Cryopreservation of sperm from the gudgeon, Microphysogobio rapidus (Cyprinidae): Effects of cryoprotectant, diluents, and dilution ratio

We investigated methods for cryopreserving sperm from the endangered gudgeon, Microphysogobio rapidus, by examining the effects of cryoprotective agent (CPA) concentration, diluent, and dilution ratio on post-thaw sperm quality. The quality of frozen sperm was evaluated in terms of motility and kinematic parameters, viability, DNA damage, and fertilization rate. We evaluated methanol, glycerol, dimethyl sulfoxide (DMSO), and ethylene glycol as CPAs. Sperm motility, velocity, and viability were significantly higher when methanol was used as the CPA (p < 0.05). The diluents tested were Ringer's solution, Kurokura's Extender, Common Carp Sperm Extender (CCSE), and buffered sperm motility-inhibiting saline solution (BSMIS); post-thaw motility was highest when Ringer's solution was used as the diluent. Next, various quantities of methanol were combined with Ringer's solution to identify the optimal dose of methanol. The dilution ratios tested ranged from 1:1 to 1:7. Cryopreserved sperm was thawed at 20 °C for 15 s. The use of 10% methanol with Ringer's solution at a dilution ratio of 1:5 resulted in the highest post-thaw sperm motility, viability, and velocity including VAP, VCL, and VSL. Post-thaw sperm showed significantly greater DNA damage than the control (fresh sperm) (p < 0.05). The fertilization rate was highest with fresh sperm (p < 0.05), followed by sperm frozen with 10% methanol + Ringer's solution. We recommend that the best way to preserve sperm in the studied species is to use a combination of Ringer's solution and 10% methanol at a 1:5 dilution ratio. Our findings will facilitate the artificial fertilization of M. rapidus.

Development of molecular identification methods for Dryophytes suweonensis and D. japonicus, and their hybrids

Background

As hybridization can reduce biodiversity or cause extinction, it is important to identify both purebred parental species and their hybrids prior to conserving them. The Suwon tree frog, Dryophytes suweonensis, is an endangered wildlife species in Korea that shares its habitat and often hybridizes with the Japanese tree frog, D. japonicus. In particular, D. suweonensis, D. japonicus, and their hybrids often have abnormal ovaries and gonads, which are known causes that could threaten their existence.

Methods

We collected 57 individuals from six localities where D. suweonensis is known to be present. High-resolution melting curve (HRM) analysis of the mitochondrial 12S ribosomal RNA gene was performed to determine the maternal species. Thereafter, the DNA sequences of five nuclear genes (SIAH, TYR, POMC, RAG1, and C-MYC) were analyzed to determine their parental species and hybrid status.

Results

The HRM analysis showed that the melting temperature of D. suweonensis was in the range of 79.0-79.3 °C, and that of D. japonicus was 77.7-78.0 °C, which clearly distinguished the two tree frog species. DNA sequencing of the five nuclear genes revealed 37 single-nucleotide polymorphism (SNP) sites, and STRUCTURE analysis showed a two-group structure as the most likely grouping solution. No heterozygous position in the purebred parental sequences with Q values ≥ 0.995 were found, which clearly distinguished the two treefrog species from their hybrids; 11 individuals were found to be D. suweonensis, eight were found to be D. japonicus, and the remaining 38 individuals were found to be hybrids.

Conclusion

Thus, it was possible to unambiguously identify the parental species and their hybrids using HRM analysis and DNA sequencing methods. This study provided fundamental information for D. suweonensis conservation and restoration research.

Characterization of the complete mitogenome of the endangered freshwater fish Gobiobotia naktongensis from the Geum River in South Korea: evidence of stream connection with the Paleo-Huanghe

Background

The freshwater fish Gobiobotia naktongensis (Teleostei, Cypriniformes, and Gobionidae) is an endangered class I species whose population size has been greatly reduced.

Objective

To successfully protect and restore the highly endangered freshwater fish G. naktongensis from the Geum River in South Korea.

Methods

The mitogenome was characterized using the primer walking method with phylogenetic relationships.

Results

The complete mitogenome of G. naktongensis Geum River was 16,607 bp, comprising 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA (tRNA) genes. Seventeen substitutions were found by comparing the tRNA regions between G. naktongensis Geum and Nakdong Rivers and G. pappenheimi; most were specific to G. naktongensis Nakdong River, with changes in their secondary structures. The comparison between G. naktongensis Geum River and G. pappenheimi revealed differences in the lengths of the D-loop and two tRNAs (tRNA^Arg and tRNA^Trp) and the secondary structures in the TΨC-arm of tRNA^His. In the phylogenetic tree, G. naktongensis Geum River did not cluster with its conspecific specimen from the Nakdong River in South Korea, but showed the closest relationship to G. pappenheimi in mainland China.

