Evolutionary complication of life cycles in Coccidea (Sporozoa: Coccidea)

Similar strategies to preserve a species were evolved independently in different groups of Coccidea. Polyenergid oocysts and tissue cysts are found in representatives of the orders Protococcidiida and Eimeriida. Hypnozoits are found in Karyolysus lacerate and Plasmodium vivax; transovarial transmission of parasites occurs in life cycles of Coccidea of the genera Karyolysis and Babesia. Formation of heteroxenity in groups of Coccidea apparently was developed by different ways and in different periods. In some groups (Cystoisospora, Toxoplasma, Aggregata, Atoxoplasma, Schelackia, Lankesterella, and Calyptospora), recent definitive hosts were initial hosts; in other groups (Sarcocystis, Karyolysus, Haemogregarina, Hepatozoon, Plasmodium, Haemoproteus, Leucytozoon, Babesiosoma, Theileria, and Babesia), intermediate hosts were initial hosts.     

Seasonal and Scale Size Relationships between Citricola Scale (Homoptera: Coccidae) and Its Parasitoid Complex (Hymenoptera: Chalcidoidea) on San Joaquin Valley Citrus

The phenology of citricola scale, Coccus pseudomagnoliarum (Kuwana), and its associated parasitoid complex were studied on citrus in the San Joaquin Valley of central California over the period April 1995–March 1997. A total of 10,237 parasitoid specimens of 10 species were collected. Two of these species, Marietta mexicana (Howard) and Encyrtus lecaniorum (Mayr), each recovered from individually isolated scales, represent new parasitoid records for citricola scale. A third species, Encarsia citrinus citrinus (Craw), may represent a new parasitoid record, but this requires further confirmation because a single (male) specimen was recovered from individually isolated scales. The three most dominant parasitoid species, Coccophagus lycimnia (Walker), Metaphycus helvolus (Compere), and Metaphycus luteolus (Timberlake), accounted for the majority (>97%) of the specimens recovered. In contrast to the situation on citrus in southern California, where citricola scale is under effective biological control and is very rarely seen, citricola scale on citrus in the San Joaquin Valley is reemerging as a major pest, especially in groves employing integrated pest management with minimal use of broad-spectrum insecticides. Possible reasons uncovered in this study for the lack of effective biological control of citricola scale in the San Joaquin Valley include: (i) reduced presence of Metaphycus spp. because of hyperparasitism by the heteronomous hyperparasitoid C. lycimnia; (ii) absence of alternate hosts for those species of Metaphycus present; and (iii) absence of hosts of suitable size for Metaphycus at critical times of the year. Recommendations for improving the level of biological control in the San Joaquin Valley are discussed.     

Aggregata dobelli N. Sp. and Aggregata millerorum N. Sp. (Apicomplexa: Aggregatidae) from Two Species of Octopus (Mollusca: Octopodidae) from the Eastern North Pacific Ocean

ABSTRACT. Gamogony and sporogony of two new species of Aggregata (Apicomplexa: Aggregatidae) commonly were observed during histopathological examination of the digestive tracts of octopuses from the National Aquarium in Baltimore. North Pacific giant octopus, Octopus dofleini martini Pickford 1964, from British Columbia and Washington state were infected with Aggregata dobelli n. sp. Sporocysts were smooth-surfaced, dark-staining, subspherical to subovoid, typically 18–31 μ m long by 15–27 μ m wide, and contained 9–22 sporozoites, 18–23 μ m long. California two-spotted octopus, Octopus bimaculoides Pickford and McConnaughey 1949, from California were infected with Aggregata millerorum n. sp. Sporocysts were smooth-surfaced, dark-staining, and subspherical to subovoid, 12–20 μ m long by 11–17 μ m wide, and contained 8–10 sporozoites, 18–31 μ m long. Both species infected the noncuticularized spiral caecum and intestine; A. millerorum n. sp. also infected the cuticularized esophagus and crop. Both parasites were present in the submucosa, muscularis, and serosa. Our observations of Aggregata infections in cuticularized regions of the gut and in the muscularis and serosa appear to be novel. Associated pathologic features included hypertrophy of invaded cells, edema, inflammation, and ulceration.     

