The Natural History of Model Organisms: Amphioxus as a model to study the evolution of development in chordates
- Biology and Evolution of Marine Organisms (BEOM), Stazione Zoologica Anton Dohrn, Italy
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, France
Figures
Figure 1
Deuterostome phylogeny and body plan for amphioxus.
(A) Deuterostomes are subdivided into ambulacraria (echinoderms and hemichordates) and chordates (cephalochordates, tunicates and vertebrates). Cephalochordates, which are commonly known as amphioxus or lancelets, are further divided into three genera: Branchiostoma, Epigonichtys and Asymmetron. Whole genome duplication (WGD) occurred specifically in vertebrates. (B). Photograph of a Branchiostoma lanceolatum specimen exhibiting the typical body morphology shared by all cephalochordates. The body is elongated, with pointed extremities hence its name which comes from the Greek “amphi = both” and “oxus = pointed”, and a series of chordate synapomorphies are indicated, such as the dorsal nerve chord and notochord, pharyngeal slits, segmented muscles and gonads, atriopore, caudal fin and post anal tail. Anterior is to the left and dorsal to the top.
Figure 2
A drawing by Comingio Merculiano showing Amphioxus lanceolatus (now known as Branchiostoma lanceolatum).
This drawing of adult amphioxus is based on research done at the Stazione Zoologica Anton Dohrn (SZN) between 1880 and 1890. Some of the amphioxus in the drawing are buried in the sand at the bottom of the sea, which is a relatively rare occurrence. The typical anatomical features of chordates (see Figure 1B) are clearly visible, which is a testament to the accuracy of Merculiano’s drawings.
Image courtesy of Stazione Zoologica Anton Dohrn – Archivio Storico; used with permission (SZN 2022 (L6) Prot. n. 6630). This image is not covered by the CC-BY 4.0 license and further reproduction of this panel would need permission from the copyright holder.
Figure 3
The life cycle of amphioxus includes benthic and pelagic phases.
Adults live at the bottom of the sea during the benthic phase (1); external fertilization takes place in the water column during the breeding season; embryos and larvae then join the planktonic community near the surface during the pelagic phase (2). The length of time spent near the surface depends on the species (and varies from a few weeks to several months). Metamorphosis results in the mouth migrating from the left side of the larvae to a ventral and midline position (juvenile/adults). This is accompanied by a significant change in food intake strategy and a shift from pelagic to benthic behaviour.
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The Natural History of Model Organisms: Amphioxus as a model to study the evolution of development in chordates
eLife 12:e87028.
https://doi.org/10.7554/eLife.87028
