Anostraca,Cladocera and Copepoda of Spanish saline lakes

A study of 102 samples from almost all salt water bodies in Spain has allowed the preparation of a comprehensive list of anostracans, cladocerans and copepods living in such extreme environments. Among the 26 species recorded, 9 are halobionts, but 17 can exist in less saline waters. Of the halobionts, several are widely distributed throughout arid areas around the Mediterranean (Arctodiaptomus salinus, Cletocamptus retrogressus, Branchinectella media, Branchinella spinosa, Daphnia mediterranea, Moina salina); Branchinecta orientalis ( = B. cervantesi) only appears in Guadiana watershed and toward the east of Hungary, and the Alona belonging to the A. elegans complex is a Spanish endemic. In the second group are many typically freshwater species which also appear occasionally in saline waters, and colonizers of wetlands in steppes, characteristically adapted to a wide range of salinity; one of the formers, Diaphanosoma cf. mongolianum, deserves closer study. The Spanish halobiontic fauna seems to be very old judging by the existence of some isolated species, e.g. B. orientalis may be a Tertiary relic. Persistence through time could have resulted from the continuous aridity of some Iberian localities during the Pleistocene and the ecological constancy of wetlands maintained by regional groundwater discharges.     

Anostraca,Conchostraca, Cladocera and Copepoda from Tunisia

In samples from 62 localities in Tunisia and La Calla area in N.E. Algeria, 56 species of Entomostraca were found. More than half of these are widespread and give little insight into the origin of the regional fauna. A few are endemic to the area and three groups are of relictual nature. The first one consists of northern species, some of which are known to have reached the central Sahara. It is argued that their populations have an estimated age of about 5–6000 yrs. At first sight, the second and more numerous group of species, the Ethiopian relicts, should be older. However, until historical times pathways around the Sahara may have functioned. One was along the Atlantic coast; a second and older one was via the Nile. The second possibility is almost a certainty, since a third group of relicts, the Oriental one, has migrated into the central Sahara as far as (and therefore probably together with) the northern relicts. This group must have come via the Nile Delta and the Libyan desert. If that pathway has also been used by Ethiopian species, all three groups of relicts are of the same age. In our Tunisian collection, only one Oriental element is represented.From a taxonomical point of view, morphological differences between the Chydorids Alona rectangula Sars and Alona elegans Kurz are sorted out and illustrated. Alona rectangula is best regarded as a superspecies. Hybridisation with A. elegans appears possible.Contribution n° 23 from project Limnology of the Sahara, under Contract n° 2.0009/75 with the Fonds voor Kollektief Fundamenteel Onderzoek, Belgium     

Rotifera, Cladocera, Copepoda, and Ostracoda from coastal wetlands in northeast Algeria

Two wetland complexes in the El Kala area, northeast Algeria, were sampled for zooplankton over a two-month period (mid-May to mid-July 1993). Some samples from 1976 and 1978 were also studied. A total of 98 taxa (51 species of Microcrustacea and 47 species of Rotifera) are recorded. Twenty-seven of these (26.5% overall) are new to Algeria and/or to the Maghreb and Africa. A significant fraction of Afrotropical species was found in all four groups, beside species of northern (European) origin, and at least one cyclopoid copepod with an Irano-Turanian range. These results confirm the El Kala wetlands as an important relict pocket of species of various historical and geographical origin, and highlight the urgency of safeguarding these sites. This revised version was published online in July 2006 with corrections to the Cover Date.     

Freshwater Crustacea (Cladocera,Copepoda) of Iceland: taxonomy,ecology, and biogeography

