Underwater observations of piranhas in western Brazil

Synopsis The behaviour of three piranha species,Serrasalmus marginatus, S. spilopleura, andPygocentrus nattereri, and their prey fishes was studied underwater in the Pantanal region, Mato Grosso, Brazil. General habits, predatory tactics, feeding behaviour, and social interactions while foraging, as well as defensive tactics of prey fishes were observed.S. marginatus is solitary whereas the other two species live in shoals; their agonistic behaviour varies accordingly, the simplest being displayed by the solitary species. Predatory tactics and feeding behaviour also vary:S. spilopleura shows the most varied diet and highly opportunistic feeding strategy, which includes aggressive mimicry. The solitaryS. marginatus, besides fin and scale-eating, occasionally cleans larger individuals ofP. nattereri. Several cichlid species display defensive tactics clearly related to piranha attacks: tail protecting, watching, and confronting the predator are the most commonly observed behaviours. Piranhas seem to strongly influence use of habitat, social structure, and foraging mode of the fish communities.     

Subsociality and female reproductive success in a mycophagous thrips: An observational and experimental analysis

Oviparous females of the haplodiploid, facultatively viviparous thrips Elaphrothrips tuberculatus(Thysanoptera: Phlaeothripidae) guard their eggs against female conspecifics and other egg predators. The intensity of maternal defense increases with clutch size. Field and laboratory observations indicate that cannibalism by females is an important selective pressure favoring maternal care. Experimental removals of guarding females showed that egg guarding substantially increases egg survivorship and that the survivorship of undefended eggs is higher in the absence of nonguarding female conspecifics than in their presence. The fecundity of viviparous females increases with the number of eggs cannibalized. The reproductive success of oviparous females increases with body size and local food density and decreases with local density of breeding females. Social behavior may not have advanced beyond maternal care in Elaphrothrips tuberculatusbecause, relative to Hymenoptera, capabilities for helping relatives are few or nonexistent, and the causes of variation in female reproductive success are not influenced easily by cooperation among females.     

Predator-induced behavioral defense and its ecological consequences for two calanoid copepods

Summary We used an automated technique for the observation and quantification of zooplankton swimming behavior to study the behavioral responses of two congeneric, herbivorous, freshwater copepod prey to a copepod predator (Limnocalanus macrurus). One prey, Diaptomus sicilis, often co-occurs with Limnocalanus, while previous studies indicated that the zoogeographic distribution of the second prey, Diaptomus oregonensis, was independent of the predator. We found that in the presence of Limnocalanus, D. sicilis swims more slowly and with less hopping and jumping than D. oregonensis. Diaptomus sicilis is also attacked and consumed by the predator Limnocalanus macrurus less frequently than D. oregonensis. We suggest that the faster, noisier swimming of D. oregonensis increases its vulnerability to Limnocalanus. The behavioral defenses to both prey are induced by the presence of the predator, and may represent two different anti-predator strategies, crypsis and avoidance for D. sicilis and D. oregonensis respectively. In a zoogeographical analysis D. oregonensis occurs at densities below D. sicilis in lakes where Limnocalanus is at elevated abundances, while in low-predator lakes the opposite is true. This distribution pattern supports our experimental results, and suggests that D. sicilis is adapted to survive with Limnocalanus, while D. oregonensis is not.     

Food habits and prey selection of three species of groupers from the genus Cephalopholis (Serranidae: Teleostei)

Synopsis This paper describes a study performed in the Gulf of Aqaba on food selectivity and hunting behaviour of three species of sympatric fish from the genusCephalopholis. These fishes occur in the shallow-water coral habitats of the Red Sea and feed on fishes and invertebrates. Of these,C. argus andC. miniata prefer selected fish species (95 and 86% of their diet respectively), whereasC. hemistiktos consumes more invertebrates (36%) and is less selective with respect to fish species. All three species employ various techniques to catch their prey and in situations where their elected food is absent they readily switch to substitute prey species.     

