A study on seasonal populations of potato leafhoppers in Kerman province of Iran

This study of potato leafhoppers population dynamics was conducted in Kerman province during 2005–2007. In this study Mahan, Bardsir and Lalehzar as the principal potato growing areas of Kerman province were selected. Sampling commenced at 40 days after planting on 8 June in Lalehzar region, 30 days after planting on 8 May in Bardsir and 55 days after planting on 4 May in Mahan. According to the results of this study 11 species belong to 11 genus; three families and six subfamilies were collected from three potato growing areas (Lalehzar, Bardsir, Mahan) during 2005–2007 and identified as follows: Empoasca decipiens, Psammotettix striatus, Unkanodes tanasijevici, Sogatella vibix, Exitianus fasciolatus, Euscelis alsius, Reptalus lindbergi, Pseudophlepsius binotatus, Circulifer sp., Macrosteles sp., Idiocerus sp. Statistical analysis revealed that Empoasca decipiens was the most abundant species in potato fields in Lalehzar, Bardsir and Mahan regions.     

Nomenclatural changes in Cicadellidae: Typhlocybinae?and Delphacidae (Homoptera)

New replacement names are proposed for seven species of the subfamily Typhlocybinae; one new synonym is recognized in the family Delphacidae. The following changes are proposed: Empoasca (Empoasca) angustata nom.nov. for Empoasca angusta Linnavuori & DeLong (not Dworakowska); Empoasca (Empoasca) chilensis nom.nov. for Empoasca diversa Linnavuori & DeLong (not Vilbaste); Austroasca verdensis nom.nov. for Empoasca artemisiae Lindberg (not Lethierry); Kropka vidanoi Dworakowska for Erythroneura unipunctata Dlabola (not Cerutti); Zyginella vietnamica nom. nov. for Zyginella melichari Dworakowska (not Kirkaldy); Eupteryx (Eupteryx) dlabolai nom. nov. for Eupteryx octonotata Dlabola (not Hardy); Baaora ahmedi nom. nov. for Baaora spinosa (Ahmed) (not Beamer); Paradelphacodes insolitus Dmitriev is synonymized with Paradelphacodes gvosdevi (Mitjaev), syn. nov.     

Italian neo-endemism in a widespread group of leafhoppers insects: A revision of the Eupteryx aurata group (Auchenorrhyncha: Cicadellidae: Typhlocybinae) using morphology,ecology and genetics

The Eupteryx aurata group is characterised by several features, primarily by colouration and aedeagus morphology. It is distributed mainly in Europe, with some species also in Asia and one species perhaps in North Africa. At least one species is introduced in North America. Until now 12 taxa were known. Two new species, Eupteryx divulsa from central Italy and Eupteryx oscorum from central and southern Italy, are described in this paper. Eupteryx petasitidis Ferrari, 1882, described as Eupteryx carpini petasitidis and later synonymised with Eupteryx atropunctata (Goeze, 1778), is reestablished on species level and redescribed including genital morphology. Ten taxa of the species group are studied in relation to their morphological and molecular characters. The colouration, aedeagus, and pygofer appendage are figured for all of these taxa. Molecular study showed that the E. aurata group is monophyletic. The little or moderate distances in sequences (below 6.0% for mtDNA and up to 2.5% for nuclear ITS2) between the different taxa of the E. aurata group and incongruence of genetic signals from mtDNA and nuclear DNA could be the result of incomplete lineage sorting in young species and/or hybridisation and introgression of DNA among taxa. Of particular importance in this study is material from Italy, a peripheral region in relation to the distribution of the species group and due to its geomorphological features favouring isolation and speciation. A distribution map for the E. aurata species group in Italy and an identification key for all 15 taxa of the aurata group are given. Phylogenetic relationships within the aurata group are discussed in relation to morphological, molecular, ecological, and zoogeographic aspects.     

