No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
The expansion continues: Girardia arrives in Africa. First record of Girardia sinensis (Platyhelminthes, Tricladida, Continenticola, Dugesiidae) in Morocco
... Until recently, Girardia was not known from African waters. Benítez-Álvarez et al. (2022) reported the first record of this genus in Morocco, a country in the Palearctic region of Africa. However, there is currently no formal record of Girardia in sub-Saharan Africa. ...
... The current study reports for the firsttime the occurrence of a feral population of Girardia sinensis Chen & Wang, 2015 in South Africa. Originally described from China (Chen et al. 2015), where it may be non-native, G. sinensis is a native of North America, and has subsequently been introduced into many countries, including Australia, Morocco, Spain, Italy, France, Germany and Netherlands (Benítez-Álvarez et al. 2022(Benítez-Álvarez et al. , 2023. Given the difficulties of morphological identification of fissiparous triclads lacking copulatory apparatus (Lázaro and Riutort 2013), the species level identification was confirmed using a fragment of the mitochondrial gene cytochrome oxidase I (COI). ...
... This provides strong support for the assignment of the South African species to G. sinensis. Thus, the current manuscript reports the second record of this cosmopolitan species in Africa (Benítez-Álvarez et al. 2022), and a first from Sub-Saharan Africa. The discovery of this feral population shows the power of citizen and formal science working together (Daniels et al. 2022), as we were alerted to the presence of this population by a citizen scientist. ...
... Representatives of the genus have been reported also from Australia, Japan, and Hawaii (Kawakatsu et al. 1984;Sluys et al. 2005;Sluys, Kawakatsu, and Yamamoto 2010). In addition, records of Girardia in China, Serbia, and Eastern Europe have been published in the past few years (Chen et al. 2015;Ilić et al. 2018; Kanana and Riutort, 2019), and recently the genus has been detected for the rst time in Africa (Benítez-Álvarez et al. 2022). ...
... From this perspective, it is especially worrisome that G. sinensis has recently been detected for the rst time in Africa (Benítez-Álvarez et al. 2022). It is noteworthy that this concerned a region for which our niche modelling already indicated its suitability and that harbours a high diversity of autochthonous species of Dugesia (Leria et al. 2022;Benítez-Álvarez et al. 2023). ...
Freshwater planarians of the genus Girardia have been introduced all over the world, but little is known about the species involved and their possible impact on autochthonous ecosystems. Using molecular phylogenetics and niche modelling under different climatic scenarios we examine the human-induced spread of alien Girardia species from their original areas of distribution in the Americas to other areas. Our results corroborate that Girardia populations spreading worldwide belong to three species: G. dorotocephala , G. sinensis , and G. tigrina . Our study emphasizes that G. sinensis is native to North America and shows that G. dorotocephala has a broader range of introduced localities than previously known. Niche modelling revealed that the three species have a broad range of potential distribution in extensive regions of the Northern Hemisphere. Regardless of the future climatic scenario, their distributional range will increase towards northern Europe, without diminishing the high suitability of regions in the south. Their environmental requirements, being generalists with high suitability for human-modified habitats, and fissiparous reproduction explain their successful colonization. In the Iberian Peninsula, G. tigrina and G. sinensis have extensive areas of high suitability, overlapping with the more limited suitable areas of autochthonous planarians, pointing to potential detrimental effects of Girardia invaders.
Freshwater planarians of the genus Girardia have been introduced all over the world, but little is known about the species involved and their possible impact on autochthonous ecosystems. Using molecular phylogenetics and niche modelling under different climatic scenarios we examine the human-induced spread of alien Girardia species from their original areas of distribution in the Americas to other areas. Our results corroborate that Girardia populations spreading worldwide belong to three species: G. dorotocephala, G. sinensis, and G. tigrina. Our study emphasizes that G. sinensis is native to North America and shows that G. dorotocephala has a broader range of introduced localities than previously known. Niche modelling revealed that the three species have a broad range of potential distribution in extensive regions of the Northern Hemisphere. Regardless of the future climatic scenario, their distributional range will increase towards northern Europe, without diminishing the high suitability of regions in the south. Their environmental requirements, being generalists with high suitability for human-modified habitats, and fissiparous reproduction explain their successful colonization. In the Iberian Peninsula, G. tigrina and G. sinensis have extensive areas of high suitability, overlapping with the more limited suitable areas of autochthonous planarians, pointing to potential detrimental effects of Girardia invaders.
