Establishing intraspecific breeding and hybridization programs and determining genetic variability are two important issues for aquaculture. However, interspecific hybridization to improve growth and feeding efficienc...Establishing intraspecific breeding and hybridization programs and determining genetic variability are two important issues for aquaculture. However, interspecific hybridization to improve growth and feeding efficiency is limited. For this purpose, the embryonic and larval development of reciprocal crosses of Clarias gariepinus (Burchell, 1822) and Clarias jaensis (Boulenger, 1909) were studied under laboratory conditions. The fertilization rate varied from 63.33% to 92%, while the hatching rate ranged from 55.68% to 76% with the highest value in hybrids ♀Cg × ♂Cj. Crosses between ♀Cj × ♂Cj, ♀Cg × ♂Cj and ♀Cj × ♂Cg had embryonic stages similar to those of the pure sib ♀Cg x ♂Cg. All crosses, however, had different timing for the various embryological stages. Hatching occurred at 32 h 15 min and 38 h for ♀Cj × ♂Cj and ♀Cj × ♂Cg, and 23 h and 23 h 30 min, respectively, for ♀Cg × ♂Cg and ♀Cg × ♂Cj. However, both crosses produced viable larvae until the first external feeding. The external morphological features of the larvae were completely formed by the 10th day after hatching. The body forms of the crosses at this time were indistinguishable from the pure sib. This study thus laid the groundwork for further comparative studies on hybrid performance and characterization.展开更多
Although information about embryonic and larval development of garpike,Belone belone(Linnaeus,1761),is present in the published literature,the bulk of research concerns garpike from the northeastern Atlantic Ocean and...Although information about embryonic and larval development of garpike,Belone belone(Linnaeus,1761),is present in the published literature,the bulk of research concerns garpike from the northeastern Atlantic Ocean and the Baltic Sea.The present work describes the embryonic and larval development of garpike,Belone belone,from the Adriatic Sea,and methods used for incubation of fertilized eggs in aquarium conditions.Because garpike is,as suggested by some authors,divided into subspecies,we conclude that some differences in embryonic development could also be expected.In the present study,eggs were fertilized using the dry fertilization method and were incubated in a tank equipped with aeration and constant sea water flow.Salinity and content of dissolved oxygen were constant,and the temperature varied between 19.4 and 22.3°C.Eggs were spherical,measuring 3071.9±75.73μm in diameter.Yolk sacs were homogeneous and did not contain oil globules.The first larvae hatched 329 h and 47 min after fertilization.Absorption of the yolk sac occurred 17 h–48 h after hatching and the total length of newly hatched larvae was 9.78 mm.The peculiarities observed in the embryonic and early larval development are evidence of an exceptional plasticity and adaptive potential,which could be considered as helpful features in extending the natural range of occurrence of this species.展开更多
文摘Establishing intraspecific breeding and hybridization programs and determining genetic variability are two important issues for aquaculture. However, interspecific hybridization to improve growth and feeding efficiency is limited. For this purpose, the embryonic and larval development of reciprocal crosses of Clarias gariepinus (Burchell, 1822) and Clarias jaensis (Boulenger, 1909) were studied under laboratory conditions. The fertilization rate varied from 63.33% to 92%, while the hatching rate ranged from 55.68% to 76% with the highest value in hybrids ♀Cg × ♂Cj. Crosses between ♀Cj × ♂Cj, ♀Cg × ♂Cj and ♀Cj × ♂Cg had embryonic stages similar to those of the pure sib ♀Cg x ♂Cg. All crosses, however, had different timing for the various embryological stages. Hatching occurred at 32 h 15 min and 38 h for ♀Cj × ♂Cj and ♀Cj × ♂Cg, and 23 h and 23 h 30 min, respectively, for ♀Cg × ♂Cg and ♀Cg × ♂Cj. However, both crosses produced viable larvae until the first external feeding. The external morphological features of the larvae were completely formed by the 10th day after hatching. The body forms of the crosses at this time were indistinguishable from the pure sib. This study thus laid the groundwork for further comparative studies on hybrid performance and characterization.
文摘Although information about embryonic and larval development of garpike,Belone belone(Linnaeus,1761),is present in the published literature,the bulk of research concerns garpike from the northeastern Atlantic Ocean and the Baltic Sea.The present work describes the embryonic and larval development of garpike,Belone belone,from the Adriatic Sea,and methods used for incubation of fertilized eggs in aquarium conditions.Because garpike is,as suggested by some authors,divided into subspecies,we conclude that some differences in embryonic development could also be expected.In the present study,eggs were fertilized using the dry fertilization method and were incubated in a tank equipped with aeration and constant sea water flow.Salinity and content of dissolved oxygen were constant,and the temperature varied between 19.4 and 22.3°C.Eggs were spherical,measuring 3071.9±75.73μm in diameter.Yolk sacs were homogeneous and did not contain oil globules.The first larvae hatched 329 h and 47 min after fertilization.Absorption of the yolk sac occurred 17 h–48 h after hatching and the total length of newly hatched larvae was 9.78 mm.The peculiarities observed in the embryonic and early larval development are evidence of an exceptional plasticity and adaptive potential,which could be considered as helpful features in extending the natural range of occurrence of this species.
