Two experiments were carried out to estimate the gross efficiency and the conversion efficiency of phytoplankton in the growth of silver carp, Hypophthalmichthys molitrix. One involved the determination of the growth rates of silver carp at each respective bloom of different algal species in Lake Kasumigaura, and the other, the estimation of food intake by silver carp. The results showed the gross efficiency figures of 15% for Anabaena, 11% for diatoms and 1.5% for Microcystis. Considering the digestive efficiency, the conversion efficiency figures of 19% were obtained for diatoms and 4.5% for Microcystis.
ABSTRACT. To clarify the phylogenic relationship of channel catfish with other fishes, the cytochrome b (Cyt b) gene of the catfish was cloned and sequenced. Channel catfish (Ictalurus punctatus) belonging to the family Ictaluridae in the order Siluriformes showed a 78.4-87.4 % similarity to all but one fish of the family Cyprinidae and river loach Crossostoma lacustre of the family Balitoridae in the order Cypriniformes in which genes had already been sequenced, and a 97.2 % similarity to the goldfish (Carassius auratus) belonging to the family Cyprinidae. Within the family Cyprinidae, a 78.8-89.2% similarity to one another was recorded. In addition, the similarity rate between the family Cyprinidae and the family Balitoridae reached a value of 77.8-79.9% in the order Cypriniformes. Furthermore, in an unrooted phylogenetic tree consisting of four branches among eight fishes, channel catfish and goldfish appeared in the same branch. These results suggested that the Cyt b gene of the channel catfish in the order Siluriformes was closely related to that of a goldfish in the order Cypriniformes. The results were not agreement with the morphological classification. Genetic reclassification of the fishes may be necessary to identify the ancestor. This is the first report on the cloning and complete sequencing the Cyt b gene of the channel catfish which may contribute to the genetic reclassification of catfishes belonging to the order Siluriformes. Catfishes with various characteristics are known to consist of about 2,200 species and are widely distributed throughout the world. However, the catfishes have been classified only morphologically. On the other hand, although analyses of mitochondrial genes such as cytochrome b (Cyt b) and 16S ribosomal RNA genes of other fishes have been performed, there has been no report on the analysis of the complete sequences of the genes of the catfishes, unlike those of the genes in other fishes (the family Cyprinidae). Therefore, the evolutionary relationship between the catfishes and others fishes has not been determined. To address this problem, nucleotide sequence analyses of mitochondrial genes have been attempted. As a result, the complete nucleotide sequence of the Cyt b gene of the channel catfish (I. punctatus) were analyzed and the base arrangement between the catfish and other fishes was compared.Total DNAs were isolated from the channel catfish (I. punctatus) [6] and Taq DNA polymerase (Takara-Shuzo Co., Kyoto, Japan). The resultant fragments were introduced into a pUC19 vector and sequenced on both sides by using a DSQ-1000L DNA sequencer (Shimadzu
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