Reproduction of Dodecaceria caulleryi (Polychaeta: Cirratulidae)

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Abstract
D. caulleryi breeds asexually by fragmentation and regeneration (schizogenesis), and sexually as an epitoke. Fragmentation is initiated in Sept.-Nov. in worms generally 40 segments long with the autotomy of the anterior 11-34 segments. Some 14-18 isolated segments are then autotomized in succession from the front of the remainder of the worm, leaving a residual 7-19 posterior segments. The anterior, individual segmental and posterior fragments produced in this way all begin regenerating; anterior regeneration of the posterior fragment is limited to 14 or fewer segments but posterior regeneration and growth of all fragments is unlimited though slow. When the segmental fragment has regenerated about 7 new anterior and posterior segments, these may be autotomized as secondary individuals and the original segment regenerates again. The anterior regenerate is more commonly shed than the posterior regenerate and not all segmental individuals engage in secondary fragmentation. The total production of new individuals by schizogenesis is 30-38 for each fragmenting worm, but gross production is 1/3 of this because only 35% of the population undergoes schizogenesis in any year. The schizonts remain in the parent burrow until spring when they disperse. They are unable to make their own burrows but depend on finding empty burrows probably of Polydora or other Dodecaceria; most fail to do so and there is a 95% mortality of schizonts, chiefly segmental and posterior individuals. By the start of the following season of fragmentation, primary anterior individuals are estimated to have reached a length of 48 segments and so are large enough to fragment again. Surviving primary and secondary segmental, and posterior fragments are no more than 30-32 segments long by the following autumn and are unlikely to reach a sufficient size to fragment until the 2nd year after their formation. A small number of epitokes representing no more than 1/6 the population per year, possibly less, are formed during the spring and summer. They are derived from large worms which failed to fragment in the previous autumn. Sexual reproduction has not been observed to contribute to the local population which to an overwhelming extent is maintained by asexual reproduction.

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