During the last 40 years time lapse photography has become a strong tool for in situ observations of marine and freshwater wildlife. We compared the validity of two low cost camera systems to analyze the filtration activity of Diplodon chilensis (Gray, 1828), the most common freshwater bivalve in southern Chile. One camera system (Nikon D300) was connected with an external flash, whereas the other system (GoPro Hero 3+) contained a permanent video light source. Size change of the total area of the exhalant siphon (ESA) of Diplodon individuals was used to track activity changes over time. Each ESA is expressed as the percentage of the maximum siphon opening of the corresponding specimen. The siphon of D. chilensis was completely closed for 3.4% ± 5.2% (mean ± SD) of the recording time and it shows a nearly completely opened siphon for 42.7% ± 22.9% of the recording time. The mean siphon opening was 68.3% ± 26.5% of its potential opening area. Although a red filter (permeable to wavelengths above 600 nm ) was placed in front of the video light source, the mobile fauna, especially Aegla abtao (Schmitt, 1942) and unidentified small fishes were highly attracted by the permanent light, whereas this effect was not visible when a flash light in intervals of 2 min was used. We conclude that both low cost cameras are very suitable for in situ time lapse observation of freshwater clams.
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