Genetic variability comparison of cultured Israeli carp (Cyprinus carpio) from Korea using microsatellites.

In aquaculture, cultured fish often undergo continuous cross-fertilization without any inflow of new broodstock. This lowers genetic diversity, leading to increased disease rates and decreased survival rates. To improve the mass production and easy culture of Israeli carp, it is essential to investigate the population structure and genetic diversity of these fish. However, such a survey has not yet been performed on Korean Israeli carp. In this study, we used seven microsatellite markers to analyze the genetic diversity and association of cultured Israeli carp from Korea and China. The average numbers of alleles per locus (N A ) for two Korean (KorA and KorB) and two Chinese (ChA and ChB) populations were as follows: KorA (10.42), KorB (14.43), ChA (20.57) and ChB (20.71). The expected heterozygosity (H e ) ranged from 0.672 to 0.897 and from 0.827 to 0.938 in the Korean sample and Chinese sample respectively. The genetic diversity of the Korean Israeli carp was about half that of the Chinese carp. The diversity of the Korean Israeli carp was very low, suggesting that the immunity of this population could be weak, and that diversity-recovery studies are urgently needed. Therefore, our results may therefore form the foundation for future research efforts towards genetic monitoring and selective breeding, continuous research needs to be conducted in order to recover the genetic diversity of the Korean Israeli carp.

Morphometric Characteristic between Diploid and Spontaneous Triploid Carp in Korea.

We used flowcytometry to ploidy verification after that investigate difference between diploid and spontaneous triploid through the truss dimension and classical dimension at crucian carp, Carassius auratus, crucian carp C. cuvieri and common carp, Cyprinus carpio collected from Hangang river, Hantangang river, Imjingang river, Geumgang river, Yeongsangang river and Nakdonggang river, Korea. There were significant differences among the three species for the truss dimensions anterior origin of dorsal fin (2)× anterior origin of anal fin (5), 2× anterior origin of pelvic fin (6), 2× origin of pectoral fin (7), posterior origin of dorsal fin (3)×5, 3×6, and 3×7 (P<0.05). There were no significant differences among the three species in the truss dimensions dorsal fin length (2×9) and eye diameter (ED)(P>0.05). On the other hand, there were no significant differences in the several classical dimensions of each species (P>0.05). Three classical dimensions, most anterior extension of the head (1)×2, 1×6 and 2× most posterior scale in lateral line (4) did not differ between the C. auratus diploid and spontaneous triploid (P>0.05). Two classical dimensions, 1×6 and longest length between most anterior extension of the head and gill cover (1×8) did not differ between the C. cuvieri diploid and spontaneous triploid (P>0.05). One classical dimensions, 1×2 did not differ between the common carp diploid and spontaneous triploid (P>0.05). There were significant differences in the each diploid and triploid species (P<0.05). These results suggest that the classification of each species and classification between diploid and spontaneous triploid morphometrical parameters used in this study are useful indices of morphometrical status in the each species from major river of Korea.

Growth Comparison of Israeli Carp (Cyprinus carpio) to Different Breeding Combination.

The purpose of this study was to investigate the improvement of growth in Israeli carp (Cyprinus carpio), and the cross experiment was carried out with two strains of Israeli carp. Four combinations of Israeli carp from Jeonbuk fisheries farm and Songpu mirror carp from Heilong Jiang, China (KK; Jeonbuk ♀ × Jeonbuk ♂, KC; Jeonbuk ♀ × China ♂, CC; China ♀ × China ♂ and CK; China ♀ × Jeonbuk ♂) were developed and reared. Body length, body weight and condition factor were determined at 20, 40, 60 and 170 days post-hatch (DPH). The results showed that there were differences in growth rate of the four groups. Body length of four groups were CK > CC > KC > KK and body weight were CC > CK > KC > KK at 170 DPH. The growth perfomance of four groups were statistically significant difference (P<0.05). During the rearing, CC group had longer length and higher weight at 170 DPH compared to other three groups and also condition factor was highest in the CC group, but there was no significant difference in a survival rate. These results indicated that the growth performance mainly depended upon brooder combination but survival rate could not significantly affect brooder.

Gonadogenesis and Sex Differentiation in the Korean Rose Bitterling, Rhodeus uyekii).

