Notas / Notes


A synthesis of known Iberian localities for Craspedacusta sowerbii Lankester, 1880 (Cnidaria: Hydrozoa): new record for Spain from low Guadalquivir River

J. L. Medina-Gavilán1 & M. M. González-Duarte2, *

1 Sociedad de Estudios Ambientales (SOCEAMB). C/ Perú, 4, 2ª planta. 41100. Coria del Río (Sevilla), Spain. ORCID iD:

2 Instituto Universitario de Investigación Marina (INMAR), Campus de Excelencia Internacional/Global del Mar (CEIMAR), Department of Biology, University of Cádiz. Avda. República Saharaui s/n. 11510. Puerto Real, (Cádiz), Spain. ORCID iD:

* Author for correspondence:



Alien invasive species are one of the major threats to biodiversity. Particularly, cnidarian species are frequently spread far from their native areas, through human activities. Indeed, many hydroids have been successfully transported as fouling on ship hulls, in ballast waters and as fauna associated with the commercial traffic of other aquatic species. Craspedacusta sowerbii Lankester, 1880 (Hydrozoa: Olindiidae) is the most widely distributed freshwater medusa around the world. This hydrozoan species is probably considered native to the Yangtze valley (China) and invasive in freshwater systems worldwide. In this note, we report the presence of an established population of C. sowerbii from the low Guadalquivir River (western Andalusia, southwestern Spain) and provide the environmental data associated with its occurrence. The spatial distribution of C. sowerbii in the Iberian Peninsula is still poorly studied and most information is derived from regional academic publications, technical reports of limited access, naturalists’ observations or press news on environmental issues. Therefore, all sparse Iberian records for this species have been revised and presented here. This note contributes to know its distribution in the Iberian Peninsula, an important preliminary step to later assess the impact of this invasive species on the Iberian ecosystems.

Key words: alien invasive species; Hydrozoa; Olindiidae; Craspedacusta; Iberian Peninsula; chorological review; Guadalquivir River; Mediterranean seasonal stream.



Una síntesis de las localidades ibéricas conocidas para Craspedacusta sowerbii Lankester, 1880 (Cnidaria: Hydrozoa): nuevo registro para España procedente de la vega del Guadalquivir

Las especies exóticas invasoras son una de las mayores amenazas para la biodiversidad. Particularmente, las especies de cnidarios son frecuentemente dispersadas lejos de sus áreas de origen por mediación de actividades humanas. Así, muchos hidrozoos han sido exitosamente transportados en las aguas de lastre, fijadas en los cascos de los barcos y como fauna asociada al tráfico comercial de otras especies acuáticas. Craspedacusta sowerbii Lankester, 1880 (Hydrozoa: Olindiidae) es la medusa de agua dulce más ampliamente distribuida en el planeta. Esta especie de hidrozoo es considerada probablemente nativa del valle del Yangtze (China) e invasora en ambientes epicontinentales de prácticamente todo el mundo. En esta nota, señalamos la presencia de una población de C. sowerbii establecida en el bajo Guadalquivir (Andalucía Occidental, Suroeste de España) y proporcionamos los datos ambientales asociados con su ocurrencia. La distribución espacial de C. sowerbii en la Península Ibérica está aún poco estudiada y la mayoría de la información proviene de publicaciones académicas regionales, informes técnicos de limitado acceso, observaciones puntuales de naturalistas o noticias de prensa sobre cuestiones ambientales. Por tanto, se han revisado estas fuentes para presentar reunidos todos los registros conocidos sobre esta especie en la Península Ibérica. Esta nota contribuye al conocimiento de su distribución en la Península Ibérica, un importante paso previo para evaluar posteriormente el impacto de esta especie invasora en los ecosistemas ibéricos.

Palabras clave: especies exóticas invasoras; Hydrozoa; Olindiidae; Craspedacusta; Península Ibérica; revisión corológica; Río Guadalquivir; arroyo estacional mediterráneo.


Recibido/Received: 20/11/2017; Aceptado/Accepted: 6/06/2018; Publicado en línea/Published online: 28/08/2018

Cómo citar este artículo/Citation: Medina-Gavilán, J. L. & González-Duarte, M. M. 2018. A synthesis of known Iberian localities for Craspedacusta sowerbii Lankester, 1880 (Cnidaria: Hydrozoa): new record for Spain from low Guadalquivir River. Graellsia, 74(2): e072.

Copyright: © 2018 SAM y CSIC. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License.



