Sanderia pampinosus

Description. Umbrella diameter to 75 mm, of thin consistency; with conspicuous flattened, solid, gelatinous, nematocyst-tipped papillae over entire exumbrellar surface (Figure 1 B), appearing to arise from transparent “ holes ” in translucent exumbrella. In some specimens, exumbrellar papillae concentrated in central half of bell, extending in rows onto lappets. Holotype with ridge across exumbrellar diameter, cause or function unknown, possibly an artifact of preservation. Subumbrellar nematocyst warts lacking; subgenital ostium absent, instead, a large, closed depression containing the gastric filaments. Central stomach cavity in four interradial horseshoe-shaped pouches, with convex or straight distal margin, lacking indentation or heart-shape; with gastric cirri attached haphazardly to bag-like subumbrellar membrane, entirely internal (Figure 1 C). Peripheral stomach region divided into 32 unequal radiating pouches, the tentacular pouches being slightly broader proximally and distally than the rhopaliar pouches. Radial septa dividing peripheral stomach pouches nearly straight, with shallow “ S ” - curve in distal ¼, ending toward rhopalia; with jagged edges, especially distally; with proximal termini teardrop-shaped. Gonads 4, entirely within approximately 40 flattened, external, pendant papillae lining rim of each stomach pouch; gonadal papillae to about 13.5 mm long, 2.5 mm wide, covered in large, round, smooth nematocyst patches; mature by 50 mm BD. Lappets 32, square-shaped; each with two triangular, nippled extensions of corresponding gastric pouches. Rhopalia 16, 4 perradial, 4 interradial, and 8 adradial; open to subumbrellar side; with blind-ending, outward-pointing exumbrellar cone. Tentacles 16, eradial, singly in alternation with rhopalia; flattened in the oral-aboral orientation; with nematocysts in scattered round patches, larger on abaxial side; longest measurable tentacle 60.82 mm (preserved). Manubrium long, tubular, sparsely scattered with small nematocyst patches. Oral arms damaged in all specimens; from remnants: with sparsely scattered small, round nematocyst patches; length to about 1 x BD, narrow. Colour in life unknown; preserved, translucent with pinkish gonadal papillae.

Diagnosis. Sanderia with approximately 40 gonadal papillae per pouch, with gonadal tissue entirely contained within the papillae in horseshoe-shaped gastric pouches; eradial tentacles flattened in the oral-aboral direction, with nematocyst clusters on all sides.

