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Loaches, Misgurnus anguillicaudatus, from Poyang Lake are a small economic fish, falling into three categories with typical blackspot characteristics, namely, big blackspot loaches (BBL), small blackspot loaches (SBL), and non-blackspot loaches (NBL), respectively. Pigment cell composition, pigment content, tyrosinase content and activity of three kinds of loaches were investigated. Our results showed that there were three types of skin pigment cells, namely, melanophores, xanthophores and iridophores. Melanophores in dorsum were more than in abdomen. Melanophore cytosomes in BBL were larger than those in SBL and NBL, and melanosomes were the largest in stage four. The melanophores in dorsal skin of SBL or NBL were small cell bodies, spindle-like, and in chain distribution. There was an extremely significant difference in melanin content in BBL between the dorsum and abdomen (P 0.05). In dorsal skin, tyrosinase content was the highest in BBL, and it was significantly lower in NBL than in BBL and SBL (P

This study represents a description of the diet composition of one of the largest European cobitids, the weatherfish Misgurnus fossilis. Specimens were collected in a drainage canal, representing a typical habitat for weatherfish, and with gut content analysis conducted with regard to individual total length and maturity stage. Overall, the weatherfish diet mainly consisted of Copepoda, Cladocera, Ostracoda, Oligochaeta, Asellus aquaticus, Chironomidae and Coleoptera larvae, Gastropoda, and detritus. To evaluate size‐related patterns of resource use, fish were assigned to two size classes, defined according to size at first maturation. ANOSIM analyses revealed major ontogenetic shifts in feeding strategy, which were related to size and maturity, with a significant ontogenetic shift in feeding pattern, marked by differences in the proportions of the main taxonomic groups of prey consumed. Copepoda and Cladocera dominated in the diet of small and immature individuals, while large weatherfish primarily fed on detritus. Similarly, cluster analysis of diet classified into these food types showed distinct two groups comprising juvenile and mature fish. The weatherfish is a food opportunist using all available resources, but spatially showed a change in feeding sites. Smaller and sexually immature individuals more often use prey caught in the water column and among macrophytes, while larger (sexually mature) individuals occupying the bottom, much more often use detritus as a food base.

The European weather loach (Misgurnus fossilis) is classified as highly endangered in several countries of Central Europe. Populations of M. fossilis are predominantly found in ditches with low water levels and thick sludge layers and are thus hard to detect using conventional fishing methods. Therefore, environmental DNA (eDNA) monitoring appears particularly relevant for this species. In previous studies, M. fossilis was surveyed following eDNA water sampling protocols, which were not optimized for this species. Therefore, we created two full factorial study designs to test six different eDNA workflows for sediment samples and twelve different workflows for water samples. We used qPCR to compare the threshold cycle (Ct) values of the different workflows, which indicate the target DNA amount in the sample, and spectrophotometry to quantify and compare the total DNA amount inside the samples. We analyzed 96 water samples and 48 sediment samples from a pond with a known population of M. fossilis. We tested several method combinations for long‐term sample preservation, DNA capture, and DNA extraction. Additionally, we analyzed the DNA yield of samples from a ditch with a natural M. fossilis population monthly over one year to determine the optimal sampling period. Our results showed that the long‐term water preservation method commonly used for eDNA surveys of M. fossilis did not lead to optimal DNA yields, and we present a valid long‐term sample preservation alternative. A cost‐efficient high salt DNA extraction led to the highest target DNA yields and can be used for sediment and water samples. Furthermore, we were able to show that in a natural habitat of M. fossilis, total and target eDNA were higher between June and September, which implies that this period is favorable for eDNA sampling. Our results will help to improve the reliability of future eDNA surveys of M. fossilis.

