. These epidemics were attributed to the newly described species Erysiphe alphitoides, presumed to be of exotic origin. After the burst of interest following the emergence of the disease, research on this topic remained very limited. Interest in research was recently reactivated in response to the availability of molecular tools. This review summarizes current knowledge on the diversity of oak powdery mildews in Europe and their possible evolutionary relationships with European oaks. The most striking results are the evidence of cryptic diversity (detection in France of a lineage closely related to Erysiphe quercicola, previously thought to only have an Asian distribution), large host range (similarity of E. alphitoides and E. quercicola with powdery mildews of tropical plants) but also local adaptation to Quercus robur. These recent findings highlight the complexity of the history of oak powdery mildew in Europe and point to the question of host specialization and host jumps in the evolution of powdery mildew fungi.     

Plant-based host preference and larval competition of the tachinid parasitoid Epicampocera succincta

We investigated the causes of among-plant variation in the parasitism rate of Pieris melete larvae (Lepidoptera: Pieridae) by the parasitoid fly Epicampocera succincta (Diptera: Tachinidae). The rate of parasitism by E. succincta was much higher on the bitter cress Cardamine appendiculata than on any other cruciferous plants. Adult female flies were found to be more attracted to C. appendiculata than to other cruciferous plants for searching for hosts. The parasitoid appeared to be unable to distinguish P. melete from an alternative host, Pieris rapae larvae, that coexisted with P. melete on most crucifer plants. Similarly, E. succincta failed to avoid P. rapae parasitized by the braconid wasp Cotesia glomerata. C. glomerata is a superior competitor to E. succincta if occupying the same host, killing the host before the E. succincta larva can grow and depriving the larva of the chance to survive. E. succincta attacked P. rapae larvae on most cruciferous plants, many of which were already occupied by C. glomerata; only on Cardamine appendiculata was E. succincta free from interspecific competition, because only P. melete was found on this particular plant. However, the strong preference for the hosts on C. appendiculata incurred heavy intraspecific competition among larvae on this plant, killing as great a proportion of larvae as interspecific competition did on the other plants. The balance between the strength of intraspecific competition on the preferred plant and of interspecific competition on the other plants appeared to maintain plant preference by E. succincta. Received: November 13, 2000 / Accepted: April 27, 2001     

Bacterial skin flora variation and in vitro inhibitory activity against Saprolegnia parasitica in brown and rainbow trout

Variations in the number and diversity of bacteria from the skin of brown trout Salmo trutta L. and rainbow trout Oncorhynchus mykiss Walbaum were surveyed from different rivers and fish farms in northern Spain. In addition to determining bacterial populations in skin samples of healthy fish, bacterial populations were determined from skin lesions (of brown trout only) infected with Saprolegnia parasitica, the causal agent of saprolegniosis. Mean bacterial counts from skin lesions of brown trout suffering from saprolegniosis were nearly 1000 times greater than from the skin of uninfected brown and rainbow trout. More than 20 different genera of bacteria were identified, with isolates of Aeromonas and Iodobacter being the predominant genera associated with saprolegniosis lesions. The in vitro inhibitory activity of 72 of these skin isolates was tested against S. parasitica using 3 different assays. These included (1) assessing the inhibition by bacteria of colony growth on agar media, (2) the inhibition of colony growth from colonized hemp seeds in liquid media and (3) the inhibition of cyst germination in liquid media. Finally, the fungicidal effect of the 24 most inhibitory bacterial species, and the inhibitory activity of their culture supernatants, was tested in the same way. Isolates identified as Aeromonas piscicola, A. sobria, Pantoea agglomerans and Pseudomonas fluorescens achieved the highest inhibition against S. parasitica. Many of these inhibitory isolates were obtained primarily from skin lesions of fish with saprolegniosis. It is suggested that some of these isolates might be useful in the biological control of saprolegniosis.     

