Distinct development trajectories and symbiosis modes in vent shrimps.

Most animal species have a singular developmental pathway and adult ecology, but developmental plasticity is well-known in some such as honeybees where castes display profoundly different morphology and ecology. An intriguing case is the Atlantic deep-sea hydrothermal vent shrimp pair Rimicaris hybisae and R. chacei that share dominant COI haplotypes and could represent very recently diverging lineages or even morphs of the same species. Rimicaris hybisae is symbiont-reliant with a hypertrophied head chamber (in the Mid-Cayman Spreading Centre), while R. chacei is mixotrophic with a narrow head chamber (on the Mid-Atlantic Ridge). Here, we use X-ray micro-computed tomography and fluorescence in situ hybridization to show that key anatomical shifts in both occur during the juvenile-subadult transition, when R. hybisae has fully established symbiosis but not R. chacei. On the Mid-Atlantic Ridge, the diet of R. chacei has been hypothetically linked to competition with the obligatorily symbiotic congener R. exoculata, and we find anatomical evidence that R. exoculata is indeed better adapted for symbiosis. We speculate the possibility that the distinct development trajectories in R. hybisae and R. chacei may be determined by symbiont colonization at a "critical period" before subadulthood, though further genetic studies are warranted to test this hypothesis along with the true relationship between R. hybisae and R. chacei.

Description of a new species of the Alpheus edwardsii group (Decapoda: Alpheidae) with a distinctive colour pattern from the Indo-West Pacific.

A new snapping shrimp species of the Alpheus edwardsii (Audouin, 1826) group is described based on two specimens, one male and one female, collected on shallow-water reef flats of the Southern Ari Atoll in the Maldives, with a photographic record from Cebu in the Philippines. Alpheus octocellatus sp. nov. appears to be morphologically closest to A. edwardsii, A. pareuchirus Coutière, 1905, and A. leptochirus Coutière, 1905, but can be distinguished from all of them by a combination of morphological characters, mainly involving the chelipeds, third maxilliped and pleonal sternites. The new species also has a highly diagnostic colour pattern, with four pairs of conspicuous eyespots distributed in a unique and peculiar pattern on the pleon.

A new species of the mud shrimp genus Naushonia Kingsley, 1897 (Decapoda: Gebiidea: Laomediidae) from the Ryukyu Islands, southwestern Japan, inhabiting burrows of an axiidean shrimp.

A new species of the laomediid mud shrimp genus Naushonia Kingsley, 1897 is described and illustrated based on seven specimens collected from Okinawa Island, Ryukyu Islands, southwestern Japan. All specimens of Naushonia karashimai n. sp. were collected from burrows of a large axiidean shrimp, Neaxius acanthus (A. Milne-Edwards, 1879), which inhabits seagrass beds in inner reef lagoons. The new species is easily distinguished from all 16 known congeners by its tridentate rostrum and relatively narrow pereopod 1 palm with a proximally located pollex. Sequences of the mitochondrial 16S rRNA and COI genes were newly generated for five species and two species of Naushonia, including the new species, respectively. Preliminary phylogenetic analysis using sequences of the 16S rRNA gene was performed.

Redescription of Caridina sobrina Riek, 1953 stat. nov. and description of a new species of Caridina from south-eastern Queensland (Decapoda, Atyidae).

Caridina sobrina Riek, 1953, only known from Fraser Island (Queensland, Australia), is redescribed and elevated from subspecies to species level. A morphologically very similar species, Caridina pagei sp. nov., is described from nearby Moreton Island. The taxon known in previous literature as Caridina sp. C2 is also illustrated but left unnamed in view of its complete morphological overlap with C. pagei, despite substantial genetic drift.

Description of two new species of goby-associated snapping shrimps from the tropical western Pacific (Decapoda: Alpheidae: Alpheus).

