First-intermediate Host Research Articles

МАТЕРИАЛЫ К ФАУНЕ МНОГОКЛЕТОЧНЫХ ПАРАЗИТОВ PERCA FLUVIATILIS L. (ACTINOPTERYGII: PERCIFORMES) (САРАТОВСКОЕ ВОДОХРАНИЛИЩЕ)

The fauna of multicellular parasites of Perca fl uviatilis (Peciformes) (2019, 2022) was studied at the site of the Saratov reservoir, located in the zone of infl uence of a large hydroelectric complex – the Zhigulevskaya HPP (a branch of PJSC RusHydro). 8 species of parasitic organisms were found. Infection of fi sh with alien parasites Apophallus muechlingi and Nicolla skrjabini was revealed. The trematode A. muechlingi, a specifi c parasite of Cyprinidae, occupied a dominant position in the perch macroparasite fauna. This process took no more than 19 years since the introduction of the alien mollusk Lithoglyphus naticoides, the fi rst intermediate host of the parasite. The possibility of participation of invasive fi sh in the process of P. fl uviatilis invasion by 5 parasite species is discussed. Species posing a potential danger to fi sh, carnivores and humans have been found. In particular, for the fi rst time for P. fl uviatilis in the Saratov reservoir, the acanthocephalan Pomphorhynchus laevis, the causative agent of fi sh pomphorhynchosis, was recorded.

First elucidation of a didymozoid life cycle: Saccularina magnacetabula n. gen. n. sp. infecting an arcid bivalve

The first first-intermediate host for a species of Didymozoidae (Trematoda: Hemiuroidea), a bivalve of the family Arcidae, is identified using multi-loci molecular data. First intermediate, (likely) third intermediate, and adult stages of a new didymozoid taxon (Saccularina magnacetabula n. gen. n. sp.) from Moreton Bay, Queensland, Australia were collected from the Sydney cockle Anadara trapezia (Deshayes) (Arcoidea: Arcidae), Sillago sp. (Sillaginidae) and Elops hawaiensis Regan (Elopiformes: Elopidae), respectively, and genetically matched. Infections in A. trapezia were present as sporocysts and cystophorous cercariae, and infected tissue at the base of the gills. Morphologically, S. magnacetabula is distinctive relative to all other didymozoids in the combination of hermaphroditism, mate-pairing, filiform body shape, the presence of a ventral sucker, a single testis, and a saccular excretory vesicle at the posterior extremity. Molecular sequence data were generated for S. magnacetabula and 42 other putative didymozoid species to explore relationships within the Didymozoidae and Hemiuroidea. In molecular phylogenetic analyses of the 28S rDNA region, the new genus forms a clade with an undescribed taxon from the redthroat emperor, Lethrinus miniatus (Bloch & Schneider) (Perciformes: Lethrinidae), from the Great Barrier Reef, and another uncharacterised taxon from E. hawaiensis. This clade is sister to a moderately well-supported clade comprising all other didymozoid species for which sequences are available, including representatives of five of the six presently recognised subfamilies. The infection of a bivalve by a didymozoid is discussed in the context of the overwhelming use of gastropod molluscs as first intermediate hosts by the Hemiuroidea.

Spatial scale and structure of complex life cycle trematode parasite communities in streams.

By considering the role of site-level factors and dispersal, metacommunity concepts have advanced our understanding of the processes that structure ecological communities. In dendritic systems, like streams and rivers, these processes may be impacted by network connectivity and unidirectional current. Streams and rivers are central to the dispersal of many pathogens, including parasites with complex, multi-host life cycles. Patterns in parasite distribution and diversity are often driven by host dispersal. We conducted two studies at different spatial scales (within and across stream networks) to investigate the importance of local and regional processes that structure trematode (parasitic flatworms) communities in streams. First, we examined trematode communities in first-intermediate host snails (Elimia proxima) in a survey of Appalachian headwater streams within the Upper New River Basin to assess regional turnover in community structure. We analyzed trematode communities based on both morphotype (visual identification) and haplotype (molecular identification), as cryptic diversity in larval trematodes could mask important community-level variation. Second, we examined communities at multiple sites (headwaters and main stem) within a stream network to assess potential roles of network position and downstream drift. Across stream networks, we found a broad scale spatial pattern in morphotype- and haplotype-defined communities due to regional turnover in the dominant parasite type. This pattern was correlated with elevation, but not with any other environmental factors. Additionally, we found evidence of multiple species within morphotypes, and greater genetic diversity in parasites with hosts limited to in-stream dispersal. Within network parasite prevalence, for at least some parasite taxa, was related to several site-level factors (elevation, snail density and stream depth), and total prevalence decreased from headwaters to main stem. Variation in the distribution and diversity of parasites at the regional scale may reflect differences in the abilities of hosts to disperse across the landscape. Within a stream network, species-environment relationships may counter the effects of downstream dispersal on community structure.