Host plant specificity, oviposition behaviour and egg parasitism in some leafhoppers of the genus Eupteryx (Hemiptera: Cicadellidae)

Abstract.

• 1 Three species of Eupteryx, E.aurata, E.cyclops and E.urticae are regularly found on stinging nettles in South Wales.
• 2 E.aurata host alternates between nettles in spring and autumn, and Heraclewn, Eupatorium and Mentha species in summer. E.cyclops and E.urticae attack only nettles.
• 3 All species are host specific during oviposition and show preferences to lay eggs in discrete plant regions.
• 4 A Mymarid egg parasite of the genus Anagrus was reared more commonly from eggs laid in nettles than from eggs laid in alternative hosts.

     

Searching and Oviposition Behavior of Anagrus atomus L. (Hymenoptera: Mymaridae) on Four Host Plants of Its Host, the Green Leafhopper Empoasca decipiens Paoli (Homoptera: Cicadellidae)

Anagrus atomus L. is an important egg parasitoid of the green leafhopper Empoasca decipiens Paoli. In this study the ability of the parasitoid to locate and parasitize its host was investigated on four host plants, i.e., broad beans (Vicia faba L.), sweet pepper (Capsicum annuum L.), cucumber (Cucumis sativus L.), and French beans (Phaseolus vulgaris L.). For each plant species, the behavior of the parasitoid was observed on E. decipiens infested and noninfested plants. Searching and oviposition behavior were characterized by drumming, probing, and resting. Parasitoids spent significantly less time on non-infested than infested plants, 274.5 and 875.7 s, respectively, and no probing behavior was observed on non-infested plants. Frequency of resting behavior was significantly greater on non-infested than on infested plants. Total foraging time was significantly longer on infested than on non-infested plants, indicating that A. atomus females can efficiently discriminate between leaves with and without infestation. Parasitism of A. atomus was influenced by parasitoid density, with the highest parasitism rate (64.0%) obtained at a density of 10 A. atomus females/0.1356 m² but the number of parasitized eggs per female and the searching efficiency decreased with increasing parasitoid density.     

Pseudoterranova decipiens species A and B (Nematoda,Ascaridoidea): nomenclatural designation,morphological diagnostic characters and genetic markers

Five genetically distinct and reproductively isolated species have been detected previously within the morphospecies Pseudoterranova decipiens from the Arctic-Boreal, Boreal and Antarctic. Morphological analysis was carried out on male specimens identified by genetic (allozyme) markers, allowing the detection of significant differences at a number of characters between two members of the P. decipiens complex, namely P. decipiens A and B. On the basis of such differences, the nomenclatural designation for the two species is discussed. The names Pseudoterranova krabbei n. sp. and P. decipiens (sensu stricto) are proposed for species A and B, respectively. Morphological and genetic differentiation between the two species is shown using multivariate analysis. Allozyme diagnostic keys for routine identification of the four members of the P. decipiens complex, namely P. decipiens (s.s.), P. krabbei, P. bulbosa and P. azarasi, irrespective of sex and life-history stage, are provided.     

Autumnal emergence of Anagrus wasps,egg parasitoids of Empoasca vitis,from grapevine leaves and their migration towards brambles

• 1 The Anagrus‘atomus’ parasitoid group (Hymenoptera: Mymaridae), associated with Empoasca vitis (Göthe) (Homoptera: Cicadellidae), overwinters on vegetation surrounding vineyards. The emergence of parasitoid adults from grapevine leaves in autumn was studied in north‐eastern Italy, both in relation to the E. vitis egg‐laying period and to the presence of leafhoppers overwintering as eggs on Rubus bushes.
• 2 Autumnal peaks of Anagrus captured using yellow sticky traps were observed first on grapevines and then on brambles. Parasitoid captures in vineyards were observed for more than 1 month after the last first‐instar nymphs of the grape leafhoppers were noticed. Two species belonging to the A. ‘atomus’ group, Anagrus atomus and Anagrus ustulatus, were captured both on grapevines and brambles.
• 3 Parasitoids of the A.‘atomus’ group can emerge from third‐generation grape leafhopper eggs in accordance with two different development time patterns (i.e. normal or delayed). Individuals with delayed emergence required up to 2.2‐fold more time to develop from an egg to adult than individuals with normal emergence. This meant that some parasitoid adults emerged in autumn from eggs of grape leafhopper laid in August.
• 4 A delayed emergence as a result of a slower development ensures that the A.‘atomus’ parasitoid group is synchronized with the egg‐laying of leafhoppers that overwinter as eggs on Rubus spp.
• 5 Consequently, leafhoppers overwintering as eggs on brambles play a key role in the ecology of the relationship between grape leafhoppers and the A.‘atomus’ parasitoid group.

