The complete mitochondrial genome of Morishitium polonicum (Trematoda, Cyclocoelidae) and its phylogenetic implications

Trematodes can adversely impact the health and survival of wild animals. The trematode family Cyclocoelidae, which includes large digenean bird parasites, lacks molecular analysis, and reclassifications have not been supported. This study produced the first fully assembled and annotated mitochondrial genome sequence for the trematode Morishitium polonicum. The whole length of the M. polonicum (GenBank accession number: OP930879) mitogenome is 14083 bp, containing 22 transfer ribonucleic acids (tRNAs), 2 ribosomal RNAs (rRNAs, rrnL and rrnS), and a noncoding control section (D-loop) 13777 to 13854 bp in length. The 12 PCG areas have 3269 codons and a total length of 10053 bp, which makes up 71.38% of the mitochondrial genome's overall sequence. Most (10/12) of the PCGs that code for proteins begin with ATG, while the nad4L and nad1 genes have a GTG start codon. Phylogenetic analysis using the concatenated nucleotide sequences of 12 PCGs, and the ML tree analysis results showed that M. polonicum is more closely related to with Echinostomatidae and Fasciolidae, which indicates that the family Cyclocoelidae is more closely associated with Echinochasmidae. This study provides mtDNA information, and analysis of mitogenomic structure and evolution. Moreover, we aimed to understand the phylogenetic relationships of this fluke.

A new species of Echinostoma (Trematoda: Echinostomatidae) from the 'revolutum' group found in Brazil: refuting the occurrence of Echinostoma miyagawai (=E. robustum) in the Americas

Although Echinostoma robustum (currently a synonym of E. miyagawai) was reported in the Americas based on molecular data, morphological support on adult parasites is still required. Herein, a new species of Echinostoma is described based on worms found in a chicken from Brazil. Molecular phylogenetic analyses based on 28S (1063 bp), ITS (947 bp) and Nad-1 (442 bp) datasets reveal the inclusion of the new species within Echinostoma ‘revolutum’ species complex. Moreover, it was verified the conspecificity between cercariae previously identified as E. robustum in Brazil [identical ITS and only 0.3% of divergence (1 nucleotide) in Nad-1]. Species discovery analyses show that these two isolates form an independent lineage (species) among Echinostoma spp. Compared to E. miyagawai, the new species presents relatively high divergence in Nad-1 (7.88–9.09%). Morphologically, the specimens are distinguished from all nominal species from the ‘revolutum’ species complex by the more posterior position of the testes (length of post-testicular field as a proportion of body length about 20%). They further differ from E. miyagawai and South American Echinostoma spp. by the higher proportion of forebody to the body length. Therefore, combined molecular and morphological evidence supports the proposal of the species named here as Echinostoma pseudorobustum sp. nov.

Echinostoma chankensis nom. nov., other Echinostoma spp. and Isthmiophora hortensis in East Asia: morphology, molecular data and phylogeny within Echinostomatidae

Life cycles, and morphological and molecular data were obtained for Echinostoma chankensis nom. nov., Echinostoma cinetorchis, Echinostoma miyagawai and Isthmiophora hortensis from East Asia. It was established that, based on both life cycle and morphology data, one of the trematodes is identical to the worms designated as Euparyphium amurensis. Genetic data showed that this trematode belongs to Echinostoma. The complex data on biological, morphological and genetic characterizations establish that the distribution of the morphologically similar species, I. hortensis and Isthmiophora melis, in the Old World are limited by the East Asian and European regions, respectively. Data on mature worms of East Asian E. miyagawai revealed morphological and genetic identity with E. miyagawai from Europe. However, E. miyagawai from Europe differs from E. miyagawai from the type locality (East Asia) in terms of reaching maturity and the morphology of cercariae. These data indicate that the European worm, designated E. miyagawai, does not belong to this species. An analysis of the phylogenetic relationships of Echinostomatidae was conducted based on the 28S, ITS2 and nad1 markers. Analysis using the nad1 gene for the known representatives of Echinostomatidae is carried out for the first time, showing that nuclear markers are ineffective separate from mitochondrial ones.

