| At present,there are more than 92 species of cetaceans around the world,including 14 species in 4 families of Suborder Mysticeti and 78 species in 10 families of Suborder Odontoceti.At least 37 species accounted for 40%have been found in Chinese waters.10 species in 3 families of baleen whales and 27 species in 6 families of tooth whales have been recorded from the Bohai Sea,Yellow Sea,the East China Sea to the South China Sea.All cetaceans are protected under the Chinese laws.Chinese white dolphin is listed as the first-class national protected animals,the others are included in the second-class national protected animals.Cetaceans live in fresh water or seawater,and there is little chance to encounter and study them in the wild.Our knowledge of cetaceans is extremely limited,while the most of researches were based on stranding and bycatches.Omura's whale is recently recognized as a new baleen whale species and considered as one of the most mysterious species among them.As one of the least known baleen whales,it is red-listed as "Data Deficient" by IUCN.Omura's whale is separated from all known baleen whale species based on comparison of external morphology,osteology and mitochondrial DNA data.On 27 November 2011,a baleen whale was stranded in the northwestern coast of the Taiwan Strait,China.Its body length was about 7.15 m.Most of epidermis had already been removed because of decomposition;it was difficult to conduct exact species identification and preliminarily suspected as a fin whale calf basing on morphological characteristics.Therefore,both mitochondrial DNA gene fragments,cytb and coxl were amplified for molecular identification.Sequence similarity searches in different databases,diagnostic sites in genus Balaenoptera and phylogenetic mtDNA gene tree analyses indicated that the baleen whale is an Omura's whale.In addition,morphological measurements and descriptions of this specimen were performed.A pair of exposed male nipples at both sides of the posterior end of the genital slit were firstly recorded in Omura's whale.Meanwhile,other 14 reliable stranding records of this species were reviewed along the Chinese coastal waters.Omura's whale stranding records mainly distributed along the southeast coast of China,particularly aggregated on the Taiwan Strait.It is favorable that Omura's whale is more like lyto migrate through the Taiwan Strait and its adjacent waters between the Sea of Japan and Solomon Islands.And the South of Chinese coastal water is a potentially important habitat for Omura's whale.The numbers of haplotypes and nucleotide substitutions were both small in Omura's whale,and it is possible that Omura's whale population size is tiny with low genetic diversity and is of conservation concern.Gray whales,the sole species of family Eschrichtiidae,are currently recognized as two geographically distinct populations in the North Pacific Ocean:The Eastern North Pacific(ENP)population and the Western North Pacific(WNP)population.The WNP is red-listed as critically endangered by IUCN because of its small population size.On 5 November 2011,a female gray whale was found entangled with set gillnet in the Pingtan Island,Fujian Province of China.This mature individual is 13.09m in body length and 21t in weight.Notably,this is the biggest individual and is the first gray whale record of Chinese coastal waters in the 21th century.The photographs were then sent to conduct individual photo-identification comparison with the identified gray whale photo-identification catalogs from the WNP and ENP.The result showed that there was no match in both the WNP and ENP photo-catalogs.Subsequently,genetic studies of this gray whale were conducted and three fragments of mitochondrial DNA(D-loop,cytb&coxl)were amplificated successfully.As a new haplotype in gray whale,the coxl gene sequence indeed was differ from the ENP.The 522 bp DNA fragments of 5'region of D-loop was completely identical to the haplotype R which is exclusive to the ENP population and extremely low probability occurring in the WNP population.On this account,the Pingtan gray whale was speculated as a vagrant entering the Taiwan Strait from the ENP.Further discussions about which population the Pingtan gray whale should belong to were given.Decomposition of carcasses and easily confused external features between the similar cetaceans both bring us a lot of difficulties to correct identification of the stranded/bycaught cetaceans.based only on morphological characters,there are inevitably some mistakes for cetaceans' identification.We collected some stranded/bycaught cetaceans and gave them the provisional names according to the external features.Molecular identification was conducted by cytb,coxl and D-loop for reconfirmation.Analysis of sequence similarity alignment and phylogenetic gene trees,26 samples were successfully identified and we obtained their accurate species names.There are three baleen whales and ten toothed whales,and they are Omura's whale,common minke whale,gray whale,pygmy sperm whale,finless porpoise,pygmy killer whale,rough-toothed dolphin,Indo-Pacific bottlenose dolphin,common bottlenose dolphin,pantropical spotted dolphin,short-finned pilot whale,Chinese white dolphin and Blainville's beaked whale.In total,two baleen whales and eight toothed whales' samples were renamed.Compared to morphological identification for the stranded/bycaught cetaceans,it was more effective,accurate and convenient to conduct molecular identification using appropriate molecular genetic markers.In our 37 mtDNA sequences,28 new haplotypes were firstly found and absent in the NCBI GenBank nucleotide collection database,including nine of cytb,two of coxl and 17 of D-loop sequences.Our studies were thought as the fundamental and indispensable supplement for cetaceans in Chinese coastal waters and as the necessary basis of other scientific researches,such as species survey and adaptive evolution of functional genes.These studies also help a good effect for us to develop the reasonable and effective proposals for cetaceans' protection and management.Cetacean are the most exceptional and mysterious aquatic mammals that returned from land back to water about 53-56 Ma.To adapt to the aquatic environment,the external morphology and physiology had undergone many adaptive transformations.Hence,cetacean has become an ideal model for the study of adaptive evolution.The variety of body size in cetacean is the most obvious morphological characters.To explore its molecular mechanism,we studied the growth hormone(GH)and its receptor genes(GHR)to see if there was a correlation.As the most mammals,the gh gene in 13 species of cetacean we obtained was a single copy gene,which was consist of 5 exons and 4 introns and encoded 216 amino acids.Nine amino acid substitutions were detected,however,there was apparently no correlation between the substitutions with the binding interaction of GH and GHR.The ghr gene encoding 639-640 amino acids in 11 species of cetacean was obtained.Most amino acid substitutions were presented in the intracellular domain and there were no obvious correlations with the variety of body size in cetaceans.Branch model,site model and branch-site model basing on the method of maximum likelihood,have been proceeded to test the molecular evolution of the ghr gene in cetacean.No positive selection and none positive sites were detected in cetacean lineage.As other mammals,the evolution rate of ghr gene in cetacean was very low and subjected to pure selection.Growth hormone and its receptor evolution both were very conserved in cetacean and had nothing to do with the variety of body size. |
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