Ontogenic changes in phototaxis and feeding morphology of the clam shrimp Eulimnadia braueriana Ishikawa, 1895
Date Issued
2015
Date
2015
Author(s)
Liu, Jer-Yuh
Abstract
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.
Subjects
illuminance
functional morphology
Yangmingshan National Park
large branchiopod
Anostraca
Laevicaudata
Type
thesis
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