Acanthoparyphium shinanense n. sp. (Digenea: Echinostomatidae) from Experimental Chicks Infected with Metacercariae Encysted in Brackish Water Clams in the Republic of Korea

Acanthoparyphium shinanense n. sp. (Digenea: Echinostomatidae) is described from chicks experimentally infected with the metacercariae encysted in 2 brackish water clam species, Ruditapes philippinarum and Coecella chinensis, in the Republic of Korea. The metacercariae were round to oval, armed with 23 collar spines, and 0.216 (0.203-0.226) mm in diameter. From 5 chicks experimentally infected each with 200 metacercariae, 34 juvenile (5-day-old worms) and 104 adult flukes (7-day-old worms) were harvested from their small intestines, with the average worm recovery rate of 13.8%. The adult flukes were 3.18 (2.89-3.55) mm long and 0.68 (0.61-0.85) mm wide, with an elongated, posteriorly tapering body, and a prominent head collar armed with 23 collar spines arranged in a single uninterrupted row. The posterior testis of A. shinanense was longitudinally elongated, which is similar to Acanthoparyphium spinulosum Johnston, 1917 but unique from the other closely related species, including Acanthoparyphium tyosenense Yamaguti, 1939, Acanthoparyphium kurogamo Yamaguti, 1939, and Acanthoparyphium marilae Yamaguti, 1934. The eggs of A. shinanense were larger than those of A. spinulosum, and the anterior extent of 2 lateral groups of vitellaria was slightly more limited in A. shinanense than in A. spinulosum. Molecular analysis of nuclear and mitochondrial genes revealed low homology with A. spinulosum from USA (96.1% in 5.8S rRNA) and Ukraine (97.9% in 28S rRNA), Acanthoparyphium n. sp. from USA (98.0% in 28S rRNA), and Acanthoparyphium sp. from Australia, Kuwait, and New Zealand. Biological characteristics, including its first intermediate host and natural definitive hosts, as well as its zoonotic capability, should be elucidated.

Echinostoma miyagawai Ishii, 1932 (Echinostomatidae) from Ducks in Aceh Province, Indonesia with Special Reference to Its Synonymy with Echinostoma robustum Yamaguti, 1935

Adult echinostomes having 37 collar spines collected from the intestine of Pitalah ducks in Aceh Province, Indonesia in 2018 were morphologically and molecularly determined to be Echinostoma miyagawai Ishii, 1932 (Digenea: Echinostomatidae). Among 20 ducks examined, 7 (35.0%) were found to be infected with this echinostome, and the number of flukes collected was 48 in total with average 6.9 (1-17) worms per duck. The adult flukes were 7.2 (6.1-8.5) mm in length and 1.2 (1.0-1.4) mm in width (pre-ovarian or testicular level) and characterized by having a head collar armed with 37 collar spines (dorsal spines arranged in 2 alternating rows), including 5 end group spines, and variable morphology of the testes, irregularly or deeply lobed (3-5 lobes) at times with horizontal extension. The eggs within the worm uterus were 93 (79-105) µm long and 62 (56-70) µm wide. These morphological features were consistent with both E. miyagawai and Echinostoma robustum, for which synonymy to each other has been raised. Sequencing of 2 mitochondrial genes, cox1 and nad1, revealed high homology with E. miyagawai (98.6-100% for cox1 and 99.0-99.8% for nad1) and also with E. robustum (99.3-99.8% for nad1) deposited in GenBank. We accepted the synonymy between the 2 species and diagnosed our flukes as E. miyagawai (syn. E. robustum) with redescription of its morphology. Further studies are required to determine the biological characteristics of E. miyagawai in Aceh Province, Indonesia, including the intermediate host and larval stage information.

The effect of trematode infection on the markers of oxidative stress in the offspring of the freshwater snail Lymnaea stagnalis

Most invertebrate species exhibit immunological responses that can inactivate and eliminate penetrating parasites. Such immune responses in particular involve the formation of potentially toxic reactive oxygen species (ROS). We explored the immune capabilities of the first-generation (F1) offspring of naturally infected freshwater snails, Lymnaea stagnalis, in response to infection by trematode cercariae under laboratory conditions. The rates of ROS formation and peroxidase activity in the hemolymph of the F1 offspring of L. stagnalis parents infected by an asexual stage of trematodes were significantly higher than in F1 offspring of uninfected parents. Compared to offspring from uninfected parents, the growth rate of F1 snails from infected parents was higher, but survival was lower. After infection of F1 snails by trematode cercariae of Echinoparyphium aconiatum under laboratory conditions, the rate of ROS formation and peroxidase activity in the hemolymph of F1 offspring of uninfected parents increased compared to control snails. This pattern persisted throughout the entire 3-week observation period. In contrast, the rate of ROS formation in the hemolymph of F1 snails from infected parents after experimental infection by E. aconiatum cercariae did not differ from controls, and peroxidase activity even decreased. Thus, trematode parthenitae infection of parents could alter the immune response of their offspring.