Decreased preference and reproduction, and increased mortality of Frankliniella occidentalis on thrips-resistant pepper plants

The effect of thrips resistance in pepper (Capsicum annuum L.) – previously shown to result in impeded thrips population development (Maris PC, Joosten NN, Goldbach RW & Peters D (2003a) Restricted spread of Tomato spotted wilt virus in thrips‐resistant pepper. Phytopathology 93: 1223–1227. Maris PC, Joosten NN, Goldbach RW & Peters D (2003b) Spread of Tomato spotted wilt virus and population development of Frankliniella occidentalis in pepper resistant to thrips. Proceedings of the Section Experimental and Applied Entomology Netherlands Entomological Society (NEV) Amsterdam 14: 95–101.) – on thrips’[Frankliniella occidentalis Pergande (Thysanoptera: Thripidae)] reproduction, mortality, host preference, and behaviour was investigated. Reproduction, studied by oviposition and larval survival, was negatively affected by the thrips‐resistant (TR) phenotype, whereas the offspring's developmental rate did not differ on TR and the thrips‐susceptible (TS) phenotype. While thrips’ behaviour was hardly affected by thrips resistance, a significant preference for TS plants over the TR plants was found in different tests. When released on either a TR or a TS plant, thrips dispersed at significantly higher rates from the TR plants, demonstrating that not only an impeded reproduction, but also a reduced residence time adds to the reported lower thrips numbers on TR plants.     

DECISION TOOLS FOR MULBERRY THRIPS PSEUDODENDROTHRIPS MORI (NIWA, 1908) MANAGEMENT IN SERICULTURAL REGIONS; AN OVERVIEW

Abstract Mulberry thrips Pseudodendrothrips mori (Niwa, 1908) is a major pest of mulberry trees recorded from different sericultural regions of the world. The thrips infestation affects the qualitative and quantitative characters of mulberry leaf, by direct feeding damage to leaves and the ingestion of sap, which in turn affects the silkworm cocoon crop. This is most harmful in dry climates and seasons when heavily attacked plants lose moisture heavily. Under these conditions infestation can seriously deplete yields. The seasonal population fluctuation and the degree of damage caused to the host plant are influenced by various environmental factors including climate, host-plant variety, topography, soil type, and management regimes. This article attempts to review all available documents on mulberry thrips and to discuss the practical approaches for best control of this pest.     

Screening Capsicum germplasm for resistance to tomato spotted wilt virus (TSWV)

Resistance conferred by the Tsw locus from Capsicum chinense against Tomato spotted wilt virus (TSWV) has been widely used in breeding programmes. Nevertheless, this resistance depends on inoculation conditions, and isolates able to overcome it have already been detected. In this work 29 accessions of several Capsicum species have been mechanically inoculated with TSWV to identify new sources of resistance. Five accessions showed variable percentages of resistant plants, two of which did not show local lesions on inoculated leaves, suggesting that the response was not mediated through hypersensitivity. Two of these accessions also had a remarkable reduced viral accumulation compared to susceptible control. ECU‐973., a C. chinense accession, showed the best performance against TSWV, with 100% resistant plants. This response was confirmed after mechanical inoculation with three different TSWV isolates. The resistance was maintained when the accession was inoculated with TSWV using a high pressure of viruliferous thrips. These results open new possibilities in the development of a durable resistance to TSWV in pepper.     

Improving the Control of Tetranychus urticae on Edible Glasshouse Crops Using a Specialist Coccinellid ( Stethorus punctillum Weise) and a Generalist Mite ( Amblyseius californicus McGregor) as Biocontrol Agents

