Chrysaora wurlerra Gershwin & Zeidler, 2008

Morandini, André C. & Marques, Antonio C., 2010, Revision of the genus Chrysaora Péron & Lesueur, 1810 (Cnidaria: Scyphozoa) 2464, Zootaxa 2464, pp. 1-97 : 52-62

Chrysaora wurlerra Gershwin & Zeidler, 2008 [nomen dubium]

( Figure 70, 83)

Chrysaora wurlerra Gershwin & Zeidler 2008: 11–15 (original description), Pl. 5 fig. A (live medusa), fig. B (subumbrellar tentacle base), fig. C (rhopalium) [Nobby Beach, Hawkesbury River, New South Wales – Australia].

Holotype specimen. AM G13681 (~ 12.59 cm in diameter, 16.x.1968, female, Nobby Beach , Hawkesbury River, 33°33’S 151°14’E, New South Wales – Australia) [not seen].

Type locality. Nobby Beach, Hawkesbury River, New South Wales, Australia.

Distribution. Southeastern Australia (Manly and Hawkesbury River, New South Wales, Australia) ( Fig. 83).

Diagnosis (based on Gershwin & Zeidler 2008). Medusae with recorded diameter 12.59 cm; marginal lappets with two different sizes: bilobed and tongue-shaped, 3 per octant; mature specimens with 40 tentacles (5 tentacles per octant), some specimens with 24 tentacles, with crescentic row of vacuoles at central tentacle base; quadralinga not mentioned; colouration unknown (preserved specimens known only).

Systematic remarks. Chrysaora wurlerra has 40 tentacles, as in many other species of the genus ( C. chinensis , C. fulgida , C. lactea , C. pacifica , C. quinquecirrha , C. pentastoma ). It was distinguished by the row of vacuoles at the base of each central tentacle, although this character is noted to be polymorphic ( Gershwin & Zeidler 2008: 12). Therefore, we see no decisive and unique characters to justify this species.

Descriptions and figures of three species of Chrysaora occurring in Australian waters provided by Gershwin & Zeidler (2008) included diagnostic characters for them ( C. kynthia with inverted W-shaped gonads; C. pentastoma with shallow exumbrellar rhopalial pits, colour pattern, M-shaped gonads; C. wurlerra with row of vacuoles at base of central tentacles). However, we note the weakness of these diagnostic characters, both because of their variability and their universality among other species of Chrysaora . Moreover, earlier valid names are available for species described from the same region. Additional observations on and descriptions of these Australian species are needed, especially on cnidome and various morphological characters used in this revision. Therefore, we consider C. kynthia and C. wurlerra as nomina dubia, needing to be more fully evaluated and described. In addition, we presently consider C. southcotti to be a junior synonym of C. pentastoma .

Etymology. wurlerra : from the Aboriginal wur (= fire) and lerra (= river), in reference to “stinging water” due to the stinging capacity of the species ( Gershwin & Zeidler 2008).

N e m a t o c ys t c om p a r i s o n a n d u t i l i t y. The study of the cnidome is a traditional and useful tool for the taxonomy of different cnidarian groups (viz. Anthozoa and Hydrozoa). The cnidome of scyphozoans are considered less diverse than those of the other classes, including only a few types ( Arai 1997; Marques & Collins 2004). Recently, studies using scanning electron microscopy ( Östman & Hydman 1997; Östman 2000) revealed that scyphozoan nematocysts may indeed have greater variation than presently appreciated.

Nematocysts of tentacles of the 11 studied species of Chrysaora ( C. caliparea , C. kynthia , C. pentastoma , and C. wurlerra not included) are presented in a comparative table (Table II). Tentacles of every species bear three types of holotrichous isorhizas (spheric O, a-isorhiza, and A-isorhiza) and one type of heterotrichous microbasic rhopaloid (see also species descriptions). The heterotrichous microbasic rhopaloid might have one (eurytele) or two (birhopaloid) dilations of the shaft, but this is indistinguishable under light microscopy squashes.

Types present in different species are not diagnostic characters, but the dimensions of the nematocysts appear to be an important tool for distinguishing species that are morphologically similar (e.g., C. chinensis vs. C. pacifica and C. fulgida vs. C. hysoscella ). The usefulness of the cnidome in the taxonomy of Chrysaora is not a new conclusion. In the past, two varieties of C. quinquecirrha were based on slight (2 µm) differences in the dimensions of nematocysts of the tentacles (see below), and the evidence from the cnidome supports differences between C quinquecirrha and C. hysoscella ( Papenfuss 1936) .