Of the many types of freshwater bodies across Iceland (e.g., lakes, springs, rivers, and ponds), greater effort has been invested in researching the freshwater Crustacea (Cladocera, Copepoda) of more permanent, larger, and deeper water bodies than on smaller or more ephemeral sites. To address this, we described the fauna of 12 shallow freshwater bodies distributed from the coast to the central highlands of Iceland. We identified 16 species in 11 genera belonging to six families of Cladocera, and 12 species in eight genera belonging to four families of Copepoda. Five of the species we identified (Alona werestschagini, Cyclops vicinus, Daphnia cristata, Diacyclops abyssicola, and Heterocope borealis) represent new distribution records for Iceland, increasing the number of species now known from this region to 34 Cladocera and 38 Copepoda taxa. Additionally, we discuss the taxonomy of some species with doubtful taxonomical status. Six crustacean taxocenes are described, each characterized by the dominance of different taxa, with bottom sediment characteristics best explaining species assemblage structure. We evaluated the relationships between Icelandic Cladocera and Copepoda faunas and those of the adjacent Svalbard, Faroe, and Shetland Islands, Greenland, and the mainland Norway. The taxonomic composition of the Icelandic fauna is dominated by widely distributed Holarctic, and secondarily Palaearctic and Nearctic species, and is more similar to the faunas of the major North Atlantic islands (64.2–71.8 % similarity) than it is to that of continental Norway.     

Species composition of planktonic Rotifera, Cladocera and Copepoda in the littoral zone of Lake Ladoga

In Mexico, more than 40 000 ha of dams, lakes, canals and drains are infested with waterhyacinth (Eichhornia crassipes). To prevail over the problems resulting from this infestation, specific management programs are needed. Under a national program to control the waterhyacinth, guidelines to deal with the related ecological, social, technical and economic factors, and specific strategies to reduce coverage were developed. The ecological factors which were noted include the identification of the most affected areas and the consequences of proposed treatments. The social aspects embraced the stimulation of user awareness as to the importance of water quality, the creation of organizations to coordinate user-sponsored control activities, and the awakening of a community identity. Basic to all are the technical and economic aspects which make the activities feasible and operational. Examples are given of control by means of water level management, mechanical controls using trituration, and the application of chemical and biological agents, all of which may be combined in an integral program.     

Comparative sensitivity of the several zooplankton species (Cladocera,Copepoda) to sumicidine-alpha insecticide

The sensitivity of seven zooplankton species (Daphnia magna, D. longispina, D. pulex, Simocephalus vetulus, Scapholeberis mucronata, Eudiaptomus graciloides, and Cyclops strenuus) to an insecticide, sumicidine alpha was studied. LD₅₀ values upon a 24-hour exposure were determined. Daphnia pulex and D. longispina turned out to be highly susceptible to the insecticide, while the individuals representing the natural population of D. magna happened to be the most resistant. The data on sensitivity distribution among different zooplankton species are provided, as well as the concentrations potentially hazardous for 5% and 50% of the population are calculated.     

Assessing Cladocera and Copepoda individual disturbance levels in hydrologically dynamic environment

Microcrustacean species (Cladocera, Copepoda) as a significant component of the plankton assembly play diverse roles in floodplain ecosystems and cope with the heterogenic environment differently. Since alterations in the hydro regime are considered disturbance events for zooplankton development, we assessed whether and to what extent are Cladocera and Copepoda exposed to disturbances caused by hydro regime alterations in a floodplain lake. To evaluate the disturbance levels for individual microcrustacean assemblage in different water layers and between different hydrological phases, we applied the abundance/biomass comparison (ABC) method. Recorded microcrustacean assemblages highly depended on the hydrological state of the waterbody and diverged accordingly. Cladocera demonstrated to be more sensitive to change in specific environmental parameters like conductivity, temperature and transparency, while Copepoda exhibited no limitation by ecological variables. Although both groups were influenced by the bottom–up and top–down control, different disturbance intensity was recorded for the individual microcrustacean class. An undisturbed condition during isolation of the Lake allowed Cladocera to reach equilibrium while both microcrustacean groups exhibited moderate to high levels of disturbance following inundation. Regarding disturbance intensity, Cladocera expressed a weak distinction following hydro regime and water layer replacement. On the other hand, Copepoda disturbance levels notably depended on the position in the water column within a specific hydrological phase. Results of the ABC analyses gave a good representation of a real community dispersal in the studied Lake. However, more research is needed to re-evaluate here given levels of disturbance properly.     

