Systematic analysis of the Diplostomidae and Strigeidae (Trematoda)

A systematic analysis of the genera in the Diplostomidae and Strigeidae was made using the Proterodiplostomidae as the outgroup. The Proterodiplostomidae was the family with the greatest preponderance of primitive characters and its monophyly was supported by the unique paraprostate gland. However, no character state supported the monophyly of the Diplostomidae sensu Dubois, 1970. That paraphyletic taxon was composed of 3 monophyletic groups: the pseudosuckerless Neodiplostomidae n. fam. had the most primitive character states of the 3 and its monophyly was based on characters in the neascus/neodiplostomulum metacercariae; the Bolbophoridae n. fam., with pseudosuckers, had its monophyly supported by characters present in the newly named prodiplostomulum metacercaria; and the emended Diplostomidae, also with pseudosuckers, had the most derived states and its monophyly was supported by characters present in the diplostomulum. The presence of pseudosuckers united the Bolbophoridae n. fam., the emended Diplostomidae, and the Strigeidae as a monophyletic assemblage. The Strigeidae had the most derived characters of these 3 taxa and its monophyly was supported by characters in the tetracotyle and the cup-shaped forebody and bilobed tribocytic organ of the adult. In general, the adult stages of these strigeoid families showed very conserved morphology and it was the metacercariae that possessed the innovations. The conserved adult morphology was typical of what one might expect if the intramolluscan stages were analyzed. Thus, the data were concordant with the view that the mollusc and vertebrate definitive host were the original hosts to the Digenea and that the second intermediate host and metacercaria were more recently intercalated. More specifically, the phylogeny of these groups suggested that ancestral bisegmented strigeoids originally infected reptiles, they subsequently radiated into birds with which they coevolved extensively, and on 5 separate occasions they radiated into mammals. The radiations into mammals were, by all available evidence, preceded by second intermediate host shifts from fish to amphibians.     

Cercarial chaetotaxy of Codonocephalus urniger (Rudolphi, 1819) (Trematoda: Diplostomidae)

The chaetotaxy of Codonocephalus urniger (Rudolphi, 1819) cercariae recovered from Lymnaea palustris in a brackish water lake in Bulgaria is described and figured. Comparisons with Diplostomum spathaceum (Rudolphi, 1819) and D. pseudospathaceum Niewiadomska, 1984 cercariae indicate a similar general pattern in the distribution of sensilla but with marked differences in their number and arrangement on the ventral sucker, tail stem and furcae. Data on the chaetotaxy of other diplostomid species are used to reveal the similarities and variations in some complexes within the members of Diplostomidae with known cercarial chaetotaxy.     

Diplostomiasis (Trematoda: Strigeidae) in Arctic charr (Salvelinus alpinus) from Charr Lake, northern Labrador

The eyes of 273 Arctic charr (Salvelinus alpinus) taken from Charr Lake, the Ikarut River, and Hebron Fiord in northern Labrador were examined for diplostomula. All anadromous charr taken from the Ikarut river and Hebron Fiord were uninfected. The resident fish from Charr Lake were parasitized with large numbers of diplostomula and intensity of infection increased with age and length. Infections of up to 2,852 diplostomula in one fish are the highest recorded. Such infections did not appear to affect the vision of the charr.     

On the development of body-wall musculature Diplostomum chromatophorum metacercariae (Trematoda: Diplostomidae)

The body-wall musculature of invasive cercariae and metacercariae of Diplostomum chromatophorum at different intervals after the penetration into the experimental intermediate host Cyprinus carpio (1, 3, 5, 6, 7, 10, 12, 20, 34, 40 days) has been investigated with the help of TEM technique. During the first 10 days after the invasion (in conditions of our experiment), the cercarial subtegumental muscle fibres degenerate. These muscles are replaced by newly formed ones. Mass differentiation of myoblasts beneath the tegument was observed in 7-10-day-old metacercariae. Obtained data indicate the metamorphosis of body-wall musculature during the morphogenesis in Diplostomum chromatophorum metacercariae.     

The development of the genital system in Ichthyocotylurus variegatus (Trematoda: Strigeidae)

The development of Ichthyocotylurus variegatus from metacercariae to ovigerous adults in the natural definitive host (Larus ridibundus) was examined at 24 h intervals. The metacercariae develop to the adults through a somatic growth of hindbody; the gametogeny and vitellogenesis take 4-6 days. During the first day of development the pair of testes are separated from the genital anlage. The ovary differentiates one day later. Genital ducts are completely differentiated on 4th day after the beginning of spermatogenesis and cogenesis. The vitelline cells developed from 2nd to 5th day. They take an origin from the subtegumental cells of hindbody. The hind part of uterus in strigeoid adults is identical to the metraterm of other trematodes. The spermaduct along all its length works as a spermatic bladder.     

