Long-term changes in the population of Eurytemora affinis (Copepoda,Calanoida) in the Gironde estuary (1978–1992)

Long-term changes in the population of Eurytemora affinis were investigated during 15 years (1978–1992) at a fixed station in the Gironde estuary (South West France). Total numbers, sex-ratio, % ovigerous females, proportion of copepodites and clutch-size were taken into account and their long-term distribution was related to temperature, river flow, salinity, suspended matter and chlorophyll a concentrations after the seasonal effect was removed for all variables.There was a great decrease of the river flow during the period of investigation, due to a general deficit in pluviosity. On the contrary, the general trend for salinity was an increase from 1978 to 1992. The same pattern was observed for chlorophyll, indicating an intrusion of marine phytoplankton. Water temperature increased significantly during the study period, following the general increase in air temperature observed in the area. For the suspended particulate matter (SPM), an increase was observed between 1978 and 1981–1982, then a very sharp decrease occurred from 1984 onwards.Numbers of E. affinis were inversely correlated with temperature and salinity, and positively correlated with the river flow. E. affinis was negatively correlated with chlorophyll concentration because of the covariation with salinity. No clear long-term trend was observed for the sex-ratio. A significant correlation was found between females carrying egg-sacs and SPM concentration, probably due to a decrease of the predation pressure in very turbid waters. The percentages of copepodites tended to decrease with time and were inversely correlated with temperature. Clutch-size significantly decreased during the 15-year period. This trend was mainly explained by temperature and salinity.It is concluded that, in the absence of strong human alteration in the Gironde estuary the long-term distribution of zooplankton can be explained by the natural environmental variability. The dominant factors are the river flow which governs the movement of the populations along the estuary and the temperature which influences the reproductive processes. Any change in climate will have consequences on the pelagic community.     

Calanoida (Copepoda) species composition changes in the reservoirs of São Paulo State (Brazil) in the last twenty years

A sampling programme was undertaken to monitor the total carbon (C) and total nitrogen (N) content of suspended matter in a small undisturbed upland drainage basin in the New Territories of Hong Kong. Mean C and N contents were 12.9% and 1.0%, respectively, for 132 samples. Samples collected under stable flow conditions had mean C and N contents of 12.8% and 1.1%, respectively. Stormflow samples had mean C and N values of 12.9% and 1.0%, respectively, which were very similar to the levels observed under stable flow conditions. The mean C: N ratios of 12.5 and 13.4 for stable flow and stormflow also reveal little variation with hydrologic conditions. When all the data is considered, little seasonal variation was observed in C and N. However, in winter there is a significant difference in C and N content between stable and stormflow samples. When C and N are plotted against water level, the scattergraphs suggest that as stage increases the percentage of C and N in the suspended matter declines. Scattergraphs of C and N against suspended sediment concentration reveal a negative association. This may reflect the dominance of inorganic sediments produced by erosion processes during rainfall.     

Records of the Siberian–Beringian Genus Nordodiaptomus (Copepoda,Calanoida) from the European Part of Russia

Biology Bulletin - The morphological characters and biology of the copepod genus Nordodiaptomus Wilson from temporary waterbodies lying in the northern part of the middle taiga belt of the Komi...     

Identification guide to some Diaptomid species (Crustacea,Copepoda, Calanoida,Diaptomidae) of “de la Plata” River Basin (South America)

An identification guide is presented for species of calanoid copepod family Diaptomidae from “de la Plata” River Basin (Argentina, Brazil, Bolivia, Paraguay and Uruguay). It was based on material collected during the summer and winter of 2010 from 43 sites across the eastern part and the lower stretches of this basin, the second largest in South America and the fourth in the world. The guide contains identification keys and species diagnoses for males and females, richly supported by scanning electronic micrographs and/or line drawings of 19 species. It also includes some general remarks on the taxonomy and phylogenetic relationships of these species. The key was adjusted to be useful for these species only, with separate keys for each sex, and is the first for females of South America. One species classified herein as incertae sedis was not included in the analysis. At least ten other species have previously been recorded in the basin but were not present in our samples. This is the first attempt to compile comprehensive taxonomic information on this group of copepods in this region, and it is expected to become a useful tool for biologists and young taxonomists interested in the crustacean biota of the Neotropical region.     

Does Acartia clausi (Copepoda: Calanoida) use an area-restricted search foraging strategy to find food?