Craspedacusta sowerbii Lankester, 1880 (Fig. 1) is a hydrozoan species belonging to the family Olindiidae and characterized for inhabiting inland water environments (Jankowski et al., 2008). The life cycle of this species include both a benthic polyp and a free-swimming medusa stages. The polyps are inconspicuous, minute and without tentacles. Medusa has an umbrella of 10–20 mm in wide, broad and well-developed velum with a large manubrium extending beyond the umbrella margin. The statocysts are within elongated vesicles enclosed in velum (Bouillon et al., 2004). Craspedacusta sowerbii has a cosmopolitan distribution, colonizing all continents apart from Antarctica; actually, it is the most widely distributed freshwater medusa (reviewed in Dumont, 1994 and Jankowski et al., 2008).

Fig. 1.Craspedacusta sowerbii sampled in Sietearroyos River (Villaverde del Río, Seville).
Fig. 1.Craspedacusta sowerbii muestreada en el río Sietearroyos (Villaverde del Río, Sevilla).


Within the genus Craspedacusta Lankester, 1880, more than ten species have been originally described (Jankowski, 2001). However, the lack of a systematic revision at world level has not yet resolved the main question about the number of valid species in Craspedacusta and further molecular data are needed before to may conclude this issue (Fritz et al., 2009; Zhang et al., 2009; Karaouzas et al., 2015). Eastern Asia seems to be the center of diversity for Craspedacusta, showing the highest concentration of species (Jankowski, 2001; Zhang et al., 2009). Moreover, from the classical works of Sowerby (1941) and Kramp (1950), the idea of a putative center of origin in China for Craspedacusta continues to be a suggestive study hypothesis on the basis of biological and biogeographical indicia (Dumont, 1994), in replacement of its early neotropical ascription (Lankester, 1880). Particularly, C. sowerbii is widely considered native to the Yangtze valley (e.g.: Fritz et al., 2007, 2009; Gasith et al., 2011; Karaouzas et al. 2015), until a conclusive phylogeographical study emerges.

The first description about the existence of C. sowerbii occurred in 1880, at the Royal Botanic Garden of London (Lankester, 1880). This finding already revealed the potential invasiveness of this -species and the importance of human activities as -vectors of its long-distance dispersal. In mainland Europe, C. sowerbii was initially reported in 1901 (Sowerby, 1941). Since then, it was recorded from a rapidly increasing number of localities through the first half of the 20th century, both in artificial and -natural environments (Kramp, 1950). During the last years, published citations on the presence of C. sowerbii in different European countries have increased again (e.g.: Arbaciauskas & Lesutiene, 2005; Lundberg et al., 2005; Pérez-Bote et al., 2006; Fritz et al., 2007; Jacovček-Todorović et al., 2010; Stefani et al., 2010; Gomes-Pereira & Dionísio, 2013; Morpurgo & Alber, 2015; Minchin et al., 2016), with the occurrence of more than one independent colonization event (Karaouzas et al., 2015). It is likely that this scenario will not only be due to a plausible biological reality (i.e.: progressive colonization of new localities), but also to a greater effort of sampling, observation, -monitoring and control of water bodies in relation to exotic species (Cardoso & Free, 2008), together with the phenomenon of universalization of information made possible by new communication technologies (Silva & Roche, 2007).

In the Iberian Peninsula, the first known identification dates back to 1968, when it was recorded in the Sau reservoir (Barcelona) (Margalef, 1977: 246). After fifty years, C. sowerbii is well distributed throughout the Iberian territory, with records in numerous Spanish provinces and several Portuguese districts (Table 1, Fig. 2). Unfortunately, most information about the presence of this invasive species in the Iberian Peninsula is provided by regional academic publications, technical reports of limited access, sparse naturalists’ observations or press news on environmental issues. This circumstance makes it difficult for the scientific community and environmental management institutions to stay informed of the updated distribution of C. sowerbii in this territory. Therefore, the goals of the present work were: (i) to present a synthesis of known Iberian localities for this species, and (ii) to report the presence of an established population of C. sowerbii from the low Guadalquivir River (western Andalusia, southwestern Spain). In addition, environmental data associated with its occurrence are provided.

