Phylogeny, biogeography and a new taxonomy for the Gecarcinucoidea Rathbun, 1904 (Decapoda: Brachyura)

Phylogenetic relationships of gecarcinucoid freshwater crabs were investigated, based on morphology of the male second gonopod. In addition, a comparison of sequences from the mitochondrial large subunit rRNA gene helped to resolve the phylogeny of this group and relationships to other Old World freshwater crabs. As a result, we recognise two sister groups within the Gecarcinucoidea, the African Deckeniidae and the Asian Gecarcinucidae. Deckeniidae includes three monophyletic clades, the Deckeniinae in East Africa and on the Seychelles, the West African Globonautinae and the Malagasy Hydrothelphusinae. Gecarcinucidae comprises two sister groups, the Gecarcinucinae with representatives in Sri Lanka, India and southeast Asia, and the Parathelphusinae in India, southeast Asia, the Sundaic Islands and Australia. Interpretation of our phylogenetic results leads us to propose a new biogeographic hypothesis for the Gecarcinucoidea. Most likely, the gecarcinucoid freshwater crabs have an African origin; their distribution can be explained by successive events of dispersal. This model can be correlated with palaeogeographical and palaeoclimatological data for the Cenozoic, suggesting a gecarcinucoid dispersal to Asia via the “Lemurian Stepping-Stones”, a chain of islands in the West-Indian Ocean that were emergent in times of low sea levels during the Oligocene.     

Biodiversity of brachyuran crabs (Crustacea: Decapoda) from non-consolidated sublittoral bottom on the northern coast of São Paulo State, Brazil

The brachyuran community of the coast of São Paulo State is represented by about 188 species of crabs inhabiting different kinds of coastal marine environments. The biodiversity of brachyurans found on non-consolidated sublittoral bottom was investigated. The Ubatuba region (Ubatumirim, Ubatuba and Mar Virado bays, Couves and Mar Virado Islands, offshore region) was sampled for 3 years (1998–2000), at depths of 2–40 m. All sampling was performed using a fishing boat equipped with two double-rig nets. We collected 79 brachyuran species representing 9 superfamilies (4 Dromioidea, 1 Homoloidea, 2 Calappoidea, 5 Leucosioidea, 20 Majoidea, 7 Parthenopoidea, 17 Portunoidea, 18 Xanthoidea, and 5 Pinnotheroidea) and 41 genera. Ubatuba bay showed the greatest species richness with 50 species, followed by Ubatumirim with 45 and Mar Virado with 29. The number of species collected represents about 57% of the known species of crabs already reported for the shore of São Paulo State. It is worth noticing that this percentage is restricted only to non-consolidated sublittoral bottom. This fact indicates a great biodiversity of the habitat in this studied region, probably one to the diversity of habitat types present in the bays.     

Relative growth and onset of morphological sexual maturity of the freshwater crab Sylviocarcinus pictus in a river of the Caatinga of northeastern Brazil

The aim of this study was to investigate the relative growth and onset of morphological sexual maturity of the freshwater crab Sylviocarcinus pictus. Specimens were collected every month from October 2013 to September 2014, at night, on a stretch of the river Guaribas, Piauí, Brazil. Crabs were sexed and their carapace width (CW, independent variable), carapace length (CL), cheliped propodus length (PL) and height (PH), gonopod length (GL), and abdomen width (AW) (dependent variables) were measured. These measurements were related to characterise relative growth and possible sex differences. On average males were larger than females (p = 0.0001). Size at the onset of morphological sexual maturity was defined by relating CL vs. PL for males (30.82 mm) and CL vs. AW for females (28.63 mm). These are considered secondary sexual characters and reflect initial size at morphological sexual maturity with greater precision. The differential cheliped growth of males may be related to courting and disputes with other males, while the allometric growth of the abdomen of females indicates increased probability of reproductive success.     

