Solitary terminal cells of Aphanizomenon gracile (Cyanobacteria,Nostocales) can divide and renew trichomes

An attempt was made to find evidence that morphologically distinct terminal cells of filamentous cyanobacterium Aphanizomenon gracile strain CCALA 8 are capable of dividing and forming trichomes. Based on our current knowledge, the division of morphologically diversified terminal cells is possible in nostocalean cyanobacteria. However, this process has been observed only in a few species. Terminal cells of A. gracile differ morphologically from other vegetative cells of a trichome, as they are not hyaline and can sometimes be found as solitary cells in cultures. Hence, it was reasonable for us to suspect that these cells are capable of dividing and forming trichomes. We observed terminal cells under a light and transmission electron microscope. Microscopic observations revealed that the septum formed in both solitary terminal cells and in terminal cells attached to trichomes. Our study is the first to demonstrate division and renewal of trichomes in terminal cells of A. gracile. Previously, such mode of reproduction was described only for another nostocalean cyanobacterium Raphidiopsis mediterranea. Moreover, our findings further emphasize the variability among members that belong to the genus Aphanizomenon , in which a type species (A. flos‐aquae) has hyaline cells incapable of dividing and renewing trichomes, while A. gracile can additionally propagate by solitary terminal cells division. This additional feature distinguishing A. gracile from typical species of Aphanizomenon, such as A. flos‐aquae, might be valuable for resolving taxonomic position of the species considering ambiguous genetic relationship between A. gracile and A. flos‐aquae.     

HYBRID ZONES AND HOST-PARASITE RELATIONSHIPS: EFFECT ON THE EVOLUTION OF PARASITIC SPECIFICITY

In southern France, Diplozoon gracile (Monogenea, Polyopisthocotylea), parasitizes four sympatric cyprinids. One of these host species, Barbus meridionalis, naturally hybridizes with another species of barbel, Barbus barbus, which is never parasitized by D. gracile under natural conditions. This hybridization has previously been studied and described as an introgression of B. barbus by B. meridionalis. The hybrids are parasitized by D. gracile, and parasite prevalence increases in proportion to the introgression rate, i.e., the percentage of B. meridionalis genes. The causes for this preferential distribution of the parasite in the hybrid population are analysed on the basis of ecological and ethological differences between the two parent species.     

Comparison of surface topography of three species of Diphyllobothrium (Cestoda,pseudophyllidea) by scanning electron microscopy

Plerocercoids of different sizes as well as adult worms of D. dendriticum, D. latum and D. ditremum were studied using scanning electron microscopy (S.E.M.). In the plerocercoids there were found distinct differences in appearance and length of microtriches between these three species, while the microtriches of adult worms were more similar. A regional difference in microtrix appearance was found in the larvae of D. ditremum and D. dendriticum. This was not apparent with S.E.M. in adult worms. The length of ‘body’ microtriches in D. dendriticum varied with the length of the larvae. The topography of the genital atrium of mature and gravid proglottids in adult worms of these three species is also described.     

Nematodes found in Nile crocodiles in the Kruger National Park,South Africa,with redescriptions of Multicaecum agile (Wedl, 1861) (Heterocheilidae) and Camallanus kaapstaadi Southwell & Kirshner, 1937 (Camallanidae)

Sixteen Nile crocodiles were collected in the Kruger National Park, South Africa and vicinity during 2010 and 2011. A total of 11 nematode species representing six families were recovered. Heterocheilids were the dominant group, comprising five species, with Dujardinascaris madagascariensis (Chabaud & Caballero, 1966) being the most prevalent (75%), followed by Ingwenascaris sprenti Junker & Mutafchiev, 2017 (68.8%), which was also the second most numerous nematode. While less prevalent (31.3%), Typhlophoros kwenae Junker & Mutafchiev, 2017 was the most abundant species. Micropleura huchzermeyeri Junker & Mutafchiev, 2017 (Micropleuridae) was collected from five crocodiles and Crocodylocapillaria sp. (Capillariidae) occurred in a single host. Three nematodes, Camallanus kaapstaadi Southwell & Kirshner, 1937, Spirocamallanus sp. (both Camallanidae) and Ascarophis sp. (Cystidicolidae), are considered accidental infections, likely ingested with the hosts’ prey. Our findings of D. dujardini (Travassos, 1920), D. madagascariensis and Multicaecum agile (Wedl, 1861) in South Africa constitute new geographical records. Crocodylocapillaria sp. represents a new host and geographical record, while T. kwenae, I. sprenti and M. huchzermeyeri have been described as new species during the course of this survey. Multicaecum agile is here redescribed based on light and scanning electron microscopy. Previously undescribed morphological characters of C. kaapstaadi, typically a parasite of Xenopus spp. (Amphibia: Pipidae), but here found in two Nile crocodiles, are also presented.

