Phylogenetic analysis of freshwater sponges provide evidence for endemism and radiation in ancient lakes

Morphologic and phylogenetic analysis of freshwater sponges endemic to lakes in Central Sulawesi, Siberia and South-East Europe is presented. We also analyzed several cosmopolitan sponge species from Eurasia and North America and included sponge sequences from public databases. In agreement with previous reports [Addis, J.S., Peterson, K.J., 2005. Phylogenetic relationships of freshwater sponges (Porifera, Spongillina) inferred from analyses of 18S rDNA, COI mtDNA, and ITS2 rDNA sequences. Zool. Scr. 34, 549-557], the metaniid sponge Corvomeyenia sp. was the most deeply branching species within a monophyletic lineage of the suborder Spongillina. Pachydictyum globosum (Malawispongiidae) and Nudospongilla vasta (Spongillidae), two morphologically quite distinct species from Sulawesi were found in a joint clade with Trochospongilla (Spongillidae) rendering Trochospongilla paraphyletic. Furthermore, Ochridaspongia sp., another Malawispongiidae, clustered far away from that clade, together with Ephydatia fluviatilis, making the latter family polyphyletic. The Lubomirskiidae endemic to Lake Baikal, Lubomirskia abietina, Baikalospongia bacillifera, B. intermedia, and Swartschewskia papyracea formed a well-supported clade that was most closely linked to the genus Ephydatia (99.9% identity over a total length of 2169 concatenated nucleotide positions). Our study indicates the frequent and independent origin of sponge species endemic to different freshwater ecosystems from a few cosmopolitan founder species. The highly specific primer sets newly developed here facilitate work on the molecular phylogeny and DNA barcoding of sponges.     

Ribosomal ITS Sequences Allow Resolution of Freshwater Sponge Phylogeny with Alignments Guided by Secondary Structure Prediction

Freshwater sponges include six extant families which belong to the suborder Spongillina (Porifera). The taxonomy of freshwater sponges is problematic and their phylogeny and evolution are not well understood. Sequences of the ribosomal internal transcribed spacers (ITS1 and ITS2) of 11 species from the family Lubomirskiidae, 13 species from the family Spongillidae, and 1 species from the family Potamolepidae were obtained to study the phylogenetic relationships between endemic and cosmopolitan freshwater sponges and the evolution of sponges in Lake Baikal. The present study is the first one where ITS1 sequences were successfully aligned using verified secondary structure models and, in combination with ITS2, used to infer relationships between the freshwater sponges. Phylogenetic trees inferred using maximum likelihood, neighbor-joining, and parsimony methods and Bayesian inference revealed that the endemic family Lubomirskiidae was monophyletic. Our results do not support the monophyly of Spongillidae because Lubomirskiidae formed a robust clade with E. muelleri, and Trochospongilla latouchiana formed a robust clade with the outgroup Echinospongilla brichardi (Potamolepidae). Within the cosmopolitan family Spongillidae the genera Radiospongilla and Eunapius were found to be monophyletic, while Ephydatia muelleri was basal to the family Lubomirskiidae. The genetic distances between Lubomirskiidae species being much lower than those between Spongillidae species are indicative of their relatively recent radiation from a common ancestor. These results indicated that rDNA spacers sequences can be useful in the study of phylogenetic relationships of and the identification of species of freshwater sponges.     

Distribution and ecology of freshwater sponges in Connecticut

A survey of Connecticut lakes and rivers revealed the presence of 7 species of freshwater sponge: Spongilla lacustris, Ephydatia muelleri, Eunapius fragilis, Anheteromeyenia ryderi, A. argyrosperma, Corvomeyenia carolinensis, and Corvospongilla novaeterrae in order of decreasing frequency of occurrence. Corvomeyenia carolinensis has not been reported previously beyond its type locality in South Carolina. In addition, microscleres of Spongilla lacustris, Anheteromeyenia-like megascleres, Ephydatia muelleri-like megascleres, and smooth megascleres (amphioxeas), which could not be assigned to a particular species, were found in surface sediments from lake cores. Spongilla lacustris inhabiting small rivers produced brown, thick-capsuled gemmules during the summer and yellow, thin-capsuled gemmules during the fall. The thick-capsuled gemmules, but not the thin-capsuled gemmules, are tolerant of desiccation; and populations of Spongilla lacustris and Ephydatia muelleri survived severe drying of their habitats during the summer.     

