title for sandworm section of A SNAIL'S ODYSSEY
   
title for sandworms & relatives section of A SNAIL'S ODYSSEY
  Physiological ecology
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Research study 1
 

graph comparing salt loss in 3 species of nereid polychaetesA researcher at the University of California, Berkeley compares rates of salt loss in 3 species of commonly occurring nereid polychaetes Neanthes diversicolor, N. limnicola, and N. succinea.  The author approaches the study from a standpoint of strict comparative physiology, and there is little to interest students of ecology.  All 3 species inhabit brackish and estuarine waters and are adapted to, or tolerant of,  exposure to dilute salinities.  The main experiment involves immersing the worms for 1h in a measured quantity of distilled water and measuring the salt content of the bathing water afterwards.  Results show that salt loss is greatest in N. succinea and least in N. limnicola, and that loss scales with body mass (M) to a logarithmic exponent of 0.68-0.89, as would be expected from the three-quarters “surface rule”.   Other data not shown here includes loss rates in media such as sugar and urea solutions.  Smith 1963 Biol Bull 125 (2): 332.

NOTE  at the time of the study all 3 species were nominally classified in the genus Nereis, but have since been moved to Neanthes 

NOTE  the study is a preliminary one and, in the words of the author, is aimed at “evaluating the separate roles of body wall, nephridia, and gut” in the process of salt loss
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Research study 2
  photograph of scaleworm Halosydna brevisetosa courtesy Lovell & Libbie Langstroth, Californiadrawing of water flow in a scalewormPolynoid polychaetes or scaleworms bear a double row of overlapping scales or elytra on their dorsal surfaces.  The elytra are held in erect position to create a continuous roof along each side of the body.  Theories as to their function include sensory, protection, gas-exchange, luminescence, and egg-protection, depending upon the species in question.  For Halosydna brevisetosa, research at the Hopkins Marine Station, Pacific Grove, California confirms that the elytra are positioned to contain and direct water flow posteriorly, presumably for gas exchange.  The elytra themselves are not ciliated nor do they exhibit any fanning or pumping motions; rather, it is cilia on the dorsal epithelium and parapodial lobes that generate the water flow.  Water enters the sub-elytral area at the front and along the sides of the animal (see drawing).  If selected elytra are removed, the otherwise continuous anterior-posterior current is disrupted, and water escapes at the break.  Coelomic fluid just beneath the skin apparently moves counter-current with the ciliary-generated flow above.  Although not measured directly by the author, this counter-current arrangement would maximise gas exchange between the 2 fluids.  The author opines that the elytra would permit the currents to operate effectively even when the worms are wedged into crevices and other hideaways during daylight hours.  Lwebuga-Mukasa 1970 Bull So Calif Acad Sci 69: 154. Photograph courtesy Lovell & Libbie Langstroth, California.
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