     

A multiyear survey of helminths from wild saddleback (Leontocebus weddelli) and emperor (Saguinus imperator) tamarins

The establishment of baseline data on parasites from wild primates is essential to understand how changes in habitat or climatic disturbances will impact parasite–host relationships. In nature, multiparasitic infections of primates usually fluctuate temporally and seasonally, implying that the acquisition of reliable data must occur over time. Individual parasite infection data from two wild populations of New World primates, the saddleback (Leontocebus weddelli) and emperor (Saguinus imperator) tamarin, were collected over 3 years to establish baseline levels of helminth prevalence and parasite species richness (PSR). Secondarily, we explored variation in parasite prevalence across age and sex classes, test nonrandom associations of parasite co‐occurrence, and assess the relationship between group size and PSR. From 288 fecal samples across 105 individuals (71 saddleback and 34 emperor tamarins), 10 parasite taxa were identified by light microscopy following centrifugation and ethyl‐acetate sedimentation. Of these taxa, none were host‐specific, Dicrocoeliidae and Cestoda prevalences differed between host species, Prosthenorchis and Strongylida were the most prevalent. Host age was positively associated with Prosthenorchis ova and filariform larva, but negatively with cestode and the Rhabditoidea ova. We detected no differences between expected and observed levels of co‐infection, nor between group size and parasite species richness over 30 group‐years. Logistic models of individual infection status did not identify a sex bias; however, age and species predicted the presence of four and three parasite taxa, respectively, with saddleback tamarins exhibiting higher PSR. Now that we have reliable baseline data for future monitoring of these populations, next steps involve the molecular characterization of these parasites, and exploration of linkages with health parameters.     

Developmental Stages of Trypanosoma (Megatrypanum) freitasi Rego, Magalhaes & Siqueira, 1957 in the Opossum Didelphis marsupialis (Marsupialia, Didelphidae)

Trypanosoma (Megatrypanum) freitasi, a parasite of marsupials of the genus Didelphis, has been found to undergo in the lumen of the scent (anal) glands of its vertebrate host, a cycle such as usually occurs in the intestinal tract of the insect vectors of trypanosomatids and similar to what has been reported for Trypanosoma (Schizotrypanum) cruzi. The invertebrate host of Trypanosoma freitasi is still unknown. Developmental stages of the trypanosome in its mammalian host, especially the dividing epimastigotes, multinucleate plasmodial forms and rosettes found in the lumen of the scent glands of a naturally infected Didelphis marsupialis are described and illustrated.     

The distribution of intertidal algae in a Hebridean Loch

Summary

Ten species of Rhopalostroma are currently known and all are from either Africa or Asia. Rhopalostroma gracile D. Hawksw. and R. kanyae Whalley &; Thienhirun have previously been reported from Thailand. A further species, R. lekae sp. no v., is now described from Thailand. Thus three out of the eleven known species of Rhopalostroma are from Thailand.     

Nematode lungworms of two species of anuran amphibians: evidence for co-adaptation

Genetic studies have indicated that some parasite species formerly thought to be generalists are complexes of morphologically similar species, each appearing to specialize on different host species. Studies on such species are needed to obtain ecological and parasitological data to address whether there are fitness costs in parasitizing atypical host species. We examined whether lungworms from two anuran host species, Lithobates sylvaticus and Lithobates pipiens, differed in measures of infection success in L. pipiens recipient hosts. We also determined if the worms from the two host species were sources of genetically resolvable species of morphologically similar nematodes. Sequences of internal transcribed spacer and lsrDNA regions of adult lungworms from each host species indicated that worms from L. sylvaticus matched Rhabdias bakeri, whereas worms from L. pipiens matched Rhabdias ranae. Our work suggested that these morphologically similar species are distant non-sibling taxa. We infected male and female metamorphs experimentally with lungworm larvae of the two species. We observed higher penetration, higher prevalence and higher mean abundance of adult worms in lungs of male and female metamorphs exposed to R. ranae larvae than in lungs of metamorphs exposed to R. bakeri larvae. Furthermore, metamorphs exposed to R. ranae larvae carried larger adult female worms in their lungs. Some variation in infection measures depended on host sex, but only for one parasite species considered. Overall, the differential establishment and reproductive potential of R. ranae and R. bakeri in L. pipiens suggests co-adaptation.     