Two new snapping shrimps associated with gobies are described from the tropical waters of the western Pacific. Alpheus thompsoni sp. nov. is described based on a single adult female from Madang, Papua New Guinea. Alpheus sciolii sp. nov. is described based on several specimens of both sexes from the Solomon Islands, Australia and Vietnam. Both species are part of a larger species complex, which also includes A. djeddensis Coutire, 1897, A. djiboutensis De Man, 1909, A. bellulus Miya Miyake, 1969, A. macellarius Chace, 1988, A. fenneri Bruce, 1994 and A. mannarensis Purushothaman, Abhilash, Kumar Lal, 2021, but can be distinguished from each of them by a combination of morphological characters, and from the latter four species also by the very different colour patterns.

Description of the complete larval development of Lysmata amboinensis (De Man) (Decapoda: Lysmatidae) reared under laboratory conditions.

Complete larval morphological descriptions are currently only known for three of the 48 species of genus Lysmata. The present study describes and illustrates the larval development of Lysmata amboinensis (De Man) reared under laboratory conditions. Lysmata amboinensis larval development is composed by a total of ten zoea and a decapodite stage. The first zoeal stage larvae presents sessile eyes, a carapace with a pterigostomial spine and anterio-ventral marginal denticles, a long, slender, and pointed rostrum, an antennal exopod terminally articled, a pleon with five somites, the fifth one bearing a pair of dorso-lateral spines on the posterior margin, and a triangular shaped telson with 7+7 posterior processes. The decapodite resembles a smaller adult and has extremely long antennas (more than twice the total length of the decapodite), the first two pair of pereiopods with chela, first four pairs of pereiopods with reduced and entire exopods, and fully developed pleopods. The morphological features of L. amboinensis are compared with those currently available for the larval stage of the genus Lysmata.

A new report on the deep-sea sponge-associated Spongicoloides weijiaensis Xu, Zhou & Wang, 2017 (Decapoda: Spongicolidae) from the Southwest Indian Ocean Ridge.

The sponge-associated benthic shrimp Spongicoloides weijiaensis Xu, Zhou & Wang, 2017 is reported for the first time from the Southwest Indian Ridge (SWIR). A single female specimen of S.weijiaensis was associated with the hexactinellid sponge belonging to Dictyaulus sp. that was collected using a benthic sledge from the southwest Indian Ridge at a water depth of 2358 m. The spongicolid shrimp is reported using both classical taxonomic and molecular tools (cytochrome c oxidase subunit 1-COI). The S. weijiaensis specimen from the SWIR appears to represent a morphological variant that has pigmented eyes, telson with thirteen spines, and a broadly rounded setiferous posterior margin. This new report at a latitude of nearly 26° South on the seamount provides the first Mid Ocean Ridge sector record for stenopodidean shrimp known to date.

De novo assembly transcriptome analysis reveals the genes associated with body color formation in the freshwater ornamental shrimps Neocaridina denticulate sinensis.

The body color of Neocaridina denticulate sinensis is a compelling phenotypic trait, in which a cascade of carotenoid metabolic processes plays an important role. The study was conducted to compare the transcriptome of cephalothoraxes among three pigmentation phenotypes (red, blue, and chocolate) of N. denticulate sinensis. The purpose of this study was to explore the candidate genes associated with different colors of N. denticulate sinensis. Nine cDNA libraries in three groups were constructed from the cephalothoraxes of shrimps. After assembly, 75022 unigenes were obtained in total with an average length of 1026 bp and N50 length of 1876 bp. There were 45977, 25284, 23605, 21913 unigenes annotated in the Nr, Swissprot, KOG, and KEGG databases, respectively. Differential expression analysis revealed that there were 829, 554, and 3194 differentially expressed genes (DEGs) in RD vs BL, RD vs CH, and BL vs CH, respectively. These DEGs may play roles in the absorption, transport, and metabolism of carotenoids. We also emphasized that electron transfer across the inner mitochondrial membrane (IMM) was a key process in pigment metabolism. In addition, a total of 6328 simple sequence repeats (SSRs) were also detected in N. denticulate sinensis. The results laid a solid foundation for further research on the molecular mechanism of integument pigmentation in the crustacean and contributed to developing more attractive aquatic animals.

