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Brachionus calyciflorus showing the measured morphological characters. (A) Anterior medial spine length; (B) anterior lateral spine length; (C) distance between anterior medial spines; (D) distance between anterior lateral spines; (E) distance between anterior lateral and medial spines; (F) dorsal sinus depth; (G) head aperture; (H) lorica width; (I) lorica length; (J) posterior lateral spine length; (K) egg major diameter; (L) egg short diameter.
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Different rotifer stains exhibited remarkably morphological differences which could not be eliminated under laboratory conditions. In the present study, we hypothesized that predation pressure and pollution might be two forces driving morphological differentiation of rotifer. To test this hypothesis, rotifers (Brachionus calyciflorus) belonging to...
Citations
... Rotifers are cosmopolitan micro-invertebrates that play an integral role in planktonic food webs, and are prey to various predators. A number of species have developed strategies to survive predation by induced morphological defences i.e., increasing spine length [22][23][24][25][26][27] and/or behavioural strategies [1,8,15]. Most studies on the response of rotifers to predation risk have focused on behavioural responses before the induction of transgenerational morphological responses and neglected the behavioural response to predators after induction of morphological structures. ...
Predation is a strong species interaction causing severe harm or death to prey. Thus, prey species have evolved various defence strategies to minimize predation risk, which may be immediate (e.g., a change in behaviour) or transgenerational (morphological defence structures). We studied the behaviour of two strains of a rotiferan prey (Brachionus calyciflorus) that differ in their ability to develop morphological defences in response to their predator Asplanchna brightwellii. Using video analysis, we tested: (a) if two strains differ in their response to predator presence and predator cues when both are undefended; (b) whether defended individuals respond to live predators or their cues; and (c) if the morphological defence (large spines) per se has an effect on the swimming behaviour. We found a clear increase in swimming speed for both undefended strains in predator presence. However, the defended specimens responded neither to the predator presence nor to their cues, showing that they behave indifferently to their predator when they are defended. We did not detect an effect of the spines on the swimming behaviour. Our study demonstrates a complex plastic behaviour of the prey, not only in the presence of their predator, but also with respect to their defence status.
... Rotifers are cosmopolitan micro-invertebrates that play an integral role in planktonic food webs, and are prey to various predators. A number of species have developed strategies to survive predation by induced morphological defences i.e., increasing spine length [22][23][24][25][26][27] and/or behavioural strategies [1,8,15]. Most studies on the response of rotifers to predation risk have focused on behavioural responses before the induction of transgenerational morphological responses and neglected the behavioural response to predators after induction of morphological structures. ...
Predation is a strong species interaction causing severe harm or death to prey. Thus, prey species have evolved various defence strategies to minimize predation risk, which may be immediate (e.g., a change in behaviour) or transgenerational (morphological defence structures). We studied the behaviour of two strains of a rotiferan prey (Brachionus calyciflorus) that differ in their ability to develop morphological defences in response to their predator Asplanchna brightwellii. Using video analysis, we tested: (a) if two strains differ in their response to predator presence and predator cues when both are undefended; (b) whether defended individuals respond to live predators or their cues; and (c) if the morphological defence (large spines) per se has an effect on the swimming behaviour. We found a clear increase in swimming speed for both undefended strains in predator presence. However, the defended specimens responded neither to the predator presence nor to their cues, showing that they behave indifferently to their predator when they are defended. We did not detect an effect of the spines on the swimming behaviour. Our study demonstrates a complex plastic behaviour of the prey, not only in the presence of their predator, but also with respect to their defence status.
... Mercury poisoning has been observed in cattle grazing within a 5 km radius of a coal-fired power plant (Mahajan et al., 2012). Coal ash pollution may also affect natural selection on rotifer morphology (Xue et al., 2017). Rotifers, like many other zooplankton species, are known for their phenotypic plasticity as an adaptive response to environmental change (Garza-Mouriño et al., 2005;Sanoamuang, 1993). ...
