Salinity and the distribution of rotifers in the Lagos Harbour — Badagry Creek system,Nigeria

The waters of Lagos Harbour have a salinity variation of 30, as a consequence of the annual rainfall regime and of the influx of Atlantic Ocean waters. We made monthly plankton hauls at 10 stations for 11 months starting in October 1986, and found 51 species of rotifers, with Brachionus baylyi Sudzuki & Timms, Keratella hispida Lauterborn, Colurella obtusa Gosse, and Filinia pejleri Hutchinson recorded for the first time in Nigeria. In distribution, species numbers decreased with increasing salinity. Brachionus plicatilis, B. rubens, Hexarthra intermedia, Keratella americana, K. cochlearis and K. tropica were classed as euryhaline. Stenohaline species were Anuraeopsis fissa, Ascomorpha ovalis, Filinia longiseta, F. opoliensis, Gastropus sp., Lecane curvicornis and Monostyla stenroosi. All other monogononts were restricted to waters of salinity below 1.     

Abundance,succession and morphological variation of planktonic rotifers during autumnal circulation in a hypertrophic lake (Heiligensee,Berlin)

Quantitative samples were taken in the pelagial zone of hypertrophic Heiligensee (Berlin, Germany) in the late summer and autumn of 1990. Abundances of 26 species occurring in the plankton, as well as physical and chemical parameters (water temperature, O₂, total phosphorus, SRP, NO₃ ^–, NO₂ ^– NH₄ ⁺ , chlorophyll a) were determined at different depths. Erosion of the hypolimnion due to autumnal storms and decrease in temperature was interrupted by fine weather periods with the occurrence of re-stratification, thus allowing mass production of algae and rotifers (Synchaeta oblonga, S. tremula, Keratella cochlearis) through exploitation of newly available nutrients. Warm stenothermal summer species (e.g. Pompholyx sulcata, Trichocerca pusilla, Liliferotrocha subtilis) became less abundant as a consequence of the progressive mixing process, whereas the appearance of new species was a rare event. The late summer occurrence of Liliferotrocha subtilis in the fraction < 30 µm (up to 3500 ind. l^–1) is remarkable. Keratella cochlearis showed morphological variation from spineless summer forms to spine-bearing autumnal forms, the latter particularly dominating the deeper water layers. The prevailing phenomenon was the dramatic decrease of the total number of individuals and of species towards completion of autumnal turnover. The impact of falling temperature, increasing mixing depth and mass production of phytoplankton on the rotifer plankton community is discussed.     

Zooplankton of a swamp water ecosystem

The Great Dismal Swamp, located in southeastern Virginia and extending into northeastern North Carolina, is a unique ecosystem which has undergone severe alteration over the last 200 years due to agricultural, municipal and timbering development. The swamp is presently about 50% of its late 1700 size when George Washington commissioned the construction of the first of a series of drainage ditches that have subsequently reduced the swamp aquatic environs to a ditch network draining into Lake Drummond located near the swamp's center. The swamp waters are characterized by a brown color, high suspended organic matter, high acidity and low nutrient levels. This paper presents the first comprehensive study of the zooplankton assemblages of the Great Dismal Swamp.Zooplankton was collected for one year at 14 stations and was dominated by rotifers. Of the 84 species identified, 61 were rotifers, 18 were Cladocera and 5 were copepods. Many of the species collected were cosmopolitan and acid tolerant forms. Dominant lake rotifers included Polyarthra vulgaris, Conochiloides dossuarius, Keratella cochlearis, Trichocerca similis, Synchaeta longipes and Microcodon clavus. Dominant crustaceae included Bosmina longirostris, Diaphanosoma leuchtenbergianum, Mesocyclops edax, and Tropocyclops prasinus.Usually the ditch zooplankton was the same as that of the lake. Of the seven ditches studied, the most unique chemically and biologically were Interior, Washington, and Portsmouth. Measurable alkalinity was detected in Interior and Washington Ditches. Alkaline water rotifers such as Brachionus, Mytilina, Filinia, Notholca Platyias and Keratella earlinae were found in these ditches. The rotifer, Keratella valga, was only found from Portsmouth Ditch, during a period when water was flowing into the lake and it contained high nutrient levels.Research funded in part by the Virginia Academy of Sciences and the Center for Environmental Studies, Virginia Polytechnic Institute and State University.     

