Vol. 60, 2021 (update: 2021.02.20; 04.08) Seasonal Changes in the Sexual Size Dimorphisms of the Chelipeds and Pleons of the Porcellanid Crab Petrolisthes japonicusKatsuyuki
Hamasaki* doi:10.6620/ZS.2021.60-18
Department
of Marine Biosciences, Tokyo University of Marine Science and
Technology, Konan, Minato, Tokyo 108-8477, Japan. *Correspondence:
E-mail: hamak@kaiyodai.ac.jp (Hamasaki) Received 5 August 2020 / Accepted 5
February 2021 Decapod
crustaceans develop secondary sexual structures, such as large
chelipeds for weaponry and/or display in males and a wider pleon for
incubating eggs in females. These structures should be costly to
produce and maintain; hence, the crustacean reproductive strategy might
be adaptive to conserve energy for developing secondary sexual
characteristics during a reproductive season. However, little is known
about seasonal changes in the sexual size dimorphisms of the chelipeds
and pleons of decapod crustaceans. Anomuran crabs from the family
Porcellanidae exhibit a true crab-like body shape, with relatively
large chelipeds for their body size and a well-developed pleon. They
also show sexual size dimorphism (i.e.,
males with larger chelipeds and females with wider pleons); therefore,
it was expected that seasonal changes in the sexual size dimorphisms of
these organs would occur in porcellanid crabs. We tested this
expectation using Petrolisthes
japonicus,
which is common on the intertidal cobble and boulder shores of the
temperate and tropical regions of Japan. We employed allometric growth
analyses of the cheliped and pleon dimensions of P. japonicus
females and males collected over a year. Our analyses supported our
expectation regarding the seasonal changes in the sexual size
dimorphisms of the chelipeds and pleons in P. japonicus.
Intersexual size dimorphism of the chelipeds and pleons was evident
during the breeding season: females allocated more energy to pleon
growth, while reducing cheliped growth, and investment in the pleon
increased with increasing female body size, whereas males invested
their energy in cheliped growth and investment in chelipeds increased
with increasing male body size. In the nonbreeding season, females and
males conserved energy by reducing the size of pleons and chelipeds
relative to their respective body sizes. Our results highlighted the
sex-specific and season-dependent resource allocation and reproductive
strategies of porcellanid crabs. Key words: Allometric growth, Life history, Reproductive strategy, Secondary sexual traits, Sexual maturity. Citation:
Hamasaki K, Dan S. 2021. Seasonal changes in the sexual size
dimorphisms of the chelipeds and pleons of the porcellanid crab Petrolisthes japonicus. Zool Stud 60:18. doi:10.6620/ZS.2021.60-18. Supplementary Materials: Fig. S1 | Table S1 | Table S2 | Table S3 | Table S4 |