Current glasshouse biological control practice relies on regular prophylactic introductions of one or two 'best' species of natural enemy. Whilst this is effective for much of the time, occasional failures occur due to factors such as differences in response to seasonal changes in environmental conditions and/or host plant effects. This study looks at the predatory behaviour of a specialist coccinellid, Stethorus punctillum Weise, and a generalist mite, Amblyseius californicus McGregor (which predate on the two-spotted spider mite, Tetranychus urticae ) in order to assess how they responded to temperatures and relative humidities typical of glasshouse conditions on four edible crop plant species. Activity (distance covered, time spent walking, walking speed, angular velocity, and turning rate) was recorded at 20, 25 and 30 o C and at relative humidity (RH) levels of 33, 65 and 90%, on tomato, pepper, aubergine and cucumber leaves, and analysed using video-computer techniques. The results show that the activity of S. punctillum significantly increased at higher temperature levels. Host plant species also strongly influenced the performance of the predator, with it being most active on pepper and tomato and least active on aubergines. RH had no significant influence. The activity and predation by A. californicus increased at low humidity levels, especially in terms of time spent moving and number of prey killed. Temperature levels had no significant influence, but host plant species strongly influenced the performance of the predator, which was most active on pepper, and least active on aubergines. Further research was conducted with semi-field trials to investigate the efficacy in controlling TSSM with different combination of predators. When contrasting the commercially available predatory mite Phytoseiulus persimilis , used alone, compared with its use in a treatment with a combination of predator species, there was a stronger decrease in TSSM numbers on the crop plants in the latter treatment.     

Monitoring insecticide resistance in Australian Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) detects fipronil and spinosad resistance

Abstract  Insecticide resistance monitoring using a Potter precision spray tower with discriminating concentration and log dose probability techniques underpins the Australian insecticide management strategy for Frankliniella occidentalis Pergande. Abamectin, acephate, chlorpyrifos, dichlorvos, dimethoate, endosulfan, fipronil, malathion, methamidophos methidathion, methiocarb, methomyl, pyrazophos and spinosad are recommended for use against F. occidentalis but abamectin, methiocarb and pyrazophos are the only chemicals where insecticide resistance has not been detected. Although not registered, chlorfenapyr was effective against F. occidentalis and should be pursued for that purpose. In contrast, chlorpyrifos, dichlorvos and malathion resistance were detected at low to moderate levels throughout the study period putting their sustainable use for F. occidentalis control in doubt . Although it appears that acephate, dimethoate, endosulfan, fipronil, methamidophos, methidathion and spinosad remain effective, some populations contained a small percentage of thrips that survived exposure to a concentration that killed 100% of the susceptible strain. Subsequent laboratory selection of one such population separately with fipronil and spinosad caused an increase in resistance to these insecticides. These products must now be considered at risk. This is the first report of fipronil or spinosad resistance in populations of F. occidentalis.     

COMPARATIVE ANALYSIS OF GALL MORPHOLOGY IN AUSTRALIAN GALL THRIPS: THE EVOLUTION OF EXTENDED PHENOTYPES

We used a combination of morphometric, phylogenetic, and life-history information to analyze the evolution and possible adaptive significance of gall morphology in a clade of 24 species of gall-inducing thrips (Insecta: Thysanoptera) on Australian Acacia trees. Principal components analysis revealed that galls varied in morphology along two main axes, spherical versus elongate (PC1) and general size (PC2). A high degree of conservation of gall shape on an independently derived phylogeny of the insects and the presence of nine species of Acacia each bearing two or three morphologically disparate gall forms induced by different thrips species indicate that interspecific variation in gall form is determined predominantly by the insects. Character optimization of PC1 on the phylogeny of gall thrips suggested that the ancestral gall form was a simple roll or curl. The diversification of gall form involved four main processes: (1) the convergent evolution of relatively spherical galls in two clades; (2) the evolution of small elongate and hemispherical galls in one clade; (3) the evolution of a lobed interior in a species with a spherical gall and multiple within-gall generations; and (4) the evolution of intraspecific gall polymorphism in a clade of apparent sibling species. Comparative analyses indicated that gall sphericity was associated with the presence of physogastry (foundress hyperfecundity) and that small elongate and hemispherical forms may be associated with the presence of multiple generations in a gall and, perhaps, with the presence of soldier castes. The evolution of a lobed interior in one species, which greatly increases inner surface area, coincided with the evolution of multiple generations. In the clade with intraspecific gall polymorphism in some species, patterns of intraspecific variation mirror patterns of interspecific variation within the clade as a whole. This is the first study to analyze the evolution of gall size and shape in a phylogenetic context and to investigate the life-history correlates of evolutionary changes in gall form. Taken together, our findings indicate that the main selective pressures driving the evolution of gall form in Australian gall thrips on Acacia involve inner surface area to volume relationships, which change in concert with foundress fecundity and the number of within-gall generations.