Timoides agassizii, Bigelow, 1904

Purushothaman, Jasmine, Kharusi, Lubna Al, Mills, Claudia E., Ghielani, Hamed & Marzouki, Mohammad Al, 2013, Timoides agassizii Bigelow, 1904, little-known hydromedusa (Cnidaria), appears briefly in large numbers off Oman, March 2011, with additional notes about species of the genus Timoides, Zootaxa 3746 (2), pp. 372-382 : 375-376

Timoides agassizii, Bigelow, 1904

Material examined. Several live medusae collected from the surface offshore Sohar, Oman, and two preserved medusae collected by plankton tow 0–10 m at the same location, all from February 2011 and March 2009 respectively .

Additional material: Photograph by Gustav Paulay, University of Florida, of damaged specimen collected by Y. and K. Paulay in water approximately 1 m deep in the Western Shoals portion of Apra Harbor, Guam on 24 July 2000 (reported by Kirkendale & Calder, 2003). The description below is also based on the observations and two photographs in Iwanaga et al. (2003), who collected medusae twice as large as previously known.

Description ( Figs. 2 & 3 ). Medusa umbrella hemispherical, with rounded dome to 44 mm diameter and 20 mm or more high, though more typically to 20 mm diameter and less tall, with slightly flaring sides ( Fig. 2a, b ). Apical jelly nearly as thick as subumbrella is deep, with thickness decreasing towards margin. With 4 straight, fairly broad radial canals ( Fig. 3b ) and a broad marginal ring canal ( Fig. 3b,c ) that gives off from 12 to as many as over 60 blindly-ending centripetal canals ( Fig. 2a,b ); if there are 12 centripetal canals, the 4 interradial canals are about two thirds as long as the bell height and the 8 adradial canals only half this length. With as many as 62 tentacles, but if typically 32 tentacles, then 4 perradial, 4 interradial, 8 adradial and 16 intermediates. Each tentacle with a thick, conical, laterally-compressed bulb on the margin of umbrella; the largest tentacles may have a very short spur pointing apically ( Fig. 2 , 3a,b,c ). The interradial and adradial tentacles are at the bases of interradial and adradial centripetal canals. The remaining intermediate tentacles alternate with the radial and centripetal canals and the total numbers of tentacles increases with bell size. All of the tentacles are exceedingly flexible and contractile; when expanded, the tentacles are at least 400 mm long and when contracted they coil helically in places ( Fig. 2b ) and shorten in length. In addition to the tentacles, there are numerous cirri along the bell margin, but no cirri arise from the sides of the tentacle bulbs; it is possible that all cirri can develop into tentacles in very large medusae. The bell margin has no statocysts. The velum is well developed. A broad, conical peduncle as long as the depth of the bell cavity supports the barrel-shaped stomach, which is almost as long as the peduncle and bears 4 long, lancet-shaped lips with deeply crenulated margins ( Fig. 2a ). These lips may be longer than the combined lengths of peduncle and stomach. The 8 gonads completely cover the manubrium; they consist of a great number of simple and branched papilliform, folded processes or reticulae ( Fig. 3d ) on both sides of the 4 radial canals, thus forming 4 prominent, double ridges. In life, the jelly is transparent and colorless, the radial canals and tentacles are rose pink and there is a dark pink pigment spot at the base of each tentacle; the gonads vary from Indian yellow to a ruddy orange-brown and the long oral lips which trail below the gonad-covered manubrium are a deep violet-pink ( Fig. 2a,b ). All colored portions except the gonads turn a creamy white when preserved.

The polyp is unknown.

Distribution ( Table 1). Timoides agassizii has an Indo-Western Pacific range in surface waters, having been collected in the Gulf of Oman in the north Indian Ocean, the Maldive Islands near the base of India, Papua New Guinea, the Marshall Islands, Guam, and Okinawa in the Western Pacific, and Beibu Gulf in the northern South China Sea. Most specimens, including on the four occasions that this species has been recorded as abundant, have been collected nearshore.

Remarks. Iwanaga et al. (2003) report that twelve people in Okinawa complained of jellyfish stings whose symptoms included itching and pain, presumably attributable to the large numbers of T. agassizii near the beach at the time.

A second species, Timoides latistyla , has been described from a single medusa collected in the Taiwan Strait ( Xu et al. 2007). T. latistyla is distinguished by its four short, fairly simple lips that emerge only slightly from the large, tightly-folded gonad-covered manubrium that is suspended from the peduncle of the mature specimen. We first believed the medusa ( Fig. 2b ) collected in Guam (reported by Kirkendale & Calder 2003) to be T. latistyla , but upon closer examination, the short mouth of the Guam specimen appears to be regenerating four new frilly lips. It appears identical to T. agassizii in all other respects and we feel comfortable in assigning it to this species. In Friday Harbor, Washington, one of us (C.E.M.) has frequently observed hydromedusae with colored gonads that have been ravaged by predation, probably by fish, and the long, dangling lips of T. agassizii seem a conspicuous target for hungry predators in the surface waters. This lip-free Guam medusa causes us to wonder if T. latistyla is a valid species, or if the single described specimen was another T. agassizii damaged by predation; its geographic location falls between Okinawa and the South China Sea, within the range for T. agassizii . It should be noted that a typo in the original description of T. latistyla ( Xu et al. 2007) reports the medusa to be 2.2 mm wide and 15 mm high, but the drawing indicates a medusa wider than tall, so the width should read 22 mm.

Figures

FIGURE 2. Timoides agassizii. a) Living specimens collected February 2011 in Sohar, Oman. b) Living specimen collected July 24, 2000 Apra Harbor, Guam, with slightly regenerating oral lips (photograph by Gustav Paulay, used with permission).

FIGURE 3. Timoides agassizii. a) to c) Details of the umbrella margin, with enlarged view of an interradial marginal bulb with tentaculae extended. d) Structural details of a mature gonad.