Population dynamics of Bosmina longirostris (Crustacea: Cladocera) in Lake Kariba,Zimbabwe

The population dynamics of Bosmina longirostris in a large tropical reservoir, Lake Kariba, Zimbabwe, are described. Population density showed two peaks associated with periods of high nutrient fluxes. Fecundity was always low. Two eggs per female was the maximum ever recorded. Instantaneous rates of birth, death and population growth calculated from field data using the egg ratio method are discussed. The rate of biomass change fluctuated in a regular pattern, probably linked to food availability or predation by a clupeid, Limnothrissa miodon.     

The late Holocene appearance of European Bosmina (Eubosmina) thersites (Crustacea, Cladocera) in lakes surrounding the Baltic Sea

This study shows the appearance of Bosmina (Eubosmina) thersites during the last millennium in two lakes in Northern Europe: Lake Charzykowskie (Poland) and Lake Lohja (Estonia). Cladocera remains collected from both lakes showed similar Bosmina species composition and changes during the late Holocene. Older sediment layers showed a prevalence of smaller Eubosmina species (B. (E.) longispina), indicating oligotrophic conditions of the lakes, while younger layers were dominated by larger species (B. (E.) coregoni and B. (E.) thersites), typically found in lakes with higher trophy. The presence of B. (E.) thersites has rarely been reported in paleolimnological research, and this is the first observance of its high abundance in lake sediments. More research is needed, however, to better understand the appearance, speciation driver, continental range, and ecological preferences of B. (E.) thersites.     

Competition and Population Time Lags in Bosmina (Cladocera,Crustacea)

The competition between Bosmina coregoni and B. longirostris was studied by culturing of mixed and isolated populations in lake water. While interaction was detectable between the two species, they were capable of coexisting for at least 124 days. The pattern of predominance was found to depend on initial frequencies. The ratio of B. coregoni to B. longirostris in the pelagic zone of a mesotrophic lake could be explained on the basis of competition between either species. Birth, death, and population growth rates proved to be delayed functions of stock density, as was borne out by cross-correlation analysis of experimental population dynamics. Time lag estimates for all three rates varied for different phases of population oscillation. For accurate assessment of time lags, the phases of monotonous changes in density should have been separated from one another. The time lag estimated for the rate of population growth in mixed cultures was significantly higher for the superior competitor (B. coregoni). This estimate may well be predicted as an arithmetic mean value cf time lag estimates for birth and death rates. The duration of population growth (or decline) was correlated to the time lag of the death rate, whereas the amplitude was not correlated to any time lag at all.     

Genotypic succession in the cyclomorphosis of Bosmina longirostris (Cladocera)

SUMMARY. The pattern of cyclomorphosis of Bosmina longirostris was followed over a 21-month period in Lake Travis, Texas. Appreciable variation was observed in body size and in the lengths of antennules and mucrones. Electrophoresis of clonal isolates collected over the period of study showed a seasonal cycle in esterase phenotypes. A definite association was demonstrated between the esterase phenotypes and morphologies of these clonal isolates. Individuals of one esterase phenotype were usually large and long-featured, whereas individuals of the other esterase phenotypes were smaller, with short features. The association of morphology and esterase phenotypes from laboratory experiments corresponded to the association observed in field samples. These results support the hypothesis that the cyclomorphosis of Lake Travis Bosmina involves a succession of clones as well as phenotypic plasticity.     

Functional response and food selection of the water flea, Bosmina longispina

The functional response and the feeding behaviour of Bosminalongispina in relation to varying food concentrations were investigatedunder laboratory conditions using radioactively labelled Scenedcsmusacutus and different sized fluorescent latex beads to measureclearance rates and size selectivity. Bosmina longispina reducedfeeding activity at low concentrations of food, having a sigmoidfunctional response. Particles of 5.18 µm were filteredmuch more efficiently than both 1.04- and 0.25-µm particles,and the selectivity of large particles increased with increasingfiltering rates. Scenedesmus acutus was filtered at approximatelythe same rate as 5.18-µm latex beads. The increased selectivityat high filtering rates is explained as an adjustment in thefiltering apparatus to allow for greater water flow. Both thesefeeding responses would tend to reduce energy expenditure insituations when energy intake is low.     

Ecology of predator-induced morphological defense traits in Daphnia longispina (Cladocera,Arthropoda)

Oecologia - Inducible defenses against predators are widespread among plants and animals. For example, some Daphnia species form neckteeth against predatory larvae of the dipteran genus Chaoborus....     

