Zacco Pachycephalus Research Articles

Occurrence and distribution of yellow grub trematodes (Clinostomum complanatum) infection in Taiwan.

Digenetic trematodes of the genus Clinostomum are widely distributed in many species of freshwater fish and are known to cause the zoonotic disease Halzoun. Humans may become accidental hosts if they ingest raw freshwater fish containing metacercaria of Clinostomum complanatum, which causes pharyngitis or laryngitis. The yellow grub parasitizing cultivated ayu (Plecoglossus altivelis) and loach (Misgurnus anguillicaudatus) was one of the most serious problems in fish farms from 1977 to 1979 in Taiwan. The present study revealed, for the first time, frequent occurrence of C. complanatum metacercaria in various fish species in a natural environment, the Dahan River, in Taiwan. We examined 1503 fish specimens belonging to four families and 162 snails representing six species. C. complanatum metacercaria was mainly from the fish family Cyprinidae, and only cercaria from the snail Radix swinhoei was recovered. The prevalence and mean intensity of metacercaria were 9.8% and 9.35 parasites/infected fish, respectively. The prevalence of cercaria was low, 0.62%, in snails. Acrossocheilus paradoxus, Zacco barbata, Zacco pachycephalus, Zacco platypus, Onychostoma barbatula, and Hemibarbus labeo are new host records. Metacercariae were primarily found in the operculum, mandible, muscle, and oral cavity of fish. Morphological description and molecular analysis with 18S rDNA sequencing allowed for rapidly identifying C. complanatum. Encysted and excysted metacercariae cultivated at 22°C in physiological saline died within 60h. The mean intensity of infection increased with an increasing length of Z. pachycephalus. We found no association between monthly parasite prevalence and mean intensity at each sampling location. No C. complanatum metacercaria survived after 8h of salting. The Dahan River has suitable conditions and hosts (snails, fish, and fish-eating birds) for maintaining the life cycle of C. complanatum.

New insights on molecular systematics of opsariichthines based on cytochrome b sequencing

Species or sub‐species including Parazacco spilurus fasciatus, Candidia barbatus, Zacco temminckii, Zacco sieboldii, Zacco platypus, Zacco macrolepis, Zacco pachycephalus, some undetermined Zacco taxa formerly misidentified as Chinese Z. platypus and Opsariichthys uncirostris were sampled, and their mitochondrial cytochrome b genes were sequenced. In the phylogenetic analysis, the genus Parazacco forms the basal taxon for the remaining members of the opsariichthine fishes, which can be divided into two major groups. The first group includes species with one longitudinal stripe on the flanks and contains Z. temminckii, Z. sieboldii and C. barbatus with sequence divergences of 12·7–16·5%. The second group has species with 10 cross bars on the body and includes O. uncirostris, Z. macrolepis, Z. platypus, Z. pachycephalus and five undetermined Zacco spp. (A–E) lineages. The estimated divergence times of mtDNA lineages within the nominal species of Z. pachycephalus and C. barbatus are >2 million years ago. According to geological evidence, this predates the earliest possible time for their arrival in Taiwan Island and indicates that the population differentiations might have been taken place in mainland China before their subsequent dispersal to Taiwan.

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.

Isolation and cross‐species amplification of microsatellite loci in the freshwater minnow Zacco pachycephalus (Teleostei: Cyprinidae) for diversity and conservation genetic analysis

AbstractAsian minnows of the genus Zacco are dominant fish in various freshwater ecosystems. Two species, Zacco pachycephalus and Z. platypus, occur in Taiwan and are favourite targets for local sport anglers. The introduction of Zacco fish into nonindigenous habitats in Taiwan has become a conservation issue. We developed eight polymorphic microsatellites for Z. pachycephalus (average HE = 0.779) and these microsatellites were applicable to Z. platypus, which showed a comparable polymorphic level (average HE = 0.784). These loci can be used as genetic markers for identifying conservation units and studying population differentiation for both Zacco species.

Influence of glaciation on divergence patterns of the endemic minnow, Zacco pachycephalus, in Taiwan.

The genetic subdivision of the endemic minnow, Zacco pachycephalus, in 12 rivers of Taiwan was studied by allozyme electrophoresis. Among 26 loci surveyed, six were significantly differentiated among sites. Allozyme genotype frequencies within samples accord with Hardy-Weinberg expectations. A highly divergent genetic structure among sites (FST = 0.497) with low genetic variability within samples (H = 0.006-0.062, mean = 0.03) suggests that local populations originated from a small number of founders. UPGMA and Fitch trees derived from Nei's genetic distance and hierarchical analysis of FST values reveal that samples of Z. pachycephalus can be divided into northern, middle, and southern subgroups and that most genetic variation (87%) is distributed among rather than within groups. It is proposed that there were two isolated refugia during the most recent glacial period, and that populations of the southern group (Group I) originated from a southern refugium in Taiwan below the boundary of the Kaoping River, and other groups (Group II), including northern and middle subgroups, originated from a refugium located on the extinct land-bridge between Taiwan and mainland China. The postglacial division between northern and middle subgroups may be due to hydrological differences between these two regions.

Osteology of Zacco pachycephalus, sensu Jordan & Evermann (1903), with special reference to its systematic position

The skeletal system of Zacco pachycephalus, sensu Jordan & Evermann (1903), is described and compared with that of other related barilines to clarify its systematic position. Osteological characters fall generally into two categories in terms of apomorphic features. The first category is exemplified by autapomorphies such as lower jaw bone shape and the number of branchiostegal rays and hypurals. The latter characters are highly unusual among Cyprinidae. The second category consists of synapomorphies linking Z. pachycephalus and Opsariichthys uncirostris. Specialization of jaw bones for a piscivorous habit is also notable. The quadratepterygoid fenestra of Z. pachycephalus and O. uncirostris is considered derived. We conclude that Zacco pachycephalus should be transferred from Zacco to Opsariichthys based on the present osteological analysis.

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...

The reproductive biology of an endemic cyprinid,Zacco pachycephalus, in Taiwan

Reproductive parameters including body weight-length relationship, condition factor, gonadosomatic index (GSI) and fecundity of an endemic cyprinid,Zacco pachycephalus, were studied from October 1991 to January 1993. Although the condition factor was similar between both sexes, GSI values of female (3.72 to 14.24%) were significantly larger than that of males (0.21 to 2.23%) during the major breeding season. The number of yolky eggs per fish ranged from 459 to 2059. Ovum size distribution, annual GSI value, and recruitment of juvenile fish indicated thatZ. pachycephalus conducted two major spawning activities in spring (February to April) and summer (June to August). The larger GSI value and number of yolky eggs in spring compared to those in summer implies thatZ. pachycephalus has evolved a reproductive style by investing more energy in spring to avoid the damage of summer freshet on its recruitment success. The mating behavior ofZ. pachycephalus is similar to that of otherZacco fishes.