| In this paper, the development of early life and appendicular skeleton about Tanakiachii and Tanakia himantegus were examined in larvae and juveniles which wereartificially fertilized and hatched. The results are as follows:Newly hatched larva of T. chii contained a substantial amount of yolk, with paleyellow in color and tiny tubercles on the surface. On day3, a pair of hilly projections ofyolk expanded toward both sides of the body, and the primordial fin-fold at the caudalportion developed. Optic cups developed into circular at day6. Lens and melaninpigments began to form on the optic cups at day8. At day11, the mouth formed andbrain developed, and melanophores were observed on the body. On15days old larvae,the branchial groove and anus had developed, the base of dorsal fin and anal fin formed,and caudal fin rays formed at the lower lobe. At day21, the boundary of the head andtrunk was clear, the gas-bladder divided into anterior and posterior lobes. The numbersof the dorsal fin and anal fin were8and10respectively. Even thought the larvae stillhad partial yolk-sac left, it started to eat to replenish energy, and the larvae began freeswimming since then. During day31to day36, rudiments of the pectoral fin appearedas small membranes, some rays were formed in the pelvic fin. The caudal fin changedfrom a truncated to a deep forked shape. In66days old juvenile, scales appeared on thebody and a black longitudinal line appeared on the middle and latter part of body. Sincethen, the fish always swam as a cohort.Newly hatched larva of T. himantegus contained a substantial amount of yolk, withpale yellow in color and tiny tubercles on the surface. The larva were usually stationaryin the bottom of dish. On day3, a pair of hilly projections of yolk expanded toward bothsides of the body, and the primordial fin-fold at the caudal portion developed. And thelarva had intermittent creep phenomena. Optic cups developed into circular at day5,and auditory vesicles possessed two pairs of otoliths. The brain had been formed at day7. Lens and melanin pigments began to form on the optic cups at day9. At day14, the branchial groove and gas-bladder had developed. The anus had developed and it didn’tconnect to the outside environment. At day17, the caudal fin rays forked. Eye pigments,both melanin and guanine, were heavily concentrated. At day20, the upper and lowerjaws were approximately equal in size. The pectoral fins commenced to move. At day21, the boundary of the head and trunk was clear, the gas-bladder divided into anteriorand posterior lobes. The larva were now able to swim actively with well-balancedorientation for much longer than before. Even thought the larvae still had partialyolk-sac left, it started to eat to replenish energy.36days, the height were larger than21days old larvae. The operculum had developed and completed covered the gill.Rudiments of the ventral fins emerged as small membranes. Dorsal and anal fins hadcompleted developed and caudal fin developed into forked shape. There were melanindistributed on the caudal, dorsal and anal fins.The appendicular skeleton of T.chii and T.himantegus were studied aftercartilage-teleost double staining:(1)Vertebrae and Weberian organ. The vertebrae number of Tanakia chii and Tanakiahimantegus were32and34, respectively. Both were20caudal vertebra. The larvawhich before10days only had a straight notochord both of T.chii and T.himantegus.The neural spines and veins spine had formed at day13, and there were parapophysis inthe front of the notochord, the ventral ribs were also developed. The vertebrae of T.chiiand T.himantegus were developed at day17and day19, respectively. At day36, therewere7supraneural at the front of the notochord of T.chii compared T.himantegus’6.And the vertebrae of T.chii and T.himantegus were both almost ossified from front toback of the notochord. The timing of T.chii’s scaphium and tripus developed weresimilar to himantegus. At day36, the Weberian apparatus of T.chii and T.himanteguswere almost complete developed and didn’t ossified yet.(2)The dorsal and anal support bones. At day13, the dorsal and anal cartilage supportbones had developed. At day17, the cartilage pterygiophore of T.chii had developed,and at day19, the cartilage pterygiophore of T.himantegus had developed. At day66,the spines and rays had formed, the support bones had ossified while thepterygiophore didn’t ossified yet.(3)The caudal support bones. At day8, the hypural had formed in both T.chii andT.himantegus. At day13, there were2or3epural bones,5hypural bones and one Phy. The Phy and Hy1were combined at the base.(4)The pectoral support bones. The developed process of pectoral of T.chii andT.himantegus were similar. The time of cleithrum, cartilage spealbone and cartilagesupport bone developed were similar. At day19, the cartilage support bones werefractured. Then, there were pterygiophore on the fractured bones and a hole on thespealbone. At day66, the hole were much bigger.(5)The pelvic support bones. The developed process of pelvic of T.chii andT.himantegus were similar. At day36, the pelvic support bones were formed. Then, twocartilage pterygiophore bones had developed at the end of support bones. At day66, thepelvic bones were almost finish the development.Based the above results, there were no obvious morphology difference on the earlystage of T.chii and T.himantegus. And the number of vertebrae and supraneural betweenT.chii and T.himantegus were obvious different. Both of them, the sensing organ,feeding, breathing and swimming apparatus had developed well about21days while thelarvae had a few yolk-sac left and started to eat to replenish energy. We believe that thetiming of larva swim out the mussel is about21days. At day66, the support bones ofT.chii and T.himantegus were both ossified from front to back of the notochord, whilethe scale appeared on the surface. It means the begin of juvenile. The character of thedevelopment of early life and appendicular skeleton about T.chii and T. himantegusprovides basis scientific evidence for the classification of the Acheilognathinae fish. |
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