Quantitative comparison of food niches in some freshwater zooplankton

Summary The abilities of some zooplankton (rotifers, cladocerans, copepods) to ingest different sizes and kinds of food cells were quantified by determining the relative efficiencies with which they ingested nine tracer-cell types, ranging from a coccoid bacterium (0.45 m³) to the alga Cryptomonas erosa (800–920 m³). These efficiencies were obtained by dividing the clearance rate of each zooplankton group (species population, developmental stage or size class of a species population) on each ³²P-labeled cell type by that of a simultaneously-offered, ³³P-labeled, standard cell type — Chlamydomonas reinhardtii. Similarities of efficiency patterns on these cell types (food niches) between all possible pairs of the 17 zooplankton groups from 4 ecosystems were determined by calculating correlation coefficients. Although the utilization of the tested cell types may vary greatly within a species, three feeding guilds could be distinguished — based primarily on the efficiencies with which the smallest cell types were ingested. Guild I (Poyarthra vulgaris, Keratella crassa, Diaptomus minutus nauplii) ate the smallest cells (<4 m diameter) (bacterium, Synechococcus, Nannochloris) and Ankistrodesmus very ineffifently but the three Cryptomonas species very efficiently. Guild II (Bosmina longirostris, D. minutus copepodites and Adults) had higher efficiencies on Synechococcus, Nannochloris, Ankistrodesmus, Stichococcus, and Stephanodiscus than guild I but similarly low ones on the bacterium and high ones on the Cryptomonas species. Guild III (Conochilus inicornis, Keratella cochlearis, Ceriodaphnia quadrangula, Diaphanosoma leuchtembergianum) differed from guilds I and II in having uniformly high efficiencies on all the small cells as well ad the larger ones. Principal component analysis of the matrix of correlation coefficients provided objective confirmation of the three guilds and provided a visual representation of the food niches of the 17 zooplankton groups in 3-dimensional space.     

Additions to the rotifer fauna of south-east Asia: new and rare species from north-east Thailand

Ninety-three freshwater habitats in the north-eastern part of Thailand were surveyed for rotifers during March–October 1993. Two hundred species were identified, 120 of which are new to Thailand. Brachionus africanuss Segers, B. lyratus Shephard and Trichocerca hollaerti De Smet are new to Asia. Brachionus niwati n.sp. is described and figured. Brachionus donneri Brehm, Keratella edmondsoni (Ahlstrom) and Lecane blachei Berzi, endemic to south and southeast Asia, were found also.Comments are presented on some insufficiently known taxa. Of special zoogeographic interest is the record of several species previously considered endemic to Australia. An attempt is made to characterise the Thai rotifer fauna in the light of recent developments in rotifer zoogeography.     

Three new species of Stiphrornis (Aves: Muscicapidae) from the Afro-tropics,with a molecular phylogenetic assessment of the genus

We describe three new species of forest robin in the genus Stiphrornis; two from West Africa and one from the Congo Basin. Each species represents a distinct phylogenetic lineage based on genetic analysis. In addition to genetic differentiation, each new species is diagnosable from other Stiphrornis lineages by morphology, and by plumage. One of the new species appears to be restricted to the Central and Brong-Ahafo Regions of Ghana, and another is restricted to Benin and the Central Region of Ghana. In Ghana, these two new species presumably come into contact with Stiphrornis erythrothorax (Western Region of Ghana and westward), and there is evidence that one of the new species has a distinguishably different song from erythrothorax. The distribution of the third new species is primarily on the south bank of the Congo River, near the city of Kisangani. Recognition of these species provides additional evidence that Afrotropical forests are harbouring substantial cryptic diversity, and that our knowledge of the drivers of this diversity remains poorly documented across the region.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:BF2A0BE6-1140-4EFF-9035-380D61AB03AE     

A new and phylogenetically suggestive morphotype ofKeratella lenzi (Rotifer,Monogononta), from Argentina

The morphological characteristics ofKeratella lenzi (f.ayui) f. nov. and the phylogenetic and ecological implications of the appearance of posterolateral spines inK. lenzi Hauer, 1953 are discussed. The morphotype is described after detailed observations using light and scanning electron microscopy, and compared with otherKeratella species of the superspecies valga. The pores of the lateral antennae are described, and proposed as a new character for future comparative research. Some ecological information is also given.     

