Seasonal variations in a population of the monogenean Ancyrocephalus mogurndae Gussev, 1955 were investigated on gills of cage-cultured mandarin fish, Siniperca chuatsi (Basilewsky), during the period from April 1994 to April 1995. The abundance of A. mogurndae peaked in late spring and summer. Prevalence was high (75-100 %) throughout the study period, and did not vary significantly between months. More than 50 % of all monogeneans were found on the first and second gill arches, except one occasion when the fourth gill arch had the majority in April 1995. The niche breadths were significantly correlated with the population abundance. A coexistent parasitic myxosporean, Henneguya weishanensis Hu, 1965, on the gills of the fish was found to have little influence on the gill-arch preference of the monogenean, although the monogenean abundance was higher in those fish infected with the myxosporean.
In recent years, an emerging dermocystidiosis caused by Dermocystidium anguillae Spangenberg, 1975 has been found to pose a threat to the culture of American eel, Anguilla rostrata (Lesueur), as well as Chinese perch, Siniperca chuatsi (Basilewsky), in China. Dermocystidium anguillae was originally described from European eel, Anguilla anguilla (Linnaeus), and it is thus important to identify the possible source of this pathogen. In the present study, we compared D. anguillae from European eels cultured in China with those from American eels. Molecular analysis showed that the SSU rDNA of D. anguillae infecting European eels was identical to that of D. anguillae infecting American eels, suggesting their conspecificity. To investigate the source of D. anguillae causing dermocystidiosis in American eels cultured in China, a specific PCR assay for the detection of D. anguillae was developed with high sensitivity (10-6 ng/µl of D. anguillae genomic DNA). Using the present molecular detection method, the water and sediment of culture ponds, fish feed and American eel elvers imported from America were screened for the presence of D. anguillae. No amplicons were detected from the water, sediment and fish feed samples. However, positive amplicons were found in American eel elvers, indicating that D. anguillae has been introduced from American eel elvers to China. It is suggested that American eel elvers imported from America should be examined for the presence of D. anguillae before their exportation abroad to prevent the spread of this pathogen.
By examining iron contents, it is demonstrated that the monogenean Ancyrocephalus mogurndae (Yamaguli, 1940) feeds on the blood of its host, the mandarin fish Siniperca chuatsi (Basilcwsky), The iron content and then the quantity of blood necessary to produce this amount of iron are found different in young and fully-matured worms. Young worms contain higher levels of iron and estimated amount of blood. It is suggested that/1, mogurndae may start to feed on host blood as attached on gills, and the amount of blood ingested by young worms may vary from 0.01 to 1.00 μΙ before reproduction. The difference between young and fully-malurcd worms may be accounted for by the elimination of haematin and change of food composition in matured worms and may also be affected by reproduction. Experimental infections of the monogenean may provide supportive information for explaining the difference, and further studies should also examine the effect of immune components in host blood or mucus on the intestines of the parasite.
Morphological characteristics of the acanthocephalan Polymorphus minutus (Goeze, 1782), which was collected from the duck Anas platyrhynchos Linnaeus in the Czech Republic, are described. The mitochondrial (mt) genome of P. minutus was sequenced, with a total length of 14,149 bp, comprising 36 genes including 12 protein coding genes (PCGs), 22 transfer RNA (tRNA) genes and two ribosomal RNA genes (rrnL and rrnS). This genome is similar to the mt genomes of other syndermatan species. All these genes were encoded on the same DNA strand and in the same orientation. The overall nucleotide composition of the P. minutus mt genome was 38.2% T, 27.3% G, 26.2% A, and 8.3% C. The amino acid sequences of 12 PCGs for mt genomes of 28 platyzoans, including P. minutus, were used for phylogenetic analysis, and the resulting topology recovers P. minutus as sister to Southwellina hispida (Van Cleave, 1925), and the two taxa form a sister clade to Centrorhynchus aluconis (Müller, 1780) and Plagiorhynchus transversus (Rudolphi, 1819), which are all species in the Palaeacanthocephala, thus supporting the monophyly of this class.
A new highly pathogenic muscle-infecting species of the genus Myxobolus Bütschli, 1882 is described from the Prussian carp, Carassius gibelio (Bloch, 1782) using spore morphology and SSU rDNA sequence data. Phylogenetic analyses elucidated relationship of the newly described Myxobolus lentisuturalis to other Myxobolus species and supported its position of an independent species.
During a survey on the myxosporean fauna of gibel carp Carassius auratus gibelio (Bloch) in China, a species of Myxobolus Bütschli, 1882 that did not conform to any known species was found. The species is characterised by the presence of round to ellipsoidal plasmodia of 2.6-4.0 mm in diameter in the palate of host. Mature spores are obovate in frontal view and lemon-shaped in lateral view, with the following range, mean and standard deviation of dimensions: 10.8-12.8 µm (11.7 ± 0.4 µm) long, 8.2-9.9 µm (8.9 ± 0.4 µm) wide and 6.0-7.5 µm (6.8 ± 0.3 µm) thick. Two polar capsules are pyriform, 4.0-5.5 µm (4.8 ± 0.3 µm) long by 2.9-3.6 µm (3.0 ± 0.2 µm) wide. Polar filaments are coiled, with 5 to 6 turns. A small proportion of spores possesses a short caudal process. Scanning electron microscopy revealed discoid spores with a low sutural ridge and middle bulge. The small subunit ribosomal DNA sequence of this species did not match any available sequences in GenBank. Phylogenetically, this species is sister to M. nielii (Nie et Li, 1973) and M. hearti Chen, 1998 in a Henneguya-Myxobolus clade with robust support. Given the morphological and molecular differences between this species and other Myxobolus species, we propose the name Myxobolus oralis sp. n. for this parasite from gibel carp.
