The Scent of Danger: the Impact of Predator Chemical Cues on Emergence from Refuge and Willingness to Autotomize Limbs in the House Cricket (<Emphasis Type="Italic">Acheta domesticus</Emphasis>)

Prey can accurately assess predation risk via the detection of chemical cues and take appropriate measures to survive encounters with predators. Research on the chemical ecology of terrestrial invertebrate predator-prey interactions has repeatedly found that direct chemical cues can alter prey organisms’ antipredator behavior. However, much of this research has focused on the chemical mediation of avoidance and immobility by cues from lycosid spiders neglecting other prominent invertebrate predators and behavior such as autotomy. In our study, house crickets (Acheta domesticus) were exposed to cues from cricket-fed orange-footed centipedes (Cormocephalus aurantiipes), red-back spiders (Latrodectus hasselti), an odorous (cologne) control, and a non-odorous control to determine whether direct chemical cues had any influence on two types of anti-predatory behavior: the willingness (latency) to emerge from a refuge and to autotomize limbs. Exposure to C. aurantiipes cues resulted in a significantly slower emergence from a refuge, but exposure to L. hasselti cues did not. Direct chemical cues had no influence on initial autotomy, but exposure to L. hasselti cues did significantly decrease the latency to autotomize a second limb. That cues from L. hasselti had an influence on a second autotomy, but not initial autotomy may be because crickets that undergo autotomy for a second time may perceive themselves to be already at a higher risk of predation as they were already missing a limb. Variation in responses to cues from different predators demonstrates a need to examine the influence of chemical cues from a wider variety of invertebrate predators on anti-predator behavior.     

Evolution of increased larval competitive ability in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis> without increased larval feeding rate

Multiple experimental evolution studies on Drosophila melanogaster in the 1980s and 1990s indicated that enhanced competitive ability evolved primarily through increased larval tolerance to nitrogenous wastes and increased larval feeding and foraging rate, at the cost of efficiency of food conversion to biomass, and this became the widely accepted view of how adaptation to larval crowding evolves in fruitflies. We recently showed that populations of D. ananassae and D. n. nasuta subjected to extreme larval crowding evolved greater competitive ability without evolving higher feeding rates, primarily through a combination of reduced larval duration, faster attainment of minimum critical size for pupation, greater efficiency of food conversion to biomass, increased pupation height and, perhaps, greater urea/ammonia tolerance. This was a very different suite of traits than that seen to evolve under similar selection in D. melanogaster and was closer to the expectations from the theory of K-selection. At that time, we suggested two possible reasons for the differences in the phenotypic correlates of greater competitive ability seen in the studies with D. melanogaster and the other two species. First, that D. ananassae and D. n. nasuta had a very different genetic architecture of traits affecting competitive ability compared to the long-term laboratory populations of D. melanogaster used in the earlier studies, either because the populations of the former two species were relatively recently wild-caught, or by virtue of being different species. Second, that the different evolutionary trajectories in D. ananassae and D. n. nasuta versus D. melanogaster were a reflection of differences in the manner in which larval crowding was imposed in the two sets of selection experiments. The D. melanogaster studies used a higher absolute density of eggs per unit volume of food, and a substantially larger total volume of food, than the studies on D. ananassae and D. n. nasuta. Here, we show that long-term laboratory populations of D. melanogaster, descended from some of the populations used in the earlier studies, evolve essentially the same set of traits as the D. ananassae and D. n. nasuta crowding-adapted populations when subjected to a similar larval density at low absolute volumes of food. As in the case of D. ananassae and D. n. nasuta, and in stark contrast to earlier studies with D. melanogaster, these crowding-adapted populations of D. melanogaster did not evolve greater larval feeding rates as a correlate of increased competitive ability. The present results clearly suggest that the suite of phenotypes through which the evolution of greater competitive ability is achieved in fruitflies depends critically not just on larval density per unit volume of food, but also on the total amount of food available in the culture vials. We discuss these results in the context of an hypothesis about how larval density and the height of the food column in culture vials might interact to alter the fitness costs and benefits of increased larval feeding rates, thus resulting in different routes to the evolution of greater competitive ability, depending on the details of exactly how the larval crowding was implemented.     