The swimming behavior of Acartia clausi within small aquaria containing phytoplankton was videotaped, along with unfed controls. From these videos, aspects such as swimming speed, distance traveled, and 2D (horizontal, X, and vertical, Z) headings were then measured from over 75000 X Z positional data in order to quantify their swimming functional response. There was generally no significant difference in swimming behavior between different food levels, although there was a large difference between feeding and unfed controls. Because feeding bouts moved the copepods a short distance at a slow speed, net vertical displacement decreased as feeding-bout frequency increased. Non-feeding individuals showed longer periods of sinking, interspersed with longer-distance, high-speed jumps, which displaced them farther distances than filter-feeding copepods over the same time interval. For both fed and unfed control copepods, a 1D unbiased random walk was adequate to describe their displacement over these very short time periods (10 s). This behavior is consistent with an area-restricted search foraging strategy. The net vertical displacements predicted by combining the experimental data with a 1D random walk model suggest that A. clausi would be retained within even small 10 cm phytoplankton patches long enough to fill their gut. However, copepods outside of phytoplankton patches must rely on other means to find patches of food greater than 50 cm apart. Potentially, knowledge of a copepod's swimming functional response could enable predictions about the typical spatial and temporal patchiness of its food in situ.     

Dormancy in the Copepoda — an overview

Dormancy affects copepods in their anatomy, physiology, genetics, population biology, community ecology, evolution and local and geographic distribution. It is known from freeliving representatives of three copepod taxa, namely the Harpacticoida, Cyclopoida and Calanoida. Species showing dormancy occur in various realms and habitats, both freshwater and marine, being benthic, planktic or ice-dwelling. Depending on the taxon, dormancy occurs at various times of the year, prevailing in higher and temperate latitudes. Copepod dormancy is expressed in various ontogenetic stages, such as resting eggs, arrested larval development, juvenile and adult encystment, or arrested development of nonencysted copepodids or adults. Ecologically, dormancy is an energy saving trait, allowing the individual to bridge periods of environmental harshness. Adverse environmental conditions could be abiotic (e.g. desiccation, temperature, oxygen availability) or biotic in nature (e.g. food availability, predation). Diapause s. str. is initiated, maintained and terminated by triggering factors (e.g. photoperiod, temperature, chemical cues, population density/physiological factors). The dormant state and emergence patterns directly affect reproduction, population dynamics, community composition, coexistence and distribution of copepods, as well as the phenology of their predators and living food items. Populations having dormancy, in most cases belong to and affect communities of two realms: the water column and the bottom. Dormant stages may provide means for dispersal as well as for staying in special localities. The variability of dormancy permits flexible and complex life histories. Dormancy is subjected to and on the other hand affects copepod evolution.     

Vergleichende Untersuchungen über Morphologie,Taxonomie und geographische Verbreitung der Arten der Gattung Tropodiaptomus Kiefer (Copepoda: Calanoida) aus asiatischen Binnengewässern

Revision of the Asiatic representatives of the genus Tropodiaptomus. Of the 20 names hitherto given for species or varieties, one is a nomen nudum, 9 forms are characterized insufficiently and, hence, their taxonomical position is still uncertain, 10 species are redescribed and illustrated, and 2 taxa have proved to be new to science.

     

The effect of food concentration on the gut clearance time of Pseudocalanus minutus Krøyer (Calanoida: Copepoda)

The effect of food concentration on gut clearance time of a pelagic copepod, Pseudocalanus minutus Krøyer, was investigated. Gut clearance time was estimated from ingestion rate and gut content pigment of copepods which were continuously fed during experiments. The time estimated by this method was longer than that estimated by evacuation of gut content pigment in filtered sea water by a factor of 1.3 to 2.6. Gut clearance time showed fluctuation with food concentration over 1.6 to 3.3. h, whereas food category had little effect on the time.     

