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.     

Lipid compounds of freshwater sponges: family Spongillidae,class Demospongiae

More than 100 novel, unusual and rare fatty acids, lipids and sterols have been isolated from freshwater sponges. The structures, biogenesis, synthesis and bioactivity of some lipid compounds of freshwater sponge species are reviewed.     

Spatial and temporal distribution of freshwater sponges in Connecticut lakes based upon analysis of siliceous spicules in dated sediment cores

A survey of 28 Connecticut water bodies for spicular remainsoffreshwater sponges preserved in lacustrine sediments revealed14species representing 10 genera. Sediments were examined atfivelevels (ca 1991, ca 1970, ca 1934, ca 1890, ca 1875)todocument changes in species composition, distribution, andabundance. Five species were recorded statewide in all fivegeologic regions: Spongilla lacustris, Heteromeyeniatubisperma, Anheteromeyenia ryderi, Eunapius fragilis, andEphydatia muelleri. Spongilla lacustris was the mostcommonand widely distributed species. Factors that may havecontributedto the observed distribution of the spongillids in Connecticutareregional differences in lake water chemistries, individualspeciestolerances, and differences in extent of dispersal of variousspecies. Most of the more abundant species are widelydistributedwith respect to water quality parameters. Anheteromeyeniaargyrosperma, Duosclera mackayi and Trochospongillapennsylvanica appear to be restricted to waters exhibitingthelower ranges for conductivity, alkalinity and calcium content.Ingeneral, a greater number of spicules was found in bottomsedimentsof the surveyed lakes as compared with the surface sediments.Oftenthis was correlated with increased sediment accumulation ratesinmore recent periods. When this fact is taken into account, itappears that populations of a number of sponge species haveremained relatively constant in many of the lakes over thepastcentury. However, in some lakes exhibiting lower or onlyslightlyhigher sediment accumulation rates at the surface, fewerspiculeswere also found in more recent sediments, suggesting an actualdecline in sponge population sizes. Changes in abundance overthelast 100 years may be related to changes in land use practicesinsurrounding watersheds and the associated changes in waterchemistries.     

Hatching of freshwater sponge gemmules after low temperature exposure: Ephydatia mülleri (Porifera: Spongillidae)

1. 1.|Gemmules of Ephydatia mülleri can withstand exposure to temperatures down to −80°C for 63 days without loss of hatchability.

2. 2.|Hatching is slowed following exposure to temperatures below −27°C.

3. 3.|There is a slight but significant relationship between gemmule size and the time to hatch.

4. 4.|This species can withstand long-term exposure to winter air temperatures occurring within its known geographic range.

Canal systems and choanocyte chambers in freshwater sponges (Porifera,Spongillidae)

Summary The spongillid species Spongilla lacustris and Ephydatia fluviatilis possess choanocyte chambers of the classical eurypylous type. They are surrounded by the mesenchymal tissue and connected to the incurrent canal system by prosopyles and to the excurrent canal system by wide apopyles. Each apopyle is sealed against spaces between the basal choanocyte collar parts by a ring of uniflagellated cone cells. The functional aspects of the choanocyte chamber and canal structure are discussed.Dedicated to Prof. Dr. K.E. Wohlfarth-Bottermann, Bonn, in honor of his 65th birthday     

The filtration apparatus for food collection in freshwater sponges (Porifera,Spongillidae)

Summary The freshwater sponges (Spongillidae) feed by filtering out small particles from the water passing through them by means of strainer devices in the flagellated chambers. These are filamentous, fine-meshed structures at the distal ends of the choanocyte collars formed of a mucous material similar to that in the glycocalyx. Each strainer separates its flagellated chamber into an outer and an inner zone. The strainers are an extremely efficient filtering mechanism.     

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.     

Xenochironomus ceciliae (Diptera: Chironomidae), a new chironomid species inhabiting freshwater sponges in Brazil

Chironomids living inside freshwater sponges are scarcely known, particularly in the Neotropical region where most of them are to be described. Here, male and female adults, pupa and 4th instar larva of Xenochironomus ceciliae sp. n., living in freshwater sponges of the Paraná River (Brazil) are described. The larval labrum with its several densely setose or combed structures somewhat resembling the filtering structures of simuliid larvae and the predominance of fine detritus in the larval gut contents, may indicate that the larvae of Xenochironomus ceciliae sp. n. are collector-filterers and they might be favored by the aquifer systems of the sponges.     

