Participation of metanauplii and juvenile individuals of <Emphasis Type="Italic">Artemia parthenogenetica</Emphasis> (Branchiopoda) in the circulation of avian cestodes

Adult crustaceans of the genus Artemia (brine shrimps) are intermediate hosts in the life cycle of cestode species parasitic in aquatic birds as their definitive hosts. However, there are no data on the role of larval and juvenile brine shrimps in the transmission of avian helminth parasites. In order to examine the possible role of early developmental stages (nauplii, metanauplii and juveniles) of Artemia for the circulation of avian cestodes, the natural cestode infection in the population of Artemia parthenogenetica from La Mata Lagoon, Mediterranean coast of Spain, was studied. Metacestodes (cysticercoids) of four cestode species were recorded in adult brine shrimps: Flamingolepis liguloides and Flamingolepis flamingo (hymenolepidids parasitic in flamingos), Confluaria podicipina (a hymenolepidid species parasitic in grebes) and Eurycestus avoceti (a dilepidid species parasitic in avocets, stilts, plovers and, to a lesser extent, in flamingos). No cysticercoids were found in nauplii. Two species, F. liguloides and F. flamingo, were found in metanauplii and juvenile brine shrimps. Only 36.3% of the cysticercoids of F. liguloides occurred in adult brine shrimps; the remaining 63.7% were parasitic in metanauplii (39.6%) and juveniles (24.1%). Similarly, the metacestodes of F. flamingo were also distributed among various age groups: in adults (44.4% of cysticercoids), juveniles (27.8%) and metanauplii (27.8%). These results indicate that the early developmental stages of Artemia have an important role for the circulation of certain parasite species. No cysticercoids of C. podicipina and E. avoceti were recorded in larval and juvenile brine shrimps. The selective infestation of larval brine shrimps with flamingo parasites is probably associated with the feeding behaviour of definitive hosts, which are filtering predators; in contrast, grebes and waders pick brine shrimps individually one by one. The possible underlying mechanism for selective infestation of metanauplii and adults by certain cestode species is associated with the size of parasite eggs, allowing only cestode species with small eggs to be ingested by larval brine shrimps.     

Records of cysticercoids of Fimbriarioides tadornae Maksimova, 1976 and Branchiopodataenia gvozdevi (Maksimova, 1988) (Cyclophyllidea, Hymenolepididae) from brine shrimps at the Mediterranean coasts of Spain and France, with a key to cestodes from Artemia spp. from the Western Mediterranean

Cysticercoids of two cestode species isolated from brine shrimps from the Mediterranean coasts of Spain and France are described. Fimbriarioides tadornae Maksimova, 1976 (adults known as parasites of Tadorna tadorna) was recorded from Artemia parthenogenetica and A. franciscana from Spain (Bras del Port and River Ebro Delta, respectively), and from A. franciscana from Aigues-Mortes, France (new geographical record). Branchiopodataenia gvozdevi (Maksimova, 1988) (adults known as parasites of Larus genei) was recorded from A. parthenogenetica (Bras del Port, Spain), A. salina (San Pedro del Pinatar, Spain) and A. franciscana (River Ebro Delta, Spain); this is the first record of the species in Europe. An illustrated key to cysticercoids of 12 cestode species from Artemia spp. from the Western Mediterranean is proposed.     

High prevalence of cestodes in Artemia spp. throughout the annual cycle: relationship with abundance of avian final hosts

Brine shrimp, Artemia spp., act as intermediate hosts for a range of cestode species that use waterbirds as their final hosts. These parasites can have marked influences on shrimp behavior and fecundity, generating the potential for cascading effects in hypersaline food webs. We present the first comprehensive study of the temporal dynamics of cestode parasites in natural populations of brine shrimp throughout the annual cycle. Over a 12-month period, clonal Artemia parthenogenetica were sampled in the Odiel marshes in Huelva, and the sexual Artemia salina was sampled in the Salinas de Cerrillos in Almería. Throughout the year, 4–45 % of A. parthenogenetica were infected with cestodes (mean species richness?=?0.26), compared to 27–72 % of A. salina (mean species richness?=?0.64). Ten cestode species were recorded. Male and female A. salina showed similar levels of parasitism. The most prevalent and abundant cestodes were those infecting the most abundant final hosts, especially the Greater Flamingo Phoenicopterus ruber. In particular, the flamingo parasite Flamingolepis liguloides had a prevalence of up to 43 % in A. parthenogenetica and 63.5 % in A. salina in a given month. Although there was strong seasonal variation in prevalence, abundance, and intensity of cestode infections, seasonal changes in bird counts were weak predictors of the dynamics of cestode infections. However, infection levels of Confluaria podicipina in A. parthenogenetica were positively correlated with the number of their black-necked grebe Podiceps nigricollis hosts. Similarly, infection levels of Anomotaenia tringae and Anomotaenia microphallos in A. salina were correlated with the number of shorebird hosts present the month before. Correlated seasonal transmission structured the cestode community, leading to more multiple infections than expected by chance.     

