MARINE TOXINS AND VENOMOUS AND POISONOUS MARINE ANIMALS
271
that the effect of the poison is greater on reflex transmission than
on the nerve, and that these changes occur, for the most part, independently of the changes in the cardiovascular system.
M. H. Evans (personal communication, 1965) has found that the
toxin has no specific effect on the neuromuscular junction in frog
and mammalian limb muscles. I n mammals, nerve conduction and
muscle contraction were almost equally sensitive to the toxin. C. Y.
Kao (personal communication, 1965) states that in the frog sartorius
muscle, 0.1 pg/ml of smitoxin first increases the threshold for spike
generation but subsequently blocks spikes. He feels that the toxin
interferes with sodium conductance without altering potassium or
chloride conductances.
Parnas (1963) notes that when the toxin of Prymnesium parvum is
injected into mice or frogs it too produces respiratory paralysis.
He suggested that this was provoked through the action on the central
nervous system at the synaptic level. The toxin did not affect skeletal
muscle but did inactivate the motor end plates. It caused smooth
muscle to contract (Parnas suggests that this might occur through
the release of acetylcholine); subsequently, it inhibited both this
contraction and the response to acetylcholine, histamine, serotonin,
bradykinin, nicotine and barium chloride. In a personal letter (1964),
he states that the toxin acts as a non-depolarizing blocking agent at
the post-synaptic membrane of the neuromuscular junction. Intracellular recordings from the frog’s heart indicate that the toxin causes
depolarization.
111. PORIFERA
Of the 5000 or so species of sponges, only a few tropical and subtropical forms are known to be dangerous to man. Our knowledge of
the toxicity of these highly organized colonies of unicellular monads
to other animals is very meager. Some sponges have been implicated
in the food-chain relationship of icthyotoxism but the evidence so
far presented is very circumstantial.
A. Poisoning
Some Porifera are known to eject substances which are toxic to
certain of the animals in their environment. De Laubenfels (1932)
states that when Tedania toximlis de Laubenfels is placed in a bucket
with fishes, crabs, molluscs and worms, in an hour or perhaps less,
these animals will be found dead. The toxin appears to be located in
the gemmules. The stimuli for the discharge of the toxin and the
mechanism by which these animals release their poison are not known.
271
that the effect of the poison is greater on reflex transmission than
on the nerve, and that these changes occur, for the most part, independently of the changes in the cardiovascular system.
M. H. Evans (personal communication, 1965) has found that the
toxin has no specific effect on the neuromuscular junction in frog
and mammalian limb muscles. I n mammals, nerve conduction and
muscle contraction were almost equally sensitive to the toxin. C. Y.
Kao (personal communication, 1965) states that in the frog sartorius
muscle, 0.1 pg/ml of smitoxin first increases the threshold for spike
generation but subsequently blocks spikes. He feels that the toxin
interferes with sodium conductance without altering potassium or
chloride conductances.
Parnas (1963) notes that when the toxin of Prymnesium parvum is
injected into mice or frogs it too produces respiratory paralysis.
He suggested that this was provoked through the action on the central
nervous system at the synaptic level. The toxin did not affect skeletal
muscle but did inactivate the motor end plates. It caused smooth
muscle to contract (Parnas suggests that this might occur through
the release of acetylcholine); subsequently, it inhibited both this
contraction and the response to acetylcholine, histamine, serotonin,
bradykinin, nicotine and barium chloride. In a personal letter (1964),
he states that the toxin acts as a non-depolarizing blocking agent at
the post-synaptic membrane of the neuromuscular junction. Intracellular recordings from the frog’s heart indicate that the toxin causes
depolarization.
111. PORIFERA
Of the 5000 or so species of sponges, only a few tropical and subtropical forms are known to be dangerous to man. Our knowledge of
the toxicity of these highly organized colonies of unicellular monads
to other animals is very meager. Some sponges have been implicated
in the food-chain relationship of icthyotoxism but the evidence so
far presented is very circumstantial.
A. Poisoning
Some Porifera are known to eject substances which are toxic to
certain of the animals in their environment. De Laubenfels (1932)
states that when Tedania toximlis de Laubenfels is placed in a bucket
with fishes, crabs, molluscs and worms, in an hour or perhaps less,
these animals will be found dead. The toxin appears to be located in
the gemmules. The stimuli for the discharge of the toxin and the
mechanism by which these animals release their poison are not known.