To study the effect on amino acid and mineral content of the loach meat by adding Fe (II) chelating hairtail protein hydrolysates (Fe (II)‐HPH) to the feed. A total of 100 healthy loaches were selected. After 1 week's adaptive feeding, they were randomly divided into five groups and fed with feeds containing of Fe (II)‐HPH (0, 0.5, 1, 2, and 4 g/kg). On the 40th day, detection work of general nutrients (moisture, ash, crude protein, and crude fat), mineral elements (Fe, Mn, Cu, Zn, Na, K, and Ca), amino acid and amino acid score (AAS), Chemical Score (CS) and essential amino acid index (EAAI) indexes were done. The results show that crude protein has the highest content while crude fat has the lowest when amount of added Fe (II)‐HPH in feed is 2 g/kg. The Fe content is significantly improved while amount of added is 1, 2, 4 g/kg. The Ca content is significantly improved and the Zn content is significantly improved while amount of added was 2 g/kg. Mn contents are significantly lower than control while amount of added is 4 g/kg. Based on analysis of amino acids in each group, the nutritional value of loach meat with 2 g/kg Fe (II)‐HPH addition amount is relatively high, total amount of essential amino acids increases significantly, and EAA/TAA and EAA/NEAA improve significantly. In conclusion, adding 2 g/kg Fe (II)‐HPH to feed could improve the nutritional values of loach meat.

We examined the functional morphology of loach Misgurnus anguillicaudatus skin by using synchrotron X-ray micro-computed tomography (SR-μCT) and high-contrast staining using osmium tetroxide or phosphotungstic acid (PTA), which enhances the image contrast of soft tissues. The captured high-spatial resolution images revealed that the surface ornamentations were stuck in the basement membrane of the loach scales. The ornamentations consisting of grooves (radii) and ridges (circuli) that can move freely and bend flexibly. The cross-sectional lateral microstructures of flat, concave and convex loach skins were observed from a live image of loach skin obtained through dark-field optical coherence tomography (OCT) imaging. The thickness of loach skin was changed with varying empty space between the mucous-cell layer and the scales by bending motion of loach. In addition, through direct measurement of drag reduction of loach skin, the mucous layer was found to have a strong influence on the reduction of skin friction. The present results enhance the understanding of the functional morphologies of mucous layer of loach to secrete mucus for skin friction reduction.

The European weather loach (Misgurnus fossilis) is a cryptic and poorly known fish species of high conservation concern. The species is experiencing dramatic population collapses across its native range to the point of regional extinction. Although environmental DNA (eDNA)-based approaches offer clear advantages over conventional field methods for monitoring rare and endangered species, accurate detection and quantification remain difficult and quality assessment is often poorly incorporated. In this study, we developed and validated a novel digital droplet PCR (ddPCR) eDNA-based method for reliable detection and quantification, which allows accurate monitoring of M. fossilis across a number of habitat types. A dilution experiment under laboratory conditions allowed the definition of the limit of detection (LOD) and the limit of quantification (LOQ), which were set at concentrations of 0.07 and 0.14 copies μl-1 , respectively. A series of aquarium experiments revealed a significant and positive relationship between the number of individuals and the eDNA concentration measured. During a 3 year survey (2017-2019), we assessed 96 locations for the presence of M. fossilis in Flanders (Belgium). eDNA analyses on these samples highlighted 45% positive detections of the species. On the basis of the eDNA concentration per litre of water, only 12 sites appeared to harbour relatively dense populations. The other 31 sites gave a relatively weak positive signal that was typically situated below the LOQ. Combining sample-specific estimates of effective DNA quantity (Qe ) and conventional field sampling, we concluded that each of these weak positive sites still likely harboured the species and therefore they do not represent false positives. Further, only seven of the classified negative samples warrant additional sampling as our analyses identified a substantial risk of false-negative detections (i.e., type II errors) at these locations. Finally, we illustrated that ddPCR outcompetes conventional qPCR analyses, especially when target DNA concentrations are critically low, which could be attributed to a reduced sensitivity of ddPCR to inhibition effects, higher sample concentrations being accommodated and higher sensitivity obtained. ispartof: JOURNAL OF FISH BIOLOGY vol:98 issue:2 pages:399-414 ispartof: location:England status: published