Red and transparent brine shrimps (Artemia parthenogenetica): a comparative study of their cestode infections

Although the red colour of brine shrimps has previously been supposed to be associated with cestode parasitism, no evidence has been provided that red and transparent brine shrimps differ in their role for cestode circulation. We compared the cestode infections in 100 red and 100 transparent Artemia parthenogenetica collected from the Odiel salt pans in Spain. Seven cestode species were recorded in red, and only four of them were recorded in transparent brine shrimps. The red brine shrimps were more infected with cysticercoids than transparent individuals (prevalence, 87 vs 21%; mean intensity, 1.56 vs 1.00; mean abundance, 1.35 vs 0.21). Three cestode species (Flamingolepis liguloides, Anomotaenia tringae and Confluaria podicipina) had significantly higher prevalence and mean abundance in red brine shrimps. These results suggest that red brine shrimps have a more important role for the circulation of avian cestodes than transparent individuals of the same population.     

Larval helminths in the invasive American brine shrimp Artemia franciscana throughout its annual cycle

One of the best examples of rapid displacement of native species by an invader is the eradication of native Artemia salina and A. parthenogenetica in the Mediterranean by the introduced American A. franciscana. Previous studies based on sampling from limited time periods suggest that the success of the American species as a competitor may be due partly to different parasite burden, since native Artemia spp. have high cestode infection rates regulating their density. The aim of this study is to test the hypothesis that the helminth infection in A. franciscana in its invasive range is low throughout its annual life cycle. Samples of A. franciscana were collected every second month from La Tapa saltern (Andalusia) during one year. Five helminth species were recorded: cestodes Flamingolepis liguloides, F. flamingo, Gynandrotaenia stammeri (all flamingo parasites), Eurycestus avoceti (a shorebird parasite) and larval spirurids of the Acuariinae (the first record of nematodes in Artemia). The overall infection rate was low, with total prevalence 5.9% and prevalence of individual parasite species between 0.2 and 3.2%. The mean abundance of helminths was 0.005–0.155 (av. 0.068), 5–13 times lower than in native congeners. Waterbird counts indicate that the low infection rates cannot be explained by lack of definitive hosts. The results are consistent with the hypothesis that helminths have no regulating effect on the invasive brine shrimp in the Mediterranean. The replacement of the native populations by the invader can be partially explained by a competition mediated by parasites/predators through a differential impact on host fitness.     

The parasitism of <Emphasis Type="Italic">Flamingolepis liguloides</Emphasis> (Gervais, 1847) (Cestoda,Hymenolepididae) in <Emphasis Type="Italic">Artemia salina</Emphasis> (Crustacea,Branchiopoda) in two saline lakes in Algeria

Studies revealed the role of Artemia salina as intermediate host in the life-cycle of a cestode species parasitizing flamingos, i.e. Flamingolepis liguloides. Cysticercoids of this parasite were found for the first time in the Algerian populations of Artemia salina in winter of 2000 and 2001 in Chott Marouane and spring of 2003 in Sebkha Ez-Zemoul. The prevalence ranged between 10 and 33% for the two examined Artemia populations. The intensity of infection was 1–3 cysticercoids per individual. The abdomen was the most targeted site of infection (95% of the population of Sebkha Ez-Zemoul) followed by the thorax and the ovisac. Infected females were less fertile than uninfected ones (24.83 vs 43.70 cysts/brood) in Sebkha Ez-Zemoul or castrated in Chott Marouane.     

