Carybdea marsupialis

Description: Adult medusa: (Figs. 1 A – D, 5 A – H) Bell sturdy, cuboid, slightly wider than high (BH: DBW ratio less than or equal to 1: 1, Fig. 5 A, B), interradial furrows shallow, highly transparent with few whitish nematocyst warts sparsely scattered on bell from apex (very small warts) to bell margin (big warts along interradial furrows), amount of warts varies between specimens (i. e. some individuals present few or no warts; others have profuse warts); apex, thickened, domed, with slight horizontal constriction at level of gastric phacellae; bell height up to 40.5 mm high, bell width up to 40 mm (DBW). Pedalia (Fig. 5 E), 4, simple, unbranched, flattened, scalpel-shaped, measures approx. 1 / 3 the bell height in length, situated in each interradial corner, with irregularly spaced white nematocyst bands on outer keel of pedalium, smaller warts scatter on outer half of pedalium; in some mature medusae margin of inner keel of pedalium sometimes undulated. Pedalium carrying a single tentacle, tentacles light brownish pink colour when contracted, when extended resemble bead-chains with white nematocyst-battery “ pearls ” on pale pink tentacle “ string ”. Pedalial canal with rectangular knee without any hook or thorn appended on outer knee bend (Fig. 5 F), slightly tapering at the upper end, straight (not bending) throughout the length of the pedalium but slightly curving towards the inner pedalial keel in the middle part, ellipsoid in diameter with sharp outer keels. Rhopalia (Fig. 5 G), 4, suspended within heart-shaped rhopalial niche ostium with triangular upper covering scale, without lower covering scale; some specimens present covering scale with nematocyst mammilation (1 or 2 warts), but not the neotype; approx. 1 / 5 of bell height up from bell margin; rhopalium with 6 eyes (2 median lens eyes + 2 lateral slit eyes + 2 lateral pit eyes). Velarium (Figs. 5 H) with some small nematocyst warts, containing 3 velarial canals per octant (i. e. 6 v. c. / quadrant), slim, sharply pointed tips, deeply forked, slightly lobed with smooth margin, canals flanking frenulum are the simplest, mostly unforked, only few small lobes, middle canals, seldom more than 2 main branches, only single side branches, canals flanking pedalia bases, most complex with 3 to 4 main branches and several side branches. Manubrium (ḵ 1 / 4 BH in length), 4 lobes, cruciform lacking nematocyst warts connected to a small, flat (biconvex lens-shaped) stomach which is connected by narrow, non-conspicuous, perradial mesenteries to the sides of the umbrella; stomach communicates perradially with 4 gastric pockets leading into velarial canals. Gastric phacellae (Fig. 5 C), 4, epaulette-shaped, mounted on 4, conspicuously raised stomach corners; filaments brush-like, tightly bundled, originating from a single stem, deeply branched at some distance from the stalk, with numerous short gastric filaments; phacellae brownish-orange in colour, colour remains after preservation (Figs. 5 C, D). Gonads, 4 pairs, narrow leaf-like, separated by perforated interradial septum, extending from stomach rim to pedalium, tapering at level of rhopalia and towards stomach rim; ripe gonads milky whitish in both sexes. Developmental stages: Development of young medusae to adult stage has been documented herein. We classified the individuals of C. marsupialis captured in Denia (Spain) from June to October 2010 into 6 different developmental stages, using both size and different morphological characters as indicators of the development of the animals. The 6 stages were named from A to F (Figs. 6 A – F). By monitoring the development of small cubomedusae into subsequent stages (Acevedo et al. 2013), we confirmed that they all belong to the same species C. marsupialis. Stage A (MZB 2015 - 4801, n = 10): Although the metamorphosis from polyp to medusa has not been observed and described yet, very small medusae (<2 mm DBW; supposed recently liberated from the polyp) were caught in the field (Denia, Spain) in this study. Initial stage A (Fig. 6 A): whitish-colourless, tetraradial, spheroid to cuboid umbrella with large round warts irregularly dispersed over entire exumbrella; bell height up to 1.4 mm, bell width up to 2.2 mm. Tentacles, 4, without pedalia, resembling pearl-string with white, spherical nematocysts batteries. Velarial canals and rhopaliar niche ostia, not yet developed, rhopalium with 6 eyes (2 median complex lens eyes + 2 lateral slit eyes + 2 lateral pit eyes). No gastric filaments. Stage B (MZB 2015 - 4802, n = 12): Mean bell height (BH) 1.5 (± 1.0) mm, mean bell width (DBW) 2.1 (± 0.7) mm; although an overlap in size with stage A exists, the main difference is the appearance of gastric filaments, 4, one in each stomach corner; velarial canals not yet developed; rhopalial niche with scale, pedalia, 4, begin to develop (Fig. 6 B). Stage C (MZB 2015 - 4803, n = 8): Mean BH 2.1 (± 1.7) mm, mean DBW 3.1 (± 1.6) mm; gastric phacellae, completely developed (Fig. 6 C); velarial canals not yet developed; pedalia, 4, still developing. Stage D (MZB 2015 - 4804, n = 8): Mean BH 4.3 (± 4.2) mm, mean DBW 6.4 (± 3.9) mm; velarial canals, begin to develop (Fig. 6 D); pedalia development completed; gonads, appearance of gonadal tissue along the interradial septum. Stage E (MZB 2015 - 4805, n = 2): Mean BH 15.8 (± 9.1) mm, mean DBW 19.1 (± 10.7) mm; velarial canals and pedalia completely developed; gonads, developing but not yet mature, distinction of sex not yet possible (Fig. 6 E). Stage F (MZB 2015 - 4806, n = 4): Mean BH 23.7 (± 2.1) mm, mean DBW 28.8 (± 2.7) mm; Gonads, mature, sex distinction possible (males: finger-print appearance; females: oocytes) (Fig. 6 F).