Relationship between physical leaf characteristics and growth and survival of polyphagous grasshopper nymphs, <Emphasis Type="Italic">Parapodisma subastris</Emphasis> (Orthoptera: Catantopidae)

Common types of plant defense mechanisms are thought to affect the host ranges of polyphagous herbivorous insects, yet few studies have examined the relationship between host plant suitability for polyphagous insects and defense against them. We investigated the suitability of the 19 plant species growing in the habitat of the polyphagous grasshopper, Parapodisma subastris, to determine the relationship between the physical characteristics of leaves and the growth and survival of grasshopper nymphs. We examined leaf toughness, trichome density, and length. Nymph survival was greater on plants with characteristics ranging from soft leaves and dense trichomes to tough leaves and few trichomes than on plants with soft leaves and few trichomes. The exception was Rorippa indica, a plant with soft leaves and few trichomes that uses biotic defense, on which nymph survival was maximal. Higher-quality plants that share common physical characteristics over families may favor polyphagy by grasshoppers that possess ability to overcome the physical defense easily with their robust mandibles.An erratum to this article can be found at     

Evolutionary variations on a theme: host plant specialization in five geographical populations of the leaf beetle Chrysomela lapponica

The ancestral host plants of Chrysomela lapponica are Salicaceae rich in salicylic glycosides (SGs), which serve as precursors for larval chemical defensive secretions. Nevertheless, some populations have shifted to plants poor in SGs or even lacking these compounds. To study whether this shift is accompanied by adaptations to novel SG-poor host plants, we reared C. lapponica larvae from five geographical populations on host plants with high (Salix myrsinifolia) or low (S. caprea) SG content. Individuals from two populations (Finland and Kola region in Russia) associated in nature with SG-rich S. myrsinifolia showed higher survival and shorter developmental time on native host species than on foreign SG-poor S. caprea, thus demonstrating local adaptations to their ancestral SG-rich host plant. Individuals from a Belarus population associated in nature with SG-poor S. caprea showed higher survival on this species than on foreign SG-rich S. myrsinifolia, thus demonstrating local adaptation to the novel SG-poor host. On the other hand, individuals from two other populations associated in nature with SG-poor plants (Baikal and Ural region) performed equally well on both SG-rich S. myrsinifolia and SG-poor S. caprea in our rearing experiments, thus showing no local adaptation to a specific SG-host type, but rather a wide feeding niche including several Salicaceae species of different SG-type. Our results suggest that diet breadth of C. lapponica is a local phenomenon, and that adaptation strategies to novel host plants may differ between populations of a single leaf beetle species.     

Sexual and local divergence in host exploitation in the marine herbivore Idotea baltica (Isopoda)

We studied sexual and habitat-specific variation in herbivores' host exploitation patterns and tested for a hypothesis on sex-specific adaptation in replicated landscapes. The hypothesis has not to our knowledge been previously tested either in a marine environment or for the host exploitation traits of an herbivore. The hypothesis states, first, that populations may show different adaptations due to spatially differing selective environments, and second, that males and females that differ ecologically (e.g. in reproductive behavior, in host use patterns) will respond to selective environments in distinct ways. We investigated possible differences in the host exploitation patterns of the marine generalist crustacean grazer Idotea baltica between the sexes or among populations originating from different habitats: plant assemblages dominated by either a brown alga or an angiosperm species. We determined the preferences for both the structure and nutritive quality of five common host species and compared these to the actual performance on the hosts. We found that performance on the hosts differed between the sexes and differently so in the two habitat types, supporting the hypothesis of sex-specific adaptation between distinct selective environments. Habitat-specific preference for the structural host further supported ecological divergence between habitat types. The different approaches for testing host exploitation resulted in a very different rank order of the hosts, indicating the complexity of the factors involved. The herbivore differentiates for the chemical quality of the hosts, but this alone does not explain host exploitation; rather it supports the theory of enemy-free space as a determinant of host choice. We also discuss the chemical characteristics of the host associated with the exploitation patterns found.     

Metapopulation-level adaptation of insect host plant preference and extinction-colonization dynamics in heterogeneous landscapes

Species living in highly fragmented landscapes typically occur as metapopulations with frequent turnover of local populations. The turnover rate depends on population sizes and connectivities, but it may also depend on the phenotypic and genotypic composition of populations. The Glanville fritillary butterfly (Melitaea cinxia) in Finland uses two host plant species, which show variation in their relative abundances at two spatial scales: locally among individual habitat patches and regionally among networks of patches. Female butterflies in turn exhibit spatial variation in genetically determined host plant preference within and among patch networks. Emigration, immigration and establishment of new populations have all been shown to be strongly influenced by the match between the host plant composition of otherwise suitable habitat patches and the host plant preference of migrating butterflies. The evolutionary consequences of such biased migration and colonization with respect to butterfly phenotypes might differ depending on spatial configuration and plant species composition of the patches in heterogeneous patch networks. Using a spatially realistic individual-based model we show that the model-predicted evolution of host plant preference due to biased migration explains a significant amount of the observed variation in host plant use among metapopulations living in dissimilar networks. This example illustrates how the ecological extinction-colonization dynamics may be linked with the evolutionary dynamics of life history traits in metapopulations.     

