Sung Hwoan Cho

Optimum temperature and salinity conditions for growth of green algae Chlorella ellipsoidea and Nannochloris oculata

The effects of temperature and salinity on growth of green algae Chlorella ellipsoidea and Nannochloris oculata were determined to compare the optimum culture conditions. A four-temperature (15, 20, 25, and 30°C) × three-salinity (10, 20, and 30) factorial design with triplicates was applied. Specific growth rate (SGR), maximum density, and duration to reach maximum density of C. ellipsoidea were significantly affected by both temperature and salinity. The highest SGR was observed in C. ellipsoidea at 25°C and salinity 10, but the maximum density was very low. The highest maximum density was achieved in C. ellipsoidea at 15°C and 10. The slope constant of the linear relationship between semilogarithmic growth of C. ellipsoidea and day of culture was highest at 15°C and 10. The SGR and duration to reach maximum density of N. oculata were significantly affected by both temperature and salinity. However, maximum density of N. oculata was significantly affected by temperature, but not salinity. The highest maximum density was achieved in N. oculata at 25°C and 30, but SGR was significantly lower than that of N. oculata at 25°C and 10. The slope constant of the linear relationship between semilogarithmic growth of N. oculata and day of culture was highest at 25°C and 30. Based on these results, the condition of 15°C and salinity 10 seemed to be optimal for maximum density of C. ellipsoidea, and the condition of 25°C and 10 and 30 for SGR and maximum density for N. oculata, respectively.

Sex differentiation and hormonal sex reversal in the bagrid catfish Pseudobagrus fulvidraco (Richardson)

Abstract Sex differentiation of the bagrid catfish Pseudobagrus fulvidraco (Richardson) is described from hatching to the 100th day post-hatch (water temperature 25 °C). Primordial germ cells (PGCs) were observed on the 3rd day post-hatch (0.78 cm total length (TL), 0.006 g body weight (BW)), and began to protrude into the peritoneal cavity from the 8th day post-hatch (1.17 cm TL, 0.02 g BW). On the 12th day post-hatch (1.46 cm TL, 0.06 g BW), initial ovarian differentiation was identified by the PGCs with condensed chromatin, and their transformation into meiotic oocytes. Oocytes were in the secondary and tertiary yolk stages on the 100th day post-hatch (10.04 cm TL, 11.38 g BW). While ovaries gradually grew after sex were differentiated, testes continued to multiply from the 20th day post-hatch (2.30 cm TL, 0.24 g BW) when testicular differentiation was first identified. On the 100th day post-hatch (9.84 cm TL, 12.79 g BW), testes contained spermatocytes exhibiting meiotic activity, spermatozoa and cyst cells. Therefore, the sex differentiation type of the bagrid catfish is identified as gonochoristic. Effect of oral administration of either estradiol-17β (5–40 ppm) or tamoxifen (25–200 ppm) for 20 days (from 3rd to 20th day post-hatch) on mortality and growth of the bagrid catfish was studied. Estradiol-17β treatment at the concentration of 400 ppm successfully produced 100% females; however, estradiol-17β treatment induced mortality seemingly related to dose-dependent. Estradiol fashion did not affect growth of the bagrid catfish at doses of 0–20 ppm ( P >0.05), but significant growth depression occurred at 40 ppm ( P P >0.05). The combined results of oral administration with estradiol-17β and tamoxifen suggest that these hormones be effective for sex reversal in the bagrid catfish and the labile period of sex differentiation fall between the 8th and 30th day post-hatch.

Compensatory growth and body composition of juvenile black rockfish Sebastes schlegeli following feed deprivation

Compensatory growth, feeding rate, feed efficiency and chemical composition of juvenile black rockfish (mean weight 1.43 g) were investigated for 35 days after a 14-day feed deprivation treatment under four feeding conditions: one group continuously fed (control) and the other three groups fasted for 5 days (F5), 10 days (F10) and 14 days (F14). All fasted fish were re-fed from day 15. Only F5 achieved the same body weight as the control, indicating that complete compensation occurred in F5. The specific growth rate (SGR) of F5 was the highest at day 21 and then decreased thereafter, showing higher values than the control at days 21, 28 and 42. In contrast, although SGRs of F10 and F14 were higher than that of the control during the whole refeeding period except day 21, they did not catch up the control in body mass, indicating that only partial compensation occurred in F10 and F14. The feeding rate (FR) of all groups except F14 changed in a pattern similar to SGR (Spearman’s rank correlation, rs>0.9), suggesting that SGR varied depending on FR. Similar feeding efficiencies (FEs) were found in the four groups and they did not vary significantly during the whole refeeding period, suggesting that FE was not the factor affecting SGR. At day 14, the ratios of lipid to lean body mass in F10 and F14 were lower than those in the control and F5, and there was no difference between the control and F5. At day 49, however, only F14 showed a lower value than the other three groups, and there was no difference among the three groups. These results indicate that juvenile black rockfish fasted for 5–14 days can exhibit compensatory growth after refeeding, but timing and degree vary depending on the duration of feed deprivation.