Effect of temperature in laboratory studies on development and growth of Cladocera and Copepoda from Tjeukemeer, The Netherlands

SUMMARY. The effects of temperature on development and growth are described for the common Cladocera and Copepoda in Tjeukemeer. Eight cladoceran species and five copepod species have been investigated: Daphnia hyalina, Daphnia cucullata, Bosmina coregoni, Bosmina longirostris, Chydorus sphaericus, Ceriodaphnia pulchella, Diaphanosoma brachyurum, Leptodora kindtii, Acanthocyclops robustus, Mesocydops leuckarti, Diacyclops bicuspidatus, Cyclops vicinus vicinus and Eurytemora affinis . Growth is expressed as length increment per size class (cladocerans) or instar (copepods) per week and as the relationship between time and length. The curvilinear logarithmic equation: In D = In a + b (In T)² is fitted to the development times of eggs, combined naupliar instars and combined copepodite instars, as well as to the longevity of the adults. The results are compared with those found in the literature and differences are discussed.     

Fatty acid composition of Cladocera and Copepoda from lakes of contrasting temperature

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Seasonal and longitudinal aspects of microcrustacean (Cladocera, Copepoda) dynamics in a lowland river

Crustacean zooplankton was sampled extensively from the RiverMeuse between 1993 and 1998. The spatio-temporal aspects oftheir dynamics were examined in relation to the primary forcingfactor: hydrology. A time-series obtained at a fixed samplingstation revealed a strong dependence of development on dischargepatterns, as expected, despite large interannual variabilityin the recorded maximal densities. Benthic cladocerans weremost sensitive to rises in discharge. On the longitudinal plane,much higher densities were recorded in downstream reaches ofthe river, over distances too short for the necessary numberof generations to develop at the generally accepted rates ofgrowth. Short-lived peaks in abundance of large planktonic cladoceranswere also recorded downstream, at a well-defined time of theyear. These observations suggest that hydrology is not alwaysaccountable for all thevariations observed, and that the combinationof supplementary zooplankton inputs, internal production andtrophic effects should also be invoked. In the case of copepods,for the most part represented by cyclopoids, the hypothesisof resident populations is proposed to account for seeminglyunrealistic rises in density.     

The dry weight estimate of biomass in a selection of Cladocera,Copepoda and Rotifera from the plankton,periphyton and benthos of continental waters

Summary A procedure for determining dry weights has been standardized and applied to a number of Cladocera, Copepoda and Rotatoria. In most of the Cladocera, regression equations of the exponential type, relating dry weight to body length, were computed. In the Copepoda, one equation per suborder was computed, and suggestions for future refinements are made. In both groups, a fairly satisfactory agreement was found with literature data where these exist. In both groups, the egg and embryo weight proved to be considerable, relative to the weight of the adult female. In Rotatoria, 4 species could be dealt with in size-classes, and their weight increment per unit length was found to be lower than in the Cladocera and Copepoda. A large number of species were weighed as adults only. A conclusion applicable to the 3 groups is that, as a rule, limnetic species weigh relatively less than littoral, periphytic or benthic species. Even within a species, populations with a more pronounced limnetic way of life weigh less than populations of littoral nature.     

Cladocera and free-living Copepoda from the Fouta Djalon and adjacent mountain areas in West Africa

Thirty-two species of Cladocera and 27 species of free-living copepods were identified in a series of samples collected in 25 localities in and around the Fouta Djalon mountains, West Africa. Beside great richness in numbers of species, the nature of the fauna is noteworthy: at least 20% of the Cladocera and 50% of the copepods are endemic to West Africa. Possible palaeoclimatological reasons for this are discussed. The cladoceran genus Streblocerus is recorded from Africa for the first time. It is an element of northern origin in the fauna of West Africa. More examples of this kind are documented among the Copepoda Cyclopoida and Harpacticoida, but the bulk of the fauna is evidently of tropical origin. In particular, great adaptive radiation is occurring in the local representatives of the genus Tropocyclops. Three new species of Parastenocaris are described; they are the first representatives of this genus found in West Africa.     

