Ultrastructure of the forebody and foregut tegument and eccrine gland cells of Crepidostomum metoecus (Trematoda: Digenea: Allocreadiidae)

The forebody and foregut of Crepidostomum metoecus Braun, 1900 are invested with a tegument bearing regularly arranged surface tubercles comparable with the aspidogastrean surface structures. The tegument of the ventrolateral lobes and of the prepharynx is penetrated by ducts of eccrine gland cells. The frontal and prepharyngeal gland cells, localised in the parenchyma, discharge electron-dense granules. Their ducts are lined by peripheral microtubules and fixed to the tegument plasmalemma by a septate junction. The functional roles of these glands are discussed.     

Transmission electron microscopy of intra-tegumental sensory receptors in the forebody of Crepidostomum metoecus (Digenea: Allocreadiidae)

In the adult fish trematode Crepidostomum metoecus (Braun, 1900), four types of sensory receptors were observed inside the forebody tegument and one type beneath the tegument basal lamina. Two types of sensory receptors extend through the thickness of tegument and have a free cilium inside a pit (types I and II). Two types (III and IV) are nonciliate and entirely intra-tegumental in location. Type IV receptor with large horizontal and thin vertical rootlets was described earlier in aspidogastreans only. Below the basal lamina, nerve endings in close association with muscle fibres, comparable with those in the Aspidogastrea, were detected.     

The ecology of Crepidostomum species (Allocreadiidae: Digenea) in the salmonoids of Lake Yli-Kitka in northeastern Finland

Crepidostomum spp. were studied from 417 whitefish (Coregonus acronius Rapp, 1854), 220 vendace (Coregonus albula L.) and 38 brown trout (Salmo trutta m. lacustris (L.)) from Lake Yli-Kitka in northeastern Finland during 1980-1983.12.7% of the whitefish were infected with Crepidostomum with a mean intensity of 4.6 worms per infected fish. The species involvedare C. farionis (Müller, 1784) and Crepidostomum wikgreni Gibson et Valtonen, 1988, which differed from C. farionis in the number and size of the eggs. Both types were encountered in the gall-bladder and intestine, but were unable to be distinguished as immature stages. 21% of the brown trout harboured C. farionis in the intestine with a mean number of 1.5 worms per infected fish. Two C. farionis specimens occurred also in the intestine of one vendace. Whitefish smaller than 150 mm did not harbour Crepidostomum specimens, but in bigger fish the prevalence and the mean intensity of infection increased to a certain limit as the fish got larger. The prevalence of Crepidostomum infection also clearly increased during the three seasons in the three size-groups studied. The seasonal pattern of Crepidostomum in whitefish of the size greater than or equal to 150 mm was variable in that the lowest values, both in the prevalence and mean intensity of infection, occurred between September and December in 1980 and between April and August in 1982. Reinvasion was found throughout the year, although the main recruitment occurred during autumn and early winter. Eggs matured between late spring and early autumn. The smallest worms occurred mainly in the gall-bladder, and most of the gravid specimens were located in the intestine. Both the variance-to-mean ratio and the low values of the parameter k of the fitted negative binomial distribution reveal the Crepidostomum specimens are overdispersed in the whitefish of Lake Yli-Kitka.     

Transmission electron microscopy of presumed sensory receptors in the forebody papillae of Crepidostomum metoecus (Digenea: Allocreadiidae)

Five types of presumed ciliate sensory receptors were detected in the forebody papillae of the adult fish trematode, Crepidostomum metoecus (Braun, 1900). The cilia are short and submerged in a tegumental pit. The apical bulb part of all types of receptors observed is supported by a dense collar and connected to the tegument basal plasma membrane by a circular septate junction. In sensory receptors types I and III no rootlet is present; the bulbs of sensory receptors types III and IV contain an electron-dense formation.     

