SCIENTIA MARINA 77(2) June 2013, 341-352, Barcelona (Spain) ISSN: 0214-8358 doi: 10.3989/scimar.03815.15A Morphology of the larval stages of a Mediterranean population of the allochthonous Say’s mud crab, Dyspanopeus sayi (Decapoda: Brachyura: Panopeidae) ELENA MARCO-HERRERO 1, GUILLERMO GUERAO 2 and JOSÉ A. CUESTA 1 1 Instituto de Ciencias Marinas de Andalucía (ICMAN), CSIC, Avenida República Saharaui, 2, 11519 Puerto Real, Cádiz, Spain. E-mail: [email protected], [email protected] 2 IRTA, Cultius Aqüàtics, Ctra. Poble Nou km 5.5, 43540 Sant Carles de la Ràpita, Tarragona, Spain. SUMMARY: In this study the complete larval development (including four zoeal stages and a megalopa stage) of Dyspanopeus sayi is described and illustrated in detail based on larvae reared in the laboratory. Ovigerous females were collected in Alfacs Bay, Ebro Delta (NW Mediterranean) where the species was recently introduced. These larval stages were compared with others collected in the plankton from the same area, the larval stages described previously for this species and the larval stages of the two other Panopeidae that inhabit the Iberian Peninsula: Panopeus africanus and Rhithropanopeus harrisii. Differences were found in both zoeal and megalopal larval characters between D. sayi and the other two species, which could raise doubt about their placement in the same family. Keywords: Panopeidae, Dyspanopeus sayi, allochthonous species, larval stages, zoea, megalopa. RESUMEN: MORFOLOGÍA DE LOS ESTADIOS LARVARIOS DE UNA POBLACIÓN MEDITERRÁNEA DEL CANGREJO ALÓCTONO, DYSPANOPEUS SAYI (DECAPODA: BRACHYURA: PANOPEIDAE). – En este estudio se describe e ilustra en detalle el desarrollo larvario (4 estadios zoea y un estadio megalopa) de Dyspanopeus sayi, a partir de larvas cultivadas en el laboratorio. Las hembras ovígeras fueron capturadas en la Bahía de Alfacs (NO Mediterráneo), donde la especie ha sido recientemente introducida. Los estadios larvarios descritos han sido comparados con larvas del plancton capturadas en la misma zona, con descripciones previas de esta especie y con descripciones de los estadios larvarios de las otras dos especies de Panopeidae que habitan en la Península Ibérica: Panopeus africanus y Rhithropanopeus harrisii. Se han encontrado diferencias destacables en algunos caracteres de los estadios, zoea y megalopa, lo cual podría poner en duda la posición de estas especies dentro de la misma familia. Palabras clave: Panopeidae, Dyspanopeus sayi, especie alóctona, estadio larvario, zoea, megalopa. INTRODUCTION 1980, Clark 1986), on the French and Dutch coasts of the North Sea (Vaz et al. 2007), and more recently in The native distribution of Say’s mud crab, Dys- the Black Sea (Micu et al. 2010). It is also present in panopeus sayi (Smith 1869), encompasses the Atlan- the Mediterranean Sea, where it has been collected tic coast of North America from Florida to Canada in Venice, the Marano and Varano lagoons, and in (Nizinski 2003). It is considered an invasive species the Po River Delta (western Adriatic Sea) (Froglia in other parts of the world as a result of human activi- and Speranza 1993, Mizzan 1995, Florio et al. 2008). ties and has probably been accidentally transported The most recent record is from the western Mediter- in ballast water like many other marine invertebrates ranean, which constituted the first record for the coast (Davidson and Simkanin 2012). Currently, outside of of the Iberian Peninsula (Schubart et al. 2012). Figure its native range, D. sayi has been recorded from south- 1 shows the current distribution of Dyspanopeus sayi west England, Queens Dock, Swansea (Wales) (Ingle worldwide. 342 • E. Marco-Herrero et al. FIG 1. – Worldwide distribution of Say’s mud crab Dyspanopeus sayi (Smith, 1869). References: 1, Nizinski (2003); 2, Ingle (1980), Clark (1986); 3, Vaz et al. (2007); 4, Micu et al. (2010); 5, Florio et al. (2008); 6, Froglia and Speranza (1993), ICES (2005); 7, Schubart et al. (2012). Dyspanopeus sayi is a euryhaline and eurythermic MATERIALS AND METHODS species that inhabits estuaries and shallow coastal marine waters (see Schubart et al. 2012). This spe- Three ovigerous females of Dyspanopeus sayi of 16 cies is the second Panopeidae that has established to 18 mm cephalothorax length were collected by beam large populations in estuarine habitats of the Iberian trawls from sandy-muddy bottoms of Alfacs Bay, Ebro Peninsula. The first species was Rhithropanopeus Delta (40°40’N, 0°40’E) covered by the seagrass Cy- harrisii (Gould 1841), reported for the first time in modocea nodosa and the alga Caulerpa prolifera (see the Guadalquivir River (south Atlantic coast of Spain) Pérez and Camp 1986, Fusté 1988), in August 2011. (Cuesta et al. 1991). Another panopeid inhabiting the Specimens were transported to the laboratories of Iberian Peninsula is Panopeus africanus A. Milne- the IRTA (Institut de Recerca i Tecnologia Agroali- Edwards, 