The lack of data concerning the morphology of male cladocerans greatly impedes our understanding of the systematics of cladocerans. This is because the differentiation of males is of significant importance for disting...The lack of data concerning the morphology of male cladocerans greatly impedes our understanding of the systematics of cladocerans. This is because the differentiation of males is of significant importance for distinguishing closely related species. Simocephalus himalayensis himalayensis Chiang & Chen, 1974 (Cladocera, Simocephalus) is an endemic cladoceran species in the Tibetan plateau, China. To date, no information has been available regarding the morphology and biology of its males. In this study, we provide the morphological and biological data of the males that were produced in laboratory populations. The male individuals are about 1.01–1.20 mm long; the margin of antennulae possess two sensory papilla; dorsal valve margin smooth. Two vas deferens are located between the supra-anal angle and the proximal anal teeth. Sperm is round with a diameter of two micrometers. An updated morphological description and reproductive data of the females of this species are also provided.展开更多
Understanding when small- or large-bodied cladocerans dominate zooplankton communities has received considerable debate over the past 50 years. While a large body of research has proposed that large-bodied species are...Understanding when small- or large-bodied cladocerans dominate zooplankton communities has received considerable debate over the past 50 years. While a large body of research has proposed that large-bodied species are superior competitors over small-bodied species, other studies have shown that small-bodied species can dominate at least under some environmental conditions. We tested the hypothesis that dominance by small- and large-bodied cladocerans varied in response to the coupled effects of food supply and temperature. Laboratory experiments with poly- and monocultures of small- and large-bodied cladocerans were performed at three temperatures (16°C, 22°C and 27°C) and with varying amounts of food supply. The results of the experiments showed that the small-bodied species (Ceriodaphnia quadrangula) dominated at low food supply and higher temperature, while the large-bodied species (Daphnia magna and Daphnia pulex) in contrast dominated at lower temperature and higher food supply. Furthermore, although there were variations in the relative biomass of the small- and large-bodied cladocerans in the polycultures, C. quandrangula replaced the two larger Daphnia species when they declined in biomass at low food supply. Species replacement in response to temperature and food supply helped to maintain the relatively constant level of total cladoceran biomass in the polycultures which was the most pronounced at the intermediate temperature. We suggest that the observed changes in dominance were similar to facilitative replacement rather than competitive exclusion. Physiological processes such as clearance rates can help to promote the succession of large- and small- bodied populations within a community along gradients of temperature and food availability.展开更多
Ten years of monthly dataset of cladoceran (Diaphanosoma sp., Bosmina spp., Ceriodaphnia spp.) density in Lake Kinneret (spatially scattered lake sampling stations), Israel, was studied with the aim of searching impac...Ten years of monthly dataset of cladoceran (Diaphanosoma sp., Bosmina spp., Ceriodaphnia spp.) density in Lake Kinneret (spatially scattered lake sampling stations), Israel, was studied with the aim of searching impact factors controlling their dynamics. Statistical regressions indicated that out of several environmental factors (among others, non-pyrrhophyte algal biomass, invertebrate predation) only temperature factor was relevant. Additional speculative assumptions of zooplanktivore fish predation suggest this factor as a significant impact on cladoceran dynamics.展开更多
