title for sandworms & relatives section of A SNAIL'S ODYSSEY
  Foods & feeding
 

photograph of nereid polychaete with proboscis parly exposedLarval polychaetes feed on phytoplankton or other organic particles. Adult sandworms such as Nereis spp. mainly eat algae, while other species are omnivorous or strictly carnivorous.  The large jaws may be used to tear apart food, but are primarily used for defense.

 

 

Sandworm Nereis sp. with
proboscis partly everted 1.4X

 

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Research study 1
 

photograph of sandworm in its tube with a piece of green alga Ulva as part of its gardenAlthough usually thought of as being free-living, nereid worms Nereis vexillosa and Platynereis bicanaliculata tend to inhabit “home” locations consisting of a tube constructed of mucus and embedded debris.  Both species are omnivores, and feed on small invertebrates and various types of algae.  In San Juan Island, Washington both species engage in an unusual “gardening” behaviour that involves attaching bits of drift algae to their tube openings.  The algae are mostly the green ulvaceans, Ulva, Monostroma, and Enteromorpha.  The worms respond to the presence of pieces of algae drifting in front of their tubes by emerging, capturing the pieces, and attaching them to the tube opening using sticky mucus.  Periodically the worm tears a piece of alga from its free edge and eats it.  The plants grow more quickly in their attached locations, but not always fast enough to meet the harvesting activities of the worms. Other benefits to the worms from their "gardens" is that summer temperatures in the sediments are a few degrees cooler beneath the algal cover than in nearby experimentally cleared areas.  photograph of sandworm Nereis vexillosa Moisture levels are also higher beneath the algal layers created by the worms.  Negative features of the worm’s gardening activities, however, include anoxic soils being present immediately beneath the lowermost algal blades, rather than being 1-3cm beneath the sediment surface in the absence of the algae, and blocked access of other infaunal organisms, for example, maldanid worms, to oxygenated water.  In summary, the algal-attachment behaviour provides a food source, and modulates temperature and desiccation stresses for the worms but, in that it creates favorable habitat for the algae, it changes the community dynamics of the mudflat.  Woodin 1977 Mar Biol 44: 39.

 

Sandworm Nereis vexillosa in
an under-rock habitat 1.6X

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Research study 2
 

drawings of gut morphology of the carnivorous worm Ophiodromus pugettensisPrey items identified in gut contents of the algal-mat/sediment-inhabiting hesionid worm Ophiodromus pugettensis include harpacticoid copepods and several species of small polychaete worms.  Ophiodromus is a carnivore with a massively muscled pharynx that can rapidly open to suck in prey organisms. No jaws or teeth arm the pharynx and most prey appear to be sucked in relatively undamaged.  The pharynx is in 2 parts, with valves sited at the anterior end of each double section (see drawings). The pharynx can be everted as far as the middle valve by contraction of the pharynx protractor muscles.  Food matter is sucked first into the anterior part of the pharynx and then, with sequential opening and closing of the valves, it is sucked into the posterior part and afterwards is passed to the intestine.  The pharynx is withdrawn by contraction of the pharynx retractor muscles. The muscularity of structure and extreme rapidity of eversion indicates that the pharynx is adapted for a diet of small, fast-moving animals. 

Studies at Friday Harbor Laboratories, Washington on feeding behaviour of Ophiodromus show that prey are detected and evaluated as food by vibration sensing, direct contact, and distance chemoreception.  Size of prey seems to be the most critical factor influencing selection.  Food items too large to be ingested are spat out and not approached again.  The worm is able to detect distant prey by their vibration, and also seems able to judge their direction.  It is likely, then, that vibration is more important than vision in locating prey.  Even though Ophiodromus has 2 pairs of eyes, the eyes are oriented photograph of 2 hesionid worms Ophiodromus pugettensis living symbiotically on the undersurface of a bat star Patiria miniataupwards, and forward vision to detect prey seems unlikely.  Shaffer 1979 Biol Bull 156: 343.

NOTE this common worm is known also as Podarke. It may be free-living on muddy bottoms or symbiotic in the ambulacral grooves of sea stars such as Patiria miniata


Two hesionid worms Ophiodromus pugettensis living
symbiotically on a bat star Patiria miniata 0.5X

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Research study 3
 

drawing and photo of a larval hesionid worm Ophiodromus pugettensis showing feeding parts, courtesy Phillips & Pernet 1996 Biol Bull 191: 199photograph of larva of scaleworm Arctonoe vittata after it has ingested 2 polystyrene beads of 40um diameter eachLarvae of scaleworms are different from other polychaete larvae in that they lack a metatroch and food groove, and possess a prominent bundle of long cilia attached at the left side of the mouth known as the oral brush; hence, their mechanism of feeding differs from other polychaetes (see drawing and photo on Left).  Investigations at Friday Harbor Laboratories, Washington on feeding of larval scaleworms Arctonöe vittata using videotaping methods indicate that food particles are caught up in the locomotory/feeding current generated by the ciliated prototroch. As a food particle rolls ventrally the larva appears to recoil briefly from a reversal of ciliary beat, and this causes the particle to end up near the mouth where is ingested. The authors could not see the oral brush come into play, but its prominent size suggests that it may entrain particles in flow patterns generated by it, or it may be extended outwards to capture a particle and direct it into the mouth.  The larva is only about 100µm in diameter, but can ingest particles as large as 60µm.  Phillips & Pernet 1996 Biol Bull 191: 199.

NOTE  collected from mantle cavities of keyhole limpets Diodora aspera

NOTE when the larvae are in unstirred culture dishes they tend to become tethered by mucous strands to the bottom and, attached in such a way, lend themselves well to being fed and
videotaped

 

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Research study 4
 

photograph of snorkel arrangement in scaleworm Sthenelais berkeleyidrawing of scaleworm Sthenelais berkeleyi showing the relationship of snorkel to sediment surface An interesting feeding behaviour is described for predatory scaleworms Sthenelais berkeleyi at the Friday Harbor Laboratories, Washington.  The worm apparently is an ambush-type predator, lying in wait just beneath the surface layer of sediment and waiting for prey to happen by.  Long-duration burial is enabled by the worm creating a respiratory tube or snorkel with setae and other body parts that opens to the sediment surface antero-dorsally (see photograph).  Note that in addition to setae, the other parts comprising the snorkel are a median antenna and dorsal cirri.  Water is drawn into the snorkel by the beating of cilia on the parapodia of the first segment.  The current is driven by general body cilia, and moves between the body wall and elytra, exiting either at the back end or ventrally (see drawing on Right). The author thinks that the water flow provides for gas exchange during the worm’s long period of burial.  In captivity the worm will eat polynoid scaleworms, and it is likely that these and similar surface-crawling polychaetes, small crustaceans, and perhaps holothuroids may comprise Sthenelais’ natural diet.  Pernet 2000 Invert Biol 119: 147. 

NOTE  these are large worms, up to 40cm in length, and are carnivorous.  The author is able to observe behaviour in only a single laboratory specimen of this uncommon species

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