Remarks. The only other species currently assigned to Sanderia is S. malayensis Goette (1886), which is clearly distinguishable from the present species in the location and number of genital papillae and in the shape of ring they form around the stomach cavity. In a mature S. malayensis (ca. 90 mm), there are 14 – 30 papillae per gonadal ring (Browne 1926; Mayer 1910, 1917; Stiasny 1937; Vanhöffen 1902). Goette’s original specimens from Singapore were only 15 mm and 25 mm in diameter, and the number of gonadal papillae was not stated; similarly, Stiasny (1935) had seven specimens from Singapore ranging from 12 – 30 mm diameter, but did not state the number of gonadal papillae. Mature specimens have been collected from other locations. Vanhöffen (1902) studied material from the Gulf of Aden, reporting 24 gonadal papillae but not reporting the size of the specimens. Kishinouye (1910) found a single specimen of 90 mm diameter off Japan, but did not state the number of gonadal papillae. Browne (1926) studied 30 specimens 12 – 35 mm diameter from the Suez Canal region, and reported that they do not begin developing gonads until they reach at least 25 mm diameter; in specimens 30 – 35 mm diameter, 5 – 16 ridges are formed but not fully developed into finger-like papillae. Mayer (1910) reported on a perfect specimen from the Philippines; at 75 mm diameter, it had 25 – 30 gonadal papillae. Thus, it would appear that the gonads form a small number of ridges at about 30 mm bell diameter, subsequently elongating into finger-like papillae and growing in number to a mature stage at about 75 mm diameter with up to about 30 papillae. In contrast, S. pampinosus reaches a full complement of 36 – 44 gonadal papillae per ring before it reaches a mere 50 mm diameter, and does not appear to add more with an increase in bell size up to 75 mm. Thus, the numerical difference in gonad papillae number does not appear to be ontogenetic. The shape of the gonadal ring in S. pampinosus is horseshoe-shaped, whereas in S. malayensis it forms a heart-shaped structure. Stiasny (1937) reported that his five specimens from the Gulf of Oman, ranging from 35 – 55 mm diameter, had horseshoe-shaped rather than heart-shaped gonad rings. We are not clear at this time whether this suggests that the Gulf of Oman specimens might be related to, but not identical to, the true S. malayensis, or to S. pampinosus for that matter, or whether this suggests that there is variability in this character among species. Statistical shape analyses of a large number of specimens from different localities are needed to help answer this question. The two specimens figured by Stiasny have up to about 35 gonadal papillae, more like S. pampinosus than S. malayensis at a similar size, leading us to question the specific identity of the Gulf of Oman form. Stiasny (1937) also noted that these specimens, like the Malayan specimens he studied from the Snellius expedition (1935), completely lacked pigment; in contrast, Vanhöffen’s (1902) specimens from the Gulf of Aden had yellow-brown streaks on the exumbrella, suggesting that they may have been a different species that were not recognized at the time as such. While we do not know the colour of the living Australian form, a recently identified Sanderia in New Zealand waters is ghostly whitish with conspicuous reddish streak-shaped nematocyst clusters in the tentacular and rhopaliar radii (Gershwin & Gordon, unpublished notes). Furthermore, in the Japanese form, previously described as Neopelagia eximia Kishinouye, 1910 and assigned to the synonymy of S. malayensis by Mayer (1910), the tentacles are at the perradii and interradii, flattened laterally, with nematocyst warts only on the abaxial side. Whether the same is true for the Malaysian form, we cannot presently determine. However, medusae with these characters differ considerably from S. pampinosus, in which the tentacles are all eradial, flattened in the oral-aboral direction, and bear nematocyst patches on all sides. Apparent confusion exists in the literature about the actual form of the gonads in Sanderia malayensis. According to Browne (1926), Vanhöffen (1902) described them as internal with external protective papillae; Kishinouye (1910) described them from Japanese material as partly extending into the external ridges; and Browne himself, who studied 30 specimens from the Suez Canal, noted that the genital band may fold into the interior of the ridges, supporting Kishinouye’s findings. Stiasny (1937), however, described and figured specimens from the Arabian Sea in which the gonad is entirely contained within the papillae. Thus, S. pampinosus appears to be most closely allied to the Arabian Sea form, with gonads entirely in external papillae. Moreover, the shape of the gonadal ring is horseshoe-shaped rather than heart-shaped. However, there is still a large numerical difference in papillae number between the present specimens (ca. 40 per ring) and Stiasny’s material (ca. 22 – 36), and the radial septa are considerably more robust in the latter. We cannot determine at this time whether the Arabian Sea material is conspecific with S. pampinosus. One might conceivably question the validity of adding another species to a genus defined by a duplication of rhopalia (i. e., 16 rhopalia instead of the typical eight of Pelagiidae). However, although it is commonly cited, the duplication of rhopalia is not the only feature separating Sanderia from other genera of Pelagiidae; the finger-like gonads along the rim of the gastro-gonadal pouch are unlike those of any other. Thus, an ephyra of Chrysaora or Pelagia, liberated with 16 rhopalia, would still not develop into a medusa corresponding to Sanderia, and an ephyra of Sanderia liberated with eight rhopalia would nevertheless develop into a medusa identifiable as Sanderia. Symmetry and meristic deviations, and their phylogenetic implications, were studied by Gershwin (1999), who observed that these sorts of deviations occur about 2 % of the time in any given population, and may play an important role in the ability of a lineage to withstand environmental perturbations. One might further question whether slight morphological differences such as gonadal papillae number, gastro-gonadal pouch shape, tentacular armature, and ontogenetic comparisons are sufficient grounds to propose a new species. We assert that it is equally possible that all forms of Sanderia might be members of one highly variable species, or that morphologically diagnosable forms in different geographical regions represent further biological differences not previously appreciated; the answer to this question rests in further study based on large numbers of specimens subjected to statistical and molecular analyses. In the meantime, it seems clear to us that the Australian form bears numerous structural differences from the Malayan form, and we question the accuracy of some identifications from other regions.

Distribution. The genus Sanderia has not previously been recorded in Australian waters, a fact that surprised Williamson et al. (1996: 231) in referring to S. malayensis: “ Curiously the species has not been reported in Indonesia, Papua New Guinea or Australia ”. Thus, the description of S. pampinosus extends the range of the genus considerably east. Furthermore, a species of Sanderia of uncertain identity has recently been found in New Zealand waters (Gershwin & Gordon, unpublished notes).

Etymology. From the Latin “ pampinosus, ” meaning “ full of tendrils, ” in reference to the numerous elongate gonadal papillae.

Holotype: WAM Z 4692, 105 n. miles NW of Port Hedland, WA, 19 ° 06 ’ S: 117 ° 17 ’ E to 19 ° 05 ’ S: 117 ° 19 ’ E, 14 April 1982, coll. L. Marsh on ‘ Soela; ’ 74.80 mm BD, gonadal papillae: 40, 40, 39, 41. Paratypes: WAM Z 4693, 100 n. miles NW of Port Hedland, WA, 18 ° 59 ’ S: 117 ° 32 ’ E to 18 ° 59 ’ S: 117 ° 31 ’ E, 14 April 1982, coll. L. Marsh on ‘ Soela; ’ 49.25 mm BD, gonadal papillae: 44, 36, 44, 42. WAM Z 4748, 106 n. miles NNW of Port Hedland, WA, 18 ° 33 ’ S: 118 ° 22 ’ E to 18 ° 33 ’ S: 118 ° 20 ’ E, 28 March 1982, coll. L. Marsh on ‘ Soela; ’ 59.53 mm BD, gonadal papillae: 40, 40, 34 (damaged), 38.