The role of ecological availability and host plant characteristics in determining host use by the bogus yucca moth Prodoxus decipiens

1. Specialisation in host plant use is strongly correlated with speciation in many plant‐feeding insects. Specialised taxa, however, could be restricted in host range due to limits in ecological availability of host plant species rather than trade‐offs in using alternate host species. 2. Moths in the genus Prodoxus are extreme specialists on Yucca and speciation is closely tied to host plant shifts. However, many Yucca ranges are allopatric. This study examined whether the bogus yucca moth Prodoxus decipiens is limited in host range because of biogeographic factors or due to differences in the characteristics of host plant species. 3. In a common garden, local P. decipiens moths that use Yucca filamentosa were exposed to individuals of five Yucca species, two that are known hosts of P. decipiens in other parts of its range and three that are used by its sister species, Prodoxus quinquepunctellus. 4. Local moths were attracted to flowers of all Yucca species and females attempted oviposition in the flowering stalks of all species. However, larvae successfully completed development to diapause in only one of the five host plant species. Larval development on non‐natal Yucca species was significantly reduced compared with the local host. 5. The results suggest that differences in host plant characteristics among Yucca species would result in strong natural selection during a host shift. Thus, specialisation in host plant use is probably due to trade‐offs involved with using novel host plant species as well as ecological availability.     

Variability in grape phylloxera preference and performance on canyon grape (Vitis arizonica)

We tested the deme-formation hypothesis experimentally with four populations of leaf-galling grape phylloxera, Daktulosphaira vitifoliae, and its host, canyon grape (Vitis arizonica). An experiment designed to examine preference and performance showed that phylloxera populations did not significantly prefer their original host relative to other hosts in the percent available leaves galled. There were significant herbivore population effects (P<0.01), host effects (P<0.001), and population x host interaction effects (P<0.001). Herbivore populations had different colonizing abilities (performance, as measured in the mean number of galls per leaf) on an individual host (P<0.001), but there was no host effect. Host genotype significantly affected phylloxera performance, measured as survivorship (P<0.01), but a phylloxera population did not necessarily have higher survivorship on its original host. Differences in fecundity, an-other measurement of performance, were due to intrinsic differences among herbivore populations (P<0.05), and not related to host genotype. There was no correlation between distance from a phylloxera population in the field and a host's susceptibility to attack. There was a significant positive relationship between levels of infestation on a clone in the field and its susceptibility to colonization experimentally (P<0.05), suggesting inherent differences in host resistance and susceptibility. These results did not support the deme-formation hypothesis. In a second experiment, host clone x water treatment interactions affected phylloxera survivorship (P<0.05) and fecundity (P<0.05). We conclude that host genotype x environment interactions may prevent sessile, parthenogenetic herbivores from locally adapting to individual host genotypes.     

Host use dynamics in a heterogeneous fitness landscape generates oscillations in host range and diversification

Colonization of novel hosts is thought to play an important role in parasite diversification, yet little consensus has been achieved about the macroevolutionary consequences of changes in host use. Here, we offer a mechanistic basis for the origins of parasite diversity by simulating lineages evolved in silico. We describe an individual‐based model in which (i) parasites undergo sexual reproduction limited by genetic proximity, (ii) hosts are uniformly distributed along a one‐dimensional resource gradient, and (iii) host use is determined by the interaction between the phenotype of the parasite and a heterogeneous fitness landscape. We found two main effects of host use on the evolution of a parasite lineage. First, the colonization of a novel host allowed parasites to explore new areas of the resource space, increasing phenotypic and genotypic variation. Second, hosts produced heterogeneity in the parasite fitness landscape, which led to reproductive isolation and therefore, speciation. As a validation of the model, we analyzed empirical data from Nymphalidae butterflies and their host plants. We then assessed the number of hosts used by parasite lineages and the diversity of resources they encompass. In both simulated and empirical systems, host diversity emerged as the main predictor of parasite species richness.     

