真湖蚌蟲趨光性及攝食形態的發育變異

Ontogenic changes in phototaxis and feeding morphology of the clam shrimp Eulimnadia braueriana Ishikawa, 1895

劉哲聿(Jer-Yuh Liu)

指導教授 ： 周蓮香

國立臺灣大學/生命科學院/生態學與演化生物學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01104

摘要

趨光性會影響生物的分布而型態能顯示其功能，本研究以不同照度的人造光源測試真湖蚌蟲 (Eulimnadia braueriana Ishikawa, 1895) 無節幼體、幼體及成體階段的趨光性，並以光學及掃描式電子顯微鏡觀察其攝食構造的形態發育，以探索此物種對於分布和取食的偏好。雖然蚌蟲在發育過程中外觀會有明顯變化，但過去少有探討其發育過程至成熟期的研究。實驗結果顯示，真湖蚌蟲於無節幼體階段會表現出正趨光性，但進入幼體期之後會轉為負趨光性。形態的轉變也大約在同樣時期，主要攝食構造由第二對觸角和大顎轉為較尾端的胸足、小顎、成熟大顎的組合。其攝食構造大多符合濾食性物種的特徵，但成體在前幾對胸足末端具有較堅固的梳狀構造，推測可能也具有刮食能力。從趨光性的結果可以推斷真湖蚌蟲於無節幼體期白天會游向水面，在有攝食能力後以浮游藻類及懸浮顆粒為食。進入幼體期後，真湖蚌蟲將因負趨光性聚集於水底，攝食方式可能濾食由底層懸浮或刮起的物質。在發育過程中的趨光性變化會造成生物的遷徙，可能可以幫助此物種更均勻分布於棲地中。此外，比較向天池三種共域大型鰓足類成體的形態發現，真湖蚌蟲分別與鵠沼枝額蟲 (Branchinella kugenumaensis Ishikawa, 1895) 及貓眼蚌蟲 (Lynceus biformis Ishikawa, 1895) 有相似形態，可能在食性上有競爭壓力；貓眼蚌蟲和鵠沼枝額蟲間則在形態上有明確差異，推測應有棲位分化現象。

關鍵字

照度 ； 功能形態學 ； 陽明山國家公園 ； 大型鰓足類 ； 無甲目 ； 平尾目

並列摘要

Phototaxis influences distribution and morphology is representative of function. While clam shrimps undergo an apparent change in appearance during development, ontogenic studies until maturation were seldom the center of attention. In this study, phototaxis through the nauplius, juvenile and adult stages with artificial lighting of different illuminances were tested and developmental morphology of feeding structures were observed with both light microscopy and SEM to explore their preference for general distribution and food. Results revealed that they first show positive phototaxis at the nauplius stage while changing into negative phototaxis from the juvenile stage on. Morphological change and a posterior shift in the main feeding structures also happen at the juvenile stage. The main feeding structures change from the second antenna and mandibles to the more posterior combination of sophisticated mandibles, maxillae and thoracopods. While the feeding structures mostly fit the description for filter feeding animals, scraping structures have also been found on the first several thoracopod pairs in the adult stage. The results imply that newly hatched E. braueriana nauplii will swim to the water surface during day time and filter feed on planktonic particles once having the ability to feed. Reaching the photo-negative juvenile stage, they may gather at the bottom, likely filtering suspended or scraped up particles as food source from this stage on. Ontogenic change in phototaxis leads to migration which could help this species distribute more even through the habitat, avoiding intraspecific competition. In addition, comparing adult feeding structures with the sympatric large branchiopods Siangtian Pond revealed potential competition for E. braueriana with the other two species, Branchinella kugenumaensis Ishikawa, 1895 and Lynceus biformis Ishikawa, 1895, and suggested resource partitioning between B. kugenumaensis and L. biformis.

並列關鍵字

illuminance ； functional morphology ； Yangmingshan National Park ； large branchiopod ； Anostraca ； Laevicaudata

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