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     

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     

Global diversity of cladocerans (Cladocera; Crustacea) in freshwater

Cladocera is a primarily-freshwater monophyletic group, an important component of the microcrustacean zooplankton. They inhabit most types of continental fresh and saline water habitats, occurring more abundantly in both temporary and permanent stagnant waters. Cladocera is an ancient group of Palaeozoic origin. About 620 species are currently known, but we estimate that the real number of species is 2–4 times higher. A number of currently-recognised widespread species can be expected to harbour extensive cryptic diversity. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of copepods (Crustacea: Copepoda) in freshwater

The zoogeographic distributions of the 2,814 species of copepods reported from freshwater are analysed. Faunal diversity is compared between zoogeographic regions: the Palaearctic region has more than double the species richness of the next most diverse region, the Neotropical. Historical factors affecting levels of diversity are identified. More than 90% of all freshwater copepods are endemic to a single-zoogeographic region and endemic genera occur in all regions except Antarctica. Species that are not endemic to a single region include the highly vagile and cosmopolitan species occurring in four or more regions. The greatest faunal connectivity, as identified by Sørensen’s Index, is between Palaearctic and Nearctic regions, and identifies the Holarctic taxa. Key human-related issues, such as the role of copepods as vectors for human parasites and the losses caused by parasitic copepods in commercial aquaculture, are mentioned.     

Global diversity of ostracods (Ostracoda,Crustacea) in freshwater

There are close to 2,000 subjective species and about 200 genera of Recent non-marine Ostracoda. Together, Cyprididae (1,000 spp.) and Candonidae (c. 550 spp.) represent more than 75% of the extant specific diversity; the remaining 11 families comprise the other 25% of the species. The Palaearctic region has the highest absolute non-marine ostracod diversity, followed by the Afrotropical. The Australian region has the highest relative endemicity. About 90% of the species and 60% of the genera occur in one zoogeographical region only. This means that all the biological mechanisms which lead up to efficient dispersal and which are present in at least part of the non-marine Ostracoda (e.g. brooding, drought-resistant eggs, parthenogenesis) have not induced common cosmopolitan distributions in ostracods. Several habitats are hotspots for ostracod diversity and endemicity. For example, it appears that the ancient lakes hold up to 25% of the total ostracod diversity. Other speciation-prone habitats are groundwater, temporary pools and Australian salt lakes; in the latter two instances, cladogenesis has often been paralleled by gigantism. The present ostracod diversity results from 9 to 12 separate invasions of the non-marine habitat, starting about 400 Myr ago. Genetic diversity can be very different in different species, mostly, but not always, related to reproductive mode. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Peracarid composition,diversity and species richness in the area of the Northeast Water polynya,East Greenland (Crustacea,Malacostraca)

During the ARK XI-2 expedition with RV Polarstern in September/October 1995, a transect of epibenthic sledge (EBS) samples was taken in the area of the Northeast Water Polynya off the Greenland coast, from the shelf down into the deep sea. A total of 85,304 specimens of Peracarida were collected at seven stations. These individuals comprised 45 families, 103 genera and 180 species. With regard to abundance, Cumacea occurred with highest numbers, 31,269, followed by Isopoda, Amphipoda, Mysidacea and Tanaidacea. Species richness was highest in Amphipoda with 94 species, followed by Isopoda with 43 species, Cumacea with 20 species, Tanaidacea with 15 and Mysidacea with 8 species. Species richness was highest at the shallowest station 37-016 and lowest at the deepest station 37-021, whereas the opposite pattern was found for abundance. Diversity and eveness were highest at the southernmost station and lowest at the deepest station. Amphipoda occurred more frequently at the shallower stations, while Cumacea were very frequent at the deepest station. Numbers of species were lowest for Cumacea at the deepest station, while Amphipoda and Isopoda generally occurred with high species richness at all stations. On the basis of the species composition stations were compared.     

Global diversity of shrimps (Crustacea: Decapoda: Caridea) in freshwater

Freshwater caridean shrimps account for approximately a quarter of all described Caridea, numerically dominated by the Atyidae and Palaemonidae. With the exception of Antarctica, freshwater shrimp are present in all biogeographical regions. However, the Oriental region harbours the majority of species, whilst the Nearctic and western Palaearctic are very species-poor. Many species are important components of subsistence fisheries, whilst the Giant River Prawn forms the basis of an extensive aquaculture industry. A total of 13 species are threatened or endangered, with one species formally extinct. Guest editors: E. V. Balian, C. Lévêque, H. Segers and K. Martens Freshwater Animal Diversity Assessment     

