Scolionema sanshin, Toshino, 2017

Toshino, Sho, 2017, Scolionema sanshin sp. n., a new species (Hydrozoa, Limnomedusae, Olindiidae) from the Ryukyu Archipelago, southern Japan, Zootaxa 4344 (2), pp. 277-290 : 280-286

Scolionema sanshin sp. n.

New JapaneSe name: Komochi-kaginote-kurage-modoki Figure 2–6

Material examined. Holotype: NSMT-Co1597. Southern Japan, Okinawa Prefecture, Aka ISland, HizuShihama , 26°11'22.8"N, 127°16'32.2"E, 6 July 1999, collector: Kazuyuki Shimoji, one adult female ( Fig. 2A–C ) . ParatypeS. NSMT-Co1598. Same locality aS Holotype, 6 July 1999, collector: Kazuyuki Shimoji, one adult male. NSMT- Co 1599. Same locality aS Holotype, 4 July 1999, collector: Kazuyuki Shimoji , one adult female. NSMT-Co1600. Southern Japan , Okinawa Prefecture, Ginowan , Ginowan Marina , 26°16'38.4"N, 127°43'47.0"E, 12 June 2003, collector: unknown, one adult female. NSMT-Co1601. Southern Japan , Okinawa Prefecture, IShigaki ISland, FuSaki , 24°22'21.5"N, 124°6'50.4"E, 4 June 2002, collector: unknown, one adult male.

Description. Mature meduSae with Smooth, tranSparent, plate-like eXumbrella ( Fig. 2A, D ). UH about 4 mm and UD about 7 mm ( Table 3). EXumbrella lacking nematocySt wartS or centripetal canalS ( Fig. 2A, B, D, E ). Cock’S-comb Shaped gonadS attached along edge of diStal part of four radial canalS only, and light red to orange in color ( Fig. 2B, C, D, E , 3A ). TeSteS were full of Sperm ( Fig. 3A ), while oVarieS contained fully mature eggS ( Fig. 3B ). Marginal tentacleS 60 to 70, with nematocySt ringS and eVenly Spaced adheSiVe padS ( Fig. 3C ). StatocyStS 16, encloSed in meSoglea ( Fig. 3D ). The endoderm cellS at the baSe of tentacleS, radial canalS and gonadS were fluoreScent green in color under LED light ( Fig. 3A, D, E ). The portion of the tentacle proXimal from the adheSiVe pad iS nearly Straight, while the diStal portion iS bent in a hook-like manner ( Fig. 3B, C ). The diStal portion of tentacle waS light red in liVing SpecimenS ( Fig. 3C ). The manubrium had a quadrate baSe, and waS light red in color, folded, and with a Short peduncle and fluoreScent at each corner ( Fig. 3E ). MeduSa-budS were not produced from the radial canalS in the collected SpecimenS ( Fig. 3A, B ).

Life cycle. Planulae Settled on the bottom of petri-diSheS and deVeloped into tiny primary polypS within SiX dayS ( Fig. 4A ). The Shape of the primary polypS reSembleS a pouch, with three to four tentacleS. At a body length of about 0.09 mm the mouth diSc diameter of the polypS waS about 0.08 mm. The primary polypS deVeloped into mature polypS within 24 dayS ( Fig. 4A–C ). The Shape of the mature polypS waS almoSt identical to the primary polyp Stage, but they were larger (mean body length 1.8 mm, mean mouth diSc diameter 0.47 mm) and had more tentacleS (fiVe to eight). The baSal diSc waS enVeloped by periderm oVer about half of the total length of itS body. FruStule and meduSa budding were obSerVed when the polypS were at the mature Stage ( Fig. 4D, E ). Both buddingS occurred from the middle part of the calyX. The fruStuleS were about 0.5 mm in length and had no tentacleS. They Settled and grew out into mature polypS within 60 dayS. MeduSa budS deVeloped into free Swimming young meduSae within three dayS.

Young meduSae juSt releaSed from polypS had a Spherical eXumbrella ( Fig. 5A–C ). UH about 1.0 mm and UD about 1.3 mm. EXumbrella with Very Small nematocySt wartS along entire umbrella ( Fig. 5D ). Four Simple radial canalS. GonadS not deVeloped ( Fig. 5D ). StatocyStS eight, encloSed in meSoglea ( Fig. 5E, F ). Marginal tentacleS 19 to 25, with nematocySt ringS and adheSiVe padS ( Fig. 5G ). Manubrium length about 30% of umbrella height ( Fig. 5A ). Peduncle not deVeloped ( Fig. 5A ).