Host–parasite relationships of Rhabdochona kidderi Pearse, 1936 (Nematoda: Rhabdochonidae) in fishes of the Lacantún River in the Lacandon rain forest of Chiapas State, southern Mexico, with a key to Mexican species of Rhabdochona Railliet, 1916

For the first time, the nematode Rhabdochona kidderi kidderi Pearse, 1936 (Rhabdochonidae) was recorded from fishes of the Lacantún River (Usumacinta River basin) in the Lacandon rain forest, Chiapas State, southern Mexico. Amphilophus nourissati (Allgayer) and Theraps irregularis Günther (both Perciformes: Cichlidae) were found to be the only definitive hosts in the locality, whereas Eugerres mexicanus (Steindachner) (Perciformes: Gerreidae), Ariopsis sp., Cathorops aguadulce (Meek) and Potomarius nelsoni (Evermann & Goldsborough) (all Siluriformes: Ariidae), Ictalurus furcatus (Valenciennes) (Siluriformes: Ictaluridae) and Strongylura hubbsi Collette (Beloniformes: Belonidae) all harboured the nematode’s fourth-stage larva and only served as paratenic hosts. All these fish species represent new host records for this parasite. The morphology of both adults and larvae was studied in detail by light and scanning electron microscopy, and some conspecific museum specimens from three other host species were also examined for comparison. Rhabdochona ictaluri Aguilar-Aguilar, Rosas-Valdez & Pérez-Ponce de León, 2010 is considered here to be a junior synonym of R. kidderi kidderi. A high degree of the variability of some morphological and biometrical features (deirid shape, left spicule length) and an unusually wide range of hosts suggest that R. kidderi may represent a species complex, but further studies are necessary in this respect. A key to Rhabdochona species and subspecies occurring in Mexico is provided.     

New,known and unidentified species of Eulimdana (Nematoda): additional information on biologically unusual filarioids of charadriiform birds

Eulimdana spp. were found in 13 of 32 species of charadriiform birds from North America and Iceland; 88 of 636 adult birds and seven of 72 juvenile birds harboured infections. Described are: E. andersoni n. sp. from Chlidonias niger; E. metcalforum n. sp. from Sterna hirundo; E. sonini n. sp. from Charadrius hiaticula; E. wongae n. sp. from Limosa fedoa; and E. bainae n. sp. from Numenius phaeopus. Eulimdana asperum Bartlett, Anderson, & Bush, 1989 is reported for the second time in its type-host, Phalaropus tricolor. The emerging pattern of one parasite species to one host species suggests that most Eulimdana species are strongly host specific. However, E. florencae Bartlett & Anderson, 1990 is reported for the first time in a second species of Calidris (C. alba) and may be the unidentified species found in C. bairdii, C. alpina and C. pusilla. Other unidentified species were found in Larus pipixcan, Arenaria interpres and Recurvirostra americana. A key to species-groups (three are proposed) and species of Eulimdana in charadriiforms is given. Two pieces of evidence support an earlier suggestion that infections are acquired by neo-natal charadriiforms: (1) the presence of E. wongae in a bird captured as a chick and examined after two months in captivity; and (2) a greater frequency of mixed sex infections with microfilariae in infected juvenile birds (four of seven) than in infected adult birds (five of 88). The latter also supports an earlier suggestion that post-reproductive worms are ephemeral.     

Olfaction in the Colorado potato beetle: Ultrastructure of antennal sensilla inLeptinotarsa sp

Sensillae on the antennae of the Colorado potato beetle,Leptinotarsa decemlineata are described using scanning (SEM) and transmission (TEM) electron microscopy and compared with SEM observations of antennal sensilla inL. haldemani andL. texana. In all the three species, 13 distinct sensillar types were identified with a higher density of sensilla in the more polyphagous species,L. decemlineata than in the moderately host specificL. haldemani and the highly host specificL. texana. Cuticular specializations and the predominance of olfactory sensilla are discussed in relation to host specificity in the three species.     

<Emphasis Type="Italic">Mycena</Emphasis> sp., a mycorrhizal fungus of the orchid <Emphasis Type="Italic">Dendrobium officinale</Emphasis>

An endophytic fungus, F-23, was isolated from the roots of Dendrobium officinale Kimura et Migo, an endangered Chinese medicinal plant. The sequence of the ITS region indicated that the isolate belongs to the genus Mycena. After 4 months of inoculation, the root systems of D. officinale that were inoculated with F-23 fungus were much larger than the control’s root systems. We also observed that the hyphae of F-23 penetrated the epidermal cells within the host’s roots and spread from cell to cell. A large number of pelotons existed in the root cortical cells of D. officinale inoculated with F-23 fungus. Intracellular hyphae crossing through the host walls were also observed using SEM (scanning electron microscopy). In contrast, light microscopy and SEM showed that the transverse sections of the roots of control plants remained uncolonized. Therefore, the F-23 fungus can form mycorrhizal associations with the roots of its host plant, D. officinale, and enhance the growth of seedlings and roots. In brief, Mycena sp. was identified and shown to be a mycorrhizal fungus of the epiphytic orchid, D. officinale. This might be of potential use to the mass cultivation of D. officinale under artificial conditions.     

