invertebrate reproduction, such as sperm motility and fertilization success (22, 
25), and embryonic cleavage rates (1, 22). Reduced egg production has been 
reported for oil-exposed Mytilus edulis (7) and Eurytemora affinis (5), and 
development of some larval Crustacea (16, 32, 33) and bivalves (9, 24, 25) is 
delayed after exposure to sublethal oil concentrations. Oil-induced changes in 
larval behavior of Homams americanus (32) and Cancer irroratus (6) have also 
been demonstrated. Recently, Anderson et al (3) have reported effects of low 
hydrocarbon levels on hatchability of fish embryos, and on heart beat rate of 
larval fish. 
The general objective of this investigation was to elucidate some sublethal 
effects of No. 2 fuel oil (introduced as the water accommodated fraction, 
WAF) on aspects of the reproductive and developmental biology of several 
common coastal invertebrates. Specific topics studied include egg capsule 
deposition, fecundity, hatchability and larval growth rates. The lethal dose of 
the oil was also determined for adult and larval Nassarius obsoletns, and larvae 
of Crepidula fornicata and Cancer irroratus , in order to establish sublethal 
exposure levels. 
A review by Moore and Dwyer (21) suggest that larval organisms are more 
sensitive to hydrocarbon toxicity than are adults, yet tolerance data on adults 
and larvae of the same species are infrequently reported. Culliney et al (12) 
suggest that the high surface/volume ratio in larvae and their “obligatory 
exposure to whatever may be in the water” would make larvae particularly 
susceptible to toxic substances, such as oil, at very low concentrations. Our 
study includes work on both adults and larvae of N. obsoletns, to further 
examine this hypothesis. 
MATERIALS AND METHODS 
Experiments were conducted using the gastropods Nassarius obsoletus, 
Crepidula fornicata and Urosalpinx cinerea , and the crustacean Cancer 
irroratus. Adults were exposed to oil using the flow-through oil-dosing system 
described by Hyland et al (15). Briefly, unfiltered seawater and No. 2 fuel oil 
enter a mixing chamber. The WAF produced is then metered into exposure 
tanks where it is diluted to the desired concentration by controlled flow of 
untreated seawater. Total hydrocarbon concentrations in control (for 
background) and experimental tanks are monitored three times/week by 
infrared spectrophotometry, and flow rates are adjusted to maintain desired 
WAF exposure levels. Nominal total hydrocarbon concentrations (WAF) were: 
0.0 ppm (control), 0.01 ppm, 0.1 ppm, and 1.0 ppm. Because measured 
hydrocarbon concentrations varied with time in the flow-through system, the 
nominal concentrations (cited as “X” ppm in the text) indicate only the order 
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