Relative predation risk and risk of desiccation co-determine oviposition preferences in Cope’s gray treefrog, <Emphasis Type="Italic">Hyla chrysoscelis</Emphasis>

Habitat permanence and threat of predation are primary drivers of community assembly and composition in lentic freshwater systems. Pond-breeding amphibians select oviposition sites to maximize fitness and minimize risks of predation and desiccation of their offspring, typically facing a trade-off between the two as predation risk often increases as desiccation risk decreases. To experimentally determine if Hyla chrysoscelis partition oviposition along gradients of relative desiccation risk and predation risk, we tested oviposition site preference in a natural population of treefrogs colonizing experimental ponds that varied in water depth and contained predatory larvae of two Ambystoma salamander species. Hyla chrysoscelis selected habitats with both lower predation risk, avoiding A. talpoideum over A. maculatum, and lower desiccation risk, selecting ponds with three times greater depth. We demonstrate that adult oviposition site choices simultaneously minimize relative predation risk and desiccation risk and that closely related salamander species produce functionally different responses among colonizing animals.     

A review of oribatid mites of the family Liacaridae (Acariformes,Oribatida) from the Caucasus

The paper summarizes the data on oribatid mites of the family Liacaridae and their distribution in the Caucasus. Two new species, Liacarus subiasi from Azerbaijan (differing from the known species in the shape of cuspids and short lamellae) and Dorycranosus musaevi from Daghestan (differing from closely related D. splendens (Coggi, 1898) and D. punctulatus Miheli?i?, 1956 in the presence of the smooth notogaster, wide distal lamellar cuspids, and also in the absence of inner cuspid tooth and the presence of longer ventral setae), are described. The species status of D. punctulatus is reestablished. Liacarus lencoranicus Krivolutsky, 1967 and L. nitidulus Krivolutsky, 1967 are synonymized with L. coracinus C.L. Koch, 1898. D. zachvatkini Kuliev, 1962 (= D. ibericus Dzaparidze, 1973) is redescribed. Data on species variability of Adoristes poppei (Oudemans, 1906) and A. ovatus Koch, 1849 are given.     

Interacting Effects of Leg Autotomy and Exposure to Predator Cues on Survival in A Wolf Spider (<Emphasis Type="Italic">Pardosa valens</Emphasis>)

Chemical cues from predators (kairomones) are used by many aquatic and terrestrial animals when deciding on behavioral responses to predation threats. These responses may also be affected by the animal’s physiological state (e.g., nutrition level, parasitism, or prior injury), which could alter normal responses to kairomones. In this study, we examined effects of leg autotomy (the voluntary sacrifice of a leg) on subsequent responses to predator chemical cues in females of the riparian-zone wolf spider Pardosa valens. In a fully-crossed design, spiders with all legs intact or with one leg removed were exposed to one of two cue treatments for 90 min: a control (no predator cue) or one with chemical cues (silk and excreta) from a larger sympatric wolf spider, Rabidosa santrita. We then introduced an R. santrita into each container, and recorded subsequent survival of P. valens. Survivorship was significantly higher for individuals previously exposed to predator cues than for those in the control group; however, autotomy had no effect on survivorship, which was similar for both intact and autotomized spiders in both the predator-cue and control treatments. In addition, although P. valens were more likely to be found off the substrate than on it when the predator was added in each of the four treatment pairings, this initial position did not influence survivorship. These results therefore indicate that P. valens can behaviorally respond to predator kairomones in ways that reduce their risk of predation, but that this response is unaffected by the prior sacrifice of a leg.     

