Leucocytozoon atkinsoni n. sp. (Apicomplexa: Leucocytozoidae) from the avian family Timaliidae

Investigators of haematozoa of the Timaliidae have reported the presence of two species of Leucocytozoon Berestneff, 1904, i.e. L. liothricis Laveran & Marullaz, 1914 and L. timaliae Bennett, Earlé & Pierce, 1993. Blood films collected from 42 wild-caught babblers in Madagascar were stained and examined for the presence of haematozoa using a compound microscope. To date, no species of avian haematozoa have been reported from babblers in Madagascar, although haematozoa have been observed. In the present study, we report a new species of Leucocytozoon, L. atkinsoni n. sp., whose morphometrics fall between those reported for the two previously described species from timaliids. The parasite is capped by the host cell nucleus covering 38% of its perimeter. L. atkinsoni n. sp. was found to have a marked, intensely staining, nucleolus as well as vacuoles in the parasite cytoplasm, in contrast to both L. liothricis and L. timaliae. Remnants of the host cell cytoplasm are commonly observed in cells infected with L. atkinsoni, a characteristic not reported in association with either of the previously described species from these hosts.     

Life Cycle of Hammondia hammondi (Apicomplexa: Sarcocystidae) in Cats

Hammondia hammondi and Toxoplasma gondii are feline coccidians that are morphologically, antigenically, and phylogenitically related. Both parasites multiply asexually and sexually in feline intestinal enterocytes, but H. hammondi remains confined to enterocytes whereas T. gondii also parasitizes extra‐intestinal tissues of the cat. Here, we studied multiplication of H. hammondi in feline intestine and compared with T. gondii cycle. Five parasite–free cats were inoculated orally with tissue cysts and free bradyzoites from skeletal muscles of gamma interferon gene knockout mice and killed at 1, 3, 4, 6, and 7 d later. At 1 and 3 d post inoculation (DPI), numerous individual intracellular bradyzoites were detected in histological sections of small intestine. At 4 DPI only schizonts were found and they were located in enterocyte cytoplasm above the host cell nucleus. At 6 and 7 DPI both schizonts and gamonts were seen and they were located in enterocytes. Ultrastucturally, schizogonic and gametogonic development of H. hammondi was similar to T. gondii. However, in H. hammondi merozoites rhoptries were longer, and coiled and contained more micronemes than in T. gondii. Ultrastructural development is illustrated in detail.     

Morphological and molecular characterizations of the Gregarina sp. (Apicomplexa: Protozoa) parasitizing on Phaedon brassicae (Coleoptera: Chrysomelidae)

A gregarine parasite (Eugregarinida: Gregarinidae) was observed in the population of daikon leaf beetle, Phaedon brassicae Baly, (Coleoptera: Chrysomelidae) in Korea. Gregarines are well known species-specific parasites of various Arthropoda. This Gregarina sp. also confirmed a species-specific parasite in P. brassicae. Based on 1.727 kb of 18S rDNA sequence (FJ481523), this gregarine species was grouped in eugregarine and a 5.258 kb of full length rDNA replicon was cloned (JF412715). We also observed interaction of trophozoite or gamonto of gregarine and epithelium of a host midgut using a light microscope and a scanning electron microscope. Although the developmental period of the infected host is delayed half a day in every larval stage, there was no significant difference in the developmental period of P. brassicae whether Gregarina sp. was infected or not. Gregarina sp. was a kind of facultative parasite from P. brassicae. This is the first report of a gregarine parasite in P. brassicae.     

Morphology and Phylogenetic Position of Two New Gregarine Species (Apicomplexa: Eugregarinorida) Parasitizing the Lubber Grasshopper Taeniopoda centurio (Drury, 1770) (Insecta: Orthoptera: Romaleidae) in Mexico

