• Development and Reproduction
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• v.22 no.1
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• pp.39-53
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• 2018

The purpose of this study is to investigate the early life history of the Rhodeus fish, Rhodeus uyekii and R. ocellatus, in the Nakdong River to use as the preliminary data for the systematic study. The embryos used in the study were fertilized eggs (embryo) and larvae after artificial fertilization. The long diameter of the eggs of the R. uyekii was 3.39-3.97 mm (average $3.68{\pm}0.41mm$, n=30) and the short diameter was 1.36-1.55 mm (average $1.45{\pm}0.13mm$, n=30). The long diameter of the eggs of the R. ocellatus was 2.53-2.71 mm (average $2.62{\pm}0.12mm$, n=30) and the short diameter was 1.47-1.60 mm (average $1.53{\pm}0.09mm$, n=30). Hatching time was 48 hours for the R. uyekii and 50 hours for the R. ocellatus given that the average water temperature was $21.5^{\circ}C$. The hatched larvae were 4.95-5.00 mm (average $4.98{\pm}0.04mm$, n=5) for the R. uyekii and the total length was 3.66-3.69 mm (average $3.67{\pm}0.02mm$, n=5) for the R. ocellatus. R. uyekii was found to be 15.5-15.8 mm at total length (average $15.6{\pm}0.21mm$, n=5) on the 56 days after hatching with the number of dorsal fins being ⅲ-9, anal fins ⅲ-10, ventral fins ⅲ-5. The R. ocellatus was found to be 15.8-16.0 mm (average $15.9{\pm}0.14mm$, n=5) at total length on the 58 days with the number of dorsal fins being ⅲ-11, anal fins ⅲ-12 and ventral fins ⅲ-5 where the number of all fin stalks reached maximum.

• Ocean and Polar Research
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• v.42 no.4
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• pp.303-311
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• 2020

In this study, the embryonic development and hatchability of eggs fertilized by the reciprocal hybrids of kelp grouper (Epinephelus bruneus) and red-spotted grouper (E. akaara) were evaluated with the goal of establishing a novel hybrid with enhanced growth and viability during the farming period in the temperate waters of Korea. The fertilization rates were lower for hybrids than for maternal purebreds and were significantly higher in the red-spotted grouper ♀ × kelp grouper ♂ hybrid (RGKG, 89.61 ± 1.58%) than in the kelp grouper ♀ × red-spotted grouper ♂ hybrid (KGRG, 74.82 ± 4.23%, p < 0.05). Unlike the fertilization rates, the hatching rates of fertilized eggs were similar between hybrids and maternal purebreds and did not differ significantly between KGRG and RGKG (72.74 ± 3.60% vs. 75.23 ± 2.20%, respectively, p > 0.05). The embryonic development of the hybrids was similar to that of maternal purebreds; however, irregular cleavage and asymmetric blastoderm were noticeable in the developing eggs of KGRG hybrids. The deformity rates of newly hatched larvae were higher in hybrids than in maternal purebreds and were significantly higher in KGRG than in RGKG (17.47 ± 1.28% vs. 7.11 ± 0.54%, respectively, p < 0.05). These results demonstrate the potential to produce viable larvae from these two hybrids. Although the production efficiency of KGRG was lower than that of RGKG, the fertilization, hatching, and deformity rates make both hybrids useful for further comparative studies regarding economic aspects.

• Korean Journal of Ichthyology
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• v.34 no.1
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• pp.16-24
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• 2022

The eggs development and early life history of Sarcocheilichthys variegatus wakiyae was investigated. The adult fishes were collected in Yeongsangang River, Damyang-gun, Jeollanam-do, Korea, and their spawning inducement was carried by sex maturation hormone (Ovaprim) injections. Spawning amount was mean 31±3.5 Mature eggs were cicular in shape and mean 2.40±0.05 mm in diameter. Hatching period of the embryo was 230 to 240 hours after fertilization under water temperature of 22℃. The newly hatched larvae were 10.7±0.19 mm in total length (TL). 3 days after hatching, postlarvae was measured 12.0±0.13 mm in TL and the tip of the caudal fin was bent at 45°. 11 days after hatching, it was measured 14.6±0.13 mm in TL, and transferred to juvenile as the number of fins (iii7 dorsal fin, iii6 anal fin, i7 ventral fins) reached a constant number of each part.