Phytoplankton and zooplankton (Cladocera,Copepoda) relationship in the eutrophicated River Danube (Danubialia Hungarica,CXI)

The seasonal variation in primary production, individual numbers, and biomass of phyto- and zooplankton was studied in the River Danube in 1981. The secondary production of two dominant zooplankton species (Bosmina longirostris and Acanthocyclops robustus) was also estimated. In the growing season (April–Sept.) individual numbers dry weights and chlorophyll a contents of phytoplankton ranged between 30–90 × 10⁶ individuals, l^–1, 3–12 mg l^–1, and 50–170 µg l^–1, respectively. Species of Thalassiosiraceae (Bacillariophyta) dominated in the phytoplankton with a subdominance of Chlorococcales in summer. Individual numbers and dry weights of crustacean zooplankton ranged between 1400–6500 individuals m^–3, and 1.2–12 mg m^–3, respectively. The daily mean gross primary production was 970 mg C m^–3 d^–1, and the net production was 660 mg C m^–3 d^–1. Acanthocyclops robustus populations produced 0.2 mg C m^–3 d^–1 as an average, and Bosmina longirostris populations 0.07 mg C m^–3 d^–1. The ecological efficiency between phytoplankton and crustacean zooplankton was 0.03%.     

Diel feeding rhythms and daily food consumption of juvenile Atlantic salmon in the River Alta, northern Norway

Atlantic salmon fry (0+) sampled from the River Alta exhibited only minor differences in stomach content weights and feeding rates throughout diel periods, but feeding rates were generally lowest at night. In contrast, salmon parr (1+ to 3+) had large diel fluctuations in stomach content weight, with the largest weights usually being recorded during the night and early morning. Accordingly, their feeding rates were highest at night. This nocturnal feeding pattern was consistent throughout all sampling occasions, and appeared to reflect a persistent feeding periodicity in the salmon parr. The daily food consumption rates of both fry and parr were highest during midsummer and decreased towards autumn.     

Copepoda – Cladocera – Tunicata: The role of three major mesozooplankton groups in pelagic food webs

Copepods, cladocerans and tunicates form major groups of herbivorous mesozooplankton. The former two are found in fresh and marine waters, while the latter are restricted to marine systems. In the present review, we compile existing ecophysiological knowledge about between-group differences in metabolic and reproductive rates, feeding selectivity and elemental composition. From this, we derive predictions about their impact on the lower trophic levels (phytoplankton and microbial food web) and predictions about their prevalence under different ecological conditions (e.g. nutrient richness, Si : N ratio, phytoplankton size structure and top-down control).     

Littoral microcrustaceans (Cladocera, Copepoda) in a prairie coastal wetland: seasonal abundance and community structure

Seasonal species abundance and community structure of the littoralmicrocrustacean community (Cladocera, Copepoda) in two areas of DeltaMarsh were investigated over the open-water season. Cladoceranabundance in Crescent Pond, with no fish, only invertebrate predatorswas considerably higher than in Blind Channel, with both fish andinvertebrate predators, and where cyclopoid copepods were thedominant microcrustaceans. In both areas, a small number of speciesof planktonic cladocerans characterized the community in spring andearly summer, whereas a diverse array of species of phytophilouscladocerans comprised the community throughout the summer. Daphnia rosea was the most abundant species in the planktoniccommunity in Crescent Pond for the first half of the summer, and Ceriodaphnia dubia was most abundant in the last half. In contrast,no single planktonic cladoceran species was consistently mostabundant in Blind Channel. The sequence of dominant phytophilouscladoceran species observed in Crescent Pond through the season wasChydorus sp. 2, Simocephalus vetulus, Pleuroxusdenticulatus, and Ceriodaphnia dubia, and in Blind Channel,Alona circumfimbriata, Simocephalus vetulus, and Ceriodaphnia dubia. Dominant planktonic and phytophilous copepods inboth areas were Diacyclops thomasi, Acanthocyclops vernalis,Eucyclops agilis, and Macrocyclops albidus. Canonicalcorrespondence analysis revealed differences in community structurebetween areas of the marsh related to turbidity, phytoplanktonbiomass, and soluble reactive phosphorus concentration.     

