• Korean Journal of Ichthyology
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• v.28 no.3
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• pp.147-155
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• 2016

This study describes the cell type, ultrastructure and histochemical characteristics as a preliminary study for the research on integument of the smooth lumpsucker, Aptocyclus ventricosus in accordance with the physiological and environmental changes using light and electron microscopes. The SEM revealed the presence of well-developed finger printing structure in the skin surface. The skin surface of the smooth lumpsucker showed an irregular folds in cross section of light microscope. Integument is composed of outer epidermal and inner dermal layer. The epidermal layer is a stratified layer composed of epithelial cells, mucous cells, vacuolar cells, and granular cells. Epithelial cells are classified into superficial, intermediated, and basal cell. The superficial cells were the squamous with well-developed microridges on the free surface, and the microridges were covered with glycocalyx. The mucous cells of unicellular gland were mainly distributed in the apical layer of epidermis and contained mucosal materials of neutral glycoprotein. The vacuolar cells of unicellular gland were mainly distributed in the mid and basal layer of epidermis. The proportion of mucous cells and vacuolar cells were $7.0({\pm}1.07)%$ and $40.6({\pm}3.31)%$ of epidermal area, respectively. The granular cells contained membrane bounded secretory granules with high electron density and developed cell organelles in the cytoplasm. The dermal layer was loose connective tissue layer and composed of mainly collagen fibers. It also contained blood vessels and chromatophores of melanophores and reflecting platelets.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.6
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• pp.478-484
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• 2004

On 11 June 1991, eggs from the brood stock of small yellow croaker (Larimichthys polyactis) were artificially fertilized using the standard dry method and were hatched. Each of the fertilized eggs (1.1-1.2 mm in diameter) had an oil globule and was transparent and buoyant. The fertilized eggs hatched in a range of water temperatures $(17.5-20.3^{\circ}C)$ 44 hrs after fertilization. The total lengths of the newly hatched larvae were 3.1-3.3 mm, and these hatchlings had 31 myotomes (10+21). Melanophores and yellow-brown chromatophores were concentrated on the head, at the ventral part of the yolk, and in the middle of the tail. Four days after hatching, the larvae completely absorbed the yolk and became flexions of 5.1-5.5 mm in total length. Fifteen days after hatching, one spine (the anterior tip of the maxillary) appeared in the upper jaw and three spines developed at the upper parts of the eyes and on the posterior part of the head. At this stage, the larvae were approximately 8.3 mm long. Thirty-nine days after hatching, juveniles (1.9-3.4 mm in total length) had a pointed tail fin. By 66 days after hatching, the juvenile fish (about 4.0-6.5 mm in total length) were similar to adult fish in body shape. The larvae of L. polyactis could be distinguished from those of L. croacea by two distinct characteristics: the large number of vertebrae (28-29), and a relatively small bony ridge on the occipital region of the head.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.5
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• pp.298-303
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• 2005

This study described the reproductive behavior and the morphological development of the larvae and juvenile of the hedgehog seahorse (Hippocampus spinosissimus). Larvae released from male seahorse were reared for 30 days in the laboratory. At the birth, the small flap-like mouth and anus of the yolk-sac larvae were open, and the yolk was completely absorbed within 1 day. The size of newborn larvae ranged 7.01-13.19mm (mean $9.26\pm1.9mm$, n=9) in TL (total length). The larvae had 15-16 pectoral fin rays and 19 dorsal fin rays, but 4 anal fin rays were not completely developed. The larval size ranged 13.38-14.38 mm (mean $13.96\pm0.3mm$, n=6) in TL at 1 day after release, and they had 17 pectoral fin rays, 20 dorsal fin rays and 4 anal fin rays when the larvae reached the juvenile stage. Juvenile size ranged 14.98-16.42mm (mean $15.84\pm0.5mm$, n=5) in TL at 3 days after release, and 1, 4, 6, 8 trunk spines extended quickly. Terminal part of the coronet became a four-forked wedge shape concurrently. Juvenile became 23.25mm (n=l) in TL after 15 days and all 11 trunk rings was connected completely. After 20 days, the juveniles were 24.66-28.65mm (mean $27.26\pm1.6mm$, n=5) in TL, and many melanophores appeared in integument. In the eye lenses, 5-6 lusters were formed. After 30 days, the juveniles were 26.78-28.26 mm (mean $27.36\pm0mm$, n=4)in TL and 8-9 lusters appeared on the eye lenses. Coronet terminal part developed to a five-forked crown-shape completely.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.1
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• pp.83-89
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• 2020