Species-specific prevalence of mermithid parasites in populations of six congeneric host caddisflies of Ecnomus McLachlan, 1864 (Trichoptera: Ecnomidae)

Mermithid nematodes are entomophagous parasites and, despite being present in diverse aquatic insects, studies of caddisflies acting as definitive hosts are few and the ecological impacts on host populations are largely unknown. During a four-year study in a stream in southeastern Australia, parasitic mermithid worms were commonly found inside adult caddisflies, but only species of the genus Ecnomus McLachlan, 1864 (Ecnomidae). Ecnomus were the definitive host and parasite prevalence ranged from <1% to nearly 50% across six species. Species-specific prevalence varied little between years and was typically higher in males than in females. Parasite intensity ranged from 1 to 6 (median = 1), but did not vary between species or sexes. Infected hosts could fly, but were castrated and died when worms emerged. High prevalence and virulence (reproductive failure and death of the host) suggests that these parasites could potentially play a role in the population dynamics of some Ecnomus spp.     

Hidden diversity and evolutionary trends in malacosporean parasites (Cnidaria: Myxozoa) identified using molecular phylogenetics

Malacosporeans represent a small fraction of myxozoan biodiversity with only two genera and three species described. They cycle between bryozoans and freshwater fish. In this study, we (i) microscopically examine and screen different freshwater/marine fish species from various geographic locations and habitats for the presence of malacosporeans using PCR; (ii) study the morphology, prevalence, host species/habitat preference and distribution of malacosporeans; (iii) perform small subunit/large subunit rDNA and Elongation factor 2 based phylogenetic analyses of newly gathered data, together with all available malacosporean data in GenBank; and (iv) investigate the evolutionary trends of malacosporeans by mapping the morphology of bryozoan-related stages, host species, habitat and geographic data on the small subunit rDNA-based phylogenetic tree. We reveal a high prevalence and diversity of malacosporeans in several fish hosts in European freshwater habitats by adding five new species of Buddenbrockia and Tetracapsuloides from cyprinid and perciform fishes. Comprehensive phylogenetic analyses revealed that, apart from Buddenbrockia and Tetracapsuloides clades, a novel malacosporean lineage (likely a new genus) exists. The fish host species spectrum was extended for Buddenbrockia plumatellae and Buddenbrockia sp. 2. Co-infections of up to three malacosporean species were found in individual fish. The significant increase in malacosporean species richness revealed in the present study points to a hidden biodiversity in this parasite group. This is most probably due to the cryptic nature of malacosporean sporogonic and presporogonic stages and mostly asymptomatic infections in the fish hosts. The potential existence of malacosporean life cycles in the marine environment as well as the evolution of worm- and sac-like morphology is discussed. This study improves the understanding of the biodiversity, prevalence, distribution, habitat and host preference of malacosporeans and unveils their evolutionary trends.     

Phyllodistomum folium (Trematoda: Gorgoderidae) infecting zebra mussels (Dreissena polymorpha) in the Ebro River, Spain

Zebra mussels (Dreissena polymorpha) were first found in the Ebro River (Spain) in Ribaroja reservoir, in the summer of 2001. This paper reports a study to detect parasites in this bivalve species. From September 2003 to August 2004, a total of 1380 zebra mussels were collected and dissected or sectioned in paraffin and haematoxylin and eosin staining. We observed the presence of Phyllodistomum folium (Olfers, 1816) in two hosts (prevalence 0.14%). Sporocysts containing metacercariae were located within the gill lamellae. One of the mussels was collected in January and the other one in July. In both cases the shell length was >2 cm. P. folium had not been previously reported in Spain and D. polymorpha is its only known intermediate host. It represents a new invasive species in this river basin, presumably introduced together with the zebra mussels.     

Aggregata andresi n. sp. (Apicomplexa: Aggregatidae) from the ommastrephid squid Martialia hyadesi in the SW Atlantic Ocean and some general remarks on Aggregata spp. in cephalopod hosts

A new species of coccidian, Aggregata andresi, is described from the digestive tract of the flying squid Martialia hyadesi, an ommastrephid squid that lives in cold subantarctic waters in the Southwest Atlantic. Gamogonic and sporogonic stages were observed in the digestive tract of 96.5% studied hosts. Oöcysts were ovoid to subspheroid in shape, 170–590 µm in length and 200–530 µm in width. Each oöcyst contained approximately 45,000 sporocysts. Sporocysts measured 9.5–10 µm in length and 8–8.5 µm in width. The surface of the sporocyst wall was smooth and the cyst wall thick. Each sporocyst contained three sporozoites measuring 16–20 µm in length and 2–2.5 µm width. A. andresi is the second species of Aggregata to be reported from a nerito-oceanic cephalopod host.     

