Abstract:

We exposed embryonated eggs from blue crab, Callinectes sapidus, to crude oil and to uncontaminated water and measured embryonic development daily after exposure and recorded whether or not eggs hatched into a normal zoea.

Suggested Citation:

Kelsie Kelly. 2017. Effects of crude oil on embryonic development and early instars in Callinectes sapidus. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7JW8BZ2

Purpose:

Experiment to test the effects of crude oil exposure on the development of blue crab embryos.

Data Parameters and Units:

date (date plate was removed from incubator and data collected MM/DD/YYYY) replicate (1-7 indicates from which female they were taken) day (Cont = control, Ex = experimental and number indicate day) stage (the stage of the embryo determined by morphological features described in DeVries (1983)) cloudy/dark (living embryos were observed to have clear eggs with yellow yolk. Embryos in cloudy eggs with dark yolk that ranged in color from dark yellow to orange were considered deceased. If the column is blank the egg was observed to be clear with a yellow yolk) heart beat (heartbeat was visually assessed and generally occurred after stage 9) dorsal spine (Dorsal spine morphology was evaluated in hatched larvae. In zoea the dorsal spine is typically long and erect with backward arch. In prezoea the dorsal spine was either not visible due to persistent invagination or it was visibly shorter than the dorsal spine of a typical zoea. This characteristic is noted as SHORT. Occasionally these short dorsal spines would be arched forward. This characteristic is noted as FORWARD) eyes full & bilaterally symmetrical (The eyes of embryos below stage 6 are classified as NOT PRESENT indicating that they had not yet reached this developmental milestone. The eyes of embryos at stage 6 or later were evaluated on the basis of being bilaterally symmetrical and fully pigmented. If eyes met this criteria they were classified as Y for yes. If they did not meet the criteria they were classified as either BROKEN UP indicating that the eyes were missing patches of pigmentation or UNDERTEMINED. UNDETERMINED was used to describe the eyes of embryos that were either decayed past an identifiable stage or when the egg had become ruptured) rostrum (the presence or absence of a rostrum was visually assessed in hatched larvae and noted as Y for present and N for absent) telson (the telson was visually assessed in hatched larvae for abnormalities and noted Y for normal and N for abnormal) swimming ability (swimming ability was assessed in hatched larvae and noted as NORMAL if the larvae was able to swim in the typical rapid fashion of a zoea or IMPAIRED if the swimming was abnormal) lateral spines (lateral spines were visually assessed in hatched larvae for abnormalities and noted as Y for present and normal or N for absent with additional notes documenting abnormalities)

Methods:

Water accommodated fractions (WAF) were prepared daily (as described by Singer M, Aurand D, Bragin G, Clark J. R, Coelho G. M, Sowby M. L, Tjeerdema R. S. 2000. Standardization of the preparation and quantitation of water-accommodated fractions of petroleum for toxicity testing. Marine Pollution Bulletin 40: 1007–1016) for both oilexposed and non oil-exposed (control) eggs. The WAF for the oil-exposed eggs was made with an oil concentration of 500 ppb. Eggs were transferred individually into 48 wells of a 96-well plate with 1 mL of seawater with a salinity of 28 ppt. The eggs were then incubated for approximately 12 hours and experimental trials commenced the following day. The majority of embryonated eggs in an egg mass, and therefore in each replicate of the experiment, were at the same developmental stage. Eggs that were at the same stage as the majority in the egg mass for each experiment and were normal, were selected for treatment. One μL of WAF was added to each well of the oil-exposed group, and clean seawater was added to control wells. Full water changes were performed daily for both treatments with WAF re-added to oil-exposed wells. Oil exposure was continuous for the duration of the experiment. Eggs were incubated at 28°C in the dark until they hatched. One well plate from the control and oil-exposed group was examined daily under a microscope.

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