Larval development of the Caribbean king crab Maguimithrax spinosissimus (Lamarck, 1818), the largest brachyuran in the western Atlantic (Crustacea: Decapoda: Majoidea)

The complete larval development of the spider crab Maguimithrax spinosissimus (Lamarck, 1818) is re-described and illustrated in detail from laboratory-reared material. The development consisted of the typical pattern reported for the Majoidea, two zoeal stages and one megalopa. The complete larval development from hatching to first crab lasted 5–6 days at temperatures that ranged between 24–28 °C. Both zoeal stages of M. spinosissimus exhibited moderate reduction in the number of setae in the maxilla and maxillipeds, from the first to the second zoeal stage, when compared with other closely related species. Maguimithrax spinosissimus can be easily distinguished from other species belonging to the closely related genus Mithrax by the (i) setation of the endopod of the maxillule, maxilla and second maxilliped in both zoeal stages; (ii) setation of the scaphognathite of the maxilla in the first zoeal stage; (iii) setation of the basis of maxilliped I in the second zoeal stage and megalopa; (iv) morphology of the antennule and antenna in the second zoeal stage; and (v) setation of the antennule, coxal endite of maxilla, and exopod of second maxilliped in the megalopa. All these characters support the recent generic status of Maguimithrax within the Mithracidae. Additional morphological details, not available previously, are provided. This study will provide support for conservation strategies in this species.

The first zoeal stage of the yellow land crab Johngarthia lagostoma (Milne Edwards, 1837) (Decapoda: Brachyura: Gecarcinidae)

The objective of this paper is to describe and illustrate the first zoeal stage of the largest land crab of the Tropical Atlantic, Johngarthia lagostoma (Milne Edwards, 1837) (Brachyura: Gecarcinidae). A larval description of J. lagostoma was previously not available. Larvae were obtained from ovigerous females on Rocas Atoll and Fernando de Noronha Archipelago, Brazil. Twenty larvae were randomly chosen to be dissected and described in detail, while 40 others (20 larvae from each island) were measured only. The published description of the congener J. planatus (Stimpson, 1860) larvae was used for a comparison of larval morphology. Some morphological differences between the first zoeal stage of these two species were: The absence or presence of a simple shorter seta on antennule, number of the minute terminal spines on the antenna, setation of the coxal endite of the maxilla, exopod unsegmented of the first and second maxilliped, and a single mid-dorsal seta on first pleonite. These results and differences observed between these species can assist in studies on phylogenetic relationships within the Family Gecarcinidae MacLeay, 1838, as well as in the identification of the larvae of J. Lagostoma in plankton samples from the tropical Atlantic.

Morphology of the first three zoeal stages of the deep-sea caridean shrimp Heterocarpus fascirostratus Yang, Chan & Kumar, 2018 (Crustacea, Decapoda, Pandalidae)

The larvae of the deep-sea pandalid shrimp Heterocarpus fascirostratus Yang, Chan & Kumar, 2018 were successfully hatched and cultured to the third zoeal stage. The larvae reached the third zoeal stage nine days after hatching at a water temperature of 21 ± 1 °C. Although members of Heterocarpus A. Milne-Edwards, 1881 have rather diverse body forms and are often separated into many species groups, the early zoeal morphology of H. fascirostratus follows the general developmental pattern of the species in Heterocarpus. The main differences amongst these larvae are body size, spines on the anteroventral margin of the carapace, and the endopod setation of the third maxilliped.

The first larval stage (Zoea I) description of the caridean shrimp Ogyrides occidentalis (Ortmann, 1893) (Alpheoidea: Ogyrididae) reveals congruence with taxonomic status

A complete and detailed description of the first zoeal stage of Ogyrides occidentalis is provided. Larvae were obtained in the laboratory from a female with embryos collected in Ubatuba, State of São Paulo, Brazil. The morphological characters are compared with previous description of the close related O. alphaerostris. Despite of some similarities (number of appendages, pleonites, and setae on the majority of appendages) substantial differences were found between the two species, as the size of larvae and rostrum and segmentation of some structures (antenna exopod, first maxilliped coxa and basis). However, these differences must be interpreted carefully because larval description of O. alphaerostris was conducted before the proposed standardization for decapod larval morphology descriptions. The present larval description furnished additional information to corroborate the recent resurrection of O. occidentalis and will be useful for future comparative and ecological research.

First zoeal stage morphology of Alpheus carlae and A. intrinsecus (Decapoda, Caridea, Alpheidae) obtained in the laboratory

The first zoeal stages of the snapping shrimps Alpheus carlae and A. intrinsecus from Brazil were obtained from laboratory-hatched specimens and a detailed morphological description is provided. The morphological characteristics of both species are compared with available descriptions of other Alpheus species with a known first zoeal stage. Remarks from a semi-quantitative comparison of species belonging to A. armillatus species complex (A. carlae and A. brasileiro) and a comparison between larvae of A. intrinsecus from two localities in Brazil are presented. It was possible to distinguish first zoea of both species from the other congeners based on morphology. No intraspecific variability was detected between A. intrinsecus larvae obtained from two locations. Some structures showed differences between species of the A. armillatus complex. However, generalizations and conclusions based on larval morphology for taxonomic rearrangements at this point need to be made with caution and accuracy, since data of a sufficient number of species are not yet available for comparison.