Aggregata polibraxiona n. sp. (Apicomplexa: Aggregatidae) from Octopus bimaculatus Verrill, 1883 (Mollusca: Cephalopoda) from the Gulf of California,Mexico

The Apicomplexa Aggregata spp. are intracellular parasites of cephalopods that infect the intestinal tract of commercially important species such as Octopus bimaculatus, which sustains the octopus fishery in Baja California (B.C.), Mexico. In this study, Aggregata polibraxiona n. sp. was described from the cecum of O. bimaculatus collected from Bahia de Los Angeles, B. C. Light and electron microscopy revealed that oocysts and sporocysts were spherical to ovoid in shape. Sporulated oocysts (293–835 × 177–688 μm) contained 135–674 sporocysts (12–24 × 11–22 μm). The sporocyst wall was covered by tubular projections (0.55–2.19 μm in length) bifurcated in the top, unevenly distributed, covered by a thin membrane. Each sporocyst contains 11–13 sporozoites (16–26 × 1.20–3 μm). Three partial sequences of the 18S rDNA gene were obtained, and two phylogenetic approaches were performed according to Bayesian inference and Maximum Likelihood. In both phylogenetic reconstructions, the sequences of A. polibraxiona n. sp. were recovered as a monophyletic group within the genus Aggregata and placed as a sister group to Aggregata octopiana Lineage II. Aggregata polibraxiona n. sp. is the first Apicomplexa described from a cephalopod host from Mexico and extends the geographical range of Apicomplexa infecting cephalopods.     

Parasitism of Hylodes phyllodes (Anura: Cycloramphidae) by Hannemania sp (Acari: Trombicuudae) in an area of Atlantic Forest, Ilha Grande, southeastern Brazil

We studied some parameters of the parasitism by the mite Hannemonia sp. on the endemic frog Hylodes phyllodes in the Atlantic Forest of Ilha Grande (Rio de Janeiro State, Brazil). Prevalence, mean abundance, mean intensity and total intensity of infestation, body regions infected, and host sexual differences in parasitism rate of the larvae of Hannemania sp. on individuals of H. phyllodes were assessed. Prevalence was 86.5% (N = 37; total of 1,745 larvae of Hannemania sp) for male hosts and 91.7% (N = 12; total of 330 larvae) for female hosts, with no significant difference between the sexes. Overall prevalence of Hannemania sp. on H. phyllodes was 87.7%. Mean intensity of infestation in males (54.5 +/- 42.5; range 1-173 larvae) was higher than in females (29.9 +/- 47.6; range 1-166). We conclude that the rates of intensity, abundance, and prevalence of Hannemania larvae parasitizing Hylodes phyllodes at Ilha Grande were considerably high, suggesting that this species of anuran constitutes a relevant host for this mite species to complete its life-cycle in the area. Differences between males and females in infestation rates probably reflect their differential use of space in the forest.     

Prevalence and host-parasite list of some nasal mites from birds (Acarina: Rhinonyssidae, Speleognathidae)

A survey of nasal mites, primarily from birds in Texas, was reported and comparisons with the other major studies were made. Of 103 host species examined, 40 were parasitized, and of 502 individual birds examined, 87 were parasitized (17% prevalence). It was shown that the prevalence of infection was significantly dependent on the bird taxa examined, which indicates that the evolution of the hosts has affected the nasal mites' ability to parasitize their avian hosts. It was also shown that the prevalence of rhinonyssid nasal mites in their hosts seems to differ significantly between geographic regions.     

The role of Cytograpsus angulatus (Crustacea; Brachyura) in the life cycles of Microphallus szidati (Digenea; Microphallidae) and Falsifilicollis chasmagnathi (Acanthocephala; Filicollidae): various aspects of their ecological parasitology

Based on a study of the larvae from two helminth species parasitizing the crab Cyrtograpsus angulatus Dana, 1851 (Microphallus szidati Martorelli, 1986 and Falsifilicollis chasmagnathi Holcman-Spector et al., 1977), from Mar chiquita lagoom (Argentina) together with the analyses of their life cycles and rates of prevalence, intensity and association coefficient (compared in definitive and intermediate host) the following conclusions have been reached: a) C. angulatus suns to be an excellent intermediate host in the life-cycles of the studied helminths; b) the size of the crabs and the occurrence of natural amputations in the females (Spivak & Politis, in press) appeared correlated with prevalence; c) in the studied crabs the prevalence for F. chasmagnathi is higher in males than in females; d) the intensity did not appear correlated with size and sex of the intermediate host; e) M. szidati and F. chasmagnathi are closely associated with the intermediate host; f) C. angulatus and Himantopus melanurus Vieillot, 1817 (Aves; Recurvirostridae) are reported as new intermediate and definitive hosts, respectively, for F. chasmagnathi; g) Chasmagnathus granulata Dana, 1851 (Crustacea; Brachyura) is reported as a new intermediate host for M. szidati.     

