1.
The only other extant member of the ancient family
Cryptobranchidae (to which both of the above species
belong) is the North American Hellbender
(Cryptobranchus alleganiensis); a much smaller but
otherwise similar species which is also encumbered by a
number of other unflattering names such as the ‘Water
Dog’, ‘Snot Otter’, ‘Grampus’ and the strangely apt
‘Lasagna Lizard’. Adult Hellbenders may grow to over 70
centimetres in length, with a weight of 2.5 kilograms.
Again dependent on cutaneous respiration (with a surface
area considerably increased by dorsoventral skin folds),
they are confined to cool, shallow, fast-flowing streams in
the eastern states of the US and are highly territorial. Most
populations have exhibited dramatic declines in recent
years, with habitat loss, collection for the pet trade and the
chytrid fungus being significant causal factors, and the
species is considered to be ‘near threatened’, with the
Ozark subspecies (C. a. bishopi) listed as endangered.
2.
Cryptobranchids exhibit incomplete metamorphosis; the
young possess external gills, which atrophy as they
develop extensive skin folds along the flanks. There may
be ontogenetic colour changes as well, however many
other larval traits are retained in conjunction with a fully-
aquatic lifestyle, such as paddle-shaped tails, gill slits,
small eyes lacking eyelids and sensory apparatus to detect
prey in the water.
In contrast, adult members of the genus Necturus, which
consists of a handful of species (the taxonomy remains in
dispute) also native to the eastern US, retain external gills.
Also referred to as water dogs, as well as ‘mudpuppies’,
these creatures again typically inhabit rocky streams. The
Common Mudpuppy (N. maculosus) is sympatric with the
Hellbender in some locations, but is easily distinguished
by the lack of dorsoventral skin folds, the presence of
external gills, and the fact that it possesses four toes on