Monostephanostomum nolani sp. n. and M. krusei Reimer, 1983 (Digenea: Acanthocolpidae) from carangid fishes from coral reef waters off Australia

Monostephanostonum nolani sp. n. is described from Carangoides plagiotaenia Bleeker, off Lizard Island, Great Barrier Reef, Queensland, Australia. It differs from all other species in the genus except M. manteri Kruse, 1979 in that the vitellarium reaches into the forebody. It differs from M. manteri in the ventral hiatus in the circum-oral spine row, the extent of the vitellarium in the forebody, where it is not confluent, its elongate pharynx and its smaller eggs. Monostephanostoinum krusei Reimer, 1983 is redescribed from Pseudocaranx dentex (Bloch et Schneider) from Ningaloo Reef off Western Australia. It is considered similar to M. nolani, differing in the vitellarium being restricted to the hindbody, but sharing with M. nolani an unusual arrangement of small body-spines on the antero-ventral surface. It is also morphologically very similar to Monostephanostomum roytmani (Parukhin, 1974), which apparently lacks the diminutive antero-ventral body-spines. A key to eight recognized species in the genus is presented.     

落叶松种皮微形态特征及种子鉴定的研究

本文运用日本Ｓ－５７０扫描电镜，观察了落叶松属六个种的种皮微形态特征，发现该属各种间背面纹饰，腹面纹饰，种孔周围纹饰差异明显；各种间种孔周围形态各具特色。可根据种皮微形态特征的差异，准确鉴别落叶松种子。     

Ritacestus gen. n. (Cestoda: Proteocephalidea) and redescription of R. ritaii comb. n., a parasite of Rita rita (Siluriformes) in India

A new genus, Ritacestus, is proposed to accommodate Ritacestus ritaii (Verma, 1926) comb. n. (syn. Proteocephalus ritaii), a parasite of the catfish Rita rita (Hamilton) in India. The new genus, which is placed in the Gangesiinae, is characterized by (i) a small, subspherical scolex formed by four large lobes separated from one another by longitudinal grooves, with a large, widely oval to pyriform rostellum-like apical organ, larger than suckers and possessing an apical hemispherical depression; (ii) paramuscular and cortical position of some vitelline follicles (most follicles are situated medullary); (iii) ventral and dorsal bands of vitelline follicles usually uninterrupted ventral to terminal genitalia and reaching to the posterior margin of proglottides; (iv) the vagina always anterior to the cirrus-sac; (v) a large size of the body (length up to 51 cm); and (vi) development of the uterus of type 2. In its morphology, especially shape of the scolex and apical organ, and paramuscular and cortical position of some vitelline follicles, Ritacestus resembles Postgangesia Akhmerov, 1969, but differs in the presence of a genital atrium (both genital pores of Postgangesia are separate), the anterior position of the vagina (almost always posterior in the latter genus), position of vitelline follicles in cross sections (dorsal and ventral bands in Ritacestus versus only a lateral band in the latter genus), and dorsal excretory canals indistinguishable in mature and gravid proglottides of R. ritaii (well developed in Postgangesia spp.). The type and only species of the genus, R. ritaii, is redescribed on the basis of new material from the type host from the Ganges River basin in India and its neotype is designated.     

Taxonomic status of Ascocotyle (Phagicola) rara Arruda, Muniz-Pereira et Pinto, 2002 (Digenea: Heterophyidae)

Holotype and paratype of Ascocotyle (Phagicola) rara Arruda, Muniz-Pereira et Pinto, 2002, a heterophyid trematode recently described on the basis of two worms collected by Lauro Travassos in 1921 in the intestine of Ixobrychus exilis (Gmelin) from Brazil, were studied. The morphology of the worms revealed their conspecificity with Ascocotyle (Phagicola) angeloi Travassos, 1928 found in the same host. Both the taxa have a similar length (between 600 and 900 microm) and shape of the body (long pyriform), the long intestinal caeca reaching to the ovarian level, a long posterior muscular prolongation of the oral sucker and the prepharynx, transverse uterine loops situated between the ventral sucker and testes, and the gonotyl with more than 20 digitiform pockets. Consequently, A. (P.) rara is proposed as a junior synonym of Ascocotyle (Phagicola) angeloi.     

A new species of the genus Chauhanellus Bychowsky et Nagibina, 1969 (Monogenea) from the gills of a sea fish Tachysurus dussumieri (Val.) from Andhra Pradesh, India

Chauhanellus chauhani sp. n., collected from the gills of a sea cat-fish, Tachysurus dussumieri (Valenciennes) from the Bay of Bengal, off the coast of Kakinada, Andhra Pradesh, India is described and illustrated. It differs from the related species of the genus--C. oculatus, C. flexiosus, C. australis, C. nagibinae, and C. pedunculatus--in the shape and articulation of accessory piece with cirrus and in having a crescentic posteromedian process on its dorsal bar. It has five transverse hard structures on the ventral surface of peduncular region, by which it differs from C. oculatus and C. australis the latter have 10-11 and 3 such hard structures, respectively.     