Chewing Lice of Swan Geese (Anser cygnoides): New Host-Parasite Associations

Chewing lice (Phthiraptera) that parasitize the globally threatened swan goose Anser cygnoides have been long recognized since the early 19th century, but those records were probably biased towards sampling of captive or domestic geese due to the small population size and limited distribution of its wild hosts. To better understand the lice species parasitizing swan geese that are endemic to East Asia, we collected chewing lice from 14 wild geese caught at 3 lakes in northeastern Mongolia. The lice were morphologically identified as 16 Trinoton anserinum (Fabricius, 1805), 11 Ornithobius domesticus Arnold, 2005, and 1 Anaticola anseris (Linnaeus, 1758). These species are known from other geese and swans, but all of them were new to the swan goose. This result also indicates no overlap in lice species between older records and our findings from wild birds. Thus, ectoparasites collected from domestic or captive animals may provide biased information on the occurrence, prevalence, host selection, and host-ectoparasite interactions from those on wild hosts.     

Physiological and ecological hosts of Popenaias popeii (Bivalvia: Unionidae): laboratory studies identify more hosts than field studies

1. Freshwater mussels are critically endangered in North America, making it important to understand their environmental requirements at all life stages. As glochidia (larvae), they attach to fish hosts where they undergo substantial mortality, making this transition important in their life cycle. Larval host fish requirements have typically been described using data from laboratory infestations to determine suitable hosts. 2. Laboratory infestations circumvent many natural barriers that prevent infestation of physiologically compatible fishes by mussel larvae. While such methods are invaluable for identifying ‘physiological hosts,’ they cannot fully describe realised ‘ecological hosts’ in the field. 3. We studied Popenaias popeii in the Black River in New Mexico, because it is of conservation concern and it is the only mussel species present, facilitating identification of glochidial infestation. To explore the difference between physiological hosts and ecological hosts, we conducted a 3‐year field study of fishes infested by P. popeii glochidia. 4. Substantially fewer fish species were infested by P. popeii in the wild (10 of 20 observed) than had been identified as physiological hosts in laboratory trials (24 of 31). We combined data on fish abundance, proportion of fish hosts infested (prevalence) and the number of glochidia per fish (intensity) and identified three fish species that probably contributed substantially more to mussel recruitment by carrying more glochidia than other host species. 5. Similarities in behaviour among these fishes allowed us to hypothesise routes of infestation, such as benthos‐feeding by catostomids, that allow glochidia to infest these hosts at higher rates than other suitable hosts. Overall, this approach provides a method of quantifying the relative importance of different species of host fish in the mussel lifecycle.     

The Evolution of Resistance to Simian Immunodeficiency Virus (SIV): A Review

Examining how pathogens cross species boundaries, spread within species, and persist within their hosts is an essential part of understanding the factors that underpin the evolution of virulence and host resistance. Here, we review current knowledge about the genetic diversity, molecular epidemiology, prevalence, and pathogenicity of simian immunodeficiency viruses (SIVs). SIVs have crossed species boundaries from simian hosts to humans on at least 12 separate occasions, one of which led to the global HIV–AIDS crisis. Though SIVs infect a wide range of primates, scientists have only recently begun to describe the natural history of SIV infection in their natural hosts. Several new studies reveal how both viral and host factors are responsible for the transmission to, and adaptation in, new hosts. These studies also suggest that the spread of the virus may be affected by host-specific traits, including social structure, mating system and demographic history. These studies challenge the traditional view that SIV is relatively benign in its natural host, and instead suggest that a highly dynamic relationship exists between SIV and its simian hosts.     

