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.     

Redescription of Petasiger exaeretus Dietz, 1909 and P. phalacrocoracis (Yamaguti, 1939) (Trematoda: Echinostomatidae), parasites of cormorants

Two echinostome trematodes of the genus Petasiger, P. exaeretus Dietz, 1909 and P. phalacrocoracis (Yamaguti, 1939), parasitising cormorants (Phalacrocoracidae), were found in Phalacrocorax carbo L. from the Czech Republic. Both taxa are redescribed and literary data on their occurence in cormorants are reviewed. The species P. exaeretus appears to be a rather rare species, hitherto recorded in Phalacrocorax carbo in Europe, Kirghizia and Azerbaidzhan. P. baschkirovi Ablassov & Iksanov, 1959 is synonymized with P. exaeretus. P. phalacrocoracis (syn. P. hospitale (Mendheim, 1940) and P. exaeretus auct. nec Dietz, 1909), which has previously been misidentified and erroneously designated as P. exaeretus, appears to be the commonest species of the genus, parasitising cormorants in the Palaearctic Region (Europe, CIS [USSR], Japan) and in Australia. Differential diagnoses of both the above mentioned species are 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.     

Preliminary data on the chromosomes of Echinostoma caproni Richard, 1964 (Trematoda: Echinostomatidae)

The karyotype of Echinostoma caproni Richard, 1964 is studied. There are eleven pairs of chromosomes (2n=22). Two pairs are submetacentric (Nos. 4 and 5). C-banding methods revealed a large block of heterochromatin in No. 3 and two blocks in No. 5. E. cinetorchis (see Terasaki et al., 1982) and E. barbosai (see Mutafova & Kanev, 1983) also have 22 chromosomes, but the metacentric or submetacentric chromosomes are Nos. 8 and 11 for the former and No. 10 for the latter. ac]19860425     

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.     

Redescription of Echinostoma trivolvis (Cort, 1914) (Trematoda: Echinostomatidae) with a discussion on its identity

The life-cycle of Echinostoma trivolvis (Cort, 1914) has been completed experimentally and the validity and identity of this species are discussed. Synonyms for cercariae and adults of E. trivolvis are as follows: Cercaria trivolvis Cort, 1914, C. trisolenata Faust, 1917, C. acanthostoma Faust, 1918, C. complexa Faust, 1919; Distoma echinatum Zeder, 1803, of Leidy (1888, 1904) and Hassall (1896); E. echinatum (Zeder, 1803) of Hassall (1896), Stiles & Hassall (1895), Barker & Laughlin (1911), Barker (1916) and Swales (1933); E. revolutum (Frölich, 1802) Dietz, 1909 of Johnson (1920), Fallis (1934), Beaver (1937) and Fried & co-workers (1968–1989); E. armigerum Barker & Irvine, 1915; E. coalitum Barker & Beaver, 1915; E. callawayensis Barker & Noll, 1915; E. paraulum Dietz, 1909 of Miller (1937); E. multispinosum Vigueras, 1944; and Echinoparyphium contiguum Barker & Bastron, 1915. The first intermediate host is the planorbid snail Helisoma trivolvis. Second intermediate hosts are various pulmonate and prosobranch snails, mussels, planarians, fishes, frogs, tadpoles and freshwater turtles. Final hosts are various birds and mammals. E. trivolvis occurs only in North America.     

Studies on the attachment response of Isthmiophora melis cercariae (Trematoda: Echinostomatidae)

The cercaria of Isthmiophora melis is relatively specific to suitable intermediate hosts, amphibia and fish, as early as the stage of attachment. Attachment responses are maximally stimulated by intact amphibia, whereas isolated frog tissues have a reduced efficiency. Human urine contains attachment triggering substances. Its effectiveness is reduced, when carbonate systems are removed, and may be restored by addition of carbonate. Aqueous solution systems of dissolved CO2 and H2CO3/HCO-3 stimulate attachment responses, especially at pH 6.0-7.5. The attachment response to frog skin surface seems to be triggered by the buffering system, which uses carbonate solution equilibria as important components.     

The life-cycle of Petasiger islandicus Kostadinova & Skirnisson, 2007 (Digenea: Echinostomatidae) elucidated with the aid of molecular data

The small planorbid snail Gyraulus cf. laevis (Alder) from Lake Myvatn in Iceland was found to emit large-tailed cercariae with 19 collar spines, and three-spined sticklebacks Gasterosteus aculeatus L. were infected with metacercariae of a species of Petasiger Dietz, 1909. Comparative sequence analysis using ND1 mitochondrial DNA sequences revealed that the rediae and cercariae are conspecific with P. islandicus Kostadinova & Skirnisson, 2007, recently described from an isolated population of the horned grebe Podiceps auritus (L.) at the lake. The redia, cercaria and metacercaria are described and compared with related forms.