In this video we are going to see the history of amphioxus in science
from the first description by zoologists to the use of amphioxus as a model system
in the lab to tackle evo-devo questions.
Amphioxus are small, worm-like animals that resemble a fish without a head.
They live in sand in shallow waters in temperate and tropical areas
from 1-50 meters deep.
The first description of amphioxus, which is the common name
of the Cephalochordate clade, also called lancelets, came from a Chinese legend.
In this legend, Wencheng, the literature God, would escape his enemies
on the back of a crocodile. And when the crocodile died
in the Bay of Xiamen, lava came out from his body
and it resulted to be amphioxus.
And since then, the Chinese call it the fish of the God of Literature.
These animals are consumed as food, although the population of amphioxus
has greatly decreased in China. In the Philippines as well,
where they call it banusok, they are used for human consumption.
In 1774, the zoologist and botanist Peter Simon Pallas
scientifically described amphioxus for the first time
and named this animal Limax Lanceolatus.
He could only observe two fixed adult specimens from the Cornwall coast
and he classified amphioxus as a mollusk.
In 1834, Gabriele Costa, a zoologist in
and he recognised it could represent the
and vertebrates. Costa observed living animals and he described
the oral cirri around the mouth as gills.
This is why he named the genus Branchiostoma
from the Greek words for "gills" and "mouth".
in 1828, William Yarrel, who was unfamiliar with Costa's work
proposed Lancelet as a common name, and they changed the name of the genus
from Limax to Amphioxus, and later on it became Branchiostoma.
However, Yarell is the origin of the two common names of our favourite animal
Amphioxus and Lanclet. Later, many zoologists became interested in amphioxus
and made descriptions of its morphology.
However, they were all working with adult specimens.
The first researcher that described amphioxus embryos was the
Russian embryologist, Alexander Kowalevsky.
After his studies, he came to Naples in 1863 to try to obtain embryos from animals
of the Bay of Naples. Kowalevsky frequently collected amphioxus
and kept them in his own aquarium in the hope of them spawning.
The animals had large gonads since December 1863
and finally they spawned for Kowalevsky in May 1864.
So he had the opportunity for the first time to study amphioxus embryonic development.
He recognised that the early embryogenesis
while after gastrulation it resembled that of vertebrates
with the formation of a notochord, which is a chordate synapomorphy.
Kowalevsky tried to raise the amphioxus larvae to the adult stage,
but he failed.
However, he was able to collect and study planktonic larvae.
Many other 19th-century zoologists became interested in amphioxus,
among them the German naturalist Ernest Haeckel, who wrote in The Evolution of Man:
He liked amphioxus so much, they feature on the menu for his 60th birthday dinner.
Like Heckel, many others zoologists were interested in studying amphioxus
for its morphological and developmental characteristics
that are similar to vertebrates, but simpler. Amphioxus was believed to
represent the transition between invertebrates and vertebrates.
However, as you know, amphioxus cannot be
at the root of vertebrates because they are extant animals,
but they are evolutionarily closely related to them.
This is one of the reasons why many researchers use amphioxus
as an animal model system.
Let's go back to the story.
At the beginning of the 20th century, the research on amphioxus slowed down
until two American researchers Dr. Linda Holland and professor Nick Holland
decided to work on amphioxus embryonic development.
In 1986-87 Linda and Nick decided to spend a sabbatical year in France
working at the marine station of Villefranche-sur-Mer
that together with the stations of Banyuls-sur-Mer and Roscoff
are part of Sorbonne University in Paris.
At that time, Linda was working on pelagic tunicate development
and Nick on crinoids.
Nick spent many hours in the library of
collection of 19th century material on the
He became more and more interested in the question on the origin of the vertebrates.
However, he thought crinoids were not the best model to tackle this question,
and therefore he started to study amphioxus together with Linda, who was also interested
in this topic. So they started to collect amphioxus in Tampa, FL during the summer
1988. They were able to obtain embryos, and in collaboration with
professor Peter Holland at the University of Oxford, they developed a protocol
to analyse embryonic gene expression through in situ hybridization experiments.
Ultimately, amphioxus entered the molecular biology era, and
in 2014, Linda and Nick
were awarded the Kowalevsky Medal from the Saint Petersburg Society of Naturalists.
This award was for extraordinary achievement in evolutionary developmental biology
and comparative zoology. In this video
we have seen that amphioxus is an animal that fascinated many biologists
for a long time for its morphological and developmental characteristics.
We have also seen how the classification of an animal can be hampered by the access
to biological material and communication among scientists.
In the next chapters, we will see more in detail the biology of amphioxus
and how it is used today as a model in the lab for evo-devo studies.