1867, which is an endemic crab with a wide mentàries) in Sant Carles de la Ràpita. The females distribution from Angola to Portugal (Rodríguez and were kept in 40-L aquariums. After hatching, actively Paula 1993). swimming zoea I were transferred to 500-mL beakers A number of authors have partially or completely (n=5). A total of 20 larvae were placed in each beaker. studied the larval development of the three species: The subsequent rearing cultures were conducted at a Rodríguez and Paula (1993) described Panopeus af- constant salinity of 34, a temperature of 18±1°C and ricanus; Connolly (1925), Hood (1962), Chamberlain a natural photoperiod of ca. 12 h light per day (early (1962), and Kurata (1970) studied Rhithropanopeus spring condition). After the water had been changed, harrisii and Marco-Herrero et al. (2012) recently re- the Chlorophyceae Tetraselmis chuii and Artemia sp. described the megalopa stage; and Birge (1883), Hy- naupii were provided daily as feed. man (1925), Chamberlain (1957, 1961), Kurata (1970), A qualitative plankton survey was carried out on Clark (2007) and Schubart et al. (2012) studied Dys- 24 and 25 September 2012 in the Alfacs Bay, Ebro panopeus sayi. With the exception of the zoea I, the Delta using a plankton net with a mouth opening of descriptions of the remaining three zoeal stages and 0.25 m2 and mesh size of 250 µm. Samples were taken the megalopa of Dyspanopeus sayi are incomplete, not during daytime, fixed in ethanol (96%), and later detailed and poorly illustrated according to the mod- sorted in the laboratory under a Wild MZ6 compound ern standardization of brachyuran larval descriptions microscope. (Clark et al. 1998). For easier observation of larvae structures and se- In the present study the complete larval develop- tation under microscope, a digestion-stain procedure ment (four zoeal stages and a megalopa) of Dyspan- (Marco-Herrero et al. 2012) was carried out. Initially, opeus sayi is described and illustrated in detail based entire specimens were placed for 10 minutes in a watch on larvae reared in the laboratory. We compared these glass with 2 ml of heated lactic acid. Immediately after, larval stages with those collected in the plankton, and 3 drops of Clorazol Black stain (0.4 g Clorazol Black the larval stages described previously for the other two powder dissolved in 75 ml 70% ethanol) were added to Panopeidae that inhabit the Iberian Peninsula, namely the heated solution. After 5-10 minutes, the specimen P. africanus and R. harrisii. was removed from the solution and placed on a slide SCI. MAR., 77(2), June 2013, 341-352. ISSN 0214-8358 doi: 10.3989/scimar.03815.15A Larval morphology of Dyspanopeus sayi • 343 in Figure 2. The first zoeal stage is redescribed (see Schubart et al. 2012) and only the main differences in subsequent stages are described. Larval description Dyspanopeus sayi (Smith, 1869) Zoea I (Figs 3A, G; 5 A, E; 6 A, E; 7 A, E; 8 A, D) Size: RDL=1863.5±12.4 µm; CL=514.4 ± 31.9 µm; CW=612.5±31.5 µm; RL=786.0±12.2 µm; AL=832.3±50.0 µm; N=10. FIG 2. – Percentage survival and duration of larval stages of Dyspan- Cephalothorax (Fig. 3A, G): dorsal spine straight opeus sayi reared under laboratory conditions (18±1°C and 34±1 salinity). ZI-IV, zoea I-IV; M, megalopa. and well developed with small tubercles over the sur- face; rostral spine straight and slightly longer than dor- with lactic acid, in order to proceed with the dissection sal spine; ventral caparace margin without setae, 1 pair of the appendages. of posterodorsal simple setae; eyes sessile. Drawings and measurements were made using Antennule (Fig. 5A): uniramous, unsegmented and a Wild MZ6 and Zeiss compound microscope with conical; endopod absent; exopod with 4 terminal aes- Nomarski interference, both equipped with a camera thetascs (two long and two shorter) and 1 simple seta. lucida. All measurements were made by an ocular mi- Antenna (Fig. 5E): protopod long, equal in length crometer. Descriptions and measurements of different to rostral spine, with rounded tip and without spines; larval stages were based on at least 10 specimens of exopod reduced to a minute bud with 1 small terminal each stage from culture larvae. In Figure 7 first and simple seta; endopod absent. second maxilliped of zoea I are drawn without exopod, Mandible: incisor and molar process developed; and plumose natatory setae of the maxillipeds exopods palp absent. of zoeae II-IV are drawn truncated. Description and Maxillule (Fig. 6A): coxal endite with 7 plumoden- figures are arranged according to the standards pro- ticulate setae; basial endite with 5 terminal setae (3 cus- posed by Clark et al. (1998). pidate and 2 plumodenticulate); endopod 2-segmented Measurements taken for the zoeal stages were: with 1,2 subterminal + 4 terminal sparsely plumose rostrodorsal length (RDL), distance from the tip of the setae respectively; epipod and exopod setae absent.