Molecular identification of <Emphasis Type="Italic">Trichuris vulpis</Emphasis> and <Emphasis Type="Italic">Trichuris suis</Emphasis> isolated from different hosts

Trichuris suis was isolated from the cecum of two different hosts (Sus scrofa domestica—swine and Sus scrofa scrofa—wild boar) and Trichuris vulpis from dogs in Sevilla, Spain. Genomic DNA was isolated and internal transcribed spacers (ITS)1-5.8S-ITS2 segment from the ribosomal DNA (rDNA) was amplified and sequenced using polymerase chain reaction techniques. The sequence of T. suis from both hosts was 1,396 bp in length while that of T. vulpis was 1,044 bp. ITS1 of both populations isolated of T. suis was 661 nucleotides in length, while the ITS2 was 534 nucleotides in length. Furthermore, the ITS1 of T. vulpis was 410 nucleotides in length, while the ITS2 was 433 nucleotides in length. One hundred fifty-four nucleotides were observed along the 5.8S gene of T. suis and T. vulpis. Intraindividual and intraspecific variations were detected in the rDNA of both species. The presence of microsatellites was observed in all the individuals assayed. Sequence analysis of the ITSs and the 5.8S gene has demonstrated no sequence differences between T. suis isolated from both hosts (S. scrofa domestica—swine and S. scrofa scrofa—wild boar). Nevertheless, clear differences were detected between the ITS1 and ITS2 of T. suis and T. vulpis. Furthermore, a comparative molecular analysis between both species and the previously published ITS1-5.8S-ITS2 sequence data of Trichuris ovis, Trichuris leporis, Trichuris muris, Trichuris arvicolae, and Trichuris skrjabini was carried out. A common homology zone was detected in the ITS1 sequence of all species of trichurids.     

Redescription of <Emphasis Type="Italic">Lemuricola</Emphasis> (<Emphasis Type="Italic">Madoxyuris</Emphasis>) <Emphasis Type="Italic">bauchoti</Emphasis> (Nematoda,Oxyuridae) from <Emphasis Type="Italic">Lemur catta</Emphasis> in Madagascar

Lemuricola (Madoxyuris) bauchoti Chabaud, Brygoo et Petter, 1965 is redescribed from material collected from the ring-tailed lemur, Lemur catta, from the Beza Mahafaly Special Reserve in Madagascar using the scanning electron microscope. This is a new host record and the first oxyurid reported from the ring-tailed lemur. Previously, records of each species of the subgenus Madoxyuris have been restricted to a single host species, but the close relationship between these nematodes and their Strepsirrhini hosts will only be proven when additional records fill in the gaps in their distribution.     

Spontaneous capture of oilseed rape (<Emphasis Type="Italic">Brassica napus</Emphasis>) chloroplasts by wild <Emphasis Type="Italic">B</Emphasis>. <Emphasis Type="Italic">rapa</Emphasis>: implications for the use of chloroplast transformation for biocontainment

Environmental concerns over the cultivation of Genetically Modified (GM) crops largely centre on the ecological consequences following gene flow to wild relatives. One attractive solution is to deploy biocontainment measures that prevent hybridization. Chloroplast transformation is the most advanced biocontainment method but is compromised by chloroplast capture (hybridization through the maternal lineage). To date, however, there is a paucity of information on the frequency of chloroplast capture in the wild. Oilseed rape (Brassica napus, AACC) frequently hybridises with wild Brassica rapa (AA, as paternal parent) and yields B. rapa-like introgressed individuals after only two generations. In this study we used chloroplast CAPS markers that differentiate between the two species to survey wild and weedy populations of B. rapa for the capture of B. napus chloroplasts. A total of 464 B. rapa plants belonging to 14 populations growing either in close proximity to B. napus (i.e. sympatric <5 m) or else were allopatric from the crop (>1 km) were assessed for chloroplast capture using PCR (trnL-F) and CAPS (trnT-L-Xba I) markers. The screen revealed that two sympatric B. rapa populations included 53 plants that possessed the chloroplast of B. napus. In order to discount these B. rapa plants as F₁ crop-wild hybrids, we used a C-genome-specific marker and found that 45 out of 53 plants lacked the C-genome and so were at least second generation introgressants. The most plausible explanation is that these individuals represent multiple cases of chloroplast capture following introgressive hybridisation through the female germ line from the crop. The abundance of such plants in sympatric sites thereby questions whether the use of chloroplast transformation would provide a sufficient biocontainment for GM oilseed rape in the United Kingdom.     

<Emphasis Type="Italic">P</Emphasis>. <Emphasis Type="Italic">aeruginosa</Emphasis> Biofilms in CF Infection

Pseudomonas aeruginosa is an opportunistic pathogen of immunocompromised hosts. In cystic fibrosis (CF), P. aeruginosa causes acute and chronic lung infections that result in significant morbidity and mortality. P. aeruginosa possesses several traits that contribute to its ability to colonize and persist in acute and chronic infections. These include high resistance to antimicrobials, ability to form biofilms, plethora of virulence products, and metabolic versatility. In P. aeruginosa, a cell-to-cell communication process termed quorum sensing (QS) regulates many of these factors that contribute to its pathogenesis. Recent evidence suggests that the CF lung environment presents a specialized niche for P. aeruginosa. The relationship of P. aeruginosa QS, biofilm formation, and the CF lung environment is discussed.     

