Chrysaora melanaster Brandt, 1835

Morandini, André C. & Marques, Antonio C., 2010, Revision of the genus Chrysaora Péron & Lesueur, 1810 (Cnidaria: Scyphozoa) 2464, Zootaxa 2464, pp. 1-97 : 37-40

Chrysaora melanaster Brandt, 1835

( Figures 44 –49, 79, 91)

Chrysaora melanaster Brandt 1835: 227 (description) [Kamchatka – Russia]. Lesson 1843: 403 (description). Claus 1877: 36 (mention). Haeckel 1880: 515–516 (description) [North Pacific Ocean]. Vanhöffen 1888: 23 (brief description); 49 (distribution). Vanhöffen 1906: 49–50 (brief description), fig. 12 (medusa) [North Pacific Ocean]. Mayer 1910: 580 (synoptic table), fig. 367 (medusa). Bigelow 1913: 90 (mention) [North Pacific Ocean]. Stiasny 1919: 73– 74 (description) [Yokohama – Japan]. Vannucci 1954: 125 (commented that C. melanaster is identical to C. gilberti ). Naumov 1956: 38 (mention, tab.). Kramp 1961: 326–327 (synonymy). Naumov 1961: 63 (key), 64–66 (description), fig. 43 (medusa) [ Russia]. Hamner & Schneider 1986: 172 (tab. 1), 173 (mention) [Bering Sea]. Mills 1987: 67 (mention, key), fig. 3.80 (medusa) [northwest Pacific Ocean]. Larson 1990: 549 (mention, tab. 1), 552 (historical), 552 ( C. melanaster of Fewkes, 1889 = C. fuscescens ), fig1E (medusa, figure reproduced from Brandt 1838) [Bering Sea]. Cairns et al. 1991: 12 (list), 66 (index). Arai 1997: 51 (lack radial muscle), 198 (aggregation), 225 (classification). Brodeur 1998: 13–16, 18 (association with fishes) [Bering Sea]. Wrobel & Mills 1998: 53 (description), 93, 99, 102, 103 (mention). Brodeur, Mills, Overland, Walters & Schumacher 1999: 298, 303 (mention, bloom) [Bering Sea]. Arai 2001: 74 (mention). Mills 2001: 56, 64, 65 (mention, blooms). Purcell & Arai 2001: 34 (mention), 35 (tab. 4). Brodeur, Sugisaki & Hunt 2002: 90–101 (biomass increase) [Bering Sea]. Gershwin & Collins 2002: 128 (mention), 129 (tab. 1), 130 (mention), 131 (absence of quadralinga), 143 (key), fig. 2 (phylogeny). Kubota 2003: 34 (mention). Purcell 2003: 137 (mention). Purcell 2005: 466 (mention, climate effects on blooms) [Bering Sea]. Raskoff, Purcell & Hopcroft 2005: 211 (mention) [Arctic Ocean]. Purcell, Uye & Lo 2007: 154, 156–157, 159–160, 166–167 (mention, blooms). Brodeur, Decker, Ciannelli, Purcell, Bond, Stabeno, Acuna & Hunt Jr. 2008b: 103–111 (population variation) [Bering Sea]. Coyle, Pinchuk, Eisner & Napp 2008: 1780, 1785 (mention, abundance variation) [Bering Sea]. Zavolokin, Glebov & Kosenok 2008: 462–466 (occurrence, distribution) [Bering Sea]. Masuda 2009: 270 (mention). Palomares & Pauly 2009: 13, tab.1 (stock), 15, tab. 2 (growth parameters) [SE Bering Sea]. Purcell 2009: 25, 27, 42 (mention, trophic ecology).

Chrysaora (Polybostricha) melanaster: Brandt 1838: 385–387 (description), Pl. XVI (medusa), Pl. XVII (medusa oral view) [Kamchatka – Russia].

Chrysaora melanaster var. gilberti Mayer 1910: 582–583 (description), fig. 368 (medusa) [non Chrysaora gilberti Kishinouye, 1902 ].

Dactylometra pacifica: Calder 1972: 41 (mention = C. melanaster ) [non Dactylometra pacifica ( Goette, 1886) ].

Holotype specimen. Not available.

Examined material. CASIZ 26232 (~ 9 cm in diameter, 02.iv.1977, 4% formaldehyde solution, 57º46.6’N 162º51.4’W, Bering Sea ); USNM 29762 (~ 17 cm in diameter, 07.vi.1906, 4% formaldehyde solution, 52º14.30’N 174º13’W), USNM 53224 (~ 3 cm in diameter, 21.vii.1969, 4% formaldehyde solution, Coos Bay , Oregon – USA), USNM 53864 (specimens ~4 and 6 cm in diameter, 17.vii.1941, 4% formaldehyde solution, 57ºN 164ºW, Bering Sea), USNM 54328 (~ 25 cm in diameter, 18.vii.1973, 4% formaldehyde solution, Bodega Bay – USA), USNM not-numbered (~ 30 cm in diameter, 16.viii.1987, 70% ethanol, 27 m depth, 54º31.52’N 160º29.87’W, Bering Sea).

