探討台灣鯷科魚類之形態與分子性狀差異並推論其類緣關係

Abstract

全球鯷科(Engraulidae)魚類共有16個屬139種，台灣附近海域計有5屬12種：黃鯽(Setipinna tenuifilis)、芝蕪綾鯷(Thryssa chefuensis)、杜氏綾鯷(T. dussumieri)、漢氏綾鯷(T. hamiltonii)與長頷綾鯷(T. setirostris)、日本鯷魚(Engraulis japonicus)、刺公鯷(Encrasicholina punctifer)、異葉公鯷(E. heteroloba)、孔氏小公魚(Stolephorus coommersonii)、印度小公魚(S. indicus)、島嶼小公魚(S. insularis)與魏氏小公魚(S. waitei)。鯷魚之仔稚魚，為台灣沿岸漁業的重要漁獲，主要出現在西北海域(淡水、桃園、新竹)、東北海域(宜蘭、梗枋、大溪)以及西南海域(枋寮、林園)。 實務上，鯷科之物種鑑定有相當程度之困難，因而在漁業資源管理上亦成棘手之態。既存之檢索，有許多特徵具有相當大的重疊，目前尚無利用單一特徵可供分辨兩個物種之簡便、確實方法，均需要結合多個內部構造之特徵來做參考。此外，各發育時期亦會對些許外部型態特徵造成影響，有些成體特徵，在幼體卻闕如。因此，本研究擬利用形態學之特徵點法，將外部特徵數值化，以統計分析抽取變異(variance)中之對比，做為形貌(shape)因數，俾進一步取其徵值製作檢索表。在電子影像存取便捷的今日，本法將有其相當之延伸性。 研究結果顯示，利用腹鰭起點、臀鰭起點、臀鰭終點與上顎骨長度之幾何關係可區分所實驗的八個種類，其確率皆達95％以上；因此，亦據這些數值化的特徵，整理成檢索表。對應的分子資料之群內均質性，亦肯定事前物種鑑定無誤。最複雜的三物種：日本鯷、刺公鯷、異葉公鯷，經節錄401bp之粒線體DNA胞色素b基因部分序列顯示：鹼基組成在物種間具有顯著差異；種內的變異以日本鯷為最大，而刺公鯷與異葉公鯷具有可比較的大小，分析其類緣關係，得到不同屬的刺公鯷與日本鯷關係比較相近。由於在群內關係上，日本鯷種內的變異大，異於其他兩種，以及刺公鯷與異葉公鯷在多型性方面仍比較相近，因此推論刺公鯷與異葉公鯷來自同一個祖先，在種化歷史上較日本鯷來的年輕。

Engraulidae is composed of 16 genera and 139 species. There are 5 genera with 12 species reported from the coastal waters of Taiwan; Setipinna tenuifilis, Thryssa chefuensis, T dussumieri, T hamiltonii, T setirostris, Engraulis japonica, Encrasicholina punctifer, E. heteroloba, Stolephorus coommersonii, S. indicus, S. insularis, and S. waitei. In the coast of Taiwan, engraulid larvae are common recruits, which support traditional larval fisheries practiced at NW, NE and SW respectively. Identification of engraulid species is not an easy thing, especially as early as larval stages. This situation not only applies to studies on their natural history, but also hinders the prospects for reasonable fishery management. In this study, supported by within group genetic homogeneity, I arrange to analyze engraulid morphometrics, and aim to construct a quantitative key to species in a shape plane. In total, 406 effective samples were used this study, i.e., Engraulis japonicus 37, Encrasicholina heteroloba 96, E. punctifer 60, Thryssa chefuensis 8, T. dussumieri 58, Stolephorus insularis 65, and Setipinna tenuifilis 50. An addition 26 sardine of Dussumieria elopsoides was also incorporated into analysis for out. group reference. In morphometrics, the first three components explain 85.92% of the total variance, and using qualitative comparison of triangles indicate that landmarks at P4 (last insertion of dorsal fin rays crosses the body), P7 (last insertion of anal fin rays crosses the body), P8 (first insertion of anal fin rays crosses the body), P9 (first insertion of pelvic fin rays crosses the body), and P13 (most posterior point of maxillary) are valid for species identification. A section of 401 bases were truncated from cytochrome b gene for comparison on the most complicate species complex. Engraulis japonicus, Encrasicholina heteroloba, and E. punctifer. Site by site comparison indicated 118 (29.43%) variable positions, among which 113 (28.18%) can be informative, of which 11(9.73%) located at codon 1, and 102 sites (90.3%) at codon 3. The fractions of A:T:C:G and autapomorphic sites could be useful factors in specific identification. It is apparent that E. japonicus population had higher, distinctive diversity than the rest two species. However, comparable values are found with E. heteroloba and E. punctifer. In phylogenetic analysis, an aberrant relationship is obtained with lowest inter. specific distance found between E. japonicus and E. punctifer. My results improve the extant identification procedure of engraulid species and open up a window for further review of their phylogeny.