No, I was more concerned with his failure to standardize venom
concentration, failure to identify the actual toxic component, failure to
identify the physical mecahnism by which venom is transferred from the
axillary glands (under the skin of the body, immediately below the
posthumeral process) to the integuementary sheath (the fleshy covering on
the spine). He also attributes the development of this apparatus to strong
predation pressures, which he can't support without a phylogeny. Mammals may
be much different in their response and suceptability to this compound than
Gambusia, so any extrapolation needs to be taken with a grain of salt.
That aside, there's some interesting stuff here. BG, he did include Arius
felis, which ranked in the "more virulent" group. Arius is in a different
family than the other NA catfishes (the Ariidae), so at least two families
appear to have a venomous compound.
Birkhead suggests that the integuementary sheath is actually the source of
venom in ictalurids (rather than the axillary gland), which would make
sense. There aren't any ducts connecting the axillary gland to the spine.
This sheath is torn on impact, and ruptured glandular cells in the epidermis
would release toxic compounds directly into the wound.
Nelson's 'Fishes of the World' (1984) suggests that "Heteropneustes fossilis
of India, which has a painful and potentially dangerous sting, have an
aggressive behavior with records of attacks on humans and other fishes," (!)
and that "stings from Plotosus lineatus" may result in death."
Heteropneustes is the sole genus in the Heteropneustidae, and Plotosus is in
the family Plotosidae.
Any biochemists out there willing to have a go at isolating the venom
compounds? Noone's done it yet... and on the off chance that humans could
be allergic to the venom (as in bees), NIH might be willing to fund such a
study in the interest of "public safety".
Alternatively, we could maybe setup a booth at NANFA2000, jab a bunch of
NANFA volunteers with various madtom spp, and then monitor their
reactions... ;)
Cheers,
Dave
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