Second finding, first complete specimen and range extension of the rare alpheid shrimp Bermudacaris britayevi Anker, Poddoubtchenko amp; Marin, 2006 (Caridea: Alpheidae).

The very uncommon alpheid shrimp Bermudacaris britayevi Anker, Poddoubtchenko Marin, 2006, previously known only from the incomplete holotype from Nha Trang Bay, Vietnam, is recorded from Guam, Mariana Islands, extending its previously known distribution range into the oceanic islands of the western Pacific. The single specimen from Guam, an ovigerous female, was collected adjacent to a near-shore coral reef, on fine sand under a large piece of coral rubble, at a depth of about 10 m. This habitat is different from the collection data of the holotype, which was extracted from a burrow of unknown host on an intertidal sand-mud flat close to mangroves. Despite these ecological differences, the specimen from Guam corresponds to the holotype of B. britayevi in all diagnostic morphological characters and can be distinguished from the closely related B. australiensis Anker Komai, 2004 and B. harti Anker Iliffe, 2000. Since the holotype of B. britayevi was lacking one of the chelipeds, the complete specimen from Guam enables to complement the original description of the species. The stouter (= major) cheliped of the Guam specimen is illustrated to show a marked difference in the armature of the cheliped fingers, between the left and right cheliped. The colour pattern of B. britayevi, which was superficially described in the original description, is herein illustrated by photographs of the living individual. The relatively low number and large size of eggs in the Guam specimen of B. britayevi suggests an abbreviated larval development in this species.

Cycloachelous levigatus sp. nov., a new swimming crab (Crustacea: Decapoda: Portunidae) from the South China Sea.

A new species of portunid crab from the genus Cycloachelous Ward, 1942 is described from Vietnamese waters. Cycloachelous levigatus sp. nov. is morphologically most similar to C. orbitosinus (Rathbun, 1911), which was originally described from the syntype series collected from Western Pacific area (Cargados Carajos Islands, Amirante Islands, Seychelles) and C. octodentatus (Gordon, 1938) described from one single male from Singapore. There are differences in the sternal segments, third maxilliped, chela, abdomen and male gonopode shapes. The specific status of C. levigatus sp. nov. is also clearly supported by molecular data. Aside from a comparison of this new species with other known congeners, new photographs of syntypes of C. orbitosinus and the holotype of C. octodentatus are also provided.

Description of Paraxiopsis/ kensleyi/ n. sp., a new axiid lobster from the Gulf of Mexico (Crustacea: Decapoda: Axiidea).

A new species of axiid was discovered during sampling offshore deep banks on the middle continental shelf off Louisiana. Paraxiopsis kensleyi n. sp. appears to inhabit interstices and cavities of coralline algal rubble, rhodoliths, coral rubble, and other eroded calcareous substrates. Weakly separated from Eutrichocheles Wood-Mason, 1876 on the basis of morphology, present assignments of western Atlantic species to Paraxiopsis de Man, 1905 are regarded as provisional. The new species is described morphologically, and the coloration of freshly captured specimens is documented and compared to related species where possible. Coloration readily distinguishes mature specimens of the new species from Paraxiopsis spinipleura Kensley, 1996, with which it was initially confused. The diagnosis includes GenBank accession numbers for COI sequences to allow future molecular phylogenetic comparisons. Compared to regional species that share a similar dentation or spination on the submedian carina, the pleon of the new species is distinctive in the truncate ventral margin on pleura 2-4, as opposed to being broadly rounded or directed ventrally in an acutely triangular tip. The new species is the eighteenth species of Paraxiopsis worldwide and the ninth from western Atlantic waters, seven of which are now known to range into the Gulf of Mexico. An updated key to western Atlantic members of the genus is provided.

New data on Beurlenia araripensis Martins-Neto & Mezzalira, 1991, a lacustrine shrimp from Crato Formation, and its morphological variations based on the shape and the number of rostral spines.