     

Background matching behaviour and pathogen acquisition: plant site preference does not predict the bacterial acquisition efficiency of vectors

Many insect-borne pathogens are heterogeneously distributed within their hosts: therefore, a vector’s within-plant distribution may be a predictor of its exposure to pathogens. In this study, we set out to quantify plant site preference, in the context of background matching, and investigated its effect on acquisition of a bacterial pathogen by its leafhopper vectors. The two green-coloured species, Graphocephala atropunctata and Draeculacephala minerva, preferred green plant tissue and artificial backgrounds whereas the brown-coloured Homalodisca vitripennis preferred brown stem tissue and backgrounds. Within-plant feeding site did not predict either the acquisition success or the number of plant-pathogenic Xylella fastidiosa cells acquired by the vectors; an 86% mortality for G. atropunctata was reported on the lignified stem tissue. Overall, H. vitripennis acquired significantly more cells than G. atropunctata. A novel artificial diet-based transmission system was used to further illustrate that the observed between-species difference in the number of cells acquired was independent of vector-host plant interactions. H. vitripennis, a less efficient vector of the bacterium X. fastidiosa on grapevines, acquired more bacterial cells than G. atropunctata, possibly due to its larger size. Contrary to previous assumptions, pathogen acquisition efficiency by the vectors did not explain their reported differences in inoculation. Vector interactions with the host during the inoculation stage should be evaluated as another determinant of X. fastidiosa transmission efficiency.     

Influence of plot characteristics and surrounding vegetation on the intra-plot spatial distribution of Empoasca vitis

• 1 Spatial distributions of adults and nymphs of Empoasca vitis were assessed during 3 years inside two adjacent vine plots having considerable intra‐plot variability, diversified natural ground cover and surrounding vegetation, and no insecticide application.
• 2 Geostatistical analysis confirmed that, in spite of repeated adult migrations, spatial distributions of summer populations were highly aggregated, similar every year and similar between adults and nymphs. Comparison of insect distribution with intra‐plot characteristics, such as vine plant vigour (leaf density and leaf chlorophyll concentration) and phenology, plot topography and surrounding vegetation, revealed that E. vitis clearly aggregates in areas with the most vigorous vine plants.
• 3 Even though the presence of natural enemies in the surrounding vegetation was confirmed by specific observations, we did not observe significant population decrease at the contiguous plot edges. Natural ground cover, together with the absence of insecticide, might allow the spreading and perennial conservation of E. vitis natural enemies inside the plots.
• 4 Clear adult aggregations observed along downwind woodlands suggest that this vegetation acts as a barrier and intercepts the adults flying passively across the plot. However, this surrounding vegetation could also serve as an alternative refuge when vine water deficit and vine foliage temperature increase.