Global diversity of amphipods (Amphipoda; Crustacea) in freshwater

Amphipods are brooding peracaridan crustaceans whose young undergo direct development, with no independent larval dispersal stage. Most species are epibenthic, benthic, or subterranean. There are some 1,870 amphipod species and subspecies recognized from fresh or inland waters worldwide at the end of 2005. This accounts for 20% of the total known amphipod diversity. The actual diversity may still be several-fold. Amphipods are most abundant in cool and temperate environments; they are particularly diversified in subterranean environments and in running waters (fragmented habitats), and in temperate ancient lakes, but are notably rare in the tropics. Of the described freshwater taxa 70% are Palearctic, 13% Nearctic, 7% Neotropical, 6% Australasian and 3% Afrotropical. Approximately 45% of the taxa are subterranean; subterranean diversity is highest in the karst landscapes of Central and Southern Europe (e.g., Niphargidae), North America (Crangonyctidae), and Australia (Paramelitidae). The majority of Palearctic epigean amphipods are in the superfamily Gammaroidea, whereas talitroid amphipods (Hyalella) account for all Neotropic and much of the Nearctic epigean fauna. Major concentrations of endemic species diversity occur in Southern Europe, Lake Baikal, the Ponto-Caspian basin, Southern Australia (including Tasmania), and the south-eastern USA. Endemic family diversity is similarly centered in the Western Palearctic and Lake Baikal. Freshwater amphipods are greatly polyphyletic, continental invasions have taken place repeatedly in different time frames and regions of the world. In the recent decades, human mediated invasions of Ponto-Caspian amphipods have had great impacts on European fluvial ecosystems. Guest editors: E. V. Balian, C. Lévêque, H. Segers and K. Martens Freshwater Animal Diversity Assessment     

Global diversity of Isopod crustaceans (Crustacea; Isopoda) in freshwater

The isopod crustaceans are diverse both morphologically and in described species numbers. Nearly 950 described species (∼9% of all isopods) live in continental waters, and possibly 1,400 species remain undescribed. The high frequency of cryptic species suggests that these figures are underestimates. Several major freshwater taxa have ancient biogeographic patterns dating from the division of the continents into Laurasia (Asellidae, Stenasellidae) and Gondwana (Phreatoicidea, Protojaniridae and Heterias). The suborder Asellota has the most described freshwater species, mostly in the families Asellidae and Stenasellidae. The suborder Phreatoicidea has the largest number of endemic genera. Other primary freshwater taxa have small numbers of described species, although more species are being discovered, especially in the southern hemisphere. The Oniscidea, although primarily terrestrial, has a small number of freshwater species. A diverse group of more derived isopods, the ‘Flabellifera’ sensu lato has regionally important species richness, such as in the Amazon River. These taxa are transitional between marine and freshwater realms and represent multiple colonisations of continental habitats. Most species of freshwater isopods species and many genera are narrow range endemics. This endemism ensures that human demand for fresh water will place these isopods at an increasing risk of extinction, as has already happened in a few documented cases. 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     

Global diversity of fish (Pisces) in freshwater

The precise number of extant fish species remains to be determined. About 28,900 species were listed in FishBase in 2005, but some experts feel that the final total may be considerably higher. Freshwater fishes comprise until now almost 13,000 species (and 2,513 genera) (including only freshwater and strictly peripheral species), or about 15,000 if all species occurring from fresh to brackishwaters are included. Noteworthy is the fact that the estimated 13,000 strictly freshwater fish species live in lakes and rivers that cover only 1% of the earth’s surface, while the remaining 16,000 species live in salt water covering a full 70%. While freshwater species belong to some 170 families (or 207 if peripheral species are also considered), the bulk of species occur in a relatively few groups: the Characiformes, Cypriniformes, Siluriformes, and Gymnotiformes, the Perciformes (noteably the family Cichlidae), and the Cyprinodontiformes. Biogeographically the distribution of strictly freshwater species and genera are, respectively 4,035 species (705 genera) in the Neotropical region, 2,938 (390 genera) in the Afrotropical, 2,345 (440 genera) in the Oriental, 1,844 (380 genera) in the Palaearctic, 1,411 (298 genera) in the Nearctic, and 261 (94 genera) in the Australian. For each continent, the main characteristics of the ichthyofauna are briefly outlined. At this continental scale, ichthyologists have also attempted to identify ichthyological ‘‘provinces’’ that are regions with a distinctive evolutionary history and hence more or less characteristic biota at the species level. Ichthyoregions are currently identified in each continent, except for Asia. An exceptionally high faunal diversity occurs in ancient lakes, where one of the most noteworthy features is the existence of radiations of species that apparently result from intra-lacustrine speciation. Numerous fish-species flocks have been identified in various ancient lakes that are exceptional natural sites for the study of speciation. The major threats to fish biodiversity are intense and have been relatively well documented: overexploitation, flow modification, destruction of habitats, invasion by exotic species, pollution including the worldwide phenomena of eutrophication and sedimentation, all of which are interacting. 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     

