A Rich and Highly Endemic Decapod Crustacean Fauna from the Middle Jurassic of North-east France

Decapod crustaceans are relatively widespread in Jurassic deposits of Europe and a small number have been collected from the north-east of France. A new fossil of a macrurous decapod assigned to Eryma burgundiaca sp. nov., an erymid lobster, is described from this area and comparisons are made with closely allied species from Europe. Probable pagurid anomurous decapods are represented by Orhomalus magnificus sp. nov., Palaeopagurus acutus sp. nov. and Palaeopagurus neraudeaui sp. nov. No brachyurous decapods are presently known from the fauna. Based on the associated ammonites, the material is considered to be Callovian in age.     

5-HT和DA对虾蟹打斗行为影响的研究进展

5-羟色胺(5-HT)和多巴胺(DA)是两种神经递质,可与众多不同类型的受体结合发挥多种重要的生理功能.现已证明其广泛分布于多种动物的不同组织中,在动物的打斗行为活动中起着重要的调节作用.目前,在虾蟹中已被报道的5-HT受体主要有5种,分别是5-HT1A、5-HT1B、5HT2A、5HT2B和5-HT7;DA受体主要为DA1A、DA1B、DA2和DA4.5-HT和DA及其受体分布存在明显的种属和组织特异性.5-HT和DA参于了虾蟹打斗行为的调节过程并有不同的调节机理.5-HT可以调节环磷酸腺苷(cAMP)或高血糖激素(CHH)的释放,促进或抑制虾蟹打斗行为;而DA同样能够通过调节cAMP及COMT等物质的释放来调节虾蟹打斗行为.     

Ingestion of Large Centric Diatoms, Mangrove Detritus, and Zooplankton by Zoeae of Aratus pisonii (Crustacea: Brachyura: Grapsidae)

Ingestion rates of zoeae of Aratus pisonii Milne Edwards (Brachyura: Grapsidae) were determined offering natural plankton-detritus mixtures in laboratory food selection experiments. The food mixtures were sampled in the Itamaracá estuary, north-eastern Brazil, and standardised to a size range of 50–200 μm. Zoeae ingested significant amounts of large centric diatoms (Coscinodiscus spp.), mangrove detritus, tintinnids (Favella ehrenbergi) and adult copepods during feeding experiments. Diatoms were positively selected by A. pisonii zoeae in all three experiments, with ingestion rates of 3.3–21.3 cells zoea⁻¹ day⁻¹. Detritus particles were always more abundant than phytoplankton and zooplankton in the particle size spectrum offered. Detritus was ingested in two of three experiments, with ingestion rates of up to 34.1 particles zoea⁻¹ day⁻¹, being the most important food item during one experiment. Adult copepods (up to 1.8 ind. zoea⁻¹ day⁻¹) and tintinnids (up to 0.4 ind. zoea⁻¹ day⁻¹) were ingested by A. pisonii zoeae during one experiment each. In spite of a wide range of zoeal density, food particle composition, and density, zoeae of A. pisonii displayed a consistent pattern of food selectivity. This hints at a consistent sensory and behavioural mechanism related to capture and handling of food particles, that most likely also affects larval feeding under natural conditions. Although detritus showed to be quantitatively ingested under estuarine conditions, zoeae of A. pisonii preferred large diatoms and ingested zooplankton only occasionally.     

Functional anatomy of the female reproductive systems of two spider crabs (Decapoda,Majoidea)

To better understand the mating systems of majoid crabs, we studied the functional anatomy of the female reproductive systems of the spider crabs Leurocyclus tuberculosus and Libinia spinosa, comparing them with those of other Majoidea. Adult females were measured and dissected, and their reproductive systems described macroscopically and histologically. In females of both species, the seminal receptacles are paired globular structures of ecto‐mesodermal origin. The mesoderm‐derived region is lined by a stratified epithelium. The anchoring, proliferative, and secretory strata are clearly recognizable . The ectoderm‐derived region is lined by a simple cylindrical epithelium underlying a cuticle that increases in thickness toward the vagina. The transition between the ectoderm and mesoderm‐derived regions is abrupt, with differences between the studied species: Li. spinosa has a “velum,” whereas Le. tuberculosus presents prominent “folds.” In both species, the position in which the oviduct is connected to the seminal receptacles is intermediate between the dorsal and ventral types previously described in other eubrachyurans. The seminal receptacles of the studied species show four different conditions, which can be distinguished macroscopically based on their shape and amount of sperm stored. We compare our data with those from other Majoidea in an attempt to determine whether the morphology of the seminal receptacles is related to different mating strategies or behaviors.     

