Experimental data on the life-cycle of Petasiger grandivesicularis Ishii, 1935 (Trematoda: Echinostomatidae)

Larval stages of an echinostome were found in Planorbis planorbis in a brackish water lake on the Black Sea coast of Bulgaria. The cercaria is a large-tailed form with 19 collar spines. The life-cycle was completed in the laboratory using aquarium-reared fishes (Lebistes reticulatus, Puntius tetrazona tetrazona, P. pentazona pentazona, P. nigrofasciatus, Carassius auratus auratus and Xiphophorus helleri) as second intermediate hosts and canaries as definitive hosts. The redia, cercaria, metacercaria and experimentally reared adults are described. The species is determined as Petasiger grandivesicularis Ishii, 1935, and its cercaria is compared in detail with those of related forms. A key to the known large-tailed echinostome cercariae from the Palaearctic Region is presented.     

A revision of Petasiger Dietz, 1909 (Digenea: Echinostomatidae) and a key to its species

Petasiger Dietz, 1909 is revised, and a key to and lists of the records and hosts of the 18 recognised species are presented. The recognised species are: P. exaeretus Dietz, 1909, P. australis Johnston & Angel, 1941, P. combesi Zamparo, Overstreet & Brooks, 2005, P. floridus Premvati, 1968, P. grandivesicularis Ishii, 1935, P. islandicus Kostadinova & Skirnisson, 2007, P. johnstoni n. sp., P. megacanthus (Kotlán, 1922), P. minutissimus Gogate, 1934, P. neocomense Fuhrmann, 1927, P. nitidus Linton, 1928, P. novemdecim Lutz, 1928, P. oschmarini Kostadinova & Gibson, 1998, P. phalacrocoracis (Yamaguti, 1939), P. pseudoneocomense Bravo-Hollis, 1969, P. pungens (Linstow, 1894), P. soochowensis Ku, Chiu, Li & Zhu, 1977 and P. variospinosus (Odhner, 1910). Seven of these species are redescribed on the basis of type and newly collected material. P. laricola Ku, Chiu, Li & Zhu, 1977, Echinochasmus fotedari Chishti & Mir, 1989 and P. neocomense of Cankovi?, Kazi? & Milka (1983) are considered synonyms of P. pungens; P. longicirratus Ku, 1938, P. skrjabini Bashkirova, 1941 and P. nitidus of Chen et al. (1985) synonyms of P. neocomense; P. caribbensis Nassi, 1980 a synonym of P. novemdecim; and P. tientsinensis Ku, Chiu, Li & Zhu, 1977 a synonym of P. exaeretus. P. johnstoni n. sp. is described from Tachybaptus ruficollis novaehollandiae in Australia. It is readily distinguished from the most closely-related P. grandivesicularis Ishii, 1935 and P. australis Johnston & Angel, 1941 by the smaller size of the body and angle collar spines and differences in most other metrical characters. Species attributed to Petasiger which are here considered species inquirendae are: P. antigonus Nigam, 1944 sp. inq., P. chandleri Abdel-Malek, 1952 sp. inq., P. jubilarum Elperina in Skrjabin, Petrov & Bashkirova, 1947 sp. inq., P. nicolli Pande, 1939 sp. inq. and P. spasskyi Oshmarin in Skrjabin, Petrov & Bashkirova, 1947 sp. inq.; and Echinoparyphium inopinatum (Baer, 1959) n. comb. is a species previously attributed to Petasiger.     

A comparative study of cercarial chaetotaxy in two species of Petasiger Dietz, 1909 (Digenea: Echinostomatidae)

The chaetotaxy of two types of cercariae found in naturally infected Planorbis planorbis in a brackish water lake in Bulgaria is described. The comparison of the sensory patterns shows the distinct species status of the cercariae of P. grandivesicularis and Petasiger sp. The morphology of the cercaria of Petasiger sp. is described and compared with that of known large-tailed Petasiger cercariae from the Palaearctic. It is suggested that the unidentified species of cercaria is probably a larval stage of P. pungens.     