Vertical distribution and abundance of Ceriodaphnia quadrangula (O. F. Muller) (Crustacea, Cladocera)

Distribution and abundance of C. quadrangula (O. F. Muller) has been studied in two small lakes in the southern part ofthe English Lake District. Esthwaite Water (maximal depth 15 m) was sampled from 1958 to 1969 and Blelham Tarn (maximal depth 12 m) from 1961 to 1963. Samples in both lakes were taken with a 5-1 water bottle at a fixed station in deep water. No difference in vertical distribution between day and night samples was observed. The majority of individuals were located below 7 m in Esthwaite Water and above 8 m in Blelham Tarn. The seasonal cycle in the open water was from May to December with maximal abundance in September and October. Males and ephippial females regularly appeared in early October, irrespective of population density, water-temperature or the time of the overturn.     

A taxonomic reappraisal of the European Daphnia longispina complex (Crustacea, Cladocera, Anomopoda)

The Daphnia longispina complex contains some of the most common water flea species in the northern hemisphere, and has been a model organism for many ecological and evolutionary studies. Nevertheless, the systematics and nomenclature of this group, in particular its Palaearctic members, have been in flux for the past 150 years; this hinders the correct interpretation of scientific results and promotes the erroneous use of species names. We revise the systematics of this species complex based on mitochondrial sequence variation (12S rDNA and COI) of representative populations across Europe, with a special focus on samples from type localities of the respective taxa. Combining genetic evidence and morphological assignments of analysed individuals, we propose a comprehensive revision of the European members of the D. longispina complex. We show that D. hyalina and D. rosea morphotypes have evolved several times independently, and we find no evidence to maintain these morphotypes as distinct biological species. Alpine individuals described as D. zschokkei are conspecific with the above-mentioned lineage. We suggest that this morphologically and ecologically plastic but genetically uniform hyalina–rosea–zschokkei clade should be identified as D. longispina (O. F. Müller, 1776). The valid name of Fennoscandian individuals labelled D. longispina sensu stricto in the recent literature is D. lacustris G. O. Sars, 1862. Additionally, we discovered another divergent lineage of this group, likely an undescribed species, in southern Norway. Our results present a solution for several prevailing taxonomic problems in the genus Daphnia , and have broad implications for interpretation of biogeographical patterns, and ecological and evolutionary studies.     

Effect of food concentration on growth, reproduction and survivorship of Bosmina longirostris (Cladocera)

SUMMARY. 1. Body growth, reproduction and survivorship of Bosmina longirostris were monitored at four food concentrations (0.05, 0.10, 0,25 and 2.50 ing Cl⁻¹) to examine the extent to which food concentration affects these life-history parameters.
2. Food concentration had a significant effect on growth, and most of the reproductive parameters (size and age at maturation, brood size, instar duration and egg development time). More than 60% of animals died before maturation at the lowest food concentration, although most animals survived until maturation at other food concentrations.
3. Change in life-history parameters resulted in a decrease in rate of population growth ( r ) from 0.310 to 0.020 day⁻¹ with decreasing food concentration, showing that this cladoceran is highly food-limited in many lakes.
4. Importance of the effect of food concentration on egg development time was emphasized in relation to analysis of natural populations.     

Population dynamics and production of Daphnia galeata (Crustacea, Cladocera) in Lake Esrom

The population dynamics and production of D. galeata Sars were investigated from April 1974 to April 1975. The population density and biomass was maximum in June. Population dynamics indicated that food supply was better in spring and early summer than mid-summer. Net production was calculated by method of daily addition of biomass for eight size groups. The total net production of biomass for the year of investigation was 26.5 g dw m⁻². The P/B yr⁻¹ was 35 8.     

Subgeneric differences in head shield and ephippia ultrastructure within the genus Bosmina Baird (Crustacea,Cladocera)

Seven samples of roach (Rutilus rutilus L.) fromthe Austrian section of the Danube river, the Drauriver and lake Wallersee were examined to studypossible population genetic effects of anthropogenichabitat modification and subdivision. Geneticvariability was assessed using electrophoreticvariation of 11 enzyme systems coded by 14 gene loci.Genetic variation of roach was remarkably high, andwas mainly located within samples while differencesbetween them were weak. Morphometric analyses ofconventional external measurements revealedconsiderable morphological variation within samples.Significant differences between samples mainlyinvolved body depth and fin size, but did not allowadaptive ecomorphological interpretations in severalcases. The comparison of morphological and geneticvariation showed no significant correlations but waslimited by the narrow range of heterozygosityestimates.     

