Understanding 'smart,' spitting archerfishes

Date:
April 11, 2022
Source:
University of Kansas
Summary:
A new article thoroughly examines the evolutionary history and
anatomical variation of archerfishes.



FULL STORY ========================================================================== Archerfishes are the anti-aircraft gunners of the aquatic world. The
fishes are famed for their amazing ability to shoot down land-based
insects midflight with highly accurate streams of water they project
from their mouths.


==========================================================================
Yet, scientifically speaking, not enough really has been known about archerfish: What makes an archerfish? How many species are there? What
other fishes are closely related? What fishes did they descend from? Now,
a new paper appearing in the peer-reviewed journal Integrative Organismal Biology from researchers at the University of Kansas Biodiversity
Institute and Natural History Museum is the most thorough examination
ever produced of the evolutionary history and anatomical variation of archerfishes, which are also known by the scientific name Toxotidae.

"Archerfishes are a small group of fishes that predominantly live in
Southeast Asia and Australia and a lot of the regions in between," said
lead author Matthew Girard, a research affiliate with the KU Biodiversity Institute and Natural History Museum and a postdoctoral fellow in the
Division of Fishes at the Smithsonian Institution's National Museum of
Natural History. "Sometimes people think of archerfishes as a famous
group because they can spit water out of their mouths, and they are
often studied just because they're pretty smart animals -- they have to calculate for refraction, and they're able to hit things that are on the
wing as they're flying overhead." Despite archerfishes' renown among ichthyologists and aquarium enthusiasts, until now not much scholarly
work has been performed on them.

"That's really where our study comes in," Girard said. "We looked at
how these fishes are related and asked, 'How did this amazing mechanism
of allowing them to actually be able to spit come to evolve?' We had
some ideas of what other kinds of fishes they were related to, but for
the first time we've generated a hypothesis of how all these species of archerfish are related to each other. We didn't even really know if all
of them could shoot. The studies that have looked at how they're shooting
or how smart they are, they're generally using archerfish that are found
in the aquarium trade -- but there's some rare ones out there, too. So,
we were not only answering questions about how they're related and how
this shooting mechanism evolved, but can all of them even shoot in the
first place, or is there variation in there? We did find that they all can shoot; they all at least have the structures in their mouth to be able
to shoot, but there are differences among them." For the first time,
the paper establishes an authoritative family tree of archerfishes,
allowing researchers to trace through genetics and morphology how the
spitting specialization may have evolved over time.



========================================================================== "There are other fish that eat insects and some that will jump out of
water, but I would say there's nothing really like this," said co-author
Leo Smith, associate curator at KU's Biodiversity Institute and Natural
History Museum.

"There's a potentially apocryphal story, which is that back in the
mid-1800s in India, archerfishes would shoot out the colonizers'
cigarettes, just like if there was like a lightning bug. They would
shoot them out and drive people crazy and that's how the Western
Europeans discovered the thing that was already there, that everybody
there already knew about -- but there are stories that they will
spit out cigarettes." Girard sought tissue samples and specimens of archerfishes from institutions and natural history museums around the
world -- unheralded, often grueling work -- and then analyzed their
structures and genetics to better understand the group.

For instance, Girard, Smith and their co-authors found the oral structures
of archerfishes support a blowpipe-mechanism hypothesis, but soft-tissue
oral structures may also play a role in shooting.

"Just because other fish can move water, it's not anything like
this," Smith said. "I equate it to, 'I could put a trumpet in my
mouth, and I suppose I could make noise come out of it, but not like
Miles Davis.' It's like a fundamentally different thing, too, a really remarkable specialization for catching insects." Further, the research
team determined archerfishes have a closely related "sister group"
of fishes, called beach salmon -- and found they, too, had "relevant
shooting features in the oral cavity," suggesting shooting water at prey
could be what evolutionary biologists dub a co-opted or exapted trait.

"We think of adaptations like, for example, a sailfish that has this
really beautiful sail on their dorsal fin -- but a lot of fishes have
dorsal fins and what they've done is kind of modify that dorsal fin to
fit some other need," Girard said. "If we look at the group that's most
closely related to archerfish, it's already eating hard-body things. So, archerfish must have had all the structures that would allow that to
happen, and all they had to do was kind of modify those to be able to
shoot. So that's what that co-option is - - it's really a nuance saying
that the necessary parts were already there and all they did was modify
a few things to allow this to happen." Girard and Smith's co-authors
on the new paper are M.P. Davis of St. Cloud State University; H.H. Tan
of the National University of Singapore; D.J. Wedd of Charles Darwin University; P. Chakrabarty of Louisiana State University; W.B. Ludt of
the Natural History Museum of Los Angeles County; and A.P. Summers of
the University of Washington's Friday Harbor Laboratories.


========================================================================== Story Source: Materials provided by University_of_Kansas. Note: Content
may be edited for style and length.


========================================================================== Related Multimedia:
* Spitting_archerfish_bones ========================================================================== Journal Reference:
1. M G Girard, M P Davis, H H Tan, D J Wedd, P Chakrabarty, W B Ludt,
A P
Summers, W L Smith. Phylogenetics of archerfishes (Toxotidae)
and evolution of the toxotid shooting apparatus. Integrative
Organismal Biology, 2022; DOI: 10.1093/iob/obac013 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220411113739.htm

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