Morphological and molecular data for larval stages of four species of Petasiger Dietz, 1909 (Digenea: Echinostomatidae) with an updated key to the known cercariae from the Palaearctic

Recent molecular phylogenetic studies on fish tapeworms of the genus Caryophyllaeus Gmelin, 1790 (Cestoda: Caryophyllidea), parasites of cyprinid fishes in the Palaearctic Region, have revealed unexpected phenotypic plasticity that seems to be related to definitive hosts. In the present paper, Caryophyllaeus brachycollis Janiszewska, 1953 is redescribed and its two morphotypes are circumscribed on the basis of newly-collected specimens. Morphotype 1 from barbels [Barbus spp. including the type-host Barbus barbus (L.); Barbinae] and chubs (Squalius spp.; Leuciscinae) is characterised by a more robust body with spatulate scolex, which is only slightly wider than a very short neck region, and the anterior position of the testes and vitelline follicles, which begin immediately posterior to the scolex. Specimens of Morphotype 2 from breams (Abramis spp., Ballerus spp. and Blicca spp.; Abraminae), which have been previously misidentifed as Caryophyllaeus laticeps (Pallas, 1781), possess a more slender body with a flabellate scolex, which is much wider than a long neck, and the first testes begin at a considerable distance posterior to the first vitelline follicles. Despite conspicuous differences in the scolex morphology and the anterior extent of the testes and vitelline follicles, both morphotypes are identical in the morphology of the posterior end of the body, in particular that of the cirrus-sac, which is large, thick-walled, elongate-pyriform, and contains a long cirrus, and in the distribution of the vitelline follicles, which surround medially vas deferens near the cirrus-sac. A specimen of Morphotype 1 from B. barbus from the Argens River, France, is designated as neotype of C. brachycollis. The presence of phenotypic plasticity in morphological characteristics previously used for differentiation of species of Caryophyllaeus may confound species identification, which is crucial for biodiversity, ecological and evolutionary studies. To avoid these potential problems, combination of morphological and molecular data is strongly recommended.     

Studies on the life-cycle of Ganeo tigrinus Mehra & Negi, 1928 (Digenea)

The life-history stages of Ganeo tigrinus Mehra & Negi, 1928 infecting the Indian bull frog Hoplobatrachus tigerinus (Daudin) are described, those from cercaria to egg-producing adult having been established in the laboratory. Non-virgulate xiphidiocercariae are released by the planorbid snail Indoplanorbis exustus (Deshayes). Metacercariae occur in the haemocoel of dragonfly nymphs and become infective to the frog H. tigerinus within 15 days. The pre-patent period is 45 days. Growth and development of both metacercariae and adults are described in detail. Comments on the systematic position of Ganeo Klein, 1905 are included.     

Reproduction of the trematode Echinostoma caproni parthenites (Digenea: Echinostomatidae)

Dynamics of the reproduction in the trematode Echinostoma caproni parthenites (Echinostomatidae) was observed. Early laying and maturation of the generative cells are for the first time shown to be characteristic for all parthenogenetic generations. Really the process of reproduction had been finishing to the beginning of the generating of new age by parthenites. Mother sporocysts, as well as redia of different generations, in fact stop producing new generative cells with the beginning of the generating of new age, and assume the function of a brood pouch. This feature was considered previously as peculiar mainly to mother sporocysts. Data on the autotomy of the anterior body end in mother sporocysts are verified. In our opinion, these data are an evidence of an early manifestation of the evolutionary trend to the morpho-functional regress and disintegration of the parasitic stage of mother sporocyst.     

Complete Mitochondrial Genome of Echinostoma hortense (Digenea: Echinostomatidae)

Echinostoma hortense (Digenea: Echinostomatidae) is one of the intestinal flukes with medical importance in humans. However, the mitochondrial (mt) genome of this fluke has not been known yet. The present study has determined the complete mt genome sequences of E. hortense and assessed the phylogenetic relationships with other digenean species for which the complete mt genome sequences are available in GenBank using concatenated amino acid sequences inferred from 12 protein-coding genes. The mt genome of E. hortense contained 12 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and 1 non-coding region. The length of the mt genome of E. hortense was 14,994 bp, which was somewhat smaller than those of other trematode species. Phylogenetic analyses based on concatenated nucleotide sequence datasets for all 12 protein-coding genes using maximum parsimony (MP) method showed that E. hortense and Hypoderaeum conoideum gathered together, and they were closer to each other than to Fasciolidae and other echinostomatid trematodes. The availability of the complete mt genome sequences of E. hortense provides important genetic markers for diagnostics, population genetics, and evolutionary studies of digeneans.     