... Rotifers, like many other zooplankton species, are known for their phenotypic plasticity as an adaptive response to environmental change (Garza-Mouriño et al., 2005;Sanoamuang, 1993). Therefore, rotifers in lakes polluted by coal ash effluent may have smaller bodies, as they require less energy to survive (Cattaneo et al., 1998), and lay larger eggs, which would ensure neonate survival (Xue et al., 2017). ...
Coal combustion generates almost 40% of world's electricity. However, it also produces 1.1 billion tons of coal combustion residues (CCR) annually, half of which end up in landfills. Although current regulations require proper lining and monitoring programs, the ubiquitous old, abandoned landfills are often not lined nor included in these programs. In addition, the total number of coal ash disposal sites and their status in the world is unknown. Therefore, this article reviews the environmental damage caused by CCR and three commonly used risk assessment methodologies: leaching assessment, groundwater assessment, and toxicity testing.
Leaching methods are usually the first step in coal ash risk assessment, however, a large number of methods with different parameters make a comparison of data difficult. Groundwater pollution is commonly detected near coal ash disposal sites, but other anthropogenic activities may also exist nearby. Therefore, multivariate statistical methods and isotope traces should be used to differentiate between different sources of pollution. So far, both stable (δ¹⁸O, δD, δ¹¹B, δ³⁴S, δ⁷Li) and radiogenic (⁸⁷Sr/⁸⁶Sr, ²⁰⁶Pb/²⁰⁷Pb) isotopes have been successfully used as coal ash pollution tracers. Coal ash also negatively affects biota, reduces the diversity of organisms, affects children's health, and increases the risk for developing various diseases. Toxicity studies are great for early screening of coal ash safety; however, they provide no insights into mechanisms causing the adverse effects.
Future directions are also proposed, such as the development of new ‘low-level’ detection methods for coal ash pollution and sustainable and selective method for recovery of critical elements.
... Gilbert (2010) reported that the development of normal-appearing females (rotifer from Brachionus species) is favored when food quality is acceptable; otherwise, the females tend to be smaller and cannot produce cysts. Ying-Hao et al. (2017) reported that rotifers develop a stable, long, lateral posterior spine and relatively small body size in habitats with high predation pressure. Also, the previous authors reported that rotifers collected from polluted habitats exhibit smaller body sizes than specimens from unpolluted habitats. ...
Morphological alterations in zooplankton are induced by exposure to hazardous materials in the environment. These alterations in the body are excellent indicators of adverse effects at the (sub) individual and population levels. These changes might be undetectable within a population in the first generation; however, it was recently documented that alterations are more frequent in the subsequent generations. Because of this, we revised scientific literature that reported malformations in cladocerans, copepods, oligochaetes, and rotifers caused by diverse toxicants when organisms were exposed either in the laboratory or in natural conditions. From an environmental perspective, we focused on the importance of morphological alterations in zooplankton, the most likely causes, and their consequences. Furthermore, the present article shows that alterations of the normal morphology could be used as consistent biomarkers, but further research requires discriminating the influence of natural behavior and the consequences of exposure to toxic compounds.
... For example, a large amount ecotoxicological tests have used zooplankton species as models (e.g., Daphnia water fleas and Brachionus rotifers) to define toxicological thresholds for various types of chemicals (Uriarte and Villate 2004). However, few studies investigated morphological response of zooplankton species to water pollution in the wild (except Xue et al. 2017), while most studies used controlled conditions in a laboratory (Karlsson and Winder 2018;Kang et al. 2019). The complex response to pollution is a major cause hampering field studies, as body size and other functional morphological traits could be simultaneously affected by multiple interacting factors, such as food source, prey and predation, and stressors derived from mixed pollution (Xue et al. 2017). ...
... However, few studies investigated morphological response of zooplankton species to water pollution in the wild (except Xue et al. 2017), while most studies used controlled conditions in a laboratory (Karlsson and Winder 2018;Kang et al. 2019). The complex response to pollution is a major cause hampering field studies, as body size and other functional morphological traits could be simultaneously affected by multiple interacting factors, such as food source, prey and predation, and stressors derived from mixed pollution (Xue et al. 2017). ...
