Respiration and ingestion rate of different sized Daphnia pulex fed on four algal species | Dihanje in prehranjevanje različno velikih osebkov vrste Daphnia pulex s štirimi vrstami alg

English. Respiration rate and ingestion rate for four different algal species (Scenedesmus quadricauda, Asterionella formosa, Aphanizomenon flos-aquae and Planktotrix rubescens) of different sized Daphnia pulex were measured in the laboratory. Population of D. pulex grew maximally when it fed S.quadricauda, but the presence of P. rubescens and A. flos-aquae caused negative population growth rate. Ingestion rates increased with increasing body size for all in- vestigated algae; the lowest b value was obtained for S. quadricauda and the highest one for P. rubescens. The amount of ingested carbon exceeded the required amount for standard metabolism in both small and large sized individuals fed all four algal species. Relatively higher amount of ingested A. flos-aquae and P. rubescens in comparison with A. formosa and S. quadricauda and the results of the growth experiments indicate that the inhibitory effect of filamentous blue-green algae on D. pulex is more due to toxicity, low assimilation efficiency or/and inadequate composition than incapability of ingestion due to mechanical interference with filaments.

Slovenian. V laboratoriju smo pri različno velikih osebkih Daphnia pulex merili dihanje in stopnjo hranjenja s štirimi različnimi vrstami alg (Scenedesmus quadricauda, Asterionella formosa, Aphanizomenon flos-aquae and Planktotrix rubescens). Populacija D. pulex je najbolje uspevala pri hranjenju z algoS. quadricauda, v prisotnosti vrst A. flos-aquae in P. rubescens pa smo opazili negativno rast populacije. Stopnja hranjenja se je povečevala z naraščajočo telesno velikostjo pri vseh vrstah alg; najnižjo vrednost b smo dobili pri hranjenju s S. quadricauda, najvišjo pa s P. rubescens. Količina zaužitega ogljikaje presegala porabo za standardni metabolizem pri hranjenju z vsemi štirimi vrstami alg. Večje količine zaužitih vrst A. flos-aquae in P. rubescens v primerjavi z vrstama A. formosa in S. quadricauda in rezultati rastnih poskusov kažejo, da je inhibitorni vpliv nitastih modro-zelenih alg na osebke vrsteD. pulex bolj posledica strupenosti, nizke asimilacijske učinkovitosti ali/in neustrezne sestave kot pa nezmožnosti zaužitja zaradi težav, ki bi jih povzročala nitasta oblika alg.