Water Absorption in the Egg Sac of the Salamander Hynobius nigrescens

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Why is it important?

In Hynobius nigrescens, we investigated relationships between days after insemination and changes in mass, inner layer length, and outer and inner layer widths of egg sacs associated with the absorption of water. Egg sac mass, which exhibited a continuous increase irrespective of water temperatures (8 °C or 12 °C) until hatching, was the best parameter for estimating a date of oviposition. We presented a regression equation for this estimation by applying the analysis of analogue and digital data. Using this equation, we can estimate a date of oviposition only by measuring mass of an egg sac deposited in the water during the breeding season.