Food composition of Clarias gariepinus (= C. lazera) (Cypriniformes,Clariidae) in Lake Kinneret (Israel)

The feeding behaviour of the freshwater piscivore, Clarias gariepinus (C. lazera) (C & V 1840) was studied over two periods: 1973–1975 and 1981–1982, in Lake Kinneret (Israel). The total number of fish analysed was 264 and their sizes (SL) and weights varied between 238 and 830 mm (146 to 5728 g). More than fifty species of plants and animals from the plankton, benthos and nekton of Lake Kinneret were identified in the intestines of C. gariepinus. Preyed fish were the most abundant food component (81%) and constituted the highest biomass, with Mirogrex terraesanctae representing the majority (although other species were also found). The potential impact of piscivory in the Kinneret ecosystem is considered.     

Ancient lakes as hotspots of diversity: a morphological review of an endemic species flock of <Emphasis Type="Italic">Tylomelania</Emphasis> (Gastropoda: Cerithioidea: Pachychilidae) in the Malili lake system on Sulawesi,Indonesia

The viviparous freshwater gastropod Tylomelania (Caenogastropoda: Cerithioidea: Pachychilidae) endemic to the Indonesian island Sulawesi has radiated extensively in two ancient lake systems. We here present the first systematic species-level review of taxa in the five lakes of the Malili lake system, which contains the most diverse and best studied freshwater fauna on Sulawesi. Our results indicate a significantly higher diversity of Tylomelania in these lakes than previously perceived based on morphological evidence for delimiting the taxa. We describe nine new species, thus increasing the number of taxa known from the Malili lakes to 25. Tylomelania species are inhabiting all available substrates in the lakes, and the diversity of habitats is reflected in an unparalleled range of radula types in this closely related group. Several species show a high intraspecific variability in some characters, and their closer investigation will probably lead to the discovery of more cryptic species. As it is, this species flock on Sulawesi is among the largest freshwater mollusc radiations known. Since the Malili lake system also contains other large endemic species flocks of e.g. crustaceans and fishes, it is a major hotspot of freshwater biodiversity in Asia to become a conservation priority. Handling editor: K. Martens     

The taxonomic and ecological status of the environmentally restricted Spongillid species of North America. II. Anheteromeyenia biceps (Lindenschmidt, 1950)

The taxonomic validity, present distribution, and specific threats to the existence of the freshwater sponge, Anheteromeyenia biceps (Lindenschmidt, 1950) were investigated. The species, reported only from the type locality, Bessey Creek and Maple River, two streams flowing into Douglas Lake, Michigan, is relegated to synonomy with Ephydatia mülleri. Habitat data from Bessey Creek and Maple River, particularly physicochemical data, greatly extend the known environmental parameters of Heteromeyenia tubisperma and Ephydatia mülleri.     

Integrative taxonomy reveals too extensive lumping and a new species in the moss genus Amphidium (Bryophyta)

An integrative taxonomic approach, including molecular phylogenetic reconstructions based on plastid rps4-trnF and nuclear ITS sequences, statistical analysis of morphological-anatomical characters, and classical taxonomy, indicates that the reduction of 13 Amphidium species to three in a recent morphological revision represents a case of too extensive lumping. Instead, six Amphidium species can be distinguished based on molecular and morphological data, the widespread Amphidium lapponicum, A. mougeotii, and A. tortuosum, as well as the Macaronesian endemic A. curvipes, the North American endemic A. californicum, and a newly discovered species from Central Asia (southern Siberia and northern Mongolia), A. asiaticum sp. nov. Diagnostic morphological characters for all six species are discussed. The present data confirm that species diversity of Amphidium is highest in the Holarctic, where all six species occur.     

Contrasting levels of genetic differentiation among putative neutral microsatellite loci in Atlantic herring Clupea harengus populations and the implications for assessing stock structure

Porifera is a primarily marine phylum comprising more than 15,000 species. The successful and wide adaptive radiation of freshwater sponges (Haplosclerida: Spongillina) has resulted in the colonization of an extremely wide variety of habitats at all latitudes. Colonization is dated back to the Mesozoic, and the mono- or poly-phyletism of Spongillina, and the number of potential sponge invasions into freshwater is still under debate. Living freshwater sponges belong to 45 genera in six families for a total of 219 species. The highest diversity, at the scale of zoogeographic regions, is recorded from the Neotropical (65 species), Palaearctic (59 species), and Afrotropical regions (49 species). Endemic freshwater sponge species are 103 (47%) out of 219. All species belonging to the families Lubomirskiidae, Metschnikowiidae, and Malawispongiidae are endemic. Endemic species among the other families are 72% for Potamolepidae, 38% for Spongillidae, and 32% for Metaniidae. Data on some wide geographic areas are scattered and fragmentary if not almost completely lacking. Species richness is probably underestimated and doubtless destined to increase with further research. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Phylogenetic relationships of freshwater sponges (Porifera, Spongillina) inferred from analyses of 18S rDNA, COI mtDNA, and ITS2 rDNA sequences