Global diversity of nematodes (Nematoda) in freshwater

Despite free-living nematodes being present in all types of limnetic habitats including unfavorable conditions that exclude many other meiobenthic invertebrates, they received less attention than marine and terrestrial forms. Two-fifths of the nematode families, one-fifth of the nearly 1800 genera and only 7% of the about 27,000 nominal species are recorded from freshwater habitats. The Dorylaimia are the most successful in freshwater habitats with nearly two-thirds of all known freshwater nematodes belonging to this subclass. Members of the subclass Enoplia are principally marine though include some exclusively freshwater taxa with extreme endemism. The subclass Chromadoria includes half of the freshwater nematode families and members of the Monhysterida and Plectida are among the most widely reported freshwater nematodes. Studies on freshwater nematodes show extreme regional bias; those from the southern hemisphere are extremely underrepresented, especially compared to European freshwater bodies. The majority of records are from a single biogeographic region. Discussion on nematode endemism is largely premature since apart from Lake Baikal, the nematofauna of ancient lakes as centers of speciation is limited and recent discoveries show high nematode abundance and diversity in cryptic freshwater bodies, underground calcrete formations and stromatolite pools potentially with a high number of new taxa. Guest editors: E.V. Balian, C. Lèvêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of snakes (Serpentes; Reptilia) in freshwater

A list of the snake species inhabiting freshwaters is provided. It includes 153 species, which represents about 5% of all known snakes. These freshwater snakes belong to 44 genera distributed among the families Acrochordidae, Boidae, Colubridae, Elapidae, Homalopsidae and Viperidae. The highest diversities in freshwater snakes are found in the Oriental (64 species) and Neotropical (39 species) Regions. Conservation actions are needed for several overcollected species with a limited distribution. Guest editors: E. V. Balian, C. Lévêque, H. Segers, & K. Martens Freshwater Animal Diversity Assessment     

A replacement name for Dayus Gerken, 2001 (Crustacea,Peracarida, Cumacea), preoccupied by Dayus Mahmood, 1967 (Insecta,Hemiptera, Cicadellidae)

A replacement name is proposed for genus Dayus Gerken, 2001 (Crustacea: Peracarida: Cumacea), preoccupied by Dayus Mahmood, 1967 (Insecta: Hemiptera: Cicadellidae). The following changes are proposed: Jennidayus new replacement name = Dayus Gerken, 2001 (nec Mahmood 1967); Jennidayus pharocheradus (Gerken, 2001), comb. n. = Dayus pharocheradus Gerken, 2001; Jennidayus acanthus (Gerken, 2001), comb. n. = Dayus acanthus Gerken, 2001; Jennidayus makrokolosus (Gerken, 2001), comb. n. = Dayus makrokolosus Gerken, 2001.     

Global diversity of mammals (Mammalia) in freshwater

Species that are dependant on, or adapted to, freshwater environments are found in almost all mammalian orders, and two orders, the Cetacea and the Sirenia, are strictly aquatic and include some freshwater-dependant species. Overall, the aquatic and freshwater-dependant species represent around 70 of the more than 1,200 living or recent genera of mammals, and occur in all continents except Antarctica. They include some of the most endangered species of mammals, and several have gone extinct or become critically endangered in recent decades. One of the main threats is habitat loss or degradation. This chapter provides an overview of the freshwater species within each order of mammals, their evolutionary history, their relations to humans and their conservation status. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Global diversity of nemerteans (Nemertea) in freshwater

Most ribborn worms (phylum Nemertea) are marine and only 22 of the currently named around 1,200 species are known from freshwater habitats (mainly lakes/ponds). They are all free-living benthic forms found in all continents except Antarctica. The vast majority of species have been recorded from the Palearctic region, but this may reflect sampling efforts rather than biogeography. Guest editors: E.V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of mysids (Crustacea-Mysida) in freshwater