First molecular identification and phylogenetic tree of Petasiger exaeretus Dietz, 1909 (Digenea: Echinostomatidae) from an intermediate host Radix auricularia (L., 1758) in Greater Zab river, Iraq

INTRODUCTION

Radix auricularia (Linnaeus, 1758) is a freshwater gastropod belongs to the Lymnaeidae (pond snails) family which act as intermediate hosts or vectors of various parasitic flukes. No study has yet been undertaken on the prevalence of Petasiger spp. infection in R. auricularia. Species of Petasiger (Dietz, 1909) are a cosmopolitan parasite that utilize snails as the first intermediate host, with vertebrates like amphibians larvae and fish as the second intermediate host, followed by fish-eating birds. The current paper is considered to be the first report of Petasiger exaeretus parasitized R. auricularia in Iraq, which is supported with molecular and phylogenetic analysis.

MATERIAL AND METHODS

Freshwater snails R. auricularia were collected during October 2016 - September 2017 from different locations of Sufaia village on the Greater Zab river, Erbil province, Iraq.

RESULTS

A total of 307 freshwater snails R. auricularia were collected, only five of them were infected with a prevalence of Petasiger exaeretus (1.62%).

CONCLUSIONS

The current study agrees with the opinion of Selbach, Soldánová (26), which suggested the possibility of a much higher morphological diversity within Petasiger species, based on the number of described cercariae, compared with adult forms.It is clear that P. phalacrocoracis specimens have often been erroneously designated as P. exaeretus by many authors (Našincová et al., 1994). Certain morphological similarities and dissimilarities between P. exaeretus and P. phalacrocoracis can be detected: the pear-shaped body resembles P. exaeretus, whereas, P. phalacrocoracis have an elongated body.

Molecular characterisation of four echinostomes (Digenea: Echinostomatidae) from birds in New Zealand, with descriptions of Echinostoma novaezealandense n. sp. and Echinoparyphium poulini n. sp

Morphological and molecular characterisation of echinostome specimens (Digenea: Echinostomatidae) recovered in one Anas platyrhynchos L. and one Cygnus atratus (Latham) (Anseriformes: Anatidae) from New Zealand revealed the presence of two known species, Echinostoma miyagawai Ishii, 1932 and Echinoparyphium ellisi (Johnston & Simpson, 1944) and two species new to science. Comparative morphological and phylogenetic analyses supported the distinct species status of Echinostoma novaezealandense n. sp. ex Branta canadensis (L.), A. platyrhynchos and C. atratus, and Echinoparyphium poulini n. sp. ex C. atratus. Echinostoma novaezealandense n. sp., a species of the "revolutum" species complex characterised by the possession of a head collar armed with 37 spines, keyed down to E. revolutum but was distinguished from the latter in having a much narrower body with almost parallel margins, longer oesophagus, wider cirrus-sac, larger seminal vesicle, much smaller ventral sucker, ovary, Mehlis' gland and testes, more anteriorly located ovary and testes, and distinctly smaller eggs (81-87 × 42-53 vs 106-136 × 55-70 µm). This new species appears similar to Echinostoma acuticauda Nicoll, 1914 described in Australia but differs in having a longer forebody, more posteriorly located ovary and testes, and much smaller eggs (81-87 × 42-53 vs 112-126 × 63-75 µm). Echinoparyphium poulini n. sp. is differentiated from the four species of Echinoparyphium possessing 37 collar spines considered valid as follows: from E. chinensis Ku, Li & Chu, 1964 in having a much smaller body, four (vs five) angle spines and simple seminal vesicle (vs bipartite); from E. schulzi Matevosyan, 1951 in having a less robust body at a comparable body length, much smaller ventral sucker, ovary and testes, and longer but narrower eggs (87-109 × 50-59 vs 70-85 × 60-84 µm); and from the two smaller forms, E. serratum Howell, 1968 and E. aconiatum Dietz, 1909, in a number of additional metrical features correlated with body size and especially in the possession of much larger collar spines. Partial fragments of the mitochondrial nad1 and 28S rRNA genes were amplified for representative isolates of the four species and analysed together with sequences for Echinostoma spp. and Echinoparyphium spp. available on GenBank. Phylogenetic analyses based on the mitochondrial nad1 gene revealed congruence between the molecular data and species identification/delineation based on morphology; this was corroborated by the 28S rDNA sequence data.

Malformations of the gill filaments of the ruffe Gymnocephalus cernuus (L.) (Pisces) caused by echinostomatid metacercariae

In parasite surveys of fishes from Lake Balaton and its tributaries in Hungary, infections with metacercariae of a species of the digenean genus Echinochasmus (Trematoda: Echinostomatidae) were found in seven species of fish. In ruffe, Gymnocephalus cernuus, malformations of the gill filaments apparently caused by these infections were observed. These malformations were in the form of bifurcations of the filaments at about their mid-length. At the point where the filaments bifurcate, an Echinochasmus metacercaria was always embedded in the cartilaginous ray of the gill filament. All specimens of the ruffe were found to be infected by these metacercariae, and each ruffe specimen was infected by 30-300 metacercariae. Such a bifurcation was found in all of the ruffe specimens, but, apart from these gill malformations, the metacercariae produced only local changes in the cartilage. In the other six infected fish species, only local signs were observed in the cartilage. Experimental infections of chicks with metacercariae resulted in the finding of the sexual adult (marita) of an unidentified species of Echinochasmus. ITS sequences of the adult and metacercaria corresponded with each other, and also with a cercaria isolated from a gravel snail (Lithoglyphus naticoides), with a 99.5-100% similarity.

