Masculinizing Effects of Chrysin-Loaded Poloxamer Micelles on Siamese Fighting Fish

Siamese fighting fish (Betta splendens) are freshwater fish that are commonly found in Thailand and other Southeast Asian countries. In the present study, chrysin-loaded polymeric micelles (CPs) were developed and investigated for the masculinizing effects, survival rate, growth indices, and toxicity on Siamese fighting fish. CPs were prepared using a poloxamer. The micelle system of CPs that were formed at a chrysin-to-polymer ratio of 1:2 was found to be the most suitable monodispersed system and exhibited a nanosized diameter (74.2 ± 1.6 nm) with a narrow size distribution (0.288 ± 0.012). In vivo studies were performed using Siamese fighting fish larvae as animal models. In the in vivo toxicity study, the fish larvae were immersed in aqueous systems containing CPs that had five different chrysin concentrations of 1, 10, 100, 1000, and 10,000 ng/mL for 24, 48, and 72 h. Blank polymeric micelles and water were used as controls. The in vivo masculinization effect of CPs with different chrysin concentrations on the fish larvae was evaluated after 5 weeks of exposure. The results demonstrated that CPs with a chrysin concentration of 1000 ng/mL showed a masculinization effect of 94.59 ± 2.76% with a high fish larvae survival rate of 72.45 ± 5.09% and low toxicity. It was concluded that the developed CPs had a significant effect on the sex reversal of Siamese fighting fish larvae with a high survival rate.

ẢNH HƯỞNG CỦA HORMONE 17α - METHYLTESTOSTERONE BỔ SUNG VÀO THỨC ĂN LÊN TĂNG TRƯỞNG, CHIỀU DÀI CÁC VÂY, TỶ LỆ SỐNG VÀ TỶ LỆ ĐỰC HÓA CỦA CÁ LIA THIA (Betta splendens Regan, 1910)

Cá lia thia hay cá xiêm đá (Betta splendens) là một loài cá cảnh nước ngọt đặc trưng được nuôi làm cảnh hoặc giải trí thông qua hình thức chọi cá. Nghiên cứu này nhằm tìm ra liều lượng hormone 17α - Methyltestosterone (17α - MT) thích hợp bổ sung vào thức ăn để nâng cao tỷ lệ đực của cá lia thia. Cá bột sau khi hết noãn hoàng cho ăn thức ăn có bổ sung hormone 17α - MT liên tục trong 21 ngày với liều lượng 0, 20, 40 và 60 mg 17α - MT/kg thức ăn, tương ứng với nghiệm thức NT1, NT2, NT3 và NT4. Cá giống được nuôi tiếp tục đến 60 ngày tuổi để xác định tăng trưởng, tỷ lệ sống và tỷ lệ chuyển giới tính trên cá. Kết quả cho thấy tăng trưởng và tỷ lệ sống thì khác biệt không có ý nghĩa thống kê giữa các nghiệm thức (p>0,05). Tỷ lệ đực và chiều dài các vây ở NT3 cao hơn có ý nghĩa thống kê so với NT1 và NT2 (p<0,05), tuy nhiên khác biệt không có ý nghĩa thống kê so với NT4 (p>0,05). Nghiệm thức NT3 đạt tỷ lệ đực hóa (93,8%), hiệu suất đực hóa (84,6%) cao nhất và khác biệt có ý nghĩa thống kê giữa các nghiệm thức (p<0,05). Nghiên cứu này cho thấy bổ sung hormone 17α - MT vào thức ăn với liều lượng 40 mg 17α - MT/kg sẽ làm tăng tỷ lệ cá lia thia đực. ABSTRACT Lia thia fish commonly called the Siamese fighting fish (Betta splendens) is a specific freshwater aquarium fish, which raising as pet or for entertainment through fish fighting. This study aimed to find out the appropriate dosage of 17α - Methyltestosterone (17α - MT) hormone supplemented into feed to enhance masculinization rate of Siamese fighting fish. Frys after completing yolk digestion were fed with 17α - MT supplemented feed continuously for 21 days at dose of 0, 20, 40 and 60 mg 17α - MT per kg of feed, respectively treatment of NT1, NT2, NT3 and NT4. Fingerlings were kept being grown for up to 60 days of age to determine the growth, survival and transsexual rates on fish. The results showed that growth and survival rates of fish were not significantly different among treatments (p>0.05). Male rate and the fin lengths of fish in treatment of NT3 were statistically higher than those treatment of NT1 and NT2 (p<0.05); however, there were not significant difference compared to treatment of NT4 (p>0.05). Masculinization rate (93,8%) and masculinizing efficiency (84,6%) in treatment of NT3 were highest and there was statistically significant difference among the treatments (p<0.05). This research showed that supplement of 17α - MT into the feed at a dose of 40 mg 17α - MT per kg of feed increased the rate of male Siamese fighting fish.