Temperature- and predator-induced phenotypic plasticity in Bosmina cornuta and B. pellucida (Crustacea: Cladocera)

SUMMARY 1. Clones of Bosmina cornuta and B. pellucida (B. longirostris species complex) were derived from samples collected from Scheuermühlenteich and Lake Windsborn(westernGermany). Experimental temperature change (to 10 °C and 20 °C) and exposure to Acanthocyclops vernalis copepods (12 L^?1) significantly altered external morphology in laboratory cultures of the two species. Morphological traits were derived from eight log₁₀‐transformed and standardised morphometric distances by factorial analysis: factor 1 represented body size, factor 2, size of appendages and factor 3, the head size. 2. Acclimation of clones to cold water (10 °C, >14 days) led to an increase in body, antennule and mucrone size in B. cornuta and B. pellucida. Moreover, at 10 °C, B. cornuta cultures usually collapsed within a few weeks. Compared to the trials at 10 °C, acclimation to 20 °C (the two species) and to 15 °C (B. pellucida only) left the size of body appendages unchanged. Individuals were unequivocally assigned to each species by discriminant functions. Conspecific individuals that were acclimated to different temperatures between 10 and 20 °C also differed in external morphology, but discriminant analysis yielded misclassification rates of 5.3–23.3%. 3. Morphological response to the presence of copepod predators was weaker than that caused by temperature change. Long‐term exposure of clones to copepod predators induced a significant increase in size of appendages in the two species but left body size unaffected. Again, species identification by discriminant functions could be made without any error, whereas conspecific controls and experimentals were misclassified at rates between 19.4 and 29.5%. 4. It is suggested that temperature is the main proximal cue for Bosmina cyclomorphosis. The distinct response to temperature of B. pellucida and B. cornuta may also account for seasonal differences in abundance observed in field.     

Abrupt Changes in Bosmina (Cladocera,Crustacea) Assemblages During the History of the Ostrowite Lake (Northern Poland)

During the 10000-year history of the Ostrowite Lake, there have been several episodes of change in dominance amongst species of the genus Bosmina. The dominants were alternately B.longirostris and Eubosmina spp. Amongst the subgenus Eubosmina, two species prevailed in different periods:Bosmina coregoni and Bosmina reflexa. The first species, Bosmina coregoni, is characterized by long antennae and short carapace mucrones, while the second one, Bosmina reflexa, by short antennae and very long mucrones. Bosmina reflexa was dominant at the beginning of the lake's history (Preboreal, 10000--9000 BP) and during the early Subboreal Period (5000–3500 BP). Only a small number of remains of Bosmina longispina(Eubosmina spp.) were present along the entire profile. Such strong changes in the domination of Bosmina species were observed for the first time in the sediments of Polish lakes. A similar transition from one species to another has been described in a few German lakes and was linked to climate changes. However, the changes in the Ostrowite Lake do not correlate with climate changes, but most probably, with changes in the lake's trophic level. This is suggested by the simultaneous increase of Bosmina reflexa and a good indicator of eutrophy, Bosmina longirostris.     

Plankton community of a polyhumic lake with and without Daphnia longispina (Cladocera)

The impact of Daphnia longispina (Cladocera) on the plankton food web was studied in a polyhumic lake where this species comprised almost all zooplankton biomass. Plastic enclosures (volume 7 m³) were inserted into the lake retaining the initial water stratification except that in one enclosure zooplankton was removed. After the removal of Daphniaa rotifer, Keratella cochlearis, ciliates and heterotrophic nanoflagellates increased markedly and the density and biomass of bacteria decreased. Edible algal species, Cryptomonas rostratiformisand three small chrysophytes,Ochromonas, Pedinella and Spinifermonas, took advantage of the removal of Daphnia, while more grazing-resistant species declined. In spite of the changes in the species composition of phytoplankton, the removal of Daphnia did not affect the biomass, primary production or respiration of plankton. The results implied that the density of heterotrophic flagellates and ciliates was controlled by Daphnia, but in its absence the former took its role as the bacterial grazers.     

