A rhizocephalan parasite of the hermit crab Pagurus minutus Hess, 1865 (Decapoda, Paguridae) is described from Russian waters using morphological and molecular methods. Partial sequences of the mitochondrial cytochrome c oxidase subunit I gene (COI) were used as a genetic marker. We refer this species to Peltogaster reticulata Shiino, 1943 (Rhizocephala, Peltogastridae) based on its morphological description, since genetic data for the species from its type locality are lacking. The species can be distinguished from its known congeners by the reticular pattern of the external cuticle. Peltogaster reticulata is the sister taxon to P. postica Yoshida & Osawa, 2011 (in Yoshida et al. 2011), inhabiting the same host in southwestern Japan. The complete larval development of Peltogaster reticulata, including five naupliar and one cypris stage, is described and illustrated using SEM.

Larval development of the mud shrimp Upogebia issaeffi (Balss, 1913) (Decapoda: Gebiidea: Upogebiidae) is describedand illustrated for the first time from material reared in the laboratory. The development includes four zoeal and a singlemegalopal stages. At 20–22°C the first megalopa was attained 12 days after hatching. U. issaeffi is distinguished from U.major, the second upogebiid species inhabiting Russian waters of the Sea of Japan, by the presence of the fourth zoeal stage and considerably more intensive larval setation.

Zoeal stages of the mud shrimp Nihonotrypaea petalura (Stimpson, 1860) (Decapoda: Axiiidea: Callianassidae) inhabiting Peter the Great Bay (Sea of Japan) is described and illustrated from the larvae reared in the laboratory individually. The development included seven zoeal stages before molting to the megalopa. At 22-23°C the first megalopa was attained 26 days after hatching. A range of the number of zoeal stages in the family Callianassidae is analyzed. The possibility of variation of the number of zoeal stages of burrowing shrimps in different populations of the same species and/or under different laboratory conditions is discussed.

The complete larval development of the lobster shrimpLeonardsaxius amurensis(Kobjakova, 1937) (Decapoda: Axiidea: Axiidae) is described and illustrated for the first time. The first zoeae of this species were collected from the plankton samples and reared in the laboratory before moulting to the megalopa. A molecular genetic analysis based on comparison of partial mitochondrial COI, 12S rDNA and 16S rDNA sequence data confirmed the identity of axiid larvae found in the plankton andL. amurensisadults collected in the same area. The larval development ofL. amurensisincludes five zoeal stages and a single megalopa. Zoeae I ofL. amurensisare characterized by the presence of one short posterodorsal spine on the fifth pleonite in contrast to the larvae of related sympatric speciesBoasaxius princepshaving four posterodorsal spines on the pleonites 2–5.Leonardsaxius amurensisoccupies an intermediate position between lobster shrimps with abbreviated pelagic development (2–3 zoeal stages) and species with long development (up to eight zoeal stages). Thus, the number of zoeal stages in the family Axiidae varies widely, similarly to that in the families Callianassidae and Upogebiidae.

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