Sudnik S.A.1, Marin I.N.2 2021. Biological features of symbiotic pea crabs of the genus Pinnixa sensu lato (Decapoda: Brachyura: Pinnotheridae) from Vostok Bay of the Sea of Japan // Arthropoda Selecta. Vol.30. No.2: 167–178 [in English].

1 Kaliningrad State Technical University, Sovietsky pr., 1, Kaliningrad, 236022, Russia. E-mail:

2 A.N. Severtsov Institute of Ecology and Evolution of RAS, Leninsky prosp., 33, Moscow, 119071, Russia. E-mails: ,

doi: 10.15298/arthsel.30.2.04

ABSTRACT. The article describes some biological features (morphometry, sex ratio, reproductive condition, fecundity, egg size and etc.) of symbiotic pea crabs Pinnixa rathbunae (main object) and P. banzu from Vostok Bay of the Sea of Japan. Despite living in association with different hosts (Urechis and Chaetopterus) both species are quite similar in biology: females are slightly dominant in number and slightly larger than males, possess the similar relationships between molting and reproductive cycles and the seasonality of reproduction with the possibility of producing more than one clutch of eggs per a season. The average values of morphometric parameters between the two species do not differ significantly, which indicates their close similarity. Different measurements of exoskeleton, presented in the article, as well as their ratios to the width of carapace (REP) for P. rathbunae and P. banzu, are useful for trophologists reconstructing sizes of these crabs from exoskeleton elements collected in stomachs of different hydrobionts of the Sea of Japan. All these parameters are also compared with other relative representatives of the family Pinnotheridae.

KEY WORDS: Symbiosis, morphometry, reproductive biology, breeding season, oocytes, eggs, fecundity.

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