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Expressed sequence tag (EST) analysis is an efficient tool for gene discovery and for profiling gene expression. A cDNA library developed from messenger RNA of the Japanese flounder, Paralichthys olivaceus spleen was constructed by directional cloning, in order to isolate functional genes involved in immunity in fish. A total of 1010 ESTs from the library were sequenced and compared with sequences in the GenBank database. Of the 1010 ESTs, 618 ESTs (61%) were identified as being homologous with known genes from many organisms by BLAST searches, whereas 392 (39%) appeared to be unknown and are likely to represent newly described genes. Of the identified genes, 105 (17%) encoded proteins associated with cell/organism defence and homeostasis. Of these 105 genes, 21 were identified for the first time in Japanese flounder. These included macrophage inflammatory protein (MIP)-3 α, granulin-A, novel immune-type receptor (NITR), interferon regulatory factor (IRF)-10, presenilin-like protein-2, and antizyme inhibitor. A comparison of ESTs derived from spleen, kidney, liver and leukocytes suggested that expression of immune-related genes in different tissues, organs, or cells are different.KEY WORDS: cDNA sequence, expressed sequence tag, Japanese flounder, spleen.

A list of genes expressed in the liver of Japanese flounder was compiled using an expressed sequence tag (EST) strategy; 940 EST derived from liver cDNA clones were determined. Bioinformatic analysis revealed that 537 (57%) of the EST could be ascribed to the transcriptional products of identified genes including 397 previously described in fish. The identified genes were classified with respect to a cellular role, which showed that 314 (58%) of the identified genes encoded proteins associated with primary liver functions such as transport, acute phase response, and blood clotting. Furthermore, comparative analysis revealed that 26 unique genes had homologous to known genes highly expressed in mammalian liver systems. cDNA clones corresponding to antimicrobial peptide origin in the mammalian liver, the hepcidin-like peptide, had conserved cysteine residues similar to the previously identified hepcidin-like peptide type II from winter flounder and were also found in Japanese flounder.

The snakehead fish (Channidae) is widely distributed in inland water of Indonesia. This fish is native species in Suma-tera, Java and Kalimantan, but non-native species in Sulawesi and Papua. Study on molecular identification and phylo-geny of this fish using cytochrome c oxidase subunit I (COI) gene has only been conducted on snakehead fish origin from Tasikmalaya, Ambarawa, Bali, Aceh, Pontianak, and Banjarmasin waters, but none is available in South Sulawesi waters. The objectives of this research are to identify species of snakehead fish from Towuti Lake Sorowako and the first generation (F1) of domesticated snakehead fish from Bantaeng waters of South Sulawesi using COI gene for DNA barcoding, and to analyze the phylogenetic resolution of the fish. Partial sequences of the COI gene of the snakehead fish were aligned with sequences of snakehead fish deposited in GenBank. The phylogenetic tree was constructed using MEGA 7.0.20 program. The result indicated that COI gene nucleotides of snakehead fish from Towuti Lake Sorowako showed 99% homology with Channa striata acc no. KU692418 and KU692421, and showed 98% homology with those of acc no. KU852443. Therefore it can be conclude that Channa striata exist in Towuti Lake Sorowako. Nucleotide sequences of the first generation (F1) of domesticated snakehead fish from Bantaeng waters showed 65% homology with Channa pleurophthalma (acc no. KJ937390) origins from Banjarmasin waters and Channa gachua (acc no. KX389277). Based on this result, it assumed that snakehead fish from Towuti Lake Sorowako are distantly in gene to those from Bantaeng waters, and further analyses are required to identify the population of snakehead fish from Bantaeng waters. Abstrak Populasi ikan gabus (famili Channidae) tersebar luas di wilayah perairan tawar Indonesia. Ikan gabus merupakan ikan asli di Sumatera, Jawa, dan Kalimantan) tetapi merupakan ikan introduksi di Sulawesi dan Papua. Identifikasi berdasar-kan gen cytochrome c oxidase subunit I (COI) telah dilakukan terhadap ikan gabus dari perairan di Tasikmalaya, Amba-rawa, Bali, Aceh, Pontianak dan Banjarmasin, tetapi ikan gabus dari perairan Sulawesi Selatan belum dilakukan. Tuju-an penelitian adalah untuk mengidentifikasi species ikan gabus dari Danau Towuti Sorowako dan ikan gabus generasi I (F1) hasil domestikasi dari induk yang berasal dari perairan tawar Kabupaten Bantaeng Sulawesi Selatan menggunakan gen COI untuk DNA barcoding, dan untuk menganalisis filogeni ikan gabus tersebut. Sekuen gen COI ikan gabus terse-but disejajarkan dengan sekuen nukleotida ikan gabus yang terdeposit di GenBank. Pohon filogenetik dikonstruksi de-ngan menggunakan program MEGA 7.0.20. Hasil penelitian menunjukkan bahwa nukleotida gen COI sampel ikan gabus dari Danau Towuti Sorowako memiliki kemiripan 99% dengan Channa striata nomor aksesi KU692418 dan KU692421 dan 98% dengan Channa striata nomor aksesi KU852443 sehingga dapat disimpulkan bahwa di Danau To-wuti terdapat ikan gabus jenis Channa striata. Tingkat kemiripan sekuen nukleotida ikan gabus F1dari perairan Kabu-paten Bantaeng adalah 65% dengan ikan gabus Channa pleurophthalma (KJ937390) asal perairan Banjarmasin dan ikan gabus Channa gachua (KX389277). Berdasarkan hasil tersebut maka diduga bahwa ikan gabus dari Danau Towu-ti Sorowako berkerabat jauh dengan ikan gabus dari perairan Bantaeng, dan diperlukan analisis yang lebih lanjut untuk menentukan jenis populasi ikan gabus F1 asal perairan tawar Kabupaten Bantaeng tersebut.