My Favorite Animal, Amphioxus: Unparalleled for Studying Early Vertebrate Evolution

Abstract

Amphioxus represents the most basally divergent group in chordates and probably the best extant proxy to the ancestor of all chordates including vertebrates. The amphioxus, or lancelets, are benthic filter feeding marine animals and their interest as a model in research is due to their phylogenetic position and their anatomical and genetic stasis throughout their evolutionary history. From the first works in the 19th century to the present day, enormous progress is made mainly favored by technical development at different levels, from spawning induction and husbandry techniques, through techniques for studies of gene function or of the role of different signalling pathways through embryonic development, to functional genomics techniques. Together, these advances foretell a plethora of interesting developments in the world of research with the amphioxus model. Here, the discovery and development of amphioxus as a superb model organism in evolutionary and evolutionary‐developmental biology are reviewed.

The Ontology of the Amphioxus Anatomy and Life Cycle (AMPHX)

“…Cephalochordates (i.e., amphioxus) are a group of benthic marine filter feeding animals which live buried in the sand of shallow coastal environments in most temperate and tropical seas. Although there are only about thirty species and three genera ( Branchiostoma , Epigonichthys , and Asymmetron ), this chordate subphylum attracts the attention of numerous researchers because of its key phylogenetic position, representing the earliest diverging evolutionary lineage within chordates, and for its extraordinary morphological, anatomical, and genomic conservation with the last common ancestor of all chordates, including vertebrates ( Bertrand and Escriva, 2011 ; Escriva, 2018 ). Some of these conserved morphological characters include a dorsal hollow neural tube and a dorsal notochord, pharyngeal slits, segmented muscles, and gonads as well as organs homologous to those of vertebrates, such as the pronephric kidney or an endostyle.…”

JNK Mediates Differentiation, Cell Polarity and Apoptosis During Amphioxus Development by Regulating Actin Cytoskeleton Dynamics and ERK Signalling

“…They share many fundamental developmental processes with vertebrates, including regulative development, neurulation, and somitogenesis, as well as key chordate characters such as a notochord, hollow nerve cord, post-anal tail, and the endostyle, a thyroid hormone producing organ (Bertrand and Escrivà, 2011). However, broadly speaking, lancelet genomes are much simpler, with often single orthologues of genes found in multiple copies in vertebrates, which have arisen due to the whole genome duplications in this lineage (Escrivà, 2018). They also lack the complex acquired immune systems and behaviours characteristic of many model systems (Yuan et al, 2014).…”

A Potential Method for Rapid Screening of Amphioxus Founder Harboring Germline Mutation and Transgene

“…However, current methods used for identifying valid founder amphioxus (F0) carrying desired mutations or transgene are time-consuming ( Holland and Li, 2021 ) since they rely on animal spawning that normally takes at least 3 months (from their births) for B . floridae or more for other amphioxus species ( Zhang et al, 2007 ; Escriva, 2018 ). Moreover, to ensure success, especially for transgene and mutation sites of low efficacy, more than several dozen F0 animals need to be raised.…”

“…These advances have greatly accelerated the rate of establishing amphioxus as a model organism, and enables researchers to robustly dissect the function of amphioxus genes (Hu et al, 2017;Li et al, 2017;Ren et al, 2020;Zhong et al, 2020;Zhu et al, 2020). However, current methods used for identifying valid founder amphioxus (F0) carrying desired mutations or transgene are time-consuming (Holland and Li, 2021) since they rely on animal spawning that normally takes at least 3 months (from their births) for B. floridae or more for other amphioxus species (Zhang et al, 2007;Escriva, 2018). Moreover, to ensure success, especially for transgene and mutation sites of low efficacy, more than several dozen F0 animals need to be raised.…”