Determining the effects of life stage,shared prey density and host plant on intraguild predation of a native lacewing (<Emphasis Type="Italic">Chrysoperla carnea</Emphasis>) by an invasive coccinellid (<Emphasis Type="Italic">Harmonia axyridis</Emphasis>)

Negative impacts of non-native Harmonia axyridis (Pallas) on members of the native aphid enemy guild have been widely hypothesised but mainly only assessed with other coccinellid species, and mostly in small experimental arenas. Here we investigated the interactions between H. axyridis and Chrysoperla carnea Stephens larvae. In small-scale (Petri dish) arenas 2nd-instar C. carnea were at risk of predation from larval (2nd and 4th-instar) and adult (male and female) H. axyridis while 3rd-instar C. carnea were only at minimal risk from 4th-instar and adult female H. axyridis. Plant species, aphid species and aphid density did not affect intraguild predation of 2nd-instar C. carnea by 4th-instar and adult H. axyridis in mesocosm experiments. Chrysoperla carnea consumed similar numbers of Megoura viciae Buckton, Aphis fabae Scop. and Acyrthosiphon pisum Harris aphids while H. axyridis consumed fewer M. viciae than the other two species. The greatest suppression of A. pisum was achieved in treatments with both C. carnea and H. axyridis. Life stage and the sex of H. axyridis as well as the life stage of C. carnea are important variables affecting intraguild predation and these attributes should be considered when assessing the potential threat of other potentially invasive alien predators.     

Shared behavioral responses and predation risk of anuran larvae and adults exposed to a novel predator

Invasive species are a regional and global threat to biological diversity. In order to evaluate an invasive predator species’ potential to harm populations of native prey species, it is critical to evaluate the behavioral responses of all life stages of the native prey species to the novel predator. The invasion of the African clawed frog (Xenopus laevis) into southern California provides an opportunity to evaluate the predation risk and behavioral responses of native amphibians. We performed predation trials and explored prey behavioral responses to determine how this invasive predator may impact native amphibian populations using Pacific chorus frogs (Pseudacris regilla) as a representative native California prey species. We found that X. laevis will readily prey upon larval and adult life stages of P. regilla. Behavior trials indicated that both larval and adult P. regilla exhibit prey response behaviors and will spatially avoid the novel invasive predator. The results suggest that native anurans may have a redundant predator response in both the larval and adult life stages, which could reduce the predatory impact of X. laevis but also drive emigration of native amphibians from invaded habitat.     

Adaptation to larval crowding in <Emphasis Type="Italic">Drosophila ananassae</Emphasis> and <Emphasis Type="Italic">Drosophila nasuta nasuta</Emphasis>: increased larval competitive ability without increased larval feeding rate

The standard view of adaptation to larval crowding in fruitflies, built on results from 25 years of multiple experimental evolution studies on Drosophila melanogaster, was that enhanced competitive ability evolves primarily through increased larval feeding and foraging rate, and increased larval tolerance to nitrogenous wastes, at the cost of efficiency of food conversion to biomass. These results were at odds from the predictions of classical K-selection theory, notably the expectation that selection at high density should result in the increase of efficiency of conversion of food to biomass, and were better interpreted through the lens of α-selection. We show here that populations of D. ananassae and D. n. nasuta subjected to extreme larval crowding evolve greater competitive ability and pre-adult survivorship at high density, primarily through a combination of reduced larval duration, faster attainment of minimum critical size for pupation, greater time efficiency of food conversion to biomass and increased pupation height, with a relatively small role of increased urea/ammonia tolerance, if at all. This is a very different suite of traits than that seen to evolve under similar selection in D. melanogaster, and seems to be closer to the expectations from the canonical theory of K-selection. We also discuss possible reasons for these differences in results across the three species. Overall, the results reinforce the view that our understanding of the evolution of competitive ability in fruitflies needs to be more nuanced than before, with an appreciation that there may be multiple evolutionary routes through which higher competitive ability can be attained.     

