Algal Exploitation by Tadpoles — an Experimental Approach

This study examined the exploitation of several species of algae and other organisms by Rana dalmatina larvae, by comparing nutrient contents and pigment degradation of food algae to faeces and changes in larval weight. Tadpoles gained weight when fed Oscillatoria limosa mats collected from the field. The high inorganic content of the Oscillatoria mats, combined with gut peristalsis, may have faciliated the cracking of the tough cell walls. When fed Cladophora and Spirogyra , ash‐free dry weight and protein content of tadpole faeces decreased whilst chlorophyll‐degradation products increased in the faeces relative to the food. With Scenedesmus as food, pigment degradation occurred after gut passage. Tadpoles tended to gain weight when fed Scenedesmus or Aphanizomenon . The epipelic diatoms, Gongrosira , and the planktonic flagellates Cryptomonas and Chlamydomonas were exploited only in traces. Food was better exploited after repeated gut passage, as evidenced by reductions in organic contents, proteins and carbohydrates in the faeces.