The original description of Myxobolus longisporus Nie et Li, 1992, the species infecting gills of Cyprinus carpio haematopterus L., is supplemented with new data on the spore morphology and pathogenicity. Spores are elongate pyriform with pointed anterior end, 15.7 (15.5-16.5) µm long, 6.7 (6-8) µm wide and 5.5 µm thick. Sutural ridge is straight and narrow. Mucus envelope is lacking. Two equal-sized elongate pyriform polar capsules are 8.5 µm long and 2.5 µm wide with convergent long axes. Polar filament coiled perpendicularly to the long axis of the capsule makes 9 (8-10) turns. Posterior end of polar capsules exceeds mid-spore by 15-20%. Cyst-like plasmodia are localised in the gill secondary lamellae. The infection is described in adult big host specimens. Gross lesions manifested as dark red colouration of gill tissues were restricted to the ventral part of the first gill arches. Remarkable site specificity (apical part of secondary lamellae) was observed in the course of development of microscopic lesions. M. longisporus is characterised also on the molecular level using sequences of SSU rRNA gene. Phylogenetic analysis based on these sequences has allowed clearer phylogenetic relationships to be established with other species of the genus Myxobolus sequenced to date.
Two little-known nematode species of the genus Spinitectus Fourment, 1883, S. petrowi Belous, 1965 (prevalence 25%, intensity 1-8) and S. gigi Fujita, 1927 (prevalence 10%, intensity 2-3), were collected from the gastrointestinal tract of the yellow catfish, Pelteobagrus fulvidraco (Richardson), from Liangzihu Lake, Hubei Province, central China, in September of 2002. The light and scanning electron microscopical examination of this material, supplemented by a few museum specimens of S. gigi collected from the catfish Clarias fuscus (Lacépède) in southern China, made it possible to study in detail the morphology of these parasite species and to redescribe them. The first species, whose correct name is S. petrowi Belous, 1965, exhibits some morphological features (e.g., unusually short vestibule, shape of pseudolabia and of the left spicule) not found in most other congeners; a unique feature is the presence of peculiar pairs of transversely oriented peg-like cuticular spines with rounded ends on the ventral surface of the female tail. Spinitectus gigi was found to have 28-31 cuticular spines in the first ring, relatively long distances between the 2nd-7th rings of spines, and anterior rings divided into 2 sectors; the excretory pore is located at the level of the 4th ring of cuticular spines; males posses 4 pairs of preanal- and 6 pairs of postanal caudal papillae and a pair of small phasmids. Spinitectus bagri Wang, Wu et Yu, 1993 and S. wulingensis Yu et Wang, 1997 are considered junior synonyms of S. petrowi, whereas S. clariasi Ky, 1971, S. ophicephali Ky, 1971 and S. yuanjiangensis Wang, Wu et Yu, 1997 are regarded to be junior synonyms of S. gigi. Spinitectus petrowi was not previously reported from China.
Re-examination of the syntypes of the capillariid nematode Neocapillaria phoxini Yu et Wang, 1994, the type species of Neocapillaria Yu et Wang, 1994, described from the intestine of the freshwater fish Phoxinus lagowskii variegatus Günther (Cyprinidae) from China, confirmed its morphological similarity with species of Freitascapillaria Moravec, 1987, to which it is transferred as Freitascapillaria phoxini (Yu et Wang, 1994) comb. n. Consequently, Neocapillaria Yu et Wang, 1994 (a homonym to Neocapillaria Moravec, 1987) and Sinocapillaria Moravec et Spratt, 1998 become junior synonyms of Freitascapillaria. Skrjabinocapillaria gigantea is transferred to Freitascapillaria as F. gigantea (Wang, 1984) comb. n.
The present paper comprises a systematic survey of nematodes based on helminthological examinations of 176 specimens of freshwater fishes, belonging to 22 species, from central China (mostly lakes in Hubei Province) collected during the autumn of 2001. The following six species were recorded: Procamallanus (Spirocamallanus) fulvidraconis Li, 1935, Camallanus cotti Fujita, 1927, Dentiphilometra monopteri Moravec et Wang, 2002, Pingus sinensis Hsü, 1933, Proleptinae gen. sp. larv., and Eustrongylides sp. larv. Data on their morphology, morphological variability, host range, prevalence, intensity and distribution are provided. SEM studies of P. fulvidraconis and larval Physalopterinae, used for the first time in these species, revealed some additional morphological details and made it possible to redescribe the former. In contrast to the existing description of P. fulvidraconis, this species was found to possess two spicules and a V-shaped gubernaculum with unequal arms (originally mistaken for the left spicule), as well as deirids, whose location can be considered an important taxonomic feature. Larvae of the Physalopterinae have not previously been reported from fishes in China. The finding of larval Eustrongylides in Paramisgurnus dabryanus represents a new host record. All but one nematode species from this zoogeographically interesting region are briefly described and illustrated.