In this article we present a biogeographical assessment of species diversity within the Mysida (Crustacea: Malacostraca: Peracarida) from inland waters. Inland species represent 6.7% (72 species) of mysid diversity. These species represent three of the four families within the Mysida (Lepidomysidae, Stygiomysidae, and Mysidae) and are concentrated in the Palaearctic and Neotropical regions. The inland mysid species distributional patterns can be explained by four main groups representing different freshwater invasion routes: (1) Subterranean Tethyan relicts (24 spp.); (2) Autochthonous Ponto-Caspian endemics (20 spp.); (3) Mysis spp. ‘Glacial Relicts’ (8 spp.); and (4) Euryhaline estuarine species (20 spp.). The center of inland mysid species diversity is the Ponto-Caspian region, containing 24 species, a large portion of which are the results of a radiation in the genus Paramysis. 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 and K. Martens Freshwater Animal Diversity Assessment     

Global diversity of hymenopterans (Hymenoptera; Insecta) in freshwater

A summary of the known species of aquatic Hymenoptera is presented. In total, 150 species from 11 families are recognized as aquatic (0.13% of the total described species). This number is likely an underestimate, because of the high percentage of undescribed species and a lack of knowledge of host range and behaviour for most species. All aquatic Hymenoptera are parasitoids. Many species have relatively dense pubescence to trap air and elongate, tarsal claws to grip the substrate, when underwater. Most species are known from the Holarctic and Oriental regions, but this is likely an artefact caused by lack of knowledge of other regions of the world. Aquatic behaviour has evolved independently at least 50 times within the order. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of water mites (Acari,Hydrachnidia; Arachnida) in freshwater

The Hydrachnidia (water mites) represent the most important group of the Arachnida in fresh water. Over 6,000 species have been described worldwide, representing 57 families, 81 subfamilies and more than 400 genera. The article analyzes extant water mite diversity and biogeography. Data on distribution and species richness of water mites are substantial but still far from complete. Many parts of the world are poorly investigated, Oriental and Afrotropical regions in particular. Moreover, information among different freshwater habitats is unbalanced with springs and interstitial waters disproportionately unrepresented. Therefore, more than 10,000 species could be reasonably expected to occur in inland waters worldwide. Based on available information, the Palaearctic region represents one of the better investigated areas with the highest number of species recorded (1,642 species). More than 1,000 species have been recorded in each of the Neotropical (1,305 species) and Nearctic regions (1,025 species). Known species richness is lower in Afrotropical (787 species) and Australasian (694 species) regions, and lowest in the Oriental region (554 species). The total number of genera is not correlated with species richness and is distinctly higher in the Neotropical (164 genera); genus richness is similar in the Palaearctic, Nearctic and Australasian regions (128–131 genera) and is lower in the Afrotropical and Oriental regions with 110 and 94 genera, respectively. A mean number of about three genera per family occur in the Palaeartic, Nearctic and Oriental while an average of more than four genera characterizes the families of Australasian and Afrotropical regions and more than five genera those of the Neotropical. Australasian fauna is also characterized by the highest percentage of endemic genera (62%), followed by Neotropical (50.6%) and Afrotropical (47.2%) regions. Lower values are recorded for the Palaearctic (26.9%), Oriental (24.4%) and Nearctic (21.4%). The Palaearctic and Nearctic have the highest faunistic similarity, some minor affinities are also evident for the generic diversification of Holarctic and Oriental families. The faunas of Southern Hemisphere bioregions are more distinct and characterized by the presence of ancient Gondwanan clades with a regional diversification particularly evident in the Neotropics and Australasia. This scenario of water mite diversity and distribution reflect the basic vicariance pattern, isolation, phylogenetic diversification, recent climatic vicissitudes and episodes of dispersal between adjacent land masses together with extant ecological factors can be evoked to explain distribution patterns at a global scale. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Molecular insights into Cumacean family relationships (Crustacea, Cumacea)

Cumaceans are a diverse order of small, benthic marine crustaceans. Phylogenetic hypotheses for the eight currently recognized cumacean families have not been formally proposed. However, based on external morphological traits and Linnean classification, a few conflicting hypotheses of relatedness have been proposed. Family definitions rely on morphological characters that often overlap and diagnoses are based on a combination of non-unique characters. Morphological analysis does not provide a well-resolved phylogeny. In the present study, we use amino acid sequences from the mitochondrial cytochrome oxidase I gene to produce a molecular phylogenetic hypothesis for the families of Cumacea. Phylogenetic analyses at the amino acid level were performed under Bayesian, likelihood, and parsimony methods. Results strongly suggest that families lacking an articulated telson form a monophyletic group. This pleotelson clade, composed of the families Bodotriidae, Leuconidae, and Nannastacidae, is the most derived within the Cumacea. Within this group, the Bodotriidae resolve paraphyletically, with Leuconidae and Nannastacidae embedded within it. Comparison of the molecular phylogeny with that based on morphology suggests that many "diagnostic" characters are homoplasious.