A 10 week feeding trial was conducted to evaluate the effects of different dietary soybean oil (SO) levels on growth performance, fatty-acid composition and lipid deposition in viscera, histology and histochemistry of liver, intestine and hepatic-lipid metabolism-related gene expressions in pond loach Misgurnus anguillicaudatus juveniles. Misgurnus anguillicaudatus (mean ± s.d. mass 0·40 ± 0·01 g) were fed five experimental diets containing SO at different concentrations: 0, 20, 32, 56 and 100% SO and a diet containing 100% fish oil (100% FO). The mass gains and specific growth rates of M. anguillicaudatus fed 20% SO and 100% FO diets were significantly higher than those of the other groups (P

Although it has been reported that populations of the Japanese dojo loach Misgurnus anguillicaudatus (Cypriniformes: Cobitidae) belong to two distinct mitochondrial (mt)DNA (Type I and Type II), the taxonomic status of the species remains unresolved. To address this question, nuclear DNA and morphological analyses were performed on M. anguillicaudatus population in the Nakaikemi Wetland, where Type I and Type II lineages are sympatric. Results suggest the existence of a cryptic species (Type I) within the Japanese dojo loach.

Experiments on the swimming kinetics and behaviour of weather loach Misgurnus anguillicaudatus showed that horizontal swim speed was significantly greater than swim speeds when ascending to or descending from the water surface to gulp air. Vertical swimming speeds during ascending or descending were similar. Misgurnus anguillicaudatus swam unsteadily during vertical movements compared with horizontal movements.

In this study, we aimed to characterize the fish community structure and identify the drivers contributing to homogenization/differentiation processes in four tributaries to the Pearl River, Guangxi Province, China, over the past few decades. We sampled 22 sites seasonally from 2013 through 2015, and these sites were selected based on archived records of previous sampling conducted in the 1980s. Jaccard's faunal similarity index, cluster analysis, and canonical correspondence analysis (CCA) were applied to describe the homogenization/differentiation of fish community and illustrate the potential effectors. The number of fish species present in three of the four sampled tributaries declined dramatically over the past 30 years, leading toward a trend of increased fish community homogeneity throughout the watershed. Results from multidimensional scaling and cluster analyses allowed us to divide the study area into two distinct ecoregions. Four species (yellow catfish Pelteobagrus fulvidraco, pond loach Misgurnus anguillicaudatus, Nile tilapia Oreochromis niloticus, and sharpbelly Hemiculter leucisculus) were considered to be indicative fish species contributing more than 5% of the dissimilarity between the two eco‐regions according to the results of similarity percentage procedure. Results from CCA revealed that pH and latitude corresponded with the dominant fish species of each respective tributary. More specifically, CCA results allowed us to classify dominant fish species into three distinct groups. The first group was mainly located in Guijiang characterized by higher latitudes and lower pH values, the second group was widespread in the four tributaries, and the last group was primarily distributed in Yujiang, Youjiang, and Zuojiang characterized by lower latitudes and higher pH values. Spatial differentiation of fish community structure and temporal homogeneity of species composition were attributed to the joint actions of human interventions including construction of dams and introductions of exotic fish species that led to habitat degeneration and fragmentation, and unequal interspecies competitions.

Thermal requirements of larval weatherfish Misgurnus fossilis were investigated in terms of growth, survival and aerobic performance. Growth and survival of M. fossilis larvae acclimated to five temperatures (11, 15, 19, 23 and 27° C) were measured over 25 days. In the upper temperature treatments (19, 23 and 27° C), survival of larvae was stable throughout the entire rearing period (>75%), whereas 11 and 15° C resulted in severe declines in survival (to 27° C. All larvae of the 35° C regime, however, died within the ṀO2 measurement period. M. fossilis larvae show greater than expected tolerance of high temperatures. On the other hand, low temperatures that are within the range of likely habitat conditions are critical because they might lead to high mortality rates when larvae are exposed over periods >10 days. These findings help to improve rearing conditions and to identify suitable waters for stocking and thus support the management of re-introduction activities for endangered M. fossilis.

