台灣新紀錄種蚯蚓乳突重胃蚓Dichogaster affinis（Michaelsen, 1890）

A New Record of the Octochaetid Earthworm Dichogaster affinis (Michaelsen, 1890) from the Centro-western Taiwan

This paper describes the octochaetid earthworm Dichogaster affinis (Michaelsen, 1890) as a new record from the centro-western Taiwan. It is a small earthworm with two gizzards, belonging to the family Octochaetidae. D. affinis is quadriprostatic and has a pair of female pores in XIV and genital markings in 7/8-9/10. It is easily distinguishable from other two congeneric species in Taiwan, Dichogaster saliens (Beddard, 1892) that is biprostatic and Dichogaster bolaui (Michaelsen, 1891) that is quadriprostatic but has a single female pore and no genital marking. Occurrence of D. affinis in Taiwan reported herein constitutes the island as the northernmost range of this cosmopolitan species in East Asia. 本文描述一台灣新紀錄種蚯蚓乳突重胃蚓Dichogaster affinis（Michaelsen, 1890）。其為小型蚯蚓，屬於八毛蚓科（Octochaetidae）重胃蚓屬（Dichogaster），具有兩對前列腺及一對雌性生殖孔，且在7／8至9／10體節間有生殖乳突。在台灣其餘兩種同屬物種為Dichogaster saliens（Beddard, 1892）及Dichogaster bolaui（Michaelsen, 1891），前者僅具一對前列腺，後者具有兩對前列腺但僅有一個雌性生殖孔且不具生殖乳突。D. affinis的發現使得台灣成為此種廣布種蚯蚓在東亞分布的北界。