Fossil freshwater carideans are very rare worldwide. Here, we present new taxonomic remarks about Beurlenia araripensis from the Early Cretaceous laminated limestones of the Crato Formation, Araripe Basin, northeastern Brazil. We analyzed five fossil samples, testing the morphological variations such as, rostrum with 5 to 14 supra-rostral spines and 2 to 3 sub-rostral spines, which appears as serrate for Caridea. This variation demonstrates a morphologic plasticity also seen in extant species of the group, such as those of the genera Macrobrachium and Palaemon.

The orbital hoods of snapping shrimp have surface features that may represent tradeoffs between vision and protection.

Snapping shrimp (Alpheidae) are decapod crustaceans named for the snapping claws with which they produce cavitation bubbles. Snapping shrimp use the shock waves released by collapsing cavitation bubbles as weapons. Along with their distinctive claws, snapping shrimp have orbital hoods, extensions of their carapace that cover their heads and eyes. Snapping shrimp view the world through their orbital hoods, so we asked if the surfaces of the orbital hoods of the snapping shrimp Alpheus heterochaelis have features that minimize the scattering of light. Using SEM, we found that surface features, primarily microbial epibionts, covered less space on the surfaces of the orbital hoods of A. heterochaelis (∼18%) than they do elsewhere on the carapace (∼50%). Next, we asked if these surface features influence aerophobicity. By measuring the contact angles of air bubbles, we found the orbital hoods of A. heterochaelis are less aerophobic than other regions of the carapace. Surfaces that are less aerophobic are more likely to have cavitation bubbles adhere to them and are more likely to have shock waves cause new cavitation bubbles to nucleate upon them. Computational modeling indicates the orbital hoods of A. heterochaelis face a functional trade-off: fewer surface features, such as less extensive communities of microbial epibionts, may minimize the scattering of light at the cost of making the adhesion and nucleation of cavitation bubbles more likely.

Study on the heterogeneous material coupling connection characteristics and mechanical strength of Oratosquilla oratoria mantis shrimp saddle.

The microstructure, chemical composition and mechanical strength of heterogeneous materials of mantis shrimp (Oratosquilla oratoria) saddle were studied. As the key component of the striking system, the saddle comprised two distinct layers including outer layer and inner layer. The outer layer contained blocky microtubules and exhibited compact appearance. The inner layer presented a typical periodic lamellar structure. Due to the change of the thickness of the mineralized outer layer, the organic multilamellar structure became the foundation and enhanced the connection strength (4.55 MPa) at the connect regions between the saddle and merus exoskeleton and membrane, respectively. In the process of fracture, the lamellar structure dispersed the stress effectively by the change of the crack deflection direction and the microfibrils ordered arrangement. The exploration of mantis shrimp saddle region is beneficial to understand the striking system and provided the possibility for the stable connection of heterogeneous materials in engineering fields. The microstructure, heterogeneous material connection characteristics and high mechanical strength of saddle provide bionic models for the preparation of fiber-reinforced resin composites and soft composites.

First worldwide molecular phylogeny of the morphologically and ecologically hyperdiversified snapping shrimp genus Alpheus (Malacostraca: Decapoda).

Hyperdiverse animal groups raise intriguing questions regarding the factors that generate and maintain their diversity. The snapping shrimp genus Alpheus (with >300 described species) is a spectacularly diversified group of decapod crustaceans that serves as an exemplary system for addressing evolutionary questions regarding morphological adaptations, symbiosis, cryptic diversity and molecular divergence. A lack of information regarding evolutionary relationships among species has limited investigations into the mechanisms that drive the diversification of Alpheus. Previous phylogenetic studies of Alpheus have been restricted in scope, while molecular datasets used for phylogenetic reconstructions have been based solely on mitochondrial and a handful of nuclear markers. Here we use an anchored hybrid enrichment (AHE) approach to resolve phylogenetic relationships among species of Alpheus. The AHE method generated sequence data for 240 loci (>72,000 bp) for 65 terminal species that span the geographic, ecological and taxonomic diversity of Alpheus. Our resulting, well-supported phylogeny demonstrates a lack of monophyly for five out of seven morphologically defined species groups that have traditionally been used as a framework in Alpheus taxonomy. Our results also suggest that symbiotic associations with a variety of other animals have evolved independently in at least seven lineages in this genus. Our AHE phylogeny represents the most comprehensive phylogenetic treatment of Alpheus to date and will provide a useful evolutionary framework to further investigate questions, such as various modifications of the snapping claw and the role of habitat specialization and symbiosis in promoting speciation. Running head: PHYLOGENY OF THE SNAPPING SHRIMP GENUS ALPHEUS.