This work presents currently available knowledge on alien species (AS) found in the inland waters of Morocco. The objective is to provide an updated list of alien species and identify the main introduction pathways and possible threats to native biodiversity. The dataset was built from an extensive literature search supplemented by our own research work (published or in progress). The main areas harboring xenodiversity in Moroccan freshwaters correspond to protected areas (e.g., Ramsar Site and SIBE). These areas are currently home to 41 confirmed AS belonging to different taxonomic groups. Fish are the most abundant taxonomic group with 21 species, followed by molluscs (7 species) and arthropods (7 species). The presence of 15 more species was also noticed but considered doubtful. Almost half of these AS were introduced intentionally. They correspond to restocking programs and are likely the most serious threat to native biodiversity through predation, competition, and hybridization. Commercial activities around aquarium and ornamental species appear as the second source favoring colonization by AS. Implementing protective regulations regarding the import of exotic species in Morocco appears very urgent to protect local native diversity. In addition, detecting and monitoring the expansion of AS within the colonized areas and studies improving biological and ecological knowledge seem crucial to mitigate their possible impacts on native communities and preserve Moroccan freshwater ecosystems.
Several species of the freshwater planarian genus Girardia have been introduced into freshwater ecosystems all over the world, but little is known about the actual number of species involved and about possible detrimental effects on autochthonous ecosystems. In the present study, we used molecular phylogenetics and niche modelling under present and future climatic scenarios to examine the human-induced dispersal and spread of alien species of Girardia from their original areas of distribution in the Americas to other parts of the globe. Our results corroborate that the Girardia populations spreading worldwide belong to three species of North American origin: G. dorotocephala , G. sinensis , and G. tigrina . Our study emphasizes that G. sinensis is native to North America, from where it colonised China, as well as Europe, Africa and Australia. It also shows that G. dorotocephala has a broader range of localities where it was introduced than previously known, including Europe and Brazil. Niche modelling revealed that the three colonising species have a broad range of potential distribution in extensive regions of the Northern Hemisphere; regardless of the climatic scenario, in the future, their distributional range will increase towards northern Europe, without diminishing the high suitability of regions in the south. Their environmental requirements, being generalists with high suitability for human-modified habitats, explain their successful colonization. In the Iberian Peninsula, introduced G. tigrina and G. sinensis have extensive areas of high suitability, overlapping with the more limited suitable areas of autochthonous freshwater planarians, pointing to potential detrimental effects of Girardia invaders.
The alien boatman Trichocorixa verticalis verticalis (Hemiptera: Corixidae) is expanding in Morocco This paper updates the presence of the Nearctic "water boatman" Trichocorixa verticalis verticalis in North Africa, showing a new range of the alien species that strongly have increased its distribution area in Morocco since its first record in 2010. Statistical analyses confirm a significant correlation between salinity and abundance of T. v. verticalis, highlighting the halobiont behavior of this invasive species, being this trait one of the main causes of its expansion success in the Atlantic and Mediterra-nean coast of the study area. RESUMEN El chinche acuático invasor Trichocorixa verticalis verticalis (Hemiptera: Corixidae) se está expandiendo en Marruecos Este trabajo actualiza la presencia del "chinche acuático" Nearctico Trichocorixa verticalis verticalis en el norte de África, mostrando un nuevo rango de la especie exótica que ha aumentado considerablemente su área de distribución en Marruecos desde su primer registro en 2010. Los análisis estadísticos confirman una correlación significativa entre la salinidad y la abundancia de T. v. verticalis, destacando el comportamiento halobionte de esta especie invasora, siendo este rasgo una de las principales causas de su éxito de expansión en la costa atlántica y mediterránea del área de estudio. Palabras clave: Trichocorixa verticalis verticalis, insecto acuático, especie exótica, invasión, humedales Ramsar, salinidad, Marruecos Limnetica, 39(1): 49-59 (2020).