Antiplasmodial activity of two marine polyherbal preparations from <Emphasis Type="Italic">Chaetomorpha antennina</Emphasis> and <Emphasis Type="Italic">Aegiceras corniculatum</Emphasis> against <Emphasis Type="Italic">Plasmodium falciparum</Emphasis>

The ocean covers more than 70% of earth surface and hosts most 300,000 described species of plants and animals to use, which have been virtually unexploited for the development of medicines. Marine plants are the good source of biologically active entities which exhibit therapeutic properties, when applied single or in combination of different plant extracts (polyherbal). Polyherbal preparations are always a complex mixture of different forms and thus different compounds, which might act as agonistic, synergistic, complementary, antagonistic or toxic way. The present study was initially carried out to test the antiplasmodial activity of 13 mangrove plants and eight seaweeds species distributed along the coast of south India. Of these, mangrove species Aegiceras corniculatum and the seaweed species Chaetomorpha antennina have shown maximum antiplasmodial activity. Hence, the present study was mooted out to increase the percentage of antiplasmodial activity when applied as polyherbal preparations. The effect of marine polyherbal preparations from the methanolic extracts of two marine plants A. corniculatum and C. antennina for their antiplasmodial activity was tested. It shows that the polyherbal extract showed 63.50 ± 0.408% suppression of parasitaemia against Plasmodium falciparum at 1.5 mg ml⁻¹ concentration. In vivo test was carried out with rat animal model to find out the effectiveness of the polyherbal extracts in the live system, which reveals that polyherbal extracts have exhibited remarkable antiplasmodial activity (50.57 ± 0.465%) against Plasmodium berghei at 120 mg kg⁻¹ bw. This study shows that combinations of mangrove plants and seaweeds extracts had a source of lead compounds for the development of new drugs for the treatment of malaria.     

Larvicidal,antimicrobial and brine shrimp activities of extracts from <Emphasis Type="Italic">Cissampelos mucronata</Emphasis> and <Emphasis Type="Italic">Tephrosia villosa</Emphasis> from coast region,Tanzania

Background  

The leaves and roots of Cissampelos mucronata A. Rich (Menispermaceae) are widely used in the tropics and subtropics to manage various ailments such as gastro-intestinal complaints, menstrual problems, venereal diseases and malaria. In the Coast region, Tanzania, roots are used to treat wounds due to extraction of jigger. Leaves of Tephrosia villosa (L) Pers (Leguminosae) are reported to be used in the treatment of diabetes mellitus in India. In this study, extracts from the roots and aerial parts of C. mucronata and extracts from leaves, fruits, twigs and roots of T. villosa were evaluated for larvicidal activity, brine shrimps toxicity and antimicrobial activity.     

Parasite fauna of farmed Nile tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>) and African catfish (<Emphasis Type="Italic">Clarias gariepinus</Emphasis>) in Uganda

An intensive parasite survey was conducted in 2008 to better understand the parasite fauna occurrence, distribution and diversity in the commercial aquaculture fish species in Uganda. A total of 265 fish collected from hatcheries and grow-out systems were examined for parasites using routine parasitological techniques. The survey yielded 17 parasite species: 11 from Oreochromis niloticus and ten from Clarias gariepinus. Four parasites—Amirthalingamia macracantha, Monobothrioides sp., Zoogonoides sp. and a member of the family Amphilinidae—were recorded for the first time in the country. The parasite diversity was similar between hosts; however, O. niloticus was dominated by free-living stage-transmitted parasites in lower numbers, whereas both trophically and free-living stage-transmitted parasites were equally represented in C. gariepinus in relatively high intensities. The patterns in parasite numbers and composition in the two hosts reflect differences in fish habitat use and diet. A shift in parasite composition from monoxenous species-dominated communities in small-sized fish to heteroxenous in large fishes was recorded in both hosts. This was linked to ontogenetic feeding changes and prolonged exposure to parasites. Polyculture systems showed no effect on parasite intensity and composition. The gills were highly parasitized, mainly by protozoans and monogeneans. Generally, the occurrence and diversity of parasites in these fish species highlight the likelihood of disease outbreak in the proposed intensive aquaculture systems. This calls for raising awareness in fish health management among potential farmers, service providers and researchers.     