Moina eugeniae is the most abundant species in the southwest lagoons of Buenos Aires province. The aim of this work is to study the histology of this cladoceran by light microscopy so as to expand the knowledge of thi...Moina eugeniae is the most abundant species in the southwest lagoons of Buenos Aires province. The aim of this work is to study the histology of this cladoceran by light microscopy so as to expand the knowledge of this species. The parthenogenetic females were fixed in formaldehyde 4%. Sections were cut 3 μm thick and stained with Hematoxylin and Eosin. The intestine has simple cuboidal epithelium with apical projections and the cells have 1 or 2 nucleoli in their nuclei. Two compound eyes were found and no naupliar ocelum. The ovary is saccular and it is presented in a pair at both sides of the intestine with follicles in different states of development. The striated muscle with notorious microfibrills is recognized in antennas, antennules and trunk appendices. This article may represent the first detailed description of the histology of this species.展开更多
The Mouanko mangrove is subjected to major anthropogenic activities such as agriculture, fishing and deforestation, hence information on Cladocerans and Rotifers amongst other aquatic organisms in order to monitor and...The Mouanko mangrove is subjected to major anthropogenic activities such as agriculture, fishing and deforestation, hence information on Cladocerans and Rotifers amongst other aquatic organisms in order to monitor and manage this ecosystem is vital. The aim of this work is to study the physicochemical parameters of the environment that influence the diversity and spatiotemporal distribution of Cladocerans and Rotifers in the mangrove waters of Mouanko. This study was carried out from November 2019 to October 2020 at 8 sampling stations. Both biological and physico-chemical sampling and analyses were done following standard recommendations. The results of the phyico-chemical analyses revealed that the waters of the Mouanko mangroves were slightly basic (7.64 ± 0.71 UC), moderately oxygenated (69.56% ± 14.29%) with low levels of nutrients [ NO <sup>-</sup>2</sub> (0. 06 ± 0.05 mg/L), NH<sup>+</sup>4</sub> (0.39 ± 0.3 mg/L) and PO<sup>3-</sup>4</sub> (up to 0.12 mg/L)] and high values of electrical conductivity (up to 6531.04 μS/cm), salinity (up to 3.71‰). 15 species of Cladocerans and 30 species of Rotifers were identified accounting for a total abundance of 612 ind/L. The species richness was higher in freshwater influenced zones (40 taxa) compared to marinewater influenced zones (17 taxa). Among these species, the Cladocera, Penilia avirostris was the most abundant in marinewater influenced zones (84 ind/L) while the Rotifer, Keratella tecta was the most abundant in freshwater influenced zones (64 ind/L). Shannon-Weaver’s diversity and Pielou’s equitability indices indicated that freshwater influenced zones host a diverse community with a tendency towards equi-partition of species while marinewater influenced zones revealed the opposite. The low levels of organic pollution indicator variables recorded and the high diversity of the freshwater influenced zones population studied attested to the low level of anthropization in this environment. High salinity and electrical conductivity values influence the distribution of these organisms.展开更多
基金Supported by the National Natural Science Foundation of China (No.31071880,31030059)National Key Laboratory of Freshwater Ecology and Biotechnology of China (No.2009FB11)Hangzhou Key Laboratory for Animal Adaptation and Evolution,Hangzhou Normal University (No.2010100333T05)
文摘The lack of data concerning the morphology of male cladocerans greatly impedes our understanding of the systematics of cladocerans. This is because the differentiation of males is of significant importance for distinguishing closely related species. Simocephalus himalayensis himalayensis Chiang & Chen, 1974 (Cladocera, Simocephalus) is an endemic cladoceran species in the Tibetan plateau, China. To date, no information has been available regarding the morphology and biology of its males. In this study, we provide the morphological and biological data of the males that were produced in laboratory populations. The male individuals are about 1.01–1.20 mm long; the margin of antennulae possess two sensory papilla; dorsal valve margin smooth. Two vas deferens are located between the supra-anal angle and the proximal anal teeth. Sperm is round with a diameter of two micrometers. An updated morphological description and reproductive data of the females of this species are also provided.