Polymorphic nuclear microsatellite loci for studies of brown crab, Cancer pagurus L

Twelve polymorphic microsatellite DNA loci were isolated from the brown crab, Cancer pagurus L., by construction of microsatellite-enriched genomic libraries. Genotyping of 40 individuals from Norfolk (UK) revealed variable levels of locus polymorphism with an average of 7.75 alleles per locus (range 2-22). The observed and expected heterozygosities per locus ranged from 0.025 to 0.868 and from 0.025 to 0.947, respectively. No evidence of linkage disequilibrium was detected between pairs of loci and genotype proportions at all loci conformed to Hardy-Weinberg equilibrium expectations. The microsatellite loci developed constitute a suite of genetic markers applicable to numerous areas of C. pagurus research.     

Behavioural and respiratory response of the shallow-water hermit crab Pagurus cuanensis to hydrostatic pressure and temperature

The evolutionary history of the Anomura has long been controversially discussed. One aspect that has received little attention is the dissimilarity in physiological tolerances of the related families Paguridae and Lithodidae to environmental conditions, and how this may have determined the divergence and radiation of the families into different distribution ranges, in particular with regard to the limited penetration of the deep sea by the Paguridae. This study investigates the physiological tolerances of the temperate shallow-water hermit crab, Pagurus cuanensis, to various temperature (5, 10, 15, 20 °C) and pressure regimes (1 to 100 atm) by measuring the standard metabolic rate (SMR) and behavioural changes. SMR was primarily affected by temperature, with a notably low rate at 5 °C throughout all pressures. Behaviour was affected by pressure, with an increase in pressure from 50 to 100 atmospheres (atm) resulting in reduced activity. It is suggested that this species can tolerate hydrostatic pressures greater than those found in its natural bathymetric range. It is discussed that a lack of physiological cold tolerance and ecological factors, such as the need to find gastropod shells for protection, are the principal restrictions maintaining P. cuanensis to a maximum depth of approximately 250 m. We hypothesize that temperate shallow-water invertebrates could indeed be able to penetrate greater depths as continental shelf waters warm up in the course of global climate change.     

Global diversity of crabs (Crustacea: Decapoda: Brachyura) in freshwater

An assessment of the global freshwater crab diversity is presented. A total of 1,476 species in 14 families are currently known from all zoogeographical regions (except Antarctica), including 1,306 species in eight exclusively freshwater families (Pseudothelphusidae, Trichodactylidae, Potamonautidae, Deckeniidae, Platythelphusidae, Potamidae, Gecarcinucidae and Parathelphusidae). Estimates of true freshwater crab diversity including likely numbers of undescribed taxa suggest that the field remains largely in a “discovery” phase. Main ideas on the origins, diversification, and phylogeny of true freshwater crabs are briefly discussed. The economic importance of freshwater crabs is also highlighted. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

The Freshwater Animal Diversity Assessment: an overview of the results

We present a summary of the results included in the different treatments in this volume. The diversity and distribution of vertebrates, insects, crustaceans, molluscs and a suite of minor phyla is compared and commented upon. Whereas the available data on vertebrates and some emblematic invertebrate groups such as Odonata (dragonflies and damselflies) allow for a credible assessment, data are deficient for many other groups. This is owing to knowledge gaps, both in geographical coverage of available data and/or lack of taxonomic information. These gaps need to be addressed urgently, either by liberating date from inaccessible repositories or by fostering taxonomic research. A similar effort is required to compile environmental and ecological information in order to enable cross-linking and analysis of these complementary data sets. Only in this way will it be possible to analyse information on freshwater biodiversity for sustainable management and conservation of the world’s freshwater resources. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Biogeography of the Monimiaceae (Laurales): a role for East Gondwana and long‐distance dispersal,but not West Gondwana

