Marbled Sole Pleuronectes Yokohamae Research Articles

Genetic variation and population structure of marbled sole Pleuronectes yokohamae and cresthead flounder P. schrenki in Japan inferred from mitochondrial DNA analysis

Nucleotide sequence analysis in the first half of the mitochondrial control region was used to estimate genetic variation and population structure of marbled sole Pleuronectes yokohamae and cresthead flounder Pleuronectes schrenki, obtained from 10 localities in Japan. Overall estimate of pairwise population FST and NJ tree suggested genetic distinction between P. yokohamae and P. schrenki. SAMOVA also demonstrated two distinct genetic groups of the samples, MS (marbled sole, Honshu and southernmost Hokkaido) and CF(cresthead flounder, Hokkaido), which was pertinent to the natural range of P. yokohamae and P. schrenki, respectively. However, the haplotypes common to P. yokohamae and P. schrenki were found in all four samples of the CF group and two of six samples of the MS group. Haplotype and nucleotide diversities were high within MS and CF groups, and the mismatch distribution analysis showed a bimodal profile in both groups, suggesting secondary contact between allopatrically evolved MS and CF groups. Thus, the observed haplotype sharing between two species might have been the consequence of interspecific hybridization after their divergence. In addition, FST estimates and Mantel test suggested that the population structure of P. yokohamae might have been influenced by low or restricted gene flow with isolation by distance, whereas no such population structuring was implied for P. schrenki. The observed difference in population structuring between two species was surmised by the difference of migration character.

서해 꽃게 자망의 망목 선택성 연구

A series of fishing experiments were carried out in the western coastal waters of Korea from May, 2006 to September, 2007, using gill nets of different mesh sizes (m=101, 121.8, 152.5, 176.8, and 191 mm) to determine the mesh selectivity of gill net for swimming crab, Potunus trituberculatus. The catch species was composed of swimming crab (87%), Thomas's rapa whelk Rapana venosa (5%), arthritic neptune Neptunea cumingi (2%), Japanese swimming crab Charybdis japonica (2%), marbled sole Pleuronectes yokohamae (1%), pen shell Atrina pectinata, ocellate spot skate Okamejei kenojei, and so on. The carapace length (CL) of each swimming crab caught in the experimental nets was measured. Sponge crab (egg-bearing female crab) was appeared from the end of June to August in the coastal waters. The master selection curve was estimated by applying the extended Kitahara's method. The selection curve showed that the gill nets of larger mesh size allowed more crabs of small carapace size to escape. The optimum value (CL/m) was 0.645 and the CL/m was estimated to be 0.301, 0.354, 0.391, 0.422, and 0.450 when the retention probabilities were 0.1, 0.2, 0.3, 0.4 and 0.5, respectively.

Developmental Changes in Diel Feeding Activity and Estimation of Daily Food Consumption in Hatchery-reared Larval and Juvenile Marbled SolePleuronectes yokohamae

Developmental Changes in Diel Feeding Activity and Estimation of Daily Food Consumption in Hatchery-reared Larval and Juvenile Marbled SolePleuronectes yokohamae

Seasonal distribution, age, growth, and reproductive biology of marbled sole Pleuronectes yokohamae in Tokyo Bay, Japan

The seasonal distribution, age, growth and reproductive biology of marbled sole Pleuronectes yokohamae (Gunther) from Tokyo Bay, Japan were studied. A clear seasonal distribution trend was observed, with P. yokohamae limited to the south of the bay in summer and expanding almost throughout the bay in other seasons. The formation and dynamics of hypoxic areas in the bay limited the northward distribution of P. yokohamae in summer. Age was determined by counting growth rings on otoliths; maximum ages were found to be 5 years for males and 6 years for females. The mean back-calculated length for females at each estimated age was greater than that for males. Growth of males and females was shown by the von Bertalanffy growth equations. Reproductive biology was studied on the basis of gonadosomatic indices and histological sections of gonads. The spawning season lasted from November to March, peaking in December and January. Sixty per cent of males at 1 year and all males ≥2 years had mature testes, whereas 6.7% of females at 1 year, 58.3% of females at 2 years, and all females ≥3 years had attained maturity.