Description of the first zoeal stage of Synalpheus apioceros Coutière, 1909 (Caridea: Alpheidae), including a comparative analysis with larval morphology from the genus Synalpheus Spence Bate, 1888

Herein, the Zoea I of Synalpheus apioceros is described, followed by a comparative analysis of the first larval stage from Synalpheus. Larvae were obtained from two ovigerous females sampled in Ubatuba, São Paulo. The morphology of the Zoea I of S. apioceros was compared to five other Synalpheus species whose structures were previously described: S. biunguiculatus, S. minus, S. neomeris, S. pectiniger, and S. tumidomanus. A set of unique morphological characteristics was found for S. apioceros: exopod of antennule with 4 aesthetascs and 1 plumose seta; coxal endite of maxillule with 2 simple setae plus 2 plumose setae; basial endite of maxillule with 2 simple setae plus 2 short spines; endopod of maxillule with 1 plumose seta plus 2 simple setae; basial endite of maxilla bilobed with 2 (1 plumose and 1 simple) + 2 (1 plumose and 1 simple) setae; coxal endite of maxilla bilobed with 2 + 1 plumose setae; endopod of maxilla with 3 (1 plumose and 2 simple) terminal setae + 2 simple setae; endopod of first maxilliped unsegmented with 3 terminal simple setae; basis of first maxilliped with 5 spines; endopod of second maxilliped 5-segmented with 0, 0, 0, 1 plumodenticulate, 4 (1 serrate + 3 simple) setae; endopod of third maxilliped 5-segmented with 0, 0, 0, 1 simple, 3 simple setae; pereiopods 1st to 3rd birramous and 4th and 5th uniramous. S. apioceros shows higher morphological similarity with S. minus, followed by S. tumidomanus, S. neomeris and S. pectiniger, probably since these species present extended larval development. Besides the similar morphology among species, the unique attributes presented here are important for the genus’ taxonomy, being fundamental for identifying the first larval stages of Synalpheus, as well as for subsidizing information for species identification keys.

First zoeal stage of the snapping shrimps Alpheus formosus Gibbes, 1850 and Alpheus malleator Dana, 1852 (Caridea: Alpheidae), with new characters to the genus

The first zoeae of Alpheus formosus Gibbes, 1850 and Alpheus malleator Dana, 1852 are described and illustrated for the first time, based on laboratory-hatched larvae from parental females sampled in Vitória Island, Ubatuba, Brazil. Both species shared many characters with other species of genus Alpheus Fabricius, 1798, but they also have some exclusive characters as 10 setae on the basis of the maxilla, first maxilliped with endopod 2-segmented and exopod 4-segmented, second maxilliped with exopod 4-segmented, presence of bud only of the first pereopod, presence of anal spine and simple dorsal setae on the pleon. The zoea I of both species, nevertheless, can be separated by segmentation in the exopod of the antenna (8 in A. formosus, 6 in A. malleator); segmentation in the endopod and exopod of the third maxilliped (5 in A. formosus and 4 in A. malleator); peduncle of antennule 3-segmented in A. formosus (unsegmented or 2-segmented in other species) and presence of a medial tubercle in the proximal segment in the exopod of the antenna of A. malleator (absent in A. formosus, not reported in all other species). In this study three new characters are proposed to be analyzed in zoea of the genus Alpheus: presence of anal spine in both species (absent in Alpheus saxidomus Holthuis, 1980, but not reported in other species) and for the first time reported, presence of a tubercle in the exopod of the antenna (present only in A. malleator) and presence of simple dorsal setae on the pleon (both species), here analyzed under light and scanning electron microscopy.

Extended larval development in the hololimnetic shrimp Macrobrachium pantanalense (Decapoda, Palaemonidae) reared in the laboratory

The postembryonic development of Macrobrachium pantanalense, a freshwater shrimp from central South America, was experimentally studied in the laboratory. In contrast to most other hololimnetic Caridea, this species passes through an extended larval phase with intraspecific variability in the number and morphology of stages. Here we describe the shortest developmental pathway comprising nine zoeal stages, the first post-zoeal stage (morphologically transitional between a late larva and an early juvenile), and an early juvenile with vestiges of larval traits. Post-zoeal development is characterized by a gradual reduction of the natatory exopods of the pereiopods (a larval character) and a concurrent transformation of the endopods to walking legs (juvenile trait). A comparison with the larvae of a closely related, often confused estuarine species from northern South America, M. amazonicum, revealed consistent interspecific differences, especially in the morphology of the fifth pereiopod, allowing for an unambiguous distinction of these two allopatric congeners.