利用生命條碼方法從事台灣海域魚類早期生活史之分類研究

Abstract

台灣位於全球海洋生物多樣性最高的珊瑚大三角之北緣，擁有全球十分之ㄧ，種數約3000種的魚類。魚類資源豐富，多樣性高，亟需人們的保護。而了解成魚之生殖量、生殖期及產卵場，才能有效地擬定保護策略，此乃因魚卵、仔魚的入添 (recriutment) 與魚類資源的保育管理及永續利用息息相關。但前提是必須先對魚卵和仔魚做出正確的種別鑑定，才能確知魚類早期生活史之重要資訊。本研究係利用孵化方法觀察海水魚魚卵之連續發育形態，並結合生命條碼可對魚卵和早期仔魚之分子鑑種，來評估利用孵化法鑑定魚卵之效益及可行性，同時亦收集魚卵在台灣週邊海域之種類組成及時空分佈資訊。 本研究取樣的104顆活魚卵孵化率達七成，魚卵如由光學形態可區分出38個類型 (types)，其中5個到目，14個到科，5個到種及14個為未知類型，共24個分類群 (taxa)；但藉由孵化後之仔魚形態，則鑑別率可提升為41個類型，其中包含27個分類群；如再進一步利用COI生命條碼鑑定，則可分出58個類型，其中2個鑑定到目，13個到科，14個到屬，29個到種，共58個分類群，可確認出種別的29種中有3科5屬16種為文獻上的首次形態描述。當然在相似魚卵或仔魚形態下，也可能包含多個物種如鯙科、擬金眼鯛科及帶魚科。而帶魚科可鑑定出白帶魚 (Trichiurus lepturus) 和 日本帶魚 (Trichiurus japonicus)兩種魚卵的存在，其中日本帶魚於台灣南北海域皆有分佈。而鯙科魚卵於南部墾丁分布時間主要為9月份，擬金眼鯛科和帶魚科魚卵則幾乎是一年四季。另外，魚卵樣本定序結果與BOLD Non-reference資料庫、reference資料庫及自行建立之條碼資料庫比對，以BOLD Non-reference資料庫物種之鑑別率最高，且三者鑑定結果亦有出入，此顯示資料庫中成魚樣本條碼資料之完整性與標本鑑定之正確與否，決定了序列比對結果之正確性。此外利用DNA序列條碼方法來鑑定物種，亦能協助製作魚卵或早期仔魚之形態檢索表。然而也由於成魚之生命條碼資料庫尚未齊全，故目前仍有1/2之魚卵或早期仔魚未能鑑到種之層級。但當條碼資料庫、魚卵及仔魚形態資料收集及建立完整後，未來應可更容易及正確地掌握台灣週邊海域魚類早期生活史之資訊。

Taiwan is located at the northern edge of the Coral Triangle where marine biodiversity is the richest in the world. There are about 3000 species of fish recorded in Taiwan, which is one tenth of the world’s total species. The supply of fishery resources is related to the recruitment of fish eggs and larvae. Thus the studies of fish early life history and egg identification are important for the resource conservation and management. In this study, a series of developmental morphology of marine fish eggs were observed using the hatching method and verified with molecular identification utilizing DNA barcoding to assess the feasibility and efficiency of the hatching method. The data collected also contributed to a better understanding of species composition, temporal and spatial distribution of fish eggs in the waters off Taiwan. From total of 104 hatched fish eggs, the successful rate of the hatching method is 70 %. These 104 fresh fish eggs were classified into 38 types, including 5 to orders, 14 to families, 5 to species, and 14 unknown types, a total of 24 taxa by their morphological characteristics. Eggs were identified into 41 types, including 27 taxa after hatched to preflexion larvae. However, when applying DNA barcoding, fish eggs or larvae were classified into 58 types, including 2 to orders, 13 to families, 14 to genera, and 29 to species, total of 58 taxa. Among them, 16 species are the first descriptions from the literatures. Certainly, many species share the same egg morphology, such as moray eels, sweepers, and cutlassfishes. For cutlassfishes , DNA barcoding can identify both Trichiurus lepturus and Trichiurus japonicus. The later species occurred in both south and north Taiwan. Regaring reproduction information, moray eels were found spawning in September, but sweepers and cutlassfishes spawn all seasons in the water off southern Taiwan. Comparing the results of specimens identification between the BOLD non-reference, BOLD reference, and fish BOLD of Taiwan demonstrates that the correct species identification of adult fishes is important. Combination of morphological observation and DNA barcoding can identify species more efficiently and assist the preparation of identification keys for fish eggs and larval fishes. Due to the incompletion of the sequence database, half of our specimens could not be assigned to the species level. We could better understand the early life history of fish in Taiwan in the future when the COI database of adult fishes and more information on their morphological characteristics of fish eggs and larvae is more complete.