This study provides a detailed morphological description of larvae obtained from Urocampus nanus and Syngnathus schlegeli male brood fish over 20 days of culture in the laboratory. In both species, mating takes place when several males each spread their brood pouch like a wing to attract a female's attention. When the female begins to swim upward, the males follow her and receive her eggs in their brood pouches. Newborn larvae of U. nanus and S. schlegeli had already completed formation of dorsal and caudal fin rays, but not of pectoral fin rays. Pectoral fin rays were completely formed 15 days after release in S. schlegeli and 20 days after release in U. nanus. The ratio of caudal fin length to standard length increased until 8 days and decreased thereafter in S. schlegeli, while in U. nanus this ratio declined continuously after hatching. The larvae of the two species were very similar in external morphology, but well distinguished by the number of dorsal fin rays (15-16 in U. nanus vs. 39-43 in S. schlegeli), the presence of a membrane under the tail (absent in U. nanus vs. present in S. schlegeli), and the presence of melanophores in the dorsal fin (present in U. nanus vs. absent in S. schlegeli). Based on this study, U. nanus appears to be evolutionally more similar to pipefish than to seahorse.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.2
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• pp.136-143
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• 2003

The eggs of Favonigobius gymnauchen attached on the under side of a small stone were collected off Seongsan-eup Cheju-do in August, 2000 to investigate their development of egg, larvae and juveniles. The fertilized eggs were elliptical in shape (mean long axis: 1.50 mm; mean short axis: 0.57 mm) and transparent. There were filaments on one side of the egg membrane. Larvae hatched at 48 hrs 50 mins after morula stage with 25-26 myotomes in $22.8-28.5^{\circ}C\;(mean\;24.7^{\circ}C).$ The newly hatched larvae were 2.31-2.49 mm (mean 2.37 mm n=10) in total length (TL) and their mouth and anus were already opened. Their melanophores were appeared on the over gas globule, around anus and the part of caudal peduncle with 24-25 myotomes. At 4-5 days after hatching. larvae attained 3.81-4.07 mm (mean 3.96 mm, n=10) in TL and their yolk sac was completely absorbed. They began to eat rotifer and transformed to postlarvae stage. At 14 days after hatching, postlarvae attained 6.17-6.31 mm (mean 6.21 mm, n=10) in TL and their caudal notocord was flexed $45^{\circ}$ upward. At 24 days after hatching, postlarvae attained 8.69-9.10 mm (mean 8.87 mm, n=10) in TL had reached the juvenile stage. All fins were formed with the complete set of fin rays with the following counts: dorsal fin rays IV-I, 9-10; anal fin rays I, 9; pectoral fin rays 17; ventral fin rays: I, 5; caudal fin rays: 9+8= 17.

• Fisheries and Aquatic Sciences
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• v.14 no.4
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• pp.403-410
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• 2011

Scartelaos gigas is an amphibious mudskipper species that inhabits mud flats in Korea, China, and Taiwan. This fish is at risk of extinction because of its very restricted habitat and overexploitation. Information about this fish's reproductive characteristics is needed for species conservation. The sexual maturity and early life history of S. gigas were investigated through histological methods and direct observation of eggs in the wild, respectively. In total, 560 individuals of S. gigas were collected with the aid of fishermen from March 2003 to October 2003 at Jung-do Island, southwest Korea. Through microscopic observations of gonadal development, it was determined that S. gigas of both sexes were immature in April, but began to reach maturity in May, and were then fully mature by June, which was maintained until July. In August, some female fish developed early oocytes, but by September oocytes were observed to have degenerated and had been absorbed. Spawned eggs were elliptical and had an average size of 1.37 mm (long axis) by 0.69 mm (short axis). The newly hatched larvae (3.03 mm total length, TL) had an open mouth and anus, two melanophores near the anus, and one large melanophore between the 18th and 19th myomeres. The larvae (3.18 mm TL) showed absorption of the yolk and oil globule within 5 days after hatching and became prelarvae. This species should be considered vulnerable or conservation-dependent, and thus parental fish need to be protected from fishermen during the main spawning season (June).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.1
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• pp.67-73
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• 2019

