- Two new species of jellyfishes (Cnidaria: Cubozoa: Carybdeida) from tropical Western Australia, presumed to cause Irukandji Syndrome
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- Gershwin, Lisa-Ann (2005): Two new species of jellyfishes (Cnidaria: Cubozoa: Carybdeida) from tropical Western Australia, presumed to cause Irukandji Syndrome. Zootaxa 1084: 1-30, DOI: 10.5281/zenodo.170452
Type species Malo maxima n. sp., designated herein. Diagnosis Carybdeidae without gastric phacellae; with frownshaped rhopaliar niche ostia; with rhopaliar horns; with two median eyes only, lacking lateral eye spots; with fine, cylindrical, unmodified tentacles; with one stomach pouch extension branching into about 4 5 simple to bifurcated velarial canals per octant; with moderately developed perradial mesenteries; pedalial canals lacking prominent thorn. Etymology The genus name honours Mark Longhurst, who recently survived a particularly severe sting, presumed to be from this species. The first two letters of his first and last name were taken to compose the genus name. It is also an interesting coincidence that the word “ malo ” is Spanish for “ bad ”, as this species is presumed to be capable of lethal envenomation. Gender masculine. Remarks The genus Malo is most similar morphologically to Carukia and the soontobedescribed “ Darwin carybdeid ” (Gershwin and Alderslade in review) as summarized in Table 1. All three groups lack gastric phacellae, and have frownshaped rhopalial niche ostia, rows of nematocyst warts on the perradial lappets, well developed perradial mesenteries, conspicuous rhopalial horns, and warty bells. These characters are also shared by all other known or suspected Irukandjis (Gershwin, unpublished), except for those in the Carybdea alata group and Physalia (Fenner et al. 1993; Gershwin in press). Therefore, the majority of known and suspected Irukandjis appear to form a natural group, and this information can be used predictively to evaluate the risk factors associated with untested forms. While Malo, Carukia and the “ Darwin carybdeid ” cluster together morphologically as described above and in Table 1 (and genetically, see Gershwin, 2005) to the exclusion of other genera, many differences nonetheless exist to separate these forms from one another. First, the tentacle bands of Carukia are peculiarly modified into collarlike bands with tails, whereas no such modifications occur on the tentacles of Malo or the “ Darwin carybdeid. ” Second, the rhopalial horns are short, wide, and crescentshaped in Malo and the “ Darwin carybdeid, ” and long and narrow in Carukia. Third, the “ Darwin carybdeid ” has large, round pedalia, with a conspicuous thornlike diverticulum projecting upward from the bend of each canal; Malo and Carukia have narrower pedalia, with either no thorn at all, or it is so small as to be of debatable existence. Fourth, the nematocyst warts of Carukia are marked by bright red pigment, whereas the warts of Malo and the “ Darwin carybdeid ” are pale purple. Fifth, the overall body shape of Carukia is that of a delicate blunt, rounded pyramid, whereas the bell of Malo is tall, narrow, and robust; the body of the “ Darwin carybdeid ” is even more robust, and less narrow. Sixth, the rhopalia of Malo have only the two median complex eyes, lacking lateral eye spots, whereas Carukia has the full complement of six eyes; the eyes of the “ Darwin carybdeid ” are known to have the two median complex eyes, but whether they have the lateral eye spots is unknown. Seventh, Malo has nematocyst patches on the outer keel of the pedalia, whereas the pedalia of Carukia and the “ Darwin carybdeid ” are naked. Finally, Carukia reaches a maximum of only about 15 mm BH (more typically about 11 mm), whereas Malo is known to attain 48 mm and the “ Darwin carybdeid ” reaches well over 60 mm. TABLE 1. Comparison of main diagnostic characters in the genera and natural groups of the Carybdeida. Carybdea A includes C. marsupialis, C. xaymacana, and C. rastonii. Carybdea B includes those species previously associated with C. alata. Carybdea C includes C. sivickisi. Phacellae Rhopalial Rhopalial Pedalial Velarial Perradial Mesenteries Gonads Other niche ostia horns canal canals lappets per octant Carukia Absent Frown Long & Simple 2, simple Lacking Well devel Leaflike Modified tenshaped narrow warts oped ½ way tacle bands Darwin carybdeid Absent Frown Short & Thorn 7 10, Ca 5 warts Well devel Leaflike Greatly Carybdea A Bushlike, Heart Absent with short shaped cirri Knee 2, Absent biforked complex Present, but Leaflike Pedalial nempoorly atocysts developed Carybdea B Crescen Tshaped Absent tic, with parallel cirri Variable 3, sim Absent ple com plex Absent Leaflike Hemispherical pedalia Carybdea C Bushlike, Vertical Absent with short keyhole cirri Simple 2, paw Absent like Present Leaflike Exumbrellar halfway adhesive pads shaped broad complex oped ½ way flared tentacle base The western Atlantic Tamoya haplonema Müller, 1859, appears to be the most similar described species to the Malo Carukia Darwin Carybdeid group. All share the frownshaped rhopalial niche ostium; however, Tamoya has gastric phacellae and lacks the perradial lappets and the rhopaliar horns that, in part, characterize this group.