<Emphasis Type="Italic">Thelohania montirivulorum</Emphasis> sp. nov. (Microspora: Thelohaniidae), a parasite of the Australian freshwater crayfish,<Emphasis Type="Italic"> Cherax destructor</Emphasis> (Decapoda: Parastacidae): fine ultrastructure,molecular characteristics and phylogenetic relationships

Thelohania montirivulorum sp. nov., a new species of microsporidian parasite, was found in a highland population of the Australian yabby, Cherax destructor. Data are presented on fine ultrastructure, developmental morphology and DNA sequence of the small subunit ribosomal DNA (SSU rDNA) and internal transcribed spacer region. The phylogenetic relationships of T. montrivulorum sp. nov. and other crayfish parasites in the genus Thelohania, based on the SSU rDNA sequence, are investigated. Fine ultrastructure, patterns of sporogony and SSU rDNA sequence similarities indicate T. montirivulorum sp. nov. is congeneric with T. parastaci, a parasite of lowland populations of C. destructor, and with T. contejeani, a parasite of European freshwater crayfish. SSU rDNA data suggests Thelohania species found in crustacean hosts are more closely related to the Vairimorpha/Nosema clade of species from insect and crustacean hosts than to the fire ant parasites, T. solenopsae and Thelohania sp.     

Mitochondrial genomes of the human broad tapeworms <Emphasis Type="Italic">Diphyllobothrium latum</Emphasis> and <Emphasis Type="Italic">Diphyllobothrium nihonkaiense</Emphasis> (Cestoda: Diphyllobothriidae)

Mitochondrial DNA (mtDNA) sequences of the human broad tapeworms Diphyllobothrium latum and Diphyllobothrium nihonkaiense have been totally determined. Both of them are closed circular molecules (total length, 13,720 bp in D. latum and 13,747 bp in D. nihonkaiense) containing genes for 12 proteins, 22 transfer RNAs, and two ribosomal RNAs. All the genes are coded on T-rich strand. The gene order of Diphyllobothrium mtDNAs is completely identical with that of Taenia and Echinococcus mtDNAs. The overall A + T contents of the genomes are 68.3% in D. latum and 67.8% in D. nihonkaiense. The pairwise divergence values of nucleotide sequences between these tapeworms ranged from 0.069 to 0.152 in protein-coding genes, demonstrating that D. nihonkaiense is a distinct species. The sequences determined in this study may provide useful marker systems for diagnostic, epidemiological, and phylogeographical studies of human diphyllobothriasis.     

Possible involvement of <Emphasis Type="Italic">Artemia</Emphasis> as live diet in the transmission of cryptosporidiosis in cultured fish

The viability of Cryptosporidium parvum oocysts ingested by Artemia franciscana metanauplii was evaluated using two fluorogenic vital dyes. There was no significant difference (p = 0.09) between the viability of oocysts maintained in saline (control) and those recovered from the digestive tract of the microcrustacean 24 h after ingestion (95 vs 90% viable oocysts). The results suggest that Artemia, used as a life food in fish larviculture, may act as a vehicle for transmission of piscine cryptosporidiosis caused by Cryptosporidium molnari and Cryptosporidium scophthalmi.     

Larvicidal activity of silver nanoparticles synthesized using <Emphasis Type="Italic">Plumeria rubra</Emphasis> plant latex against <Emphasis Type="Italic">Aedes aegypti</Emphasis> and <Emphasis Type="Italic">Anopheles stephensi</Emphasis>

In the present study activity of silver nanoparticles (AgNPs) synthesized using Plumeria rubra plant latex against second and fourth larval instar of Aedes aegypti and Anopheles stephensi was determined. Range of concentrations of synthesized AgNps (10, 5, 2.5, 1.25, 0.625, 0.3125 ppm) and aqueous crude latex (1,000, 500, 250, 125, 62.50, 31.25 ppm) were tested against larvae of A. aegypti and A. Stephensi. The synthesized AgNps from P. rubra latex were highly toxic than crude latex extract in both mosquito species. The LC₅₀ values for second and fourth larval instars after 24 h of crude latex exposure were 1.49, 1.82 ppm against A. aegypti and 1.10, 1.74 ppm against A. stephensi respectively. These figures were 181.67, 287.49 ppm against A. aegypti and 143.69, 170.58 ppm against A. stephensi respectively for crude latex extract. The mortality rates were positively correlated with the concentration of AgNPs. The characterization studies of synthesized AgNPs by UV–Vis spectrophotometry, transmission electron microscopy (TEM), Particle size analysis (PSA) and zeta potential confirmed the spherical shape and size (32–200 nm) of silver nanoparticles alongwith stability. Toxicity studies carried out against non-target fish species Poecilia reticulata, the most common organism in the habitats of A. aegypti and A. stephensi showed no toxicity at LC₅₀ and LC₉₀ doses of the AgNPs. This is the first report on mosquito larvicidal activity of latex synthesized nanoparticles.     

