Influences of nutritional state and temperature on suspension-feeding rates and mechanics in the spionid polychaete Polydora cornuta

Recently, Dubois et al. (2005; Mar Ecol Prog Ser 301:159-171) described the feeding mechanisms of the sabellariid polychaete Sabellaria alveolata and concluded that it is a ciliary suspension feeder that uses alternately a downstream-and an upstream-collecting system. We reinvestigated both the ciliated epithelia (scanning electron microscopy and transmission electron microscopy) and the function (video microscopy) of the tentacle crown of S. alveolata. We found that the tentacles of intact and undisturbed S. alveolata have a large number of stiff ciliary spikes, each flanked by an actively beating cirrus, but no structured flow of water is created and only minor local currents can be seen. Clearly, S. alveolata has neither a ciliary downstream-collecting system nor a proper ciliary pump as found in upstream-collecting bryozoans, phoronids and brachiopods. Our findings indicate that S. alveolata's tentacle crown is designed for passive suspension feeding and thus dependent on ambient currents to bring suspended food particles into contact with the tentacles. The significance of the conspicuous ciliary spikes remains unknown, but our observations suggest that mucus is involved in both capture and transport of food particles.

Section: Discussionsupporting

confidence: 68%

Section: Discussionmentioning

confidence: 99%

Feeding mechanism of the polychaete Sabellaria alveolata revisited: comment on Dubois et al. (2005)

Riisgård

Nielsen

2006

“…The fluid mechanical significance of the ciliary spikes remains unknown. However, the observations made by Riisgård & Nielsen (2006) suggest that mucus is involved in both the capture and transport of food particles in S. alveolata, possibly in a similar way as found in spionid polychaetes (Shimeta et al 2004). …”

Section: Ciliary-spike Suspension Feedingmentioning

confidence: 92%

Particle capture mechanisms in suspension-feeding invertebrates

Riisgård¹,

Larsen²

2010

214

179

A large number of suspension-feeding aquatic animals (e.g. bivalves, polychaetes, ascidians, bryozoans, crustaceans, sponges, echinoderms, cnidarians) have specialized in grazing on not only the 2 to 200 µm phytoplankton but frequently also the 0.5 to 2 µm free-living bacteria, or they have specialized in capturing larger prey, e.g. zooplankton organisms. We review the different particle capture mechanisms in order to illustrate the many solutions to the common problem of obtaining nourishment from a dilute suspension of microscopic food particles. Despite the many differences in morphology and living conditions, particle capture mechanisms may be divided into 2 main types. (1) Filtering or sieving (e.g. through mucus nets, stiff cilia, filter setae), which is found in passive suspension feeders that rely on external currents to bring suspended particles to the filter, and in active suspension feeders that themselves produce a feeding flow by a variety of pump systems. Here the inventiveness of nature does not lie in the capture mechanism but in the type of pump system and filter pore-size. (2) A paddle-like flow manipulating system (e.g. cilia, cirri, tentacles, hair-bearing appendages) that acts to redirect an approaching suspended particle, often along with a surrounding 'fluid parcel', to a strategic location for arrest or further transport. Examples include (1) sieving (e.g. by microvilli in sponge choanocytes, mucus nets in polychaetes, acidians, and salps among others), filter setae in crustaceans, 'ciliary sieving' by stiff laterofrontal cilia in bryozoans and phoronids; and (2) 'cirri trapping' in mussels and other bivalves with eu-laterofrontal cirri, ciliary 'catch-up' in bivalve and gastropod veliger larvae, some polychaetes, entroprocts, and cycliophores. These capture mechanisms may involve contact with a particle, and possibly mechanoreception or chemoreception, or may include redirection of particles by the interaction of multiple currents (e.g. in scallops and other bivalves without eu-laterofrontal cirri). Based on the review, we discuss the current physical and biological understanding of the capture process and suggest a number of specific problems related to particle capture, which may be solved in the future using advanced theoretical, computational and experimental techniques.

“…These different geometries might alter the rates at which particles are contacted in a turbulent boundary layer and the rates at which contacted particles are retained during transport along a worm's palps (Shimeta & Jumars 1991, Shimeta & Koehl 1997). Recent measurements of particle contact and retention by juvenile P. cornuta show that retention is highly variable and can be enhanced when worms have been starved (Shimeta et al 2004). The rates of particle contact and retention of S. benedicti have not been studied in relation to flow speed, but our growth-rate data suggest that S. benedicti might have reduced retention in faster flows relative to P. cornuta.…”

Section: Discussionmentioning

confidence: 99%

“…Smaller pump-driven flumes that are well suited for making high-magnification video observations of particle capture by individual worms (e.g. Shimeta & Koehl 1997, Shimeta et al 2004 do not facilitate measuring the growth of dozens of worms simultaneously. To date, only Taghon (1992) and Taghon & Greene (1992) have measured rates of feeding and growth simultaneously in different flow speeds.…”

Section: Discussionmentioning

confidence: 99%

Growth rates of interface-feeding polychaetes: combined effects of flow speed and suspended food concentration

Hentschel

Larson²

2005

Most spionid polychaetes switch from deposit feeding to suspension feeding as the current speed and the flux of suspended food particles increase. Previous experiments testing the effects of flow on the growth rates of facultative, interface feeders have been limited to a single concentration of suspended food. We performed an experiment in counter-rotating annular flumes set to one of 3 flow speeds and 2 concentrations of suspended microalgae. This design allowed the horizontal flux of algae (i.e. concentration multiplied by current speed) to be manipulated by 2 independent means. The relative growth rates of Polydora cornuta and Streblospio benedicti were measured during a series of 3 d runs in replicate flumes set to each of the 6 food-flow treatments. Sediment collected from the worms' field site was added to each flume as a food source for deposit-feeding worms. The 3 flow speeds (U 5mm = 3, 6, or 12 cm s -1 , where U 5mm = velocity measured 5 mm above bottom) were all slower than the sediment's critical erosion velocity (U 5mm = 13 cm s -1 ; shear velocity U * = 0.9 cm s -1 ). P. cornuta grew significantly faster as flow increased in the lower algal concentration, but not in the higher one. The higher algal concentration led to faster growth of P. cornuta at the 2 slower flows, but there was no effect of algal concentration at the fastest flow speed. Overall, the growth rate of P. cornuta increased as the horizontal flux of suspended food increased up to a value that led to a maximal growth rate, regardless of whether the flux of suspended food was manipulated by flow speed or by algal concentration. In contrast, S. benedicti did not show significant relationships between growth rate and either flow speed, algal concentration, or the overall flux of suspended food. The data demonstrate that the juvenile growth rates of some interface-feeding spionids, such as P. cornuta, can be tied strongly to hydrodynamic conditions that favor passive suspension feeding, while the growth rates of other interface-feeding spionids, such as S. benedicti, can be less sensitive to flow.KEY WORDS: Benthic boundary layer · Deposit feeding · Flume · Growth rate · Polydora · Spionid polychaete · Streblospio · Suspension feeding Resale or republication not permitted without written consent of the publisher