Eugregarines are understudied apicomplexan parasites of invertebrates inhabiting marine, freshwater, and terrestrial environments. Most currently known terrestrial eugregarines have been described parasitizing the gut from less than 1% of total insect diversity, with a high likelihood that the remaining insect species are infected. Eugregarine diversity in orthopterans (grasshoppers, locusts, katydids, and crickets) is still little known. We carried out a survey of the eugregarines parasitizing the Mexican lubber grasshopper, Taeniopoda centurio, an endemic species to the northwest of Mexico. We described two new eugregarine species from the gut of the host: Amoebogregarina taeniopoda n. sp. and Quadruspinospora mexicana n. sp. Both species are morphologically dissimilar in their life‐cycle stages. Our SSU rDNA phylogenetic analysis showed that both species are phylogenetically distant to each other, even though they parasitize the same host. Amoebogregarina taeniopoda n. sp. clustered within the clade Gregarinoidea, being closely related to Amoebogregarina nigra from the grasshopper Melanoplus differentialis. Quadruspinospora mexicana n. sp. clustered within the clade Actinocephaloidea and grouped with Prismatospora evansi, a parasite from dragonfly naiads. Amoebogregarina taeniopoda n. sp. and Q. mexicana n. sp. represent the first record of eugregarines found to infect a species of the family Romaleidae.     

Invasion and Early Development of Sarcocystis muris (Apicomplexa,Sarcocystidae) in Tissue Cultures1

Ultrastructural observations on the invasion and early development of merozoites (bradyzoites) of Sarcocystis muris in Madin-Darby canine kidney (MDCK) cells are presented. Invading merozoites cause the host cell plasmalemma to invaginate; they form a membrane junction (moving junction) and move into the host cell where they are enclosed in a primary parasitophorous vacuole (PV). Within 30–45 min after becoming intracellular, merozoites begin to vacate the newly established primary PV and move, forming a new membrane junction, into a secondary PV. Simultaneously with the movement of the parasite, the contents of dense granules in the apical part of the merozoites are shed by exocytosis into the lumen of the developing secondary PV. A lamella of the endoplasmic reticulum of the host cell becomes attached to the PV membrane, forming a PV limited by three host cell membranes.     

Sophisticated Adaptations of Gregarina cuneata (Apicomplexa) Feeding Stages for Epicellular Parasitism

Background

Gregarines represent a very diverse group of early emerging apicomplexans, parasitising numerous invertebrates and urochordates, and are considered of little practical significance. Recently, they have gained more attention since some analyses showed that cryptosporidia are more closely related to the gregarines than to coccidia.

Methodology/Principal Findings

Using a combined microscopic approach, this study points out the spectacular strategy of Gregarina cuneata for attachment to host tissue and nutrient acquisition while parasitising the intestine of yellow mealworm larvae, and reveals the unusual dynamics of cellular interactions between the host epithelium and parasite feeding stages. Trophozoites of G. cuneata develop epicellularly, attached to the luminal side of the host epithelial cell by an epimerite exhibiting a high degree of morphological variability. The presence of contractile elements in the apical region of feeding stages indicates that trophozoite detachment from host tissue is an active process self-regulated by the parasite. A detailed discussion is provided on the possibility of reversible retraction and protraction of the eugregarine apical end, facilitating eventual reattachment to another host cell in better physiological conditions. The gamonts, found in contact with host tissue via a modified protomerite top, indicate further adaptation of parasite for nutrient acquisition via epicellular parasitism while keeping their host healthy. The presence of eugregarines in mealworm larvae even seems to increase the host growth rate and to reduce the death rate despite often heavy parasitisation.

Conclusions/Significance

Improved knowledge about the formation of host-parasite interactions in deep-branching apicomplexans, including gregarines, would offer significant insights into the fascinating biology and evolutionary strategy of Apicomplexa. Gregarines exhibit an enormous diversity in cell architecture and dimensions, depending on their parasitic strategy and the surrounding environment. They seem to be a perfect example of a coevolution between a group of parasites and their hosts.     