Impact of hydrology on free-living and particle-associated microorganisms in a river floodplain system (Danube, Austria)

1. A floodplain segment of the Danube River downstream of Vienna was studied during the hydrologically most dynamic phase (spring–summer) to evaluate the significance of connection between the main channel and the floodplain segment for particle abundance and quality as well as for bacterial and viral parameters, both free‐living and attached to particles. 2. Hydrological connectivity between the main channel and its floodplain segment (expressed as water age) influenced particle abundance and quality. Polysaccharide‐containing particles [Alcian positive‐stained particles (ASP)] and protein‐containing particles [Coomassie positive‐stained particles (CSP)] each contributed a substantial fraction to total suspended solids and were both positively related to water age. ASP were about twice as abundant as CSP. 3. Water age influenced bacterial and viral abundance and the bacterioplankton productivity in the surrounding water. Free‐living bacterial abundance and their bacterial secondary production (BSP) increased continuously with water age, best described by a linear regression. Water age also significantly impacted BSP and per cell BSP of bacteria attached to particles. The abundance of attached bacteria and viruses was not influenced by water age. 4. Bacteria and viruses on particles were influenced by particle quality. Their abundance on particles was closely related to particle size. Particle‐attached bacteria accounted on average for 30.34% (± 3.09) of the total bacterial abundance. A variable and occasionally significant proportion of viruses, between 0.43% and 35.06%, were associated with particulate material. 5. Bacteria attached to particles were significantly more productive than their free‐living counterparts. Their per‐cell activity was on average 8.6 times higher than that of the free‐living fraction. 6. Hydrological connectivity between the Danube River and its floodplain is crucial not only for the exchange of water, sediment and nutrients, but also for microbiota, thus influencing microbial life, distribution and activity.     

Intracellular pathways and degradation of endosomal contents in basal epithelial cells of freshwater sponges (Porifera, Spongillidae)

 The digestive system expressed by basal epithelial cells of the freshwater sponges Spongilla lacustris and Ephydatia muelleri is mainly represented by a population of 30–50 preexisting lysosomes located in the close vicinity of the central nucleus. The strongly acidic vacuoles (pH 4–4.5) vary in size between 1 and 3 μm, and contain a set of different lysosomal enzymes. Immunocytochemical studies succeeded in the detection of β-hexosaminidase, cathepsin D, acid phosphatase, and α-glucosidase. Endosomes resulting from fluid-phase macropinocytosis, receptor-mediated endocytosis, or phagocytotic activity deliver their exogenous contents to the preexisting lysosomes for enzymatic degradation. Macropinosomes and phagosomes follow a rather reduced intracellular pathway by immediate fusion with the lysosomal compartment, whereas substances conveyed by coated vesicles pass through two additional vacuolar stages, namely early and late endosomes. Early endosomes serve as sorting organelles and segregate various constituents of complex ligands (BSA-AU_6, BSA-AU₁₂) by size into individual late endosomes, which then coalesce with preexisting lysosomes. As a whole, the intracellular pathways and hydrolytic processing of endosomal and phagosomal contents in freshwater sponge cells share certain similarities with the respective mechanisms in cells of higher eukaryotes. Accepted: 7 October 1997     

Detection of distinct endocytotic and phagocytotic activities in epithelial cells (pinacocytes) of freshwater sponges (Porifera, Spongillidae)

 Light and electron microscopical investigations using externally applied fluorescent and gold-labeled markers have revealed the existence of distinct endocytotic and phagocytotic activities in basal epithelial cells (pinacocytes) of the freshwater sponges Spongilla lacustris and Ephydatia es) of the f. The total rate of endocytotic membrane uptake, ascertained by the application of the cationic lipid probe TMA-DPH, was found to be 3.2% of the cell surface area/h. A typical fluid-phase endocytosis, demonstrated by the use of the water-soluble membrane-impermeable tracers BCECF-dextran and LY-CH, participates in endocytotic activity at a rate of 0.7% of the cell surface area/h and results in the formation of endosomes measuring 0.8–1 μm in diameter. Moreover, the application of labeled BSA succeeded in the detection of a receptor-mediated endocytosis amounting to a concentration-dependent uptake of 2.3–2.8% of the cell surface area/h. Coated pits and coated vesicles conveying the adsorbed BSA measure 0.3 μm in diameter and are covered on the cytoplasmic face with a clathrin-like protein (HC, 180 kDa; LC, 30 kDa). To facilitate phagocytotic activities, a series of fluorescent–labeled and chemically treated particles such as bacteria or latex beads have been successfully employed. Accordingly, the measured values of phagocytic membrane uptake between 1 and 8% of the cell surface area/h depend on the variety of size as well as the chemical nature of the different bioparticles and clearly point to phagocytosis as a key mechanism for providing freshwater sponges with nourishment. Accepted: 3 April 1997     

Effects of flooding on recruitment and dispersal of the Southern Pygmy Perch (Nannoperca australis) at a Murray River floodplain wetland