Table 1.— Revised list of Iberian locations for Craspedacusta sowerbii. AP: academic publication; TR: unpublished technical report; PS: preserved specimen; PN: press news; ON: observation in field by naturalists; (*): no further details in the source.
Tabla 1.— Lista revisada de las localizaciones ibéricas conocidas para Craspedacusta sowerbii. AP: publicación académica; TR: informe técnico; PS: especimen preservado; PN: noticia de prensa; ON: observación por naturalistas; (*): sin más detalles en la fuente.
Year Code in Fig. 2 Locality Province/District Centroid coordinates Habitat Source
1968 6 Pantano de Sau Barcelona 41°58’24’’ N 2°23’08’’ E Reservoir AP (Margalef, 1977)
1977 3 Lago Banyoles Gerona 42°07’30’’ N 2°45’19’’ E Lake AP (Prat, 1979)
1981 37 Barragem do Vilar Viseu 40°57’24’’ N 7°32’19’’ W Reservoir AP (Ferreira, 1985)
1983 36 Barragem da Idanha Castelo Branco 39°57’50’’ N 7°11’48’’ W Reservoir AP (Ferreira, 1985)
1983 21 Río Guarrizas Jaén 38°12’33’’ N 3°34’21’’ W Stream /reservoir AP (Ruiz et al., 1992)
1983 22 Río Yeguas Jaén-Córdoba 38°04’43’’ N 4°13’50’’ W Stream /reservoir AP (Ruiz et al., 1992)
1990 7 Embalse de La Baells Barcelona 42°09’07’’ N 1°52’38’’ E Reservoir AP (Viladrich et al., 1990)
1990 8 Pantano de Fuïves Barcelona 42°04’26’’ N 1°54’11’’ E Reservoir AP (Viladrich et al., 1990)
1994 45 Embalse de San Esteban Orense-Lugo 42°23’45’’ N 7°37’43’’ W Reservoir AP (Cobo & González, 2003)
1995 11 Embalse de Canelles Huesca-Lérida 41°59’04’’ N 0°36’59’’ E Reservoir TR (Montserrat, 2017)
1998 28 Río Hozgarganta Cádiz 36°28’40’’ N 5°30’23’’ W Stream ON
2000 17 Embalse del Cíjara Cáceres-Ciudad Real 39°21’05’’ N 4°55’23’’ W Reservoir ON
2001 31 Barragem de Póvoa e Meadas Portalegre 39°30’25’’ N 7°34’48’’ W Reservoir TR (Ministério do Ambiente e do Ordenamiento do Território, 2001)
2004 20 Embalse de Proserpina Badajoz 38°58’14’’ N 6°21’48’’ W Reservoir AP (Pérez-Bote et al., 2006)
2004 16 Embalse de Peñarroya Ciudad Real 39°02’15’’ N 2°57’59’’ W Reservoir ON
2004 39 Embalse de San Juan Madrid 40°23’03’’ N 4°20’18’’ W Reservoir ON
2004 14 Huerta Lugar Valencia 39°13’59’’ N 0°55’47’’ W Reservoir SP (GBIF, 2017)
2004 15 Barranco del Betún Valencia 39°09’05’’ N 0°39’40’’ W Reservoir SP (GBIF, 2017)
2005 25 Pantano de La Breña Córdoba 37°50’33’’ N 5°02’43’’ W Reservoir PN (Diario de Córdoba, 16/10/2005)
2005 29 Río Guadiaro Málaga 36°32’51’’ N 5°22’00’’ W Stream ON
2006 26 Río Sietearroyos Sevilla 37°37’23’’ N 5°53’13’’ W Stream AP (Present Study)
2004 42 Embalse de Añarbe Navarra-Guipúzcoa 43°13’07’’ N 1°52’41’’ W Reservoir AP (Fraile et al., 2008)
2008 12 Parque Samà Tarragona 41°06’22’’ N 1°01’14’’ E Artificial pond ON
2008 27 Río Guadiamar Sevilla 37°31’50’’ N 6°11’26’’ W Stream ON
2009 5 Río Fluvíá Gerona 42°08’18’’ N 2°26’58’’ E Artificial pond PN (Diari de Gerona, 25/08/2009)
2009 4 Río Llierca Gerona 42°14’01’’ N 2°36’30’’ E Stream PN (Diari de Gerona, 25/08/2009)
2009 40 Embalse de Alcorlo Guadalajara 41°01’22’’ N 3°01’24’’ W Reservoir TR (Asociación de Pescadores por la Conservación de los Ríos, 2011)
2009 10 Laguna de Montcortés Lérida 42°19’50’’ N 0°59’41’’ E Lake AP (Oscoz et al., 2010)
2009 46 Río Dorna Lugo 42°56’21’ N 7°32’47’’ W Artificial pond PN (El Progreso, 23/10/2009)
2009 43 Presa de Etxebarri Vizcaya 43°15’06’’ N 2°52’46’’ W Reservoir TR (Ministerio de Medio Ambiente, y Medio Rural y Marino, 2009)
2010 24 Embalse del Guadalmellato Córdoba 38°03’45’’ N 4°40’56’’ W Reservoir ON
2011 33 Barragem do Cabril Castelo Branco-Leiria 39°56’21’’ N 8°07’27’’ W Reservoir PN (Sol, 22/09/2011)
2011 34 Ribeira da Isna Castelo Branco 39°47’46’’ N 7°57’09’’ W Reservoir PN (Sol, 22/09/2011)
2011 35 Ribeira do Alvito (Alvito) Castelo Branco 39°49’26’’ N 7°47’53’’ W Reservoir PN (Sol, 22/09/2011)
2011 23 Embalse de Quéntar Granada 37°12’33’’ N 3°26’07’’ W Reservoir PN (Ideal, 12/08/2011; ed. Granada)
2012 30 Monte da Rocha Beja 37°42’56’’ N 8°17’29’’ W Reservoir AP (Gomes-Pereira & Dionísio, 2013)
2012 1 Lago de la Sorrera Gerona 42°17’18’’ N 3°11’39’’ E Lake ON
2009 43 Embalse de Aranzelai Vizcaya 43°14’46’’ N 2°51’13’’ W Reservoir AP (Rallo & García-Arberas, 2012)
2012 13 Embalse de Ulldecona Castellón 40°40’36’’ N 0°13’52’’ E Reservoir TR (Confederación Hidrográfica del Júcar, 2013)
2013 19 Río Salor Cáceres 39°21’26’’ N 6°17’35’’ W Stream ON
2013 2 Río Orlina Gerona 42°20’12’’ N 3°00’53’’ E Stream TR (Campos et al., 2013)
2014 18 Río Guadalemar Badajoz 39°05’13’’ N 4°54’40’’ W Reservoir * TR (Consejería de Medio Ambiente y Rural, Políticas Agrarias y Territorio, 2014)
2014 32 Barragem de Castelo do Bode Santarém 39°34’25’’ N 8°15’42’’ W Reservoir AP (Rodrigues e Silva, 2015)
2014 12 Riudoms Tarragona 41°08’21’’ N 1°03’15’’ E Artificial pond * AP (Ortiz & Merseburger, 2014)
2015 9 Riera de Mura Barcelona 41°43’15’’ N 1°52’51’’ E Stream ON
2015 38 Río Águeda Salamanca 40°31’24’’ N 6°28’42’’ W Reservoir TR (Salvador Vilariño, 2015)
2015 35 Ribeira do Alvito (Cerejeira) Castelo Branco 39°48’35’’ N 7°45’10’’ W Reservoir ON
2015 41 Embalse de la Cuerda del Pozo Soria 41°51°05’’ N 2°44’30’’ W Reservoir TR (Salvador Vilariño, 2015)
2015 9 Río Cardener Barcelona 41°43’15’’ N 1°49’48’’ E Stream ON
2016 44 Embalse de Valparaíso Zamora 41°58’52’’ N 6°17’35’’ W Reservoir ON

