蓝身大斑石斑鱼冷冻精子(♂)与棕点石斑鱼(♀)杂交后代发育及生长特征分析

Development and Growth of Hybrid Offspring of Brown Grouper Epinephelus fuscoguttatus (♀) x Blue Speckled Grouper Epinephelus tulcula (♂) Using Cryopreserved Sperm

关键词:  蓝身大斑石斑鱼  棕点石斑鱼  杂交  胚胎发育  变态发育  成活率

Key words:  Epinephelus tulcula  Epinephelus fuscoguttatus  Crossbreeding  Embryo development  Metamorphosis  Survival rate

摘要:

蓝身大斑石斑鱼(Epinephelus tukula)和棕点石斑鱼(Epinephelus fuscoguttatus)在自然环境中存在地理分布、繁殖时间和温度等方面的生殖隔离。本研究利用蓝身大斑石斑鱼冷冻精子与棕点石斑鱼卵人工授精，在水温为30℃、盐度为20的条件下培育，对其胚胎发育、胚后变态发育进行了详细的观察，利用显微镜和解剖镜拍摄、记录胚胎发育和变态发育的形态特征和发育时序，统计了杂交受精率、孵化率和畸形率，并对鱼苗生长进行了测量。结果显示，杂交受精卵经过1037 min完成胚胎发育。原肠早期，在胚层一侧就形成了胚盾，神经管在胚孔封闭时也开始出现，在视泡和耳囊发育的同时，克氏囊(末球)也开始形成。在心脏跳动之前，胚体先开始抽动，当977 min肌节发育到23对时，心脏开始间歇性的跳动，间歇时间24~40 s，心率98次/min；发育到1018 min时，间歇时间变短，心率约为93次/min；之后间歇性现象消失，心跳频率达到93次/min，这些现象在以往鱼类胚胎发育资料中均无记载。变态发育的典型特征是三叉棘的生长和退化，杂交幼鱼3 mm (10 d)时，形成背鳍棘和腹鳍棘；全长21.5 mm (35 d)时，三叉棘退化，完成变态发育；55.3 mm (45 d)时，表型特征与成体相似。冷冻精子的受精率、孵化率和畸形率分别为(76.67±5.77)%、(85.67±5.13)%和(6.33±1.54)%，与新鲜精子无显著差异(P<0.05)。鱼苗65 d时，体长达到8.89 cm，杂交后代体色趋于一致，且生长速度快；1龄时，平均全长和体重分别达(32.58±1.60) cm和(559.76±80.85) g。对比养殖实验显示，1龄棕点石斑鱼(♀)´蓝身大斑石斑鱼(♂)杂交后代体重是棕点石斑鱼(♀)´鞍带石斑鱼(♂)杂交后代的1.63倍，全长为1.24倍；这一时期的生长方程为W=0.0311L2.8079，R²=0.9886。研究结果表明，蓝身大斑石斑鱼和棕点石斑鱼杂交胚胎和胚后发育不存在遗传障碍，后代受精率和孵化率高、畸形率低，具有生长快杂交优势，为2种石斑鱼杂交育种和苗种大量培育提供了一定的遗传基础。

Abstract:

In the natural environment, there is reproductive isolation between Epinephelus tulcula and E. fuscoguttatus due to their different geographical distribution and reproduction time and temperature. In this study, we used frozen sperm from E. tulcula and eggs from E. fuscoguttatu for artificial insemination. The fertilized eggs were incubated in water at a temperature of 30℃ and salinity of 20. The embryonic development and post-embryonic metamorphosis were observed in detail. The morphological characteristics and developmental times of hybrid offspring were observed using a microscope and dissecting mirror. We determined the fertilization rate, hatching rate, and deformity rate, and the fry growth parameters were measured. The results showed that the fertilized eggs completed embryo development 1037 maf (min after fertilization). Early in gastrula an embryonic shield was formed on one side of the germ layer, and the neural tube also began to appear when the blastopore was closed. Additionally, as the optic vesicle and the ear vesicle developed, the Kirschner's capsule (end ball) also developed. It was found that the embryoid twitch preceded the heartbeat. When the sarcomere developed to 23 pairs (977 maf), the heart began to beat intermittently at a rate of 98 beats/min and the interval of 24~40 s. The interval of the heartbeat reduced at 1018 maf with a heart rate of 93 beats/min, and then the intermittent phenomenon disappeared. These phenomena have not been documented in previously. The typical feature of metamorphosis is the growth and degeneration of the trigeminal spine. When the hybrid juvenile grew to 3 mm (10 daf, days after fertilization), it formed dorsal and pelvic pin spines. When the length reached 21.5 mm (35 daf), the trigeminal spine degenerated and the metamorphosis was complete. When hybrid juveniles grew to 55.3 mm (45 daf), their phenotypic characteristics were similar to that of the adult. The fertilization rate, hatching rate, and malformation rate of the frozen sperm were (76.67±5.77)%, (85.67±5.13)%, and (6.33±1.54)%, respectively, and there was no significant difference in these parameters when compared to those of fresh sperm (P<0.05). At the 65 daf, the body length of hybrid fry reached 8.89 cm. Then, the offspring of the hybrids tended to be more consistent in body color and they grew very fast. The average body length and body weight of hybrid fish were (32.58±1.60) cm and (559.76±80.85) g at one year old. By contrast farming, the weight of E. fuscoguttatus♀ × E. tulcula ♂ was 1.63-fold of E. fuscoguttatus♀ × E. lanceolatus♂, and the total length of E. fuscoguttatus♀ × E.tulcula♂ was 1.24-fold of E. fuscoguttatus♀ × E. lanceolatus♂. The growth equation in this period was W=0.0311L2.8079, R²=0.9886. The results suggest that there is no genetic disorder in the hybrid embryos and post-embryonic development between E. tulcula♂ and E. fuscoguttatus♀. The offspring showed high fertility and hatching rate, but low malformation rate. Moreover, the offspring showed heterosis of rapid growth. The study provides a genetic basis for hybrid breeding and seed cultivation of these two grouper species.