... The herbivorous rotifer species Brachionus calyciflorus is one of the most widespread rotifers globally, and such worldwide distribution comes with enormous multiple-layer variation including morphology in differed environments (Xiang et al. 2016;Papakostas et al. 2016). Survival strategies of B. calyciflorus under environmental challenges have been investigated at multiple levels (Declerck and Papakostas 2017), among which morphological variation of spine length and body size was evidenced as the most sensitive and visualized parameters (Gama-Flores et al. 2007;Zhang et al. 2013;Xue et al. 2017). Body size usually determines the trophic position in food webs, while spine length is a typical prey defense morphological feature (Xue et al. 2017). ...
Various types of pollutants derived from rapid industrialization and urbanization have largely threaten biodiversity and functioning of freshwater ecosystems globally. Morphological plasticity, especially body size-associated traits, is considered as functional response to water pollution in species, as such changes are often directly related to functioning of freshwater ecosystems through dynamics of food webs. However, detailed dynamics of pollution impacts on morphological plasticity remain largely unknown, particularly in the wild. Here, we used the model planktonic rotifer Brachionus calyciflorus to assess morphological response to chemical pollution in a river reach disturbed by sewage discharges. Multiple analyses showed dynamic morphological response to water pollution in wild B. calyciflorus populations. The distance between anterior lateral spines, lorica length and egg short diameter were the most sensitive morphological indicators to water pollution, while spine length was stable in varied pollution conditions. Interestingly, body size and egg size were increased with accentuated water pollution, suggesting that wild populations maintain fitness by increasing feeding efficiency and reducing vulnerability to predation and ensure survival by producing large newborns in polluted environments. Total ammonia nitrogen was the leading nitrogen pollutant affecting body size, while total phosphorus and elements of Mn and As were the key factors relating to egg size. The results obtained here provide new sights into biological consequences of environmental pollution in the wild, thus advancing our understanding of pollution impacts on structure and functioning of freshwater ecosystems.
... Although our experiments were carried out in the absence of fish kairomones, the higher pelagic fish biomass observed in Cueva Morenilla versus Tinaja lake (Table 1) may have selected shorter spines in K. cochlearis from the former. This change may persist under laboratory conditions because rotifers are known to evolve stable morphological features after long-term local adaptation to their environment (Xue et al., 2017). ...
Organisms with wide environmentally-induced morphological plasticity and cosmopolitan distribution, e.g., the common freshwater rotifer Keratella cochlearis, are ideal models to study the evolution of plastic polymorphisms and the capacity of zooplankton to adapt to local selection conditions. We investigated population-level differences (population-by-environment interaction) in sensitivity to food availability and temperature-induced phenotypic plasticity between two clones of K. cochlearis (Gosse) isolated from neighboring populations in Ruidera Natural Park (Spain) with different trophic statuses: Tinaja (TIN) lake (mesotrophic) and Cueva Morenilla (MOR) lake (eutrophic). Using common-garden experiments, each clone proved to have a different sensitivity to food availability, with substantial phenotypic differences between them. When rotifers grew at moderate temperature (15.6°C), low food levels were more efficiently used by the TIN versus MOR clone, whereas high food levels were more efficiently used by the MOR versus TIN clone. The posterior spine was much longer and the lorica wider in the TIN versus MOR clone, with no difference in lorica length. Phylogenetic analysis based on COI sequences showed that both populations have the same haplotype. This is the first study to show possible local adaptation by a rotifer species to habitats that consistently differ in food availability. We also detected an intriguing deviation from the expected negative relationship between posterior spine length and temperature. Our experimental results indicate that intermediate temperatures may activate the gene responsible for spine elongation in K. cochlearis This suggests that rotifers in nature could use water temperature as proxy signal of a change in predation risk before defense is needed.