     

Occurrence of Pseudoterranova decipiens (Nematoda) in fish from the Southeastern Weddell Sea (Antarctic)

Eleven fish species from the Weddell Sea (Antarctic) were examined for infestation with anisakid nematodes. Two species of the genus Contracaecum and the sealworm Pseudoterranova decipiens were isolated from the liver and the body cavity of fish affected. Only two specimens of P. decipiens (1.4%) partly invaded the belly flaps. The following fish species were infested by P. decipiens at the given prevalences: Cygnodraco mawsoni (74.4%), Trematomus scotti (23.2%), Pagetopsis maculatus (10.0%), Cryodraco antarcticus (7.1%), Trematomus lepidorhinus (3.0%), and Dolloidraco longedorsalis (2.7%). All of these, except Trematomus scotti, are new host records. Chaenodraco wilsoni, Chionodraco myersi, Gerlachea australis, Racovitzia glacialis and T. eulepidotus were not infested. The reasons for low prevalence and intensity of infestation are seen in the difficulties of P. decipiens in completing its benthic life cycle in the Weddell Sea environment, in the absence of shallow coastal waters due to the floating shelf-ice. Cygnodraco mawsoni is a crucial intermediate host, without which completion of the parasite life cycle might not be possible. In order to clarify the taxonomical position of Antarctic Pseudoterranova, morphological comparisons with specimens of P. decipiens from the German and Norwegian coast were made using scanning electron microscopy. Results revealed no differences; hence, all specimens studied belong to the same species P. decipiens.     

Albinism in plants – far beyond the loss of chlorophyll: Structural and physiological aspects of wild‐type and albino royal poinciana (Delonix regia) seedlings

• The partial or complete loss of chlorophylls, or albinism, is a rare phenomenon in plants. In the present study, we provide the first report of the occurrence in albino Delonix regia seedlings and describe the morpho‐physiological changes associated with albinism.
• Wild‐type (WT) and albino seedlings were characterized. Leaflets samples were processed following common procedures for analysis with light, scanning and transmission electron microscopy. The chlorophyll a fluorescence parameters and the carbohydrate, lipid and soluble protein content were also determined in leaf and cotyledon samples of both albino and WT seedlings.
• Albino seedlings showed reduced growth. They also had lower chlorophyll and protein content in foliar tissues than WT seedlings, in addition to lower concentrations of lipids and carbohydrates stored in cotyledons. The chloroplasts of albino seedlings were poorly developed, with an undefined internal membrane system and the presence of plastoglobules. Wild‐type seedlings had a uniseriate and hypoestomatic epidermis. The mesophyll was dorsiventral, consisting of a layer of palisade parenchyma and two to four layers of spongy parenchyma. In albino seedlings, the spongy parenchyma was compact, with few intercellular spaces, and the thickness of the mesophyll was larger, resulting in increased thickness of the leaf blade. Albino seedlings had higher stomatal density and number of pavement cells, although the stomata had smaller dimensions.
• In addition to the partial loss of chlorophylls, albino D. regia showed changes at physiological and structural levels, demonstrating the crucial nature of photosynthetic pigments during the development and differentiation of plant leaf tissues/cells.

     

pEffects of UV radiation on the ultrastructure of several red algae

The effect of ultraviolet (UV) radiation on the ultrastructure of four red algae, the endemic Antarctic Palmaria decipiens (Reinsch) Ricker and Phycodrys austrogeorgica Skottsberg, the Arctic‐cold temperate Palmaria palmata (Linnaeus) O. Kuntze and the cosmopolitan Bangia atropurpurea (Roth) C. Agardh was studied. All four species showed a formation of ‘inside‐out’ vesicles from the chloroplast thylakoids upon exposure to artificial UV‐radiation. In P. decipiens, most vesicles were developed after 8 h and in P. palmata, after 48 h of UV exposure. In B. atropurpurea, vesi‐culation of thylakoids was observed after 72 h of UV irradiation. In Ph. austrogeorgica, the chloroplast envelope and thylakoid membranes were damaged and the phycobilisomes became detached from the thylakoids after 12 h of UV exposure. Ultraviolet‐induced changes in the membrane structure of mitochondria were observed in P. decipiens and P. palmata. However, in P. decipiens they were reversible as was the damage in chloroplast fine structure after 12 h of UV treatment. Protein crystals in Ph. austrogeorgica showed degradation after exposure to UV radiation. Different methods of fixation and embedding macroalgal material are discussed. These findings give insight into the fine structural changes which occur during and after UV exposure and indicate a relationship between the species dependent sensitivity to UV‐exposure and the depth distribution of the different species.     