Host-associated fitness variation in a seed beetle (Coleoptera: Bruchidae): evidence for local adaptation to a poor quality host

The geographic distributions of many generalist herbivores differ from those of their host plants, such that they experience coarse-grained spatial variation in natural selection on characters influencing adaptation to host plants. Thus, populations differing in host use are expected to differ in their ability to survive and grow on these host plants. We examine host-associated variation in larval performance (survivorship, development time, and adult body weight) and oviposition preference, within and between two populations ofStator limbatus (Coleoptera: Bruchidae) that differ in the hosts available to them in nature. In one population,Acacia greggii (Fabaceae: Mimosoideae) andCercidium microphyllum (Fabaceae: Caesalpininoideae) are each abundant, while in the second population onlyC. floridum andC. microphyllum are present. In both populations, egg-to-adult survivorship was less than 50% onC. floridum, while survivorship was greater than 90% onA. greggii. Most of the mortality onC. floridum occurred as larvae were burrowing through the seed coat; very low mortality occurred during penetration of the seed coat ofA. greggii. Significant variation was present between populations, and among families (within populations), in survivorship and egg-to-adult development time onC. floridum; beetles restricted toCercidium in nature, without access toC. floridum, survived better and developed faster onC. floridum than beetles that had access toA. greggii. Large host effects on body size were detected for female offspring: females reared onA. greggii were larger than those reared onC. floridum, whereas male offspring wee approximately the same size regardless of rearing host. Trade-offs between performance onC. floridum andC. floridum were not detected in this experiment. Instead, our data indicate that development time and survivorship onC. floridum may be largely independent of development time and survivorship onA. greggii. Patterns of oviposition preference corresponded to the observed patterns of host suitability: in laboratory preference tests, beetles with access toA. greggii in nature tended to prefer this host more than beetles without access to this host in nature.     

Identification of olfactory receptor neurons in Uraba lugens (Lepidoptera: Nolidae) and its implications for host range

Phytophagous insects detect volatile compounds produced by host and non-host plants, using species-specific sets of olfactory receptor neurons (ORNs). To investigate the relationship between the range of host plants and the profile of ORNs, single sensillum recordings were carried out to identify ORNs and corresponding active compounds in female Uraba lugens (Lepidoptera: Nolidae), an oligophagous eucalypt feeder. Based on the response profiles to 39 plant volatile compounds, 13 classes of sensilla containing 40 classes of ORNs were identified in female U. lugens. More than 95% (163 out of 171) of these sensilla contained 16 classes of ORNs with narrow response spectra, and 62.6% (107 out of 171) 18 classes of ORNs with broad response spectra. Among the specialized ORNs, seven classes of ORNs exhibited high specificity to 1,8-cineole, (±)-citronellal, myrcene, (±)-linalool and (E)-β-caryophyllene, major volatiles produced by eucalypts, while nine other classes of ORNs showed highly specialized responses to green leaf volatiles, germacrene D, (E)-β-farnesene and geranyl acetate that are not produced by most eucalypts. We hypothesize that female U. lugens can recognize their host plants by detecting key host volatile compounds, using a set of ORNs tuned to host volatiles, and discriminate them from non-host plants using another set of ORNs specialized for non-host volatiles. The ORNs with broad response spectra may enhance the discrimination between host and non-host plants by adding moderately selective sensitivity. Based on our finding, it is suggested that phytophagous insects use the combinational input from both host-specific and non-host specific ORNs for locating their host plants, and the electrophysiological characterization of ORN profiles would be useful in predicting the range of host plants in phytophagous insects.     

Antimicrobial and immunomodulatory activity of host defense peptides,clavanins and LL-37, in vitro: An endodontic perspective

Endodontic treatment is mainly based on root canal disinfection and its failure may be motivated by microbial resistance. Endodontic therapy can be benefitted by host defense peptides (HDPs), which are multifunctional molecules that act against persistent infection and inflammation. This study aimed to evaluate the antimicrobial, cytotoxic and immunomodulatory activity of several HDPs, namely clavanin A, clavanin A modified (MO) and LL-37, compared to intracanal medication Ca(OH)₂. HDPs and Ca(OH)₂ were evaluated by: (1) antimicrobial assays against Candida albicans and Enterococcus faecalis, (2) cytotoxicity assays and (3) cytokine tumor necrosis factor (TNF)-α, monocyte chemoattractant protein (MCP)-1, interleukin (IL)-1α, IL-6, IL-10 and IL-12 and nitric oxide (NO) production by RAW 264.7 cells incubated with or without heat-killed (HK) C. albicans or E. faecalis combined or not with interferon-γ. The minimum inhibitory concentration (MIC) was established only for E. faecalis (LL-37, 57 μM). Considering cytotoxicity, clavanin MO was able to reduce cell viability in many groups and demonstrated lowest LC₅₀. The Ca(OH)₂ up-regulated the production of MCP-1, TNF-α, IL-12 and IL-6 and down-regulated IL-1α, IL-10 and NO. Clavanins up-regulated the TNF-α and NO and down-regulated IL-10 production. LL-37 demonstrated up-regulation of IL-6 and TNF-α production and down-regulation in IL-10 and NO production. In conclusion, LL-37 demonstrated better antibacterial potential. In addition, Ca(OH)₂ demonstrated a proinflammatory response, while the HDPs modulated the inflammatory response from non-interference with the active cytokines in the osteoclastogenesis process, probably promoting the health of periradicular tissues.     