Toxicity of cadmium and zinc to Diplostomum spathaceum (Trematoda: Diplostomidae) cercarial survival

The toxicity of cadmium and zinc at concentrations ranging from 0.1 to 10000 microg/l was investigated with cercariae of Diplostomum spathaceum at three temperatures (12, 20, 25 degrees C) and three levels of water hardness (distilled water, soft water, hard water). Under most environmental conditions survival of cercariae was reduced by increasing metal concentration. Increasing water hardness and decreasing water temperature caused an increase in the survival of both control and metal exposed cercariae. However, with decreasing temperature increased survival of metal-exposed cercariae above the control occurred at a number of low metal concentrations. Differences in the relative toxicity of cadmium and zinc to cercariae was dependent on the environmental conditions of exposure. The two heavy metals demonstrated little toxicity to cercariae during the period of maximum cercarial infectivity (0-5 h).The mechanisms of metal toxicity and their effects on cercarial survival are discussed.     

Morphology and life history of Alaria mustelae Bosma 1931 (Trematoda: Diplostomatidae) from Minnesota mustelids.

On the bases of morphological and life history studies, flukes of the subgenus Paralaria from Minnesota mustelids were identified as Alaria (Paralaria) mustelae Bosma 1931. Alaria (P.) canadensis Webster and Wolfgang 1956 and A. (P.) taxideae Swanson and Erickson 1946 are synonyms of A. mustelae (new synonymy).     

Central European Strigeidae Railliet, 1919 (Trematoda: Strigeidida): Molecular and comparative morphological analysis suggests the reclassification of Parastrigea robusta Szidat, 1928 into Strigea Abildgaard, 1790

Strigeidae Railliet, 1919 are digenean parasites of birds and mammals that are characteristic by their cup-shaped forebody and bilobed holdfast organ. Despite that the family is taxonomically unsettled, particularly due to a very limited number of visible autapomorphic identification features, molecular phylogenetics have never been applied to analyze the relationships among European members of Strigeidae except for the genus Ichthyocotylurus. Here, we analyze the Strigeidae found during the examination of Czech birds performed from 1962 to 2017, and we provide comparative measurements and host spectra, including prevalence and intensity; we also provide and analyze sequences of four DNA loci of 12 of the Strigeidae species. We suggest the reclassification of Parastrigea robusta Szidat, 1928 as Strigea robusta (Szidat, 1928) Heneberg and Sitko, 2018 comb. n. The genera Strigea Abildgaard, 1790 and Parastrigea Szidat, 1928 appear paraphyletic, and morphological diagnostic features of genera within Strigeini Dubois, 1936 are invalid. The mute swan Cygnus olor hosts two Cotylurus spp., Cotylurus syrius Dubois, 1934 and a second species with molecular identification features shared in part with Cotylurus cornutus (Rudolphi, 1808) and Cotylurus gallinulae Lutz, 1928. New host records are provided for seven species. Analyses of non-European genera of the Strigeidae are needed to provide an updated key to Strigeini.     

First Finding of Ornithodiplostomum scardinii (Schulman, 1952) Sudarikov et Kurotschkin, 1968 (Trematoda,Diplostomidae) in Rybinsk Reservoir

During a parasitological survey of nonnative fish species—rudd Scardinius erythrophthalmus—in the Rybinsk Reservoir, the metacercariae Ornithodiplostomum scardinii were found in its brain. This is the first find of this helminth in the Upper Volga basin. The rudd was infected with the prevalence 31.3%, with an intensity of 1–12 parasites per fish. Data on the current distribution of the trematode O. scardinii in the Volga River basin are provided.     

Infectivity of Ornithodiplostomum ptychocheilus and Posthodiplostomum minimum (Trematoda: Diplostomidae) cercariae following exposure to cadmium

The effect of cadmium (Cd) exposure on infectivity of cercariae of 2 trematode species (Ornithodiplostomum ptychocheilus and Posthodiplostomum minimum) to their second intermediate fish host was evaluated. Individual fathead minnows (Pimephales promelas) were exposed to cercariae that had been treated with Cd solutions at concentrations of 0, 2, 20, or 200 microg/L for 2 hr. Two weeks later, the numbers of encysted metacercariae in the brain (O. ptychocheilus) and body cavity (P. minimum) of the fish were evaluated. ANOVA analyses indicated a strong negative effect of Cd concentration on cercaria infectivity. The species x Cd concentration interaction was not significant, indicating that the magnitude of Cd-induced reduction in infectivity was similar between O. ptychocheilus and P. minimum. The results show that short-term exposure to Cd, even at low concentrations, interferes with transmission processes that affect the recognition and penetration of cercariae, the migration and survival of metacercariae within the second intermediate host, or both.     

Sensory apparatus of the cercaria of 2 species of the genus Apatemon (Trematoda: Strigeidae)

The sensory apparatus of cercariae of two species of trematodes (A. cobitidis and A. minor) is described. The species differ both morphologically and biologically. The only common feature in the sensory apparatus of the above species is the topography of sensillae in the posterior half of the lateral complex of the caudal trunk and of the furcal complex.