Some remarks on parasitic infections of the invasive Neogobius spp. (Pisces) in the Hungarian reaches of the Danube River, with a description of Goussia szekelyi sp. n. (Apicomplexa: Eimeriidae)

During a survey of the parasite fauna Neogobius spp., which only recently invaded Hungarian reaches of the Danube River upstream from Budapest, it was found that Neogobius melanostomus and N. fluviatilis had become common species. Neogobius kessleri was less frequent and the previously widespread Proterorhinus marmoratus was drastically reduced. The parasite fauna of the newcomer fish species was characterized by ubiquitous parasites of a wide host range, such as the trematode Nicolla skrjabini, the metacercariae of Metagonimus yokogawai and Apatemon cobitidis, the larval stages of the acanthocephalan Pomphorhynchus laevis and the nematode Rhaphidascaris acus, the glochidia of an Anodonta sp. (Mollusca) and the ciliophoran Ichthyophthirius multifiliis. The specific parasites of Neogobius spp. were represented by three intestinal coccidia: Eimeria daviesae, Goussia kessleri, and a new species described here as Goussia szekelyi sp. n. This survey showed that the rapid invasion of Ponto‐Caspian gobies in the northern Danube caused important changes in the fish fauna composition of the Danube River and enriched the parasite fauna of Hungarian fishes.     

Biology of Microplitis kewleyi (Hymenoptera: Braconidae): A parasite of Agrotis ipsilon (Lepidoptera: Noctuidae) larvae

Microplitis kewleyi Muesebeck is a gregarious internal parasite of larvae of the black cutworm Agrotis ipsilon (Hufnagel). Studies of the biology of the parasite revealed that there was an inverse relationship between host instar and parasite preference. Duration of development from egg to pupa ranged from 18 days at 27°C to 68.7 days at 16°C. Development from egg to pupa took 13.5–21.6 days when fourth and first instar host larvae, respectively, were parasitized. A larger number of parasites emerged from hosts parasitized in the fourth instar (22.4) than the first instar (11.5). Parasite pupation occurred when the host was in the fifth/sixth instar, depending on the instar parasitized. Thirty‐nine per cent of host larvae exposed as first instars to parasites died before parasite emergence. This decreased to 0% for host larvae exposed as fourth instars. The sex ratio was 1:1.2 (M:F). Thirty‐seven per cent of hosts exposed diurnally were stung, compared to 24% exposed nocturnally. Mean daily progeny was highest (12) on the first day, decreasing to zero after 20 days. Percent host parasitism was also highest on the first day (35%) decreasing to nearly 0% after 18 days. There appear to be three parasite larval instars. Host larvae often remained alive after parasite emergence.     

DEVELOPMENT OF JANCZEWSKIA MORIMOTOI (CERAMIALES) ON ITS HOST LAURENCIA NIPPONICA (CERAMIALES,RHODOPHYCEAE)1

Janczewskia morimotoi Tokida was successfully cultured from spore to reproductive maturity on its host Laurencia nipponica Yamada. The spore penetrates the host without requirement for wound or abrasion sites, growing between host cortical cells and developing a superficial and an endophytic system simultaneously. During the juvenile period, when the parasite is nonpigmented, it differentiates a cortex and the proliferating endophytic filaments enlarge causing a displacement of layers of host cells into the parasitic tissue. Host cells contacted by cells of the parasite exhibit increased wall thickness, cytoplasmic density and vesicle formation. Pit connections between host and parasite cells were rarely observed whereas penetration of host cell walls was seen commonly. As the parasite increases in size, its cells become pigmented evenly throughout the cortex and host cells show less obvious reactions to the parasite. At this same time, the parasite develops branches and reproductive structures. Host plant segments less than 3 cm long failed to grow when infected with spores of the parasite whereas longer segments were not significantly affected by the parasite. In the absence of the host, the parasite cannot complete its development. Although J. morimotoi is well pigmented at maturity, the absence of pigmentation in the juvenile stage, penetration of host cells, and effect on host growth in culture strongly suggest that it is parasitic during at least its early development.     

Composite bundles,the host/parasite interface in the holoparasitic angiosperms Langsdorffia and Balanophora (Balanophoraceae)

Composite bundles are not simply a type of vascular bundles, but an integrated host/parasite interface. We investigated their structure in tubers of Langsdorffia and Balanophora. Composite bundles in both genera have similar components: 1) a central mass of host vascular tissues among which are located large parasite transfer cells; 2) a sheath of parasite parenchyma surrounding the central host vascular tissues; 3) specialized conducting tissues in the sheath; and 4) apical meristems composed of both host and parasite meristematic cells. Sheath parenchyma is recognizable from parasite tuber matrix by having thinner cell walls, and, especially in Langsdorffia, by the presence of collapsed matrix cells between the bundle sheath and tuber matrix. Sheath-conducting tissues consist of densely cytoplasmic transfer cells and small sieve tube members; in Langsdorffia, tracheary elements are also present. These sheath bundles connect with vascular bundles of the tuber matrix. Direct host/parasite contact only occurs by means of parasite transfer cells in the composite bundles. There is no xylem-xylem contact at the host/parasite interface. Abundance of parasite transfer cells suggests that they play an important role in nutrient absorption and translocation.     