Correlated patterns of variation in phenology and seed production in populations of two annual grasses along an aridity gradient

I applied a comparative approach to reveal correlated patterns of variation in phenology and seed production in four populations of two annual grasses Hordeum spontaneum and Avena sterilis, sampled in the same environments distributed along an aridity gradient in Israel. The steep aridity gradient in Israel represents two parallel clines of environmental productivity (annual rainfall) and predictability (variation in amount and timing of annual rainfall) that is likely to induce similar responses in natural plant populations distributed along the gradient, if (1) selection is strong, (2) species share the same ecological niche, and (3) there is genetic variation for ecologically important traits. I found in plants of both species (1) ultimate advance in onset of flowering, and (2) more but smaller seeds, with increasing aridity. The broad sense heritabilities of onset of flowering, seed size and seed yield in both species were very high, moderate and low, respectively. It appears that the observed adaptive complex of traits have evolved in both species in response to this specific array of environments.     

Intraspecific variation in beech scale populations and in susceptibility of their host Fagus sylvatica

ABSTRACT.

• 1 Within a seed orchard in southern England, beech trees (Fagus sylvatica L.) belonging to three clones were artificially infested by introducing beech scale larvae (Cryptococcus fagisuga Lind. Homoptera: Coccidae) into small cages attached to the bark.
• 2 Some larvae developed to fecund adults on trees of two susceptible clones but all failed to develop on a third, resistant clone.
• 3 Within susceptible clones, survival of larvae on individual trees was positively related to their degree of natural infestation.
• 4 Larvae deriving from several separate trees differed significantly in their ability to survive when inoculated onto trees of susceptible clones.
• 5 Five forest trees which acted as both donors of larvae and as hosts for artificial inoculation were each inoculated with larvae from all five trees.
• 6 There was significant variation in survival of inoculated larvae both between the host trees and between sources of larvae on each host.
• 7 Survival of larvae reinoculated onto their original host was significantly higher than that of larvae originating from other trees.
• 8 Fecundity of adults on the forest trees was positively correlated with the probability of inoculated larvae surviving to the adult stage.

     

Characterization and evaluation of Ramularia crupinae,a candidate for biological control,and of its host,two varieties of Crupina vulgaris in the United States

Crupina vulgaris (common crupina) is an invasive annual plant of rangelands and pastures in the United States (USA). There are two varieties of C. vulgaris in the USA that differ morphologically and biologically, particularly in requirements for bolting. A vernalization protocol enabled synchronization of bolting, thus facilitating concurrent comparative studies of both varieties. Leaf-removal experiments suggest that all leaves provide photosynthate for seed fill, but the cauline leaves, on a relative basis, produced 1.7–4 times more seed per g than rosette leaves, suggesting disease on the cauline leaves has greater potential to reduce seed production than disease on rosette leaves. Ramularia crupinae, a leaf-spotting fungus, was evaluated for biological control. A single inoculation caused a 47% reduction in root dry weight, and seed yield was reduced by 39% as the number of inoculations increased from 0 (controls) to 3. None of 35 non-target taxa, i.e., species, cultivars, and varieties, in the tribe Cardueae was damaged from inoculation by R. crupinae, including safflower, which developed a few, small necrotic spots on old leaves. Best Linear Unbiased Predictors (BLUPs), generated by a mixed model analysis of disease reaction and genetic relatedness data, indicated that only C. vulgaris varieties were susceptible to disease; i.e., BLUPs were significantly different from zero (p > |t| < 0.05). None of the other taxa had BLUP estimators that were significantly different from zero and were, therefore, determined to be not susceptible to disease by R. crupinae. Results suggest that R. crupinae is a potentially good candidate for biological control of this important weed pest and would likely not affect other species of importance in the USA.     

