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Latin american journal of aquatic research

versión On-line ISSN 0718-560X

Lat. Am. J. Aquat. Res. vol.40 no.4 Valparaíso nov. 2012 

Lat. Am. J. Aquat. Res., 40(4): 1090-1093, 2012

Short Communication


First record of the association between Lychnorhiza lucerna (Scyphozoa, Rhizostomeae) and Cyrtograpsus affinis (Decapoda, Varunidae)

Primer registro de la asociación entre Lychnorhiza lucerna (Scyphozoa, Rhizostomeae) y Cyrtograpsus affinis (Decapoda, Varunidae)


Agustín Schiariti1,2, María Paz Sal Moyano1, Diego A. Giberto1,2 & Hermes W. Mianzan1,2

1Instituto de Investigaciones Marinas y Costeras (IIMyC), FCEyN, CONICET Universidad Nacional de Mar del Plata Diagonal J.B. Alberdi 2695, 7600, Mar del Plata, Argentina.
2Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP) Paseo V. Ocampo N°1, Mar del Plata, Argentina

ABSTRACT. We report the association between the jellyfish Lychnorhiza lucerna and the crab Cyrtograpsus affinis. Numerous examples of associations between medusae and brachyurans have been observed in the field and noted in the literature. All of these cases involve medusae of the Class Scyphozoa and crabs belonging to the families Majidae and Portunidae. The presence of three individuals of C. affinis within the subgenital space of L. lucerna constitutes a striking finding since none species of this brachyuran family (Varunidae) has been previously reported associated to scyphomedusae.

Keywords: symbiosis, jellyfish, brachyurans, Rio de la Plata, southwestern Atlantic, Argentina.

RESUMEN. Se reporta la asociación entre la medusa Lychnorhiza lucerna y el cangrejo Cyrtograpsus affinis. Existen numerosos ejemplos de asociaciones entre medusas y brachiuros mencionados en la literatura. Todos ellos involucran a las medusas de la Clase Scyphozoa y a cangrejos pertenecientes a las familias Majidae y Portunidae. La presencia de tres individuos de C. affinis dentro de la cavidad subgenital de L. lucerna es un hecho llamativo dado que, hasta el momento, no se habia reportado a ninguna especie de esta familia de brachiuros (Varunidae) asociada con medusas de la Clase Scyphozoa.

Palabras clave: simbiosis, medusas, braquiuros, Rio de la Plata, Atlántico sudoccidental, Argentina.


Several medusae species have been intensively investigated in recent times within the context of their hypothetical biomass increases and the socioeconomic and environmental problems caused by their mass occurrences (see Purcell et al., 2007; Uye, 2008). In particular, rhizostome medusae have acquired greater importance since species of this taxon are characterized by their frequent outbreaks, and some of them constitute important food resources for several countries (Arai, 1997; Kingsford et al., 2000; Omori & Nakano, 2001). Therefore, there is a need of increasing knowledge about the ecological role they play in marine environments.

Medusae form symbiotic relationships with many species, including small fishes (see references in Arai, 1997), and a broad taxonomic spectrum of invertebrates including cnidarians, platyhelminthes, nema-tods, gastropods, cephalopods, echinoderms, pycno-gonids and crustaceans (e.g. Arai, 1997; Towanda & Thuesen, 2006). These animals may profit from the mobile nature of their hosts, allowing otherwise benthic organisms to access to the benefits of a pelagic lifestyle. On the other hand, any potential advantage seems unlikely for the medusae (Corrington, 1972). Based on these hypothetical effects of one species on the other, these associations have been characterized s commensalism or parasitism (see Towanda & Thuesen, 2006).

The jellyfish Lychnorhiza lucerna Haeckel, 1880 is the most frequent rhizostome medusa inhabiting the coastal waters from southeastern Brazil (22-23°S) to northern Argentina (36-38°S) (Mianzan & Cornelius, 1999), at a point its commercial exploitation is currently under consideration (Schiariti, 2008). L. lucerna adult medusae were observed as host of seven different species including fishes (Chloroscombrus chrysurus and Hemicaranx amblyrhynchus; Morandini, 2003), digenean parasites (Opechona sp.; Morandini et al., 2005), shrimps (Periclimenes pavai; Martinelli et al., 2008), isopods (Synidotea marplatensis, Nogueira & Silva, 2005) and crabs (Libinia ferreirae and L. spinosa; Moreira, 1961; Vaz-Ferreira, 1972; Mianzan et al., 1988; Zamponi, 2002; Nogueira & Haddad, 2005; Santos et al., 2008). In the present work, we report for the first time the association between L. lucerna and Cyrtograpsus affinis Dana, 1851 constituting the first example of a varunid crab in association with medusae.