On the morphology of the early life history stages of lanternfish genus <Emphasis Type="Italic">Triphoturus</Emphasis> (Myctophidae) and distribution of <Emphasis Type="Italic">T. oculeum</Emphasis> larvae in southeastern waters of the Pacific Ocean

Results of comparative analysis of specific features of morphology of larval lanternfishes of the Indo-Pacific genus Triphoturus based on materials from the southeastern part of the Pacific Ocean, northwestern Pacific, South China Sea, and the western part of the Indian Ocean, as well as on published data, are provided. Noticeable differences are shown in specific features of pigmentation of larval T. nigrescens (sensu Hulley, 1986) from different parts of the vast range of this species, that may be accounted for by its individual and/or geographic variation and by the collective pattern of this taxon. It is stated that it is necessary to use genetic data for the verification of the taxonomic status of the representatives of the genus. Morphological evidence in favor of the species isolation of T. oculeum and T. microchir based on larval materials is presented. The presence of three morphologically different forms of larval Triphoturus from the eastern Pacific differing in the pattern of body pigmentation that are identified with three nominal species of the genus Triphoturus—T. nigrescens, T. mexicanus, and T. oculeum—is confirmed. The study of specific features of distribution of larvae of these species in southeastern waters of the Pacific Ocean based on our own and published materials revealed the presence of larval T. mexicanus and T. oculeum off Peru, which is supported by data on the presence of adult individuals of both species here.     

Artificial reefs for sea cucumber aquaculture confirmed as settlement substrates of the moon jellyfish <Emphasis Type="Italic">Aurelia coerulea</Emphasis>

In coastal areas with a high intensity of human activities, expansion of artificial structures may enhance Aurelia spp. blooms because these constructions may provide additional substrates for the settlement and proliferation of the polyps. In the present study, the possible occurrence and distribution of Aurelia coerulea ephyrae and polyps were investigated in sea cucumber (Apostichopus japonicus) culture ponds that contain huge amounts of artificial structures. Our results showed that A. coerulea ephyrae were widely distributed in the A. japonicus culture ponds along the Bohai and Yellow Seas. Furthermore, underwater photography revealed that polyps of A. coerulea mainly occurred on the undersides of the artificial reefs made by plastic sunshade nets, tiles and substrate cages. The artificial reefs may decrease the time A. coerulea planulae spend settling, provide more hidden, calm and shady places for the settlement and proliferation of A. coerulea planulae, and thus were suitable substrates for the moon jellyfish A. coerulea. Our study suggests that the A. japonicus culture ponds may act as nursery grounds for the jellyfish A. coerulea and may potentially enhance the blooms of this species in the coastal waters along the Bohai and Yellow Seas.     

Size matters: predation of fish eggs and larvae by native and invasive amphipods

Invasive predators can have dramatic impacts on invaded communities. Extreme declines in macroinvertebrate populations often follow killer shrimp (Dikerogammarus villosus) invasions. There are concerns over similar impacts on fish through predation of eggs and larvae, but these remain poorly quantified. We compare the predatory impact of invasive and native amphipods (D. villosus and Gammarus pulex) on fish eggs and larvae (ghost carp Cyprinus carpio and brown trout Salmo trutta) in the laboratory. We use size-matched amphipods, as well as larger D. villosus reflecting natural sizes. We quantify functional responses, and electivity amongst eggs or larvae and alternative food items (invertebrate, plant and decaying leaf). D. villosus, especially large individuals, were more likely than G. pulex to kill trout larvae. However, the magnitude of predation was low (seldom more than one larva killed over 48 h). Trout eggs were very rarely killed. In contrast, carp eggs and larvae were readily killed and consumed by all amphipod groups. Large D. villosus had maximum feeding rates 1.6–2.0 times higher than the smaller amphipods, whose functional responses did not differ. In electivity experiments with carp eggs, large D. villosus consumed the most eggs and the most food in total. However, in experiments with larvae, consumption did not differ between amphipod groups. Overall, our data suggest D. villosus will have a greater predatory impact on fish populations than G. pulex, primarily due to its larger size. Higher invader abundance could amplify this difference. The additional predatory pressure could reduce recruitment into fish populations.     

