Although Chaetognatha sounds like an eldritch horror, it's only scary if you're a plankton! Chaetognaths, or arrow worms, are microscopic predators found throughout the world's oceans. They hunt mainly by ambush, darting forward to hook a number of spines around their prey and swallow it whole. But as scary as they seem to other microscopic prey, arrow worms are themselves an important source of food for larger fish like anchovies, mackerel, and sardines.
(Image: (Left) A close-up of a Sagitta setosa head by Jan van Arkel and Katja Peijnenburg; (Right) A specimin of Pterosagitta draco by Katja Peijnenburg)
he used to write a lot of books, so many books that people started to get concerned for him!
he devoted every minute to his writing, and would only take short breaks to eat and drinkbut he had to stop for a while, as the decades of no sleep finally caught up to him, and he slept for 100 years
a few days ago he woke up and went back to writing. now he's working on his latest novel, a comedy murder mystery called "how you breath on your arms", which is already being adapted into a 30-season TV show
glorpiness rating: at 9:30 we'll travel to that location, 78% approximately
photographs by Chris Isaacs (sacisaacs) on iNaturalist. link to original observation
I made a suggestion thingy on my profile a few months ago. I'm not sure how it looks when my profile is seen by someone else but you can use it to suggest invertebrates for me (I mostly want to post lesser known ones though)
Chaetognaths, whose name means "bristle-jaw," can be found all over world, swimming in brackish estuaries, tropical seas and above the deep dark ocean floor. Also known as arrow worms, the creatures have been around since the Cambrian Period, but their precise place in evolutionary history has long eluded scientists. Now, researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) have learned where arrow worms wiggle on the Tree of Life, and their results could reveal important trends in the evolution of bilateral organisms.
Chaetognaths, whose name means "bristle-jaw," can be found all over world, swimming in brackish estuaries, tropical seas and above the deep dark ocean floor. Also known as arrow worms, the creatures have been around since the Cambrian Period, but their precise place in evolutionary history has long eluded scientists. Now, researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) have learned where arrow worms wiggle on the Tree of Life, and their results could reveal important trends in the evolution of bilateral organisms.
The researchers sought to verify the relationship of the predatory arrow worm to other spiralia—members of a diverse group of organisms, or clade, believed to share a common ancestor. The spiralian clade includes mollusks, segmented worms and flatworms. Strikingly, the scientists found that arrow worms don't belong with spiralians, but instead with a new group of animals that form a sister group to the clade. The results, published January 10, 2019 in Current Biology, challenge the classical view that complex organisms evolved from simple ancestors by gaining new traits over time.
"Arrow worms are predators, they have nervous systems, they have developed sensory organs. But the other organisms they're grouped with are much simpler," said Ferdinand Marlétaz, first author of the study and a postdoctoral scholar in the OIST Molecular Genetics Unit, led by Prof. Daniel Rokhsar. "If you place arrow worms here, it means there was probably a lot of independent simplification, rather than the independent emergence of complexity."
Though very different in appearance, arrow worms and their phylogenetic relatives, such as the microscopic animals known as rotifers, seem to share a unique jaw structure. Composed of dense protein matrix and a fibrous substance called chitin, these jaws are situated near the organisms' mouths and allow them to grasp their prey.
"Arrow worms group with a fairly obscure collection of small marine animals—they're not animals most people are familiar with," said Prof. Daniel Rokhsar, senior author of the study and principal investigator of the research unit. "The fact that these different animals had jaws that were probably related to each other wasn't clear until this paper."
Day 6. Chaetognatha (meaning ‘Bristle Jaw’) Arrow Worms
Again I found this to be a fun drawing, it was also fun to design the dragon especially with that mouth.
The arrow worm design hasn’t differed too much from the original phylum; only really developing the mouth part and tentacles which I think would aid the animal in feeling around (possibly smelling/chemical sensing?) it’s environment.
The dragon is less a chaetognatha and more of a “this is stuff from this organism I like, lets shove it on a dragon”. I imagine this to be a deep see benthic predator.
