Larval development and metamorphic behaviour of the subtropical spionid polychaete Pseudopolydora vexillosa

Although newly described, Pseudopolydora vexillosa is one of the most conspicuous surface-feeding spioniform polychaetes in subtropical waters. This is the first report on larval growth and metamorphosis of R vexillosa. Newly hatched (3-chaetigers stage) larvae of P vexillosa reached metamorphic competence at 12-17 chaetigers stage when fed with Chaetoceros gracilis or Dunaliella tertiolecta at a concentration of similar to 10(5) cells ml(-1) for 6 to 8 days at 32 psu and 27 degrees C. Larvae on these two diets achieved comparable levels, of approximately 70% metamorphosis. On the other hand, larvae fed with Isochrysis galbana or starved in 0.22 mu m filtered seawater never reached competence during the 10 days of study. The effect of organic matter on larval substrate selection was examined using glass beads, manipulated sediments and natural sediments. A significantly higher percentage of larvae metamorphosed on glass beads that had been submerged in unfiltered natural seawater for 5 days as compared to the control; when manipulating the organic content of sediment as a substratum, significantly more larvae metamorphosed in 100% natural sediment, compared with 0%, 25%, 50%, and 75% natural sediment mixed with different portions of ashed sediment. Surprisingly, with natural undisturbed surface sediment sampled along a transect perpendicular to a sewage discharge site, these laboratory bioassays demonstrate that the larvae of P. vexillosa are capable of responding to sedimentary cues in complex ways to find a habitat suitable for metamorphosis and survival. (C) 2008 Elsevier B.V. All rights reserved.