Three Consecutive Generations of Nephridia Occur During Development of Platynereis dumerilii (Annelida, Polychaeta)

Morphology and Evolution of Animals, Philipps-Universität Marburg, Karl-von-Frisch-Strasse 8, Marburg, Germany.
Developmental Dynamics (Impact Factor: 2.38). 07/2010; 239(7):1967-76. DOI: 10.1002/dvdy.22331
Source: PubMed


Molecular data for nephridial development in polychaetes are not available yet. The scope of our work was to establish a reference system for future investigations using two markers for nephridial development: beta-tubulin as marker for cilia and alkaline phosphatase (AP) activity for secretory epithelia. The markers identified, unexpectedly, three consecutively forming generations of nephridia: (1) a transitory unciliated, but AP-positive head kidney, (2) a transitory larval nephridium, which undergoes a morphological transition from a protonephridium to a funnelled nephridium concomitant with the development of the coelomic cavity and finally, (3) the serially arranged metanephridia. The spatial arrangement of larval and definitive nephridia, revealed an up to now unknown developmental boundary between the synchronously forming larval and the serially proliferating definitive segments. Development of three consecutive sets of nephridia with different morphology and biochemical properties was unexpected and reveals an interesting multistep process in the development of excretory structures in Platynereis.

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Available from: Monika Hassel, Sep 18, 2014
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    • "In addition, two small Pdu-twist expressing patches can be observed on both sides of the 24 hpf larva (Fig. 2 (a, a′, arrows)). According to their location in the episphere, it is most convincing that these cells refer to the transitory larval head kidneys (Hasse et al. 2010). During further development, Pdu-twist-positive cells of the three bilateral domains expand around the ventral and dorsal chaetal sacs and give rise to the trunk musculature (Fig. 2 (c–i)), while the stomodeal expression increases in intensity and labels the developing pharyngeal muscles (Fig. 2 (c, e, arrowheads , i, g)). "
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    ABSTRACT: The basic helix-loop-helix transcription factor twist plays a key role during mesoderm development in Bilateria. In this study, we identified a twist ortholog in the polychaete annelid Platynereis dumerilii and analyze its expression during larval development, postlarval growth up to the adult stage, and caudal regeneration after amputation of posterior segments. At late larval stages, Pdu-twist is expressed in the mesodermal anlagen and in developing muscles. During adulthood and caudal regeneration, Pdu-twist is expressed in the posterior growth zone, in mesodermal cells within the newly forming segments and budding parapodia. Our results indicate that Pdu-twist is involved in mesoderm formation during larval development, posterior growth, and caudal regeneration.
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    • "In addition, both types do occur subsequently during ontogeny in certain polychaetes (e.g. [42]). The finding of a cilium in a podocyte of Lepidochitona corrugata – remarkably the first report of a podocyte bearing a cilium in a mollusc – lends substantial support to this concept. "
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