Reproduction, development, growth, and the length of larval life of P hascolosoma turnerae , a wood‐dwelling deep‐sea sipunculan

Specimens of the deep‐sea sipunculan P hascolosoma turnerae were retrieved over a 5‐year period from fibrous collectors placed for various time intervals at a depth of 520 m in the T ongue of the O cean, B ahamas. Sipunculans removed from the collectors were counted, weighed, and maintained in the laboratory at 14°C, where they were monitored for gametogenic activity, spawning, development, and growth. In a 2‐year study of seasonality, worms were most abundant in collectors retrieved in the spring and summer, and least abundant in the fall. Small animals (<0.01 g) were present in all seasons and represented ≥70% of the animals in winter collections. Large specimens (>0.16 g) were found from M ay through A ugust, but in markedly lower frequencies than small animals. Over the entire study, spawning was observed in the laboratory from A pril through A ugust. We inferred from analyses of size frequencies, growth, and spawning seasonality that settlement of the larvae occurs primarily from N ovember through A pril and that oceanic larval life could be as short as 7 months and as long as 12–14 months. Cleavage of fertilized eggs, as observed from laboratory spawnings, was spiral and holoblastic, resulting in a trochophore that transformed into a typical planktotrophic pelagosphera larva at 21 d. A few larvae survived as long as 2 months in the laboratory. This is the first study of biological processes in living sipunculans from the deep sea, and one of the first studies of living deep‐sea wood dwellers.