Molecular characteristics of Camallanus spp. (Spirurida : Camallanidae) in fishes from China based on its rDNA sequences

In the,paper, we explored the intra- and interspecific evolutionary variation among species of Camallanus collected from different fish species in various regions of China. We determined the internal transcribed spacers of ribosomal DNA (ITS rDNA) sequences of these nematodes. The divergence (uncorrected p-distance) of ITS 1, ITS2, and ITS rDNA data sets confirmed 2 valid species of Camallanus in China, i.e., C. cotti and C. hypophthalmichthys. The 2 species were distinguished not only by their different morphologies and host ranges but also by a letranucleotide microsatellite (TTGC)n present in the ITS I region of C cotti. Phylogenetic analyses of the nematodes disclosed 2 main clades, corresponding to different individuals of C cotti and C. hypophthalmichthys from different fish species in various geographical locations, although the interior nodes of each clade received poor support.

Variation patterns of the mitochondrial 16S rRNA gene with secondary structure constraints and their application to phylogeny of cyprinine fishes (Teleostei : Cypriniformes)

The mitochondrial 16S ribosomal RNA (rRNA) gene sequences from 93 cyprinid fishes were examined to reconstruct the phylogenetic relationships within the diverse and economically important subfamily Cyprininae. Within the subfamily a biased nucleotide composition (A > T, C > G) was observed in the loop regions of the gene, and in stem regions apparent selective pressures of base pairing showed a bias in favor of G over C and T over A. The bias may be associated with transition-transversion bias. Rates of nucleotide substitution were lower in stems than in loops. Analysis of compensatory substitutions across these taxa demonstrates 68% covariation in the gene and a logical weighting factor to account for dependence in mutations for phylogenetic inference should be 0.66. Comparisons of varied stem-loop weighting schemes indicate that the down-weightings for stem regions could improve the phylogenetic analysis and the degree of non-independence of stem substitutions was not as important as expected. Bayesian inference under four models of nucleotide substitution indicated that likelihood-based phylogenetic analyses were more effective in improving the phylogenetic performance than was weighted parsimony analysis. In Bayesian analyses, the resolution of phylogenies under the 16-state models for paired regions, incorporating GTR + G + I models for unpaired regions was better than those under other models. The subfamily Cyprininae was resolved as a monophyletic group, as well as tribe Labein and several genera. However, the monophyly of the currently recognized tribes, such as Schizothoracin, Barbin, Cyprinion + Onychostoma lineages, and some genera was rejected. Furthermore, comparisons of the parsimony and Bayesian analyses and results of variable length bootstrap analysis indicates that the mitochondrial 16S rRNA gene should contain important character variation to recover well-supported phylogeny of cyprinid taxa whose divergences occurred within the recent 8 MY, but could not provide resolution power for deep phylogenies spanning 10-19 MYA. (c) 2008 Published by Elsevier Inc.

Threatened fishes of the world: Tanichthys albonubes Lin 1932 (Cyprinidae)

The white cloud mountain minnow Tanichthys albonubes Lin is an endemic species to southern China and the genus has two species, Tanichthys albonubes Lin and Tanichthys micagemmae Freyhof et Herder. The distribution range of T. albonubes Lin and T. micagemmae is very narrow and only found in the mountain brooks of Baiyunshan Mountain (White Cloud Mountain), Huaxian Country and the vicinity of Guangzhou in Guangdong Province and Halong, Quang Ninh Province, Vietnam respectively. The wild populations of this fish had already been on the verge of extinction when Shu-Yan Lin first discovered it in 1932 at the Baiyunshan Mountain. It was believed to be extinct in the wild because there were no reports of this fish in the wild since 1980. In September 2003, a small and isolated population of the fish was discovered in a mountain puddle in the north vicinity of Guangzhou. Additional studies are needed to determine the survival and propagation of the released fish. The protection of their natural habitat should be implemented.

