ScienceAsia 30 (2004): 75-80 |doi: 10.2306/scienceasia1513-1874.2004.30.075
Effects of Egg Size
on Fertilization and Embryonic Development of
Sibling Tropical Sea Urchins
Sk. Mustafizur Rahman,* Tsuyoshi Uehara
ABSTRACT: Egg size has the ability to influence fertilization success and embryonic development in freespawning
marine invertebrates. The effects of egg size on fertilization and embryonic development were
compared among three sibling species of Echinometra sp. B, Echinometra sp. C, and Echinometra sp. D.
Gamete size of Echinometra sp. D is larger than Echinometra sp. B and Echinometra sp. C. Larger eggs of
Echinometra sp. D might provide a larger target for sperm and thus, were fertilized at higher rate than smaller
Echinometra sp. B and Echinometra sp. C eggs under moderate and limiting sperm concentrations.
Developmental time from fertilization to prism stage (embryonic development) in Echinometra sp. B and
Echinometra sp. C were comparatively longer than Echinometra sp. D, suggesting that increased allocation of
energy reserve in the cytoplasm in larger Echinometra sp. D eggs reduced the developmental period. As
Echinometra sp. B, Echinometra sp. C and Echinometra sp. D have diverged from their ancestral species, the
differences of the above traits related to egg sizes transcended species differences among them.
Graduate School of Science and Engineering, University of the Ryukyus, 1 Senbaru, Nishihara-cho,
Okinawa 903-0213, Japan.
* Corresponding author, E-mail: email@example.com
Received 10 Sep 2003,
Accepted 17 Nov 2003