Developmental transformations in a normal series of embryos of the sea lamprey Petromyzon marinus (linnaeus)
Article first published online: 12 MAY 2003
Copyright © 2003 Wiley-Liss, Inc.
Journal of Morphology
Volume 257, Issue 3, pages 348–363, September 2003
How to Cite
Richardson, M. K. and Wright, G. M. (2003), Developmental transformations in a normal series of embryos of the sea lamprey Petromyzon marinus (linnaeus). J. Morphol., 257: 348–363. doi: 10.1002/jmor.10119
- Issue published online: 12 MAY 2003
- Article first published online: 12 MAY 2003
- van der Leeuw Fonds
- Natural Sciences and Engineering Research Council (NSERC) of Canada
Lamprey development is of interest to evolutionary biologists because it can inform our understanding of primitive vertebrate developmental patterns. In this study, we describe and illustrate some of the principle landmarks of organogenesis in the embryonic sea lamprey Petromyzon marinus L. at different chronological ages. We examined 63 fixed embryos spanning Piavis developmental stages 11–18+ (5–70 days postfertilization) by gross observation and histology. This period begins at late neurulation stages and ends with the formation of the larva (ammocoete). A significant difference with some previous accounts is that the anus develops not from a persistent blastopore, but by secondary canalization and proctodeum formation at the former site of the blastopore. Further, we show that the ciliated bands of the pharyngeal roof originate in the esophagus, distinguishing it from the intestine. We clarify the epithelialization of the gut, showing that the secondary gut cavity is progressively epithelialized from each end. We identify possible germ cells in the coelomic and cloacal walls. Balfour's “subnotochordal rod” is lacking in our specimens; we suggest that he may have misinterpreted the corpus adiposum. Our study is of potential value to the growing number of biologists interested in lamprey development and provides a character set that will be used : 1) in a phylogenetic study of vertebrate development, and 2) to prepare a staging series for the lamprey based on parsimony analysis. J. Morphol. 257:348–363, 2003. © 2003 Wiley-Liss, Inc.