Architecture of, and water circulation and flow rate in, the house of the planktonic tunicateOikopleura labradoriensis

Abstract

Abstract. The gelatinous house of Oikopleura labradoriensis (Tunicata, Appendicularia), collected from the docks of Friday Harbor Laboratories, University of Washington, USA, in 1984USA, in , 1986USA, in and 1990, was examined in vivo by stereomicroscopy and strobe-light macrophotography, and after fixation and processing for light and electron microscopy. In addition to confirming previous knowledge and adding new information on structural organization of the oikopleurid house, this study presents quantitative data on important aspects of its function. Particles small enough to pass through the inlet filters (pore width ~ 13 gin) were concentrated between differently constructed upper and lower food-concentrating filters (pore widths 0.18 and 0.24 gm, respectively). These filtes were held together by an intermediary screen of widely separated ribbon-like filaments. Water sieved through the filters left the house through a pressure-regulated exit valve. However, the intermittent activity of the tail pump and the elasticity of the house caused frequent refluxes of water that cleared both inlet filters and foodconcentrating filter screens of adhering particles. During these refluxes the food-concentrating filters usually collapsed and compacted the trapped particles into coarser aggregates. With each pumping cycle the particles and aggregates were brought closer to the midline. From here they were periodically drained into the mouth of the organism through a medial food-collecting tube, to be recaptured in a pharyngeal feeding filter secreted by the organism's endostyle. Based on the size and movements of the tail within the close-fitting tail chamber, a water flow rate of ~ 0.84 ml min-1 was calculated for medium-sized houses (belonging to individuals with trunk length of ca.

Retention efficiency of sub-micrometer particles by the pharyngeal filter of the pelagic tunicate Oikopleura vanhoeffeni

“…There is also the possibility that the small beads formed clumps. Although there was no evidence of clumping of any of the beads in suspension in the experimental chambers, lt is possible that they may have aggregated within the house before ingestion (Flood 1991). We have no direct measurement of particle state within the house.…”

“…The feeding mechanism of appendicularians is complex, with external pre-filters and food-concentrating filters in the house, and an internal pharyngeal filter within the animal (Deibel 1986, Flood 1991. The external filters are secreted by the animal and are subject to clogging, leading eventually to the animal abandoning its house.…”

“…Empirical retention spectra may approach an asymptote at small particle size set by the degree of particle collection by direct interception. In addition, particles that pass through the pharyngeal filter are not lost from the house but flow into the tail chamber to be recycled through the food-concentrating filter (Deibel 1986, Flood 1991. Thus, it is theoretically possible that, given unlimited cycles through the house, a particle of infinitely small size eventually will be captured by direct interception onto a fiber of the pharyngeal filter.…”

Absorption efficiencies and biochemical fractionation of assimilated compounds in the cold water appendicularian Oikopleura vanhoeffeni

“…At the end of the incubation, we removed 200 ml of seawater from the jars using a syringe, carefully avoiding fecal pellet contamination, and passed the water through a glass fiber filter (GF/F). The animals were gently sucked into a widemouthed pipette through the escape chamber of the house (Flood 1991) and put into GF/F-filtered seawater on ice. They were then serially transferred through two washes in GF/F-filtered seawater to reduce the number of attached algae.…”

Particle capture mechanisms in suspension-feeding invertebrates

“…Fritillaria borealis (Flood 2003). Of the 3 families of larvaceans, the Oikopleuridae is the best known (Jørgensen 1966, Alldredge 1977, Deibel et al 1985, Deibel 1986, Deibel & Powell 1987, Flood 1991, Acuña et al 1996. The sinusoidal beat of the animal's tail draws water into the balloon-like gelatinous house through 2 in-current filters of coarse mucus mesh which pre-screen the water (Fig.…”