In a few Japanese populations of the loach Misgurnus anguillicaudatus (Teleostei: Cobitidae), clonal diploid lineages produce unreduced diploid eggs that normally undergo gynogenetic reproduction; however the origin of these clones remains elusive. Here, we show the presence of two diverse clades, A and B, within this loach species from sequence analyses of two nuclear genes RAG1 (recombination activating gene 1) and IRBP2 (interphotoreceptor retinoid-binding protein, 2) and then demonstrate heterozygous genotypes fixed at the two loci as the evidence of the hybrid nature of clonal lineages. All the clonal individuals were identified by clone-specific mitochondrial DNA haplotypes, microsatellite genotypes, and random amplified polymorphic DNA fingerprints; they commonly showed two alleles, one from clade A and another from clade B, whereas other wild-type diploids possessed alleles from either clade A or B. However, we also found wild-type diploids with clone-specific mitochondrial DNA and nuclear genes from clade B. One possible explanation is an introgression of a clone-specific mitochondrial genome from clonal to these wild-type loaches. These individuals likely arose by a cross between haploid sperm from bisexual B clade males and haploid eggs with clone-specific mtDNA and clade B nuclear genome, produced by meiotic hybridogenesis (elimination of unmatched A genome followed by meiosis after preferential pairing between two matched B genomes) in clone-origin triploid individual (ABB).

To evaluate the influence of ploidy elevation and aneuploidy on spermatozoa in the loach Misgurnus anguillicaudatus, we investigated some parameters (motility, concentration, and viability), fine structures (gross morphology, head size, and flagellum length), and energy-related biochemical factors (volume of mitochondrial mass per cell and ATP content) in diploid, hyper-diploid, and hexaploid-range spermatozoa produced in natural tetraploid, hyper-tetraploid, and hyper-triploid male loaches, respectively. Diploid spermatozoa exhibited vigorous movement and sufficient duration of motility similar to those in haploid spermatozoa. They had longer flagella, higher numbers and larger volume of mitochondria, and higher ATP content than haploid spermatozoa of wild-type diploids. No differences were observed in parameters and morphological characteristics between diploid and hyper-diploid spermatozoa. In contrast, the hexaploid-range spermatozoa of hyper-triploid males exhibited poor progressive motility in spite of a higher ATP content of spermatozoa. Spermatozoa with no flagella (36.0%) or multiple flagella (18.6%) were also observed in hyper-triploids. Ratios of head to flagellum length in hexaploid-range spermatozoa were significantly different from those of haploid spermatozoa. In addition to the normal 9+2 microtubule structure of the flagellum, an abnormal 9+1 microtubule structure was also observed in the spermatozoa of hyper-triploids.

The Oriental Weatherfish Misgurnus anguillicaudatus is invasive to many countries around the world, but very little is known about the life history or environmental tolerances of this cryptic fish. As part of a larger study of its life history, we conducted an experiment designed to determine the critical thermal minimum (CTmin) of Oriental Weatherfish collected from water bodies near Boise, Idaho, USA. In each of three experimental trials, 16 fish were placed into individual tanks in an environmental chamber where over the course of 20 d the ambient air temperature was lowered to 0°C. Air temperature was then held at 0°C for 102–134 h. Individual tank temperatures decreased over the course of each trial such that fish were exposed to temperatures ranging from 20°C to −3.64°C. Tank temperatures reaching below the ambient air temperature set-point were attributed to cold air currents within the environmental chamber. Six of 48 fish died due to temperature-related factors. Thirty-eight of the remain...

