Obligatory disclaimer: real life sucks, but we're going to talk about a RL animal altogether, since Marvel and co. are lying low for the rest of May. Therefore, where are we?
Let us talk about the cryptobranchid, or the
giant, salamanders of Asia and North America, simply because they are in their
own suborder. Pause
There are three suborders of the tailed amphibians,
aka newts and salamanders, and the overwhelming majority of them belong to the
Salamandroidea suborder; the only exceptions are the sirens of the south-east
North America, (USA), and the aforementioned giant salamanders and their
relatives, (more on them below).
The sirens’ differences from the rest of the
salamanders are obvious: they are probably the most neotenic of all the tailed
amphibians: not only they have external gills, but they also have only front
legs – no hind ones. Pause.
Whereas in frogs and toads it is the hind legs that
develop first, in newts and salamanders it is the front ones instead; plus,
their tadpoles have external gills, while the frogs and toads acquire internal
ones very quickly; the legless caecilians, the final group of the modern amphibians,
also seem to have external gills, but they are much less known than the other
two, so they will be mentioned only in passing – wait.
Getting back into the mists of time, the thing is that
the modern amphibians only began to appear around the time of the K-T
extinction 66 MYA; before then, especially during the Palaeozoic and the early
Mesozoic, completely different groups of amphibians ruled. The thing is that
while initially paleontologists went with a linear P.O.V. and proclaimed that
amphibians evolved from the fish, and reptiles – from the amphibians, by now it
is clear that these statements are much vaguer than scientists have initially
imagined.
Yes, the initial land vertebrates have evolved from
fish, (as there were not any other vertebrates), but these days scientists tend
to classify those early semi-terrestrial semi-aquatic animals as ‘tetropods’
and prefer to differentiate them from the amphibians because of reasons. Ditto,
right now the actual ancestors of the reptiles is unknown; the reptiles have
appeared back in the Carboniferous, (as shown in ‘Walking with Monsters’, for
example), though they were small at that time – about the size of the modern
lizards on average, (but, again, they weren’t really related to the modern
lizards and snakes at all); yet they were already differentiated from the
amphibians. However…
However, for a while, in the late Paleozoic, there
were the so-called reptilomorph amphibians – amphibians that had reptile-like
traits in adults, but their young still had gills and lived in water… and why should
not they? The amphibious way of life – when the young and the adults of the same
species have different… everything and thus do not compete with each other – is
clearly advantageous, as the amphibians’ evolutionary history, from the
Devonian to Recent demonstrates; however…
However, somewhere along the line, things have
diverged at least for some tailed amphibians, as they evolved neoteny, a
condition where juvenile traits persist into sexual maturity. Actually, neoteny
is present in several groups of animals, including insects, so let us for now
focus on the tailed amphibians: for them, neoteny is when a species has both
sexual maturity and external gills, (with the sirens going one-step further, as
we already said). However, the giant salamanders are a different story.
Why? Because while they are mostly aquatic, (as the
neotenic amphibians are), their adults lack external gills. Yes, their young
hatch underwater, have external gills, eventually grow legs…but unlike the
axolotl and the mudpuppies, their gills disappear with sexual maturity;
instead, they grow skin folds and the like to extract oxygen from the water
instead, which is a different story altogether – but what it is?
To recapitulate, metamorphosis came before neoteny –
for a while, there was no obvious reason to evolve the latter, but when it did…
either the giant salamanders were too late, apparently, as plenty of other
salamander groups and subgroups had, and so the giant salamanders couldn’t ‘fit
in’… other the giant salamanders were too early: they began to stick to a
mostly fully aquatic lifecycle before the other salamanders evolved neoteny,
and since there was no competition, they flat-out didn’t evolve it, as there
was no need for it. What next?
While throughout Earth’s history there were plenty of
giant salamander subgroups, right now, there are only three species around –
one in North America, and the other two in Asia. The American hellbender is the
smallest of the three – no bigger than 70 cm long, about the size of a small
child at best… but the bigger species of North American mudpuppies don’t grow
over 48-50 cm long, so, obviously there’s some other factor at work, since the Japanese
giant salamander reaches 150 cm in length – the size of a small adult – and the Chinese species – reaches
180 cm, which is the size of an average
adult instead. Pause.
Let us get into the ecology of the giant salamanders
instead. While they might be vaguely associated with the crocodiles, they
really are not. The crocodilians divide, among other ways, into two broad
categories: narrow-snouted fish-eaters and broad-snouted ambush-hunters of land
animals. By contrast, the giant salamanders live most of their life underwater,
and they do not ambush land animals, yet their heads and snouts are shore and
broad instead. Therefore, whom do they resemble instead?
Why, the catfish, and especially the wels catfish –
one of the biggest freshwater catfish species of them all. Just as the giant salamanders,
the wels catfish is active mainly at night; it hunts by swimming along the
river bottom, sensing the prey with its whiskers and swallowing them whole. The
giant salamanders’ don’t have such as advanced whiskers as the wels catfish does,
but neither does the burbot, (another fish), and it does the same thing too,
but being around 1 m 24 cm in length, (in the size range of the giant
salamanders, cough), it just cannot compete with the wels catfish size-wise.
Where are we?
Ah yes, entertaining my theory that the giant
salamanders, (also known as the ‘primitive salamanders’ in some nomenclature,
while the other, non-siren salamanders, are known as the ‘advanced salamanders’
instead), are the ecological analogues of the wels catfish instead. The hellbender
lives in the Eastern United States, where there is not any natural analogue of
the wels, and, again, it is the smallest living member of the cryptobranchids. The
Japanese giant salamander lives alongside the Biwa catfish – a wels catfish
variant… which is endemic to a single lake only, and the Amur catfish, which is
around the size of a large burbot instead, so the Japanese giant salamander can
handle it.
As for the Chinese salamander, this is where things
get murky. These days, there are actually two species of this amphibian: the
Chinese salamander proper, and the South China giant salamander; both species
are critically endangered, (i.e., in a much worse state than their Japanese and
U.S. cousins), and there may be more species of the giant salamander living
there – they just have not been identified and confirmed by the scientists yet.
Still, the Chinese giant salamander species’ complex is struggling – from habitat
destruction, water pollution, harassment from humans, hybridization with the Japanese
giant salamander…and maybe from the competition from the introduced wels
catfish? Who knows!
One last thing. The kappa. In one of the RM episodes,
our main man JW went to Japan to confront the Biwa catfish and the Japanese
giant salamander, which he proclaimed to be the root behind the kappa legend.
With all due respect, JW, but on this occasion you’re a flat-out wrong; the
kappa was never depicted as even vaguely salamander-like, but as a turtle-like
humanoid instead. Therefore, that is that.
For the moment, though, we are saying good-bye to the
giant salamanders. See you all soon!