Chrysaora wurlerra, Gershwin, Lisa-Ann & Zeidler, Wolfgang, 2008

Gershwin, Lisa-Ann & Zeidler, Wolfgang, 2008, Some new and previously unrecorded Scyphomedusae (Cnidaria: Scyphozoa) from southern Australian coastal waters, Zootaxa 1744, pp. 1-18 : 11-15

Chrysaora wurlerra , sp. nov.

(Plate 5)

Material examined. Holotype: AM G13681, Nobby Beach, Hawkesbury River, NSW, 33° 33’S 151° 14’E, coll. R. Haddock, 16.10.1968; female (BD 125.9 mm, longest oral arm 92.7 mm).

Paratypes: AM G13682, collected with holotype (40 tentacle stage, unless noted otherwise): five females (BD 72.3 mm with 24 tentacles plus nubs, 76.8 & 77.6 mm with vacuoles, 98 & 114.5 mm) and three males (BD 87.0 mm with 24 tentacles plus nubs, 84.4 & 87 mm). AM G16022, from type locality, 4.i.1972; two males (BD 78.8 mm with 24 tentacles & 106.8 mm). AM G13729, from type locality, 3.viii.1971; four immature specimens (BD 23.7 mm, 8 tentacle stage plus nubs and 43.7, 51.6 & 53.0 mm with 24 tentacles). AM G13683, Manly, Sydney, NSW, no date; female (BD 61.1 mm with eggs, 24 tentacle stage).

Diagnosis. Chrysaora with 40 tentacles, with crescentic row of vacuoles at base of each central tentacle per octant; with tentacles flat and ribbon-like, in conspicuous 2-1-2 arrangement; with oral arms long and tapering; reaching over 125 mm BD.

Description of holotype. Bell much flatter than a hemisphere, with fairly thin jelly, 125.9 mm BD; exumbrella sprinkled with low nematocyst warts, coalescing in center, radiating out toward margin; subumbrella with numerous bumpy nematocyst warts over gastro-genital region, smooth over radial gastric pouches.

Tentacles 40, grouped five per octant, lacking longitudinal muscle ridges, flat and ribbon-like throughout length; issuing from margin between or proximal to margin in 2-1-2 array in three forms; centermost tentacle in each group attached at level of rhopalium, with crescentic row of vacuoles defining attachment point; second and fourth tentacle attached somewhat more peripherally; first and fifth tentacle placed in close proximity to second and fourth, respectively, but issuing from subumbrella under fused lappets. Marginal lappets 32, of two forms; those flanking central tentacle tongue-shaped, angled away from tentacle; those flanking rhopalia bilobed at point of first and fifth tentacles.

Radial gastric pouches 16, of equal width proximally, with 45° bend in peripheral quarter to encompass five tentacles within each tentacular pouch; extending into marginal lappets, with extension of both adjacent tentacular and rhopaliar pouches into bilobed lappets. Radial gastric septa 16, distally running along rhopalial side of first and fifth tentacles, proximally teardrop-shaped with minute lateral diverticula.

Oral arms four, interradial, lacking stiffness, tapering, tending to curve counter-clockwise; moderately speckled with raised nematocyst warts; longest oral arm 92.7 mm. Gonads four, interradial, contained within subumbrellar pouches; genital ostia small, rectangular.

Rhopalia eight, four perradial, four interradial, finger-shaped on gelatinous base attached to body; subumbrellar niche open; exumbrellar sensory pore broadly rounded, blind-ending.

Color in life unknown.

Variation. Not all the paratypes exhibit the tentacle-base vacuoles observable in the holotype. However, the other characters are constant. It is interesting to note from the growth series that the tentacles issue from the subumbrella while the lappets are still fused. This is observable not only with the first and fifth tentacles in those specimens in which these tentacles are emerging, but also in the second and fourth tentacles in the smallest specimen (G13729).

Etymology. From the Aboriginal wur (= fire) and lerra (= river), in reference to “stinging water” ( Reed 1977), as “sea nettles” (i.e., Chrysaora spp.) tend to give very sharp stings; noun in apposition.