Host plants influence female oviposition and larval performance in West Indian sweet potato weevils <Emphasis Type="Italic">Euscepes postfasciatus</Emphasis> (Coleoptera: Curculionidae)

Euscepes postfasciatus (Fairmaire) is an invasive pest of the sweet potato (Ipomoea batatas) and is also parasitic to other wild host plants of the Ipomoea genus. The population density of E. postfasciatus is sometimes greater in Ipomoea pes-caprae L. than in Ipomoea indica (Burm. f.). We investigated the desirability of I. pes-caprae as a host plant for E. postfasciatus in terms of reproductive and developmental potential. Females laid fewer eggs on I. pes-caprae, and the eclosion of their larvae was delayed compared with on I. indica. Furthermore, the larval growth rate was slower on I. pes-caprae than on I. indica. These results suggest that I. pes-caprae is not always the preferred host for egg laying and growth rate in the early developmental stages. However, the larval survival rate after the initial period of development was markedly better on I. pes-caprae than on I. indica. The present simulation study demonstrated that the population density of E. postfasciatus on I. pes-caprae overwhelmed that on I. indica over generations. Comparing the two wild host plant species, I. pes-caprae outweighs I. indica with respect to total population growth, but reproduction on I. indica may be advantageous for the colonization of the new habitat.     

Fatal attack on a Rylands' bald-faced saki monkey (<Emphasis Type="Italic">Pithecia rylandsi</Emphasis>) by a black-and-white hawk-eagle (<Emphasis Type="Italic">Spizaetus melanoleucus</Emphasis>)

Predation risk has played an important role in primate behavioral evolution, yet natural primate–predator interactions are rarely observed. We describe the consumption and probable predation of an adult bald-faced saki monkey (Pithecia rylandsi) by a black-and-white hawk-eagle (Spizaetus melanoleucus) at the Los Amigos Biological Station in lowland Amazonian Peru. To our knowledge, this is the first published case of a black-and-white hawk-eagle consuming any primate species. We contend that while most reported observations of successful and attempted predation by raptors involves the largest and most notorious species (i.e. the harpy eagle), smaller and lesser known species like S. melanoleucus should be considered more seriously as a predator of neotropical primates. We discuss the predation event in the context of understanding what other neotropical primates might be vulnerable to S. melanoleucus predation given its body size and hunting tactic.     

Methanogenic community compositions in surface sediment of freshwater aquaculture ponds and the influencing factors

Aquaculture ponds represent ecologically relevant environments to study the community composition and diversity of methanogenic assemblages, as well as their interactions with cultivated species and chemical indicators. In this study, aquaculture ponds with crab (Eriocheir sinensis), oriental river prawn (Macrobrachium nipponense), perch (Micropterus salmonides) and Wuchang fish (Parabramis pekinensis) were sampled, and Illumina high-throughput sequencing was used to investigate the methanogenic communities. The results revealed that the abundant methanogenic orders in surface sediment were Methanomicrobiales, Methanosarcinales and Methanocellales. The relative abundance of Methanocellales was higher in crab and prawn ponds as compared to other ponds. Methanogenic 16S rRNA gene abundance and beta diversity of the community was affected by the cultivated species. Methanogenic communities in aquaculture ponds with higher contents of total nitrogen and organic matter had decreased species richness, while those with higher contents of ammonia and nitrite had an overall decreased abundance of methanogens and their respective diversities. Overall, in addition to the differences in cultivated species, the consequent differences in farming practices including the types and amounts of feeds used, the contents of total nitrogen, organic matter, ammonia and nitrite could all influence the methanogenic community in surface sediment of aquaculture ponds.     

On distribution and ecology of some species of cleonines (Coleoptera,Curculionidae): IV. Genus <Emphasis Type="Italic">Lixus</Emphasis> F., subgenus <Emphasis Type="Italic">Eulixus</Emphasis> Reitt.

Data on habitats, food plants of larvae and adults, feeding, mating, oviposition, larval and pupal development, natural enemies, and distribution of seven weevil species (Lixus canescens F.-W., L. iridis Ol., L. myagri Ol., L. punctirostris Boh., L. subtilis Boh., L. incanescens Boh., and L. brevipes Bris.) are given. New host plants of L. canescens and L. iridis are revealed. Gall induction by L. brevipes is reported for the first time. Distribution of all the species in Ukraine and Russia (the latter based on the literature) are given in more detail. Information on the known and potential economic importance of every species is provided.     