Fig. 2.— Distribution of Craspedacusta sowerbii in the Iberian Peninsula, from published and unpublished recordings. Localities are numbered in the Table 1. Presence data are expressed in 10x10 UTM squares; in black, present study. Grey lines define administrative units: provinces (Spain) and districts (Portugal).
Fig. 2.— Distribución de Craspedacusta sowerbii en la Península Ibérica, a partir de registros publicados e inéditos. Las localidades se enumeran en la Tabla 1. Los datos de presencia se expresan en cuadrículas UTM 10x10; en negro, el presente estudio. Las líneas grises definen las unidades administrativas: provincias (España) y distritos (Portugal).


Iberian Distribution. To our knowledge, C. sowerbii has been detected at least in 50 localities from 26 Spanish provinces and 6 Portuguese districts (Table 1, Fig. 2). All annotated records occurred in the bell-shaped jellyfish stage, which must be taken into account as a possible factor of underestimation about its real distribution in Spain. Indeed, the presence of C. sowerbii is usually ignored when the organism is only present as a polyp (Duggan & Eastwood, 2012).

Lentic waters define the characteristic biotope of C. sowerbii (Jankowski, 2001), which explains that reservoirs and lakes were the dominant habitat in the Iberian Peninsula (74%). Medusae were also frequent in temporary rivers (22%), where inhabit ponds and backwaters from middle to low courses (Table 1). In these environments, the absence of strong currents and the remarkable increase of the water temperature during the summer favour polyp fixation and medusa budding respectively (De Vries, 1992).

