TY - JOUR

T1 - Variations in life cycle and seasonal sex ratio in the rhizocephalan Peltogasterella gracilis (Boschma, 1927) (Cirripedia: Rhizocephala: Peltogasterellidae)

AU - Kajimoto, Asami

AU - Hoeg, Jens T.

AU - Kato, Kenji

AU - Yusa, Yoichi

PY - 2022

Y1 - 2022

N2 - Most individuals of the rhizocephalan Peltogasterella gracilis () produce only male (larger) or female (smaller) offspring, but some mixed-sex broods appear in autumn. Such variability may be an adaptation to the seasonally changing availability of hosts (for female larvae) and conspecific females (for male larvae), but details of the seasonal variation in the sex ratio and its ultimate causes have not been fully studied in P. gracilis. We studied the life cycle, host availability, and seasonal sex-ratio variation in P. gracilis by samplings from spring to autumn in 2017-2020 in Otaru, and additionally from winter to spring of 2007 in Oshoro Bay, Hokkaido, northern Japan. We measured its prevalence on the hermit crab Pagurus lanuginosus De Haan, 1849, the number of males per externa, the proportion of externae brooding different embryonic stages, and embryo size that are linked to sex. The prevalence was about 20% in most of the sampling period. The number of males per externa was 0.01-0.74 in June 2018-2020, but increased in later months to nearly 1.0. Eyed embryos and nauplii before hatching were common from June or July to September, but they were rare in other seasons. Female embryos were observed in all sampling periods, but male embryos were not found in July or August, by which time most females already have males implanted within their receptacles. It is suggested that P. gracilis releases both female and male larvae according to the availability of unparasitized hosts and of virgin externae, respectively.

AB - Most individuals of the rhizocephalan Peltogasterella gracilis () produce only male (larger) or female (smaller) offspring, but some mixed-sex broods appear in autumn. Such variability may be an adaptation to the seasonally changing availability of hosts (for female larvae) and conspecific females (for male larvae), but details of the seasonal variation in the sex ratio and its ultimate causes have not been fully studied in P. gracilis. We studied the life cycle, host availability, and seasonal sex-ratio variation in P. gracilis by samplings from spring to autumn in 2017-2020 in Otaru, and additionally from winter to spring of 2007 in Oshoro Bay, Hokkaido, northern Japan. We measured its prevalence on the hermit crab Pagurus lanuginosus De Haan, 1849, the number of males per externa, the proportion of externae brooding different embryonic stages, and embryo size that are linked to sex. The prevalence was about 20% in most of the sampling period. The number of males per externa was 0.01-0.74 in June 2018-2020, but increased in later months to nearly 1.0. Eyed embryos and nauplii before hatching were common from June or July to September, but they were rare in other seasons. Female embryos were observed in all sampling periods, but male embryos were not found in July or August, by which time most females already have males implanted within their receptacles. It is suggested that P. gracilis releases both female and male larvae according to the availability of unparasitized hosts and of virgin externae, respectively.

KW - Crustacea

KW - kentrogonid rhizocephalans

KW - life cycles

KW - parasitism

KW - reproductive biology

KW - SACCULINA-CARCINI CRUSTACEA

KW - PARASITIC BARNACLE

KW - LARVAL DEVELOPMENT

KW - HERMIT-CRAB

KW - CYPRIS ULTRASTRUCTURE

KW - LOXOTHYLACUS-PANOPAEI

KW - THOMPSON CRUSTACEA

KW - METAMORPHOSIS

KW - REPRODUCTION

KW - BRIAROSACCUS

U2 - 10.1093/jcbiol/ruac057

DO - 10.1093/jcbiol/ruac057

M3 - Journal article

VL - 42

JO - Journal of Crustacean Biology

JF - Journal of Crustacean Biology

SN - 0278-0372

IS - 4

M1 - ruac057

ER -