FEEDING BEHAVIOR AND DIET OF THE CIRRATULID, CIRRIFORMIA FILIGERA (DELLE CHIAJE, 1825)
Pardo, E. V.1 & Amaral, A. C. Z. 2
1 Universidade Estadual Paulista- UNESP - Pós-graduação Zoologia, Instituto de Biociências, 13506-900, Rio Claro, SP, Brazil
2 Universidade Estadual de Campinas - IB/Depto. de Zoologia, C.P. 6109, 13083-970, Campinas, SP, Brazil
Cirriformia filigera is frequently present in sandy or mixed-substrate bottoms. The purpose of the present study is to identify the main food components encountered in the gut content of C. filigera, as well as to study its feeding behaviour. For examination of gut content, 188 specimens were examined; 49 of them were found to contain at least some material in the gut. Most of the examined specimens (57.14%) showed a repletion degree (R.D.) of 0.25. Only in one specimen was full, i.e., the R.D. was 1, while in the rest the R..D. was 0.5. Among 22 identified food items, the diatoms Coscinodiscus sp. (24 specimens) and Grammatophora marina (16 specimens) were the most abundant. The ocurrence frequency of each item in the gut content, sand was the most frequent (100%), followed by unidentified diatoms (18.18%) and the diatoms Coscinodiscus sp. (14.28%), Biddulphia sp. (12.24%), Surirella sp. (12.24%) and finally Bacillaria sp. (10.28%). The rest of the items had a frequency of ocurrence lower than 8.5%. Observations on feeding behavior study were made with a stereoscope microscope equipped with carefully controlled light to reduce the light intensity and stress, showed that C. filigera moves slowly in horizontal position few milimeters at a time at the sediment-water interface. During such a movement, all tentacles and gills were directed backward, and the prostomium seemed to be free. The worms were observed to be moving above the sediment, with the aid of the prostomium (using sideway movements), collecting and transporting sand grains of similar sizes posteriorly. These grains were passed along the ventral region of the animal forming a string until it reached the medium region of the body. At this point, the tentacles and gills take over, moving the sand grains slowly to the posterior on the dorsal side of the animal, and covering this area with the grains. Some of the sand particles were taken up by the mouth, like a pump as the sand. When the animal are completely buried (apparently not feeding in this position), some of the gills (about 8) were found to be out of the sediment. The results of the laboratory observations and the gut content analysis of C. filigera showed that this is a deposit-feeder species and it selects the size of the sand particles during the feeding process.