Study of Apiosoma piscicola (Blanchard 1885) occurring on fry of freshwater fishes in Hongze, China with consideration of the genus Apiosoma

Apiosoma piscicola (Blanchard 1885) was reported from fry of Carassius auratus (Var. pengze) and Ctenopharyngodon idella during parasite surveys in May 2005 and June 2006 at Hongze Lake Fish Hatchery, Jiangsu province, China. Twelve morphometric parameters were used to describe this peritrich in detail in the present study and comparisons were made with other reports. Its synonyms, Glossatella cylindriformis (Chen 1955) and Apiosoma magna (Banina 1968), were clarified based on reliable data. A. piscicola was still considered somewhat host-specific by us, especially to cyprinids, although it shows a quite wide limit of host variability. The telotroch was also observed, and its structures were described herein. Besides, the difficulties of the generic taxonomy were discussed and some suggestions were given.

A new species of Allocreadium (Trematoda : Allocreadiidae) from freshwater fishes in the Danjiangkou Reservoir in China

A new species of Allocreadium, Allocreadium danjiangensis n. sp., is described from the intestine of several species of freshwater fish, including Abbottina rivularis (Basilewsky, 1855), Sarcocheilichthys nigripinnis nigripinns (Gunther, 1873), Gnathopogon argentatus (Sauvage et Dabry 1874), Opsariichthys uncirostris bidens (Gunther, 1873), and Erythroculter mongolicus mongolicus (Basilewsky, 1855) (Cyprinidae) from the Danjiangkou Reservoir in central China. The main morphological characters of the new species are as follows: vitelline follicles numerous, extending from the level of acetabulum to posterior extremity, distributed over both sides around the ceca; cirrus sac relatively large, developed, lying obliquely anterior to the acetabulum, extending from the level of the intestinal bifurcation to the central level of acetabulum, and overlapping left or right cecal; and ovary much smaller than testes, generally close to or even overlapping the anterior border of anterior testis. Observation by scanning electron microscopy shows only 2 kinds of tegumental formations, i.e., papillae and tubercles, instead of 3 types of tegumental formations, i.e., papillae, bosses, and minute sensor receptors observed on other species of the Allocreadiidae. The tegumental striations of the present species vary on the different parts of the body. In addition, a new structure, identified as the "groove" with a tonguelike tubercle, was observed on the inner wall of acetabulum.

Description of a new genus and two new species of labeonine fishes from South China (Teleostei : Cyprinidae)

A new genus and two new species are described from the Pearl River drainage in Guangxi Province, South China. Hongshuia, new genus, can be distinguished from all other Asian genera of the Labeonini by having a lower lip with its median lobe modified into a round, fleshy plate peripherally greatly protruded so as to form a ring-like fold that is posteromedially continuous with the mental region, and centrally sunken so as to form a round, flat, fleshy pad. This genus is distinct from all other Asian labeonine genera of the Garrina except for one newly described species of Parasinilabeo ( P. longibarbus), Pseudocrossocheilus, and Sinocrossocheilus, in the presence of well-developed maxillary barbels. Hongshuia differs from the above three genera in the lower lip morphology, and further from both Pseudocrossocheilus and Qianlabeo in the number of pharyngeal tooth rows and from Sinocrossocheilus in the colour pattern. Two new species, H. banmo and H. paoli, differ in the distribution density and degree of development of papillae on the rostral fold, depth of indentations on the distal edge of the rostral fold, presence or absence of papillae on the lower lip, size and shape of tubercles on the tip of the snout and anterior portion of the lachrymal, length, position and colour pattern of the dorsal fin, and snout length.

Morphological description of two bucephalid trematodes collected from freshwater fishes in the Uji River, Kyoto, Japan

The morphology of two species of bucephalids (Bucephalidae; Digenea; Trematoda), which since 1999 has caused a fish disease at the Uji River, Kyoto Prefecture, Japan, is described. Parabucephalopsis parasiluri Wang, 1985 was first recorded in the Uji River in 2000, and Prosorhynchoides ozakii (Nagaty, 1937) in 2005. The definitive host of both species is the Lake Biwa catfish (Silurus biwaensis), and the second intermediate hosts include many fish species from several families. P. parasiluri is an introduced parasite that invaded with its first intermediate host, golden mussels (Limnoperna fortunei), from the Asian continent. P ozakii may also be an introduced species, although its first intermediate host has not been identified. (C) 2007 Elsevier Ireland Ltd. All rights reserved.