Lychnorhiza lucerna medusae (n = 306) were collected during March 2006 at the Rio de la Plata Estuary (Argentina-Uruguay) (Fig. 1), during a fishery research cruise performed by the National Fishery Research Institute of Argentina (INIDEP) on board the R/V Capitán Cánepa. Hauls (n = 42) were carried out during daylight using a mini bottom trawl net (2.4 m2 of net mouth, 25 mm mesh at wing, 10 mm mesh at codend). Medusae were measured across the bell diameter (BD, cm ± 0.1) and macroscopically examined for the presence of symbionts (exumbrella, oral arms, oral pillars, gastric cavity, subgenital space and gonads).

Figure 1. Map of the Río de la Plata Estuary showing the distribution of the sampling stations. White dots indicate the stations where Lychnorhiza lucerna were captured. Black dot shows the location of Cyrtograpsus affinis found in association with L. lucerna.

Figura 1. Mapa del estuario del Río de la Plata indicando la distribución de las estaciones de muestreo. Los puntos blancos representan las estaciones donde se capturó Lychnorhiza lucerna. El punto negro representa la estación donde fueron hallados los cangrejos Cyrtograpsus affinis dentro de L. lucerna.

One of the medusae (BD = 22 cm), harbored three adult specimens of the crab Cyrtograpsus affinis and one of the spider crab Libinia spinosa. The C. affinis specimens were adult hard-shelled, including two ovigerous females (6.0 and 7.3 mm carapace width, CW) and a male (8.0 mm CW), while the L. spinosa was a hard-shelled adult male (4.5 cm CW). All individuals were found within the subgenital space of the medusa, each one occupying an individual subgenital pocket. No crabs were observed within the bottom trawl bycatch.

Cyrtograpsus affinis is a crab of relative small size and a common sublittoral species in the Rio de la Plata Estuary (Boschi, 1964; Spivak & Cuesta, 2000; Giberto, 2008). L. lucerna, the largest planktonic species in the region, it is a rhizostome medusa with a mean diameter of 15-25 cm and up to 50 cm. Its occurrence is restricted to the warmer months (December-May) (Schiariti, 2008).

Having indirect development with a planktonic larval stage, the adult forms of C. affinis are confined entirely to the bottom (Spivak & Cuesta, 2000). Therefore, there are two alternatives to explain how the crab attains the medusa; either the medusa must descend to the substratum at least occasionally or else one of the larval stages of the crab must seek shelter within the medusa (Corrington, 1972).

Phillips et al. (1969), demonstrated that crabs enter in association with medusae when the jellyfish is near the bottom. Sal Moyano et al. (2012) observed that the moulting period from larval stages to adult crabs of the spider crab L. spinosa is longer even than the life span of medusae in the region. In addition, the presence of L. spinosa specimens bearing the anemone Antholoba cf. achates within L. lucerna suggest the crabs is capable of attaining the medusa after its larval stage has concluded (Schiariti pers. obs.). Based on these indirect evidences, it is reasonable to suppose the crabs have attained their host while the medusae have descended to the substratum near the bottom. In fact, the presence of medusae (L. lucerna and Chrysaora lactea) near the bottom has been observed in Rio de la Plata Estuary by Álvarez-Colombo et al. (2003) and Cabreira et al. (2006), reinforcing this possibility.

Although in this study no crab larvae were found within L. lucerna, the presence of crab larval stages in association with scyphomedusae was reported several times (Corrington, 1972; Graham, 1994; Towanda & Thuesen, 2006), even for the same medusa species (Nogueira & Haddad, 2005). Furthermore, small juveniles and recently moulted individuals of L. spinosa have been found within L. lucerna. Therefore, the presence of the most vulnerable life stages (larvae, juveniles, and soft-shell individuals) in association with L. lucerna indicates this species may constitute one of the few available structures in the pelagic realm of the Rio de la Plata Estuary giving protection against predation.

Numerous examples of associations between scyphomedusae and brachyurans have been observed in the field and noted in the literature. All of these cases involve medusae of the Class Scyphozoa and crabs belonging to the families Majidae and Portunidae (see references in Nogueira & Haddad, 2005; Towanda & Thuesen, 2006). Therefore, the presence of three specimens of C. affinis within L. lucerna constitutes the finding of a new brachyuran family (Varunidae) in association to medusae of the Class Scyphozoa. Nevertheless, the small number of animals requires further studies with distinguish symbionts from accidental occurrences.


We are grateful to Dr. María Andrea Gavio for her help and comments on the ms. This work was partially supported by FONCyT PICT-2007 N°02200. This is INIDEP contribution N°1738.


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Received: 4 January 2012; Accepted: 12 October 2012.

Corresponding author: Agustin Schiariti (

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