Conclusions

Our results support the existence of the Paleo-Huanghe River connecting the Korean peninsula and mainland China, suggesting that G. naktongensis in the Geum River should be treated as a different evolutionarily significant unit separated from that in the Nakdong River. The complete mitogenome of G. naktongensis Geum River provides essential baseline data to establish strategies for its conservation and restoration.

Trophic Ecology of Endangered Gold-Spotted Pond Frog in Ecological Wetland Park and Rice Paddy Habitats

Simple Summary

Gaining information about the habitat environment and biological interactions is important for conserving gold-spotted pond frogs, which are faced with a threat of local population extinction in Korea due to artificial habitat changes. Based on stable isotope ratios, we estimated the ecological niche space (ENS) of gold-spotted pond frogs in an ecological wetland park and a rice paddy differing in habitat patch connectivity and analyzed the possibility of their ENS overlapping that of competitive and predatory frogs. Gold-spotted pond frogs showed a broader ENS in the ecological wetland park, wherein predation was relatively easy, than in the rice paddy. However, the ENS of the gold-spotted pond frogs was highly probably overlapped with that of other competing frog species that shared some of the food sources. Nevertheless, since the stable isotope analysis showed that gold-spotted pond frogs fed on more diverse prey than their competitors, it would remain relatively easy to procure alternative food sources, which are less affected by the competition in an environment with abundant food. Therefore, for stable settling of gold-spotted pond frogs into habitats and preserving their population, establishing habitat environments with highly diverse food sources is crucial, following consideration of their feeding behavior.

Abstract

The gold-spotted pond frog (Pelophylax chosenicus) is an endangered amphibian species in South Korea. In order to obtain ecological information regarding the gold-spotted pond frog’s habitat environment and biological interactions, we applied stable isotope analysis to quantify the ecological niche space (ENS) of frogs including black-spotted pond frogs (P. nigromaculatus) and bullfrogs (Lithobates catesbeianus) within the food web of two different habitats—an ecological wetland park and a rice paddy. The gold-spotted pond frog population exhibited a broader ENS in the ecological wetland park than in the rice paddy. According to the carbon stable isotope ratios, gold-spotted pond frogs mainly fed on insects, regardless of habitat type. However, the results comparing the range of both carbon and nitrogen stable isotopes showed that gold-spotted pond frogs living in the rice paddy showed limited feeding behavior, while those living in the ecological wetland park fed on various food sources located in more varied trophic positions. Although the ENS of the gold-spotted pond frog was generally less likely to be overlapped by that of other frog species, it was predicted to overlap with a high probability of 87.3% in the ecological wetland park. Nevertheless, gold-spotted pond frogs in the ecological wetland park were not significantly affected by the prey competition with competitive species by feeding on other prey for which other species’ preference was low. Since these results show that a habitats’ food diversity has an effect on securing the ENS of gold-spotted pond frogs and prey competition, we recommend that the establishment of a food environment that considers the feeding behavior of gold-spotted pond frogs is important for the sustainable preservation of gold-spotted pond frogs and their settlement in alternative habitats.

Movement Patterns and Diel Activity of Anguilla japonica in the Middle Part of a Large River in South Korea

To investigate movement patterns and diel activities of Anguilla japonica in the freshwater ecosystem, we applied acoustic telemetry on A. japonica in the Geum River, a large river in South Korea. The acoustic tags were attached on 19 individuals of A. japonica (12 with a depth sensor) in May and October 2015 and tracked at approximately 100-km sections from an estuary barrage by 20 automatic listening stations. Only four individuals showed longitudinal movement (mean, 5.2 km), and others were detected by the receivers at release sites; therefore, A. japonica showed high site fidelity. We did not identify seaward migration during the study period (May to November). Conversely, A. japonica showed active diel movement. The number of detections (p = 0.002) and movement distance (p = 0.004) were higher at night-time (18:00-06:00). As most individuals were actively moving at nighttime, we confirmed that A. japonica is nocturnal, although few individuals also showed daytime movement. Although the population and habitats of A. japonica have been decreasing simultaneously, the East-Asian countries are still severely exploiting rivers and streams to use water resources, and result in habitat simplification generated. Therefore, these results contribute to effective A. japonica management regarding habitat and population conservation and restoration.

