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Marine Turtle Newsletter 39:8, © 1986

Development of the White Spot on Leatherback Eggs

E. H. Chan
Faculty of Fisheries and Marine Science, Universiti Pertanian Malaysia, Mengabang Telipot, 21030 Kuala Terengganu Malaysia

Early development in freshly laid turtle eggs results in the vitelline membrane rising to the uppermost portion of the egg and adhering to the inner shell membrane. This adherance is marked by the appearance of an opaque chalky spot on the upper surface of the egg shell (Yntema 1964, 1979; Ewert 1979; Blanck and Sawyer 1981). The chalky spot will enlarge to envelope the entire shell surface as development progresses. The first appearance of the white spot has frequently been reported to occur within a day or less after laying (Yntema 1964, 1979; Blanck and Sawyer 1981). Ewert (1979) reported that the white spot will appear in eggs between a few hours to 3 days old. Observations on eggs taken from 4 leatherback clutches laid between 20 and 31 July 1986 and subsequently held in styrofoam boxes at temperatures of 28-29°C revealed that the white spot begins to appear faintly on some of the eggs on the fourth day after laying and by day 5, all fertile eggs would have developed white spots. As the white spot envelopes the entire shell surface (i.e., at about 20 days), the egg becomes turgid. Eggs which have not developed the white spot by day 5 subsequently remained flaccid with a pinkish-beige color. It is interesting to note that the white spot appears much later in leatherback eggs compared to other species. Experiments to determine hatchabilities of eggs handled after the development of the white spot are in progress.

Blanck, C. E. and R. H. Sawyer. 1981. Hatchery practices in relation to early embryology of the loggerhead sea turtle, Caretta caretta (Linné). J. Exp. Mar. Biol. Ecol. 49:163-177.

Ewert, M. A. 1979. The embryo and its egg: development and natural history. pp. 333-416 In M. Harless and H. Morlock (Eds.). Turtles: Perspectives and Research. Wiley Interscience, New York. 695pp.

Yntema, C. L. 1964. Procurement and use of turtle embryos for experimental procedures. Anat. Rec. 149:577-586.

Yntema, C. L. 1979. Temperature levels and periods of sex determination during incubation of eggs of Chelydra serpentina. J. Morph. 159:17-28.