Evidence of a link between taboos and sacrifices and resource scarcity of ritual plants

Background

One of the main obstacles for the mainstreaming of religious traditions as tools for the conservation of nature is the limited applicability of research results in this field. We documented two different restrictions implemented by local people (taboos and sacrifices) related to the use of ritual plants in Benin (West Africa) and Gabon (Central Africa).

Methods

To see whether these restrictions reflected plant scarcity from an etic perspective (official threat status) and an emic viewpoint (perceived scarcity by local people), we conducted 102 interviews with traditional healers and adepts of traditional faiths.

Results

We documented a total of 618 ritual plants, from which 52 species were used in both countries. In Benin, the use of 63 of the 414 ritual plant species was restricted; while in Gabon 23 of the 256 ritual plants were associated with taboos and sacrifices. In Benin, restricted plants were significantly more often officially threatened, perceived as scarce, and actively protected than non-restricted plants. In the more forested and less densely populated Gabon, plants that were perceived as scarce were more often associated to local restrictions than officially threatened species.

Conclusions

These results prove the presence of a form of adaptive management where restrictions are related to resource scarcity and protection of ritual plant species. By providing baseline data on possibly endangered species, we demonstrate how plant use in the context of religious traditions can yield important information for conservation planning.

Electronic supplementary material

The online version of this article (doi:10.1186/1746-4269-11-5) contains supplementary material, which is available to authorized users.     

Detrital feeding in natural zooplankton communities: Discrimination between live and dead algal foods

Freshwater zooplankton species differ in their consumption of live and dead algal cells when tested in situ. Using isotopically-labeled living and heat-killed Chlamydomonas reinhardti as models for phytoplankton and detrital seston, respectively, we tested differential feeding on these foods by 3 rotifers and 2 microcrustaceans. Keratella cochlearis selectively feeds on detrital materials while 2 sympatric rotifer species, Conochilus dossuarius and Kellicottia bostoniensis show no ability to discriminate between the living and dead foods. Both the copepod Diaptomus spatulocrenatus and a cladoceran, Bosmina sp., differentially consume living cells.     

Aquatic pollution assessment based on attached diatom communities in the Pinang River Basin,Malaysia

The diatom communities collected from artificial substrates (glass slides) at 12 sampling sites along Pinang River Basin were analysed. Species composition was highly variable among sampling sites, and the highest diversity value (mean H = 3.56 bit/individual) and species richness (mean S = 17.32) was recorded at a polluted station in an estuary, which received salt-water intrusion during high tide. The downstream sampling stations were heavily organically polluted with Saprobic Index values ranging between 2.81 and 3.10, while upstream stations were relatively clean with Saprobic Index values recorded between 1.40 and 1.96. The diatom community structure and the specific sensitivity of certain diatom species can be related to the degree of water quality in Pinang River Basin. The abundance of certain diatom species could be used as biological indicators to measure impacts of river pollution.     

Urban rotifers: structure and densities of rotifer communities in water bodies of the Poznań agglomeration area (western Poland)

The rotifer fauna of 19 mostly small water bodies (natural and artificial ponds, clay-pits and pools) in Pozna was studied on four occasions during 1996–98 to determine the suitability of urban areas for rotifer habitats. Rotifers were present in all the water bodies studied, with 114 species in 39 genera found, representing ca. 25% of all rotifers recorded from Poland. Mean diversity was 10 spp (range 1–36). Most common were: Brachionus angularis and Keratella cochlearis (spring), Colurella uncinata, Lecane closterocercaand Lepadella patella (summer) and L. closterocerca and K. cochlearis (autumn). Rotifer densities (1-1503 ind l^–1), Shannon's diversity (H 0.00-3.71) and dominant species differed in different water-bodies. The index of percentage similarity of community showed strong differences in qualitative structure of rotifer assemblages. The different types of water habitats, both the existing or the newly created in towns, may explain the relatively high diversity of rotifer communities observed in the urban areas studied.     

Temporal and spatial distribution of rotifera in a Chilean reservoir: A possible effect of impoundment hydrodynamics

Rotifers were sampled at monthly intervals for a year at four monitoring stations in Rapel Reservoir (a hydroelectric impoundment) in Central Chile (34°02S; 71°35W). Fifteen species were identified, but only Keratella cochlearis was consistently found at each station, it usually was the most abundant (> 50% of total rotifers). Marked differences were found among sites; stations I and 2, those nearest to the dam, showed greatest rotifer densities in spring and autumn. Station 4, that nearest to the inflowing rivers, had its highest rotifer abundance in summer. Station 8 had the highest mean density but the least marked seasonal changes in rotifer numbers.The impoundment water dynamics and the relative locations within the lake (distance from the dam or from the rivers) are suggested as determinants for different rotifer assemblages and, probably, for most other planktonic organisms.     

