Three
(un)usual suspects as the identity of the Shatt-al-Arab's venomous mystery fish
– the Asian stinging catfish (top); the long-tailed moray eel (centre), and the
bull shark (bottom) (public domain)
Yesterday, here
on ShukerNature, I offered a blenny for your thoughts (click here). So today, I'm offering another one! You can
thank me later.
The
Shatt-al-Arab is a 120-mile-long river formed by the confluence of the Tigris and Euphrates rivers in the
southern Iraq town of Al-Qurnah. Flowing
southwards, it constitutes the physical border of Iraq with Iran, and empties
into the Persian Gulf. Many species of fish inhabit its waters,
but one of them may be a notable species still unknown to science.
The
Shatt-al-Arab river (public domain)
I first learnt
of this small but potentially significant unidentified freshwater fish many
years ago, when reading Dangerous To Man (1975), Roger Caras's
definitive book on creatures hostile to humans, but its mystery remains
unsolved to this day. In his book, Caras included the following brief but very
intriguing paragraph:
From Tehran comes a
report of a diminutive black fish found in the Shatt al Arab River. It
reputedly has killed twenty-eight people with a venomous bite. Death is
said to be swift. No other information is presently available. (No other fish
is known to have a venomous bite, and this report is at least suspect.)
What makes the
above snippet so interesting (apart from the fact that except for my own
researches into it and documentation of it in various of my books and articles,
I have never encountered anything more about this creature anywhere) is Caras's
claim that it is its bite that is venomous and that no other fish is known to
have a venomous bite. In contrast, a wide range of piscean species possess
venomous spines, for instance, or toxin-secreting skin.
My
copy of Dangerous To Man by Roger Caras (© Roger Caras; reproduced here
on a strictly non-commercial, Fair Use basis only)
But if we assume
that such a fish does indeed exist, what could it be, and how can its reputedly
venomous nature be explained? Various candidates can be selected from the many
thousands of fish species already known to science, but none can offer a
comprehensively satisfying solution.
When I
originally read Caras's report, the first candidate that came to mind, for
several reasons, was the Asian stinging catfish Heteropneustes [formerly
Saccobranchus] fossilis. This species does indeed inhabit the
Shatt-al-Arab (though it is an imported rather than a native fish here, originating
from Indochina). Moreover, it is often only around 4
in long (though it can grow up to 1
ft), it is definitely black in colour, and, of particular
significance, it is known to be venomous. So far, so good.
Asian
stinging catfish (public domain)
However, unlike
the Shatt-al-Arab mystery fish, the Asian stinging catfish is venomous due not
to a toxic bite but instead to a poison gland at the base of a spine on each of
its two pectoral fins. This can yield an extremely painful but not fatal sting.
Consequently, even if victims (or onlookers) were mistaken in assuming that
this catfish had bitten them (unless perhaps it had done so in self-defence if
they had been molesting it, but this would not have been a source of venom),
they would not have died from its fin spines' sting. Exit H. fossilis
from further consideration.
A second
candidate is the long-tailed or slender giant moray eel Strophidon sathete
(aka Thyrsoidea macrura). Although typically marine, and distributed
widely in the tropical Indo-Pacific Ocean, it is well
known for entering estuaries and travelling considerable distances up rivers,
including the Shatt-al-Arab. What is particularly interesting about this
species in relation to the latter river's mystery fish is that in a sense it
can be said to have a toxic bite, albeit not in the usual convention.
Long-tailed
(slender giant) moray eel (public domain)
True, its teeth
do not actually secrete a toxin, via poison sacs, like those of venomous
reptiles do. However, as a voracious carnivore the long-tailed moray eel will
certainly have pieces of rotting flesh left over from previous meals and packed
with pathogenic bacteria sticking to its teeth, just like crocodiles and
carnivorous mammals like lions and tigers do. Consequently, a bite from this
fish might well transfer some of those bacteria into the wound caused by its
teeth, which in turn may lead to septicaemia developing, especially in someone
with a less than robust immune system, such as a child, an elderly person, or
someone recovering from a major illness. Even so, no known human fatalities
resulting from a bite by this moray eel species are on record, and there is
also the not-inconsiderable problem of size difference to reconcile, because it
can attain a maximum length of up to 12
ft when fully grown (even its average length is over 2
ft). So this species can hardly be deemed 'diminutive', like the
Shatt-al-Arab mystery fish. Don't call us, S. sathete.
Nor can the bull
shark Carcharhinus leucas be termed diminutive, bearing in mind that it averages
7.5 ft long. Unlike
most sharks, this notably aggressive species is frequently found in freshwater
habitats, including the Shatt-al-Arab River, and like those
of moray eels its teeth are brimming with pathogenic bacteria from rotting meat
still attached from earlier meals. So again, a bite from this fish, although
not intrinsically venomous, might well lead to blood poisoning. And several
human deaths caused by this fish attacking them have been confirmed here. But
as even a new-born specimen is normally around 2.5
ft long, this species clearly has no bearing upon the identity of
the Shatt-al-Arab mystery fish.
Bull
shark (public domain)
As I researched
further into this ichthyological puzzle, however, I made an unexpected
breakthrough, by discovering that one crucial aspect of Caras's account was
fundamentally incorrect. Contrary to his statement, some fishes do
possess a genuinely venomous bite.
And one of these
is the blackline fang blenny Meiacanthus nigrolineatus. Its lower jaw
bears sizeable canine teeth that have grooved sides and venom-producing tissue
at their base. These teeth enable it to produce a sufficiently unpleasant bite to
deter all predatory fishes, large and small. In general appearance, it is
relatively nondescript – no more than 3.75
in long, with a blue-grey head and foreparts, and the remainder of
its body pale yellow. There is also a thin black stripe running lengthwise just
beneath its dorsal fin, which earns it its common name.
Blackline
fang blenny (© Akvariumugamyba at http://akvariumugamyba.lt/ - reproduced here
on a strictly non-commercial Fair Use basis only)
Over 830 species
of true blenny or blennioid are currently known to science, generally small in
size and scaleless but many-toothed, and are of worldwide distribution. Most
are marine fishes, as indeed is the blackline fang blenny, which is native to
the Red Sea and the Gulf of Suez and Aqaba.
However, there are freshwater species too (such as the well-known Salaria
fluviatilis, which is native to rivers in several European countries as well
as in Morocco, Algeria, Israel, and Turkey).
No human
fatalities have been recorded with the blackline fang blenny, but what if the Shatt-al-Arab River is harbouring a
still-undescribed, darker-coloured, but otherwise comparable freshwater
relative that is capable of producing a more potent venom? If such a creature, known
locally but attracting little notice from the outside, scientific world, is one
day captured and formally identified, then our mystery fish will surely have
been unmasked at last - turning up like the bad blenny that it is.
My special
thanks to French ichthyologist Dr François de Sarre for very kindly sharing his
own thoughts and comments with me regarding this fishy affair.
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