Effects of starvation on morphometric characteristics of olive flounder, Paralichthys olivaceus

An experiment was conducted for 12 weeks to determine the effect of feeding and starvation on truss and classical parameters in the external body of olive flounder, Paralichthys olivaceus. There was an increase in the truss dimension of body depth in the trunk region of the fed group at the end of the experiment (P < 0.05). In the olive flounder, the trunk region dimensions, including body depth measurements, are likely to be compromised by variability related to differences in the feeding of fish from different habitats. Classical dimensions in relation to the anterior–posterior body axis decreased and classical dimensions of head characteristics increased upon starvation but decreased upon feeding (P < 0.05). These results suggest that these morphometric parameters may be a useful index of nutritional status in olive flounder.

Effect of the Formulated Diets on Performance and Resistance of Juvenile Abalone [Haliotis discus (Reeve, 1846)] Subjected to Various Stress Conditions

ABSTRACT Performance and stress resistance of juvenile abalone (Haliotis discus) fed formulated diets substituting fish meal (FM) and macroalgae (MA) with soybean meal and rice bran, respectively, was compared with the MA under various stress conditions. Four experimental diets (Standard, FM50, FM50 + MA50, and FM50 + MA100 diets) were prepared in duplicate. The dry MA (Undaria pinnatifida and Laminaria japonica)were also prepared to compare with the effects of formulated diets on the performance of abalone to achieve the industry standard. About 84,000 juvenile abalone were distributed into twelve 5-ton tanks (7,000 abalone per tank). The diets were fed to abalone once a day to satiation. At the end of the 16-wk feeding trial, abalone were subjected to various stress (air exposure, sudden salinity, and temperature changes) conditions and cumulative mortality was monitored. Weight gain and specific growth rate of abalone fed the all formulated diets were higher than the dry MA. The cumulative mortality of abalone fed the MA was higher than that of abalone fed the all formulated diets at the end of observation after sudden salinity and temperature changes. In conclusion, the well-formulated diets produced better growth performance of abalone over the dry MA. Abalone subjected to the various stress conditions after being fed with all formulated diets, except for abalone fed with the Standard, FM50, and FM50 + MA50 diets after air exposure, were more resistant than those fed the MA.

Effects of Dietary Scutellaria baicalensis Extract on Growth, Feed Utilization and Challenge Test of Olive Flounder ( Paralichthys olivaceus )

Effects of dietary Scutellaria baicalensis extract (SBE) on growth, feed utilization and challenge test of olive flounder (Paralichthys olivaceus) were determined. Six hundred thirty fish averaging 5.0 g were distributed into 18, 180-L tanks. Six experimental diets were prepared in triplicate: SBE-0, SBE-0.5, SBE-1, SBE-2, SBE-3 and SBE-5 diets containing SBE at the concentrations of 0, 0.5, 1, 2, 3 and 5%, respectively. Fish were hand-fed to apparent satiation twice a day for 8 wks. At the end of 8-wk feeding trial, ten fish from each tank were infected by Edwardsiella tarda for challenge test. Survival and weight gain of fish were not affected by dietary concentrations of SBE. However, specific growth rate of fish fed the SBE-2 diet was higher than that of fish fed the SBE-0, SBE-1, SBE-3 and SBE-5 diets. Neither feed efficiency nor serum chemical composition of fish was affected by dietary concentrations of SBE. The cumulative mortality of fish fed the SBE-0 diet was 100% at 96 h after E. tarda infection, but 77 to 87% for fish fed the other diets. Dietary inclusion of 2% SBE appears to be recommendable to improve specific growth rate of fish and SBE had the potential to mitigate mortality of fish at E. tarda infection.