Morphological and phylogenetic analyses of <Emphasis Type="Italic">Uromyces appendiculatus</Emphasis> and <Emphasis Type="Italic">U. vignae</Emphasis> on legumes in Japan

Uromyces appendiculatus, inclusive of three varieties, is distinguished from U. vignae primarily by the position of urediniospore germ pores and putative host specificity. However, opinions concerning these morphological and physiological features as taxonomic characters have varied greatly, and distinction of these species has often been confused. To clarify the taxonomy of these two species, morphological features of urediniospores and teliospores of 225 rust fungus specimens on species of Phaseolus, Vigna, Apios, Lablab, and Dunbaria were examined by light microscopy and scanning electron microscopy. Forty-five specimens were subjected to molecular phylogenetic analyses. As a result, the position of germ pores in urediniospores and the teliospore-wall thickness were considered as good characters to separate three morphological groups. In molecular analyses, the specimens fell into two and three clades based on the nucleotide sequence at D1/D2 domain of LSU rDNA and ITS regions, respectively. One of the D1/D2 clades corresponded to one morphological group whereas another D1/D2 clade included two other morphological groups. In contrast, each of the three ITS clades corresponded to a separate morphological group. Neither morphological groups nor molecular clades were host limited. It is suggested that the three morphological groups that corresponded to three distinct ITS clades constitute distinct species.Contribution no. 186 from the Laboratory of Plant Parasitic Mycology, Institute of Agriculture and Forestry, University of Tsukuba, Japan     

A new species of <Emphasis Type="Italic">Stephanopodium</Emphasis> (Dichapetalaceae) from eastern Brazil

A new species of Stephanopodium (Dichapetalaceae) from tabuleiro forests in southern Bahia is here described and illustrated. This species, named Stephanopodium gracile because of its slender habit, is compared to S. blanchetianum and S. organense. From these two species, S. gracile can be distinguished by the inflorescences on the apical portion of the leaf petiole, young branches with sparse short appressed trichomes, and glabrous leaves; from S. blanchetianum it differs also by leaf blades with an acuminate (vs. usually obtuse or rounded, and sometimes acute) apex.     

The root-nodule symbiosis between Sarothamnus scoparius L. and its microsymbionts

When nitrogen fixing root nodules are formed, Sarothamnus scoparius (broom) is inoculated with its microsymbionts. Nodules studied under light and electron microscopy exhibited typical indeterminate nodule histology with apical, persistent meristem, age gradient of nodule tissues, and open vascular bundles, and also with some particular features such as: the presence of mitotic activity in the infected meristematic cells, lack of infection threads, distribution of bacteria by process of host cell division, and occurrence of a large bacteroid zone only with infected cells. The results of cross-inoculation tests have shown a broad host range for S. scoparius microsymbionts including not only the native host but also species such as: Lupinus luteus, Ornithopus sativa, Lotus corniculatus, Genista tinctoria, Chamaecitisus ratisbonensis, Macroptilium atropurpureum, and Phaseolus vulgaris. In addition, our data established a close symbiotic relationship of S. scoparius nodulators to Bradyrhizobium sp. (Lupinus) by comparison of the partial sequence of nodC gene of the strain CYT7, specific for the broom, to those from Bradyrhizobium sp. (Lupinus) strain D1 and others available in the public databases.     

Paradiplozoon homoion Bychowsky & Nagibina, 1959 versus P. gracile Reichenbach-Klinke, 1961 (Monogenea): two species or phenotypic plasticity?

Specimens of the Paradiplozoon homoion-complex were collected from ten species of cyprinid fish in the Czech Republic. A combined molecular and morphometric approach was performed to distinguish Paradiplozoon homoion and P. gracile. The second internal transcribed spacer (ITS2) of the ribosomal RNA genes was amplified and sequences were analysed. No variability in the analysed sequences was detected. Measurements of clamps and the central hooks obtained from specimens from different host species were compared. Great variability was found in the length and width of the third pair of clamps. No significant differences were detected in the measurements of the central hook sickle. A positive relationship was found between host size and each of the following measurements of the third pair clamps: length and width of the whole clamp; and length of the median plate of the third pair of clamps. The length of the median plate of the attachment clamps may be a useful character for species identification of diplozoids. Further molecular and morphometric studies are required to resolve this taxonomic problem and, henceforth, we suggest considering P. gracile as a species inquirenda.     