Setal morphology of grooming appendages in the spider crab,Libinia dubia

In crustaceans, grooming behaviors decrease fouling by removing debris from the exoskeleton and body structures; these grooming behaviors improve respiration, sensory reception, movement, and reproduction. Setal morphologies of the following grooming appendages in the decapod crustacean spider crab Libinia dubia are examined including the first pereiopod (cheliped), first, second, and third maxillipeds (mouthparts), and first, second, and third epipods (internal extensions of the maxillipeds). The objective of this study was to describe setal morphologies of these grooming appendages and to elucidate possible functions and efficiencies of setal structures. Spider crabs are hypothesized to have elaborate setal morphologies, mainly for cleaning specialized decorating setae as well as for cleaning inside the gill chamber, which has a higher likelihood of becoming fouled compared to other decapods such as shrimps. Fourteen setal types are documented and included several varieties of serrate and pappose setae as well as simple setae, cuspidate setae, papposerrate setae, and canoe setae. Maxillipodal epipods in the gill chamber are free of fouling, suggesting the setation on the third maxilliped protopod has an efficient functional morphology in removing debris before water enters the gill chamber. Serrate setae may function for detangling and separating structures whereas pappose setae may function for fine detailed grooming. The cheliped is the only grooming appendage that can reach decorating setae and it contains only pappose setae; thus decorating setae is not likely groomed in a manner that would greatly decrease fouling. J. Morphol. 277:1045–1061, 2016. © 2016 Wiley Periodicals, Inc.     

A meta-analysis of the ecological and evolutionary drivers of metabolic rates in brachyuran crabs

Metabolic rates provide an estimate of the cost of living for different organisms that can readily be compared across species to provide an estimate of their relative requirements for survival. As such, metabolic rates have been measured for decades on a wide range of organisms. Here, we review published estimates of metabolic rates for brachyuran crabs, a ubiquitous and ecologically and economically important group of consumers. Consistent with ecological theory and results in many other groups of animals, and after controlling for phylogenetic relationships, crab metabolic rates scale with body mass with a scaling exponent of 0.65. Similarly, as with other groups of poikilotherms, crab metabolic rates increase strongly with temperature, with a Q₁₀ of 1.26. Additionally, we found that metabolic rates were correlated with ecological niche, varying with both the diet strategy and the habitat occupied. These results help clarify the relative risk to crabs from environmental changes that impose metabolic stress, including climate change and the proliferation of hypoxic zones.     

The crustacean ichnofossil Palaxius associated with callianassid body fossils in an Eocene methane-seep limestone, Humptulips Formation, Olympic Peninsula, Washington

Crustacean microcoprolites are preserved along with crustacean megafossils in an Eocene limestone within the Humptulips Formation in Grays Harbor County, Washington. The limestone formed at a methane seep, as revealed by early diagenetic carbonate phases resembling those of other seep limestones, δ¹³C_carbonate values as low as −27‰, and lipid biomarkers of prokaryotes involved in anaerobic oxidation of methane with δ¹³C values as low as −110‰. Recognizable crustacean megafossils are chiefly isolated chelipeds, akin to those of callianassid shrimp. The microcoprolites are pierced by ten longitudinal canals with crescent-shaped outlines in cross-section, arranged in two symmetrical groups. The symmetry plan and number of canals of the microcoprolites identify the Humptulips ichnospecies as Palaxius habanensis Brönnimann & Norton. The occurrence of decapod fossils along with microcoprolites suggests that callianassid shrimp were the producers of the Palaxius , supporting earlier work that attributed this ichnogenus to callianassids.     

Eusociality Shapes Convergent Patterns of Molecular Evolution across Mitochondrial Genomes of Snapping Shrimps

Eusociality is a highly conspicuous and ecologically impactful behavioral syndrome that has evolved independently across multiple animal lineages. So far, comparative genomic analyses of advanced sociality have been mostly limited to insects. Here, we study the only clade of animals known to exhibit eusociality in the marine realm—lineages of socially diverse snapping shrimps in the genus Synalpheus. To investigate the molecular impact of sociality, we assembled the mitochondrial genomes of eight Synalpheus species that represent three independent origins of eusociality and analyzed patterns of molecular evolution in protein-coding genes. Synonymous substitution rates are lower and potential signals of relaxed purifying selection are higher in eusocial relative to noneusocial taxa. Our results suggest that mitochondrial genome evolution was shaped by eusociality-linked traits—extended generation times and reduced effective population sizes that are hallmarks of advanced animal societies. This is the first direct evidence of eusociality impacting genome evolution in marine taxa. Our results also strongly support the idea that eusociality can shape genome evolution through profound changes in life history and demography.