Parasitism ofAphis gossypii (Homoptera: Aphididae) byAllothrombium pulvinum larvae (Acari: Trombidiidae) in cotton fields: spatial dispersion and density dependence

Spatial aspects of the interaction between the aphid host,Aphis gossypii, and its parasite,Allo-thrombium pulvinum larvae, on cotton plants were examined in seven fields in China. For both the host and the parasite, sample variance increased with the mean according to Taylor's power law, which explained a substantial proportion (84–97%) of the variation in the data. Although both the host and parasite showed aggregated distribution on cotton plants, the host aphids aggregated more strongly than the parasites. The host dispersion pattern was not significantly affected by the presence of parasites. Increasing the spatial scales of observation from individual plot to the entire field also had no significant effects on host and parasite dispersion patterns. Parasites aggregated in cotton plants with higher aphid densities in five out of the seventeen samples. Spatial patterns of parasitism were mostly host density-independent (71% of the samples) and sometimes inversely density-dependent (29% of the sample). The processes underlying these patterns were discussed.     

Modulation of immune responses of Rhynchophorus ferrugineus (Insecta: Coleoptera) induced by the entomopathogenic nematode Steinernema carpocapsae (Nematoda: Rhabditida)

Aim of this study was to investigate relationships between the red palm weevil (RPW) Rhynchophorus ferrugineus (Olivier) and the entomopathogenic nematode Steinernema carpocapsae (EPN); particularly, the work was focused on the immune response of the insect host in naive larvae and after infection with the EPN. Two main immunological processes have been addressed: the activity and modulation of host prophenoloxidase‐phenoloxidase (proPO) system, involved in melanization of not‐self and hemocytes recognition processes responsible for not‐self encapsulation. Moreover, immune depressive and immune evasive strategies of the parasite have been investigated. Our results suggest that RPW possess an efficient immune system, however in the early phase of infection, S. carpocapsae induces a strong inhibition of the host proPO system. In addition, host cell‐mediated mechanisms of encapsulation, are completely avoided by the parasite, the elusive strategies of S. carpocapsae seem to be related to the structure of its body‐surface, since induced alterations of the parasite cuticle resulted in the loss of its mimetic properties. S. carpocapsae before the release of its symbiotic bacteria, depress and elude RPW immune defenses, with the aim to arrange a favorable environment for its bacteria responsible of the septicemic death of the insect target.     

Sarcocystis rommeli,n. sp. (Apicomplexa: Sarcocystidae) from Cattle (Bos taurus) and its Differentiation from Sarcocystis hominis

Cattle (Bos taurus) are intermediate hosts for three named species of Sarcocystis, S. cruzi, S. hirsuta, and S. hominis. Recently, a fourth species was identified and named S. sinensis. However, S. sinensis originally named a species of Sarcocystis in water buffalo (Bubalus bubalis) in China. Based on unverifiable evidence, it was suggested that the same parasite infects cattle. In addition, S. sinensis was recently declared as nomen nudum because its naming violated the rules of International Code of Zoological Nomenclature. Thus, the fourth species using cattle as an intermediate host does not have a valid name. Here, we propose a new name, Sarcocystis rommeli for the S. sinensis‐like parasite from cattle in Argentina, and differentiate it ultrastructurally from S. hominis sarcocysts from experimentally infected cattle. Sarcocystis rommeli sarcocysts were microscopic with a 5‐μm‐thick wall with slender villar protrusions (Vp); the Vp were up to 5 μm long, up to 0.5 μm wide, and of uneven thickness, often bent at an angle. The ground substance layer (Gs) was up to 0.8 μm thick and smooth. Vesicular structures were seen at the base of the Vp. The bradyzoites were 10–12 μm long. Sarcocystis hominis sarcocysts had Vp that were often upright, up to 7.5 μm long, and up to 1.8 μm wide; the Gs was up to 2 μm thick and without vesicles. Its sarcocyst wall was up to 5.6 μm thick, the vp were bent at an angle, up to 5.8 μm long, the Gs was up to 2 μm thick, but without vesicles seen in S. rommeli. Beef containing sarcocysts of S. rommeli was not orally infectious for two human volunteers and a red fox (Vulpes vulpes). The Sarcocystis described here is molecularly different from S. cruzi, S. hirsuta, and S. hominis based on 18S rRNA and cox1 gene sequences.     