Neotropical Monogenoidea. 40. Protorhinoxenus prochilodi gen. n., sp. n. (Monogenoidea: Ancyrocephalinae), parasite of prochilodus lineatus (Characiformes: Prochilodontidae) from south Brazil

The monotypic Protorhinoxenus gen. n. is proposed to accommodate a species with the following characteristics: 1) tubular sclerotised vagina, 2) vaginal pore dextrolateral, 3) ventral and dorsal anchors with undifferentiated elongate shaft and base (representing approximately 2/3 of the length of anchor), and 4) superficial and deep roots of ventral and dorsal anchors lacking. Protorhinoxenus prochilodi sp. n. is described from the gills of Prochilodus lineatus (Valenciennes) of the Represa Capivari-Cachoeira, Municipality of Campina Grande do Sul, metropolitan area of Curitiba, Paraná. Specimens of other probable new species of Protorhinoxenus are reported from Prochilodus lineatus of the Rio Paranapanema, Municipality of Salto Grande, S?o Paulo; Hoplias spp. of the Rio Dois de Fevereiro, Municipality of Antonina, Paraná, and the Rio Piraquara, metropolitan area of Curitiba, Parana; Leporinus elongatus Valenciennes of the Rio Tibagi, Municipality of Jataizinho, Parana; and Schizodon fasciatum Agassiz of the Rio Solim?es, island of Marchantaria, near Manaus, Amazonas. Protorhinoxenus appears to be a sister group of Rhinoxenus Kritsky, Boeger et Thatcher, 1988 based on the following apparent synapomorphies: 1) ventral and dorsal anchors lacking superficial and deep roots, 2) ventral and dorsal anchors with elongate shaft, and 3) male copulatory organ with counterclockwise rings.     

Acanthocolpidae (Digenea) of marine fishes off New Caledonia, with the descriptions of two new species

The following acanthocolpid species are reported from New Caledonia. Acaenodera nautili sp. n. from Conger cinereus Rüppel differs from other Acaenodera species in details of the body-spination, the sucker-ratio and the bipartite seminal vesicle; Stephanostomum murielae sp. n. from Carangoides hedlandensis (Whitley) differs from most species of Stephanostomum in the average of 36 circum-oral spines, the circum-oral spine rows with a ventral hiatus and the anterior extent of the vitellarium being > 10% of the hindbody length from ventral sucker. The species is distinguished from the three other species with these characters in a detailed review. The other species reported are: Stephanostomum aaravi Bray et Cribb, 2003 from Lethrinus miniatus and L. rubrioperculatus; Stephanostomum ditrematis (Yamaguti, 1939) from Gnathanodon speciosus; Stephanostomum japonocasum Durio et Manter, 1969 from Cephalopholis urodeta, Epinephelus areolatus, E. chlorostigma, E. maculatus, E. retouti, Lethrinus miniatus and Variola louti; Stephanostomum uku Yamaguti, 1970 and Pleorchis uku Yamaguti, 1970 from Aprion virescens.     

A new species of Acanthochondria (Copepoda: Chondracanthidae) parasitizing the flounder Xystreurys rasile (Pleuronectiformes: Paralichthyidae) from Argentina

A new copepod species, Acanthochondria sagitta sp. n., is described based on specimens collected from the flounder Xystreurys rasile (Jordan) (Pleuronectiformes, Paralichthyidae), caught in the coastal waters off Necochea, Buenos Aires Province, Argentina. The new species differs from its congeners by the following combination of characters: presence of three pairs of cephalic outgrowths; the triangular shape of the trunk with diverging postero-lateral processes; leg 2 of an intermediate shape between Types C and D, which projects laterally from the trunk, and Type B-V antennule bearing two proximal processes (one ventral and one dorsal) on the swollen basal portion.     

