Chrysaora pentastoma Péron & Lesueur, 1810

Morandini, André C. & Marques, Antonio C., 2010, Revision of the genus Chrysaora Péron & Lesueur, 1810 (Cnidaria: Scyphozoa) 2464, Zootaxa 2464, pp. 1-97 : 45-47

Chrysaora pentastoma Péron & Lesueur, 1810

( Figures 68 –69, 83)

Chrysaora pentastoma Péron & Lesueur 1810: 366 (original description), N° 117 [terre Napoléon = Australia]; Goy

1995: 368, Pl. p. 371. Chrysaora hysoscella ; Goy 1995: Pl. p. 371. [non Chrysaora hysoscella ( Linnaeus, 1767) ]. Chrysaora southcotti Gershwin & Zeidler 2008: 7–11 (description), Pl. 3 (live medusa), Pl. IV fig. A (subumbrellar view), fig. B (tentacles), fig. C (rhopalia), figs D–E (tentacle detail) [Port Noarlunga, South Australia – Australia].

Holotype specimen. Not available. Although the holotype of the junior synonym Chrysaora southcotti Gershwin & Zeidler, 2008 is available (SAM H969), it was not seen.

Type locality. île Decrès ( Goy 1995: 368, today known as Kangaroo Island, South Australia – Australia.

Distribution. South Australia (Gulf St. Vincent, Kangaroo Island, Edithburg, Port Noarlunga) ( Fig. 83).

Diagnosis (based on Gershwin & Zeidler 2008). Medusae with recorded diameter of 6.6 cm ( Fig. 68); marginal lappets with two different sizes: rounded and tongue-shaped (Fig. 69), 6 per octant; mature specimens with 40 tentacles (5 tentacles per octant); quadralinga not mentioned; background colouration transparent or whitish with exumbrellar nematocyst warts dark-red, oral arms dark-reddish; gonads crescentic to Mshaped.

Cnidome. “spherical isorhizas” (13.73–17.18 µm, n=23); “large euryteles” (8.78–10.33 x 6.13–7.69 µm, n=9); “small euryteles” (5.8–7.16 x 3.77–4.44 µm, n=9). These measurements (small x large euryteles) should be revised, because the differences between the size classes are only 1.62 µm, which sometimes is lesser then standard error found in the measurements for other species.

Systematic remarks. Chrysaora pentastoma has a colour pattern distinct from all other Chrysaora species , and its exumbrellar rhopalial pits are shallower than those of other species (according to Gershwin & Zeidler 2008). The tentacles are 40 and can inflict a painful sting ( Gershwin & Zeidler 2008: 10). The similar colour pattern of C. southcotti and C. pentastoma (described by Péron & Lesueur 1810: 366; plate published by Goy 1995: 371) suggests that the two names may refer to the same species ( Gershwin & Zeidler 2008: 11). Gershwin and Zeidler argued that the written description of C. pentastoma is incomplete and inadequate to correctly identify the specimens (there are no available specimens of Péron & Lesueur’s species, only the plate), and they concluded that C. pentastoma is an unrecognizable species (nomen dubium). The type locality of C. pentastoma is vague (“ de la terre Napoléon ”) in the original description of Péron & Lesueur (1810: 366), but Goy (1995: 368) provided further details (“ de l’ilê Decrès ”, presently known as Kangaroo Island, Australia), a site quite close to the type locality of C. southcotti (Port Noarlunga) , and from where several specimens were observed (see list of specimens in Gershwin & Zeidler 2008: 7). Based on these data, we do not consider it necessary to establish a new name for specimens from South Australia, and prefer to use the older available name ( pentastoma ). Although Péron & Lesueur (1810: 366) described the species based on an imperfect specimen (“ cinq bras ramifies; cinq bouches; cinq estomacs ”) it is assumed here (based on the description of Gershwin & Zeidler 2008) that the species has tetramerous symmetry.

In addition to a new name being unnecessary, as noted above (see discussion in C. kynthia ), colour pattern is a character that that must be considered with care in the taxonomy of Chrysaora because of its variability. Supposedly diagnostic characters such as the M-shaped gonads (or “inverted W-shaped”) are also variable and have been observed in other species (e.g. the South Australian C. kynthia ; see discussion above). Moreover, other characters thought diagnostic do not justify recognition of this new species: (a) depth of the rhopaliar pits is difficult to compare, and the description given may refer to any species of Chrysaora ; (b) conspicuous warts, thought important, are variable as observed in the large series of medusae examined here (e.g., those of C. lactea vary considerably, with some specimens having large and coloured warts and others having the body finely granulated). Thus, we regard C. southcotti as a redescription of C. pentastoma .

Etymology. pentastoma : likely in reference to the presence of five oral arms in the species (based on an imperfect specimen), derived from the Greek pente (five) plus stoma (mouth) ( Brown 1956).