We presented detailed morphological descriptions of the eggs, larvae and juvenile of Acanthaphritis unoorum based on specimens collected with bongo nets from Korean waters during the period May 2017-July 2018. We collected 18 individuals including eggs (n= 4, 0.77-0.85 mm in egg diameter), preflexion larvae (n= 6, 4.11-6.31 mm in standard length, SL), flexion larvae (n= 4, 6.60-7.82 mm SL), postflexion larvae (n= 3, 8.94-13.46 mm SL), and one juvenile (n= 1, 14.67 mm SL). The mitochondrial (mt) DNA 16S rRNA sequences of the eggs, and the cytochrome c oxidase subunit I (COI) sequences of the larvae were identical to those of A. unoorum adults (genetic distances <0.01). The A. unoorum larvae and the juvenile that we collected were morphologically similar to those of Dactylopsaron dimorphicum, but the A. unoorum specimens were readily distinguishable by the presence of lateral melanophores. This is the first record of A. unoorum in Korean waters. We propose a new Korean name for A. unoorum: "O-ri-bu-ri-nuntung-i".

• Korean Journal of Ichthyology
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• v.35 no.1
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• pp.57-63
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• 2023

Four individuals of Lipolagus ochotensis larvae (13.4~21.3 mm SL), belong to the family Bathylagidae, were collected by a Bongo net from the southern waters off Jejudo Island, Korea in February to March 2018. L. ochotensis is characterized by a elongated and compressed body, the eye stalks, series of melanophores on posterior of body, dorsal fin origin above the middle of the body. A molecular analysis based on 625 base pairs sequences in the mitochondrial DNA cytochrome c oxidase subunit I region shows that specimens were closely matched to adult L. ochotensis (genetic distance=0.024). We report the first record of family Bathylagidae, genus Lipolagus, L. ochotensis in Korean waters, and suggest their new Korean names, "Sim-hae-bing-eo-gwa", "Geom-eun-bing-eo-sok", and "Geom-eun-bbyam-bing-eo", respectively.

• Korean Journal of Ichthyology
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• v.36 no.1
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• pp.101-106
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• 2024

In May 2020, a single larval specimen (5.14 mm in total length) was collected from the southeastern sea of Jeju Island of Korea using bongo net. The specimen was identified as Lepidotrigla longifaciata based on mitochondrial DNA cytochrome c oxidase subunit I sequences. The morphological traits of the L. longifaciata larva are as follows: a long snout, a large mouth, large fan-shaped pectoral fins, and black melanophores scattered on the abdominal cavity and nape. We propose the new Korean name 'Gin-meo-ri-dal-jae' for this species, which was first discovered in Korea.

• Korean Journal of Ichthyology
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• v.11 no.1
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• pp.94-101
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• 1999

This study was conducted to observe the early life history of sea bass, Lateolabrax japonicus. The fertilized eggs were spherical in shape and turned out to be separative and floated. Their membrane and yolk having 1~5 oil globule were transparent. Fertilized eggs were measured to be 1.33~1.46 mm in diameter. Hatching of eggs were started at 74 hrs 15 mins, 54 hrs 55 mins, 50 hrs 45 mins, after fertilization in water temperature $16.0^{\circ}C$, $18.0^{\circ}C$, $20.0^{\circ}C$ respectively. The newly hatching larvae were 3.79~3.97 mm in total length with 35~37 myomeres, and mouth and anus were closed. Melanophores were distributed on the up side of head, upper jaw and margins of the body. The 5 days after hatching larvae measured 4.78~5.24 mm in total length, yolk were completely absorbed, and transformed to postlarval stage. In this time, mouth of larvae was opened, and also melanophores were presented on the lower jaw. Head of larvae grew remarkably. The 21~22 days after hatching, total length of the larvae was 7.15~8.12 mm, the caudal fin rays began to differentiation. In 31 days after hatching, the larva were 8.46~9.16 mm in total length, and tip of the caudal notochord flexed $45^{\circ}$. The larvae reached to the juvenile stage with all the fins were developed at 61 days after hatching and attained 16.28~17.31 mm in total length.