Chemical defences of native European coccinellid eggs against intraguild predation by the invasive Asian coccinellid, <Emphasis Type="Italic">Harmonia axyridis</Emphasis> (Pallas)

Harmonia axyridis (Pallas) is a coccinellid of Asian origin that has recently invaded substantial parts of Europe and is suspected to affect native coccinellid populations through intraguild predation and competition for food. Previous work has shown that two species from the Calvia genus appeared to be well protected against H. axyridis predation. To deepen our understanding on chemical protection of Calvia spp. and the predation risk by H. axyridis, we tested for susceptibility and palatability of Calvia spp. and H. axyridis eggs against predation by H. axyridis neonate larvae. Results show that eggs of C. quatuordecimguttata were mostly not eaten by H. axyridis, while eggs of the congeneric C. decemguttata were found to be largely unprotected against predation by the invasive coccinellid. We also observed that H. axyridis first instars successfully cannibalized on conspecific eggs. Removing the surface chemicals from C. quatuordecimguttata eggs resulted in significantly reduced protection from being preyed upon by H. axyridis, while applying these extracts onto C. decemguttata and H. axyridis eggs resulted in increased protection against H. axyridis larvae. The importance of surface chemicals in the interactions between H. axyridis and native coccinellids was confirmed by GC–MS analysis, showing a high diversity of hydrocarbons located on the surface of C. quatuordecimguttata eggs, i.e. more than twice as many when compared to C. decemguttata. Survival of H. axyridis larvae feeding on eggs of C. quatuordecimguttata, C. decemguttata or conspecific eggs, from which surface chemicals were removed by washing them with hexane, was not different from survival on unwashed eggs.     

Suppression of Settlement of Larvae of Fouling Organism by Water-Soluble Substances from Epibiotic Bacteria

Twenty-nine bacterial strains were isolated from the surface of the green alga Ulva reticulata, the soft coral Dendronephthya sp., and the sponge Haliclona sp. The bacterial species Vibrio alginolyticus, Vibrio sp. 4, an unidentified α-Proteobacterium, Vibrio sp. 7, Pseudoalteromonas sp. 2, and Pseudoalteromonas sp. 4 were found to suppress the larval settlement of the polychaete Hydroides elegans (Haswell, 1883) and the bryozoan Bugula neritina (Linnaeus, 1758). Aqueous extracts of five bacteria (all those named above except Pseudoalteromonas sp. 2) prevented larval settlement. Bacteria V. alginolyticus, Vibrio sp. 4, and an unidentified α-Proteobacterium were first discovered to produce high-molecular substances (>100 kDa) preventing larval settlement. Their activity was inhibited by amylase treatment, while trypsin and papain did not influence their activity. The data obtained proved that bacteria from the surface of the number of marine organisms excrete water-soluble sacchariferous compounds preventing larval settlement.     

Surface–sediment diatom assemblages of the urban ponds of St. Petersburg,Russia

The diatom assemblages of the surface sediments have been studied in 53 urban ponds and lakes of St. Petersburg for the first time. In total, 350 species and infraspecific taxa have been registered; the species of Achnanthidium, Cocconeis, Cyclostephanos, Cyclotella, Gomphonema, Lemnicola, Navicula, Nitzschia, and Stephanodiscus genera were the most common. The wide distribution of small centric planktonic taxa, Cyclostephanos dubius, C. invisitatus, Cyclotella pseudostelligera, Stephanodiscus hantzschii, and S. minutulus, is preconditioned by the depletion of dissolved silica, which is a result of the high phosphorus load. The high abundance of macrophytes in the shallowest sites favors the dominance of epiphytic Fragilaria, Staurosira, and Staurosirella taxa. Bottom-living diatoms in the shallow eutrophic and hypereutrophic urban ponds are light-limited; this is a result of either macrophytes or phytoplankton development. Alkaliphilous and alkalibiontic species prevail among the pH-indicative species, while eutraphentic and hypereutraphentic diatoms, as well as those thriving in a wide range of trophic conditions, dominate over other trophic groups. The β- and α-mesosaprobic species are the most common saprobity-indicative taxa.     

