Comparative study of water-processing in two ciliary filter-feeding polychaetes (Ditrupa arietina and Euchone papillosa) from two different habitats

• A comparative study of feeding rates and structures was made with the 2 ciliary filter-feeding polychaetes Ditrupa arietina and Euchone papillosa from the Mediterranean Sea (Gulf of Lions, France) and the Gullmarsfjord (Sweden), respectively. The feeding rate (clearance) was measured as the volume of water cleared of 6 pm diameter flagellate cells (Rhodomonas sp.) per unit Lime. Most experiments were conducted at algal concentrations equivalent to about 0.4 to 3.8 mug chlorophyll a l(-1). The clearance rates of 'standard' 1.5 mg dry wt E. papillosa and 'standard' 3.0 mg dry wt D. arietina showed that the maximum weight-specific clearance rate was 114.7 ml h(-1) mg(-1) for E. papillosa and about 7 times lower, 15.7 ml h-1 mg-1, for D. arietina. A relative large tentacle crown in E. papillosa, resulting in the higher specific clearance rate, may be the evolutionary result of 'minimal scaling' and adaptation to extremely low food concentrations. When the algal concentration was increased from 2000 to 10 000 cells ml(-1) a 50% decrease in the clearance rate was observed in D. arietina, presumably because the gut capacity was exceeded. A more pronounced tendency to become satiated was found for E. papillosa. No tendency to reduce the filter-feeding activity at even very low algal concentrations was noticed in the 2 polychaetes, and the filtering activity of both worms seems to be a basically continuous process. Video-microscope observations of E. papillosa showed that suspended algal cells approaching the pinnules suddenly accelerate and move through an arc of over 180degrees to be delivered on the frontal side of the pinnule. The transfer takes place at a maximum distance (radius) of about 25 mum from the pinnule. Scanning micrographs show the compound lateral cilia to be 20 to 25 mum long in both D, arietina and E, papillosa and to consist of 1 row of 4 cilia. The feeding current is generated by these compound cilia, which, during their power stroke, catch up with the particles.

Subject headings

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Keyword

suspension-feeding

filtration rates

particle -retention mechanism

adaptation to the environment

feeding structures

ascidian ciona-intestinalis

banyuls-sur-mer

mytilus-edulis

physiological regulation

filtration-rate

energy-cost

biochemical-composition

sabella-penicillus

ectoprocts bryozoa

oxygen-consumption

Publication and Content Type

ref (subject category)

art (subject category)