The phylogenetic relationships of nine species of freshwater sponges, representing the families Spongillidae, Lubomirskiidae, and Metaniidae, were inferred from analyses of 18S rDNA, cytochrome oxidase subunit I (COI) mtDNA, and internal transcribed spacer 2 (ITS2) rDNA sequences. These species form a strongly supported monophyletic group within the Demospongiae, with the lithistid Vetulina stalactites as the sister taxon. Within the freshwater sponge clade, the basal taxon is not resolved. Depending upon the method of analysis and sequence, the metaniid species, Corvomeyenia sp., or the spongillid species, Trochospongilla pennsylvanica , emerges as the basal species. Among the remaining freshwater sponge species, the spongillids, Spongilla lacustris and Eunapius fragilis , form a sister group to a clade comprised of the spongillid species, Clypeatula cooperensis , Ephydatia fluviatilis , and Ephydatia muelleri , and the lubomirskiid species, Baikalospongia bacillifera and Lubomisrkia baicalensis . C. cooperensis is the sister taxon of E. fluvialitis , and E. muelleri is the sister taxon of ( B. bacillifera + L. baicalensis ). The family Spongillidae and the genus Ephydatia are thus paraphyletic with respect to the lubomirskiid species; Ephydatia is also paraphyletic to C. cooperensis . We suggest that C. cooperensis be transferred to the genus Ephydatia and that the family Lubomirskiidae be subsumed into the Spongillidae.     

Mesoscale investigations based on microsatellite analysis of the freshwater sponge <Emphasis Type="Italic">Ephydatia fluviatilis</Emphasis> in the River-Sieg system (Germany) reveal a genetic divergence

Freshwater sponges play a major role in freshwater ecological system as important filter-feeding organisms and bioindicators. There are only few data about their ecological diversity and population genetic structure available, though a deeper knowledge is needed to propose proper conservation and effective management. The aim of this study was to assess data on distribution patterns of freshwater sponges to study the connectivity of genotypes of Ephydatia fluviatilis in a river system. We sampled specimens from River-Sieg system (River Agger and River Sieg, Germany). We hypothesized that strong anthropogenic influence would cause a uniform distribution of population structures. The genetic structure of E. fluviatilis populations was analysed with a set of eleven microsatellite loci from seven locations in River-Sieg system. Besides of E. fluviatilis, three other species co-occurred (Ephydatia mülleri, Spongilla lacustris, Eunapius fragilis). In contrast to our hypothesis, we observed an overall correlation between genetic and geographic distances among populations of this sessile species, which follows a clear isolation-by-distance pattern. A significant microsatellite polymorphism and high levels of genetic divergence between populations (F_ST) in upstream reaches were present. These results will provide important information for conservation management of populations with limited dispersal ability in connected river systems.     

Molecular phylogeny of the freshwater sponges in Lake Baikal

The phylogenetic relationship of the freshwater sponges (Porifera) in Lake Baikal is not well understood. A polyphyletic and/or monophyletic origin have been proposed. The (endemic) Baikalian sponges have been subdivided into two families: endemic Lubomirskiidae and cosmopolitan Spongillidae. In the present study, two new approaches have been made to resolve the phylogenetic relationship of Baikalian sponges; analysis of (1) nucleotide sequences from one mitochondrial gene, the cytochrome oxidase subunit I (COI) and of (2) one selected intron from the tubulin gene. Specimens from the following endemic Baikalian sponge species have been studied; Lubomirskia baicalensis , Baikalospongia intermedia, Baikalospongia recta , Baikalospongia bacillifera and Swartschewskia papyracea . They are all grouped to the family of Lubomirskiidae. Sequence comparisons were performed with the ubiquitously distributed freshwater sponge Spongilla lacustris (family Spongillidae) as well as with one marine sponge, Suberites domuncula . A sequence comparison * * The sequences reported here are being deposited in the EMBL data base. of the mitochondrial COI gene revealed a monophyletic grouping of the endemic Baikalian sponges with S. lacustris as the most related species to the common ancestor. The sequences of the COI gene from B. recta , B. intermedia , B. bacillifera and L. baicalensis were found to be identical and separated from those of S. lacustris and S. papyracea . In a second approach, the exon/intron sequences framing the intron‐2 of the sponge tubulin gene were chosen for the phylogenetic analysis. The intron sequences were aligned and used for construction of a phylogenetic tree. This analysis revealed again a monophyletic grouping with S. lacustris as the closest related species to the common ancestor. It is concluded that the Baikalian sponges, which have been studied here, are of monophyletic origin. Furthermore, the data suggest that the endemic species S. papyracea is the phylogenetically oldest, extant, endemic Baikalian sponge species.     

