Varicorhinus Barbatulus Research Articles

The effects of extenders, cryoprotectants and conditions in two-step cooling method on Varicorhinus barbatulus sperm

In this study, we developed an optimal cryopreservation procedure for Varicorhinus barbatulus sperm. To this end, we optimized (1) the types and dilution ratios of extenders; (2) types and final concentration of cryoprotectants; and (3) freezing conditions, including equilibration time, height above the surface of liquid nitrogen (LN), and the cooling times in the two-step cooling method. The optimum result was obtained when the sperm was diluted at a 1:9 ratio in D-17 with 10% methanol, equilibrated at 4 °C for 10 min, held at 7 cm above LN for 2 min, and finally stored in LN. After storage for 12 h in LN, the sperm was thawed in a water bath at 40 °C for 6s, the post-thaw sperm motility was 66.10 ± 7.12%, while the corresponding rate for fresh sperm was 87.08 ± 2.38%. Using computer-assisted sperm analysis, we found a significant decrease in the motility parameters of post-thaw sperm, especially the parameters related to velocity. To evaluate the effects of cryopreservation on the structural integrity of sperm, transmission electron microscopy and scanning electron microscopy were employed, which showed the defects in frozen sperm, including: abnormal heads, damaged plasma membranes, broken tails, and the disappearance of the mitochondrial internal crest. In addition, we determined the mitochondrial membrane potential to assess the functional integrity of frozen sperm. Our results showed a decrease in the mitochondrial function of frozen sperm. This procedure could be used alongside cryopreservation of V. barbatulus and supports its commercial-scale production and species conservation.

Metagonimus yokogawai: metacercariae survey in fishes and its development to adult worms in various rodents

A parasitological survey for Metagonimus yokogawai metacercariae was carried out by examining a total of 321 freshwater fish comprising of 7 species. Of the 321 fish samples examined, 182 (56.7%) were found to be infected with M. yokogawai metacercariae. The prevalence of M. yokogawai metacercariae in Opsariichthys pachycephalus was 93.4% (86/92), Zacco platypus 75.0% (30/40), Distoechodon turmirostris 61.3% (38/62), Varicorhinus barbatulus 56.5% (13/23), Hemibarbus labeo 33.3% (1/3), Acrossocheilus formosanus 15.9% (14/88), and 0% in Sinibrama macrops (0/13), respectively. This is the first record of M. yokogawai infection in Z. platypus, D. turmirostris, V. barbatulus, and H. labeo in Taiwan. The major site of predilection of the metacercariae in the fishes was in the scale, but some metacercariae were also observed in the flesh and fins. The M. yokogawai metacercariae were orally inoculated into mice, rat, gerbil, and golden hamster to study their infectivity and also to obtain the adult worms for taxonomic study. Worm recovery in hamsters was 75.3%, in mice was 70.0%, in rats was 23.3%, and in gerbils was 6.0%, respectively. Moreover, larger worms were recovered from the golden hamster. Golden hamster was thus found to be the most susceptible experimental rodent host for the infectivity study of Metagonimus. Besides M. yokogawai, metacercariae of Centrocestus formosanus was also observed in the fishes examined.

Habitat use by the Formosan landlocked salmon Oncorhynchus masou formosanus

The critically endangered Formosan landlocked salmon Oncorhynchus masou formo- sanus is one of the southernmost natural salmon populations in the world, which only occurs in Chichiawan Stream and its tributaries in the Wuling basin of subtropical Taiwan. We examined habi- tat uses by different size classes of the Formosan salmon and the sympatric shovelmouth minnow Varicorhinus barbatulus, and identified the relative importance of environmental variables, biotic components and seasonal effects in explaining the variance in the relative occurrences of fish at the catchment scale. After removing seasonal effects, 74.9% of the variation in the relative occurrence of fish was explained by the measured environmental variables and biotic components. Habitat uses by the Formosan salmon and shovelmouth minnow were distinct. The shovelmouth minnow occurred more frequently at sites with a high concentration of NH3-N and high proportions of gravel and rif- fles, while the Formosan salmon utilized sites at high elevations. Habitat uses by Formosan salmon of different size classes varied slightly. Juvenile and subadult salmon inhabited sites with lower temper- atures and current velocities, but adult salmon occurred more frequently with large-grain-sized sub- stratum. Our study showed that variations in the relative occurrence of fish in the Wuling basin were best explained by physicochemical parameters (38.8%), followed by substratum composition (11.4%). The variations exclusively explained by mesohabitat composition, seasonal effects, and biotic components were not significant. This conclusion has important consequences for local man- agers and conservationists.