Masters of communication: The brain of the banded cleaner shrimp Stenopus hispidus (Olivier, 1811) with an emphasis on sensory processing areas.

The pan-tropic cleaner shrimp Stenopus hispidus (Crustacea, Stenopodidea) is famous for its specific cleaning behavior in association with client fish and an exclusively monogamous life-style. Cleaner shrimps feature a broad communicative repertoire, which is considered to depend on superb motor skills and the underlying mechanosensory circuits in combination with sensory organs. Their most prominent head appendages are the two pairs of very long biramous antennules and antennae, which are used both for attracting client fish and for intraspecific communication. Here, we studied the brain anatomy of several specimens of S. hispidus using histological sections, immunohistochemical labeling as well as X-ray microtomography in combination with 3D reconstructions. Furthermore, we investigated the morphology of antennules and antennae using fluorescence and scanning electron microscopy. Our analyses show that in addition to the complex organization of the multimodal processing centers, especially chemomechanosensory neuropils associated with the antennule and antenna are markedly pronounced when compared to the other neuropils of the central brain. We suggest that in their brains, three topographic maps are present corresponding to the sensory appendages. The brain areas which provide the neuronal substrate for these maps share distinct structural similarities to a unique extent in decapods, such as size and characteristic striated and perpendicular layering. We discuss our findings with respect to the sensory landscape within animal's habitat. In an evolutionary perspective, the cleaner shrimp's brain is an excellent example of how sensory potential and functional demands shape the architecture of primary chemomechanosensory processing areas.

Neuroanatomy of a hydrothermal vent shrimp provides insights into the evolution of crustacean integrative brain centers.

Alvinocaridid shrimps are emblematic representatives of the deep hydrothermal vent fauna at the Mid-Atlantic Ridge. They are adapted to a mostly aphotic habitat with extreme physicochemical conditions in the vicinity of the hydrothermal fluid emissions. Here, we investigated the brain architecture of the vent shrimp Rimicaris exoculata to understand possible adaptations of its nervous system to the hydrothermal sensory landscape. Its brain is modified from the crustacean brain ground pattern by featuring relatively small visual and olfactory neuropils that contrast with well-developed higher integrative centers, the hemiellipsoid bodies. We propose that these structures in vent shrimps may fulfill functions in addition to higher order sensory processing and suggest a role in place memory. Our study promotes vent shrimps as fascinating models to gain insights into sensory adaptations to peculiar environmental conditions, and the evolutionary transformation of specific brain areas in Crustacea.

Functional cytology of the hepatopancreas of decapod crustaceans.

This article reviews the morphogenesis, morphology, histology, ultrastructure, and structural-functional relationships of the hepatopancreas, the main metabolic organ of the Decapoda. The hepatopancreas develops in early larval stages from a pair of lateral lobes of the midgut anlage. In adults, it consists of hundreds of blindly ending tubules that are enveloped by a muscle net consisting of longitudinal and circular fibers. Stem cells at the distal ends of the tubules give rise to three ultrastructurally different epithelial cell types, the R-, F-, and B-cells. Histochemistry, immunohistochemistry, in situ hybridization, and monitoring of ultrastructural changes under different experimental conditions allowed the attribution of functions to these cell types. R-cells serve for the absorption and metabolization of nutrients, storage of energy reserves and minerals, synthesis of lipoproteins for export to other organs, detoxification of heavy metals, and excretion of uric acid. F-cells synthesize digestive enzymes and blood proteins involved in oxygen transport and immune defense. They also detoxify some heavy metals and probably organic xenobiotics. B-cells are assumed to produce and recycle fat emulsifiers. The hepatopancreas tubules lack nerves. The presence of scattered M-cells with putative endocrine function in the epithelium suggests that the hepatopancreas is mainly hormonally controlled. M-cells probably represent a self-perpetuating cell lineage independent from E-cells. The interstitium between the tubules contains connective tissue, arterioles, hemolymph with circulating hemocytes, and fixed phagocytes that eliminate pathogens. The hepatopancreas is histologically and ultrastructurally uniform throughout the Decapoda, despite their broad variety in body size, morphology, life style, and ecology. However, in a few cavernicolous and deep-sea shrimps parts of the hepatopancreas are transformed into large oil storing and bioluminescent compartments. Within the malacostracan crustaceans, the hepatopancreas of the Decapoda is most similar to the digestive gland of the Euphausiacea, supporting close taxonomic relationship of these two taxa.

