The morphology of the zoeal stages IX and XI of the shrimp Thalassocaris lucida is described and illustrated in detail from plankton specimens identified by barcoding of the mitochondrial 16S ribosomal RNA gene (sequence similarities 99.4–99.6%). The present study confirms the larval morphology of Thalassocaris, that shows distinct features within Pandaloidea: (1) carapace broad and dorsoventrally flattened, (2) coxal endite of maxilla with only one lobe, (3) basis of third maxilliped with a distal globose lobe. On the other hand, the funnel-shaped eyes, and the development with long series of larval stages of Thalassocaris indicate affinities with some genera of Pandalidae which corroborates the results of recent phylogenetic analyses in abandoning the family status of Thalassocarididae.

The brush-clawed shore crab Hemigrapsus takanoi is a native species from the Western Pacific and an invader of the European Atlantic coast from northern Spain to southern Denmark. Despite the increasing concern about its rapid expansion, little is known about the early stages in its life history. In the present study, the larval morphology of H. takanoi is described and illustrated from specimens obtained in the laboratory from its type locality, Tokyo Bay, Japan. Its larval development follows the pattern of Varunidae, that involves five zoeae and one megalopa. The morphological characters of the larvae of H. takanoi are compared with those of the other known Hemigrapsus species of the North Pacific. In addition, to facilitate an early detection of the invasive species of Varunidae inhabiting European Atlantic waters, a summary of the key characters to identify their larval stages is included.

The complete larval development of the lobster shrimp Leonardsaxius 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 and L. amurensis adults collected in the same area. The larval development of L. amurensis includes five zoeal stages and a single megalopa. Zoeae I of L. amurensis are characterized by the presence of one short posterodorsal spine on the fifth pleonite in contrast to the larvae of related sympatric species Boasaxius princeps having four posterodorsal spines on the pleonites 2–5. Leonardsaxius amurensis occupies 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.

Upogebia vasquezi inhabits the western Atlantic in the regions of southern Florida, the Bahamas, Central America and Brazil (from the States of Maranhão to São Paulo). Its occurrence has been extended to the coastal region of the State of Pará (northern Brazil). There are few descriptions of the larval development of the 116 known species of Upogebia. The present study offers the first description and illustrations of the first two larval stages (zoeas I and II) of U. vasquezi reared in laboratory. The larval features of U. vasquezi were compared with those of two other species of Upogebia, revealing very similar morphological characteristics among species in zoea I. The main variation in this larval stage was in the segmentation of the maxillulary endopod. In zoea II, the number of setae on the scaphognathite was different among some species of Upogebia. The present study contributes to the available literature on the identification of thalassinidean larvae.

The larval and post-larval behaviour, growth, colour, and morphology of the brown box crab (Lopholithodes foraminatus) are described for the first time based on laboratory reared animals. A detailed morphological description is provided for 4 zoeal stages, the glaucothoe, and the first crab instar. Selected morphological changes over the remainder of the first year of development are also described. Data are presented on larval growth at 11°C and on zoeal stage durations at approximately 8°C, 12°C and 16°C. While the 4 zoeal stages are planktotrophic, the glaucothoe does not feed; a life history character that has been termed ‘secondary lecithotrophy’. Growth of L. foraminatus larvae and post-larvae is generally similar to that of other North Pacific lithodids with planktotrophic zoeae. Zoeal stage durations decrease with increasing temperature. This relationship levels off at approximately 16°C, a higher temperature than in lithodid species from colder regions. Carapace morphology is suggested as a diagnostic character of larval and post-larval stages of Lopholithodes foraminatus. Secondary lecithotrophy may be widespread or even universal among lithodids and also occurs in pagurid hermit crabs. If the family Lithodidae is indeed nested within the Paguridae, as suggested by recent phylogenetic hypotheses based on molecular evidence, secondary lecithotrophy may be plesiomorphic in lithodids.

A dichotomous identification key for brachyuran zoeal stages from Peter the Great Bay (Russian waters of the Sea of Japan) is provided for the first time. The key covers 16 taxa identified to species level and uses only the most conspicuous external characters of larvae that are easy to observe under a stereomicroscope without specimens dissection. The key is based on the accounts by various authors and new original descriptions of larvae obtained both from plankton samples and from laboratory culture. Brief descriptions of larvae of 16 brachyuran species are also included.

Osmoregulation and salinity tolerance were studied in zoeae 1 and instar IX juveniles of Chionoecetes opilio. In zoeae 1, the lower and upper lethal salinities for 50% of the animals (LS 50) at 14 °C were about 10 and 42‰ at 24 h, 18 and 41‰ at 48 h, 25 and 38‰ at 96 h. In juveniles, the approximate 48 h LS 50 s at 6 °C were 13.5 and 46‰. Both developmental stages are able to withstand relatively ample but brief variations of salinity. Their short-term euryhalinity is discussed in relation to the salinity of their habitat. Zoeae were hyper-osmoconformers. Juveniles were osmoconformers and isoionic to the external medium except for Mg++ which was hypo-regulated. Isosmotic and isoionic regulation in post-metamorphic stages are presumably an attribute of the family Majidae. The pattern of osmoregulation in zoeae 1 and juveniles relate C. opilio to the first of three groups of species previously characterized by their pattern of ontogeny of osmoregulation.