Water relations in silver birch during springtime: How is sap pressurised?

• Positive sap pressures are produced in the xylem of birch trees in boreal conditions during the time between the thawing of the soil and bud break. During this period, xylem embolisms accumulated during wintertime are refilled with water. The mechanism for xylem sap pressurization and its environmental drivers are not well known.
• We measured xylem sap flow, xylem sap pressure, xylem sap osmotic concentration, xylem and whole stem diameter changes, and stem and root non‐structural carbohydrate concentrations, along with meteorological conditions at two sites in Finland during and after the sap pressurisation period.
• The diurnal dynamics of xylem sap pressure and sap flow during the sap pressurisation period varied, but were more often opposite to the diurnal pattern after bud burst, i.e. sap pressure increased and sap flow rate mostly decreased when temperature increased. Net conversion of soluble sugars to starch in the stem and roots occurred during the sap pressurisation period. Xylem sap osmotic pressure was small in comparison to total sap pressure, and it did not follow changes in environmental conditions or tree water relations.
• Based on these findings, we suggest that xylem sap pressurisation and embolism refilling occur gradually over a few weeks through water transfer from parenchyma cells to xylem vessels during daytime, and then the parenchyma are refilled mostly during nighttime by water uptake from soil. Possible drivers for water transfer from parenchyma cells to vessels are discussed. Also the functioning of thermal dissipation probes in conditions of changing stem water content is discussed.

     

Mechanisms of hydraulic conductivity in the leaf galls of Meunieriella sp. (Cecidomyiidae) in Avicennia schaueriana (Acanthaceae): does vascularization explain the preferred sites of induction?

• Intralaminar galls of Meunieriella result from ground tissue proliferation in leaves of Avicennia schaueriana, a typical halophytic mangrove. We tested if the preferred sites of gall induction were the midribs and secondary veins (SV) at the basal leaf portion, where the galls were expected to be largest; and if the vascular system in galls and adjacent regions was altered to favour water supply in galls, thus increasing their growth.
• Gall induction sites and gall sizes were quantified according to leaf portions and regions. Anatomical and histometric analyses in vascular and ground tissues of galls and adjacent regions were compared to equivalent regions of non-galled leaves.
• The galls were largest at basal sites on leaves, the midrib and SV. More galls occurred on the apical portion of the leaf, and on the leaf blade and secondary vein regions. Changes in shape and vascular system area, number and diameter of vessel elements were detected in both galls and adjacent regions. Fewer and smaller-sized vessel elements were observed in regions proximal to the galls and inside them.
• Gall size is not related with preferred induction sites, which could be explained by factors such as thermal balance. Alterations in the vascular system indicate reduced hydraulic conductivity in the xylem in the proximal region and inside galls, leading to water leakage to gall parenchyma cells. This compensatory mechanism explains the expansion and proliferation of water storage and spongy parenchyma cells in the galls, explaining the higher growth in more vascularized regions.

     

Effects of Macroalgal Chemical Extracts on Spore Behavior of the Antarctic Epiphyte Elachista antarctica Phaeophyceae

Most macroalgal species along the Western Antarctic Peninsula (WAP) are defended against predation, many using chemical defenses. These subtidal communities are also mostly devoid of free living filamentous algae. However, one endo/epiphyte, Elachista antarctica, is found growing exclusively out of the palatable rhodophyte Palmaria decipiens. To understand this unusual and exclusive epiphytization, we tested whether macroalgal secondary metabolites such as those responsible for deterring sympatric grazers, affect the behaviors of the epiphyte's spores. Settlement, germination, and swimming behaviors of the epiphyte's motile spores were quantified in the presence of fractionated lipophilic and hydrophilic extracts of host P. decipiens and other rhodophytes from the shallow subtidal. Host P. decipiens was the only alga tested that did not inhibit spore settlement or germination. We also examined whether extracts from these chemically rich algae affect spore swimming behaviors and found spores to be chemotactically attracted to seawater soluble extract fractions of host P. decipiens. These results indicate that chemosensory behaviors of the epiphyte's spores to metabolites associated with these chemically defended macrophytes can explain this exclusive epiphyte–host interaction.     