Geographic variation in oviposition preference for male and female host plants in a geometrid moth: implications for evolution of host choice

Several dioecious plant species exhibit sexual dimorphisms in defensive traits. However, the effects of sexual dimorphism on defense against herbivores remain poorly understood. Eurya japonica (Thunb.) (Theaceae) is a dioecious shrub that shows sexual dimorphism in the chemical defense of flower buds. Female calyces contain higher concentrations of total phenolics and condensed tannins than do male calyces. Male flower buds are edible for a florivore moth, Chloroclystis excisa (Butler) (Lepidoptera: Geometridae), whereas the female flower buds are lethal to the moth larvae. The moths prefer to oviposit on male over female E. japonica flower buds. As the moths also occur in areas lacking E. japonica, we tested whether the oviposition preference for E. japonica flower sex differed between moths sympatric and allopatric with E. japonica. The moths sympatric with E. japonica showed a stronger preference for male E. japonica than the moths allopatric with E. japonica. Our phylogeographic study using mitochondrial cytochrome oxidase subunit I gene sequences revealed little genetic differentiation between moth populations sympatric and allopatric with E. japonica. These results suggest that the adaptive oviposition preference for flower sex of E. japonica has evolved rapidly in C. excisa.     

The influence of host plant variation and intraspecific competition on oviposition preference and offspring performance in the host races of Eurosta solidaginis

1. A series of experiments was conducted to measure the impact of plant genotype, plant growth rate, and intraspecific competition on the oviposition preference and offspring performance of the host races of Eurosta solidaginis (Diptera: Tephritidae), a fly that forms galls on Solidago altissima and Solidago gigantea (Asteraceae). Previous research has shown that both host races prefer to oviposit on their own host plant where survival is much higher than on the alternate host plant. In this study, neither host race showed any relationship between oviposition preference and offspring performance in choosing among plants of their natal host species. 2. The larval survival of both host races differed among plant genotypes when each host race oviposited on its natal host species. In one experiment, altissima host race females showed a preference among plant genotypes that was not correlated with offspring performance on those genotypes. In all other experiments, neither the altissima nor gigantea host race demonstrated a preference for specific host plant genotypes. 3. Eurosta solidaginis had a preference for ovipositing on rapidly growing ramets in all experiments, however larval survival was not correlated with ramet growth rate at the time of oviposition. 4. Eurosta solidaginis suffered high mortality from intraspecific competition in the early larval stage. There was little evidence, however, that females avoided ovipositing on ramets that had been attacked previously. This led to an aggregated distribution of eggs among ramets and strong intraspecific competition. 5. There was no interaction among plant genotype, plant growth rate, or intraspecific competition in determining oviposition preference or offspring performance.     

Demersal fish parasite fauna around the South Shetland Islands: high species richness and low host specificity in deep Antarctic waters

A total of nine Antarctic fish species belonging to five families were examined for their endohelminth parasite fauna. The fishes Parachaenichthys charcoti (Bathydraconidae), Chaenocephalus aceratus (Channichtyidae), Paradiplospinus gracilis (Gempylidae), Muraenolepis microps (Muraenolepididae), Gobionotothen gibberifrons, Lepidonotothen larseni, L. nudifrons, L. squamifrons, and Trematomus eulepidopus (Nototheniidae) were caught between 80 and 608 m trawling depth off the Antarctic Peninsula (Elephant Island, King George Island) in 1996. Nineteen different parasites species comprising five Digenea, two Cestoda, four Nematoda, and eight Acanthocephala were found. Pseudophyllidean cestodes, the nematodes Contracaecum radiatum and C. osculatum as well as the acanthocephalan Corynosoma bullosum were the most common, infesting eight of the fish species studied with prevalences reaching 100%. Pseudoterranova decipiens s.l. was the only parasite that was isolated from all studied fish species; however, at a lower intensity. The observed parasite host specificity was low, and the species richness in a single fish ranged from one to eleven in a C. aceratus. This icefish and the moray cod M. microps were the most heavily infested fish, harbouring many adult and larval parasitic stages. The benthodemersal P. gracilis had only two larval parasite species, while the nototheniids had very similar parasite communities, harbouring a total of 8–14 species. Larval mammalian parasites were found to utilize fish, especially the nototheniids and channichthyids, as a common transmission route into their final hosts. The fish parasites parallel explored different benthic host systems to reach the most suitable host. In contrast to the coast and continental shelf, the meso/bathypelagiac zone appears to be species poor and is inhabited by few larval forms. The fish parasite fauna off the South Shetland Islands can be characterized by generalistic parasites that distribute within Antarctic waters according to the feeding ecology and depth range of their teleost hosts, not only horizontally but also extending vertically into the deep sea.