Lethal effects of nonylphenol on fertilized eggs and larvae of marbled sole Pleuronectes yokohamae

Lethal effects of nonylphenol on fertilized eggs and larvae of marbled sole Pleuronectes yokohamae

Spatial distribution and feeding habits of the shrimp Crangon uritai as a predator on larval and juvenile marbled sole Pleuronectes yokohamae

: To examine predation on larval and juvenile Pleuronectes yokohamae by Crangon uritai, the spatial distribution and feeding habits of C. uritai were studied. Crangon uritai fed on various prey, including P. yokohamae. Density-dependent predation on juvenile Crangon spp., larval and juvenile gobiid fish Chaenogobius heptacanthus, mysids, and gammarids was observed. The abundance of alternative prey might, therefore, play an important role in reducing the pressure of predation on P. yokohamae. In each year, C. uritai migrated from depths of 10 m in March to depths of 3 m in May. There was a significant negative correlation between the weighted mean depth (WMD) of C. uritai and the weighted mean bottom water temperature (WMBWT). The migration was, therefore, delayed in the cold spring, during which C. uritai occupied depths of approximately 10 m. In contrast, no significant correlation was found between the WMD of P. yokohamae and WMBWT. Settlement of P. yokohamae began at depths of 15 m, mainly during early April. The spatial distributions of these two organisms show greater overlap during the cold spring, resulting in increased opportunities for predation.

Sound pressure values in the audiogram of marbled sole Pleuronectes yokohamae measured in air

: It has been reported that sound pressure values in the audiogram of marbled sole, which do not have swim bladders, are as low as those of fish that have swim bladders when the audiogram was measured in water using two air loudspeakers to eliminate the water displacement. In the present experiment, sound pressure values in the audiogram of 10 marbled sole Pleuronectes yokohamae were determined using sinusoidal sound pressure as a stimulus to fish removed from water. Sound pressure values in the audiogram obtained by the present method were higher than those obtained in water. This difference was presumably due to inner ear or lateral line sensitivity to water displacement around the center of the water tank.

Histopathological Changes Probably Associated with a Virus in Larval and Juvenile Marbled Sole Pleuronectes yokohamae

The seed production of marbled sole Pleuronectes yokohamae has been attempted at a hatchery in Kagawa Prefecture, Japan since 1989, while a subacute disease with a considerable amount of mortality occurred in larval and juvenile fish (24-69 days old) in 1989, 1990, 1991, 1997 and 2001. Diseased fish displayed edema, an abdominal distension due to ascites, and exophthalmia. The outbreak of the disease usually continued for 1 month or longer and the cumulative mortality was often over 40%. The evident histopathological features were the formation of multinuclear syncytia and following necrosis in the liver, renal tubules, pancreas and intestinal epithelium, and hemorrhage in the brain, choriocapillaries, stomach and skin. Electron microscopy of affected hepatocytes revealed formation of inclusion bodies consisting of crystalline arrays of virus particles (75-80 nm in diameter). These results suggest that the pathognomonic sign of the present disease is necrosis accompamied by the syncytial formation which would be associated with a virus infection.

Development of Time-Resolved Fluoroimmunoassay for Vitelline Envelope Protein Precursor, Choriogenin, in Marbled Sole Pleuronectes yokohamae

Development of Time-Resolved Fluoroimmunoassay for Vitelline Envelope Protein Precursor, Choriogenin, in Marbled Sole Pleuronectes yokohamae

マコガレイの背景雑音によるマスキング

Using a classical cardiac conditioning technique, the auditory thresholds of marbled sole Pleuronectes yokohamae were measured in the presence of masking noise in the spectrum level range of 70-90dB re 1μPa/√Hz. Critical ratios (signal-to-noise ratio) were approximately 27dB at 60-100Hz and 32-58dB at 150-700Hz. The ratio increased almost linearly with increasing frequency. The noise spectrum level at the start of masking was 62-70dB within the frequency range of 60-700Hz. This suggests that hearing of the marbled sole is masked in the natural environment with the noise spectrum level above 70dB.

マコガレイの聴覚しきい値について

The auditory thresholds for 10 specimens of the marbled sole Pleuronectes yokohamae were determined by heartbeat conditioning using pure tone stimuli of 9 frequencies from 60 to 1, 000Hz, which were coupled with an electric shock. The marbled sole could hear sound in the frequency range from 60 to 1, 000Hz, and the lowest threshold was 92.5dB re 1μPa at 100Hz. Hearing ability declined rapidly with increasing frequency above 300Hz, but little difference occurred in hearing ability between 400 and 500Hz. The results show that the auditory thresholds of marbled sole are higher and its sensitive frequency range is narrower than that for fish that have swimbladder.