Host specificity among Unionicola spp. (Acari: Unionicolidae) parasitizing freshwater mussels

Water mites of Unionicola spp. are common parasites of freshwater mussels as adults, living on the gills, or mantle and foot of their hosts and using these tissues as sites of oviposition. The present study addresses specialization among North American Unionicola mussel-mites using 2 measures of host specificity: (1) the number of host species used by a species of mite; and (2) a measure that considers the taxonomic distinctness of the hosts utilized by mites, weighted for their prevalence in the different hosts. Results of this study indicate the Unionicola spp. mussel-mites are highly host specific, with most species occurring in association with 1 or 2 species of hosts. If 2 or more host species are utilized, they are typically members of the same genus. These data are consistent with studies examining the dispersal abilities and host recognition behavior for members of the group. When the average values of host specificity for Unionicola subgenera were mapped on a phylogenetic tree for these taxa, a clade comprised of gill mites appeared to be more host specific than a clade consisting of mantle mites. There were, however, no apparent patterns of host specificity within each of the clades. Differences in specificity between the 2 lineages may reflect either a long evolutionary history that gill mites have had with host mussels or the intense competition among gill mites for oviposition sites within unionid mussels, leading to increased host specialization.     

Host specificity and local infection dynamics of Kudoa leptacanthae n. sp. (Multivalvulida: Kudoidae) from the pericardial cavity of two Zoramia spp. (Perciformes: Apogonidae) at Lizard Island lagoon, Queensland, Australia

Kudoa leptacanthae n. sp. was identified within the pericardial cavities of two apogonid species, Zoramia leptacantha and Zoramia viridiventer, from waters off Lizard Island on the Great Barrier Reef. The species shows a close taxonomic affinity, both morphologically and genetically, to Kudoa shiomitsui Egusa & Shiomitsu 1983 reported from a tetraodontid and scombrid, both from Japan. The infection was at high prevalences (average=75.8%±0.63, n=343) within schools of the two host species. Different sporogonic stages ('developing' and 'fully-developed') were observed in pseudocysts within the pericardium of the hosts. Kudoa leptacanthae n. sp. appears to be a persistent infection within the Zoramia species hosts. No seasonal variation was detected for this host/parasite system and the parasite did not affect host condition, when assessed using host length/weight ratio as a coarse indicator. We hypothesise that a source of infection in close proximity to the home patch reef of apogonid schools may lead to the high prevalence and intensity of infection reported in this study.     

Abundance patterns of two Oropsylla (Ceratophyllidae: Siphonaptera) species on black-tailed prairie dog (Cynomys ludovicianus) hosts.

Behavioral, genetic, and immune variation within a host population may lead to aggregation of parasites whereby a small proportion of hosts harbor a majority of parasites. In situations where two or more parasite species infect the same host population there is the potential for interaction among parasites that could potentially influence patterns of aggregation through either competition or facilitation. We studied the occurrence and abundance patterns of two congeneric flea species on black-tailed prairie dog (Cynomys ludovicianus) hosts to test for interactions among parasite species. We live-trapped prairie dogs on ten sites in Boulder County, CO and collected their fleas. We found a non-random, positive association between the two flea species, Oropsylla hirsuta and O. tuberculata cynomuris; hosts with high loads of one flea species had high loads of the second species. This result suggests that there is no interspecific competition among fleas on prairie dog hosts. Host weight had a weak negative relationship to flea load and host sex did not influence flea load, though there were slight differences in flea prevalence and abundance between male and female C. ludovicianus. While genetic and behavioral variation among hosts may predispose certain individuals to infection, our results indicate apparent facilitation among flea species that may result from immune suppression or other flea-mediated factors.     

Parasite in peril? A new species of mite in the genus Ophiomegistus Banks (Parasitiformes: Paramegistidae) on an endangered host,the pygmy bluetongue lizard Tiliqua adelaidensis (Peters) (Squamata: Scincidae)

Host‐parasite relationships are generally understudied in wild populations but have a potential to influence host population dynamics and the broader ecosystem, which becomes particularly important when the host is endangered. Herein we describe a new species of parasitic mite from the genus Ophiomegistus (Parasitiformes: Mesostigmata: Paramegistidae) of an endangered South Australian skink; the pygmy bluetongue lizard (Tiliqua adelaidensis). Adult mites were observed on lizard hosts in three different host populations, among which prevalence varied. No temporal trend in prevalence was evident over two spring‐summer seasons of monitoring. We hypothesise that the reliance on burrows as refuges by T. adelaidensis may be essential for the completion of the mite life cycle and also for horizontal transmission. The conservation implications of not only its effect on the host, but also its potential status as an endangered species itself, are considered.