CẢI TIẾN VIỆC ĐỰC HÓA CÁ XIÊM (Betta splendens Regan, 1910) BẰNG CÁCH NGÂM TRONG 17α-METHYLTESTOSTERONE

Cá xiêm (Betta splendens) 1 ngày tuổi được đực hóa bằng cách ngâm trong túi polyethylene chứa 17α-methyltestosterone (17α-MT) ở các nồng độ 2,5; 5,0 và 7,5 mg/L có bơm oxy (thể tích oxy: thể tích nước bằng 2:1), mật độ 150 con/L trong 4 giờ. Kết quả cho thấy, tỷ lệ đực và đực hóa tăng khi tăng nồng độ hormone, với nồng độ 2,5 mg 17α-MT/L cá đạt tỷ lệ đực, tỷ lệ đực hóa là 88,89% và 78,26%. Nồng độ 5,0 mg 17α-MT/L và nồng độ 7,5 mg 17α-MT/L đạt tỷ lệ đực, tỷ lệ đực hóa là 100%. Khác biệt không có ý nghĩa (p>0,05) về tăng trưởng chiều dài và khối lượng của cá xiêm. Tỷ lệ sống 60 ngày sau khi nở là 54 - 89,89%, tỷ lệ sống giảm khi tăng nồng độ hormone 17α-MT trong nước ngâm. Kết quả cho thấy, nồng độ 2,5 mg 17α-MT/L là liều tối ưu để áp dụng chuyển đổi cá xiêm đực. Nồng độ 2,5 mg 17α-MT/L cá đạt tỷ lệ sống, hiệu suất đực hóa cao nhất là (86,22%, 76,81%). Với nhiều ưu điểm như đơn giản, chi phí thấp và có thể áp dụng ở mọi nơi nên có thể sản xuất cá xiêm đực bằng cách áp dụng phương pháp ngâm cá trong hormone 17α-MT với nồng độ 2,5 mg/L để đạt hiệu quả kinh tế tối ưu cho người nuôi. ABSTRACT The siamese fighting fish (Betta splendens) at one day old were masculinized by immersion in a polyethylene bag containing 17α-methyltestosterone (17α-MT) at concentrations of 2,5; 5,0 and 7,5 mg/L with oxygen pump (volume oxygen: water volume is equal to 2:1), density is 150 fish/L in 4 hours. The results showed that the male and masculinization ratios increased when the hormone concentration was increased, with a concentration of 2,5 mg 17α-MT/L, the male rate and masculinisation rate was 88,89%, and 78,26% respectively. Concentration of 5,0 mg 17α-M/L and concentration of 7,5 mg 17α-MT/L reached the male rate, the masculinization rate was 100%. The difference was not significant (p>0,05) in terms of length and weight growth of siamese fighting fish. The survival rate of 60 days after hatching was 54 - 89,89%, the survival rate decreases when the concentration of 17α-MT hormone in immersion water increases. The results showed that, concentration of 2,5 mg 17α-M/L was the optimal dose for converting male siamese fighting fish. Concentration of 2,5 mg 17α-MT/L, fish achieved the highest survival rate, masculinization efficiency respectively rate (86,22%, 76,81%). With many advantages such as simplicity, low cost and applicability everywhere, it is possible to produce male siamese fighting fish by applying the method of immersion fish in the hormone 17α-MT with a concentration of 2,5 mg/L to achieve efficiency economic efficiency optimal for farmers.

Timing of isolation from an enriched environment determines the level of aggressive behavior and sexual maturity in Siamese fighting fish (Betta splendens)

Background Teleost fish are known to respond to environmental manipulation, which makes them an ideal model animal for testing relationships between the environment and behavior. The Siamese fighting fish, Betta splendens, is a solitary, highly territorial fish that displays fierce stereotyped aggressive behavior toward conspecifics or members of other species. Adult fish, especially males, are generally housed in isolation in captivity. Here we report evidence that an enriched rearing environment can decrease the level of aggression in bettas and enable adults to be housed in groups. Results B. splendens individuals were hatched in our laboratory and raised in groups in an enriched environment. At the juvenile or subadult stage, some individuals were relocated to a poor environment and kept in isolation. To evaluate aggression, a mirror-image test was conducted at the juvenile, subadult, and adult stages for each fish, and body parameters as well as plasma concentrations of 11-ketotestosterone, estradiol, and cortisol were evaluated. Male and female adult bettas raised in a group showed lower levels of aggression than other adult fish. The magnitude of threatening behavior was greater in adult bettas isolated as subadults, whereas the magnitude of fighting behavior was grater in adult bettas isolated as juveniles. The influence of rearing conditions on behavior was greater in females than in males. Plasma cortisol concentrations of adult bettas isolated as subadults after the mirror-image test were higher than those in other experimental groups. Adult males isolated as subadults had significantly higher plasma concentrations of 11-ketotestosterone than males raised in a group and isolated as juveniles. Females isolated as subadults had a higher gonadosomatic index than females raised in a group and females isolated as juveniles. Conclusions These results indicate that bettas can be kept in a group under enriched environments and that the timing of isolation influences the aggression and sexual maturity of bettas. Female and male bettas responded differently to environmental manipulation. Judging from their level of sexual maturity, bettas isolated as subadults show proper development.

Genomic consequences of domestication of the Siamese fighting fish

Siamese fighting fish, commonly known as betta, are among the world's most popular and morphologically diverse pet fish, but the genetic processes leading to their domestication and phenotypic diversification are largely unknown. We assembled de novo the genome of a wild Betta splendens and whole-genome sequenced multiple individuals across five species within the B. splendens species complex, including wild populations and domesticated ornamental betta. Given our estimate of the mutation rate from pedigrees, our analyses suggest that betta were domesticated at least 1,000 years ago, centuries earlier than previously thought. Ornamental betta individuals have variable contributions from other Betta species and have also introgressed into wild populations of those species. We identify dmrt1 as the main sex determination gene in ornamental betta but not in wild B. splendens, and find evidence for recent directional selection at the X-allele of the locus. Furthermore, we find genes with signatures of recent, strong selection that have large effects on color in specific parts of the body, or the shape of individual fins, and are almost all unlinked. Our results demonstrate how simple genetic architectures paired with anatomical modularity can lead to vast phenotypic diversity generated during animal domestication, and set the stage for using betta as a modern system for evolutionary genetics.