Two new species of Myliocotyle (Monogenea: Monocotylidae) from the gills of Aetomylaeus maculatus and A. nichofii (Elasmobranchii: Myliobatidae) from Sarawak, Borneo, Malaysia

Myliocotyle borneoensis sp. n. and M. multicrista sp. n. (Monocotylidae: Heterocotylinae) are described from the gills of the mottled eagle ray, Aetomylaeus maculatus (Gray), and the banded eagle ray A. nichofii (Bloch et Schneider) (Myliobatidae), respectively, collected from the northern coast of Malaysian Borneo. These are the first monogeneans to be described on elasmobranchs from Borneo. The formerly monotypic Myliocotyle (for M. pteromylaei) was distinguished from other monocotylids by the distribution and morphology of the eight sclerotised dorsal haptoral accessory structures and the morphology of the male copulatory organ. However, we have determined that M. pteromylaei has ten structures on the dorsal surface of the haptor. Myliocotyle borneoensis is distinguished from M. pteromylaei by the morphology of the male copulatory organ and its accessory piece. Myliocotyle multicrista has 12 sclerotised dorsal haptoral accessory structures and a male copulatory organ with two accessory pieces. Additional sclerotised ridges across the ventral surfaces of each loculus (except the posterior-most pair) are also present in M. multicrista. The diagnosis for Myliocotyle is revised given our discovery of additional dorsal haptoral accessory structures in the type species and to accommodate other new characters of the two new species. Anterior secretions of Myliocotyle are discussed.     

Three new species of Echinobothrium (Cestoda: Diphyllidea) from Indo-Pacific stingrays of the genus Pastinachus (Rajiformes: Dasyatidae)

Three new species of diphyllidean cestodes are described from stingrays of the genus Pastinachus from the Indian and Pacific Oceans. All three new species differ from all but 10 of the 36 valid species of Echinobothrium van Beneden, 1849 in that they bear lateral hooklets arranged in a continuous band across each lateral surface of the rostellum joining the groups of dorsal and ventral apical hooks, rather than arranged in distinct dorsal and ventral groups, on each side of the apical hooks. Echinobothrium nataliae sp. n. ex Pastinachus solocirostris off Borneo differs from other relatives in the following combination of characters: number of spines in each column on the cephalic peduncle, number of lateral hooklets and number of apical hooks. Echinobothrium reginae sp. n. ex Pastinachus cf. sephen off Madagascar differs from all congeners in the following combination of characters: number of hooklets and number of spines on the cephalic peduncle. Echinobothrium vojtai sp. n. from an undescribed species of Pastinachus off Borneo differs from its congeners in the following combination of characters: number of hooklets, number of apical hooks and number of spines in each column on the cephalic peduncle. The hook formula was modified to accommodate species with lateral hooklets arranged in a continuous band as follows: {(LH) AH(A)/AH(B)}, where (LH) is the total number of lateral hooklets in a band. A table of all nominal species of Echinobothrium, showing their taxonomic status, type host and locality, number of peduncle spines in a column and hook formula, is presented. Macrobothridium djeddensis and Macrobothridium sinensis are transferred to Echinobothrium. In addition, Echinobothrium deeghai is considered as a species inquirenda.     

Observations on cucullanid nematodes from freshwater fishes in Mexico, including Dichelyne mexicanus sp. n

A new cucullanid nematode, Dichelyne mexicanus sp. n., is described from the intestine of three species of fishes, Agonostomus monticola (Bancroft) (Mugilidae, Perciformes) (type host), Ictalurus balsanus (Jordan et Snyder) (Ictaluridae, Siluriformes) and Cichlasoma beani (Jordan) (Cichlidae, Perciformes), from three rivers (La Maquina River, Veracruz; Chontalcoatlán River, Guerrero and Santiago River, Nayarit) in central Mexico. This species is characterised by the absence of a ventral sucker in the male (subgenus Dichelyne) and it differs from its congeners mainly in possessing very unequal and dissimilar spicules (left 0.465-0.768 mm and right 293-548 mm long), an asymmetrical gubernaculum, and two intestinal caeca. Another cucullanid nematode, Cucullanus caballeroi Petter, 1977, is reported from Dormitator maculatus (Bloch) (Eleotridae, Perciformes) from the La Palma and La Maquina Rivers and Balzapote stream, Veracruz, being briefly described and illustrated; this represents a new host record. Findings of D. mexicanus and C. caballeroi represent a new record of cucullanid nematodes from fishes in Mexican fresh waters.     