Contributions to the knowledge of African rotifers: Rotifers from Mauritania (W.-Africa)

The number of Rotifer taxa known from Mauritania, is raised from 8 to 90. 61% of these are cosmopolitan, 1 is temperate — boreal, 18% are thermophilic and 20% are tropicopolitan. Most of them are widely distributed in Africa, but some species have limited distributions. The presence of Keratella testudo and Wolga spinifera is remarkable and is probably related to the unusual climatic conditions in the SW Sahara. One phenotype or forma is new to science.     

Oscillations in density and diversity ofPisidium communities in two biotopes in Southern Poland

Summary From September 1979 to October 1980 in two types of biotopes (in the stream at Kali and in the Biaa Przemsza River near Jaroszowiec, southern Poland)P.amnicum, P.milium, P.subtruncatum, P.nitidum, P.personatum, P.casertanum andP. sp.non det. were found.P.amnicum was accepted as an indicator species for the river community, andP.milium for the stream. The irregular changes of species composition of the sphaeriid community in the stream at Kali are rather accidental and the only temporary occurrence ofP.nitidum, P.personatum andP. sp.non det. in the Biaa Przemsza River might be connected with seasonal migration.The dominance structure of thePisidium community in the stream agrees with the model described by CONNELL (1977) for the communities of large sedentary animals and plants. The dominance relations in the river community are similar to the situation described by CONNELL (1977) as characteristic for small lakes and islands.The density of the Sphaeriidae on the chosen habitat in the Biaa Przemsza River oscillated between 300 and 3.300 ind./m² and it reached almost 130.000 ind./m² in the stream at Kali.The SHANNON-WIENER's diversity index (H) and that of equitability or evenness of species abundances (J) had low values during the whole period of investigation.This study was performed as part of the Problem MRII/15 of the Polish Academy of Sciences.     

Effects of interference and exploitative competition from large-bodied cladocerans on rotifer community structure

I examined the effects of a graded density of the large-bodied cladoceran Daphnia pulicaria upon a natural rotifer assemblage to assess the relative magnitudes of interference and exploitative competition. An in situ, 5-day, bag-enclosure experiment was conducted to test the hypothesis that populations of the rotifers Anuraeopsis spp., Keratella cochlearis typica and Polyarthra spp. are differentially suppressed by interference competition. Rotifer density decreases and observed vs. expected mortality rates for all three rotifer taxa were consistent with the hypothesis of suppression via interference competition. Evidence of exploitative effects were also apparent, though interference effects appeared more important at higher cladoceran densities.     

Ecology and fish catches in natural lakes of Benin,West Africa

Synopsis A preliminary study of the ecology and commercial fish catches was carried out in the Toho-Todougba, Ahouangan and Dati lakes (1500 ha) in southern Benin (West Africa) over a period of 18 consecutive months. Water quality, species richness, and the reproductive biology of the dominant species, Sarotherodon galilaeus, were examined. Unlike Lagoon Toho-Todougba, lakes Ahouangan and Dati are less favourable for fish production because of their high total iron content and their relative low pH. The study revealed the existence of 19 species belonging to eleven (11) families: 16 species in Lagoon Toho-Todougba,12 in Lake Ahouangan, and 7 in Lake Dati. Lakes Ahouangan and Dati had a relatively high faunal similarity whereas Lagoon Toho-Todougba exhibited a relatively low faunal similarity with the former systems. In Lagoon Toho-Todougba, six cichlid species were the most important component of the fishery: Sarotherodon galilaeus, Tilapia guineensis, T. zillii, T. mariae, Chromidotilapia guntheri, Hemichromis fasciatus. Three catfish species Chrysichthys auratus, Clarias agboyiensis, and Clarias lazera were harvested in low abundances. Some other fish, such as Polypterus senegalus senegalus, Protopterus annectens and Heterotis niloticus were captured sporadically, with H. niloticus appearing more consistently in catches than the others. Although not abundant, Gymnarchus niloticus and the African pike, Hepsetus odoe, were almost always present in the catches. Ctenopoma kingsleyae appeared only in Ahouangan. Some predatory species, such as Notopterus afer and Xenomystus nigri, are encountered only in lakes Ahouangan and Dati. In Lagoon Toho-Todougba, Sarotherodon galilaeus had a sex ratio (: ) of 0.49:1, and size at maturation was estimated as 12.3 cm TL. The spawning period extended from May to September with the peak occurring in July. Fecundity was correlated to log-body length (r = 0.74) and log-body weight (r = 0.76). Fish catches were estimated at 389 kg ha^–1 year^–1; about 73% of which was Sarotherodon galilaeus. The overexploitation of juvenile fish and the use of this lagoon for the irrigation of palm tree plantations have reduced fish recruitment and mean size.     

