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 ediilis (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 Homarus amcricanus (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 obsoletiis, and larvae 

 of Crepidula fomicata 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. CuUiney 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. obsoletus to further 

 examine this hypothesis. 



MATERIALS AND METHODS 



Experiments were conducted using the gastropods Nassarius obsoletus, 

 Crepidula fomicata 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 



136 