Ultrastructure of the digestive tract of Echinostoma revolutum cercaria

The digestive tract of a fully formed free-swimming cercaria of Echinostoma revolutum (Froelich, 1802) Dietz, 1909 was studied by electron microscopy. The oral sucker and pharynx are covered by a tegument. The oesophagus and the caeca are not luminized. They are packed with giant epithelial cells with electron-dense granules of irregular shape, rough endoplasmic reticulum and its cisterns, and Golgi apparatus. The tegument of the oral sucker cavity contains numerous uniciliate receptors.     

Chaetotaxy applied to Norwegian Gyrodactylus salaris Malmberg, 1957 (Monogenea) clades and related species from salmonids

Gyrodactylus salaris Malmberg, 1957 is a major pathogen of wild Salmo salar L. parr populations in Norway, and its delimitation from non-pathogenic species is important. The present study was undertaken to test the power of chaetotaxy to differentiate between three populations belonging to both the same and different clades (as stated by mtDNA) of G. salaris, in addition to three different species of gyrodactylids (G. salaris, G. thymalli and G. caledoniensis). The gyrodactylids were processed for chaetotaxy in situ and a maximum of 50 specimens per collection site were used to construct a generalised map over the sensilla. The sensilla were found in all populations to be symmetrically distributed around the median longitudinal axis, according to a formula of 7 dorsal (34 sensilla) and 8 ventral (44 sensilla) clusters on each side of the median line. The three Norwegian populations of G. salaris were found identical, as were the population of G. thymalli. The specimens of G. caledoniensis from Scotland, however, were found to differ from the Norwegian species G. salaris and G. thymalli by the position of one sensillum in two of the clusters. A comparison of the sensillum pattern of laboratory maintained G. salaris (River Lierelva) with results obtained ten years earlier, questions the temporal stability of the chaetotaxy pattern. The present results indicate that chaetotaxy can be used to discriminate between certain Gyrodactylus spp. but not generally.     

Gyrodactylus bohemicus sp. n. (Monogenea: Gyrodactylidae) from Oncorhynchus mykiss (Walbaum) and Salvelinus fontinalis (Mitchill) (Clupeiformes: Salmonidae) in Czechoslovakia.

Gyrodactylus bohemicus sp. n (Gyrodactylidae: Monogenea) is described from the fins, skin and gill filaments of Oncorhynchus mykiss (Walbaum) and Salvelinus fontinalis (Mitchill) (Clupeiformes: Salmonidae) from a trout farm in Czechoslovakia. G. bohemicus sp. n. is most closely related to G. thymalli Zitnan, 1960 and G. magnus Konovalov, 1967 in the shape of the anchors, the ventral and the dorsal bar, but can be distinguished from both these species by the shape of the marginal hook proper.     

Morphological and molecular study of Microphallus primas (Digenea: Microphallidae) metacercaria, infecting the shore crab Carcinus maenas from northern Portugal

The present study describes the anatomy and surface topography of the metacercaria of Microphallusprimas (J?gerski?ld, 1909) infecting the shore crab Carcinus maenas (L.) in Aveiro estuary, northern Portugal. The metacercaria species identification resulted from the combined use of morphological and molecular data, particularly the 28S rDNA gene. The metacercariae encysted preferentially in the host's hepatopancreas and also in the gonads. Isolated cysts were present in two distinct forms, spherical and oval, and were shown to be the identical species by the internal transcribed spacer 1 (ITS1) sequence. Chemically excysted metacercariae were studied by light (LM) and scanning electron microscopy (SEM). Their specific characteristics observed include the particular aspect of the vesiculo-prostatic pouch surrounded by a very thin membrane, the presence of a prominent muscular papilla, and an obvious metraterm. The dorsal and ventral tegumental surfaces of the metacercaria were densely packed with similar squamous spines, which decreased in number and size towards the hindbody. The edges of the posterior and ventral face of the body were coated with numerous microvilli, whose function remains unknown. In order to identify the species of metacercariae, we compared a 28S partial rDNA sequence of the two forms of cysts with the same 28S partial region of M. primas available in GenBank. With this comparison, we determined that the sequences had a 100% similarity and therefore belonged to the same species, i.e., M. primas.