Morphometric and Histological Changes in Cyprinid Loach, Misgurnus anguillicaudatus, in the Early Growth Period

In this study, we measured the morphometric and histological changes in the cyprinid loach, Misgurnus anguillicaudatus, during the early period of growth. Eyes, yolk length, yolk height, and yolk volume of the larva decreased for 16 days post hatching (DPH) (P<0.05). During 60 DPH (P>0.05), the most anterior extension of the head × the posterior end of the supraoccipital, the most anterior extension of the head × the origin of the dorsal fin, the most anterior extension of the head × the origin of the pectoral fin, the posterior end of the supraoccipital × the origin of the pelvic fin, and the origin of the dorsal fin × the ventral origin of the caudal fin gradually decreased, whereas the most anterior extension of the head × the dorsal origin of the caudal fin, the origin of the dorsal fin × the origin of the anal fin, the origin of the dorsal fin × the origin of the pectoral fin, and the insertion of the dorsal fin × the origin of the pelvic fin gradually increased (P<0.05). In the cyprinid loach, the retina is composed of six layers: the epithelial layer, ganglion cell layer, inner nuclear layer, inner plexiform layer, outer limiting membrane, and rod and cone layer (RCL). After hatching, part of the RCL gradually increased in density. The kidney and midgut epithelium were already formed in the cyprinid loach just after hatching and grew gradually in subsequent days.

Effects of Dietary Carbohydrate Sources on Growth and Body Composition of Juvenile Abalone (Haliotis discus, Reeve)

ABSTRACT A 16-wk feeding trial was conducted to assess the effects of different types of dietary carbohydrate on growth and body composition of juvenile abalone (Haliotis discus). A total of 1,680 abalone were randomly distributed among 24 containers (70 per container) and fed one of eight diets, including seven experimental diets containing different types of carbohydrates, including dextrin (DT), glucose (GC), corn starch (CS), α-cellulose (CL), maltose (MT), sucrose (SC), and wheat flour (WF), and Undaria to compare effect of experimental diets. Water stability of the diets was measured 12, 24, and 48 h after seawater immersion. Water stability of the diets was different over all periods of time and their significant interaction was also observed. Survival was not significantly affected by diet. Weight gain and specific growth rate were greatest in abalone fed on the CL diet. Shell length, width, height, and soft body weight were greatest in abalone fed the CL diet, followed by the WF, DT, SC, CS, GC, and MT diets and Undaria. Weight gain, specific growth rate, crude protein, and crude lipid contents of the soft body of abalone fed on the experimental diets were greater than those fed on Undaria. This study shows that CL is the most effective carbohydrate source for improving growth of this species of juvenile abalone and practically applicable in formulating abalone feed.

Morphogenesis of the Eye of Brown Croaker (Miichthys miiuy)

Eye growth and lens diameter of brown croaker Miichthys miiuy were positively allometric between hatching and 180 days post-hatch (d.p.h.). Eye growth in relation to head length and head height was nearly isometric. Eyes were formed completely at 14 d.p.h. At this age, the eye has a crystalline lens, an optic nerve fiber layer, a ganglion cell layer, an inner plexiform layer, an inner nuclear layer, an outer plexiform layer, an outer nuclear layer, an outer limiting membrane, and a pigment epithelium. The essential demands that must be met by the retina in this species pertain to light sensitivity and spatial resolution.

Lidocaine hydrochloride–sodium bicarbonate as an anesthetic for soft‐shelled turtle Pelodiscus sinensis

Attempts were made to understand how the different sizes (mean body weight of 4.1±0.8 g for small and 182.6±23.7 g for large) of the soft-shelled turtle Pelodiscus sinensis are affected by different temperature (25°C or 30°C), and different concentrations (700, 1000 and 1300 p.p.m.) of anesthetic lidocaine hydrochloride-sodium bicarbonate. The soft-shelled turtles were fed to satiation once daily. Three-way anova design (size × temperature × concentration of lidocaine hydrochloride) with duplicate was used. Twenty each of large and small soft-shelled turtles were distributed into six 30-L tanks. Exposure time of the soft-shelled turtle was affected by all factors (temperature, concentration and size). Exposure time of the soft-shelled turtle for anesthetizing decreased with increase in temperature and in concentration of lidocaine hydrochloride, and decrease in size. Recovery time for the soft-shelled turtle was also affected by all factors. Recovery time of the soft-shelled turtle increased with increase in temperature, concentration of lidocaine hydrochloride, and size. According to these results, lidocaine hydrochloride (1000 p.p.m.)-sodium bicarbonate seemed an effective anesthetic for sedating and handling the soft-shelled turtle. However, when an anesthetic is recommended for wide use, especially on commercially important edible organisms, the time organism takes to metabolize and excrete anesthetic chemicals from its body to a safe level must be given to allow fitness for human consumption.