The morphology and activity of the extrafloral nectaries in Reynoutria × bohemica (Polygonaceae)

• Reynoutria × bohemica is an invasive species causing significant damage to native ecosystems in North America and Europe.
• In this work, we performed an in‐depth micromorphological characterisation of the extrafloral nectaries (EFN), during their secretory and post‐secretory phases, in combination with field monitoring of nectary activity over time and the qualitative pool of insect visitors.
• EFN consist of secretory trichomes and vascularised parenchyma. Polysaccharides, lipids and proteins were histochemically detected in all trichome cells; phenolic substances were detected in parenchyma cells. Our data indicate that all nectary regions are involved in nectar production and release, constituting a functional unit. Moreover, the main compound classes of nectar and their transfer change over time: first, granulocrine secretion for sugars prevails, then eccrine secretion of the lipophilic fraction takes place. Active nectaries are mainly located in the apical portion of the stem during the growth phase (April–May), when we detected the highest number of individuals visited by ants; from mid‐August onwards, during flowering, the number of active nectaries declined then ceased production (September), with a concomitant decrease in visits by the ants. The spectrum of nectar‐foraging ants mainly included representatives of the genera Formica, Lasius and Camponotus.
• Reynoutria × bohemica produces an attractive secretion able to recruit local ants that may potentially act as ‘bodyguards’ for protecting young shoots, reducing secretions during the blooming stage. This defence mechanism against herbivores is the same as that displayed by the parental species in its native areas.

     

Top‐down regulation of filamentous cyanobacteria varies among a raptorial versus current feeding copepod across multiple prey generations

1. Although considered a key functional trait, little is known about how zooplankton feeding mode affects top‐down regulation of phytoplankton communities. Indeed, copepods are expected to promote the dominance of toxic phytoplankton by selective removal of their edible competitors; however, empirical evidence comparing the effect among calanoid and cyclopoid copepods is lacking.
2. We compared the top‐down effects of two copepods with contrasting feeding modes—the calanoid Notodiaptomus iheringi (current feeder) and the cyclopoid Thermocyclops decipiens (ambush feeder) — on the relative and absolute biomass of the filamentous cyanobacterium Raphidiopsis raciborskii co‐cultured with the nutritious eukaryotic phytoplankton Cryptomonas obovata in a week‐long laboratory assay.
3. The current feeder had a stronger top‐down effect on the biomass of both prey throughout the experiment, with mass‐specific clearance rates 3–5× higher than ambush feeder. By the end of the experiment, the current feeder significantly reduced cyanobacteria biomass compared to controls while the ambush feeder did not. During the week‐long experiment, the current feeder switched from grazing on edible prey to cyanobacteria as the former became less abundant.
4. Contrary to expectation, neither of the copepod species promoted cyanobacterial dominance by the end of the experiment. This is because both grazers, but especially the current feeder, initially increased but subsequently decreased the relative contribution of cyanobacteria to total phytoplankton biomass. Moreover, both copepods decreased the length of cyanobacteria filaments by c. 70%
5. Current feeders can switch from edible prey to cyanobacteria when the abundance of shortened filaments surpasses the abundance of edible prey. While top‐down regulation of phytoplankton can be stronger for current feeding copepods, ambush feeding copepods can have a significant role during blooms by shortening cyanobacterial filaments. Hence, the broader role of contrasting copepod feeding traits on phytoplankton communities merits further study.