Distribution. Apart from one specimen collected at Manly, all other specimens came from the type locality, Nobby Beach, Hawkesbury River, New South Wales. Notably, this species seems to be primarily an estuarine form whereas C. southcotti is more coastal/oceanic. Whether this is an artifact of the small sample size of C. wurlerra , or due to a real difference in habitat preference, is unknown.

Curiously, most of the specimens were collected in spring. It is unclear how old they were, but it is possible that they were strobilated in the winter and were still growing when captured inasmuch as many displayed at least some immature characters (e.g., 24 tentacles). If so, this would further separate them from C. southcotti , which begins to appear about December-January, reaches peak numbers about February, and is gone by mid-late autumn.

PLATE 5. Chrysaora wurlerra , sp. nov., holotype. A. Whole animal, subumbrellar view. B. Tentacle base vacuoles (arrows). C. Blind exumbrellar rhopaliar pit (arrow).

Remarks. Chrysaora wurlerra is immediately distinguished from its congeners in possessing vacuoles at the base of the central tentacle. It bears a superficial resemblance to C. southcotti , described above, but differs in its much larger size, its possession of flat, ribbon-like tentacles, and by the crescentic row of vacuoles at the base of the central tentacles. In addition, nematocyst warts are less dense on the manubrium and oral arms, and on the exumbrella they appear in strongly defined streaks. The oral arms in C. southcotti are stiff and short, while in C. wurlerra they are long, tapering, and weak. Furthermore, C. southcotti reaches tentacular maturity by about 38 mm, and has eggs in the gonads by 35 mm, whereas C. wurlerra most often begins to sprout the first and fifth tentacles at about 70 mm and has eggs in the gonads at about 60 mm. Littleford (1938) stated that species of Chrysaora could not be distinguished by the age at which sexual maturity occurs; he was looking at a difference between 15 cm and 20 cm, and found many intergrading forms. However, while it may have been true for his medusae, it does not appear to be the case for ours. In the present case the differences in size are approximately double: C. wurlerra begins to develop eggs at about 6 cm and reaches a maximum size of about 12 cm while C. southcotti has eggs at about 3 cm and reaches a maximum of about 6 cm.

PLATE 6. Desmonema scoresbyanna , sp. nov., holotype. A, subumbrellar view. (Scale = 10 mm). B, rhopalial cone. (Scale = 2.0 mm). C, rhopalium. (Scale = 0.5 mm).

Furthermore, the 2-1-2 tentacle arrangement in each octant, conspicuous in C. wurlerra , is less conspicuous in C. southcotti . In all 40-tentacled species that we have studied (e.g., C. quinquecirrha , C. lactea , C. pacifica ), there is some degree of this 2-1-2 arrangement, where the 1st & 2nd tentacles and 4th & 5th tentacles are closer together than either is to the middle tentacle (L. Gershwin, unpublished notes). In C. wurlerra , the 1st and 5th tentacles, even in the largest specimens, are reduced and sprouting from the subumbrella between still-fused lappets, thus suggesting that C. wurlerra may grow much larger than we are currently aware, further separating it from its South Australian counterpart. It is possible that with continued growth, the 1st -2nd and 4th -5th tentacles separate somewhat to take on a more evenly spaced appearance, such as in C. southcotti , or possibly they stay clustered as in the present specimens; however, without collection of new material in a range of sizes, we simply do not know.

The “stages” through which Chrysaora medusae develop bears some discussion. About a hundred years ago, there was much discussion about pelagiid medusae developing through a progressive sequence of genera (e.g., Mayer 1910, and references therein). For example, Kuragea passes through the Pelagia stage (1 tentacle per octant), then the Chrysaora stage (3 per octant), and then the Dactylometra stage (5 per octant), before reaching its own mature stage (with 7 tentacles per octant). Thus, it was hypothesized that each genus passes through the earlier genera in its development, a living example of Haeckel’s (1899) Biogenetic Law (i.e., that ontogeny recapitulates phylogeny). For example, Chrysaora wurlerra (with 40 tentacles) must certainly pass through a stage with eight tentacles and then a stage with 24, yet it still would not be confused with other taxa at those developmental stages because it has its own unique set of characters. Thus, when we refer to medusae in “the 24-tentacle stage”, we merely mean a stage of tentacular development that may be a proxy for total maturity, and we are not referring to the earlier belief in an ontogenetic progression through different genera.