For statistical comparison of nematocyst measurements, we unified the data as a single measure (the ratio between length and width of the capsule) (Table III). Thus, we performed an analysis of variance of these measures (ANOVA, assuming that the distributions were normal), and compared the p-values (the closer to 1 the more similar are the samples). Although the statistical analysis provided a more confident comparison, our sampling universe was small both in number of measurements (n = 10 for each type) and specimens. Better comparisons can be performed by increasing the number of measurements and the number of specimens observed, but this would require a specific study.

We focus our discussion on the cnidome of morphologically similar species, as an extra source of data for the definition and delimitation of the species.

The similar Pacific species C. achlyos and C. plocamia differ slightly in the size of the holotrichous Oisorhizas (though the dimensions are slightly overlapped), with those of C. plocamia being larger (1.5–5.6 µm differences for the mean values). Conversely, the holotrichous A-isorhizas of C. achlyos are larger (0.9–5.8 µm differences for the mean values) than those of C. plocamia . Statistical analyses (ANOVA) were not conclusive because they showed that the p-values (Table IV) vary among nematocyst types (sometimes grouping different specimens of the two species). This result is due to large intraspecific variation of nematocyst size capsules of all kinds.

The resurrected species C. chinensis resembles C. pacifica , and their ranges are in close proximity ( China Sea and Japan). Notably, holotrichous O-isorhizas of C. pacifica are much smaller than those of C. chinensis (ca. 2 times smaller on average); although the statistical analyses (ANOVA) were not conclusive because they showed that the p-values (Table V) vary among nematocyst types (sometimes grouping different specimens of the two species).

Chrysaora colorata can easily be distinguished by morphology, but its holotrichous A-isorhizas are much smaller in size than those of all other species.

The west African C. fulgida has many times been identified as C. hysoscella (see synonymy above). However, besides reproductive differences (hermaphroditism in C. hysoscella ), they differ in sizes of holotrichous A-isorhizas (4.2–4.8 µm differences of the mean values) and heterotrichous microbasic rhopaloids (1.9–2.3 µm differences for the mean values). However, statistical analyses (ANOVA) showed that the p-values (Table VI) vary among nematocyst types, sometimes grouping the species. There is some intraspecific variation of nematocyst size capsules of all kinds in the observed specimens of C. fulgida .

The northwest Pacific Ocean is a complex area with several sympatric species of the genus. Chrysaora fuscescens and C. melanaster might be confounded because of their large size, numbers of lappets, and tentacles. The cnidome of both species differ slightly in the size of the holotrichous O-isorhizas (0.9–4.7 µm differences for the mean values), holotrichous A-isorhizas (2.3–5.2 µm differences for the mean values) and by the presence of a second size class of holotrichous A-isorhizas in C. melanaster . The statistical analyses (ANOVA) were not conclusive because they showed that the p-values (Table VII) vary among nematocyst types (sometimes grouping different specimens of the two species). Chrysaora melanaster may also be confounded with C. pacifica , because of their colour pattern; but the sizes of the holotrichous O-isorhizas of C. pacifica are considerably smaller, although the statistical analyses (ANOVA) showed little differences in pvalue (Table VIII).

The cnidome of the two observed specimens of C. quinquecirrha present slight differences in the range and mean values for holotrichous O- and A-isorhizas. In the past Papenfuss (1936) distinguished two varieties of C. quinquecirrha (estuarine and coastal) based on nematocyst differences as well as colour and tentacle number. Bayha (2006) also found molecular differences among estuarine and coastal forms of the species. We interpret these differences as variations of the same species.

The cnidomes of C. lactea (Brazilian and Caribbean specimens) and C. quinquecirrha are similar in all types of nematocysts measured, and the values for both species overlap. Statistical analyses (ANOVA) were not conclusive because they showed that the p-values (Table IX) vary among nematocyst types (sometimes grouping different specimens of the two species). Unfortunately, no distinction between these species can be made based on light microscopy of their tentacle nematocysts.

From the three recently described species of the genus Chrysaora from Australian waters, the tentacle cnidome was presented only for C. pentastoma . According to Gershwin and Zeidler (2008: 10) tentacle nematocysts consists of “large spherical isorhizas” (13.73–17.18 µm, n=23), “larger euryteles” (8.78–10.33 x 6.13– 7.69 µm, n=9), and “smaller euryteles” (5.8–7.16 x 3.77–4.44 µm, n=9).