     

ACCLIMATION OF PHOTOSYNTHESIS AND PIGMENTS DURING AND AFTER SIX MONTHS OF DARKNESS IN PALMARIA DECIPIENS (RHODOPHYTA): A STUDY TO SIMULATE ANTARCTIC WINTER SEA ICE COVER1

The influence of seasonally fluctuating photoperiods on the photosynthetic apparatus of Palmaria decipiens (Reinsch) Ricker was studied in a year‐round culture experiment. The optimal quantum yield (F_v/F_m) and the maximal relative electron transport rate (ETR_max), measured by in vivo chl fluorescence and pigment content, were determined monthly. During darkness, an initial increase in pigment content was observed. After 3 months in darkness, ETR_max and F_v/F_m started to decrease considerably. After 4 months in darkness, degradation of the light‐harvesting antennae, the phycobilisomes, began, and 1 month later the light harvesting complex I and/or the reaction centers of PSII and/or PSI degraded. Pigment content and photosynthetic performance were at their minimum at the end of the 6‐month dark period. Within 24 h after re‐illumination, P. decipiens started to accumulate chl a and to photosynthesize. The phycobiliprotein accumulation began after a time lag of about 7 days. Palmaria decipiens reached ETR_max values comparable with the values before darkness 7 days after re‐illumination and maximal values after 30 days of re‐illumination. Over the summer, P. decipiens reduced its photosynthetic performance and pigment content, probably to avoid photodamage caused by excess light energy. The data show that P. decipiens is able to adapt to the short period of favorable light conditions and to the darkness experienced in the field.     

Experimental studies on the response of the fish (Notothenia coriiceps Richardson, 1844) to parasite (Pseudoterranova decipiens Krabbe, 1878) and other irritant stimuli at Antarctic temperatures

In order to better understand the immune response of Notothenia coriiceps to Pseudoterranova decipiens larvae and other irritant stimuli, we implanted a catgut suture thread, killed P. decipiens larvae and macerated P. decipiens larvae in the hepatic and muscle tissues of the fish. The response varied according to the tissue concerned and the extent of the lesion. The most noticeable immune response occurred with the implant of parasite larvae macerate in the liver, which indicates immunological memory, since all the captured fish were found infected with P. decipiens. An intense response also occurred after macrophages had infiltrated the cuticle of the implanted dead parasite in the liver, which confirms that the cuticle acts as a physical barrier to the immune system. Nevertheless, the immune response of N. coriiceps does not appear able to eliminate the infection and the fish in nature appear to suffer no adverse clinical effects. Accepted: 19 June 1999     

Host plant intraspecific variation determines gall traits

• Galls display a multiplicity of traits, including colours, which are driven by pigment accumulation. Their conspicuousness has attracted researchers' attention and several hypotheses have been raised. However, plants themselves vary intra-specifically, including in their pigment concentrations. As galls are a result of host tissue development, colours may be a by-product of the host's own traits, being more conspicuous simply because the sites where galls develop already have the predisposition to accumulate more pigment. Here, we call this the host variation hypothesis.
• We test this hypothesis using the system of galls induced by Palaeomystella oligophaga on Macairea radula host plant. Using spectrophotometry, we calculated the Anthocyanin Reflectance Index (ARI) of gall projections, which are responsible for their characteristic colours. We tested the influence of occupant identity (galling insect or any natural enemy), gall volume, parenchyma thickness, height from the ground, ARI of leaf, ARI of gall surface and ARI of the respective stem.
• We corroborated the host variation hypothesis since the anthocyanin content in stems and in galls' projections were positively related. Moreover, anthocyanin in galls' projections was positively related to anthocyanin in the gall surface and negatively related to gall volume and parenchyma thickness. This shows that, besides the host specificities, galls' own traits may also be responsible for pigment accumulation, influencing their colours.
• In this study, using colour as an example, we show that although galls tend to be considered complex expressions of galling insects' stimuli, their traits may be simply influenced by previous and specific attributes of the host organs.