Morphological delineation and distribution patterns of four newly described species within the Synura petersenii species complex (Chrysophyceae,Stramenopiles)

The Synura petersenii species complex represents a common, cosmopolitan and highly diverse taxon of autotrophic freshwater flagellates. In this paper, we describe and characterize four new species (S. borealis, S. heteropora, S. hibernica and S. laticarina) that have been identified during our extensive sampling of freshwater habitats in 15 European countries. Morphometric analyses of siliceous scales led to the significant phenotypic differentiation of all four newly described species, and their separation from other related species of the S. petersenii complex. Two of these newly described species (S. hibernica and S. borealis) can be clearly distinguished by characteristic large colonies consisting of elongated, lanceolate-shaped cells. Development of strongly elongated, narrow cells in S. hibernica could be explained by the adaptation of this species to oligotrophic conditions. Though morphologically distinct, S. borealis possesses an exceptionally high degree of genetic diversity, possibly indicating recent speciation and evolutionary diversification within this taxon. Three of the four newly described species exhibit restricted biogeographic distribution. The evolutionarily related S. borealis and S. laticarina occur only in Northern Europe, and seem to be adapted to colder areas. The most remarkable distribution pattern was observed for S. hibernica, which has a geographic distribution that is restricted to western Ireland.     

Freshwater sponge silicateins: Comparison of gene sequences and exon-intron structure

Silicateins found in spicules of siliceous sponges are proteins that take part in biogenic silica precipitation and determine the morphological features of spicules. The exon-intron structure of the genes encoding four silicatein-α isoforms (−α1, −α2, −α3, and −α4) from an endemic Baikalian sponge Lubomirskia baicalensis was studied. For eight sponge species, including both cosmopolitan (Spongilla lacustris, Ephydatia muelleri, E. fluviatilis) and endemic Baikalian (L. baicalensis, L. incrustans, Baikalospongia intermedia, B. fungiformis, Sw. papyracea) species, seventeen partial sequences of different silicatein isoform genes were determined. It was shown that cosmopolitan and endemic Baikalian sponges differ from each other in gene structure, in particular, in intron length. Among Baikalian sponges, silicatein-α1 genes had the highest variation of intron length, and silicatein-α4 genes were the most conservative. A phylogenetic analysis based on amino acid sequences of different silicatein isoforms identified four distinct clusters within the freshwater sponge clade. An analysis based on exon-intron gene sequences enables discrimination between different sponge species within the clusters.     

Endemic freshwater finfish of Asia: distribution and conservation status

Freshwater finfish species richness and level of endemism in East, and South and South‐East Asia that included 17 nations were studied using available databases, and included nation‐wise distribution, habitat types, and conservation status. The number of endemic finfish species in the region was 559, belonging to 47 families. Families Cyprinidae and Balitoridae accounted for 43.5% and 16.2% of the total number of endemic species in the region, respectively, followed by Sisoridae (25), Gobiidae (20), Melanotaeniidae (19), and Bagridae (16), and the other 41 families had at least one endemic species. Nation‐wise the most number of endemic freshwater finfish species occur in India (191), followed by China (88), Indonesia (84), and Myanmar (60). In India, the endemic species accounted for 26.4% of the native freshwater fish fauna, followed by South Korea (16.9%), the Philippines, (16.3%) and Myanmar (15.7%). Statistically significant relationships discerned between the number of indigenous and endemic species richness to land area (X_la in 10³ km²) of the nations in the region were, Y_in = 218.961 Ln(X_la) – 843.1 (R² = 0.735; P < 0.001) and Y_e = 28.445 Ln X_la?134.47 (R² = 0.534; P < 0.01), respectively, and between indigenous and endemic species richness was Y_e = 0.079X_n? 1.558 (R² = 0.235; P < 0.05). The overall conservation status of endemic finfish in Asia was satisfactory in that only 92 species were in some state of vulnerability, of which 37 species (6.6%) are endangered or critically endangered. However, the bulk of these species (83.7%) were cave‐ and or lake‐dwelling fish. However, nation‐wise, the endemic freshwater finfish fauna of the Philippines and Sri Lanka, based on the imperilment index, were found to be in a highly vulnerable state. Among river basins, the Mekong Basin had the highest number of endemic species (31.3%). The discrepancies between databases are highlighted and the need to consolidate information among databases is discussed. It is suggested that the Mekong Basin be considered as a biodiversity hotspot, and appropriate management strategies be introduced in this regard.     