Effects of the slow cooling during cryopreservation on the survival and morphology of Taiwan shoveljaw carp (Varicorhinus barbatulus) spermatozoa

Over the past decades, pollution, overfishing, and habitat degradation have driven the population size of Taiwan shoveljaw carp down markedly in Taiwan. Cryopreservation is a useful tool which could be used to maintain genetic resources to protect and preserve this endemic species. Four cryoprotectants (dimethyl sulphoxide (DMSO), dimethylacetamide (DMA), glycerol and methanol) and six freezing rates (0.5, 1, 2, 4, 8, 16 ◦ Cm in −1 ) were tested in order to develop an optimal controlled slow-freezing protocol for Taiwan shoveljaw carp spermatozoa. Samples were subsequently examined under the scanning electron microscope to reveal whether cryopreservation had affected their ul- trastructural morphology. The highest survival rate ( 50.1±2.0%) was observed with a freezing rate of 8 ◦ Cm in −1 in 1M DMSO, using SYBR-14 + PI staining. Fertility and hatching rate results using frozen-thawed spermatozoa (90.2± 2.2% and 22.3 ± 2.5%, respectively) were not significantly different from results with fresh spermatozoa. After cryopreser- vation, 21.0 ± 1.6% of frozen-thawed spermatozoa had mid-piece swelling and rupture of the head. Cryopreservation might, therefore, slightly affect Taiwan shoveljaw carp spermatozoa in terms of morphological change. However, these alterations could be compensated by using large enough numbers of normally functioning frozen-thawed spermato- zoa to achieve a standard equal to fresh spermatozoa. This is the first report of successful cryopreservation of Taiwan shoveljaw carp spermatozoa using a controlled slow-cooling method.

Model-based evaluations of spur dikes for fish habitat improvement: A case study of endemic species Varicorhinus barbatulus (Cyprinidae) and Hemimyzon formosanum (Homalopteridae) in Lanyang River, Taiwan

Abstract Two endemic species of fish in Taiwan, Varicorhinus barbatulus (Cyprinidae) and Hemimyzon formosanum (Homalopteridae), were considered to evaluate habitat areas. Numerical models, NETSTARS and TABS-2, were employed to simulate the hydraulic characteristics, i.e. water depth and flow velocity, in the presence as well as absence of constructed spur dikes. The results were used to calculate the weighted usable area (WUA) and percentage usable area (PUA); both of which are employed to evaluate the fish habitat area. The habitat area WUA of V. barbatulus and H. formosanum increases 404.8–442.4% and 38.4–435.8%, respectively after installing spur dikes. The maximum PUA for V. barbatulus was obtained when the dimensionless spur dike distance ( D / L ) fell between 3 and 3.4. However, the PUA for H. formosanum increased with D/L. This study also concluded that the fish habitat area was inversely proportional to the Froude number. The optimums of spur dikes numbers are 5–7 and 3–4 for V. barbatulus and H. formosanum , respectively. Regressive equations of PUA acquired from 240 cases indeed provided engineers with paradigms for fish habitat improvement. These two regressive equations are suitable for V. barbatulus and H. formosanum habitat evaluation and limited with the Froude number between 0.17 and 0.25.

Molecular cloning and tissue distribution of three estrogen receptors from the cyprinid fish Varicorhinus barbatulus

We present molecular cloning and tissue expression analysis of three estrogen receptor (ER) subtypes, vbERalpha, vbERbeta1 and vbERbeta2, from liver of the cyprinid fish Varicorhinus barbatulus through reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE). The sequence alignment and phylogenetic analysis reconfirmed the evolutionary relationship of V. barbatulus within the family Cypriniformes. Directional constraints for subtype-specific substitution of critical amino acids were observed in the E2 binding region. For amino acid substitution, vbERbeta exhibited a M517L change in the ligand-dependent transactivation region. The tissue distributions were investigated using RT-PCR with subtype-distinguishable primers. Both vbERalpha and vbERbeta1 were most highly expressed in liver, while vbERbeta2 was higher in intestine. Here we demonstrate that the identification and cloning of ER subtypes using PCR is feasible in wildlife in that the temporal and spatial observations are consistent with those from phylogeny analysis and crystal structural investigation by others.

