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Salinity tolerance and nursing performance under different densities in spotted scat Scatophagus argus Linnaeus, 1766
(2023-05-01)
Yangthong, Monsuang
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Suratata, Montathip
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Nontaso, Adjakab
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Ruensirikul, Jirayuth
;
Kaneko, Gen
Spotted scat Scatophagus argus is a euryhaline species generally nursed in brackish water and shipped to freshwater ponds or sea cages of local farms in Thailand. To find the best practice for this process in terms of survival and cost, we conducted two culture experiments. In experiment 1, spotted scat fries (up to 6.72 ± 2.15 g) were divided into 5 size classes (S1–S5), and their survival rates were determined after 4 patterns of salinity changes [from 0 to 30 parts per thousand (ppt), from 0 to 15 ppt, and vice versa]. The survival rates were not significantly different between groups when fries were transferred from or to 15 ppt water. However, smaller fries (S1–S3) presented lower survival rates than larger fries (S4 and S5) when transferred from 0 to 30 ppt. In experiment 2, fries (0.21 ± 0.05 g) were nursed at three densities (125, 250, and 500 fish/m3) using underground water without water changes for 80 days. The 125 and 250 fish/m3 groups showed similar culture performance, suggesting that the nursing density can be up to 250 fish/m3 under these conditions. These results provide empirical data for establishing the best nursery practice of spotted scat, which will be particularly useful for small-scale farmers.
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Optimisation of dietary protein level for rearing juvenile spotted scat (Scatophagus argus Linnaeus, 1766)
(2023-01-01)
Yangthong, Monsuang
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Pangsakun, Yaowapa
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Ruensirikul, Jirayuth
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Kaneko, Gen
An 8-week feeding trial was conducted to determine the optimum dietary protein level for growth, feed utilisation, chemical composition and amino acid profile in juvenile spotted scat (Scatophagus argus). Five isoenergetic diets containing 31.70, 35.39, 40.71, 45.88 and 51.48% crude protein (T1–T5 respectively) were formulated and fed to triplicate groups of S. argus (4.92 ± 0.06 g, n = 15 for each group). The percent weight gain (WG), specific growth rate (SGR) and average daily gain (ADG) showed significant quadratic response to dietary protein level with the highest values observed in the T4 group. The feed conversion ratio (FCR) and feed intake (FI) showed significant quadratic response to the dietary protein level, with the highest efficiency in the T3 and T4 groups. Crude protein and most amino acid levels increased with increasing dietary protein. The optimum dietary protein level for tested parameters of this species amounted to 41-45%. However, WG, SGR, ADG, FCR and FI showed subtle and/or insignificant differences between the dietary protein levels of 35.39 and 45.88% (T2–T4 groups). These results suggest that diets containing ~35% protein can be a practical and cost-effective option for rearing juvenile spotted scat.
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The Hot-Water Extract of Sargassum sp. as a Feed Ingredient for Spotted Scat (Scatophagus argus Linnaeus, 1766) Reared in Songkhla Lake: Effects on Growth, Feed Efficiency, Hematological Data and Body Composition
(2022-08-01)
Yangthong, Monsuang
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Ruensirikul, Jirayuth
;
Kaneko, Gen
The growth performance of Scatophagus argus (25.53 ± 0.89 g) reared in Songkhla Lake, a brackish lagoon, was evaluated after feeding isonitrogenous and isocaloric diets containing hot-water extract from a seaweed, Sargassum sp., at 0, 0.25, 0.50, 0.75 or 1 g·kg−1. Triplicate groups of fish were reared in 15 net cages (50 × 50 × 60 cm) at a density of 20 fish per cage, and the diets were fed twice a day at a rate of 5% of fish body weight per day for 8 weeks. The final body weight, weight gain (WG), average daily gain, and feed intake (FI) showed significant positive and quadratic responses to the Sargassum extract level. The highest WG (57.97%) and FI (0.34) were recorded in the fish that received the hot-water extract at 0.25–0.5 g·kg−1 of diet. The protein efficiency ratio showed significant positive linear and quadratic responses to the Sargassum extract level, while the hepatosomatic index showed a significant positive linear response to the Sargassum extract level. The body protein and ash contents showed positive, linear and quadratic responses to the Sargassum extract level, and the highest crude protein (49%) was observed in the 0.5 g·kg−1 diet group. There were no significant effects of the Sargassum extract levels on feed conversion ratio, food conversion efficiency, lipid and moisture contents, survival rate, hematocrit, and white or red blood cell counts. However, hematological data between fish in the control group and the Sargassum extract groups tended to be different. Overall, the optimum level of seaweed-extract supplementation for spotted scat under natural conditions was determined to be approximately 0.5 g·kg−1 diet.
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Systemic organization of tetraponera rufonigra (Jerdon, 1851) hymenoptera: Formicidae): Histological observation
(2020-01-01)
Somala, Naphat
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Senarat, Sinlapachai
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Para, Chamnan
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Jiraungkoorskul, Wannee
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Kaneko, Gen
Tetraponera rufonigra Jerdon, 1851, is one of the most dangerous ants, whose apex of gaster region contains a sting structure with a complex venom gland. Here, we describe the systemic organ system of T. rufonigra using histological techniques. The venom gland of T. rufonigra was located above the mesentero-proctodeal region, which could be histologically classified into two parts; the venom gland reservoir and the venom gland tubes. The venom gland tubes were lined by a simple cuboidal epithelium, whereas the venom gland reservoir was enclosed with simple squamous epithelium. The pygidial gland was localized near the cuticle as clusters, and each of the oval shape pygidial gland cells contained a spherical nucleus surrounded by acidophilic cytoplasm. High magnification observation showed that the integumentary system consists of three layers; epicuticle, exocuticle, and endocuticle. The digestive system was a single narrow tube consisting of the foregut, midgut, and hindgut. Five to six rectal papillae were found in the hindgut. The urinary system was made up of Malpighian tubules, which lined with simple cuboidal epithelium and tracheal embedded in the adipose tissue. The respiratory system was composed of spiracles and trachea adjacent to the integument, all of which were surrounded by a simple squamous epithelium. In the nervous system, several ganglia were found in this study. There were two layers in each ganglion: Outer cortex and inner medullar layers. Several cell types were observed in the cortex layer including the neurosecretory cells, the neuroglia, and neurons. The outcomes of this study could provide a useful basis for future research on the family Formicidae.
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