Responses of fish assemblage structure to large-scale weir construction in riverine ecosystems

Worldwide, increasing amounts of dams and weirs have been established in rivers in recent decades, often with drastic effects on their ecosystems. Between late 2009 and 2011, 16 large-scale dams were built in the main channels of the four largest rivers in South Korea, eight of these along the main channel of Nakdong River (300 km, 520 km in total). We studied the effect of these constructions on the fish community in the riparian zone based on intensive fish field surveys conducted in the littoral zone during 2007-2017, analysis of fishermen's catch data and molecular analysis of the diet of the keystone species, largemouth bass (Micropterus salmoides). Our results, based on RDA and GLM analyses, showed that environmental characteristics and fish species composition changed significantly with dam construction. Total fish abundance and biomass decreased after the start of the weir construction and fish richness decreased with time. The abundance and biomass of exotic fish decreased during construction but recovered afterwards, leading to higher proportions of exotics. Dominance and Shannon indices did not change significantly from before to after construction, while the Evenness index showed a significant decreasing trend. A comparison of the diet composition of largemouth bass showed decreasing genetic variation after construction. The changes in Functional Feeding Group (FFG) of the benthic communities at the study sites did not coincide with FFG changes in the prey items of largemouth bass, indicating a transition in feeding mode from before to after construction. In conclusion, the endemic and native fish species were most sensitive and showed lower resilience to disturbance by the large-scale dam construction than the translocated and exotic species, and the lake-like ecosystems after construction markedly improved the competitive capacity of these exotic fish over the native and endemic species in the riparian zone of the river.

Factors influencing physicians' advice about female sterilization in USA: a national survey

BACKGROUND

Tubal ligation can be a controversial method of birth control, depending on the patient's circumstances and the physician's beliefs.

METHODS

In a national survey of 1800 US obstetrician-gynecologist (Ob/Gyn) physicians, we examined how patients' and physicians' characteristics influence Ob/Gyns' advice about, and provision of, tubal ligation. Physicians were presented with a vignette in which a patient requests tubal ligation. The patient's age, gravida/parity and her husband's agreement/disagreement were varied in a factorial experiment. Criterion variables were whether physicians would discourage tubal ligation, and whether physicians would provide the surgery.

RESULTS

The response rate was 66% (1154/1760). Most Ob/Gyns (98%) would help the patient to obtain tubal ligation, although 9-70% would attempt to dissuade her, depending on her characteristics. Forty-five percent of physicians would discourage a G2P1 (gravida/parity) woman, while 29% would discourage a G4P3 woman. Most physicians (59%) would discourage a 26-year-old whose husband disagreed, while 32% would discourage a 26-year-old whose husband agreed. For a 36-year-old patient, 47% would discourage her if her husband disagreed, while only 10% would discourage her if her husband agreed. Physicians' sex had no significant effect on advice about tubal ligation.

CONCLUSIONS

Regarding patients who seek surgical sterilization, physicians' advice varies based on patient age, parity and spousal agreement but almost all Ob/Gyns are willing to provide or help patients obtain surgical sterilization if asked. An important limitation of the study is that a brief vignette, while useful for statistical analysis, is a rough approximation of an actual clinical encounter.

A seroprevalence study of poliovirus antibody among primary schoolchildren in Korea

We aimed to determine the seroprevalence of poliovirus antibody in Korea by using the cell culture neutralization method recommended by the WHO. A total of 500 sera collected from children at eight primary schools in Kyunggi province were used for this study. We found that 82.2% of children were positive for all three types of poliovirus and antibody-positive rates for types I, II and III were 94.4, 96.6 and 86.8% respectively, indicating that seropositive rates for types I and II were considerably higher than for type III (P<0.0001). This result implies that the type III component of the oral polio vaccine should be evaluated further. Although a greater number of children, including young infants, need to be tested for seroprevalence, this study still provides us with valuable information on the effectiveness of vaccination against polioviruses in Korea.

PCR-RFLP based molecular typing of enteroviruses isolated from patients with aseptic meningitis in Korea

We have evaluated PCR-RFLP as a practical method for rapid typing of enteroviruses causing aseptic meningitis in Korea. Through blind examination of 80 clinical isolates from patients with aseptic meningitis, we have compared the results of conventional serotyping with PCR-RFLP based genotyping, which was developed for this study. Among the 80 case isolates, which had been previously typed by routine neutralization test, only 42 cases (52.5%) were matched with typing by PCR-RFLP. The result clearly demonstrated that the enterovirus serotype does not coincide with the genotype. Therefore, the classification of enteroviruses by genotyping with PCR-RFLP, although rapid and simple, may be complicated by regional or seasonal differences. However, the PCR-RFLP method developed in this study is applicable to the epidemiological study of enteroviruses when regional or seasonal differences exist, and is useful in identifying the source of an infection.