The introduction of invasive species, which often differ functionally from the components of the recipient community, generates ecological impacts that propagate along the food web. This review aims to determine how consistent the impacts of aquatic invasions are across taxa and habitats. To that end, we present a global meta-analysis from 151 publications (733 cases), covering a wide range of invaders (primary producers, filter collectors, omnivores and predators), resident aquatic community components (macrophytes, phytoplankton, zooplankton, benthic invertebrates and fish) and habitats (rivers, lakes and estuaries). Our synthesis suggests a strong negative influence of invasive species on the abundance of aquatic communities, particularly macrophytes, zooplankton and fish. In contrast, there was no general evidence for a decrease in species diversity in invaded habitats, suggesting a time lag between rapid abundance changes and local extinctions. Invaded habitats showed increased water turbidity, nitrogen and organic matter concentration, which are related to the capacity of invaders to transform habitats and increase eutrophication. The expansion of invasive macrophytes caused the largest decrease in fish abundance, the filtering activity of filter collectors depleted planktonic communities, omnivores (including both facultative and obligate herbivores) were responsible for the greatest decline in macrophyte abundance, and benthic invertebrates were most negatively affected by the introduction of new predators. These impacts were relatively consistent across habitats and experimental approaches. Based on our results, we propose a framework of positive and negative links between invasive species at four trophic positions and the five different components of recipient communities. This framework incorporates both direct biotic interactions (predation, competition, grazing) and indirect changes to the water physicochemical conditions mediated by invaders (habitat alteration). Considering the strong trophic links that characterize aquatic ecosystems, this framework is relevant to anticipate the far-reaching consequences of biological invasions on the structure and functionality of aquatic ecosystems.
© 2015 John Wiley & Sons Ltd.
Environmental contamination has become an increasing global problem. Different scientific strategies have been developed in order to assess the impact of pollutants on aquatic ecosystems. Planarians are simple organisms with incredible regenerative capacity due to the presence of neoblastos, which are stem cells. They are easy test organisms and inexpensive to grow in the laboratory. These characteristics make planarians suitable model-organisms for studies in various fields, including ecotoxicology. This article presents an overview of biological responses measured in planarians. Nine biological responses measured in planarians were reviewed: 1) histo-cytopathological alterations in planarians; 2) Mobility or behavioral assay; 3) regeneration assay; 4) comet assay; 5) micronucleus assay; 6) chromosome aberration assay; 7) biomarkers in molecular level; 8) sexual reproduction assay; 9) asexual reproduction assay. This review also summarizes the results of ecotoxicological evaluations performed in planarians with metals in different parts of the world. All these measurement possibilities make Planarians good bioindicators. Due to this, planarians have been used to evaluate the toxic, cytotoxic, genotoxic, mutagenic, and teratogenic effects of metals, and also to evaluate the activity of anti-oxidant enzymes. Planarians are also considered excellent model organisms for the study of developmental biology and cell differentiation process of stem cells. Therefore, we conclude that these data contributes to the future establishment of standardized methods in tropical planarians with basis on internationally agreed protocols on biomarker-based monitoring programmes.
Humans have effectively transported thousands of species around the globe and, with accelerated trade; the rate of introductions has increased over time. Aquatic ecosystems seem at particular risk from invasive species because of threats to biodiversity and human needs for water resources. Here, we review some known aspects of aquatic invasive species (AIS) and explore several new questions. We describe impacts of AIS, factors limiting their dispersal, and the role that humans play in transporting AIS. We also review the characteristics of species that should be the greatest threat for future invasions, including those that pave the way for invasions by other species (“invasional meltdown”). Susceptible aquatic communities, such as reservoirs, may serve as stepping stones for invasions of new landscapes. Some microbes disperse long distance, infect new hosts and grow in the external aquatic medium, a process that has consequences for human health. We also discuss the interaction between species invasions and other human impacts (climate change, landscape conversion), as well as the possible connection of invasions with regime shifts in lakes. Since many invaders become permanent features of the environment, we discuss how humans live with invasive species, and conclude with questions for future research.