Development of microsatellite markers for Diaphanosoma dubium (Crustacea,Cladocera) and application to seasonal population dynamics

Diaphanosoma, the “tropical Daphnia”, is common and ubiquitous in South China. Like other ctenopods, Diaphanosoma has a reproductive mode similar to Daphnia’s, but its resting eggs are rarely observed and lack an ephippium. With limited dispersal and reduced buffer effect from resting egg banks, Diaphanosoma is expected to have a population genetic structure different from that of temperate Daphnia. To facilitate genetic comparison, we developed microsatellite markers using next-generation sequencing for the most common species in tropical and subtropical East Asia, Diaphanosoma dubium. Thirty-one polymorphic microsatellite markers were obtained, and 29 of them were efficient for the congeneric species D. excisum, D. orghidani, D. mongolianum and D. chankensis. The markers allowed intra- and interspecific genetic analysis, including population structure, hybridization and introgression. We used 11 selected microsatellite markers to analyze spatial and temporal heterogeneity of genetic diversity in four (sub)tropical D. dubium populations from two large reservoirs and two temporary ponds. In contrast to temperate Cladocera, higher genetic diversity in summer rather than in spring suggested weak contribution from resting eggs in spring. Clustering of DAPC and STRUCTURE analyses indicated a clear-cut genetic structure in the four populations. Variation partitioning revealed that water storage and depth were key factors in genetic differentiation. Within large reservoirs, we detected backward (reversing time) gene flow from resting egg banks. We conclude that resting eggs have an effective contribution to the genetic diversity in large water bodies during growing seasons and that large water bodies can host higher genetic diversity in summer due to environmental heterogeneity and high carrying capacity. Spatial and temporal heterogeneity of genetic diversity detected by our microsatellite markers showed the newly developed markers can be applied for further study of populations of D. dubium and other species of Diaphanosoma at a contemporary scale.

     

Genetic variation in two sympatric European populations of Bosmina spp. (Cladocera) tested with RAPD markers

We used RAPDs (Random Amplified Polymorphic DNA) to test genetic divergence between two populations of Bosmina spp. in Lake Östersjön, Sweden. Previous taxonomic studies on European species within the genus Bosmina have been based on morphological characters alone. RAPD markers distinguished the two populations and supported the specific status of B. coregoni and B. longispina based on morphological characters. Furthermore, juveniles with a long antennule and a mucro were classified as B. coregoni. RAPDs also revealed genetic differences among the tested individuals, suggesting several clones within each species.     

A new member of the subgenus Sinobosmina Lieder, 1957: Bosmina tripurae sp. nov. (Crustacea,Cladocera) from India

A new species, Bosmina tripurae is described from South India. The species shares some of the morphological traits with Bosmina fatalis from East and SE Asia, and two other species described recently from North America. They all form a subgeneric group established earlier: subgenus Sinobosmina Lieder 1957. Parthenogenetic females of the new species are superficially similar to the species Bosmina longirostris, which occurs on Indian subcontinent, only in northern high mountain lakes. All reports of the latter species from Indian lowlands are either Bosmina tripurae or some other not yet described species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Morphological variation and population dynamics of Bosmina (E.) longicornis kessleri Uljanin (Crustacea: Anomopoda: Bosminidae) in the Bukovec Reservoir (S.E. Slovakia)

Bosmina (Eubosmina) longicornis kessleri and B. (Bosmina) longirostris are minor components among the crustacean zooplankton in the pelagial of Bukovec Reservoir. B. (E.) l. kessleri is a recent colonist in the Carpathian region and was first found in the Bukovec reservoir in 1986. The present study gives some information about the niche occupied by B. (E.) l. kessleri in the zooplankton community; the seasonal abundance of zooplankton and phenotypic variability (cyclomorphosis) of B. (E.) l. kessleri are also examined.     

Effect of food concentration on the carbon balance of Bosmina longirostris (Crustacea: Cladocera)

SUMMARY. 1. The carbon balance of the small cladoceran, Bosmina longirostris , was examined at four food concentrations (0,05, 0.10, 0.25, 2.50mg C 1-⁻¹) based on long-term growth experiments.
2. At birth, B. longirostris allocated about 60% of assimilation to body growth at all food concentrations. However, allocation to body growth decreased with age and was less than 5% after the fourth instar at the lowest food concentration. The proportion allocated to reproduction increased with increasing food concentration, but was relatively constant among different adult instars.
3. Assimilation rate increased with increasing food concentration and increasing body size: the mean rate from birth to 15 days was 6.6 times higher at the highest food concentration than at the lowest food concentration. However, with decreasing food concentration and increasing body size, a higher proportion of the assimilated carbon was lost as respiration. As a result, the net production rate reached a plateau at intermediate body size and was 9.1 times higher at the highest food concentration than at the lowest food concentration.
4. Comparison with previous studies revealed that B. longirostris is more efficient than Daphnia with regard to carbon production, especially at low food conditions, if the death rate is negligible.