... Although rotifers are superior among live food, rotifers possess defensive structures, e.g., long spines, and have the capability to adjust their morphology and behavior to prevent predation (Gilbert, 2014;Xue et al., 2017;Yin et al., 2017;Zhang et al., 2017). For example, Yin et al. (2017) found that B. angularis increased lorica thickness and enhanced lorica hardness in the presence of the predator Asplanchna brightwellii Gosse, while B. calyciflorus developed longer posterolateral spines and increased in body size within the presence of the same predator. ...
... Gilbert (2014) found that Brachionus variabilis Hempel when cultured with Asplanchna girodi Guerne have larger (13%) lorica, longer (30-40%) anterior spines, and longer (150%) posterior spine. B. calyciflorus, which originated from different environments in China, developed stable long posterior lateral spines and smaller body size in the presence of predators including fish, copepods and Asplanchna (Xue et al., 2017). Rotifer Keratella cochlearis (Gosse) species are somewhat special in which they are known to have bidirectional change in spine length, depending on the size of the predator . ...
Due to the expanding world aquaculture production, the demand for high quality and quantity of fish larvae has also increased. Up to date, the bottleneck in larviculture is the stable and ample production of appropriate live food such as rotifers and copepods. Among rotifers, Brachionus plicatilis species complex, which encompasses 15 species with varied sizes ranging from 100 to 400 µm, is commonly used in most hatcheries. The use of B. plicatilis species complex (B. plicatilis, B. koreanus, and B. rotundiformis) in larviculture is reported in several review papers. In this review, we first described rotifer species not classified under B. plicatilis species complex, some of which are already used in larviculture, while some have high potential for use based on their characteristics, life history, and distribution. Rotifers, Brachionus angularis, Brachionus calyciflorus, and Proales similis, are described in detail in comparison with B. plicatilis species complex. Furthermore, we discussed some characteristics of rotifers which can affect their predation.
... In general, polymorphism in rotifers has great relevance because morphological variations can influence life history, population dynamics and ecological interactions (Gilbert, 2017). Moreover, laboratory bioassays demonstrated that environmental pollution of metals can change the size and morphology of rotifers (Ríos-Arana et al. 2007, Xue et al. 2017. ...
Testudinella is a taxon of Rotifera broadly distributed in Brazil. In a recent collection in marginal lakes connected to the Paranapanema River (São Paulo, Brazil), we found specimens of Testudinella mucronata and T. patina with concavities on their lorica. The objective of this study was to describe the concavities observed in individuals of both species and discuss their possible causes. Plankton samples were collected at two sampling stations, in the pelagic (PZ) and littoral (LZ) zones of the Panema and Coqueiral lakes; both of these lakes are ultra-oligotrophic and not polluted. For T. mucronata, 4% of individuals with concavities were found in the PZ of Coqueiral lake and 50% in the LZ of Panema lake. In T. patina, the proportion of specimens with concavities corresponded to 34% in the LZ of Panema lake and 17% in PZ of Coqueiral lake. In this study, we discussed that low water temperatures, predation events and/or recent hatching are factors that may justify the concavities in the lorica of specimens of our work.
Adaptation to different ecological niches is considered one of the main drivers of species diversification, also in cryptic species complexes, notwithstanding their morphological stasis. We here review all the published information on ecological differentiation within cryptic species complexes within the phylum Rotifera. We found 177 instances of cryptic species identified genetically, published in 101 papers. Only a subset of the papers contained available information on ecological differences and only for two of the 54 known complexes, namely Brachionus calyciflorus s.l. and Brachionus plicatilis s.l., sufficient data were available for analyses of ecological differences. For the B. calyciflorus complex, B. fernandoi consistently occurred at a significantly lower temperature than the other species in the complex; no differences were found for other environmental variables. For the B. plicatilis complex, B. paranguensis occurred in waters with higher pH than the other species; no differences were found for other environmental variables. These results, even if preliminary and based on scattered information, reveal that adaptation to different ecological niches exists also between closely related species. Our aim is to showcase this interesting field of research spurring further detailed studies to focus on the mechanisms of ecological speciation using rotifer cryptic species as a model system.