La présence d'un taxon néarctique, Trichocorixa verticalis verticalis (Fieber, 1851) (Hemiptera, Corixidae) originaire du California, est découverte pour la première fois au nord de l'Afrique et ce au nord-ouest du Maroc. Une description détaillée de sa morphologie, de ses habitats aquatiques ainsi que de ses exigences écologiques est exposée. Les mécanismes d'introduction de cette espèce sont également discutés. Mots clés: Hemiptera, Corixidae, Trichocorixa verticalis verticalis, espèce exotique, mécanismes d'introduction, Maroc. Trichocorixa verticalis verticalis (Fieber, 1851) (Hemiptera, Corixidae): a new exotic species in Morocco Abstract: The presence of the Nearctic taxon, Trichocorixa verticalis verticalis (Fieber, 1851) (Hemiptera, Corixidae), coming from California, is discovered for the first time in the north-west of Morocco, northen Africa. Detailed descriptions of its morphol-ogy, aquatic habitats and environmental requirements are included. The mechanisms of introduction of this species are also discussed. Trichocorixa verticalis verticalis (Fieber, 1851) (Hemiptera, Corixidae): una nueva especie exótica en Marruecos Resumen: Se registra por primera vez para el norte de África y Marruecos la presencia del taxón neártico Trichocorixa vertica-lis verticalis (Fieber, 1851) (Hemiptera, Corixidae) originaria de California. Se expone una descripción detallada de su morfo-logía, de sus hábitats acuáticos, así como de sus exigencias ecológicas y se discuten los mecanismos de introducción de esta especie. Palabras clave: Hemiptera, Corixidae, Trichocorixa verticalis verticalis, especie exótica, mecanismos de introducción, Marrue-cos.
Planarians are a group of free-living platyhelminths (triclads) best-known largely due to long-standing regeneration and pattern formation research. However, the group’s diversity and evolutionary history has been mostly overlooked. A few taxonomists have focused on certain groups, resulting in the description of many species and the establishment of higher-level groups within the Tricladida. However, the scarcity of morphological features precludes inference of phylogenetic relationships among these taxa. The incorporation of molecular markers to study their diversity and phylogenetic relationships has facilitated disentangling many conundrums related to planarians and even allowed their use as phylogeographic model organisms. Here, we present some case examples ranging from delimiting species in an integrative style, and barcoding them, to analysing their evolutionary history on a lower scale to infer processes affecting biodiversity origin, or on a higher scale to understand the genus level or even higher relationships. In many cases, these studies have allowed proposing better classifications and resulted in taxonomical changes. We also explain shortcomings resulting in a lack of resolution or power to apply the most up-to-date data analyses. Next-generation sequencing methodologies may help improve this situation and accelerate their use as model organisms.
Invasions of alien species are considered among the least reversible human impacts, with diversified effects on aquatic ecosystems. Since prevention is the most cost-effective way to avoid biodiversity loss and ecosystem problems, one challenge in ecological research is to understand the limits of the fundamental niche of the species in order to estimate how far invasive species could spread. Trichocorixa verticalis verticalis (Tvv) is a corixid (Hemiptera) originally distributed in North America, but cited as an alien species in three continents. Its impact on native communities is under study, but it is already the dominant species in several saline wetlands and represents a rare example of an aquatic alien insect. This study aims: i) to estimate areas with suitable environmental conditions for Tvv at a global scale, thus identifying potential new zones of invasion; and ii) to test possible changes in this global potential distribution under a climate change scenario. Potential distributions were estimated by applying a multidimensional envelope procedure based on both climatic data, obtained from observed occurrences, and thermal physiological data. Our results suggest Tvv may expand well beyond its current range and find inhabitable conditions in temperate areas along a wide range of latitudes, with an emphasis on coastal areas of Europe, Northern Africa, Argentina, Uruguay, Australia, New Zealand, Myanmar, India, the western boundary between USA and Canada, and areas of the Arabian Peninsula. When considering a future climatic scenario, the suitability area of Tvv showed only limited changes compared with the current potential distribution. These results allow detection of potential contact zones among currently colonized areas and potential areas of invasion. We also identified zones with a high level of suitability that overlap with areas recognized as global hotspots of biodiversity. Finally, we present hypotheses about possible means of spread, focusing on different geographical scales.