To determine the genotype with better traits for aquaculture practices of the loach, factorial crosses were made among diploid (D), tetraploid (T) dojo loach, Misgurnus anguillicaudatus, and large-scale loach, Paramisgurnus dabryanus (P), producing DD, DT, DP, TD, TT, TP, PD, PT, and PP genotypes (female listed first). The growth performance and survival of different genotypes in culture were evaluated through a 48-wk rearing trail. The average fertilization rate in genotypes with P. dabryanus as female parental was significantly higher than those of M. anguillicaudatus as female parental. The average fertilization level of sperm from P. dabryanus was about the same as diploid M. anguillicaudatus but significantly higher than tetraploid M. anguillicaudatus. The highest survival rate was found in DD group (52.77%) and PP group (50.31%) (P > 0.05). The intergenetic crosses between P. dabryanus and M. anguillicaudatus, especially for PD (19.05%), DP (17.89%), and PT (15.44%) groups, exhibited poor survival rates. Under the similar rearing conditions, PP group showed significant growth advantage. Growth rates of the interspecific hybrid progenies were found to be intermediate in comparison with the parental species. According to these results, the PP genotype is more suitable for aquaculture practice.

Natural occurrence of hexaploid loach Misgurnus anguillicaudatus detected in central China is reported here for the first time. The evidences from karyotyping, DNA content analysis and nuclear volume measurements were described to confirm the hexaploid nature of the identified individual.

Summary The electrophoretic pattern of the loach muscle adenylate kinase was composed of one or two major bands. Each major band was preceded by two minor bands. Three codominant alleles were postulated to segregate in loach. Each allele coded for one major band with different mobility. Adenylate kinase (AK. E.C. 2.7.4.3.) catalyses the reaction 2ADP ATP + AMP. and is known as a heat stable protein constituent of skeletal muscle. Electrophoretic variation of AK has been reported in the pika Ochotona r. rufescens (Vergnes et al. 1974). the teleostean fish Zoarces viviparus (Frydenberg & Si-monsen, 1973), the mussel Mvtilus edulis (Ahmad et al. 1977). and the tunicate Ciona intestinalis (Schmidtke & Engel. 1980). In this note, individual variation of AK in muscle extracts of the fresh-water fish Misgurnus anguillicaudatus is described. Loach were collected in ponds or purchased from fish shops (Table 1 & Fig. 1). Three populations (OS. AS and KN) were purchased from fish shops in Osaka. Akashi and Kanazawa cities, respectively. Their exact sampling locations were not known. For reference, the locations of these cities are indicated by an open circle in Fig. i. Fish were collected and stored frozen at – 20 oC at the sampling time given in Table 1. Muscle extracts were prepared and examined in the period February-April 1981.The method for preparing muscle extract and-the starch gel electrophoretic procedures were the same as those reported previously (Kimura, 1976). The amine-citrate buffer system as described by Clayton & Tretiak (1972) was used. AK was stained by the method of Allendorf et al. (1977). After electrophoresis, an inhibition test was also performed by immersing the gel in 10-3M 5.5'-dithiobis-(2-nitrobenzoate) solution for 30 minutes at room temperature. Under the electrophoretic condition used in the present study, all of the AK

Summary Electrophoretic variations of enzymatic and non-enzymatic proteins were investigated in 8 populations of the loach Misgurnus anguillicaudatus. The cathodic hemoglobin and the muscle protein in the region II were shown to be polymorphic, in addition to the five polymorphic proteins previously reported (the anodic hemoglobin, muscle protein in the region III, 6-phosphogluconate dehydrogenase, phosphoglucomutase and aspartate aminotransferase; Kimura, 1976 & 1977). The muscle proteins in the regions I, IV and V were monomorphic. The values of genetic distances between loach populations, calculated over 10 loci, indicated that M. anguillicaudatus should be classified into two local races.

In this study, male Chinese loaches in a semistatic waterborne exposure system were used to study the effects of tributyltin (TBT) on vitellogenin (Vtg) production induced by 17 beta-estradiol (E2), TBT accumulation and distribution in tissues, and the effects of E2 on the distribution of TBT. The results demonstrate that TBT does not induce the synthesis of Vtg in male Chinese loach and that TBT could significantly inhibit Vtg production induced by E2, after exposure to binary mixtures of E2 and TBT for 14 days. TBT was found to accumulate in the liver, kidney, gills, intestines, and muscles of male Chinese loach, wherein the liver, kidney, gills, and intestines were found to have the most TBT accumulation. The existence of E2 did not significantly affect tissue distribution of TBT. (C) 2008 Wiley Periodicals, Inc. Environ Toxicol 24: 531-537, 2009.