Identification and characterization of a novel <Emphasis Type="Italic">Tritimovirus</Emphasis> species isolated from wild <Emphasis Type="Italic">Trisetum flavescens</Emphasis> L., family <Emphasis Type="Italic">Poaceae</Emphasis>

Yellow oat-grass plants (Trisetum flavescens L.) with mild mosaic and pronounced dwarfing symptoms were observed at different locations in the Czech Republic. Electron microscope observations of symptomatic plants revealed the presence of filamentous particles and inclusion bodies characteristic of the family Potyviridae. The virus was readily mechanically transmitted to its original host plus a narrow host range of monocot species. Serological assays of infected plant extracts using antiserum specific to the closest species in the family Potyviridae were negative. The 3′ end of the viral genome was cloned, sequenced and compared to sequences of species in the family Potyviridae. The virus is more closely related to viruses in the genus Tritimovirus than to other genera within the Potyviridae. Based on phylogenetic analyses of the coat protein cistron and flanking genomic regions, we propose this is a distinct viral species of the genus Tritimovirus, tentatively named Yellow oat-grass mosaic virus (YOgMV).     

Anurans as paratenic hosts in the transmission of <Emphasis Type="Italic">Hepatozoon caimani</Emphasis> to caimans <Emphasis Type="Italic">Caiman yacare</Emphasis> and <Emphasis Type="Italic">Caiman latirostris</Emphasis>

Prevalence of Hepatozoon caimani has been reported in 76% of caimans Caiman yacare from the Pantanal region. Culex (Melanoconion) spp. mosquitoes were recently identified as natural vectors of this parasite. However, culicids are not typically eaten by crocodilians, suggesting that the main transmission route is through ingestion of insectivorous vertebrates, such as anurans. The susceptibility of wild frogs Leptodactylus chaquensis, Leptodactylus podicipinus and Scinax nasicus to infection by H. caimani was verified. Wild-caught anurans were force fed with sporulated oocysts from laboratory-bred Culex (Melanoconion) mosquitoes. Frogs were killed 30 days postinfection, and their internal organs were fed to caimans C. yacare and Caiman latirostris. Cystozoites were identified in fresh liver impression smears of L. chaquensis. C. yacare fed on anuran organ presented gametocytes in peripheral blood circulation between 74 and 80 days postinoculation (dpi). Gametocytes were also verified in C. latirostris fed on the internal organs of L. podicipinus and S. nasicus between 60–70 and 69–75 dpi, respectively. Since frogs used in experiment are sympatric with C. yacare and C. latirostris and may occur in the diet of these caimans, the results suggest these amphibians are paratenic hosts in the natural transmission cycle of H. caimani in Pantanal.     

Effect of bacterial symbionts <Emphasis Type="Italic">Xenorhabdus</Emphasis> on mortality of infective juveniles of two <Emphasis Type="Italic">Steinernema</Emphasis> species

Steinernema species are entomopathogenic nematodes associated with Xenorhabdus bacteria. The life cycle of these associations is composed of two stages: (1) a free stage in the soil, where infective juveniles (IJs), which carry bacteria in their guts, search for new insect hosts; and (2) a parasitic stage, where the IJs infect insects, release their Xenorhabdus symbionts and reproduce in order to produce new IJs. Previous studies clearly showed benefits to the association for several Steinernema species during the parasitic stage. Nevertheless, no study has so far explored, during the free stage, the existence of costs or benefits to the association for different Steinernema. Here, we compared the survival of both symbiotic and aposymbiotic IJs in two nematode species: (1) Steinernema carpocapsae-exhibiting IJs that carry a high number of Xenorhabdus cells in their guts; and (2) its closely relative species, S. scapterisci-exhibiting IJs, that carry very few Xenorhabdus cells in their guts. We showed that the bacterial symbionts were costly for S. carpocapsae by increasing IJs’ mortality but not for S. scapterisci. This difference in cost induced by bacteria to IJs during the free stage could be correlated with the difference in the numbers of bacteria carried by IJs of each nematode species.