Specific features of ecology of chars of the genus <Emphasis Type="Italic">Salvelinus</Emphasis> (Salmonidae) from the basin of Lake Kronotskoe (Kamchatka) according to parasitological data

A parasitological study was performed of chars of the genus Salvelinus inhabiting Lake Kronotskoe (Kamchatka Peninsula)—S. malma, S. albus, S. schmidtii, and S. kronocius, as well as of juvenile Salvelinus spp. Twenty-three species of parasites, including six species new for the lake, Hennequya zschokkei, Protteocephalus longicollis, Diphyllobothrium dendriticum, Crepidostomum sp., Echinorhynchus salmonis, and Paracanthobdella livanowi, were found. With consideration of published data, in chars of this water body, 28 species of parasites were recorded, including seven species (N. cf. pungitius, B. luciopercae, Crepidostomum sp., Cr. fausti, Cr. cf. cooperi, Eubothrium crassium, and Proteocephalus sp.), whose presence or species identification in the lake ecosystem need confirmation. Two species (N. rutili and Diphyllobothrium sp.) are removed from the list. Parasites common for all species of chars were revealed. They include Myxobolus arcticus, E. salvelini, D. ditretum, Crepidostotum sp., Cr. farionis, Cr. metoecus, Cystidicola farionis, Cucullanus truttae, Philonema oncorhynchi, and Salmincola carpionis. Cluster analysis of the fauna of parasites of different species of chars demonstrated considerable differences in infestation, which indicates differences between them in preference for food items and occupied biotopes and thereby supports the ecological differentiation of chars in the basin of Lake Kronotskoe. S. albus and S. kronocius are most similar in parasitofauna, which is determined by their predation; S. malma as a benthophage is infected by the same species of parasites, but considerably less intensively. Extremely high indices of population numbers of some parasite species are considered as a manifestation of the Krebs cycle in parasites under the conditions of an isolated lake.     

Predation on crown-of-thorns starfish larvae by damselfishes

Examining the functional response of predators can provide insight into the role of predation in structuring prey populations and ecological communities. This study explored feeding behaviour and functional responses of planktivorous damselfishes when offered captive reared larvae of crown-of-thorns starfish, Acanthaster sp., with the aim of determining whether these predators could ever play a role in moderating outbreaks of Acanthaster sp. We examined predatory behaviour of 11 species of planktivorous damselfish, testing: (1) the relationship between predator size and predation rate, both within and among fish species; (2) consumption rates on larvae of Acanthaster sp. versus larvae of a common, co-occurring coral reef asteroid Linckia laevigata; (3) maximal feeding rates upon both Acanthaster sp. and L. laevigata; and (4) functional responses of planktivorous fishes to increasing densities of Acanthaster sp. Consumption rates of crown-of-thorns larvae by damselfishes were independent of predator size; however, there was a significant negative relationship between predator size and consumption rate of L. laevigata, when pooling across all predatory species. Some damselfishes, including Acanthochromis polyacanthus and Amblyglyphidodon curacao, consumed larval Acanthaster sp. at a greater rate than for L. laevigata. Most predatory species (all except A. curacao and Pomacentrus amboinensis) exhibited a Type II functional response whereby the increasing feeding rate decelerated with increasing prey density. In addition to revealing that a wide range of planktivorous fishes can prey upon larvae of Acanthaster sp., these data suggest that planktivorous damselfishes may have the capacity to buffer against population fluctuations of Acanthaster sp. Importantly, predators with Type II functional responses often contribute to stability of prey populations, though planktivorous fishes may be swamped by an abnormally high influx of larvae, potentially contributing to the characteristic population fluctuations of Acanthaster sp.