SeVen-day-old meduSae were about 3.4 mm in width ( Table 4). Umbrella bowl-Shaped. OVal gonadS appeared on middle part of radial canalS. Marginal tentacleS about 40. Fifteen-day-old meduSae were about 2.9 mm in height and about 7.3 mm in diameter. The gonadS became cock’S comb-Shaped on the diStal part of the canalS. SiXteen StatocyStS were obSerVed. Marginal tentacleS about 50. Twenty-two-day-old meduSae were about 3.6 mm in height and about 10.6 mm in diameter. GonadS were enlarged. Marginal tentacleS about 65. ASeXual production of meduSa budS waS not obSerVed at temperatureS between 20 to 30°C.

Cnidome. Three different nematocySt typeS were identified and meaSured in the adult meduSa, young meduSae and mature polypS ( Table 5, Fig. 6 ). Adult meduSae had two nematocySt typeS. MicrobaSic euryteleS were found on both the tentacleS and the manubrium while baSitrichouS iSorhizaS were only found on the tentacleS The young meduSae had three nematocySt typeS. Tentacle: microbaSic euryteleS, Umbrella: baSitrichouS iSorhizaS and oVoid iSorhizaS, Manubrium: microbaSic euryteleS. The mature polypS had one nematocySt type; microbaSic euryteleS.

Molecular phylogenetics. The MaXimum Likelihood tree ( Fig. 7 ) reVealed the preSent SampleS and Scolionema suvaense within a monophyletic group within LimnomeduSae . There waS SubStantial diVergence between SequenceS from S. sanshin and S. suvaense ― greater than the Sequence diVergence obSerVed between VariouS SpecieS of OlindiaS Müller, 1861 ( Table 7).

Habitat and ecology. Scolionema sanshin meduSae appear during Summer in a range of Subtropical temperature localitieS in the Ryukyu Archipelago, Southern Japan. MeduSae from VariouS populationS, united under the name S. suvaense , haVe been reported from Summer to fall from Indo Pacific, Mediterranean, and JapaneSe localitieS ( AgaSSiz & Mayer 1899; Goy 1973; Uchida & Sugiura 1976).

The meduSae of S. sanshin were collected near Shore on a beach and in a fiShing port during the night, but were not obSerVed during daytime. The meduSae Seem to be nocturnal in behaViour. MoreoVer, young and adult meduSae Showed reSting behaVior uSing their tentacleS with their adheSiVe padS under lighted conditionS. In the field, they may reSt on Seaweed or Sea graSS during the day, aS with Scolionema suvaense and Gonionemus vertens ( Uchida and Sugiura 1976; Singla 1977). Young and adult meduSae appeared between June to AuguSt. PolypS of S. sanshin may metamorphoSe into meduSae during Summer, when temperatureS riSe from approXimately 25 to oVer 30°C ( Japan Meteorological Agency 2016). Stinging eVentS attributable to S. sanshin are preSently unknown.

Etymology. The SpecieS name sanshin (noun in appoSition) waS deriVed from the Okinawan traditional inStrument “SanShin”―a SnakeSkin-adorned banjo-like inStrument. Hook-like tentacleS of the jellyfiSh reSemble a SanShin performer’S fingerS when they play the inStrument.

Part Type Min Max Mean SD N Adult medusae Tentacle Basitrichous isorhiza D 2.60 5.22 3.81 0.54 100

L 6.87 12.67 9.76 1.00

Microbasic eurytele D 8.36 12.08 9.76 0.72 100

L 14.67 18.86 16.59 0.82

Umbrella N/A D ― ― ― ― ―

L ― ― ― ― ― Differential diagnosis. A compariSon of key featureS of the SpecieS of Scolionema iS preSented in Table 6. Scolionema sanshin can be diStinguiShed from S. suvaense by the Shape of the gonadS and number of tentacleS in adult meduSae. GonadS of S. sanshin are cock’S-comb Shaped, while thoSe of S. suvaense are SinuSoidal, papilliform, folded and lobed or ribbon-Shaped. MeduSa budS are produced in S. suvaense from Japan and Mediterranean Sea, while S. sanshin apparently lackS budS. The number of tentacleS of S. sanshin iS much more than that of S. suvaense from Japan, Mediterranean Sea and MaldiVeS. All populationS of Scolionema haVe 16 StatocyStS, adheSiVe padS on tentacleS, and gonadS located in the diStal 1/3 to 1/2, or edge of diStal part of the radial canalS.

