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EC number: 203-444-5
CAS number: 106-93-4
all species, the normal response to stimulation was an intense dark
brown coloration (usually occurring immediately after contact) followed
by escape behavior. A similar response usually involving only
chromatophore expansion could often be elicited by tapping the bowl or
by passing a hand above the bowl.
was evident within one minute after the addition of the chemical that
the reduction in the chromatophore expansion following MC or EDB was
paralleled by a loss of locomotor response. To illustrate this
association, we plotted the scores for chromatophore expansion and for
the locomotor response after acute exposure to each of the chemicals
tested. Figures 2 and 3 show this association in O.bimaculoides. Statistical
analysis of the effects of EDB and MC on the chromatophore and locomotor
ratings indicated significant change in each response. The results of
Friedman nonparametric analysis of repeated measures over a 6 hour
period indicated a p<0.001 for each chemical dosage administered for
both measures of toxicity.
loss of locomotor response and the reduction in chromatophore expansion
intensity followed a very similar time course after MC exposure (Fig.
2). Since it was impossible to equate the scale scores for these two
functions, the important comparison was the change from preexposure and
its relationship to time after exposure. These two scales were sensitive
to exposures as low as 0.001 mg/l of MC, with full recovery taking
approximately 5 hours. At the 1.000 mg/l concentration there was 100%
lethality within 3 hours.
exposure to EDB produced a similar combined loss of chromatophore
expansion and loss of locomotor response (Fig. 3). Detectable effects
were observed within 30 minutes at a concentration of 25 rag/l, with
recovery taking a minimum of 6 hours. At higher concentrations, there
was a prolongation of the impaired locomotor response and associated
reduction in chromatophore expansion. After MC or EDB exposure, there
was a concentrationrelated
reduction in both chromatophore expansion and locomotor control followed
by a recovery phase. The rate of recovery after acute exposure was
concentration-sensitive for both chemicals and provided further evidence
of the close relationship of these two measures of motor function.
the recovery phase, the animals often showed a mottled appearance that
suggested increased control of individual chromatophore motor units.
Recovery was complete within 24 hr for both locomotor and chromatophore
established the concentrations required to produce lethality in all
three species (Tables 2 and 3). The lethality data for MC and EDB were
similar over the size range of octopuses. For chronic EDB exposure, O. maya
was the most
sensitive species with respect to lethality (100% lethal at 100 mg/l
within 3 hours). However, all three species demonstrated sensitivity to
the lethal effects of EDB after chronic exposure at concentrations as
low as 25 mg/l. The LC50 for chronic MC exposure occurred in
all three species within 3 hours at 1.000 mg/l. O. bimaculoides and
O. Maya were the most sensitive species to MC, with 100%
lethality at 6 hours of exposure to MC at a concentration of 0.1 mg/l. However,
there was evidence of lethal effects at lower concentrations with longer
exposure time for O. bimaculoides and O. joubini.
advantage of using octopuses for these tests is that the responses are
immediate, highly visible and sensitive. Both responses-chromatophore
expansion and locomotion- are controlled by the central nervous system.
radially-arranged chromatophore muscles contract to pull out the pigment
sac and thus produce color within 2/3 of a second (8). The cell bodies
of the chromatophore motor units lie in the lower motor centers
(chromatophore lobes) of the brain (5); thus they travel without synapse
from the CNS to the skin. Cell bodies of motoneurons of the locomotor
organs---arms, mantle and funnel--are found in peripheral ganglia as
well as lower motor centers of the CNS (22).
control of whole chromatophore patterns and integrated locomotion takes
place in intermediate and higher motor centers of the brain. Therefore,
it is not possible for us to pinpoint the sites of action of MC and EDB.
These chemicals could have a generalized toxic effect on the nervous
system, and may even act solely in the periphery at the neuromuscular
junction. Andrews et al.(1) demonstrated that various
neurotransmitters injected into the blood of Octopus vulgaris produced
a variety of chromatophore and locomotor responses; they reported that
the site of action on chromatophores seemed to be in the lower motor
centers, but that inking and defecation seemed to be controlled from
higher motor centers. Water quality, including magnesium and calcium ion
concentration, was not altered by the addition of EDB or MC. Monitoring
of water quality was performed during the experiment in order to
eliminate such factors from the study. Previously, anesthetic-like
effects have been reported in cephalopods with agents like magnesium
chloride (13) but there was no evidence from the water quality measures
to suggest that this might account for the present results.
is noteworthy that EDB is known to cause toxic effects mainly on the
respiratory system, heart, liver and kidneys (17). In our experiments
withOctopusits most observable effect was on the neurally
controlled chromatophores and locomotion. It was clear from these
studies that the sensitivity of Octopus to MC was greater than to
EDB with respect to effective concentration. Similar differences in
sensitivity to these two chemicals have been found in other animals. It
was also observed that there were not dramatic concentration-dependent
effects after acute EDB exposure. This probably reflects the narrower
dosage range used for EDB compared to MC. Future experiments are planned
to learn the sites of action of MC and EDB in Octopus.
Table 2. Octopus survival after chronic exposure to ethylene
*Values represent the number of octopus alive at each time point.
Table 3. Octopus survival after chronic exposure to mercuric
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