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Hatching and earliest larval stages of the priapulid worm Priapulus caudatus
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology, Palaeontology group.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
2009 (English)In: Invertebrate biology., ISSN 1077-8306, E-ISSN 1744-7410, Vol. 128, no 2, 157-171 p.Article in journal (Refereed) Published
Abstract [en]

Here we describe the hatching and morphology of the earliest larval   stages of the priapulid worm Priapulus caudatus for the first time. The hatching larva differs considerably from previously described larvae  not only in its general body shape but also in its lack of a proper lorica including the typical lorica tubuli. Furthermore, no mouth opening or pharyngeal teeth have formed as yet, and the number and  arrangement of scalids differ from that of later larvae. The hatching larva molts and emerges as the first lorica larva. This larva partially   resembles earlier described lorica larvae, but there are a number of  important differences; the first lorica larva is smaller, and the mouth   opening as well as pharyngeal teeth are still yet to form. The second   lorica larva is equipped with four rings of pharyngeal teeth; it shows striking similarity to the previously described larva of P. caudatus,  i.e., the larva-type 2, only differing in the scalid pattern. We conclude that the first two larval stages of P. caudatus have not been described previously. We suggest that discrepancies between the earliest lorica larvae described here and in earlier publications might depend on sub-speciation or ecophenotypic modification of larvae collected from different localities. Our findings highlight the  importance of studying the development of non-model organisms such as priapulids under controlled laboratory conditions.

Place, publisher, year, edition, pages
2009. Vol. 128, no 2, 157-171 p.
Keyword [en]
Priapulida, Scalidophora, Cycloneuralia, Ecdysozoa, development
National Category
Biological Sciences
URN: urn:nbn:se:uu:diva-97376DOI: 10.1111/j.1744-7410.2008.00162.xISI: 000266490400005OAI: oai:DiVA.org:uu-97376DiVA: diva2:172288
Available from: 2008-05-22 Created: 2008-05-22 Last updated: 2015-05-05Bibliographically approved
In thesis
1. Aspects of priapulid development
Open this publication in new window or tab >>Aspects of priapulid development
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The phylum Priapulida is a small group of marine worms that is allied with the nematodes, kinorhynchs, loriciferans and nematomorphs in a clade called the Cycloneuralia or Introverta. Together with the arthropods they are generally considered to comprise the Ecdysozoa, a clade of moulting animals. A number of recent priapulid species possess features that resemble the predicted Ecdysozoan ancestor. In addition, recent molecular studies have also shown that they are basal within the Ecdysozoa/Cycloneuralia (Garey 2001, Webster et al. 2006). Their putative basal position thus makes priapulids highly interesting research objects for understanding the evolution of Ecdysozoa.

Earlier investigations of the early embryology of the priapulid Priapulus caudatus are critically revised with the aid of modern techniques and equipment, confirming earlier studies that the early cleavages are highly symmetrical, total, subequal, radial and stereotypical. New results show that up to the sixth cleavage, the spindles are oriented along the animal/vegetal axis at both poles. This unique cleavage pattern has only limited similarities to other animals. During the sixth cleavage two cells move inwards and gastrulation commences. If the mesoderm is derived from both cells, its origin differs from that of many other protostomes.

Two previously undescribed larval stages of P. caudatus; the light bulb shaped hatchling and the first lorica larva are described. The second lorica larva superficially resembles the previously described type 2 lorica larva (Higgins et al 1993). Differences between the second lorica larva and the type 2 lorica larva, with respect to possible ecophenotypical variation and sub-specialization, are described.

Preliminary data are presented on musculature development of P. caudatus. Preliminary data have also been obtained on the early development of a second priapulid, Halicryptus spinulosus. Comparison of Halicryptus and Priapulus may help to resolve developmental ground pattern of the priapulids.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 45 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 451
Earth sciences, Priapulus caudatus, Priapulida, Ecdysozoa, larval development, embryology, Geovetenskap
urn:nbn:se:uu:diva-9004 (URN)978-91-554-7240-5 (ISBN)
Public defence
2008-06-13, Norrlands, Geocentum, Villavägen 16, 75236, Uppsala, 10:00
Available from: 2008-05-22 Created: 2008-05-22Bibliographically approved

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Janssen, RalfBudd, Graham E.
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