Biomphalaria straminea (Mollusca: Planorbidae) as an intermediate host of Drepanocephalus spp. (Trematoda: Echinostomatidae) in Brazil: a morphological and molecular study

Species of trematodes belonging to the genus Drepanocephalus are intestinal parasites of piscivorous birds, primarily cormorants (Phalachrocorax spp.), and are widely reported in the Americas. During a 4-year malacological study conducted on an urban lake in Brazil, 27-collar-spined echinostome cercariae were found in 1665/15,459 (10.7 %) specimens of Biomphalaria straminea collected. The cercariae were identified as Drepanocephalus spp. by sequencing the 18S (SSU) rDNA, ITS1/5.8S rDNA/ITS2 (ITS), 28S (LSU) rDNA region, cytochrome oxidase subunit 1 (CO1), and nicotinamide adenine dinucleotide dehydrogenase subunit 1 (ND1) markers. In experimental life cycle studies, metacercariae developed in laboratory-reared guppies (Poecilia reticulata); however, attempts to infect birds and rodents were unsuccessful. Two closely related morphotypes of cercariae were characterized. One species, identified by molecular markers as a genetic variant of Drepanocephalus auritus (99.9 % similarity at SSU, ITS, LSU; 97.2 % at CO1; 95.8 % at ND1), differs slightly from an archived North American isolate of this species also sequenced as part of this study. A second species, putatively identified as Drepanocephalus sp., has smaller cercariae and demonstrates significant differences from D. auritus at the CO1 (11.0 %) and ND1 (13.6 %) markers. Aspects related to the morphological taxonomic identification of 27-collar-spined echinostome metacercariae are briefly discussed. This is the first report of the involvement of molluscs of the genus Biomphalaria in the transmission of Drepanocephalus and the first report of D. auritus in South America.

[Clonal variability in expression of geo- and photoorientation in cercariae of Himasthla elongata (Trematoda: Echinostomatidae)]

The study was carried out on Himasthla elongata, a digenean common in the coastal ecosystems of the northern European seas. This species utilises intertidal prosobranchs Littorina spp. as the first intermediate host, bivalves (in the White Sea, Mytilus edulis) as the second intermediate host and gulls as the final host. The periwinkles Littorina littorea infected with H. elongata rediae (parthenogenetic generations) were sampled in the intertidal of the White Sea (66 degrees 20' N, 33 degrees 38' E) and used as the source of cercariae. Periwinkles were collected from the settlement with the low prevalence of H. elongata. As shown earlier with the use of AFLP (Amplified Fragment Length Polymorphisms) method, rediae groups in all the infected periwinkles of this settlement arise from the infection of a mollusc with a single miracidium. Therefore, the cercariae shed by an infected mollusc have the same genotype or, in other words, represent a clone. Photo- and geoorientation of cercariae originating from different clones and aged 1 h and 6 h were analysed separately. It was shown that in general the larvae of each clone followed the behavioural pattern characteristics of the species (positive geoorientation and negative photoorientation). However, the degree of expression of this typical behaviour was different in different clones. An especially high variability was observed in the manifestation of geoorientation (in several clones, most larvae demonstrated negative geoorientation). Differences in the distribution of cercariae in the illumination gradient were almost equally associated with the interclonal variability and the age of the larvae. On the whole, as the age of cercariae increased, the positive geoorientation became more prominent, whereas the ratio of cercariae with the typical (negative) photoorientation decreased. Statistical analysis revealed significant differences between the cercarial clones both in the initial manifestation of geo- and photoorientation and in the changes in the character of these reactions with the larval age. Taking into account that each cercarial clone investigated had the same genotype, it seems very likely that the interclonal differences noted in this study are hereditary. Maintenance of a rather high level of genetic polymorphism by the character "expression of orientation reaction" in trematode cercariae may enhance the chances for successful transmission of these larvae. Such variability increases the scale of cercarial dispersion in space and promotes the successful infection of the hosts, whose behaviour is also subject to intra- and inter-population variability. Besides, cercariae whose behaviour deviates from the basic behaviour of the species may play the role of the population's potential for colonisation of new species of animal hosts.