• Development and Reproduction
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• v.11 no.2
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• pp.121-125
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• 2007

Morphological changes on digestive tract were observed using Flounder, Paralichthys olivaceus to elucidate the early developmental processes. Hatched larvae, ($2.50{\pm}0.14\;mm$ in total length: TL) has not opened its mouth and anus. The digestive tract showed linear tubular form from mouth to anus extending along with yolk. On $7{\sim}8$ days from hatching, the post-larvae, ($5.05{\pm}0.40\;mm$ TL) has developed digestive tract and activated for feeding. The digestive tract expanded into dorsal side, joined to intestine, and the stomach began to develop. The digestive tract was divided into an anterior and posterior region, and began to differentiate. In the post-larvae($6.50{\pm}0.25\;mm$ TL) on $13{\sim}14$ days from hatching, the digestive tract twisted one cycle in the anterior region, the area was expanded. The digestive tract was completely differentiated into oesophagus, anterior intestine, middle intestine, posterior intestine and arranges fundamental structure. In the embryo($12.40{\pm}0.55\;mm$ TL) after 30 days from hatching, stomach became large and could be distinguished from cardia and pyloric parts apparently. The digestive tract developed similar with that of adult flounder showing clear division of stomach, anterior intestine, middle intestine, posterior intestine and rectum. In the embryo($16.15{\pm}0.85\;mm$ TL) after 40 days from hatching, esophagus, pyloric part, anterior intestine, middle intestine, and rectum have largely expanded, and thus the morphological features are somewhot different with those of post-larvae flounder.

• Journal of Aquaculture
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• v.11 no.2
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• pp.203-212
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• 1998

As seed production program is growing prosperously in various fishes in southern Korea, disease problems in larval and juvenile stages have emerged as a new research object. The following results were obtained from investigation about environmental factors related to mass mortalities of young Kinki red seabream, Pagrus major in process of artificial seedling production. Total length of red seabream larvae hatched was 2.93mm, and became 18.83~20.12mm at day 40. The first noticeable mortality of red seabream larvae (7.98~9.37mm) occurred in 25~30 day-old fish with the survival rates of 59.8~60.3%. Thereafter the mortality of larvae decreased, survival rate was 20.5~25.45% in day 40. After 20~30 days, the quality of pond water was bellow II class. During the experimental period COD, $PO_4$-P, $NO_2$-N, $NO_3$-N and $NH_$-N increased up to 3, 7, 34, 6 and 8 times, respectively, compared to initial ones. The number of viable bacteria in pond water and seabream larvae were $6.3{\times}10^6$~$2.3{\times}10^7$ cfu/ml, 4.3~$7.4{\times}10^6$ cfu/g in day 25, respectively. Among the isolated bacteria from the diseased red seabream in day 25, Vibrio spp. was considered to be the causative organism. External symptoms of this disease were floated, spined near the surface and inflated abdomen. When the isolated strain of the Vibrio was bathed to seabream larvae, $LD_50$ of seabream larvae was over $10^6$ cfu/ml of Vibrio spp.

• Journal of Aquaculture
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• v.20 no.3
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• pp.160-167
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• 2007

Embryonic and pre-leptocephalic larvae development of the eel, Anguilla japonica, are described following natural fertilization in the indoor tank of $23^{\circ}C$ water temperature. Following a routine hormone treatment technique for the brood stock, female eels were artificially matured by weekly intramuscular injections of salmon pituitary extracts (SPE) at a dosage of 20 mg/kg body weight (BW) for a total of 10-14 doses to induce ovarian maturation, while male eels received weekly intramuscular injections of human chorionic gonadotropin (HCG) at a dosage of 1 IU/g BW for a total of 6-10 doses to induce testicular maturation in a separate aquarium and induced natural spawning. Fertilized eggs of about 1.0 mm in diameter were pelagic and showed a typical discoidal cleavage. Hatching occurs 38 hrs after fertilization at a water temperature of $23^{\circ}C$. The newly hatched larvae measured about 3.0 mm in total length and the number of myomeres averages 42. Their mouths and anuses were opened at 4.5 days and the yolk sacs of the pre-leptocephalic larvae were almost absorbed at 6.5 days after hatching. Pre-leptocephalic larvae survive for 14.5 days. At this time they are $5.87{\pm}0.25mm$ in total length and have about 98 myomeres. However, morphological characterization of embryonic and pre-leptocephalic larvae were not different between natural fertilization and artificial fertilization by the dry method.

• Korean Journal of Ichthyology
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• v.13 no.1
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• pp.74-84
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• 2001

The early developmental stages, growth and morphological changes of the Korean bullhead, Pseudobagrus fulvidraco, were studied from a series of reared specimens. Details of the early developmental stages are illustrated with special reference to morphological transformations. Egg and sperm of Korean bullhead were obtained from mature adults under hormonal treatment, fertilized artificially, and incubated in the aquarium. The incubation period of fertilized eggs was 55 to 66 hours at a temperature of 24.9${\pm}$0.34$^{\circ}$. Larvae were fed successively with Artemia salina and Daphnia magna for 2 to 15 days and artificial food after 20 days. Fertilized eggs were adhesive and spherical with a diameter of 2.04mm(n = 100). The mean total length of newly hatched larvae was about 4.92${\pm}$0.33 mm. Mouth opening occurred on one-day-old yolk-sac larvae, and initial feeding was observed on the third day after hatching. The morphological transitions from larvae to juvenile and juvenile to young stages occurred when the fish reached about 17 mm in total length (about 13days after hatching) and about 32 mm in total length (about 30 days after hatching), respectively. Many changes in proportion of body parts to total length were observed at about 7~8 mm and 30~32 mm, corresponding to the transformations from larvae to juvenile and from juvenile to young, respectively. In comparing relative growth of each body part against total length, those characteristics related to head parts showed positive growth in the pre-larval stages, while those concerning mobile abilities showed positive growth in the post-larval stage.