Figs. 1 A – D; 5 A – H; 6 A – F; 7 A, C, E Synonyms: A comprehensive survey of the literature yielded the following junior synonyms. Urtica soluta marsupium referens: Plancus 1739: 41 – 42 (description in Latin), Fig. 5; (not valid as first species description under Art. 3 of the International Code of Zoological Nomenclature, which establishes that “ No name or nomenclatural act published before 1 January 1758 enters zoological nomenclature, but information, such as descriptions or illustrations, published before that date may be used ”).

The original texts of Plancus (1739) and Linnaeus (1758) contain brief descriptions of C. marsupialis, and no details of any name-bearing specimen. Moreover, we could not find any evidence to the existence of any type material in the scientific literature reviewed in this publication. In order to properly define this species and stabilize the name according to the definition and rules set forth under Article 75 of the International Code for Zoological Nomenclature (ICZN 1999), we designate specimen MZB 2015 - 1701 from Denia (Spain, NW Mediterranean) deposited in the Natural History Museum of Barcelona (Museu de Ciències Naturals de Barcelona) as the neotype of C. marsupialis, since no holotype, lectotype, syntype, or prior neotype is known to exist.

Diagnosis: Gastric phacellae epaulette shaped, single rooted; Velarial canals 3 per octant; multiple branched; Pedalia knee bend rounded, no appendage. Apex thick, domed, with a constriction at the level of the gastric phacellae.