Warm temperature, low salinity and high dissolved organic matter have been interpreted as some of the main environmental factors favouring the development of C. sowerbii medusae (Zhang et al., 2016; Caputo et al., 2018). Unfortunately, the autoecology of this species is still little explored in the Iberian Peninsula and limnological data associated to its records are uncommon. Nevertheless, these scarce data suggest that C. sowerbii prefers mesotrophic lentic water-bodies and it is usually found in calm, freshwater reservoirs, lakes or pounds connected to river systems, with a maximum depth of 10 m and summer temperature above 15°C. The occurrence of medusae is between July-November, but they could be absent during several consecutive years (Ferreira, 1985; Ruiz et al., 1992; Pérez-Bote et al., 2006; Fraile et al., 2008; Gomes-Pereira & Dionísio, 2013; Montserrat, 2017).

Low Guadalquivir River. On August 19th 2006, a population of C. sowerbii was found at Sietearroyos River, in Villaverde del Río, Seville, southwestern Spain (37°37’23’’ N -5°53’13’’ W). Specimens were identified according to macromorphological diagnostic characters reviewed by Jankowski (2001) (Fig. 1). This locality has been monitored since then, having detected medusa blooms during most summers of the last 12 years. It is the first documented record of C. sowerbii from low Guadalquivir and also the first published for western Andalusia.

Sietearroyos is a seasonal Mediterranean stream, direct tributary of the Guadalquivir River and one of the few courses of the province that maintain water throughout the year. During summer, including the driest years, the lower and middle course have permanent waters with a marked influence of the Guadalquivir in their confluence, while the upper course only retains points with isolated stagnant water-bodies or weakly connected to each other with very low flows. As a whole, the lower course is integrated in an alluvial-plain geomorphological unit with deep and fertile soils, accompanied by a deciduous riparian forest (Nerio oleandri-Populetum albae) within a cropland landscape matrix. On the other hand, the upper course is enclosed in a narrow valley excavated on micaschistous bedrock, embedded within an agroforestry mosaic with open sclerophyll vegetation (Flueggeion tinctoriae and Oleo-Ceratonion). Particularly, C. sowerbii population inhabits the middle-upper course of the stream, in a system of shallow ponds that form a single water-body of meandering topology, with a total length of 200 m, maximum width of 15 m and depth up to 3 m (Fig. 3). This zone is located at altitude of 33 m above sea level, separated 8.6 km from the confluence with the Guadalquivir River and freely exposed to direct sunlight throughout the day. Its main physicochemical water parameters associated with the occurrence of C. sowerbii are listed in the Table 2.

Table 2.— Field instantaneous measurements of physicochemical water parameters of ecological interest for Craspedacusta sowerbii in the study area, through a standard year.
Tabla 2.— Mediciones instantáneas de parámetros fisicoquímicos de interés ecológico para Craspedacusta sowerbii en el área de estudio, a lo largo de un año típico.
Parameter Value
Water temperature  
Winter 9.5 °C
Spring 18 °C
Summer 22.5 °C
Fall 18 °C
pH 7-8
Conductivity 550 - 1500 mS/cm

Fig. 3.— Habitat of Craspedacusta sowerbii in Sietearroyos River: quiet, shallow open ponds at the middle-upper course, on rocky substrate.
Fig. 3.— Hábitat de Craspedacusta sowerbii en el río Sietearroyos: pozas despejadas, someras y de aguas tranquilas en el tramo medio-alto de su curso, sobre sustrato rocoso.


Water temperature is a key factor in jellyfish blooms (Purcell, 2005; Prieto et al., 2010). In particular, the polyps of C. sowerbii release medusae at a threshold of 21°C (Folino-Rorem et al., 2016), which is consistent with summer temperature in the study area (Table 2). Alkaline levels of pH recorded in Sietearroyos were similar to others reported for the Iberian Peninsula (Ruiz et al., 1992; Ferreira, 1985; Pérez-Bote et al., 2006) or zones with comparable latitude in Europe (Karaouzas et al., 2015). Nevertheless, records in pH from 6.5 (Litton, 1984; Fraile et al., 2008) to more than 8.5 (Raposeiro et al., 2011; Kozuharov et al., 2017) indicate the wide range of pH tolerance for this species. Analogously, values of electrical conductivity in Sietearroyos are also included within the wide range of values reported in the literature for this species: from 60–70 µS/cm2 (Fraile et al., 2008) to 1260–1340 µS/cm2 (Ruiz et al., 1992), in the Iberian Peninsula. However, as a surrogate of salinity, values of electrical conductivity would be expected low in optimal habitats for C. sowerbii medusae (Zhang et al., 2016). Moreover, measurements of water quality reveal high values of salinity from July to October (28.5–61.2 mg/l Na+) downstream of the sample point (41503 DMA Station, Hydrographic Confederation of the Guadalquivir Basin), in spite of freshwater nature of this species.