Aim The biogeography of the tropical plant family Monimiaceae has long been thought to reflect the break‐up of West and East Gondwana, followed by limited transoceanic dispersal. Location Southern Hemisphere, with fossils in East and West Gondwana. Methods We use phylogenetic analysis of DNA sequences from 67 of the c. 200 species, representing 26 of the 28 genera of Monimiaceae, and a Bayesian relaxed clock model with fossil prior constraints to estimate species relationships and divergence times. Likelihood optimization is used to infer switches between biogeographical regions on the highest likelihood tree. Results Peumus from Chile, Monimia from the Mascarenes and Palmeria from eastern Australia/New Guinea form a clade that is sister to all other Monimiaceae. The next‐deepest split is between the Sri Lankan Hortonia and the remaining genera. The African Monimiaceae, Xymalos monospora, then forms the sister clade to a polytomy of five clades: (I) Mollinedia and allies from South America; (II) Tambourissa and allies from Madagascar and the Mascarenes; (III) Hedycarya, Kibariopsis and Leviera from New Zealand, New Caledonia and Australia; (IV) Wilkiea, Kibara, Kairoa; and (V) Steganthera and allies, all from tropical Australasia. Main conclusions Tree topology, fossils, inferred divergence times and ances‐tral area reconstruction fit with the break‐up of East Gondwana having left a still discernible signature consisting of sister clades in Chile and Australia. There is no support for previous hypotheses that the break‐up of West Gondwana (Africa/South America) explains disjunctions in the Monimiaceae. The South American Mollinedia clade is only 28–16 Myr old, and appears to have arrived via trans‐Pacific dispersal from Australasia. The clade apparently spread in southern South America prior to the Andean orogeny, fitting with its first‐diverging lineage (Hennecartia) having a southern‐temperate range. The crown ages of the other major clades (II–V) range from 20 to 29 Ma, implying over‐water dispersal between Australia, New Caledonia, New Zealand, and across the Indian Ocean to Madagascar and the Mascarenes. The endemic genus Monimia on the Mascarenes provides an interesting example of an island lineage being much older than the islands on which it presently occurs.     

Global diversity of cumaceans &; tanaidaceans (Crustacea: Cumacea &; Tanaidacea) in freshwater

Cumacea and Tanaidacea are marginal groups in continental waters. Although many euryhaline species from both groups are found in estuaries and coastal lagoons, most occur only temporarily in non-marine habitats, appearing unable to form stable populations there. A total of 21 genuinely non-marine cumaceans are known, mostly concentrated in the Ponto-Caspian region, and only four tanaids have been reported from non-marine environments. Most non-marine cumaceans (19 species) belong in the Pseudocumatidae and appear restricted to the Caspian Sea (with salinity up to 13‰) and its peripheral fluvial basins, including the northern, lower salinity zones of the Black Sea (Sea of Azov). There are nine Ponto-Caspian genera, all endemic to the region. Only two other taxa (in the family Nannastacidae) occur in areas free of any marine–water influence, in river basins in North and South America. Both seem able to survive in waters of raised salinity of the lower reaches of these fluvial systems; but neither has been recorded in full salinity marine environments. The only non-marine tanaidacean thus far known lives in a slightly brackish inland spring in Northern Australia. The genus includes a second species, from a brackish-water lake at the Bismarck Archipelago, tentatively included here as non-marine also. Two additional species of tanaidaceans have been reported from non-marine habitats but both also occur in the sea. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of spelaeogriphaceans & thermosbaenaceans (Crustacea; Spelaeogriphacea & Thermosbaenacea) in freshwater

Spelaeogriphaceans and thermosbaenaceans are two orders of eyeless, unpigmented peracarid crustaceans represented by very few species from subterranean waters. Spelaeogriphaceans occur only in continental waters, either running or still, in limestone or sandstone caves, or in calcrete aquifers. The four species known are limnic except one occurring in slightly brackish water loosely associated with an endorheic basin. The Thermosbaenacea are primarily marine, with only 18 species recorded in limnic conditions or in brackish inland waters whose salinity does not derive from dilution of seawater. They occur in limestone caves, the interstitial medium associated to alluvial deposits, or in thermo-mineral springs. Spelaeogriphaceans are found on the southern continents, in ancient cratons not affected by sea transgressions at least since the Early Cretaceous, when Gondwana started to break-up. The former integration of these terranes into Gondwana suggests that the penetration of spelaeogriphaceans in continental waters took place previous to the fragmentation of this super continent (starting ca. 140 Ma), and that their current distribution pattern was driven by continental drift. The distribution of the Thermosbaenacea matches precisely the area covered by the ancient Tethys Sea or its coastlines. They are most probably relicts of a once widespread shallow-water marine Tethyan fauna stranded in interstitial or crevicular groundwater during marine regressions. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Pleistocene speciation of freshwater crabs (Crustacea: Potamidae: Geothelphusa) from northern Taiwan and southern Ryukyus, as revealed by phylogenetic relationships