文摘Understanding when small- or large-bodied cladocerans dominate zooplankton communities has received considerable debate over the past 50 years. While a large body of research has proposed that large-bodied species are superior competitors over small-bodied species, other studies have shown that small-bodied species can dominate at least under some environmental conditions. We tested the hypothesis that dominance by small- and large-bodied cladocerans varied in response to the coupled effects of food supply and temperature. Laboratory experiments with poly- and monocultures of small- and large-bodied cladocerans were performed at three temperatures (16°C, 22°C and 27°C) and with varying amounts of food supply. The results of the experiments showed that the small-bodied species (Ceriodaphnia quadrangula) dominated at low food supply and higher temperature, while the large-bodied species (Daphnia magna and Daphnia pulex) in contrast dominated at lower temperature and higher food supply. Furthermore, although there were variations in the relative biomass of the small- and large-bodied cladocerans in the polycultures, C. quandrangula replaced the two larger Daphnia species when they declined in biomass at low food supply. Species replacement in response to temperature and food supply helped to maintain the relatively constant level of total cladoceran biomass in the polycultures which was the most pronounced at the intermediate temperature. We suggest that the observed changes in dominance were similar to facilitative replacement rather than competitive exclusion. Physiological processes such as clearance rates can help to promote the succession of large- and small- bodied populations within a community along gradients of temperature and food availability.
文摘Ten years of monthly dataset of cladoceran (Diaphanosoma sp., Bosmina spp., Ceriodaphnia spp.) density in Lake Kinneret (spatially scattered lake sampling stations), Israel, was studied with the aim of searching impact factors controlling their dynamics. Statistical regressions indicated that out of several environmental factors (among others, non-pyrrhophyte algal biomass, invertebrate predation) only temperature factor was relevant. Additional speculative assumptions of zooplanktivore fish predation suggest this factor as a significant impact on cladoceran dynamics.
文摘Moina eugeniae is the most abundant species in the southwest lagoons of Buenos Aires province. The aim of this work is to study the histology of this cladoceran by light microscopy so as to expand the knowledge of this species. The parthenogenetic females were fixed in formaldehyde 4%. Sections were cut 3 μm thick and stained with Hematoxylin and Eosin. The intestine has simple cuboidal epithelium with apical projections and the cells have 1 or 2 nucleoli in their nuclei. Two compound eyes were found and no naupliar ocelum. The ovary is saccular and it is presented in a pair at both sides of the intestine with follicles in different states of development. The striated muscle with notorious microfibrills is recognized in antennas, antennules and trunk appendices. This article may represent the first detailed description of the histology of this species.
文摘The Mouanko mangrove is subjected to major anthropogenic activities such as agriculture, fishing and deforestation, hence information on Cladocerans and Rotifers amongst other aquatic organisms in order to monitor and manage this ecosystem is vital. The aim of this work is to study the physicochemical parameters of the environment that influence the diversity and spatiotemporal distribution of Cladocerans and Rotifers in the mangrove waters of Mouanko. This study was carried out from November 2019 to October 2020 at 8 sampling stations. Both biological and physico-chemical sampling and analyses were done following standard recommendations. The results of the phyico-chemical analyses revealed that the waters of the Mouanko mangroves were slightly basic (7.64 ± 0.71 UC), moderately oxygenated (69.56% ± 14.29%) with low levels of nutrients [ NO <sup>-</sup>2</sub> (0. 06 ± 0.05 mg/L), NH<sup>+</sup>4</sub> (0.39 ± 0.3 mg/L) and PO<sup>3-</sup>4</sub> (up to 0.12 mg/L)] and high values of electrical conductivity (up to 6531.04 μS/cm), salinity (up to 3.71‰). 15 species of Cladocerans and 30 species of Rotifers were identified accounting for a total abundance of 612 ind/L. The species richness was higher in freshwater influenced zones (40 taxa) compared to marinewater influenced zones (17 taxa). Among these species, the Cladocera, Penilia avirostris was the most abundant in marinewater influenced zones (84 ind/L) while the Rotifer, Keratella tecta was the most abundant in freshwater influenced zones (64 ind/L). Shannon-Weaver’s diversity and Pielou’s equitability indices indicated that freshwater influenced zones host a diverse community with a tendency towards equi-partition of species while marinewater influenced zones revealed the opposite. The low levels of organic pollution indicator variables recorded and the high diversity of the freshwater influenced zones population studied attested to the low level of anthropization in this environment. High salinity and electrical conductivity values influence the distribution of these organisms.