Littoral microcrustaceans (Cladocera and Copepoda) as indices of recovery of a limed water system

A 7 year study (1992–1998) of littoral microcrustaceans (Cladocera and Copepoda) in the watercourse of the River Rore, South Norway, illustrates that qualitative data on cladocerans and copepods are well suited to indicate the recovery of lakes following liming. Eight limed, two acid and two circum neutral reference lakes, were sampled twice a year (June/July and September/October). In the limed lakes, species associated with neutral lakes have become more common, whereas apparently acid-tolerant species have become rarer. In Lake Rore and Lake Syndle, the two largest limed lakes which exhibited a gradual increase in pH, the changes in species composition indicated that these lakes were about to recover. Species composition in Lake Røynelandsvatn, which has reacidified after liming, first reflected improved water quality, then reverted to dominance by acid-tolerant species. In the remaining lakes, the species composition reflects a fauna which has recovered compared with the preliming situation. There is strong evidence, however, that temporary fluctuations in pH have a negative influence on the speed of recovery, confirming the importance of keeping pH stable.     

Notes on Cladocera and Copepoda from high altitude lakes in the Mount Everest Region (Nepal)

The paper deals with Cladocera and Copepoda species from eight high altitude lakes in the Khumbu area. In all lakes, an endemic known diaptomid of the palearctic genus Arctodiaptomus is found. The dark and large Daphnia tibetana occurs in five of the lakes sampled, characterized by the persistence of the spine in adults (parthenogenetic and ephippial females, males). Apparently, this is an unknown feature of this species. The literature on the diagnostic traits of the different morphs described is reviewed. In addition, a transparent and smaller-sized Daphnia species occurs in two lakes. This is a D. longispina characterized by the absence in adults of the carapace spine (var. aspina Weretschagin, 1911). The presence of these two species is discussed in relation to water transparency, colour, and vertical distribution. Two hypotheses on the evolution of cuticular pigmentation in Daphnia are examined. In addition to these mostly dominant species, a macrothricid also typical of high altitude lakes in the Alps was found (Macrothrix hirsuticornis) together with two cosmopolitan Chydoridae.     

Spatio-temporal patterns in the copepod community in Malangen, Northern Norway

The objective of this study was to identify the key copepodspecies and their life cycles, and provide evidence for anyseasonal and spatial changes in the copepod community in Malangen,a fjord located 30 km to the south of Tromsø in NorthernNorway (69°30'N, 18°21'E). As a result of high levelsof freshwater run-off in May, the fjord became highly stratifiedwith a sharp pycnocline at 10–30 m depth from May to August.The generation patterns of six copepod species are described.Calanusfinmarchicus produced one generation during the spring thatyear, whereas two generations appeared to be produced by bothPseudocalanus acuspes and P.minutus: one in spring (March-June)and the other in autumn (August-December). However, it is uncertainto what extent P.minutus regularly produces a second generation.Two peaks of CI-CIII Metridia spp. were found; there were differencesalong the length of the fjord in the timing of these, but therelative contributions of M.longa and M.lucens are uncertain.Chiridius armatus CI-CIII peaked in abundance in the spring,which indicates that one main generation was produced at theouter station of the fjord. The copepod community in Malangencould be grouped into three entities according to their numericalabundance during the year one group of highly abundant forms,generally with maxima >50 000 individuals m^–3 (C.finmarchicus,Microcalanus sp., Oithona similis , Oithona spinirostris, Acartiasp. and Pseudocalanus spp.), a second group of less abundantspecies with a clear seasonality in abundance, varying from500 to 50 000 individuals m^–3 (M.longa, M.lucens, Calanushyperboreus, Carmatus, Tenwra longicornis, Oncaea sp., Euchaetanorvegica and Scolecithrwella minor), and a third group of 14holoplanktonic species, sporadically occurring in the fjord.The study demonstrates clear gradients in the abundance of fivespecies along the length of the fjord: the recruiting generationof C.finmarchicus occurred in higher abundances at the outerstation in May and June compared to the other inner sites. Laterin the season, the reverse situation appeared, in which thepopulation was more abundant in the inner part of the fjorcCalanw hyperboreus increased abruptly in abundance from lowwinter levels to a maximum in April-May, and declined steadilyduring the season (except at the innermost station). Metridialucens, M.longa and C.armatus demonstrated different distributionpatterns in Malangen that matched their preferred areas of distribution.Both M.lucens and C.armatus are known as oceanic and deep-waterspecies, respectively, and these were prevalent at the two outersites in Malangen. Metridia longa is a more nentic species andwas found in highest numbers at the two innermost sites. Themechanisms for the differences in abundance among these specieswithin the fjord are discussed.