Echinochasmus leopoldinae n. sp. (Trematoda: Echinostomatidae) and data on its life-cycle

The echinostomatid trematodeEchinochasmus leopoldinae n. sp. is described on the basis of adults found in the intestine of chicks and mice experimentally infected with metacercariae from the gills of the cichlid fishesCichlasoma urophthalmus andC. synspilum from the Peninsula of Yucatan.E. leopoldinae, which had previously been misidentified asE. zubedakhaname Nasir & Díaz, 1968, is characterised by the presence of 20 collar spines with one angular spine on each side and vitelline follicles confluent in the posterior part of the body. A differential diagnosis ofEchinochasmus species possessing 20 collar spines is provided, and the developmental stages (redia, cercaria, metacercaria and adult) ofE. leopoldinae are described.     

Development of the partenitae infrapopulation of Echinostoma caproni (Digenea: Echinostomatidae)

The first generation of Echinostoma caproni partenitae is represented maternal sporocysts developing in the cardium of the Biomphalaria mollusk. During all their life, they produce rediae of maternal generation. Rediae of Echinostoma caproni of all generations are similar. The first generation consists of maternal rediae forming only redoid embryos. Due to this process, the number of partenitae increases very fast. The next generations are represented by daughter rediae. In the beginning of their life they produce redoid embryos but later begin forming cercariae. The number of rediae produced before this shift of production depends on the population density. Further, the partenitae retain their potential ability to form rediae but realize it in exceptional cases. Generative organs of all generations are germinal masses. Proliferation of generative elements and beginning stages of redia and cercaria development take place within these masses. The infrapopulation of E. caproni belongs to the "prolonged type", because it is a complete microhemipopulations; its existence is limited by a lifespan of the mollusk host.     

Petasiger oschmarini n. sp. (Digenea: Echinostomatidae) in the grebes Podiceps grisegena (Bod.) and P. auritus (L.) (Aves: Podicipedidae) from Kamchatka,Russia

A re-examination of three sets of trematodes collected in two species of grebes, Podiceps grisegena and P. auritus, from the Kamchatka region of eastern Russia, previously identified as Petasiger neocomense, revealed that they actually represent a new species, which is named Petasiger oschmarini. Characteristic morphological features of the new species include: a head collar possessing a constant number of 19 spines; a large cirrus-sac comparable in size to the ventral sucker, containing a bipartite seminal vesicle and a well-developed pars prostatica; a large bulb-like cirrus similar in size to the testes; a long forebody; a long oesophagus; testes situated obliquely or symmetrically; and lateral vitelline fields which are not confluent in the forebody. The new species is distinguished from all Palaearctic and Nearctic members of Petasiger which possess 19 collar spines. The material described by Oschmarin (1950) as P. neocomense is considered to be conspecific.     

Life cycle of Stephanoprora uruguayense (Digenea: Echinostomatidae) in Argentina

The life cycle of Stephanoprora uruguayense Holcman et Olagüe, 1989, was experimentally resolved. In an artificial pond in the Zoological Garden in Buenos Aires City, Argentina, Heleobia parchappei (Hydrobiidae) was found to be releasing large-tailed cercariae with a prepharyngeal body, but lacking collar spines and corpuscles in the excretory system. Metacercariae, which encysted on the gills of naturally and experimentally infected Cnesterodon decemmaculatus (Poecilidae), developed collar spines and corpuscles in the excretory system in 7 days. Sexually mature adults were recovered from chicks and immature adults from mice fed metacercariae from C. decemmaculatus. Eggs shed in chick feces developed to miracidia within 10 days; sporocysts were found on the gills of snails. Stephanoprora uruguayense and S. denticulata from Europe are similar in adult morphology, but can be distinguished by morphological and behavioral features of larvae. Likewise, although S. denticulata and S. paradenticulata from Venezuela are similar to S. uruguayense in adult morphology, they differ considerably in larval morphology and intermediate hosts.     

Tegumental ultrastructure of the juvenile and adult Himasthla alincia (Digenea: Echinostomatidae)