Spatial and temporal variations of two cyprinids in a subtropical mountain reserve – a result of habitat disturbance

Abstract – We investigated the variations of population of two cyprinids, Varicorhinus alticorpus and Varicorhinus barbatulus, using long‐term survey data (1995–2004) in the subtropical island of Taiwan. Fish abundance data showed that at the mainstem stations, V. barbatulus which used to dominate in the higher altitude had declined significantly, while V. alticorpus that used to occupy only the lower altitude had spread upward. However, at the tributaries, trend of the populations of V. barbatulus were not significantly different over time, while populations of V. alticorpus were absent at higher altitude but began to increase at lower altitude. Environmental parameters revealed that sporadic high turbidity was observed at the mainstem stations, but not at the tributaries. Images taken before and after typhoon also showed habitat destruction by debris flow at the mainstem stations. As some models predicted that suitable fish habitats will shrink because of increasing water temperature due to global warming, we showed that fish distribution may be affected by habitat disturbance due to intensified storms sooner than the actual increase of water temperature.

Application of a yeast estrogen screen in non-biomarker species Varicorhinus barbatulus fish with two estrogen receptor subtypes to assess xenoestrogens

Xenoestrogens can interfere with normal estrogen signaling by competitively binding to the estrogen receptor (ER) and activating transcription of target genes. In this study, we cloned the estrogen receptor alpha ( vbERα) and beta 2 ( vbERβ2) genes from liver of the indigenous Taiwanese cyprinid fish Varicorhinus barbatulus and tested the direct impact of several xenoestrogens on these ERs. Transcriptional activity of xenoestrogens was measured by the enzymatic activity of estrogen responsive element (ERE)-containing β-galactosidase in a yeast reporter system. The xenoestrogens tested were phenol derivatives, DDT-related substances, phthalic acid esters, and polychlorinated biphenyls, with 17β-estradiol (E2) as a subjective standard. The phenol derivatives [4-nonylphenol (4-NP), 4- t-octylphenol (4- t-OP) and bisphenol A (BPA)] exhibited significant dose-dependent responses in both ligand potency and ligand efficiency. Consistent with yeast assays using human or rainbow trout ERs, we observed a general subtype preference in that vbERα displayed higher relative potencies and efficiencies than vbERβ2, although our assays induced a stronger response for xenoestrogens than did human or trout ERs. Whereas 4-NP and 4- t-OP have similar EC50 values relative to E2 for both ER subtypes, the strong estrogenic response of BPA markedly differentiates vbERα from vbERβ2, suggesting possible species-specific BPA sensitivity. We report that the ameliorative yeast tool is readily applicable for indigenous wildlife studies of the bio-toxic influence of xenoestrogens with wildlife-specific estrogen receptors.

Habitat segregation by fishes in western Taiwan rivers

Summary Habitat segregation has been recognized as an important means of resource partitioning in river fish assemblages. Association between river fishes and habitat features were identified through principal component analysis (PCA). Fish and habitat data were collected in the Kaoping, Tsengwen, Choshui, and Tatu rivers from July 1997 to June 1999 in western Taiwan. Electrofishing was used to collect fishes in grids, and environment variables in the sampled areas were measured immediately after sampling. The first four PCs of depth, velocity, cover, substrate and water temperature variables explained 92.3% of the total variance in habitat characteristics. Varicorhinus barbatulus, Acrossocheilus formosanus and Tilapia mossambica in the upper right quadrant, indicated preference for deep-water habitat. Species usually associated with shallow water habitat include several minnow species. Rhinogobius brunneus, Hemimyzon formosanum, Sinogastromyzon puliensis and Crossostoma lacustre distribution is centred in the upper and lower left, indicating preference for shallow water. Principal component (PC) scores on Zacco pachycephalus, Abbottina brevirostris and Hemiculter leucisculus appeared to have no special preference. Differences in habitat use exhibited by these species may be related to success in finding food and avoiding predators.

