title for learn-about lugworms & relatives
  Interactions with other infaunal species
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Research study 1

Mudflats in Mitchel Bay, San Juan Island, Washington host over a dozen infaunal polychaete species, of which four are relatively large and/or quite common.  Transect surveys show that seasonal abundances of the 4 species are quite variable, a situation attributed by the author to events such as mortality after spawning and differences in reproductive success.  Experiments using mesh cages to exclude predators on the mudflat, and manipulation of densities of the different species, demonstrate the presence of both intra- and interspecific competition between the different species for space. The paper has a wealth of data, most in tabulated form, and too complex to attempt to summarise here. Woodin 1974 Ecol Monogr 44: 171.

NOTE  these are Lumbrineris inflata, Platynereis bicanaliculata, Axiothella rubrocincta, and Armandia brevis.  The first 2 species are herbivores, eating mainly green algae and building temporary and permanent tubes, respectively.  The last 2 species are deposit-feeders, the first building permanent tubes while the last burrows freely in the surface sediment

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Research study 2

With its large size, and commensurately extensive feeding and defecating activities, does the maldanid worm Axiothella rubrocincta competitively displace other infaunal worms?  This is tested at Tomales Bay, California using a guild of polychaete worms consiting of A. rubrocincta and 6 or more species of smaller spionid polychaetes, including Pseudopolydora paucibranchiata.  Densities of all worms are monitored within and outside of Axiothella beds over a period of 13mo.  Additionally, Axiothella individuals are placed in a simulated sandflat in the laboratory and their feeding behaviour monitored at different concentrations of organic food particles over a 10-wk period.  Other types of manipulative experiments are done including placing spionids P. pacibranchiata from the field in laboratory trays containing different experimental densities of Axiothella (0, 160, and 320 individuals . m-2) in order to assess their survival over 1mo in sympatry with Axiothella. Results show that the various species feed on the same types of organic-mineral aggregates, and food-exploitation occurs between the competitively dominant Axiothella and the other species, both in the lab and in the field.  Most of the spionid species are significantly less abundant within the Axiothella patches than without.  Additonally, when living in sympatry with Axiothella, P. paucibranchiata has higher mortality and lower larval recruitment, possibly indicating interference competition.  In addition to these direct effects, by reducing the quantity of food available to the other spionids, Axiothella indirectly increases their susceptibility to predation.  What is thought to happen is that by having to reach further out of their tubes to find food,  the spionids may increase the probability of attack by predatory fishes.  Weinberg 1979 Mar Ecol Progr Ser 1: 301.

NOTE  in addition to being of smaller size, the spionids inhabit vertical tubes as opposed to the U-shaped tubes of Axiothella, and feed using their palps as opposed to proboscis on organic particles at the sediment-water interface

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