Since its introduction in 2001, MrBayes has grown in popularity as a software package for Bayesian phylogenetic inference using Markov chain Monte Carlo (MCMC) methods. With this note, we announce the release of version 3.2, a major upgrade to the latest official release presented in 2003. The new version provides convergence diagnostics and allows multiple analyses to be run in parallel with convergence progress monitored on the fly. The introduction of new proposals and automatic optimization of tuning parameters has improved convergence for many problems. The new version also sports significantly faster likelihood calculations through streaming single-instruction-multiple-data extensions (SSE) and support of the BEAGLE library, allowing likelihood calculations to be delegated to graphics processing units (GPUs) on compatible hardware. Speedup factors range from around 2 with SSE code to more than 50 with BEAGLE for codon problems. Checkpointing across all models allows long runs to be completed even when an analysis is prematurely terminated. New models include relaxed clocks, dating, model averaging across time-reversible substitution models, and support for hard, negative, and partial (backbone) tree constraints. Inference of species trees from gene trees is supported by full incorporation of the Bayesian estimation of species trees (BEST) algorithms. Marginal model likelihoods for Bayes factor tests can be estimated accurately across the entire model space using the stepping stone method. The new version provides more output options than previously, including samples of ancestral states, site rates, site d(N)/d(S) rations, branch rates, and node dates. A wide range of statistics on tree parameters can also be output for visualization in FigTree and compatible software.
The genus Girardia (Platyhelminthes: Tricladida) comprises several species of which some have spread from their original areas of distribution in the Americas to other parts of the globe. Due to great anatomical similarities between species, morphology-based phylogenetic analyses struggled to resolve the affinities between species and species-groups. This problem is exacerbated by the fact that populations of Girardia may show only asexual reproduction by fissiparity and, thus, do not exhibit a copulatory apparatus, which hampers taxonomic identification and extraction of phylogenetic characters. In the present work this problem has been resolved by constructing a molecular phylogeny of the genus. Although our samples do not include representatives of all known species, they cover a large part of the original distributional range of the genus Girardia. Our phylogenetic results suggest the presence of two main clades, which are genetically and karyologically highly differentiated. North and South American nominal G. tigrina actually constitute two sibling species that are not even closely related. The South American form is here described as a new species. The phylogenetic tree brings to light that Girardia arose on the South American portion of Gondwanaland, from which it, subsequently, dispersed to the Nearctic Region, probably more than once.
• Desiccation resistance is a key trait determining the distribution of aquatic insects, their potential for overland dispersal, and survival during drought periods in temporary waterbodies, as well as the spread of invasive species. Passive dispersal by waterbirds is considered to be a key process favouring the spread of invasive species and is more likely to occur for insects with eggs that are resistant to desiccation or gut passage.
• We investigated the hypothesis that the eggs of the alien boatman Trichocorixa verticalis verticalis are resistant to desiccation and digestion and thus able to disperse via waterbirds.
• We conducted experiments to test for egg resistance to desiccation in still air and under moving air conditions, to simulate bird flight. Oviposition on greater flamingo (Phoenicopterus roseus) legs and wetland plants was tested in the laboratory and in the field. Resistance of eggs to simulated gut passage was studied, as was the viability of eggs recovered from Eurasian coot (Fulica atra) droppings in the field.
• Only a fraction of eggs hatched after 8 hr of exposure to still air at 15°C (4% of exposed eggs), and after 2 hr exposure to air flow conditions at 20°C (8%). Oviposition on flamingo legs was confirmed in the laboratory but not in the field. However, oviposition rates were higher on plant stems than on flamingo legs. Digestion simulations showed very low resistance to chemical treatment and no resistance to scarification, and eggs recovered from coot droppings did not hatch.
• Our experiments demonstrated that T. v. verticalis cannot be considered to have eggs resistant to desiccation or gut passage. However, the dispersal of eggs on legs of flamingos or other waterbirds may occur as rare events. This epizoochory of eggs could potentially contribute to the expansion and gene flow of T. v. verticalis around the Mediterranean region.
The genus Girardia Ball, 1974 houses freshwater planarian species and is the second after Dugesia Girard, 1850 within Dugesiidae regarding the number of species. It contains 45 species (Tyler et al. 2006–2019) including three recently described: one from China—Girardia sinensis Chen & Wang 2015 (Chen et al. 2015), and two cave-dwelling planarians from Brasil—Girardia desiderensis Souza & Leal-Zanchet 2016 and Girardia pierremartini Souza & Leal-Zanchet 2016 (Souza et al. 2016).