The degree of parasitism of the bumblebee (Bombus terrestris) by cuckoo bumblebees (Bombus (Psithyrus) vestalis)

Host–parasite systems are characterised by coevolutionary arms races between host and parasite. Parasites are often the driving force, as they replicate much faster than their hosts and have shorter generation times and larger population sizes, resulting in higher mutation rates per time interval. This scenario does not fit all host–parasite systems. Socially parasitic cuckoo bumblebees (Bombus (Psithyrus) vestalis) parasitise colonies of Bombus terrestris share most life history characteristics with their hosts. As they parasitise only a subset of all available colonies, their population size should be lower than that of their hosts. This might have strong negative effects on the genetic diversity of B. vestalis and their adaptability. Here, we study for the first time the population structure of a Bombus/Bombus (Psithyrus) system. Highly polymorphic DNA markers were used to reconstruct sibships from individuals collected in the wild. The analysis of the host and parasite populations revealed a rate of parasitism of about 42% (range 33–50%). The population size of B. vestalis was lower compared to their hosts, which was also reflected in low within-group genetic distance. An analysis of the reconstructed queen genotypes revealed more supersisters amongst the B. vestalis queens when compared to the B. terrestris host. The data suggest that B. vestalis females and males do not disperse over long distances. This shows a potential for local adaptation to their hosts.     

Overdispersion of Allothrombium pulvinum larvae (Acari: Trombidiidae) parasitic on Aphis gossypii (Homoptera: Aphididae) in cotton fields

Abstract.

• 1 Dispersion patterns of the protelean parasite, Allothrombium pulvinum Ewing, among individuals of an aphid host, Aphis gossypii Glover, were examined during spring 1991 in several cotton fields in Jiangsu Province, China.
• 2 The variance-to-mean ratios (i.e. dispersion index) of larval mites per host were greater than 1, indicating that the mite parasites were overdispersed among aphid hosts. The variance increased with the mean according to the power law, variance = 1.51 mean¹⁰⁶, which explained 99.7% of the variation in the data.
• 3 The negative binomial distribution adequately describes the patterns of larval mite dispersion among aphid hosts in eight out of ten populations. The degree of clumping (1/k) decreased curvilinearly with parasite density (mites per host).
• 4 Mites were more clumped among adult aphids than among immature ones.
• 5 Ecological and evolutionary consequences of mite overdispersion within host populations are discussed. The role of Allothrombium in pest control is also discussed.

     

Influence of the Parasite Pilostyles ingae (Rafflesiaceae) on some Physiological Parameters of the Host Plant,Mimosa naguirei (Mimosaceae)*

plants found at this site were densely covered by flowers of the parasite on their stems indicating heavy development of cellular The holoparasite/host interaction of Pilostyles ingae (Karst.) Hook. f. (Rafflesiaceae) and Mimosa naguirei Barneby (Mimosaceae) was studied in the open campo rupestre vegetation of Serra do Cipó (State of Minas Gerais, Brazil). Infected M. naguirei threads of the parasite in the bark of the hosts. Cellular threads of the parasite are likely to be richer in lipids and hence depleted in ¹³C. This may explain the significantly more negative carbon isotope ratios (δ¹³C values) of the bark of infected host plants observed as compared to other tissues of infected and non-infected host plants. Photosynthetic parameters such as potential quantum yield of photosystem II (F_v/F_m), apparent photosynthetic electron transport rates (ETR) and effective quantum yield of photosystem II (A F/F'_m) in light dependence curves, as well as δ¹³C values of leaves as a relative measure of average intercellular CO₂ partial pressure during photosynthesis over the lifetime of the leaves, which is also related to average stomatal conductance via water use efficiency, were remarkably similar. This suggests a well balanced relation between the Mimosa host and the Pilostyles parasite, in contrast to other hemiparasitic angiosperm parasite/host interactions where the parasite (e.g. Striga) is known to have strong detrimental effects on host photosynthesis.     

