Vol. 53 - Alaska Resources Library and Information Services

Larval Feeding:
Studies with other larval decapods indicate that toxic
oil concentrations may be even lower than those just discussed when
based on assays of single hydrocarbons, exposures longer than 96 hr, or
sensitive sublethal criteria.
Larval lobster (Homarus americanus)
ceased feeding at 0.19 mg/l WSF and had a 30-day LC 50 value of 0.14 mg/l
(Wells and Sprague 1976).
Specific compounds such as naphthalene are
very toxic and caused narcotization followed by death of pandalid shrimp
and of crab larvae at concentrations of 8-12
of less than 24 hr (Sanborn and Malins 1977).
g/l during brief exposures
Chemoreceptive organs of
juvenile and adult Dungeness crab can detect WSF as low as 10[superscript]
-4
mg/l (0.1
g/l), a concentration well within the range of oil spill concentrations
(Pearson et al. 1980).
This may result in behavioral changes affecting
feeding and/or mating and therefore reproduction.
The extent of chemoreceptive
feeding by crab larvae is unknown but could be seriously impaired
by very low oil concentrations, thereby disrupting food consumption
by this rapidly growing stage.
Based on these studies the following generalizations can be made:
1) Larvae are more sensitive to hydrocarbons than are juveniles and
adults (Johnson 1977; Moore and Dwyer 1974).
2) Toxic oil concentrations
range as low as 0.15 mg/l WSF and may be somewhat lower for specific
compounds.
Moore and Dwyer (1974) give a sublethal range of oil WSF
to larvae of 0.001-0.1 mg/l.
Wells and Sprague (1976) suggest a multiplier
of .03 should be applied to LC 5 0 concentrations to establish "safe"
levels, which would predict that acceptable concentrations less than 1 µg/l
WSF.
3) Molting is an extremely sensitive physiological event for
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