title for learn-about lugworms & relatives
  Food & feeding
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Research study 1
 


drawings showing differences in sand grain bacterial content in the feces of lugworms Abarenicola vagabunda and A. pacificadrawing of lugworm Abarenicola sp. in feeding postureA lugworm’s food consists of decaying organic matter, protists, small nematode worms, and a few bacteria.  However, considerable differences exist in the extent to which certain food items are eaten by different species.  For example, when Abarenicola vagabunda in the San Juan Island, Washington area eats sand with its complement of bacteria and diatoms it digests most of the bacteria and diatoms.  However, when Abarenicola pacifica eats the same sediments, considerably fewer bacteria and diatoms are digested.  Research done at Friday Harbor Laboratories, Washington indicates that less than 5% of the carbon material ingested is utilised by the worm. 

The worm's burrow, which is often located in anaerobic soils, is ventilated by peristaltic movements of its body.  Water is pumped through the burrow from the tail to head end, and it is this movement that softens the sand in the pocket area around the head.  The worm eats this softened soil by engulfing it with its large, frilly, expansible proboscis.  Defecation is prodigious and occurs on a cycle of 10-30min depending upon season and temperature. Hobson 1967 Biol Bull 133: 343; May 1972 Biol Bull 142: 71; see also Fauchald & Jumars 1979 Oceanogr Mar Biol Ann Rev 17: 193 for a review of feeding in polychaetes. Drawing on Right courtesy Fauchald & Jumars 1979.

NOTE  lit. “without air” G.  Lack of oxygen favours growth of hydrogen sulphide-producing bacteria that imparts a black coloration to the soils and a smell of rotten eggs

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Research study 2
  photograph of fecal casts of many lugworms in Crescent Beach, British ColumbiaBecause lugworms Abarenicola pacifica often live in anaerobic soils in which hydrogen sulphide-producing bacteria thrive, the irrigating of their burrows and pocket-sands with fresh, oxygen-rich water actually cleanses the soil and improves conditions for survival and growth of other microorganisms.  The soil, already rich in nitrogen and phosphorus, is now oxygenated and rid of potentially toxic hydrogen sulphide gas.  Feeding pauses of 6h or so allow bacterial food components to multiply several time.  Are the worms gardening the soils?  Studies at Friday Harbor Laboratories, Washington suggest that the answer is ‘yes’ and, owing to richer growth of edible microorganisms in the pocket area and low extraction of carbon during digestion, a lugworm’s feces may be actually richer in organics than the surrounding sediments.  Hylleberg 1975 Ophelia 14: 113.
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Research study 3
 

drawing showing tube features of a maldanid worm Axiothella rubrocincta in anaerobic sands of Tomales Bay, CaliforniaIn Tomales Bay, California the maldanid worm Axiothella rubrocincta inhabits 30cm-deep, U-shaped tubes formed from aggregated sand grains and mucus.  The worm combines feeding and burrowing activities to form its tube.  The tail end of the tube terminates in a defecation aperture located at the top of a fecal mound, while the head end terminates just below the sediment surface about 15cm distant (see drawing on Left). A funnel-shaped depression in the sediment marks the location of the feeding aperture of the tube a few cm beneath.  The head end of the tube is drawn out into a softish extension, as shown in the figure, which the author thinks functions to prevent sand from entering the tube when the worm withdraws its head after feeding.  The worm is able to move about in its tube for feeding, and for tube maintenance and cleaning.  Sediments and other matter entering the defecation aperture are pushed out by the worm expanding to the appropriate diameter and moving backwards using its setae to grip the inside of the tube.  drawing of maldanid worm Axiothella rubrocincta feeding on sediments

When feeding, the worm emerges from the sediment into the organics-rich funnel region, extends its mucus-covered proboscis, and draws large quantities of particulate matter into the gut by muscular movements of the proboscis aided by ciliary currents. Gut analyses show that Axiothella’s diet consists of detritus, diatoms, and small invertebrates, such as turbellarians, amphipods, and bivalves.  Kudenov 1978 J Exp Mar Biol Ecol 31:209.

NOTE  an adult tube is about 1cm Outside Diameter amd 0.5cm ID

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Research study 4
 

drawings of feeding parts of maldanid wormsIn a related article the same author compares feeding in Axiothella rubrocincta and 2 other maldanid species Clymenella californica and Praxillella pacifica in Tomales Bay, California.  All 3 species lnhabit tubes and deposit-feed in similar fashion using extensible probosces as shown in the drawings to the Left.  Feeding commences by rapidly protruding and retracting the probosces into and out of the substratum until its dilitancy changes, that is, the sand “puddles”). 

drawing showing feeding in a maldanid worm Praxillella pacificaAs shown in the drawing (on Right) for Praxillella pacifica, as the proboscis everts and inverts into the sediment, and puddles it, papillae on the proboscis work to force particles into the bucco-pharyngeal pocket.  It is at this time that edible particles are sorted from sediment particles and moved by ciliary currents into the esophagus.  Particles selected by large individuals of all 3 species are about 100µm in size. Kudenov 1977 Zool J Linnean Soc 60: 95.

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Research study 5
 

drawing showing method of collecting feces from a maldanid worm Axiothella rubrocinctaThe maldanid Axiothella rubrocincta is a common deposit-feeding polychaete along the Pacific coast of North America.  It lives on sand-flats in U-shaped burrows that may reach 30cm in depth.  Sand is consumed, processed, and defecated in a mound on the sediment surface.  How much sand does an adult Axiothella produce and what factors influence its rate of sediment processing?  This is determined in an in situ field study in Tomales Bay, California.  The author contains and measures the amount of defecated material over a 24-h period by pressing an open-ended plastic pipe into the sediment around the tail end of the worm.  By inserting filter papers with holes cut into their centres as shown in the diagram, the processed sediments can be retrieved, dried, and weighed. Factors that positively influence the rate of working of the sediments include temperature and salinity, while those that negatively influence rates include organic-carbon content and grain size.  The author concludes that A. rubrocincta is a non-selective deposit-feeder. Kudenov 1982 Mar Biol 70: 181.

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