The phylogenetic relationship among freshwater crab species of Geothelphusa from northern Taiwan and the Yaeyama Group of islands (including Iriomote and Ishigaki) in the southern Ryukyus was studied using the mitochondrial genes 16S rRNA and COI. Our results support the hypothesis that speciation of Geothelphusa among these islands was the result of cyclic glaciations and interglaciations during the Pleistocene. Two main clades, one the Taiwan Group (containing several clades, including most Taiwanese Geothelphusa species except Geothelphusa miyazakii but including Geothelphusa minei from Yaeyama), was estimated to be separated from its sister group, the southern Ryukyus-northern Taiwan (SRN) clade (including G. miyazakii, Geothelphusa shokitai, Geothelphusa fulva and G. marginata from northern Taiwan, the Pinnacle Islands [=Diaoyutai Islands or Senkaku Islands] and Yaeyama) at about 5.3 million years ago (mya). G. shokitai was separated from others within the SRN clade at 2.4 mya, but was probably derived from G. miyazakii in northern Taiwan. The ancestor of G. miyazakii is hypothesised to have dispersed from ancestors in Yaeyama and then isolated at 2.0 mya during the Pleistocene interglaciations. This is similar to the speciation of G. minei in Yaeyama at 1.5 mya, except that its ancestors originated from north-eastern Taiwan. Four clades of freshwater crabs are present in the Fushan Botanical Garden, located in the mountainous area of north-eastern Taiwan, which might be due to the historical rearrangements of the drainage and proximity of the various river origins.     

Resource partitioning between sexes in the "unconventional" hermit crab, Calcinus tubularis

Together with Calcinus verrilli from Bermuda, the Mediterraneanhermit crab C. tubularis is unique in that it exhibits a sharpsexual dimorphism in resource use in which one sex, the male,occupies loose shells and the other, the female, occupies attachedtubes. Field surveys and laboratory experiments addressed twoissues that help understand male-female resource partitioningin this species. First, the value of shells as shelters differsbetween sexes. Shells furnish mobility to their inhabitants,but also greater opportunities to grow because they can providelarger size than can the tubes, whereas both mobility and largedimensions are crucial selective factors for the reproductiveoutcomes of males only. In fact, egg production seemed not tobe affected by females' sedentary life and the number of eggswas not related to the female size. Second, previous shelterexperience plays a role in reducing male-female competition.I found that individual crabs, once presented simultaneouslywith a shell and a tube, more likely selected the type of shelterthat they were collected in. Then, in male-female competitionexperiments, pairs composed of one crab found in a shell andone crab found in a tube and offered a shell and a tube in conjunctionoccupied the housing in accordance to the shelter previouslyoccupied without any influence of their sex or size. The questionremains as to how, why, and when such a sexual dimorphism inthe distribution of C. tubularis between microhabitats did occurduring a hermit crab's life.     

Cellular responses to increasing Cd concentrations in the freshwater crab,<Emphasis Type="Italic"> Potamonautes warreni</Emphasis>, harbouring microbial gill infestations

We investigated the uptake, transport, storage and defence mechanisms in the freshwater crab, Potamonautes warreni, harbouring microbial gill infestations and exposed to increasing chronic (0.2, 0.5, 1.0 mg l^–1) and acute (2.0 mg l^–1) cadmium (Cd) concentrations under controlled laboratory conditions over a period of 21 days. Transmission electron microscopy and X-ray microanalysis revealed that the microbial gill fauna was eliminated on exposure to 0.2 mg Cd²⁺ l^–1 and that Cd became increasingly adsorbed and incorporated into lamellar crystal deposits and permeated the cuticle of the gills of P. warreni. Degeneration of the apical membrane infoldings and vacuolation of epithelial cells occurred concurrently with pinocytosis, endocytosis and pronounced phagocytotic activity in the epithelia and haemal canal of the gills. Elevated Cd exposures (0.5 or 1.0 mg l^–1) resulted in the swelling and dissociation of mitochondrial outer membranes together with an increase in transport of Cu, Cl and S by haemocytes in the haemal canal to epithelial tissues depleted in these elements. Cd also accumulated in tightly coiled concentric membrane whorls in the haemal canal, whereas the highest concentrations of Cd were found within aggregates of lysosome-like bodies in cuticulin-secreting cells of the gill stem. Chronic exposure to Cd induced increased fatigue and mild uncoordinated motor activity. In contrast, at an acute exposure of 2.0 mg l^–1 over 48 h, P. warreni showed a time-specific rapid loss of motor function, although only mild cellular lesions occurred in the gill tissues. The significance of cellular changes in the gill epithelia and altered motor activity of P. warreni with increased waterborne Cd are discussed as potential biomarker responses in monitoring aquatic pollution.     