Type locality. Kamchatka, Russia.

Distribution. Northern Pacific Ocean (Kamchatka – Russia; Aleutian Islands, Bering Sea, Alaska, Oregon – USA) ( Fig. 79).

Diagnosis. Live and preserved medusae with up to 60 cm in diameter; marginal lappets (adults) rounded, 4 per octant, with canals; tentacles 24 (3 per octant, 2-1-2); quadralinga absent; colouration (adults) exumbrella with whitish background, some specimens with pale radial pattern of brownish lines arising from apical ring; presence of 16 dark radial lines on subumbrella.

Holotype specimen description. No holotype located, and no neotype designated.

Description of other specimens and additional data. Medusa: specimens 3–30 cm in diameter ( Figs 44 –47) (literature reports up to 60 cm); umbrella hemispherical ( Figs 44 –45, 47), flatter in younger specimens (3–6 cm). Exumbrella smooth (note: only preserved specimens studied, not in ideal condition). Colouration of exumbrella usually whitish, with 16 reddish-brown radial lines arising from an apical ring ( Figs 44 –45, 47). Subumbrella with 16 dark radial lines between stomach pouches ( Brandt, 1835; Wrobel & Mills, 1998; Fig. 48). Mesoglea flexible, thicker centrally. Marginal lappets rounded, 4 per octant, with canals of gastrovascular system; lappets of similar size; margin of rhopalar lappets not overlapping (“open rhopalia” condition). Rhopalia 8, without ocelli, in deep clefts; exumbrellar sensory pit deep. Tentacle clefts of same octant aligned. Tentacles 24 (adults), 3 per octant (primary tentacle central, secondary tentacles laterally); 2–3 times longer than umbrellar diameter. Radial and circular musculature not distinguishable. Brachial disc circular. Pillars evident. Quadralinga absent. Subgenital ostia rounded to triangular, 1/4–1/6 of umbrellar diameter. Oral arms up to 6 times longer than umbrellar diameter, V-shaped, with frilled free edges, slightly spirally coiled at distal part. Central stomach circular; margin limited by insertion of radial septa. Stomach pouches 16, width uniform at basal part; tentacular pouches enlarged at 1/5 at distal part. Radial septa thin; rounded at base; straight up to ¼ of margin, then making an “S” (first thinning tentacular pouch, then enlarging it); ending near tentacular base at rhopalar lappet (Fig. 49). Gastric filaments in 4 interradial fields. Gonads encircling gastric filaments, forming a semi-circular ring, heavily folded. Cnidome ( Fig. 91): Specimen USNM 53864, medusa tentacles with holotrichous O-isorhizas [n=10; 13.7–17.6 x 11.7–14.7 µm (mean = 16.17 x 14.11 µm)]; holotrichous aisorhizas [n=10; 5.8–6.8 x 2.9–3.9 µm (mean = 6.07 x 3.03 µm)]; holotrichous A-isorhizas [n=10; 19.6–23.5 x 6.8–8.8 µm (mean = 21.07 x 8.23 µm)]; heterotrichous microbasic rhopaloids [n=10; 14.7–16.6 x 6.8–8.8 µm (mean = 15.56 x 7.45 µm)]; Specimen USNM 54328, medusa tentacles with holotrichous O-isorhizas [n=10; 14.7–15.6 x 11.7–13.7 µm (mean = 14.9 x 12.54 µm)]; holotrichous a-isorhizas [n=10; 5.8–6.8 x 2.9–3.9 µm (mean = 5.97 x 3.13 µm)]; holotrichous A-isorhizas [n=10; 19.6–23.5 x 6.8–8.8 µm (mean = 21.56 x 8.03 µm)]; heterotrichous microbasic rhopaloids [n=10; 11.7–13.7 x 4.9–6.8 µm (mean = 12.84 x 6.47 µm)].

Systematic remarks. Larson (1990) commented on the confusion in identification of North Pacific species of Chrysaora . Many problems derived from misidentifications, probably because of the great variation within the same species and the similarities in colour patterns between different species. Apparently C. melanaster is restricted to cold waters of the North Pacific. The species characteristically has 16 dark radial lines on subumbrella, and a dark radiating pattern over a whitish background on the exumbrella (which fades away in preserved specimens); this pattern is different from that of C. fuscescens . However, colouration unfortunately disappears in preserved specimens. Notably, however, C. melanaster has some gastrovascular canals on the marginal lappets which do not occur in C. fuscescens . The species has many times been confused with C. pacifica , but they can be distinguished by differences in tentacle and lappet numbers. Medusae under this species name appear in several aquaria around the world, but we believe that they are C. pacifica and not C. melanaster .

Biological data. Blooms of the species were recorded for Arctic waters ( Brodeur et al. 1999; 2002).

Etymology. melanaster , in reference to colouration, derived from the Greek melanus (= dark, black) ( Brown 1956). Derived from the Greek melas (= black) and aster (= star) referring to the dark pigmentation pattern over a lighter background ( Wrobel & Mills 1998: 93).