In situ studies on physiological and biochemical responses of four fishes with different trophic levels to toxic cyanobacterial blooms in a large Chinese lake

Physiological and biochemical responses of four fishes with different trophic levels to toxic cyanobacterial blooms were studied in a large net cage in Meiliang Bay, a hypereutrophic region of Lake Taihu. We sampled four fishes: the phytoplanktivorous Hypophthalmichthys molitrix and Aristichthys nobilis, the omnivorous Carassius auratus, and the carnivorous Culter ilishaeformis. Alterations of the antioxidant (GSH) and the major antioxidant enzymes (CAT, SOD, GPx, GST) in livers were monitored monthly, and the ultrastructures of livers were compared between the bloom and post-bloom periods. During the cyanobacterial blooms, the phytoplanktivorous fishes displayed only slight ultrastructural changes in liver, while the carnivorous fish presented the most serious injury as swollen endomembrane system and morphologically altered nuclei in hepatocytes. Biochemically, the phytoplanktivorous fishes possessed higher basal GSH concentrations and better correlations between the major antioxidant enzymes in liver, which might be responsible for their powerful resistance to MCs. This article provided physiological and toxicological evidences for the possible succession of fish communities following occurrence of toxic cyanobacterial blooms and also for the applicability of using phytoplanktivorous fish to counteract toxic cyanobacterial blooms in natural waters. (C) 2007 Elsevier Ltd. All rights reserved.

Morphological and genetic differences of Trypanosoma in some Chinese freshwater fishes: difficulties of species identification

Blood smears and purified trypanosome from freshwater fishes yellow catfish (Pseudobagras fulvidraco) and common carp (Cyprinus carpio) captured from Niushan Lake, Hubei Province were examined to determine whether all of their trypanosomes were Trypanosoma pseudobagri, a species of supposed host specificity and widespread existence across China. Trypanosomes occurred in 16/16 blood smears, and morphometric character analysis of trypanosomes from these smears showed that there were three morphospecies, Trypanosoma sp Carpio, T. sp Pseudobagri, and T. sp. 18S rDNA sequences of trypanosomes from 16 samples revealed three genetic groups among these fish trypanosomes. Group 1 was from C. carpio containing T. sp Carpio; groups 2 and 3 were from P. fulvidraco containing T. sp Pseudobagri and T. sp, respectively. The high similarity of morphometric characters and 18S rDNA sequences showed that T. sp Carpio and T. siniperca probably were the same species. T. sp Pseudobagri was the first occurrence in China. Sequence comparison showed that T. sp Pseudobagri sequence was most similar to that of clone Marv, whereas T. sp sequence differ from those of T. sp Carpio and T. sp Pseudobagri by 5.4 and 5.8%, respectively, and tentatively identified as T. pseudobagri. It was concluded that three species of trypanosomes, at least three genotypes occur in Niushan Lake fishes, and P. fulvidraco in this region appear to contain both types, although the identification of T. pseudobagri remains a problem.

Molecular phylogeny and biogeography of the highly specialized grade schizothoracine fishes (Teleostei : Cyprinidae) inferred from cytochrome b sequences

We recovered the phylogenetic relationships among 23 species and subspecies of the highly specialized grade schizothoracine fishes distributing at 36 geographical sites in the Tibetan Plateau and its Surrounding regions by analyzing sequences of cytochrome b genes. Furthermore, we estimated the possible divergent times among lineages based on a historical geological isolation event in the Tibetan Plateau. The molecular data revealed that the highly specialized grade schizothoracine fishes were not a monophyletic group, but were the same as genera Gymnocypris and Schizogypsis. Our results indicated that the molecular phylogenetic relationships apparently reflected their geographical and historical associations with drainages, namely species from the same and adjacent drainages clustered together and had close relationships. The divergence times of different lineages were well consistent with the rapid uplift phases of the Tibetan Plateau in the late Cenozoic, suggesting that the origin and evolution of schizothoracine fishes were strongly influenced by environment changes resulting from the upheaval of the Tibetan Plateau.

Identification of the Angel-related elements in cyprinid fishes and their phylogenetic implications

Angel-related element belongs to the family of miniature inverted-repeat transposable elements (MITEs). In this paper we report the identification of an Angel-related element in the series Leuciscini of cyprinid fishes, which is located in the second intron of the growth hormone (GH) gene. We have also found that this element is absent in orthologous locus in the series Barbini of cyprinid fishes, that provides new evidence for the monophyly of the series Leuciscini. The insertion of Angel-related element into the GH gene might take place in the common ancestor of the series Leuciscini after its divergence from the series Barbini. The high sequence divergence and relatively broad species distribution of Angel-related elements implies that they might be ancient transposons which appeared about 26 million years ago.