S. suvaense S. suvaense S. suvaense S. suvaense S. suvaense

S. sanshin n. sp. S. suvaense

(as G. suvaensis ) (as G. pelagicus ) (as G. hornelli ) (as S. gemmifera ) (as G. suvaense )

Umbrella điameter (mm) 4.0-6.7 (mean: 5.4) 8 20 6 4 4.5 7

No. of tentacles 49-68 (mean: 62) 70 50 70 32 36-48 48

Nematocyst types (tentacles) B ME - - - - - -

No. of statocysts 1 6 1 6 1 6 1 6 8 1 6 1 6

Ađult Sinusoiđal curve

međusae Shape of gonađs Cock's-comb shapeđ alternately to the right anđ Papilliform Folđeđ anđ lobeđ - Ribbon-shapeđ Ribbon-shapeđ

left

Eđge of đistal part of Eđge of đistal part of Eđge of đistal part of Miđđle part of rađial Eđge of đistal part of

7istribution of gonađs 7istal 183 of rađial canals 7istal 183 of rađial canals

rađial canals rađial canals rađial canals canals rađial canals

Buđđing of međusa buđs Absent Absent Absent Absent Present Present Present

Umbrella điameter 1.0-1.9 (mean: 1.3) - - - 0.7 0.8-1.3 0.6

Juvenile No. of tentacles 19-25 (mean: 22) - - - 8 24-28 16

međusae Nematocyst types (tentacles) ME - - - - - -

No. of statocysts 8 - - - 4 8 8

Bođy điameter 0.7 - - - - - -

Boby length 1.8 - - - - - -

Mature Nematocyst types ME - - - - - ME

polyps No. of tentacles 5-8 - - - - - 2-5

Asexual reprođuction Frustule - - - - - Frustule Bay of?illefranche-sur- Ryukyu Archpelago =ađu islanđ Suvađiva Pearl Banks =ulf of Misaki Sagami Bay Misaki Sagami Bay

istribution Suva Harbor Fiji mer Međiterranean Sea Southern Japan atoll Malđives Manaar nđian>cean Central Japan Central Japan France

References This stuđy Agassi & Mayer (1899) Bigelow 1904 Browne 1905 Kishinouye 1910 Uchiđa & Sugiura 1976 =oy 1973

Figures

FIGURE 2. Scolionema sanshin sp. n., (A – C fixed Holotype, D – F live specimen) A, lateral vieW B, apical vieW C, oral vieW D, lateral vieW E, apical vieW F, oral vieW. Scale bars: 2 mm (A – C), 5 mm (D – F).

FIGURE 3. Scolionema sanshin sp. n. live, in laboratory. A testis B ovary C tentacle D velum E manubrium. AP: Adhesive pad; St: Statocyst. All bars represent 1 mm.

FIGURE 4. Scolionema sanshin sp. n., polyp, live, in laboratory. A, primary polyp, oral vieW. B, adult polyp, lateral vieW. C, adult polyp, oral vieW. D, frustule, lateral vieW. E, medusa budding polyp, lateral vieW. F: frustule; MB: medusa bud; MD: mouth disc; P: periderm. Scale bars: 0.5 mm (A), 1 mm (B – C, E), 0.2 mm (D).

FIGURE 5. Scolionema sanshin sp. n., young medusa, live, in laboratory. A, lateral vieW. B, aboral vieW. C, oral vieW. D, exumbrella, aboral vieW. E – F, statocysts. G, tentacle. AP: Adhesive pad; St: Statocyst. Scale bars: 1 mm (A – C), 0.5 mm (D, E), 50 µm (F), 200 µm (G).

FIGURE 6. Nematocysts of Scolionema sanshin sp. n.. A, B Basitrichous isorhizas, adult medusae. Intact (A), discharged (B) C, D Microbasic euryteles, adult medusae. Intact (C), discharged (D) E, F Basitrichous isorhizas, young medusae. Intact (E), discharged (F) G, H Microbasic euryteles, young medusae. Intact (G), discharged (H) Ovoid isorhizas, young medusae. Intact (I), discharged (J) Microbasic euryteles, mature polyp. Intact (K), discharged (L). Scale bars: 5 µm (E – F), 10 µm (A – D, G – L).

FIGURE 7. Maximum-likelihood tree for 11 limnomedusan taxa based on the nuclear 18 S rDNA data set. Scale bars indicate branch length in substitutions per site. Nodal support values are presented as the ML bootstrap value; only values> 50 % are shoWn.