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Title: Timing and Synchronization of the Breeding Period in Pilumnus vespertilio (Crustacea: Pilumnidae) in Subtropical Okinawa, Japan 
Author: Kyomo, Joel Sr
Date: 2002-07
Publisher: University of Hawai'i Press
Citation: Kyomo J. 2002. Timing and synchronization of the breeding period in Pilumnus vespertilio (Crustacea: Pilumnidae) in subtropical Okinawa, Japan. Pac Sci 56(3): 317-328.
Abstract: Observations on the temporal occurrence of copulating pairs, ovigerous
females, monthly brooding periods, and embryo development stages in
Pilumnus vespertilio Fabricius were carried out in the wild on Okinawa Island,
Japan. The relationship between the female gonad and hepatopancreas during a
reproductive period was also studied. These reproductive activities were observed
in relation to the lunar cycles. An inverse relationship between mass of
the hepatopancreas and development of the gonad was observed. Mating and
breeding activities were perfectly synchronized with the lunar periodicity. Five
broods from May to September were observed in a single breeding period, and
the average brooding period was 21.2 days with an interlude of 8.5 ± 3.1 days
between broods/months. The shortest interlude was between May and June (4
days). A sixth brood that started in October was not followed to the end because
it started with very few ovigerous females. Embryo development time in days
decreased with each stage and averaged 5.3 days per stage. Copulating activity
and appearance of ovigerous females during successive broods (months) were
clearly synchronized with the lunar cycle. Although copulating frequency was
highest after the full moon, nearly 100% of females were ovigerous around the
new moon. All females of anyone sample carried eggs of the same development
stage. All females released their larvae 1-3 days before full moon, coinciding
with a high tide. Larvae are probably released during this time as a survival
strategy against predators such as planktivorous fish and against adverse intertidal
conditions during other times.
ISSN: 0030-8870

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