Accidental associates are not symbionts: the absence of a non-parasitic endosymbiotic community inside the common periwinkle Littorina littorea (Mollusca: Gastropoda)

One of the most thoroughly studied marine snails in the world is the North Atlantic periwinkle Littorina littorea. In 2013, Buckland-Nicks et al. reported upon an “extensive community of organisms” living “inside” L. littorea in Nova Scotia, Canada. Conflicting with this report is a vast body of research on this snail since the mid-nineteenth century that has never identified the presence of such a taxonomically diverse endosymbiotic community, with the exception of a well-known assemblage of parasitic digenean trematodes that utilize the snail as a first-intermediate host. The absence of prior reports of a non-parasitic endosymbiotic community, and our own long-term observations, inspired us to study the biological community associated with L. littorea in two locations (Nova Scotia and Connecticut). We were unable to verify the endosymbiotic nature of any of the species (other than trematodes) noted by Buckland-Nicks et al. (Can J Zool 91:293–301, 2013) associated with L. littorea. Instead, we identified three likely sources of associated taxa reported by Buckland-Nicks et al. (Can J Zool 91:293–301, 2013) and by us: species were (1) ingested and defecated alive; (2) attached to the mucous-covered foot and drawn into the mantle cavity when the snail closed its operculum; and/or (3) associated with shell surface cracks and crevices, including within encrusting algae. We could not find any evidence that L. littorea hosts a diverse community of endosymbionts. Instead, we argue that the organisms interpreted as members of an endosymbiotic community by Buckland-Nicks et al. are instead free-living taxa that are transiently associated with the snails.

Investigation on the endemic characteristics of Metorchis orientalisin Huainan area, China

To investigate the endemic characteristics of Metorchis orientalis (M. orientalis)in the Huainan area, Anhui province, China. The first-intermediate host, second-intermediate host and reservoir hosts were collected, and the endemic characteristics of M. orientalis were examined through field investigation and artificial infection. Investigation was completed in 89 domestic ducks, 156 domestic chicken, 41 domestic geese, 20 domestic cats and 19 dogs. The infection rate of M. orientaliswas 18.0% (16/89) in ducks, 12.2% (19/156) in chicken, 9. 8% (4/41) in geese, 5.0% (1/20) in cats and 5.3% (1/19) in dogs. Sixty-seven cercariae of M. orientaliswere identified in 1,000 Parafossarulu s striatulus,with a natural infection rate of 6.7%, and 19 cercariae occurred in 300 Pseudorasbora parva, with a natural infection rate of 6.33%. The activity of the cercariae of M. orientaliswas associated with light intensity and temperature. The full life cycle of M. orientalisranged from 120 to 140 days; it occurred approximately in 89 days in snails, 28 days in fish and 20 days in ducks. M. orientalisis prevalent in the Huainan area, and it may complete its life cycle in Parafossarulus striatulus, Pseudorasbora parva and natively rais ed ducks.

Seasonal and Annual Variation in Trematode Infection of Stream SnailElimia proximain the Southern Appalachian Mountains of Virginia

Understanding temporal variation of host-pathogen dynamics can be important for predicting disease risks and anticipating how disease systems may change in response to natural or human disturbances. Seasonal changes in weather, especially those associated with changes in temperature or precipitation, are often a key component of temporal changes in infection risk and can have important impacts on disease systems. However, these patterns can be difficult to track due to interannual variation and the need for longer term, multi-year surveillance efforts. We assessed seasonal and annual changes in the trematode component community of first-intermediate host stream snail Elimia (= Oxytrema = Goniobasis) proxima across 5 streams in the southern Appalachian Mountains. Over 3 yr, we found no evidence of consistent seasonal peaks of trematode infection in E. proxima. There was some across-site consistency in infection prevalence over 4 yr, because high prevalence sites tended to maintain higher prevalence from year to year, relative to lower prevalence sites. In addition, we examined the relationship between prevalence of first-intermediate host infection, weather variables, and site-level factors, including snail density and water quality metrics. Trematode prevalence was negatively related to total precipitation, which may have been due to the movement of infectious parasite stages and hosts downstream during high flows. We found no strong relationships between trematode prevalence and snail density or any of the water quality metrics examined in this study, indicating that snail infection may be driven primarily by definitive host activity.

Faunal survey and identification key for the trematodes (Platyhelminthes: Digenea) infecting Potamopyrgus antipodarum (Gastropoda: Hydrobiidae) as first intermediate host

A diverse guild of digenean trematodes infects the New Zealand mud snail, Potamopyrgus antipodarum, as firstintermediate host. This manuscript offers an initial systematic treatment of these trematodes and relies on published andnew information. I list 20 trematode species, for which I provide taxonomic affinities, life-cycle information, and anidentification key. A species account section presents photographs, diagnostic information, additional descriptive notes,and information on relevant research concerning the listed species. The major aim of this manuscript is to facilitateresearch on this trematode guild by providing information and identification tools, and by highlighting gaps in our knowledge.