– Oriental weatherloach (Misgurnus anguillicaudatus), a benthic freshwater fish species native to East Asia, was first recorded in Australian freshwater systems in 1984. Although this species is widely established around the world, very little is known about its potential impacts as an invader. We gathered field data to parameterise a mesocosm experiment investigating the impacts of Oriental weatherloach in Southeastern Australia. During this experiment, Oriental weatherloach caused significant reductions in macroinvertebrate numbers and biomass. Additionally, Oriental weatherloach were associated with elevated ammonia, nitrate/nitrite (NOx), and turbidity levels. Because of issues involved in scaling up mesocosm experiments we are not able to conclusively determine that Oriental weatherloach are having large impacts in natural systems. Our results come from mesocosms designed to mimic natural conditions, however, and they thus indicate that ecological impacts may be occurring, and underline the need for further research and control.

Oriental weatherfish Misgurnus anguillicaudatus, from southern China, have been imported to Germany in large numbers for the garden pond trade. The first record of M. anguillicaudatus from Central Europe, a population that has been established for at least 14 years in a small nature reserve in Germany, is detailed.

As part of the technique for preservation of endangered fish species, germline chimeras using the loach (Misgurnus anguillicaudatus) model were generated by embryonic cell manipulation. Transplanting cells from early-stage embryos of a wild-type strain to the blastoderm of an orange-type strain generated chimeras. Within three days, many of the resulting individuals exhibited a dark pigment on several parts of their body, characteristic of the donor but not of the orange strain. At one year of age, four chimeras (one female and three males) were pair-mated with the orange type, and F1 was obtained. One of the four F0 chimeras produced progeny similar to the wild type at a frequency of 0.24% (2/841). The results suggest that this method is a promising technique for the preservation of endangered fish species. J. Exp. Zool. 293:624–631, 2002. © 2002 Wiley-Liss, Inc.

Summary The loach Misgurnus anguillicaudatus is a fresh-water teleost and is known to be widely distributed through Japan, Formosa, Korea and into eastern Asia. The author has reported electrophoretic variation in five different proteins in the loach (Kimura, 1976a, b, c). This note describes a sixth example, electrophoretic variation of aspartate aminotransferase (AAT; EC 2.6.1.1.).

The triploid (diploid × tetraploid) loach Misgurnus anguillicaudatus lays large, triploid eggs and small, haploid eggs simultaneously. We conducted cytogenetic examination of gonadal cells to determine the mechanisms responsible for this unusual oogenesis. In immature ovaries of triploids, both triploid (3n = 75) and hexaploid (6n = 150) metaphases were detected. Oocytes at the pachytene stage were categorized into two types: small and large. The small oocytes gave about 50 chromosome elements, comprising 25 thick, densely stained bivalents and 25 thin, faintly stained univalents, that is, bivalent-univalent complexes. The large ones showed no fewer than 60 thick elements, considered to be 75 bivalents. Cytological examination of full-grown oocytes cultured in vitro revealed that both large and small oocytes undergo two conventional successive meiotic cycles: formation of a bipolar spindle in meiosis I and equal segregation of homologues, extrusion of the first polar body, and the appearance of a bipolar spindle in meiosis II. In the small, full-grown oocytes, some chromosomes were observed to detach from the spindle and remain in the surrounding cytoplasm, and then these chromosomes (presumably unpaired univalents) were eliminated from the meiotic event. We conclude that triploid eggs are formed by a quasinormal meiosis of the hexaploid oocytes of large size, which are generated by premeiotic endomitosis, while the haploid eggs are produced from bivalents after eliminating univalents in the meiosis of triploid oocytes of small size. J. Exp. Zool. 281:608–619, 1998. © 1998 Wiley-Liss, Inc.

