線蟲及魚蚤與盲鰻之寄生關係

Abstract

盲鳗是脊椎動物中最原始的一群，只有軟骨形成的頭骨，沒有脊椎骨。在海洋食物鏈中扮演重要的腐食生物角色。海獸胃線蟲為海水魚中常見的寄生蟲，藉由寄主的掠食行為進行寄主轉移，並且以橈足類、頭足類、硬骨魚類為保蟲寄主。本研究將探討盲鰻寄生蟲相，以及盲鰻食用其他海洋動物的屍體時，是否能經由腐食方式感染海獸胃線蟲。 盲鰻樣本於2013年11月至2014年6月宜蘭大溪漁港向漁民購買，共包含四種盲鰻：蒲氏黏盲鰻 (Eptatretus burgeri)、楊氏黏盲鰻 (E. yangi)、沈氏黏盲鰻 (E. sheni)、臺灣黏盲鰻 (E. taiwanae)，經調查後發現七種海獸胃線蟲寄生，主要寄生於腸道，極少部分進入體腔及肌肉，經過PCR-RFLP及rDNA ITS序列定序後確定為Anisakis pegreffii、A. simplex s.s.、A. pegreffii與A. simplex s.s.的重組基因型、A. typica、Anisakis sp.、A. brevispiculata、Hysterothylacium amoyense。盲鰻為7種海獸胃線蟲之寄主新紀錄，此外Anisakis sp.及H. amoyense為地理新紀錄。另外，也發現一種橈足類，盲鰻刺魚蚤 (Acanthochondria eptatreti)，寄生於盲鰻的咽部，已於2014發表為新種。 研究首度發現海獸胃線蟲能以腐食方式傳播並寄生於盲鰻，修改了海獸胃線蟲之生活史。統計結果顯示，蒲氏黏盲鰻之線蟲盛行率及盲鰻刺魚蚤盛行率皆顯著高於其他三種盲鰻。蒲氏黏盲鰻與沈氏黏盲鰻之線蟲感染強度也與體長呈現正相關，盲鰻刺魚蚤感染強度只與蒲氏黏盲鰻有正相關。也觀察到寄生蟲於寄主的累積效應。

Hagfishes are the most primitive vertebrates known. They have a cartilaginous skull but no vertebral column. Hagfish is marine benthic scavenger which feed on dead organic matter, including teleosts, cetaceans, marine inverts, etc. Anisakis is transferred by host predation, and their paratenic hosts include crustaceans, cephalopods, and teleost fish. The aim of this study is to investigate the parasitical fauna of hagfish and confirm that hagfish can be infected by Anisakis via host scavenging. Hagfishes were caught from Daxi fishery harbor in northeastern Taiwanese waters from November 2013 to June 2014. A total of 265 samples were examined and four species of the genus Eptatretus, Eptatretus burgeri, E. yangi, E. sheni and E. taiwanae. These four species of hagfishes were infected by Anisakidae nematodes, which parasitized mainly in the gastrointestinal tract wall. Also, anisakid nematodes species were identified by PCR-RFLP. Seven species of nematodes were recorded: Anisakis pegreffii, A. simplex s.s., recombinant genotype of A. pegreffii and A. simplex s.s., A.typica, Anisakis sp., A. brevispiculata and Hysterothylacium amoyense. All Anisakid nematodes are new host records, and two of them (Anisakis sp. and H. amoyense) are new locality records. In addition, a new species of chondracanthid copepod, Acanthochondria eptatreti, was identified and isolated from the pharynx of hagfish, and has been published in 2014. The results proved that anisakid nematodes can transfer by hagfish scavenging and modified Anisakis life cycle. Statistical analysis showed that the prevalences of two kinds of parasites (nematode and copepod) are significant higher in E. burgeri. The intensity of nematodes positively correlated with host size of E. burgeri and E. sheni. The intensity of copepod only has positive correlation with E. burgeri. The accumulation of parasites in larger hosts can be observed in this study.