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Gigascience. 2016 Sep 9;5(1):36. doi: 10.1186/s13742-016-0144-3.

The genome of the largest bony fish, ocean sunfish (Mola mola), provides insights into its fast growth rate.

Pan H1,2, Yu H1,2, Ravi V3, Li C1,2, Lee AP3, Lian MM3, Tay BH3, Brenner S3, Wang J4,5, Yang H4,5, Zhang G6,7,8, Venkatesh B9,10.

Author information

1
State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China.
2
China National Genebank, BGI-Shenzhen, Shenzhen, China.
3
Comparative Genomics Laboratory, Institute of Molecular and Cell Biology, A*STAR, Biopolis, Singapore, 138673, Singapore.
4
BGI-Shenzhen, Shenzhen, 518083, China.
5
James D Watson Institute of Genome Sciences, Hangzhou, 310058, China.
6
State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China. zhanggj@genomics.cn.
7
China National Genebank, BGI-Shenzhen, Shenzhen, China. zhanggj@genomics.cn.
8
Centre for Social Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark. zhanggj@genomics.cn.
9
Comparative Genomics Laboratory, Institute of Molecular and Cell Biology, A*STAR, Biopolis, Singapore, 138673, Singapore. mcbbv@imcb.a-star.edu.sg.
10
Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119228, Singapore. mcbbv@imcb.a-star.edu.sg.

Abstract

BACKGROUND:

The ocean sunfish (Mola mola), which can grow up to a length of 2.7 m and weigh 2.3 tons, is the world's largest bony fish. It has an extremely fast growth rate and its endoskeleton is mainly composed of cartilage. Another unique feature of the sunfish is its lack of a caudal fin, which is replaced by a broad and stiff lobe that results in the characteristic truncated appearance of the fish.

RESULTS:

To gain insights into the genomic basis of these phenotypic traits, we sequenced the sunfish genome and performed a comparative analysis with other teleost genomes. Several sunfish genes involved in the growth hormone and insulin-like growth factor 1 (GH/IGF1) axis signalling pathway were found to be under positive selection or accelerated evolution, which might explain its fast growth rate and large body size. A number of genes associated with the extracellular matrix, some of which are involved in the regulation of bone and cartilage development, have also undergone positive selection or accelerated evolution. A comparison of the sunfish genome with that of the pufferfish (fugu), which has a caudal fin, revealed that the sunfish contains more homeobox (Hox) genes although both genomes contain seven Hox clusters. Thus, caudal fin loss in sunfish is not associated with the loss of a specific Hox gene.

CONCLUSIONS:

Our analyses provide insights into the molecular basis of the fast growth rate and large size of the ocean sunfish. The high-quality genome assembly generated in this study should facilitate further studies of this 'natural mutant'.

KEYWORDS:

Body size; Cartilaginous skeleton; Growth rate; Mola mola; Ocean sunfish; Positive selection

PMID:
27609345
PMCID:
PMC5016917
DOI:
10.1186/s13742-016-0144-3
[Indexed for MEDLINE]
Free PMC Article

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