Egg size and relationship between seawater temperature and egg incubation period of the red frog crab Ranina ranina (Decapoda: Raninidae) reared in the laboratory

T. Ichikawa, K. Hamasaki, K. Hamada-2004

Nippon Suisan Gakkaishi, 70(3): 343-347

Abstract:

This study addresses egg size and the relationship between seawater temperature and egg incubation period of the red frog crab Ranina ranina reared in the laboratory. Major-axis and minor-axis diameters and the volume of eggs increased from ca. 0.66 mm, 0.60 mm and 0.13 mm³ on the day of egg-laying to ca. 0.83 mm, 0.79 mm and 0.27 mm³ on one day before hatching, respectively. The incubation periods (days) of eggs from egg laying, embryonic body appearance and eye-pigmentation appearance to hatching decreased exponentially with increasing temperature. The relationships between mean seawater temperature and the egg incubation periods were analyzed using three non-linear regression models. Consequently, Belehrádek's equation and the equation from heat-summation theory fit the data well. Parameters that show the theoretical value of lower threshold temperature for egg development are ca. 16-18°C and 14-15°C in Belehrádek's equation and heat-summation theory equation, respectively.

(Shibushi Station, National Center for Stock Enhancement (NCSE), Fisheries Research Agency (FRA), Shibushi, Kagoshima 899-7101, Japan)

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