The Bohemo‐Iberian regional chronostratigraphical scale for the Ordovician System and palaeontological correlations within South Gondwana

The Bohemo‐Iberian regional scale for South Gondwana, involving the ‘Mediterranean Province’, comprises five regional stages (Arenigian, Oretanian, Dobrotivian, Berounian and Kralodvorian) plus the global Tremadocian and Hirnantian. The predominance of shallow‐water taxa in those high‐latitude faunas imposes serious difficulties for correlating the regional succession with the formal global chronostratigraphy because of the almost total absence of the key graptolites and conodonts defining the base of the standard series, stages and stage slices. Instead, the abundant benthic faunas (trilobites, brachiopods, molluscs, echinoderms) of South Gondwanan origin largely dominated in the area from the middle Darriwilian to the late Katian. The poleward faunal migration of originally Avalonian, Baltic, Laurentian and even Asiatic taxa during the Boda Event of global warming progressively ends with the endemicity in the region, where the ensuing benthic assemblages were severely affected by the Hirnantian glaciation. The regional scale significantly improves the precision of correlations between Ordovician strata from SW and central Europe, North Africa and a large part of the Middle East. An updated record of palaeontological data from areas where Mediterranean faunas remain practically unknown, or are still poorly investigated, is also included. Palaeobiogeographical relationships based on the distribution of faunas across South Gondwana are suggested as an improvement for positioning many territories in modern palaeogeographical reconstructions and offer a constructive approach to problems related to the pre‐Variscan and pre‐Alpine orogenic puzzles.     

A presumed spelaeogriphacean crustacean from an upper Barremian wetland (Las Hoyas; Lower Cretaceous; Central Spain)

Abstract: A third fossil attributable to the crustacean peracarid order Spelaeogriphacea is described from an Upper Barremian (125 Ma) lacustrine environment in Central Spain. Neither the new taxon, Spinogriphus ibericus gen. et sp. nov., nor the two already described fossil forms can be identified with certainty as crown‐group spelaeogriphaceans. We consider that Schram’s 1974 family Acadiocarididae represents stem‐lineage spelaeogriphaceans and should accommodate these fossil taxa that display very generalised peracaridan features and lack any conspicuous autapomorphies, except for a short carapace, undifferentiated pereiopods, foliaceous pleopods and a tail fan‐like (uropods + telson) caudal structure where the unsegmented uropodal endopod lacks annulation. The zoogeography of the Acadiocarididae is Laurasian in contrast to the modern, crown‐group spelaeogriphaceans (Spelaeogriphidae), which are limited to Gondwanan territories.     

The palaeoxylological record of Metapodocarpoxylon libanoticum (Edwards) Dupéron-Laudoueneix et Pons and the Gondwana Late Jurassic–Early Cretaceous continental biogeography

Aim Vertebrates, palynomorphs and leaf floras each give a different picture of continental biogeography of Northern Gondwana during the Middle Jurassic–Early Cretaceous interval. A new biogeographical marker is required to get a clearer picture. Location Northern part of the Gondwana during the Middle Jurassic–Early Cretaceous interval. Methods Comparisons and correlations of wood data from the literature and new material. Results We have selected Metapodocarpoxylon Dupéron‐Laudoueneix et Pons because it has a restricted distribution, temporally and geographically; it is a well‐defined Mesozoic fossil wood monospecific genus, and there are wide‐ranging data on its distribution. Conclusions Metapodocarpoxylon distribution draws a clear latitudinal belt extending from Lebanon westward to Peru. Climate being the main factor of plant distribution at a global scale, the Metapodocarpoxylon area probably underlines a climatic belt. This has several implications, for example, choosing among different Global Circulation Models or discussing dinosaur distribution.     