Contrasting effects of habitat discontinuity on three closely related fungivorous beetle species with diverging host‐use patterns and dispersal ability

Understanding how landscape structure influences biodiversity patterns and ecological processes are essential in ecological research and conservation practices. Forest discontinuity is a primary driver affecting the population persistence and genetic structure of forest‐dwelling species. However, the actual impacts on populations are highly species‐specific. In this study, we tested whether dispersal capability and host specialization are associated with susceptibility to forest discontinuity using three closely related, sympatric fungivorous ciid beetle species (two host specialists, Octotemnus assimilis and O. crassus; one host generalist, O. kawanabei). Landscape genetic analyses and the estimation of effective migration surfaces (EEMS) method consistently demonstrated contrasting differences in the relationships between genetic structure and configuration of forest land cover. Octotemnus assimilis, one of the specialists with a presumably higher dispersal capability due to lower wing loading, lacked a definite spatial genetic structure in our study landscape. The remaining two species showed clear spatial genetic structure, but the results of landscape genetic analyses differed between the two species: while landscape resistance appeared to describe the spatial genetic structure of the specialist O. crassus, genetic differentiation of the generalist O. kawanabei was explained by geographic distance alone. This finding is consistent with the prediction that nonforest areas act more strongly as barriers between specialist populations. Our results suggest that differences in host range can influence the species‐specific resistance to habitat discontinuity among closely related species inhabiting the same landscape.     

Use of immunocytochemical staining of somatostatin for correlative light and electron microscopic investigation of D cells in the pancreatic islet of Xiphophorus helleri H. (Teleostei)

Summary Somatostatin-containing cells have been demonstrated by immunocytochemistry in semithin sections of the pancreatic islet of the teleost fish, Xiphophorus helleri. These cells were shown by correlative light and electron microscopy to be identical with D cells previously defined in this species by the silver impregnation method of Hellman and Hellerström.Supported in part by grants from the British Council and from the Medical Research Council of Great Britain     

Sarcocystis cruzi: comparative studies confirm natural infections of buffaloes

Controversy exists concerning whether cattle and water buffalo sustain infections with cysts of distinct arrays of species in the genus Sarcocystis. In particular, morphologically similar parasites have been alternately ascribed to Sarcocystis cruzi or to Sarcocystis levinei, depending on their occurrence in cattle or water buffalo. We used light and transmission electron microscopy, genetic analysis, and experimental infections of definitive canine hosts to determine whether consistent differences could be identified from parasites derived from several natural infections of each host, examining several tissue types (esophagus, skeletal muscles, and heart). Cysts derived from cattle and water buffalo shared similar structure; variation among 18S rRNA sequences did not segregate consistently according to intermediate host type; parasites derived from cattle and water buffalo induced similar outcomes in the canine definitive host. One cattle specimen harbored unusually large (macroscopic) sarcocysts which nonetheless conformed to previously reported ultrastructural and genetic features of S. cruzi. Finding no consistent basis to differentiate between them, we conclude that the parasites infecting each host and tissue type correspond to S. cruzi. In our sample, no phylogenetically distinct taxon was sampled which might correspond to a distinct taxon previously described as S. levinei. Either that taxon was missed by our sampling effort, or it may represent a junior synonym to S. cruzi, which would then cycle between dogs and a broader range of intermediate bovine hosts than was previously considered.     

Larval aquatic and terrestrial mites infesting a temperate assemblage of mosquitoes

We collected 22,769 adult female mosquitoes, representing 27 species, from light traps in Norfolk, Virginia (2006–2007) and examined them to assess infestation by larval mites. Mosquitoes were parasitized by two species of aquatic (Acari: Arrenuridae: Arrenurus) and three species of terrestrial mites (Acari: Erythraeidae). The prevalence of infestation varied from 0.55% (2006) to 0.17% (2007). The mean intensity of parasitism ranged from 3.6 mites per host (2006) to 1.8 mites per host (2007). The most common host species for aquatic mites was Culex erraticus, while the most common host for terrestrial mites was Anopheles quadrimaculatus. Relationships between biotic and abiotic factors were investigated in an attempt to provide insight into temporal, spatial, and interspecific variation in mite–mosquito interactions. Scanning electron microscopy was used to examine the mode of attachment for larval mites. While the prevalence of aquatic mite parasitism was correlated for Culex erraticus, the invasive mosquito, Aedes albopictus, was never parasitized through the duration of the study. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.