Impacts of natural disturbance on fish communities in the Tachia River, Taiwan

Extensive landslides triggered by the Chi-Chi earthquake of 21 September 1999 introduced debris into the middle section of Tachia River, while debris flow was subsequently induced by Typhoon Toraji on 30 July 2001. We compared population size, species composition, and diversity of the fish community during a six-year period before and after these disturbances. The dominant taxa were Acrossocheilus paradoxus, Crossostoma lacustre, Hemimyzon formosanum, Rhinogobius brunneus, Varicorhinus barbatulus and Zacco pachycephalus. H. formosanum and R. brunneus increased then decreased suddenly in abundance following the earthquake and the typhoon. Our results suggest that both resistance and resilience were important in maintaining long-term fish community structure. Fish community resistance at station 1 (downstream of the disturbance) was lower than at station 2 and station 3 (at and upstream of the disturbance). Fish communities recovered quickly after a few months, possibly reflecting a correlation between assemblage composition and seasonal variation. Our study illustrates the ecological variability that can be induced by hydrologic and evolutionary processes in a stream. Relative positions of habitats provide a spatial framework for evaluating stress effects of abiotic and biotic factors in regulating population size and community succession patterns.

Enhancing the contrast and visibility of daily growth increments in fish otoliths etched by proteinase K buffer

The otoliths of the amphidromous gobies Stiphodon elegans and Sicyopterus japonicus, a marine eel Strophidon sathete and a freshwater fish Varicorhinus barbatulus were digested by proteinase K buffer (PKb), which removed the proteins and retained the major calcified structure to reveal conspicuous daily increments. Compared with etching by ethylenediaminetetraacetate (EDTA), etching with PKb revealed more visible daily increments and enhanced the contrast. Moreover, by using PKb, both the daily increments and annuli could be observed simultaneously. The better performance of PKb as an etching agent can be attributed to digesting of predominantly only the organic matrix and leaving the calcified structure almost intact. PKb provides another effective means to reveal otolith microstructure so as to examine and count daily growth increments.

ICHTHYOXENUS FUSHANENSIS, NEW SPECIES (ISOPODA: CYMOTHOIDAE), PARASITE OF THE FRESH-WATER FISH VARICORHINUS BARBATULUS FROM NORTHERN TAIWAN

Ichthyoxenusfushanensis, new species, a flesh-burrowing parasite of Varicorhinus barbatulus, collected from a mountain stream in northern Taiwan, is described. It resembles the only congeneric species, I. formosanus, recorded in Taiwan, but can be distinguished from the latter by the narrower forehead, smooth posterior margin of pereionites, narrower pleotelson, shorter antennae 1 and 2, and short carpus of pereiopod 1. The two species also differ in the structure of the mouthparts, especially the number of terminal spines on the mandible and maxilliped. In addition, the two species occur in different habitats and on different hosts. Ichthyoxenus formosanus is found in the body cavity of the fresh-water carp, Carassius auratus, occurring in lakes or ponds. The morphological differences between free-living mancas and parasitic adults of Ichthyoxenus fushanensis are compared. An undescribed cymothoid isopod of the genus Ichthyoxenus Herklots, 1870, was recently recovered from the fresh-water fish, Varicorhinus barbatulus (Pellegrin, 1908), in a mountain stream at Fushan Village, Wulai, Taipei County, in northern Taiwan. Ichthyoxenus is a genus of parasitic isopods that live on a variety of fresh-water and marine fishes. The distribution patterns and habitats of the

Study of Fishes in the Chung-Kung Stream: Species Distribution and Organochlorine Pesticide Residues

Abstract Fish of the Chung-Kung stream of Miau-Li County, northern Taiwan, were sampled on seven occasions from March 1994 through to August 1995. A total of 45 species belonging to seven orders and 25 families were caught at 6 sites along the stream. There were ten species of Cyprinidae, and four or fewer of the other 24 families. Major species found upstream at site F were Varicorhinus barbatulus and Hemimyzon formosanum. This section of the stream is considered unpolluted if these water quality sensitive species are present. Acrossocheilus formosanus and Crossostoma lacustre can thrive in slightly polluted water and occurred in the middle reaches at site D. Zacco pachycephalus could also survive in mildly polluted water and occurred at site C. the major species at site B were tilapia (Oreochromis hybrid species) and thus this section was considered heavily polluted. Site A in the lower, tidal, reaches contained species of Mugilidae and was considered as moderately polluted. Thirty seven fish muscle sam...