The co-evolutionary relationship between bitterling fishes and freshwater mussels: insights from interspecific comparisons

Hypothesis: In parasites that use hosts for offspring development, adults may base oviposition decisions on a range of host traits related either to host quality or the co-evolutionary relationship between parasite and host. We examined whether host quality or co-evolutionary dynamics drive the use of hosts in the bitterling-mussel relationship. Organisms: Six species of bitterling fish (Acheilognathinae) and eight species of freshwater mussels (Unionidae, Corbiculidae) that are used by bitterling for oviposition. Site of experiments: Experimental tanks in Wuhan, China, at the site of the natural distribution of the studied species. Methods: Three experiments that controlled for host accessibility and interspecific interactions were conducted to identify host preferences among bitterling fishes and their mussel hosts. We started with a broad interspecific comparison. We then tested bitterling behavioural choices, their temporal stability, and mussel host ejection behaviour of the eggs of generalist and specialist bitterling species. Finally, we measured host mussel quality based on respiration rate and used published studies on mussel gill structure to infer mussel suitability as hosts for bitterling eggs. Results: We found significant interspecific differences among bitterling species in their use of mussel hosts. Bitterling species varied in their level of host specificity and identity of preferred hosts. Host preferences were flexible even among apparently specialized species and fishes switched their preferences adaptively when the quality of individuals of preferred host species declined. Mussels varied considerably in their response to oviposition through egg ejections. Host preference by a generalist bitterling species correlated positively with host quality measured as the efficiency of the mussel gills to extract oxygen from inhaled water. Host ability to eject bitterling eggs correlated positively with their relative respiration rate, probably due to a higher velocity of water circulating in the mussel gill chamber.

Community structure of small fishes in a shallow macrophytic lake (Niushan Lake) along the middle reach of the Yangtze River, China

This study describes the current status of the small fish community in Niushan Lake in China, and examines the spatial and seasonal variations of the community in relation to key environmental factors. Based on macrophyte cover conditions, the lake was divided into three major habitat types: (1) Potamogeton maackianus habitat, (2) Potamogeton maackianus and Myriophyllum spicatum habitat, and (3) uncovered or less-covered habitat. Fish were sampled quantitatively in the three habitat types by block nets seasonally from September 2002 to August 2003. A total of 10 469 individuals from 27 fish species were caught, among which 20 species were considered as small fishes. Rhodeus ocellatus, Paracheilognathus imberbis, Pseudorasbora parva, Micropercops swinhonis and Cultrichthys erythropterus were recognized as dominant small fishes according to their abundance and occurrence. It was noted that (1) small fishes predominated the total number of fish species in the lake, which reflected to some degree the size diminution phenomenon of fish resources; (2) many small fishes had plant detritus as their food item, which was consistent with the abundance of macrophyte detritus in the lake and implied the importance of detritus in supporting small fish secondary production. Canonical correspondence analysis suggested that the spatial distributions of most small fishes were associated with complex macrophyte cover conditions. Macrophyte biomass was positively correlated with species richness, diversity index and the catch per unit of effort (CPUE) of the fish community. Water depth had no significant effects on species diversity and distribution of the small fishes. Correspondence analysis revealed a higher occurrence of the small fishes and higher abundance of individuals in summer and autumn. Seasonal length-frequency distributions of several species indicated that more larval and juvenile individuals appeared in spring and summer. This study provides some baseline information which will be essential to long-term monitoring of small fish communities in the Yangtze lakes.

The impact of planktivorous fishes on microcystin concentrations in Meiliang Bay, Lake Taihu, China

In an eight-month enclosure experiment in Meiliang Bay of Lake Taihu, a shallow subtropical lake in China, silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis) collectively reduced cyanobacterial biomass. Microcystin concentration was six times higher in the 0.35 km(2) control enclosure (without fish) than in two similar-sized enclosures that had been stocked with both carp species. Furthermore, toxic Microcystis spp. increased microcystin production when exposed to silver carp and bighead carp.