In the loach Misgurnus anguillicaudatus (Pisces: Cobitidae), triploid females derived from the hybridization of normal diploid females and natural tetraploid males generate both triploid and haploid eggs simultaneously. Diploid progenies were produced by fertilizing the haploid eggs of triploids with haploid spermatozoa of normal diploids. Ldh-1 and Mdh-2 allozyme loci were electrophoretically diagnostic, because diploid and tetraploid loach exhibited the diverged genotype aa and bbbb at each locus, respectively. Diploids from triploid (abb) × diploid (aa) crosses frequently exhibited a heterozygous ab genotype at each locus but sometimes showed genotypic frequencies that fit a random pairing model (aa:ab = 1:2) of two of three chromosomes in each set of homologues. These results show that the entire haploid genome of one parent is not completely excluded in the oogenesis of triploid loach, and the haploid eggs are not formed in a typical hybridogenetic manner. However, the two homologous chromosomes derived from the tetraploid parent are likely to pair with each other preferentially during the meiosis of triploid loach. J. Exp. Zool. 280:368–374, 1998. © 1998 Wiley-Liss, Inc.

In the loach Misgurnus anguillicaudatus, triploid fish, which had been produced by hybridizations between normal diploid females and natural tetraploid males, laid mature hexaploid (triploid egg nucleus + triploid polar body nucleus) eggs of large size as well as diploid (haploid egg nucleus + haploid polar body nucleus) eggs of small size. Gynogenetic triploidy was artificially induced by activating the large eggs with UV-irradiated spermatozoa. Gynogenetic hexaploidy was also generated by blocking the polar body release with pressure shock after induction of gynogenesis. Unexpected mosaics and pentaploid gynogens were infrequently observed in these crosses. Most triploid and all hexaploid gynogens from each triploid female demonstrated absolutely identical DNA fingerprints, suggesting clonal nature among the mature large eggs of each female. However, a small number of triploid gynogens were aclonal with slightly different DNA fingerprints. These results indicate that triploid loach generate viable large eggs which are genetically identical or highly similar to the somatic cells. J. Exp. Zool. 278:412–421, 1997. © 1997 Wiley-Liss, Inc.

Cell kinetics of the epidermal cells of normal juvenile loach (Misgurnus anguillicaudatus) were studied with autoradiography. Fish were labelled with single tritiated thymidine injections and killed at regular time intervals. Three cell types are identified by light microscopy, namely the epithelial cells, the club cells and the mucous cells. Epithelial cells are the only cell type that is involved in cell proliferation and, like the epithelial cells in the epidermis of other teleosts, proliferation of these cells occurs at all epidermal layers. The club cells and the mucous cells seem to be differentiated from the epithelial cells. Based on the time-course study of the labelling index and the grain count halving method, the generation time of the epithelial cells is estimated to be 4 days. From the labelling index of double injections, the duration of the S phase is determined as 8.3 h. Significant cell loss from the outermost layer and cell translocation from the lower layer to the upper layer within 4 days are inferred from the fluctuations of the labelling index curve. The renewal of these cells in the tissue seems rapid in comparison to the epidermis of terrestrial vertebrates.

The expression of annexins, a family of Ca2+/phospholipid-binding proteins, was analyzed by biochemical and immunological criteria in the fish Misgurnus fossilis (loach), which is a good model system to study embryonic events. Five different annexins (loach annexins A to E) are present as a maternal pool in the unfertilized eggs. Only annexin E is newly synthesized in the early embryo. Its synthesis, already apparent at mid-blastula, decreases in later stages when two additional annexins (F and G) appear. They are present among the newly synthesized polypeptides of mid-gastrula and later embryonic stages and are also found in loach larvae. The developmentally controlled expression of several annexins indicates a specific role of these proteins at certain embryonic stages.