Nematodes from saline and freshwater lakes of the Vestfold Hills,East Antarctica,including the description of <Emphasis Type="Italic">Hypodontolaimus antarcticus</Emphasis> sp. n.

The invertebrate fauna of many Antarctic ice-free areas, even those close to permanent research stations, can be poorly known. Here we describe some nematodes from freshwater and saline, marine-derived lakes of the Vestfold Hills, East Antarctica. The freshwater lakes contained the widespread East Antarctic endemic species, Plectus frigophilus Kirjanova, 1958. The saline lakes were inhabited by two recently described species, Halomonhystera halophila Andrássy, 2006 and Halomonhystera continentalis Andrássy, 2006, and by a new species described in this report, Hypodontolaimus antarcticus sp. n. Originally marine but now brackish Highway Lake contained a nematode fauna with both freshwater and marine-derived components. The nematode fauna of Antarctica now consists of 54 named species, 22 of which are found in East Antarctica.     

Phylogenetic position of sponges from Chagatai and Tore-Khol lakes

Morphological and molecular genetic data for freshwater sponges from the lakes of Tuva Depression, Baikalospongia dzhegatajensis (Rezvo, 1936), forms Dzh05 and Dzh06, from Chagatai Lake, as well as forms TKh1 and TKh2, from the Lake Tore-Khol, were obtained and examined. In the sponges examined, which on phylogenetic tree clustered together with the Ephydatia fluviatilis (Linneaus, 1758) sponge from the family Spongillidae, the ITS rDNA regions were sequenced. Comparison of highly variable interal spacer regions of the mitochondrial genome was performed using corresponding sequences of three sponges from the family Spongillidae (E. fluviatilis, E. muelleri and Spongilla lacustris), sponges from the Chagatai and Tore-Khol lakes (Dzh06 and TKh2) with an unknown status, and sponges from the Baikalian family Lubomirskiidae. Minimum genetic differences were observed between E. fluviatilis, Dzh06, and TKh2 (from 0.003 to 0.01% of nucleotide substitutions), while maximum differences were found between the species of Lubomirskiidae and Spongillidae (from 0.928 to 2.06%). The data obtained indicated that sponges from Chagatai and Tore-Khol lakes were most close to E. fluviatilis.     

August Thienemann and Loch Lomond — an approach to the design of a system for monitoring the state of north-temperate standing waters

Limnocnida and Craspedacusta are the two main genera of Cnidaria from continental waters which have a free-swimming medusa in their life cycle. Both originated in tropical-subtropical Asia, but Limnocnida is also found in Africa, with one species (L. tanganjicae) perhaps endemic to lake Tanganyika. Halmomises from Trinidad, and two genera (Mansariella, Keralica) from India have limited ranges. No freshwater medusae evolved in Europe and the Americas (aside from Trinidad), but Craspedacusta sowerbii, by virtue of its drought resistant stages, has managed to colonise all continents, except Antarctica, in the course of the twentieth century. In all, there are about 10–14 freshwater species of medusae. An additional 4–5 species of Moerisia, Australomedusa, and Craspedacusta are sequestered in continental salt-lakes, while a few genera occur in brackish-water seas and estuaries (e.g. Moerisia, Odessia, Ostroumovia). This reduced diversity is probably due to (1) a rarity of drought resistant stages, adjusted to upstream dispersal, in the life cycle, and (2) difficulties to adapt the osmoregulatory system to a hypotonic environment.The feeding ecology of the freshwater medusae is also examined. Like all Cnidaria, they are opportunistic predators. However, fish egg predation might be their major means of subsistence, other types of food being taken only occasionally, or when fish eggs and larvae are scarce. Their impact on the true zooplankton might therefore be limited to short pulses of planktivory. Whether they are themselves limited by predation remains to be studied; many fish in the invasive part of their range avoid them, but some macrocrustaceans readily consume them. It is hypothesized that this might explain their success in Lake Tanganyika, and their absence from lake Baical. Finally, the absence of endemic species from South America could relate to the great diversity bf small-sized predatory aquatic reptiles on this subcontinent.