Ontogenetic development of gonads and external sexual characters of the protandric simultaneous hermaphrodite peppermint shrimp, Lysmata vittata (Caridea: Hippolytidae).

The peppermint shrimp Lysmata vittata (Caridea: Hippolytidae) is a marine caridean shrimp popular in marine aquarium trade. The species is known to display the sexual system of protandric simultaneous hermaphrodite. In this study, based on captive bred specimens, the complete ontogenetic gonad development of L. vittata was studied both morphologically and histologically, from newly settled juveniles until they reached euhermaphrodite phase. It was found that in all specimens examined (carapace length: 1.8-8.5 mm), including the newly settled juveniles, possessed ovotestes, which comprised of an anterior ovarian and a posterior testicular part. Based on both morphological (e.g., size, color and shape) and histological features (e.g., oogenesis and spermatogenesis), four gonadal development stages were defined and described for L. vittata. From Stage I to III, the testicular part of the gonad became gradually mature but the ovarian part was still immature, which is defined as the male phase. At the male phase, cincinulli (5-8 hooks) presented at the tips of the appendix interna on the first pair of pleopods while appendices masculinae (AM), in a form of a stick structure with spines, presented at the inner edge of the appendix interna (AI) on the second pair of pleopods. At Stage IV, both the testicular part and the ovarian part were mature and hence is defined as euhermaphrodite phase. At the euhermaphrodite phase, most individuals lacked cincinulli and appendices masculinae on the first and second pair of pleopods respectively. This is the first time that complete ontogenetic gonadal and external sexual character development have been described and staged for a species from the genus Lysmata from newly settled juveniles to euhermaphrodite phase.

Palaeoecology of Voulteryon parvulus (Eucrustacea, Polychelida) from the Middle Jurassic of La Voulte-sur-Rhône Fossil-Lagerstätte (France).

Exceptional and extremely rare preservation of soft parts, eyes, or syn-vivo associations provide crucial palaeoecological information on fossil-rich deposits. Here we present exceptionally preserved specimens of the polychelidan lobster Voulteryon parvulus, from the Jurassic of La Voulte-sur-Rhône Fossil-Lagerstätte, France, bearing eyes with hexagonal and square facets, ovaries, and a unique association with epibiont thecideoid brachiopods, giving insights onto the palaeoenvironment of this Lagerstätte. The eyes, mostly covered in hexagonal facets are interpreted as either apposition eyes (poorly adapted to low-light environment) or, less likely, as refractive or parabolic superposition eyes (compatible with dysphotic palaeoenvironments). The interpretation that V. parvulus had apposition eyes suggests an allochthonous, shallow water origin. However, the presence of thecideoid brachiopod ectosymbionts on its carapace, usually associated to dim-light paleoenvironments and/or rock crevices, suggests that V. parvulus lived in a dim-light setting. This would support the less parsimonious interpretation that V. parvulus had superposition eyes. If we accept the hypothesis that V. parvulus had apposition eyes, since the La Voulte palaeoenvironment is considered deep water and had a soft substrate, V. parvulus could have moved into the La Voulte Lagerstätte setting. If this is the case, La Voulte biota would record a combination of multiple palaeoenvironments.