Infectivity of Flexibator columnaris to loach, Misgurnus anguillicaudatus (Blecker, Gunther), was studied with variation conditions and the presence of other bacteria in the water medium. Invasion of fish by the poathogen varied with different water conditions. The highest prevalence of infection was observed in an experimentally formulated water containing 0·03% NaCl 0·01% KCl, 0·002% CaCl22H2O and 0·004% MgCI2 6H2O. The percentage of infection in tap water was similar to that of the formulated water. The infeetion rate was low in the individual salt solutions, and no infection occurred in distilled water. Even in the formulated water, the pathogen failed to infect the fish when Citrobacter freundii, Aeromonas hydrophila or Pseudomonas fluorescens were present at densities 100 times that of F. columnaris. However, in such cases, the numbers of F. columnaris in the mucus of the fish body surface did not increase much throughout the experimental period. In contrast, F. columnaris suceessfully invaded the fish in the presence of either Streptococcus sp., Flavobacterium flavescens or Flavobacterium fuscum, even when the numbers of these bacteria were 1000 times that of F. columnaris. In this ease, F. columnaris gradually increased its numbers on the fish body surface.

Fertilized eggs of loach (Misgurnus fossilis), rainbow trout (Salmo gairdneri) and zebrafish (Brachydanio rerio) were bombarded with high-velocity tungsten microprojectiles covered with plasmid DNA containing sequences of β-galactosidase and neomycin phosphotransferase genes. About 70% of the eggs survived the bombardment. The activity of both transferred genes was revealed in the fish developed from the bombarded eggs. Neomycin phosphotransferase gene sequences were detected by means of PCR amplification and Southern hybridization in the total DNA of zebrafish that survived after G418 treatment.

DNA polymerase alpha, beta, gamma activities were determined after fractionation of loach (Misgurnus fossilis) cell extracts in glycerol gradients. The extracts of mature eggs, liver and testes cells yielded similar specific activities of DNA polymerase gamma (9-15 units/g protein) but differed markedly in the specific activities of DNA polymerases alpha and beta. A high activity of DNA polymerase alpha was revealed in the egg extract (2.0 X 10(3) units/g protein), while no DNA polymerase alpha activity was detected in liver cells. The specific beta-polymerase activity in the extract of mature eggs was extremely low (3.6 units/g protein), about two orders of magnitude lower than the enzyme activity in the extracts of liver or testes cells. The specific activity of DNA polymerases alpha and gamma changes insignificantly during oocyte maturation and embryogenesis up to the stage of hatching (50 h at 21.5 degrees C). As the mass of oocytes and embryos remains virtually unchanged at the stages studied, no substantial changes were observed in the alpha and gamma-polymerase activities per egg or embryo. The specific beta-polymerase activity in embryo cells increases about threefold by the completion of epiboly (20 h).

The sexual dimorphism of Chinese cobitids consists of peculiar structures of the pectoral fins and of variations in the lengths of these as well as of the ventral fins. In all groups the paired fins are, as a rule, longer in the male sex, and the female has no lamina circularis, enlargement of pectoral rays or dilation of lateral muscles. In males of Cobitis and Misgurnus, the second rays of the pectorals are enlarged and possess at their base a bony plate (lamina circularis). In other Chinese genera the lamina circularis is absent. Males of the Misgurnus group are easily recognized by the dilation of the lateral muscles in the region of the dorsal fin. Males of Barbatula have several enlarged inner rays in the pectoral fin and numerous nuptial tubercles on the head, arranged in prepercular and preorbital groups. In the European, B. barbatula, however, tubercles on the head are wanting. In males of the Leptobotia and probably Botia groups, the first pectoral ray is enlarged, and the membrane between several of the inner rays is covered with nuptial tubercles. In general, in the Chinese cobitids the differences in sexual dimorphism are correlated with the differences between genera, i.e., each genus possesses a quite different sexual dimorphism; thus the secondary sexual characters can be used for taxonomic purposes.

(1960). Establishment and Early Dispersal of a Loach, Misgurnus anguillicaudatus (Cantor), in Michigan. Transactions of the American Fisheries Society: Vol. 89, No. 4, pp. 376-377.