KIDDER, GW*; BALDWIN, J; GOLDSMITH, C; PETERSEN, CW; PRESTON, RL; Mt. Desert Isl. Biol. Lab.; Illinois St. Univ.; Illinois St. Univ.; College of the Atlantic; Illinois St. Univ.: Aerial development in Fundulus heteroclitus embryos
Spawning of Fundulus heteroclitus macrolepidotus (the northern subspecies) often occurs at spring high tides; embryos mature in moist air in about two weeks. We stripped oocytes and sperm from wild caught fish into 10� artificial seawater (ASW) and placed them on moist filter paper in a petri plate at 20oC over 10� ASW, where they developed as described by Armstrong and Child (Biol. Bull. 128:143, 1965). Even when crowded to the point of touching, they achieved nearly 100% hatching success. Development typically slowed near stage 35, and eggs synchronously hatched when triggered by flooding. Since O2 diffusion through water may produce hypoxia in submerged embryos, we placed 70 fertilized eggs in 35 mm wells in moist air, under 2 mm of 10� ASW, and under 17 mm of 10� ASW, with 10 replicates for each condition. After day 14, all plates were flooded daily with 10� ASW to test for hatching. Fry were measured with an occular micrometer upon hatching. Compared to either submerged condition, aerial incubation produced a higher hatch rate, earlier hatching, and larger fry. Aerial hatchlings averaged 5.87 � 0.03 mm in length (N = 99), shallow submersion 5.66 � 0.04 mm (N = 89) while deep submersion hatchlings averaged 5.32 � 0.18 mm (N = 42), all of which are significantly (P<0.01) different from each other. Using flow-through respirometry, O2 uptake under aerial conditions increased approximately linearly from 10 to 240 ml�kg-1�hr-1 over 10 days, declining thereafter until hatching was triggered at 14 days. The smaller fry from submerged embryos may result from less efficient anaerobic metabolism, assuming that stored nutrients were constant among eggs. The success of aerial incubation under laboratory conditions allows rearing of large numbers of synchronized fry for experimental uses. (NSF CRUI 0111860)