Craspedacusta sowerbii is considered an invasive species in freshwater systems worldwide, which has established populations in natural, as well as artificial and human-modified habitats (Dumont, 1994; Jankowski et al., 2008; Duggan & Eastwood, 2012). Its wide range of sexual and asexual reproductive strategies makes it an efficient invader. Furthermore, the life cycle of this species includes an encysted phase and it can remain dormant for many years (Bouillon et al., 2004). This characteristic makes this species a perfect invader, allowing withstand by long periods of extreme environmental conditions and facilitating the anthropogenic transport (Jankowski, 2001). Several dispersal vectors have been suggested to explain the cosmopolitan pattern of C. sowerbii, all them associated with the larval (frustule) and resting stages (cysts): water transfer, ship drift, use of alluvial sands for the construction of hydraulic infrastructures, malpractice in aquarofilia, introduction of fish and aquatic invertebrates for sports and commercial purposes, natural movements of wetland birds, importation of aquatic plants, etc. (Turquin, 2010; Fraire-Pacheco et al., 2017). Indeed, several invasive fish species (Alburnus alburnus Linnaeus, 1758; Ameliurus melas Rafinesque, 1820; Lepomis gibbosus Linnaeus, 1758) coexist at the study pools, which are frequented by fishers. Nevertheless, it is also necessary to consider the hypothesis of the spontaneous entry of C. sowerbii from the Guadalquivir River, since this is a natural route of introduction of exotic species in the area (Encina et al., 2006). Moreover, in dry years in which the disruption between water-bodies from upper course and the Guadalquivir are more pronounced, medusa blooms were not usually observed (e.g.: 2016, 2017).

Craspedacusta sowerbii is classified by the European Commission as an alien species of high impact in the European freshwaters (EASIN, 2017). The predatory impact of C. sowerbii on zooplankton community has been described within natural environments and in the laboratory (Boothroyd et al., 2002; Jankowski et al., 2005; Smith & Alexander 2008). In fact, different authors point out that blooms of C. sowerbii can increase its negative effect on native zooplankton community, alter the aquatic food webs and reduce the dissolved oxygen in water (Jankowski, 2000; Smith & Alexander, 2008; Gasith et al., 2011; Folino-Rorem et al., 2016). Dodson & Cooper (1983) conclude that the size range of prey is about 0.2–2.0 mm, though it can kill, but not eat, preys up to 8.8 mm in length. Thus, the food web effect of C. sowerbii is by reducing the density of other invertebrate predators and increasing the abundance of herbivorous zooplankton.

The loss of biodiversity by the introduction of alien and invasive species could not simply be considered in terms of displacements of some native species in favour of their equivalent newcomers (González-Duarte et al., 2016). All associated fauna and relationships can be finally altered (Byers et al., 2002). The possible ecological, socio-economical and evolutionary implications of the introduction and dispersion of C. sowerbii around the world are far from correctly understood. The impact of this invasive species on Iberian ecosystems is still preliminary, but this study contributes to know its geographic distribution along with some important physicochemical parameters.

Only further molecular analysis will be able to provide additional information about the true origin of this species. In addition, long-term studies of the populations will provide more data about the relationship between the environmental factors and the fluctuations of the population, and the influence of C. soberwii in the trophic web.


The authors thank the editor J. Fernández and the reviewers Dr. M. Álvarez Cobelas and Dr. K. Fraire-Pacheco for their comments that helped to improve this manuscript. Dr. F. Cobo (University of Santiago de Compostela), Dr. Ortiz (Associació per a la Conservació dels Ecosistemes Naturals), D. Cruz (Gemosclera) and S. Infante (Quercus, Associaçao Nacional de Conservaçao da Natureza) contributed with data about the presence of Craspedacusta sowerbii in the Sil river, Francolí river, Lagunas de Ruidera Natural Park and the fluvial beaches of Alvito river, respectively. M. A. Chamizo collaborated gathering information.



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