Breeders’ knowledge on cattle fodder species preference in rangelands of Benin

Background

We undertook ethnobotanical and ecological studies on fodder plants grazed by cattle across Benin national area. The study aims to ascertain the top priority fodder plants in order to catalogue the indigenous knowledge regarding their use.

Methods

Data were collected through semi-structured interviews and covered 690 breeders and 40 days of pasture walk. These were analysed using similarity index of Jaccard (IS), relative frequency citation (RFC) and fodder value during pasture walk (FVPW).

Results

We documented a total of 257 fodder plant species, of which 116 recorded during ethnobotanical investigations and 195 during pasture walk. These species belong to 181 genera and 54 families. Both methods shared 52 species. Leaves (58%) and leafy stem (28%) were the most grazed parts of plant. The most common species used as fodder included Andropogon gayanus, Panicum maximum, Pterocarpus erinaceus and Flueggea virosa. The top species with a highest FVPW were Panicum maximum and Pterocarpus erinaceus. A total of 16 species were considered as top fodder plants in Benin.

Conclusions

The wide diversity of plants reported indicates that there is a number of promising fodder species in the flora of Benin. The insight gained in this study relating to bovine feeds could guide in the selection and introduction of feed innovations that could improve livestock production.

     

Impact of a diazinon calamity in 1996 on the aquatic macroinvertebrates in the River Meuse, The Netherlands

A more or less continuous load of pesticides has been noted in the River Meuse in recent years. In April 1996, when high concentrations (up toca. 1 g 1^–1) of the insecticide diazinon were measured in the River Meuse at the Belgian-Dutch border, the maximum concentration for drinking water production was exceeded. This was alerted after activity changes of fish and daphnids in the biological monitoring systems (RIZA). These observations were compared with literature toxicity data of diazinon, in order to determine the ecological impact of this diazinon discharge on the aquatic macroinvertebrates. LC₅₀ values of several aquatic macroinvertebrate species were exceeded. In addition, a high mortality was observed in bioassays with the midgeChironomus riparius and the caddisflyHydropsyche angustipennis. It is inferred that the species composition of the macrofauna community in the River Meuse is likely to be reduced by such an accident. Recolonization of the River Meuse by sensitive macrofauna species may therefore be prevented by incidental pesticide discharges.     

The Southern Churchill, Petrocephalus Wesselsi, a New Species of Mormyrid from South Africa defined by Electric Organ Discharges, Genetics, and Morphology

East African and south African churchills (Petrocephalus, Mormyridae) were synonymised in 1959 to become members of a single species of subcontinental, southern African distribution, Petrocephalus catostoma (Günther, 1866). By comparison with the type material for P. catostoma from the Ruvuma River and P. stuhlmanni from the Ruvu River, both of East African origin, we confirm the South African form of churchill to represent a new species, P. wesselsi, ranging from the northern Limpopo and Incomati systems south to the Pongola River (Natal) as its southern limit. We also compared churchills from the Sabie River (25° S, South Africa, Incomati system) with churchills from the Upper Zambezi River (17° S, Namibia), using electric organ discharges (EODs) and morphology. The duration of an EOD pulse of the South African form (N = 39; 943.2±S.E. 18.82µs) is, on average, more than twice that of the Upper Zambezi form (N = 37; 436.6±15.1µs), and the amplitude of the second head-positive phase (P2 phase relative to P1 = 1) significantly weaker (0.133 ± 0.0005 vs. 0.472 ± 0.002 for Upper Zambezi males, 0.363 ± 0.03 for Upper Zambezi females). In contrast to the Upper Zambezi form, the EOD of the South African form exhibits no difference between the sexes. Fish from the two origins differ significantly in 11 out of 14 anatomical characters studied, confirming molecular genetic differentiation on the species level.