Remarks: The medusa stage of C. marsupialis can be found in coastal waters (~ 0.5 – 10 meters depth) along sandy beaches with a gentle slope where seagrass meadows (Posidonia oceanica) and green algae (Caulerpa prolifera) coexist on rocky and sandy bottoms in the Mediterranean Sea (Bordehore et al. 2011). It is also common to observe this species in canals or harbours. The medusae have been observed swimming near the surface both during day and night. However, they seem to be more active feeders during the night, preying on zooplankton and ichthyoplankton. They can be observed especially during the night, when attracted to a light source (Acevedo et al. 2013). The sting of C. marsupialis medusae causes a severe pain, a burning sensation, erythematous-vesicular eruption, and local oedema (Peca et al. 1997). Bordehore et al. (2015) described the first published case of systemic effects after contact with this species. When mature, medusae of both sexes aggregate for reproduction around mid-October; spermatozoa are released into the water, and eggs are fertilized inside the female medusae, as has been observed for other species of Carybdea (Studebaker 1972 for C. xaymacana; Matsumoto 1995 for C. rastonii). The animals are ovoviviparous and the fertilized eggs are shed into the water (this study). The complete development of the C. marsupialis polyp stage is not known. In this study we observed planulae settlement and polyp development up to the 2 – 3 tentacle stage, but after several months all polyps died before developing additional tentacles or producing asexual buds. Therefore, asexual reproduction in this species was previously undocumented. However, similarities in polyp development, asexual budding, and metamorphosis described by Studebaker (1972), Stangl et al. (2002), Fisher & Hofmann (2004), and Straehler-Pohl & Jarms (2011) for C. xaymacana (= former C. marsupialis from Puerto Rico) were expected for C. marsupialis. The metamorphosis from polyps to medusae is hypothesized to start around the 1 st – 2 nd week of May in the Western Mediterranean, as tiny medusae (1 – 2 mm DBW) have been caught from around mid-May to July during the 5 - year (2010 – 2015) species monitoring program along the coast of Denia. Adult medusae reproduce in late October to early November, and the last medusae of the season were collected in November. Reported distribution of C. marsupialis: Mediterranean Sea Spain: Denia: between Racons-Molinell River (38 ° 53 ′ 09 ′′ N, 0 ° 02 ′ 14 ′′ E) and 2 km south of Denia harbour (38 ° 50 ′ 55 ′′ N, 0 ° 02 ′ 14 ′′ E) (Bordehore et al. 2011); Catalonia: canals of the harbour in Empuriabrava, Badalona, Sitges, l’Ampolla and Alfacs Bay (LIFE CUBOMED project database, www. cubomed. eu); Southern coast of Spain: Valencia, Gandía, Oliva, Jávea, Sta. Pola, St. Pedro del Pinatar, Almería, Málaga and Cádiz (LIFE CUBOMED project database, www. cubomed. eu). Italy: Tuscany, Ligury (western Italian coast) (Bordehore et al. 2011); Numana harbour (Riviera del Conero, Ancona, Adriatic Sea) (Di Camillo et al. 2006); Fano (Boero & Minelli 1986); Gulf of Venice (Mizzan 1993); Gulf of Trieste in October 1998 (Bettoso 2002). Tunisia: Hammamet beach (Gueroun et al. 2015). Malta: St. George's Bay (Birżebbuġa), Msida, Ta’ Xbiex and other marinas and harbours (Pulis 2015).

Other material examined: Spain: Natural History Museum of Barcelona [Museu de Ciències Naturals de Barcelona; formerly Zoology Museum of Barcelona (MZB)]: Forty four (44) specimens preserved in 4 % formaldehyde solution in seawater, from the same collection location as the neotype, separated into 6 different developmental stages, museum numbers MZB 2015 - 4801 (Stage A), MZB 2015 - 4802 (Stage B), MZB 2015 - 4803 (Stage C), MZB 2015 - 4804 (Stage D), MZB 2015 - 4805 (Stage E), MZB 2015 - 4806 (Stage F), Denia (Spain), collected during August, September, October 2010 and June 2011. United Kingdom: British Natural History Museum, London: 1 specimen preserved in formaldehyde solution (BNHM 1972.5.24.1), S. Italy, Gargano Peninsula, Bay of Campi, collector: P. R. Laming, 1972. USA: Smithsonian Institution National Museum of Natural History (NMNH), Washington: from the Mediterranean, Naples Zoological Station (Italy), no exact sampling location, 1 specimen (USNM 19346), conserved in formaldehyde solution, no sampling date; also from the Mediterranean, Pescara (Italy), 3 specimens (USNM 1155726, 1155728, 1155729), preserved in ethanol, collected by Christina Di Camillo, no sampling date, identified by Bastian Bentlage in 2009.