| In order to understand the developmental relationship between the cycloid scale and ctenoid scale in teleosts,the distribution of the two types of scales in flounder(Paralichthys olivaceus),large yellow croaker(Larimichthys crocea)and small yellow croaker(Pseudosciaena polyactis)were investigated in this research.By comparing with the different morphological structures in different scales stained with alizarin red,we found not only cycloid scale and ctenoid scale with typical structures but also some scales with transitional morphological features between typical cycloid scale and ctenoid scale also existed in same individual in flounder,large yellow croaker and small yellow croaker,indicating the typical ctenoid scale might be developed from the cycloid scale.The different types of scales in similar body sites were found in the flounder at100 days after hatching and adult founder,further indicating there should exist with the developmental relationship between the cycloid scale and ctenoid scale.We further investigated the numbers of cycloid scales and ctenoid scales in different body areas in both L.crocea and P.polyactis,found there is no big difference of the numbers of cycloid scales or ctenoid scales between left and right body sides.We also did not found the difference of the numbers existed in dorsal area,lateral line area and abdomen area.However,the big difference of the numbers was found in the different body areas along anterior to posterior axis in both L.crocea and P.polyactis.The number of cycloid scales decreased gradually from the head to tail,on the contrary,the number of ctenoid scales increased gradually from anterior to posterior.More ctenoid scales are distributed in the rear of body in the two species of croakers,indicating the croaker might use ctenoid scales to generator vortex to improve swimming efficiency.Whether the oscillation of rear part of body can induce the cycloid scale development into the ctenoid scale in some teleosts,we will investigate the possibility in the future.At about 60 days old,original cycloid scales occurred on both sides of larval bodies.The cycloid scales developed into ctenoid scales on the normal ocular side while remained original status on the normal blind side.Contrast to malpigmented individuals,it was observed that the albino ocular side was still covered by cycloid scales,but the cycloid scales developed into ctenoid scales on the ambicolored blind side.Furthermore,observations of the scales on different postions of recovering albino fish showed the development of scales from immature cycloid scales to mature ctenoid scales following the recovery of pigmentation.We investigated the scales of 100 days albino flounder,and found that albino part of the fish was covered by cycloid scales,it is suggested that a close relationship existed between the occurrence of pigmentation and development of scales in Japanese flounder.After flounder become a bottom-dweller,its body color appears asymmetric.There are so many pigmented individuals in mariculture organisms: kinds of albinism in ocular side,and kinds of hypermelanism in blind side.The abnormal body color may influence the survival rate of larvae and the price of adult individuals.To discovery this mechanism,learning the technology Illumina/Solexa transcriptome sequencing,this study collected the skin of normal and hypermelanism adult Pa.olivaceus and using de novo transcriptome sequencing,and found genes about hypermelanism of flounder.There are all detected 160855 SNPs(single nucleotide polymorphism),selected 59 genes which related with body color regulation mechanism,and 12 genes SNPs located in exon region.Besides,using the AS-PCR method,we found that there is a high frequency of mutation in C-type lectin domain family 10 member A-like isoform X1,succinate-semialdehyde dehydrogenase,mitochondrial-like,succinate-semialdehyde dehydrogenase,mitochondrial-like,rhodopsin kinase-like,retinoblastoma-like protein 2,cyclic AMP-dependent transcription factor ATF-4-like and cyclic AMP-responsive element-binding protein 3-like protein 2-like isoform X4 genes,we guess it may be related with molecular mechanism of skin albinism in flatfishes. |
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