Metazoan parasites of African annual killifish (Nothobranchiidae): abundance,diversity, and their environmental correlates

Estimates of biodiversity and its global patterns are affected by parasite richness and specificity. Despite this, parasite communities are largely neglected in biodiversity estimates, especially in the tropics. We studied the parasites of annual killifish of the genus Nothobranchius that inhabit annually desiccating pools across the African savannah and survive the dry period as developmentally arrested embryos. Their discontinuous, non‐overlapping generations make them a unique organism in which to study natural parasite fauna. We investigated the relationship between global (climate and altitude) and local (pool size, vegetation, host density and diversity, and diversity of potential intermediate hosts) environmental factors and the community structure of killifish parasites. We examined metazoan parasites from 21 populations of four host species (Nothobranchius orthonotus, N. furzeri, N. kadleci, and N. pienaari) across a gradient of aridity in Mozambique. Seventeen parasite taxa were recorded, with trematode larval stages (metacercariae) being the most abundant taxa. The parasites recorded were both allogenic (life cycle includes non‐aquatic host; predominantly trematodes) and autogenic (cycling only in aquatic hosts; nematodes). The parasite abundance was highest in climatic regions with intermediate aridity, while parasite diversity was associated with local environmental characteristics and positively correlated with fish species diversity and the amount of aquatic vegetation. Our results suggest that parasite communities of sympatric Nothobranchius species are similar and dominated by the larval stages of generalist parasites. Therefore, Nothobranchius serve as important intermediate or paratenic hosts of parasites, with piscivorous birds and predatory fish being their most likely definitive hosts.     

Cophylogenetic analysis of lice in the Colpocephalum complex (Phthiraptera: Amblycera)

The chewing louse genus Colpocephalum parasitizes nearly a dozen distantly related orders of birds. Such a broad host distribution is relatively unusual in lice. However, the monophyly of the genus Colpocephalum has never been tested using molecular characters. Using one nuclear and one mitochondrial gene, we inferred a phylogeny for 54 lice from the genus Colpocephalum and other morphologically similar genera. The resulting phylogeny demonstrates that Colpocephalum itself is not monophyletic. However, these data support the existence of a Colpocephalum complex within which several lineages are restricted to particular host orders. These lineages corresponded to previously described genera, some of which are morphologically distinct and currently considered subgenera. Maddison–Slatkin tests were performed on the resulting phylogeny and showed that host order, host family and biogeographic region had significant phylogenetic signal when mapped onto the Colpocephalum complex phylogeny. A PARAFIT analysis comparing the overall Colpocephalum complex phylogeny to a host phylogeny revealed significant congruence between host and parasite trees. We also compared the cophylogenetic history of Colpocephalum and their hosts to that of a second distantly related feather louse genus, Degeeriella, which also infests diurnal birds of prey. Using PARAFIT to identify individual host–parasite links that contributed to overall congruence, there was no evidence of correlated cophylogenetic patterns between these two louse groups, suggesting that their host distribution patterns have been shaped by different evolutionary processes.     

Syntopic occurrence of new species ofPolystoma andMetapolystoma (Monogenea: Polystomatidae) inPtychadena porosissima in South Africa

Polystoma sodwanensis n. sp. andMetapolystoma porosissimae n. sp. are described as new species of the Polystomatidae parasitic in the urinary bladder of adultPtychadena porosissima collected in northern Natal, South Africa. Of 26 frogs examined, 11 host individuals were infected with one of the two parasite species, while in five both parasite species occurred. This is the first record of two different genera of polystomatids occurring together in one host species and the first record ofMetapolystoma in South Africa. The exceptional nature of the reported double infection is discussed in terms of host specificity within the Polystomatidae. Relevant information is given on the ecology and distribution of the host,Ptychadena porosissima.To whom correspondence should be addressed.