Regarding the humane use of animals in scientific research, invertebrates are often recommended in toxicological studies. "Freshwater planarians" refers to numerous free-living freshwater members of the Class "Turbellaria" of the phylum Platyhelminthes. This group of invertebrates has received extensive attention from biologists for many years because of their unique biological characteristics, such as the primitive form of the central nervous system and notable capability to regenerate tissues. Using freshwater planarians as test animals in chemical toxicity studies has grown in popularity since the 1960s. Results from various toxicological experiments have collectively suggested that freshwater planarians can serve as not only alternative models for chemical toxicity screenings in laboratories but also as potential bioindicators for the quality of freshwater environments. However, thus far, no standardized battery of tests for conducting toxicological studies that includes freshwater planarians has been proposed. This paper comprehensively reviews the toxicological information obtained from chemically exposed planarians and proposes practical factors for consideration in toxicity experiments with freshwater planarians as test organisms.
Girardia tigrina (Girard, 1850) (Turbellaria, Tricladida, Dugesiidae), a native freshwater triclad of North America, is a widespread species, which has been introduced by human activities into various parts of the world, including Europe. The aim of this paper is to contribute to the knowledge of this species by presenting its frst record and recent distribution in Serbia. Girardia tigrina was recorded in Serbia in 2008 in the lower stretch of the Kolubara River. After this initial fnding, the species was identifed only a few more times, but with low abundance. Its presence only in the northern part of Serbia, in the Danube River and in its proximity, points to the Danube River and its larger tributaries (the South invasive corridor) as the main route of its spread in the country. Our data suggest that G. tigrina should not be considered an invasive species but as an alien species with a minor impact on native communities.
Material is described that contributes to our understanding of the anatomy of 11 species of the genus Girardia Ball, 1974 and the taxonomy of one species of Romankenkius Ball, 1974. Apart from recently collected specimens, the study for the first time details old syntype material that was recovered for the species G. anceps and G. andina, resulting in the first modern description of the last-mentioned species. Relatively recently collected specimens from new sampling sites are described for G. chilla, G. dorotocephala, G. festae, G. paramensis, and G. tigrina. The new records for G. festae considerably enlarge the known geographic range of this species in South America, particularly east of the Andes. It is shown that contrary to the opinion of earlier workers there is some slight, but invariable, anatomical difference between North and South American specimens of G. tigrina, with the Neotropical animals having a much more muscled bursal canal. This slight anatomical difference suggests that the North and South American forms are actually sibling species. Four new Girardia species are described, three for the South American continent (G. avertiginis, G. capacivasa, G. jugosa) and one from Jamaica (G. bursalacertosa). The study confirms earlier conclusions that generally species of Girardia are anatomically very similar and that therefore species recognition can be difficult. It is striking that taxonomic diversity in the Neotropical Region is low, in that the majority of the freshwater planarians belongs to a single genus, viz. Girardia. It is concluded that Romankenkius michaelseni (Böhmig, 1902) is a junior synonym of R. patagonicus (Borelli, 1901).
Biogeographical and taxonomic information on the four non-indigenous freshwater planarians of
Japan is reviewed, viz. Dugesia austroasiatica Kawakatsu, 1985, Girardia tigrina (Girard, 1850), G. dorotocephala (Woodworth, 1897), and Rhodax evelinae? Marcus, 1947. The occurrence of Girardia dorotocephala in Japan is unequivocally demonstrated. New karyological data are presented for populations of D. austroasiatica (chromosome complement: 2x=16, 3x=24), G. tigrina ( 2x=16, 3x=24), and G. dorotocephala (2x=16). The following factors may have facilitated the introduction and subsequent geographical spread of exotic freshwater triclads in Japan: popularization of domestic tropical fish cultures, and culture of exotic aquatic animals for food.
A contribution to the phylogeny and biogeography of the freshwater triclads (Platyhelminthes, Turbellaria)
- I R Ball
Ball, I.R. (1974) A contribution to the phylogeny and biogeography of the freshwater triclads (Platyhelminthes, Turbellaria). In:
Biology of the Turbellaria. McGraw-Hill, New York, New York, pp. 339-401.
A new species of the genus Girardia (Tricladida : Dugesiidae) from China
- X Chen
- Y Chen
- C Wu
- A Wang
Chen, X., Chen, Y., Wu, C. & Wang, A. (2015) A new species of the genus Girardia (Tricladida : Dugesiidae) from China.
Zoological Systematic, 40 (2), 166-178.
https://doi.org/10.11865/zs.20150202