This report describes the sex differentiation of the Korean rose bitterling, Rhodeus uyekii, from hatching to 170 days post-hatch (DPH) in relation to total length (TL), body weight (BW), and integral water temperature (IWT). The growth curve of TL from just hatching to 83 DPH was 5.144e0.045t (R² = 0.961; t, time), and that of BW was 2.398e0.086t (R² = 0.725). Primordial germ cells (PGCs) were observed at 17 DPH (7.9 mm TL, 3.74 mg BW, 374°C IWT), and thereafter began to protrude into the peritoneal cavity. At 21 DPH (9.2±0.14 mm TL, 4.8±0.07 mg BW, 462°C IWT), some PGCs contained condensed chromatin and oocyte were observed in meiotic prophase. In contrast to the ovaries, which grew gradually after sexual differentiation, testes began multiplying at 25 DPH (10.1 mm TL, 5.42 mg BW, 550°C IWT), when testicular differentiation was first identified, and multiplied continuously thereafter. At 33 DPH (11.2 mm TL, 10.5 mg BW, 726°C IWT), the developing testes contained spermatogonia that exhibited mitotic activity. No spermatocyte or sperm cell was observed until 83 DPH (18.9 TL, 48.2 mg BW, 1,826°C IWT). At 170 DPH (32.5 mm TL, 270.1 mg BW, 3,740°C IWT), which was the end point of this study, the mature ovaries showed germinal vesicle breakdown, while the mature testes contained observable spermatocytes and sperm cells. These results allow us to identify the sex differentiation type of the Korean rose bitterling as differentiated gonochoristic.

Comparison of Cell and Nuclear Size Difference between Diploid and Induced Triploid in Marine Medaka, Oryzias dancena.

The influence of triploidization on cell and nucleus size characteristics of the same tissues of erythrocyte, retina, kidney, hepatocyte and midgut epithelium in marine medaka, Oryzias dancena has been determined histologically. Induced triploid fish are produced by cold shock treatments. Likewise, the size of horizontal cell nucleus in inner nuclear layer of retina, ganglion cell nucleus in ganglion cell layer of retina, proximal tubule cell of kidney, hepatocytes and nuclear height of midgut epithelium all appear to be significantly larger than diploid (p<0.05). On the other hand, retina thickness is larger in diploid than induced triploid (p<0.05). Induced triploid shows low density of cell number. Results of this study suggest that same characteristics in the induced triploid exhibiting larger cells and nucleus sizes with fewer number of cells than the diploid can be useful criteria for the distinction between diploid and induced triploid, and also the ploidy level in marine medaka.

Expression of Immune-Related Genes during Loach (Misgurnus anguillicaudatus) Embryonic and Early Larval Development.

Early life stage mortality in fish is one of the problems faced by loach aquaculture. However, our understanding of immune system in early life stage fish is still incomplete, and the information available is restricted to a few fish species. In the present work, we investigated the expression of immune-related transcripts in loach during early development. In fishes, recombination-activating gene 1 (RAG-1) and sacsin (SACS) have been considered as immunological function. In this study, the expression of the both genes was assessed throughout the early developmental stages of loach using real-time PCR method. maRAG-1 mRNA was first detected in 0 dph, observed the increased mostly until 40 dph. Significant expression of maRAG-1 was detected in 0 to 40 dph. These patterns of expression may suggest that the loach start to develop its function after hatching. On the other hand, maSACS was detected in unfertilized oocyte to molura stages and 0 to 40 dph. maSACS mRNA transcripts were detected in unfertilized oocytes, suggesting that they are maternally transferred.

Stimulation of Spermiation by Human Chorionic Gonadotropin and Carp Pituitary Extract in Grass Puffer, Takifugu niphobles.

Spermiation was stimulated in the mature grass puffer, Takifugu niphobles, with an injection of human chorionic gonadotropin (HCG) or carp pituitary extract (CPE). Spermatocrit and sperm density were reduced, but milt production was increased in both the HCG and CPE treatment groups relative to those in the control group (P <0.05). These results should be useful for increasing the fertilization efficiency in grass puffer breeding programs.

Morphometrical Changes on Korean Rose Bitterling, Rhodeus uyekii, in Early Growth Period.