• Parasites, Hosts and Diseases
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• v.36 no.2
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• pp.99-108
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• 1998

The present study was performed to check the viability of eggs, filariform larvae and adults of Strongvloines venezueLensis exposed to various conditions for an in vitro maintenance. The eggs in the feces remained viable for about 25 days at $4^{\circ}C$ and 15 days at room temperature. However, the isolated eggs in sterile saline lost their viability within 24 hr at $4^{\circ}C$. The eggs in morula stage were very sensitive to air drying and rapidly lost their viability (=12 hrs. Filariform larvae survived for a maximum period of 45 days in fecal suspension and 28 days in 0.12% nutrient broth in polyvinyl culture bags maintained at $20^{\circ}C$. On the other hand, those isolated from nutrient broth cultures survived for a maximum period of 32 days in tap water and 22 days in sterile saline at $20^{\circ}C$. The mature adult worms obtained from experimentally infected rats survived maximally for 9 days in serum supplemented (10% rat-serum) 0.12% nutrient broth and 4 days in serum free nutrient broth at $37^{\circ}C$ while the culture media were changed at an alternate day. The adult female worms deposited fertile eggs in serum supplemented and serum free nutrient broth cultures, however, the hatched larvae (Ll) were not able to develop to the filariform stage in the culture media and found to die within 24 hr of maintenance. The present findings on an in vitro maintenance of different stages of 5. uenezueLetis may provide useful information for biological and biochemical studies with Strongyloines species. Key words: Strongvloides venezuelensis. viability in vitro maintenance, free-living filariform larvae (L3), embryonation of eggs

• Korean Journal of Ichthyology
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• v.35 no.1
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• pp.10-19
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• 2023

This study aimed to examine the early life history of Trident goby (Tridentiger brevispinis) by observing their egg development and juvenile fish morphology. The average size of mature eggs was 1.13~1.41 (1.30±0.07) mm (n=30), and 0.70~0.86 (0.79±0.04) mm (n=30) in long diameter and short diameter, respectively. The incubation period at 24±1℃ ranged from 167~228 h. The newly hatched larvae measured 2.31~2.78 (2.51±0.18) mm (n=30) in total length (TL), and their mouth and anus were not yet open. At 3 days after hatching, the preflexion larvae reached 2.84~3.10 (2.98±0.10) mm in TL, where in their yolk absorption was complete and their mouths began to open. At 19 days after hatching, the larvae reached the flexion stage, measuring 4.02~4.62 (4.36±0.19) mm in TL. The tip of their notochord was bent upward. At 30 days post-hatching, the larvae reached the postflexion stage, measuring between 5.04~6.36 (5.76±0.51) mm in TL, with the tip of the caudal fin bent at 45°. After 54 days, the larvae had reached the juvenile stage, measuring between 7.43~9.84 (8.48±0.90) mm in TL, and were differentiated by their constant number of fins (6 first dorsal, 12 second dorsal, 11 anal, and 10 ventral fins). This study found that T. brevispinis had larger fertilized eggs and a greater number of myotomes in hatching larva than similar species. Additionally, the distribution of melanophores in T. brevispinis was distinct from that in other similar species, making it easy to distinguish them morphologically.

• Korean Journal of Ichthyology
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• v.36 no.1
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• pp.1-9
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• 2024

This study investigated the early life history of the Boleophthalmus pectinirostris living in the southern coastal Yeoja-man and compared the results with the same Gobiidae fishes. The brood stork used in the study were captured with bare hands in the tidal flats of Beolgyo-eup, Jeollanam-do, in June 2015. The amount of spawning was 411~11,688, and the eggs were short oval and the size was 1.40×0.72 mm. The time of hatched took 91 hours and 35 minutes at a water temperature of 25~27℃. Newly hatching larvae, the yolk sac had a total length of 3.02~3.31 (average 3.17±0.08, n=30) mm and did not eat rotifer. 4 days after hatching, the total length was 3.31~3.52 (3.43±0.07, n=30) mm, and as the mouth and anus opened, the fish transitioned to the preflexion larvae and fed. 14 days after hatching, the total length was 5.06~5.25 (5.16±0.06, n=30) mm, and the distal end of the vertebra was completely bent at 45° and the transitioned to the postflexion larvae. 41 days after hatching, the total length was 14.3~16.8 (15.4±0.85 mm, n=30), and the number of fins reached an integer of 5 first dorsal fins, 26~27 second dorsal fins, 24~27 anal fins, and 6 ventral fins, and the transitioned to the juveniles. As a result of the study, star-shaped melanophore were deposited from the front of the pectoral fin to the base of the caudal fin, which distinguished them in form from other postflexion larvae of Gobiidae fishes.