We report here the ~670 Mb genome assembly of the Asian seabass (Lates calcarifer), a tropical marine teleost. We used long-read sequencing augmented by transcriptomics, optical and genetic mapping along with shared synteny from closely related fish species to derive a chromosome-level assembly with a contig N50 size over 1 Mb and scaffold N50 size over 25 Mb that span ~90% of the genome. The population structure of L. calcarifer species complex was analyzed by re-sequencing 61 individuals representing various regions across the species’ native range. SNP analyses identified high levels of genetic diversity and confirmed earlier indications of a population stratification comprising three clades with signs of admixture apparent in the South-East Asian population. The quality of the Asian seabass genome assembly far exceeds that of any other fish species, and will serve as a new standard for fish genomics. We describe the genome assembly of Asian seabass (Lates calcarifer), a marine teleost with aquaculture relevance. Though >500 eukaryotic genome sequences are available in public repositories, the majority are highly fragmented with incomplete assemblies, which explains why considerable effort and resources are often spent to improve their quality after publication. In our study, we employed long read sequencing combined with genetic and optical mapping, and syntenic information to produce a chromosomal level assembly. The largely continuous genome assembly will be useful for comparative genomics and offers an opportunity to look into regions less explored such as tandem repeats (the core component of centromeres and telomeres). In addition, population structure of the species was analysed based on low-coverage genome sequence information from 61 individuals representing diverse geographic locations stretching from North-Western India across South-East Asia and Australia to Papua New Guinea.

Asian seabass (Lates calcarifer) is a food fish of increasing aquaculture importance. In order to improve our understanding on the digestive system and feeding of this species, morphological and histological features of the gut were studied. Morphologically, the Asian seabass gut is defined by a short and muscular esophagus, well-developed stomach and comparatively short intestine. Mucous secreting goblet cells reactive to PAS (Periodic Acid Schiff) and AB (Alcian Blue) stain were present throughout the esophagus. The stomach was sac-like and could be distinguished into the cardiac, fundic and pyloric regions. Gastric glands and mucus cells were predominately present in the cardiac and fundic regions. Five finger-like pyloric caeca were present between the stomach and intestine. The intestine was a short, tubular structure with no morphological differences between the various regions. Histologically, the intestinal regions were similar, the main difference being in the number of goblet cells that increased from anterior to posterior intestine, with 114 ± 9, 153 ± 7 and 317 ± 21 goblet cells in the anterior, mid and posterior regions, respectively. The intestinal epithelium stained positively for PAS, but the staining was stronger for acidic glycoproteins. The rectum was similar to intestine, except for increased goblet cell numbers (anterior rectum: 529 ± 26; posterior rectum: 745 ± 29). Gut morpho-histology did not respond to salinity changes, however, there was a significant reduction of mucosal height, goblet cell numbers and muscularis thickness upon food deprivation.

Asian seabass or barramundi (Lates calcarifer) is an important food fish with commercial value and a wide geographic distribution. Though some reports based on molecular and/or morphological data exist, a comprehensive effort to establish species identity across its range is lacking. In order to address this issue and especially to ascertain whether the wide-spread distribution has resulted in bifurcation of the species, we collected Asian seabass samples from various locations representing the Western and Eastern Coastline of India, Andaman and Nicobar Islands, Bangladesh and Australia. Samples from Malaysia, Indonesia, Thailand and Singapore were collected as part of a previous study. DNA sequence variations, including cytochrome c oxidase subunit 1 (COI), 16S rDNA and the highly variable D-loop (or control region), were examined to establish species delineation. Data from all the sequences analyzed concordantly point to the existence of at least two distinct species - one representing the Indian subcontinent plus Myanmar, and a second, representing Southeast Asia (Singapore, Malaysia, Thailand and Indonesia) plus Northern Australia. These data are useful for conservation ecology, aquaculture management, for establishing the extent of genetic diversity in the Asian seabass and implementing selective breeding programs for members of this species complex.

The Asian seabass (or barramundi; Lates calcarifer) is a marine teleost and a popular food fish in Southeast Asia and Australia. To date, comprehensive genome and transcriptome sequence information has not been available for this species in public repositories. Here, we report a comprehensive de novo transcriptome assembly of the Asian seabass. These data will be useful for the development of molecular tools for use in aquaculture of Asian seabass as well as a resource for genome annotation. The transcriptome was obtained from sequences generated from organs of multiple individuals using three different next-generation sequencing platforms (454-FLX Titanium, SOLiD 3+, and paired-end Illumina HiSeq 2000). The assembled transcriptome contains >80% of the expected protein-coding loci, with 58% of these represented by a predicted full-length cDNA sequence when compared to the available Nile tilapia RefSeq dataset. Detailed descriptions of the various steps involved in sequencing and assembling a transcriptome are provided to serve as a helpful guide for transcriptome projects involving de novo assembly of short sequence reads for non-model teleosts or any species of interest.