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The Strange Saccorhytus
October 17, 2022
Although its recent offering have been disappointing,
Star Trek was a
cultural phenomenon for many
decades starting with the
original series in 1966. Among its many
plot innovations was the
transporter device that was introduced as a means to eliminate the
expense of always needing to land a
spacecraft on a
planet.
The transporter quickly evolved into a
deus ex machina plot element to beam people to and from
covert and
secluded locations and away from
trouble. One Star Trek
anecdote I remember involves the
design of the
outdoor scenery on
alien planets. One
director, after seeing that the
vegetation seemed too normal, plucked a small
tree out of the
ground, placed it
upside-down with the
root system on top, and explained that alien plants should look more like that.
There's a
fanciful variety of alien
creatures depicted in
science fiction films and
television, but there are many creatures on
Earth which have an alien appearance. The reason for this is that
evolution has
adapted life's form and
function to Earth's many
ecological niches. Examples include the
Remipedia,
colorless and
blind aquatic crustaceans that live in
dark caves, and the
giant tube worms (Riftia pachyptila) that live in the
hydrogen sulfide environment of
deep sea hydrothermal vents. One especially alien creature I first encountered in one of my
childhood Golden Books[1] is the
humpback anglerfish (Melanocetus johnsonii), as shown below.
A female humpback anglerfish (Melanocetus johnsonii).
This fish is a species of the black seadevils. It exists at ocean depths of about a kilometer, at which depth there is very little light. Females of this species are 5-10 times larger than males, and they possess the bulbous bioluminescent lure to attract prey in its low-light environment.
Both males and female have sharp teeth. The largest females are only six inches in length; so, they're not as dangerous as they look.
Wikimedia Commons image by August Brauer (1863–1917) from Ref. 2.[2]
A huge
international team of
palaeontologists,
paleobiologists, and
scientists from other
specialties have just
published an extremely detailed
study on
fossils of an
ancient sea creature, the
Saccorhytus coronarius, a creature as
strange as any imagined alien organism (see figure).[3-4] Team members were from
Chang'an University (Xi'an, China), the
University of Bristol (Bristol, UK), the
Chinese Academy of Sciences (Nanjing, China), the
Chinese Academy of Geological Sciences (Beijing, China), the
Shandong University of Science and Technology (Qingdao, China), the
Freie Universität Berlin (Berlin, Germany), the
Ministry of Natural Resource (Qingdao, China), the
Paul Scherrer Institut (Villigen, Switzerland), and
Virginia Tech (Blacksburg, Virginia). The
preponderance of
Chinese team members is a consequence of the 500
million year old fossils having been found in
China.[3-4]
Saccorhytus coronarius. Left (anterior), middle (side), and right (dorsal) images from the University of Bristol and used with permission. (Click for larger image.)
The Saccorhytus, a
microscopic animal from the
early Cambrian, was thought to have been an early member of the
deuterostomes, which are animals with the
anus forming in the
embryo before the
mouth.[3] This
classification was derived principally because of the low quality of Saccorhytus fossils.[3] This would have placed these animals on the same portion of the
evolutionary family tree as
humans.[4] This new fossil analysis shows that Saccorhytus had a terminal mouth, but no anus, and
spiny armor.[3] Saccorhytus coronarius is now classified as a member of the
Ecdysozoa, such as
insects,
nematodes, and
crustaceans.[3]
Holes around its large mouth were interpreted as
pores for
gills, but this new analysis shows that the holes around the mouth were actually the
bases of spines that
broke away from the fossils.[4] The new fossil
specimens are much more representative. As
Yunhuan Liu, a
professor of
paleobiology at Chang'an University, remarks, "Some of the fossils are so perfectly preserved that they look almost alive... Saccorhytus was a curious beast, with a mouth but no anus, and rings of complex spines around its mouth."[4]
The analysis of the internal and external features of these microscopic fossils was done using a
synchrotron Xray source to take detailed
images.[4] Images at various
angles were processed by a
supercomputer to create a
three-dimensional digital model of the fossils.[4] The digital model showed that the pores around the mouth were actually spines that might have helped the Saccorhytus to capture and process its
prey.[4]
Says
palaeontologist Philip Donoghue,
co-principal investigator of the study and a professor of paleobiology at the University of Bristol,
"We considered lots of alternative groups that Saccorhytus might be related to, including the corals, anemones and jellyfish which also have a mouth but no anus... To resolve the problem our computational analysis compared the anatomy of Saccorhytus with all other living groups of animals, concluding a relationship with the arthropods and their kin, the group to which insects, crabs and roundworms belong."[4]
The final question on every reader's mind is, "How can an animal function without an anus?" The simple answer is that the mouth serves as an intake
orifice for
food, and as an exit orifice for
digestive waste.[4] As
Shuhai Xiao, a professor of
geobiology at Virginia Tech and the other co-principal investigator of the study, remarks,
"This is a really unexpected result because the arthropod group have a through-gut, extending from mouth to anus. Saccorhytus's membership of the group indicates that it has regressed in evolutionary terms, dispensing with the anus its ancestors would have inherited... "We still don’t know the precise position of Saccorhytus within the tree of life but it may reflect the ancestral condition from which all members of this diverse group evolved."[4]
References:
- Bertha Morris Parker, "The Golden Book of Science for Boys and Girls (A Giant Golden Book)," Simon and Schuster, January 1, 1956, 97 pp. (via Amazon).
- August Brauer, "Die Tiefsee-Fische. I. Systematischer Teil," Wissenschaftliche Ergebnisse der Deutschen Tiefsee-Expedition auf dem Dampfer "Valdivia" 1898-1899, 1908.
- Yunhuan Liu, Emily Carlisle, Huaqiao Zhang, Ben Yang, Michael Steiner, Tiequan Shao, Baichuan Duan, Federica Marone, Shuhai Xiao, and Philip C. J. Donoghue, "Saccorhytus is an early ecdysozoan and not the earliest deuterostome," Nature (August 17, 2022), https://doi.org/10.1038/s41586-022-05107-z.
- Scientists relieved to discover ‘curious’ creature with no anus is not earliest human ancestor, Bristol University Press Release, August 17, 2022.
- Supplementary Video no. 2 for ref. 3, Three-dimensional animation showing the general morphology of S. coronarius, Nature Website.
- Tomographic data at the University of Bristol data repository.
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