Summary With limited evidence linking Australia's Murray‐Darling Basin fish species and flooding, this study assessed annual variation in abundance and recruitment levels of a small‐bodied, threatened floodplain species, the Southern Pygmy Perch (Nannoperca australis), in floodplain habitats (creeks, lakes and wetlands) in the Barmah‐Millewa Forest, Murray River, Australia. Spring and summer sampling over a 5‐year period encompassed large hydrological variation, including 1 year of extended floodplain inundation which was largely driven by an environmental water release, and 2 years of severe regional drought. Recruitment and dispersal of Southern Pygmy Perch significantly increased during the floodplain inundation event compared with the other examined years. This study provides valuable support for an environmental water allocation benefiting a native species, and explores the link between flooding and its advantages to native fish. This suggests that the reduced flooding frequency and magnitude as a result of river regulation may well be a major contributing factor in the species’ decline in the Murray‐Darling Basin.     

Life cycle of Spongilla lacustris (Porifera,Spongillidae): a cue for environment-dependent phenotype

We studied the life cycle and growth of Spongilla lacustris in a stream with three distinct habitats. Sponge populations in the habitats exhibited different adaptive strategies. Growth forms of S. lacustris ranged from encrusting to digitate and branched. Environmental factors controlled the appearance of each growth form. In the most hospitable habitat, a variety of colonization strategies and different growth forms were present. In the less hospitable habitat growth was restricted to small and encrusting specimens. In the optimal habitat, the largest and most luxuriant specimens developed. Gemmulation and hatching were dephased among specimens in the three habitats; hence gemmules were present for long periods of time. S. lacustris was found capable of displaying two life strategies: r in the short run, K in the long run.     

Spatial and environmental effects on hydrophytic macrophyte occurrence in the Upper Rhine floodplain (Germany)

The occurrence of exclusively submerged macrophytes (hydrophytes) was analyzed on a data set of 608 mapped stream segments with a total length of 106 km from the Upper Rhine floodplain. There were three objectives. The first was to test the evidence of plot-sized bias which occurs when structural homogenous river sections are mapped. In the dataset, with a broad range of areas sampled, this bias was small but the mapping procedure nevertheless had some disadvantages for ecological interpretation of hydrophyte data. The second objective was to test for spatial autocorrelation of species composition among consecutive stream sections. Results showed that spatial autocorrelation is an intrinsic and not easily interpretable feature, which might weaken the interpretative strength of pure species–environment relationships in streams. The third objective was to analyse species–environment relationships, by redundancy analysis. The analyses gave satisfying distribution patterns of the 25 most frequent hydrophytes, using a small group of environmental parameters—current, shading, turbidity and maximum depth. They could be assigned into three groups—rheophilic, potamale and related to groundwater influence. The high amount of unexplained variability in species data is due to the large data set where the high plasticity of most hydrophytes becomes apparent and thus resulting in a broad niche overlap. The study gives a representative overview over one of the richest regions in Germany for hydrophytes. Handling editor: S. M. Thomaz     

Dietary–morphological relationships in a fish assemblage of the Bolivian Amazonian floodplain

Morphological correlates of diet were examined in 48 species of freshwater fishes from floodplain lakes in the central part of the Mamoré River (Bolivian Amazon). The species were classified, according to the percentage occurrence of seven food items, into eight broad trophic categories: mud feeders, algivores, herbivores, terrestrial invertivores and omnivores, carnivores, zooplanktivores, aquatic invertivores and piscivores. There were significant relationships between the diet and morphology of the fishes even when the effect of taxonomical relatedness between species was eliminated. Relative gut length was the main morphological variable used to order species on a carnivore to mud feeder gradient. Standard length and head and mouth size were the morphological variables most closely associated with prey size. Mud feeder, algivore and piscivore species appeared as the most dietary and morphologically specialized. These results support both the hypotheses that species morphology influences the diet and that morphological similarity is conserved even in comparison with taxonomically unrelated species.     

High abundance of Trochospongilla horrida (Porifera, Spongillidae) in the Rhine (Germany) 1992–1995

Trochospongilla horrida (Porifera, Spongillidae) was the dominant freshwater sponge in the Rhine between Karlsruhe and Bonn between 1992 and 1995 are reported. It showed an annual life cycle, with an inactive phase during winter. The life cycle was controlled by temperature. Gemmules were produced in high numbers, and played a significant role as resting bodies. Their role as distribution units was negligible because they were tightly fixed to the substratum. Trochospongilla horrida preferred relatively stable habitats, not affected by fluctuations in water level; it was restricted to habitats with a slightly alkaline pH. Laboratory experiments showed a delayed germination of the gemmules, which explains why the highest abundance of the species occured considerably after the first hatching colonies.