台灣產跑蛛科核型之研究

Abstract

摘要 台灣產跑蛛科目前記錄有黑背狡蛛、褐腹狡蛛、溪狡蛛、赤條狡蛛、長觸肢跑蛛、華麗四角蛛、跑蛛及白條跑蛛8種。前人僅止於種類紀錄的調查、形態的描述與零星生態方面的報導，並無更深入的研究。在細胞遺傳學方面，染色體資料的建立將可彌補形態分類的不足，並提供系統演化方面另一有用的證據，本研究以染色體的核型來看跑蛛科演化親緣關係，並推測染色體可能的演化方向。 本研究共獲得台灣產跑蛛科4屬7種的核型資料。染色體形態均為端著絲點染色體，狡蛛屬(除褐腹狡蛛外)、長觸肢跑蛛、跑蛛及白條跑蛛在內的4屬6種，其染色體數目均為2N = 30 (F)/28 (M)；性別決定機制為X1X2O型；NF值為30 (F)/28 (M)。首次發現褐腹狡蛛染色體數目2N = 20 (F)/19 (M)；性別決定機制為XO型；NF值為20 (F)/19 (M)。在C-顯帶染色方面，推測台灣產跑蛛科蜘蛛的C-顯帶應位於端著絲點染色體的中節。在NORs方面，台灣產跑蛛科蜘蛛NORs均只有一對，其中溪狡蛛及黑背狡蛛均位於第5對染色體上；跑蛛位於第14對；白條跑蛛位於第12對上；長觸肢跑蛛位於第3對上；赤條狡蛛位於第2對上；褐腹狡蛛位於第6對上。染色體核型方面，共可分為六種典範核型，包括褐腹狡蛛型、溪狡蛛型、赤條狡蛛型、長觸肢跑蛛型、跑蛛型以及白條跑蛛型，六種典範核型非常相似。在性染色體方面，溪狡蛛、長觸肢跑蛛、跑蛛及白條跑蛛共4種，性染色體均為第1對及第15對；赤條狡蛛為第1及第9對；褐腹狡蛛只有一對性染色體為第5對；而黑背狡蛛因資料不足無法正確判斷。性別決定機制XO型由X1X2O型經性染色體接合演化而來。染色體演化方面，跑蛛型為台灣產跑蛛科中最原始的，而白條跑蛛型、長觸肢跑蛛型及溪狡蛛型三者的親緣關係無法區分。在狡蛛屬內，我推測狡蛛屬中溪狡蛛型為較原始的種類，其次為赤條狡蛛型，褐腹狡蛛為型最進化的種類，染色體數目朝向減少的方向進行。 期望以上資料的建立，能提供一些資訊，對於蜘蛛染色體演化及親緣關係探討等相關研究有所幫助。Abstract The pisaurid spiders of Taiwan consist of eight known species: i.e. Dolomedes horishanus, D. mizhoanus, D. raptor, D. saganus, Hygropoda higenaga, Perenethis venusta, Pisaura sp., and Thalassius phipsoni. There is no advanced research but only few studies related to the spider fauna records, morphological descriptions, and some ecological works have been reported in Taiwan. Chromosome data proved to be useful in animal phylogeny. The present study focuses on the relationships of pisaurid spiders in Taiwan via cytogenetial approaches. Four genera and seven species of pisaurid spiders from Taiwan were successfully karyotyped. All members of the genus Dolomedes (except D. mizhoanus), Hygropoda higenaga, Pisaura sp., and Thalassius phipsoni have the same chromosome numbers with 2N = 30 in females and 28 in males, X1X2O type sex–determining mechanism, and NF vales with 30 in females and 28 in males. Dolomedes mizhoanus has chromosome numbers with 2N = 20 in females and 19 in males, XO type sex–determining mechanism, and NF vales of 20 in female and 19 in male. All are tolecentric chromosome in all karyotyped materials. The C – bands of chromosomes in Taiwanese pisaurid spiders are presumed in centromere of tolecentric chromosomes. There is only one pair of Ag – NORs in each studied pisaurid spiders. The positions of Ag – NORs in karyopypes are located at the distal ends of the 5th pair in Dolomedes horishanus and D. raptor, at the 14th pair in Pisaura sp., at the 12th pair in Thalassius phipsoni, at the 2nd pair in D. saganus, and at the 6th pair in D. mizhoanus.The karyotype of family Pisauridae can be grouped into six forms, i.e. D. mizhoanus form, D. raptor form, D. saganus form, Hygropoda higenaga form, Pisaura form, and Thalassius phipsoni form.The sex chromosomes are the 1st and 15th pairs in the karyotype of Dolomedes raptor, Hygropoda higenaga, Pisaura sp., and Thalassius phipsoni, the 1st and 9th pairs of Dolomedes saganus, and the 5th pairs of Dolomedes mizhoanus. The sex chromosomes of Dolomedes horishanus are remained unknown. The X1X2O type sex-determining mechanism is proposed to be primitive and the XO type is to be derived from the X1X2O type by fusion of the sex–chromosomes. For the evolution of pisaurid chromosomes from Taiwan, we proposed that the model karyotype of Pisaura form should be the most primitive in Pisauridae, and the Hygropoda higenaga form, Thalassius phipsoni form and Dolomedes raptor form were derived. Dolomedes raptor form is the most primitive model karyotype of the genus then is the Dolomeds saganus form, and the Dolomedes mizhoanus form is proposed to be the most derived form. The direction of the evolution of chromosome numbers in the family Pisauridae is from high to low. We hope our data can provide some useful cues in the chromosome evolution and relationships of spiders.