A morphological study on gills of a crab acclimated to fresh water

The gills of the fully euryhaline Chinese crab Eriocheir sinensis were studied by light and electron microscopy. In these Phyllobranchiates, the gills consist of a double row of lamellae extending laterally from a central shaft. Haemolymph flow pattern inside the gill is described and the existence of a complex secondary vascularization inside the platelets is reported. It is shown that important differences exist between the ultrastructure of the three anterior and the three posterior pairs of large gills. The epithelium of the posterior gills is much thicker and possesses an extensive elaboration of the plasma membranes in the form of infoldings, crypts and interdigitations, along which are packed numerous mitochondria. The presence of such a complex membrane system opening to the extracellular space and closely associated with mitochondria is common to all salt-transporting tissues. This study corroborates the idea that the posterior pairs of gills of Eriocheir sinensis are the only ones implicated in active Na+ uptake when the crab lives in dilute aquatic environment. The epithelium of anterior gills is much thinner and the cells poor in intracellular organelles. It seems to be involved essentially in respiration. Thus this work clearly corroborates the existence already suggested by physiological approach of a functional difference between the different pairs of E. sinensis branchiae with respect to their participation in the respiration and in the regulation of the blood ions content. Common to both types of gills is the presence of a lamellar septum separating the haemolymph space into two compartments. The part played by that structure in determining the pattern of haemolymph flow, together with periodic bridges forming pillars across the haemolymph space, is emphasized.     

Ionoregulatory and urinary responses to emersion in the mangrove crab Ucides cordatus and the intertidal crab Carcinus maenas

The mangrove crab Ucides cordatus showed a significant reduction in its output of isosmotic urine (to 60% of submerged rates) in humid, emersed conditions when in apparent water balance. A similar, but lesser, reduction was observed in the intertidal temperature species Carcinus maenas. Some of the decrease is effected by increased water withdrawal of an isosmotic fluid in the antennal gland (inulin urine to haemolymph concentration ratio=1.27) in Ucides but most is due to the reduced filtration rate which decreases from 3.41 to 2.19 ml·100 g^-1·day^-1 (in Carcinus from 7.37 to 5.88). In Carcinus, inulin urine to haemolymph concentration ratios are within the range 1.34–1.41 and show significant change on emersion. Comparisons of ion and inulin clearance ratios revealed interspecific differences in renal handling of Na⁺ and Cl^-. During emersion total Na⁺ efflux is markedly reduced in both species. Urinary Na⁺ losses are responsible for most of the efflux in Carcinus but represent only 50% of the total in Ucides. Significant Na⁺ uptake from interstitial water occurs in Ucides. REductions in ion and water loss appear to be mainly dependent on decreases in urine output (clearance rate). However, some released urine was found to accumulate in the branchial chambers in both species. Whether or not extrarenal reabsorption of ions from released urine occurs in the gill chambers in either crab species remains to be proved.Abbreviations CPM counts per minute - ECF extracellular fluid - k rate constant for inulin clearance - k ^Na rate constant for sodium efflux - J _out ^Na sodium efflux rate - Q _tot total radioactivity injected - SEM standard error of mean - SW sea water - 9-SW sea water, salinity 9 mg·ml^-1 (ppt) - 26-SW sea water, salinity 26 mg·ml^-1 (ppt) - U/B ratio of urine (U) to haemolymph (B) concentrations - V _c1 clearance rate - V _u urine output - V _a inulin space     

Encounter of lithodid crab <Emphasis Type=Italic>Paralomis birsteini</Emphasis> on the continental slope off Antarctica,sampled by ROV

A population of stone crab (Lithodidae) was encountered on the continental slope off Antarctica in the Bellingshausen Sea between 1,123 and 1,304 m water depths using the ROV-Isis during leg 166 of the RV James Clark Ross, in January 2007. Specimens were video recorded and one specimen was retrieved by ROV for morphological and molecular identification. Based on morphology and molecular data from the mitochondrial COI gene, this specimen identified as P. birsteini, Macpherson, 1988a. The significance of the molecular data and their implications for biogeography and evolution of lithodids in the Southern Ocean are briefly discussed.