The tegumental ultrastructure of juvenile and adult Himasthla alincia (Digenea: Echinostomatidae) was observed by scanning electron microscopy. One-, 5- (juveniles) and 20-day-old worms (adults) were harvested from chicks experimentally fed metacercariae from a bivalve, Mactra veneriformis. The juvenile worms were elongated and curved ventrally. The head crown bore 31 collar spines, arranged in a single row. The lip of the oral sucker had 12 paired, and 3 single type I sensory papillae, and the ventral sucker had about 25 type II sensory papillae. The anterolateral surface between the two suckers was densely packed with tegumental spines with 4-7 pointed tips. The adult worms were more elongated and filamentous, and had severe transverse folds over the whole body surface. On the head crown and two suckers, type I and II sensory papillae were more densely distributed than in the juvenile worms. Retractile brush-like spines, with 8-10 digits, were seen on the anterolateral surface, whereas claw-shaped spines, with 2-5 digits, were sparsely distributed posteriorly to the ventral sucker. The cirrus characteristically protruded out, and was armed with small spines distally. The surface ultrastructure of H. alincia was shown to be unique among echinostomes, especially in the digitation of its tegumental spines, the distribution of sensory papillae and by severe folds of the tegument.     

Surface ultrastructure of juvenile and adult Acanthoparyphium tyosenense (Digenea: Echinostomatidae)

The tegumental ultrastructure of juvenile and adult Acanthoparyphium tyosenense (Digenea: Echinostomatidae) was observed by scanning electron microscopy. One- to 3-day-old juveniles and 10-day-old adults were harvested from chicks experimentally fed metacercariae from a bivalve, Mactra veneriformis. The juvenile worms were minute, curved ventrally, and had 23 collar spines characteristically arranged in a single row. The lips of the oral sucker had 7 single aciliated sensory papillae and 4 grouped uniciliated sensory papillae. The ventral sucker had 25 aciliated round swellings on its lip. The anterolateral surface between the 2 suckers was densely packed with tongue-shaped tegumental spines, and the ventral surface just posterior to the ventral sucker was covered with peg-like spines. Retractile, peg-like spines were seen on the anterolateral surface, whereas scale-like spines with round tips and broad bases were sparsely distributed posterior to the ventral sucker. The cirrus was characteristically protruding and armed with minute spines. The surface ultrastructure of A. tyosenense was unique, especially in the number and arrangement of collar spines, shape, and distribution of tegumental spines and in distribution of sensory papillae.     

Diurnal migration of Echinostoma caproni (Digenea: Echinostomatidae) in ICR mice

Twenty-four female ICR mice, 12 acclimated to a 12 ∶ 12 light-dark cycle and 12 to a 12 ∶ 12 dark-light cycle for 7 days, were each infected with 10 metacercariae of Echinostoma caproni. Infected mice were maintained on their respective lighting regimes for 28 days. Six mice (3 from each group) were necropsied at 4-hr intervals beginning at 0700 hr. The small intestine was removed, opened, and the position of individual worms and worm clusters was measured to the nearest 0.1 cm. Each intestine was subsequently divided into 20 equal segments and individual worms and worm clusters were assigned to the appropriate segment based on the original measurements. All worms were found in the posterior 55% of the intestine (ileum). All posterior segments (10-20), with the exception of segment 18, harbored at least 1 worm at some time. A Monte Carlo simulation of worm abundance in segments 10-17 over all time periods indicated a random distribution, while the same analysis of segments 10-20 indicated a non-random distribution due to large numbers of worms in segment 20 and to the absence of worms in segment 18. To analyze temporal changes in worm distribution, mice were grouped by time of necropsy as follows: night (1900 and 2300 hr), morning (0300 and 0700 hr), and day (1100 and 1500 hr). During the night and morning, E. caproni was heavily concentrated in segments 10-17 and, during the day, worms were located more posteriorly, with a heavy concentration in the last segment (20).     

The life-cycle of Helicometra gibsoni n. sp. (Digenea: Opecoelidae)

The life-cycle of Helicometra gibsoni n. sp., an opecoelid trematode of marine fishes, is elucidated and the life-history stages are described. Natural infections with the cercariae, which are typically opecoelid in many respects but characterised by having very long, extensile tails, were found in the intertidal snail Anachis terpsichore collected from the Lawson's Bay Coast, Bay of Bengal. Metacercariae were found in the thoracic muscles of the shooting shrimp Alphaeus malabaricus as prominent, reddish-brown, oval cysts. Laboratory experiments demonstrated that 14 days are required for the development of cercaria into the infective metacercarial stage in shrimps. Natural infections with the adult fluke were found in Scorpaenopsis cirrhosus. Therapon jarbua served as an experimental host. Fourteen-day-old metacercariae fed to T. jarbua developed into egg-producing adults in 40–43 days. Intra-specific variations noted in the flukes obtained from natural and experimental infections are presented. H. fasciata of Madhavi (1975) is regarded as a synonym of H. gibsoni.