We investigated the process of yolk absorption in Korean rose bitterling, Rhodeus uyekii, and determined the changes in its morphometric characteristics. The R. uyekii from 1 days post hatching (DPH) to 21 DPH, the eye diameter (ED) was 5.4 at 5 DPH. Thereafter, the ED/total length (TL) ratio increased to 10.7 at 21 DPH (p<0.05). The yolk length (YL) decreased from 95.4 to 1.1 by 21 DPH, and this rate of decrease was greater than that for any other dimension (p<0.05). 12 morphometric dimensions/TL for the R. uyekii were measured at each sampling day from 21 DPH to 170 DPH. At just hatching, the average TL and BW were 6.1±0.09 mm and 4.9±0.07 mg, respectively. At 53 DPH, the average TL was 12.9±0.28 mm and the average BW was 14.7±0.72 mg; the total length growth equation was TL=5.507e(0.038t) (R (2)=0.916). Further, the body weight growth equation was BW=3.3647e(0.0296t) (R (2)=0.9354). The dimensions with regard to body depth showed the greatest growth rates in the external characteristics of the fish (p<0.05). The patterns of the morphometric characteristics measured in this study can be classified in three ways. The patterns were shown to be increased (y=0.0992x+ 12.07, R (2)=0.8333), decreased (y=-0.0569x+42.029, R (2)=0.8395) or maintained (y=0.005x+18.263, R (2)=0.3678) from 21 DPH to 170. These results will provide useful indices for the successful rearing of the R. uyekii.

Comparative Analysis of the Morphometric Changes in Ussurian bullhead, Leiocassis ussuriensis, and Korean bullhead, Pseudobagrus fulvidraco, in the Early Period of Growth.

Morphometric changes in the Ussurian bullhead, Leiocassis ussuriensis, and the Korean bullhead, Pseudobagrus fulvidraco, were observed during the early period of growth. Yolk length, yolk height, and yolk volume in the two species decreased within 9 days post-hatching (DPH) (p<0.05). The body lengths and body heights of both species increased gradually to 150 and 130 DPH, respectively (p<0.05). The horizontal distance between the anteriormost extension of the head and the anterior insertion of the pectoral fin, the anteriormost extension of the head × the verticality position of the anterior insertion of the primary dorsal fin rays, and the anterior insertion of the primary dorsal fin × the anterior insertion of the pectoral fin were greater in the Korean bullhead than in the Ussurian bullhead (p<0.05). However, the relative sizes of the head region, pectoral fin, ventral fin, and anal fin were greater in the Ussurian bullhead than in the Korean bullhead (p<0.05), and relative body depth and the size of the outer-mandible barbel were greater in the Korean bullhead than in the Ussurian bullhead (p<0.05). The growth curves of the morphometric characteristics of both species were divided into three types.

Induced Morphological Changes in Larval Rock Bream, Oplegnathus fasciatus, under Starvation.

Morphological changes in the reared rock bream, Oplegnathus fasciatus, from hatching to six days after hatching were examined during the early growth stage under starvation. All the larvae died within five days when feeding was delayed for three days after hatching. These results imply that initial larval food should be supplied within two days of hatching. Changes in the pectoral angle and the ratios of eye height to head height, gut height to standard length, and gut height to myotome height in the rock bream are alternative indicators for the identification of starving fish. These indicators might prove useful in evaluating the successful transition from endogenous to exogenous feeding in this species.

Comparative Analysis of Histological Changes in Ussurian Bullhead, Leiocassis ussuriensis, and Korean Bullhead, Pseudobagrus fulvidevrepaco, in the Early Period of Growth.

The histological changes in the Ussurian bullhead, Leiocassis ussuriensis, and the Korean bullhead, Pseudobagrus fulvidevrepaco, were observed during the early period of growth. The retinas size of both species increased in the 9 days post-hatching (DPH) (p<0.05). In the just-hatched Ussurian bullhead, the retina already consisted of six layers: the epithelial layer, ganglion cell layer, inner nuclear layer, inner plexiform layer, outer limiting membrane layer, and rod and cone layer. The Korean bullhead had the same components. At 50 DPH, the thickness of the retina was 538.0±7.19 µm in the Ussurian bullhead and 558.9±9.44 µm in the Korean bullhead. The relative thickness of each layer of the retina did not differ significantly in the two species. Although the growth of the Korean bullhead's retina was faster, the relative thickness of each layer in the retina did not change during early development. After hatching, some parts of the tissue gradually became denser. Immediately after hatching, the kidney and midgut epithelium of the Ussurian bullhead and Korean bullhead were already formed and grew gradually thereafter. From 0 DPH to 30 DPH, the nuclear height in the midgut epithelium did not differ significantly between the two species, but at 50 DPH, it was 11.4±2.45 µm in the Korean bullhead and 9.9± 2.13 µm in the Ussurian bullhead. During the experimental period, the major axes, minor axes, surface areas, and volumes of the proximal tubule cells in the kidney did not differ significantly between the two species. Thus, the early histological development of the Ussurian bullhead is similar to that of the Korean bullhead.