Tolerance, optimum ranges, and ecological requirements of freshwater Ostracoda (Crustacea) in Lake Aladağ (Bolu, Turkey)

During monthly sampling from Lake Alada (Bolu, Turkey) between April 2003 and June 2004, nine ostracod taxa (Candona candida, Cypridopsis vidua, Darwinula stevensoni, Eucypris virens, Eucypris sp., Heterocypris sp., Limnocythere inopinata, Physocypria kraepelini, and Tonnacypris lutaria) were recorded from seven stations. Physocypria kraepelini was commonly found in the lake while the others were recorded in particular months. UPGMA analyses clustered three groups based on their occurrence. Accordingly, the occurrence of species (C. candida, E. virens, and T. lutaria) was positive and significantly related to each other. Two species, P. kraepelini and D. stevensoni, showed a significant positive relationship with electrical conductivity. A significant negative correlation was found between the occurrence of P. kraepelini and dissolved oxygen, while there was a significant positive correlation between the occurrence of P. kraepelini and turbidity. About 76% of the relationship between species and environmental factors was explained by the first two axes of canonical correspondence analyses (CCA). Temperature and dissolved oxygen were the two most important influences on the species assemblages. All species showed different but high optima and tolerance ranges, corresponding with their cosmopolitan characteristics. These responses may be related to unstable ecological characteristics of Lake Alada, which is often subjected to human activity.     

The hipparions (Mammalia,Equidae) from Gülpinar (Canakkale,Turkey)

The mammalian fauna from Gülpinar (Canakkale, Turkey), dated Turolian, comprises threeHipparion taxa:H. cf.matthewi, H. sp. medium-sized, andH. sp. large. Two metatarsals may represent a fourth taxon or may derive from a different locality. The hipparion material is described here.     

The family Pontellidae (Crustacea: Copepoda) in la Ventosa Bay, Oaxaca, México: systematies and basic ecology

A study on ecological records of planktonic copepods from The Ventosa Bay, Oaxaca, Mexico is presented. Five species were identified: Labidocera acuta, L. lubbockii, Pontella agassizi, P. tenuiremis and Pontellina plumata. The most abundant species was L. acuta and their copepodite stages conforming the 95.7% of Pontellids, followed by L. lubbockii 4.09%; other species were less than one percent. The reproductive success of L. acuta is probably favored by its resistance to the changes in temperature and salinity, because of it is an eurytherme and euryhaline organism. Total density of this family was between 18 and 472 copepods/100 m3 in 1987 and 1988. Nevertheless in 1992 and 1993 the density was between 490 to 123,030 copepods/100 m3. This copepod density increment could be related local phenomenon (upwelling) at the beginning and end of the year.     

Ecological requirements of Ostracoda (Crustacea) in a heavily polluted shallow lake,Lake Yeniçağa (Bolu,Turkey)

Although the area of Lake Yeniça?a is a potential candidate for RAMSAR convention, several anthropogenic factors compromise its biological diversity. This is mostly due to nutrient-rich water released from both point and nonpoint sources. Thirteen ostracod taxa (Candona neglecta, C. candida, Ilyocypris bradyi, Darwinula stevensoni, Cypridopsis vidua, Physocypria kraepelini, Cypria ophtalmica, Prionocypris zenkeri, Eucypris virens, Herpetocypris reptans, Pseudocandona compressa, Fabaeformiscandona fabaeformis Potamocypris cf. fulva) were found during this study. Potamocypris cf. fulva is a new record for the Turkish freshwater ostracod fauna. The first nine of these species have broad geographic ranges, implying high tolerance levels to different environmental variables. Based on the estimated species optima and tolerance levels, two species exhibited higher effective number of occurrences (C. neglecta, and D. stevensoni, respectively) than the other species. Three species (C. neglecta, D. stevensoni, I. bradyi) did not show significant correlation with any environmental variable we used. Both Canonical correspondence (CCA) and Pearson correlation analyses showed that temperature was the most effective predictor of species occurrence, followed by electrical conductivity and redox potential. In contrast, pH and dissolved oxygen of water were the least effective predictors. Approximately 71% of the correlation between community composition and environmental variables was explained by the first axis of the CCA diagram, which had a relatively low (7.7%) cumulative variance of species. The lower (560 μg/l) and the upper (2030 μg/l) levels of ammonia (NH₃) exceeded the limits during winter season. The concentrations of total coliform and Escherichia coli bacteria were measured up to 10 × 10⁷ cfu/ml and 10 × 10³ cfu/ml, respectively. Results of physicochemical measurements, microbiological counts, and species data indicate that water quality of Lake Yeniça?a has been rapidly deteriorated by anthropogenic factors that are the main threat for not only the lake’s aquatic diversity but also human health around the lake.