Caltsacoryne setouchiensis, Toshino & Hamatsu & Uchida, 2021

Toshino, Sho, Hamatsu, Yoshimi & Uchida, Hiroaki, 2021, Caltsacoryne setouchiensis (Hydrozoa, Anthoathecata) a new genus and species of hydrozoan jellyfish from Japan, Zootaxa 5032 (1), pp. 87-103 : 96-101

publication ID	https://doi.org/ 10.11646/zootaxa.5032.1.4
publication LSID	lsid:zoobank.org:pub:24E2C6DF-D6AE-4A7A-BEB1-D4F51E917B17
persistent identifier	https://treatment.plazi.org/id/EF7D0F56-FF99-FFCE-0ABC-D9A30E4FDF49
treatment provided by	Plazi
scientific name	Caltsacoryne setouchiensis
status	sp. nov.

Treatment

Caltsacoryne setouchiensis View in CoL sp. n.

New Japanese name: Shitouzu-kurage

Figures 4–7 View FIGURE 4 View FIGURE5 View FIGURE 6 View FIGURE 7

Material examined. Holotype: NSMT-Co 1749. Suo-Oshima , Okikamuro Island, Yamaguchi Prefecture, western Japan, April 24, 2016, collector: Sho Toshino, one adult female medusa . Paratypes. NSMT-Co 1750. Same locality and date as the holotype, collectors: Yoshimi Hamatsu, one adult male. NSMT-Co1751–1753. Same locality as the holotype, April 18, 2018, collector: Hiroaki Uchida, two adult males and one adult female .

Description. Mature medusae with transparent, thick but soft bell-shaped umbrella ( Fig. 4A–C View FIGURE 4 , 5A–C View FIGURE5 ). Umbrella height (UH) and diameter (UD) approximately 7 mm and 4 mm, respectively ( Table 4). Umbrella apex thickened, tapered. Exumbrella smooth, nematocyst sparsely scattered. Bell cavity small. Four radial canals and single straight ring canal. Canals narrow, almost with same diameter. Tentacle bulbs swollen, reddish purple in color, each with abaxial ocellus ( Fig. 6A–C View FIGURE 6 ). Tentacle arising from bulbs, short and terminating in single large egg-shaped swelling covered with nematocysts ( Fig. 6D, E View FIGURE 6 ). Orange band present on middle part of swelling. Mouth simple and circular, whitish in color ( Fig. 6F, G View FIGURE 6 ). Manubrium hanging in bell cavity, large and flask-shaped; rounded at apical side and furnished with small proboscis in distal portion. Extended manubrium length approximately 3 mm and approximately half umbrella height (almost full length of subumbrella). Gonads encircling entire surface of manubrium, with exception of apical and distal portions ( Fig. 6D View FIGURE 6 ). Velum narrow ( Fig. 4C View FIGURE 4 , 5C View FIGURE5 ).

Smallest young medusa with UH of 2.5 mm and UD of 2.6 mm ( Fig. 7A–C View FIGURE 7 ). Umbrella spherical with few exumbrellar nematocysts. Mesoglea on apex of exumbrella thinner than that of adults. Manubrium thin, translucent to whitish, length approximately half that of umbrella. Mouth simple and circular. Gonad immature. Four radial canals and singular circular canal. Velum narrow. Tentacle bulbs swollen, reddish purple, each with dark brown abaxial ocellus. Four tentacles, terminating in single large spherical swelling. Orange band present on middle part of swelling.

2006; d, Huang et al. 2008; e, Forbes 1848; f, Huang et al. 2011; g, Minemizu et al. 2015; h, Torrey 1909.

Cnidome. Two different types of nematocyst were identified and measured in the adult medusa ( Table 5, Fig. 8 View FIGURE 8 ), and two sizes of stenoteles ( Fig. 8A, B View FIGURE 8 ) and desmonemes ( Fig. 8C, D View FIGURE 8 ) were observed on tentacle tips, tentacle bulbs, and manubrium, although small stenoteles were absent from the manubrium. Stenoteles were also found on the bell; however, these could not be measured.

Habitat and ecology. The medusae of C. setouchiensis collected in the present study appeared at the water surface in a shallow area (water depth 3–5 m) during the daytime around the coast of Suo-Oshima, the Seto Inland Sea, in April. They are not active swimmers but drift with the current using their extended tentacles. The species appears to be neritic. In some specimens, mesoglea at the apical part were found to be infested by flukes ( Fig. 6G View FIGURE 6 , 7B View FIGURE 7 ). Stinging events attributable to C. setouchiensis are currently unknown.

Etymology. The specific name “ setouchiensis ” refers to the Setouchi Region, which includes the type locality in which the species was found.

Differential diagnosis. A comparison of the key features of Corynidae species is presented in Table 6. Caltsacoryne setouchiensis can be distinguished from the species of other genera by the following combination of morphological characters: number of tentacles, cnidocyst pads, manubrium length, and shape of the gonads and tentacles in adult medusae. All species in the family Corynidae have four radial canals, circular canals, and marginal tentacle bulbs. Caltsacoryne bears four tentacles, whereas species in the genera Polyorchis , Scrippsia , and Spirocodon typically have more than 100. Whereas most corynids have unbranched filiform tentacles, those in Caltsacoryne , Dicyclocoryne , and Slabberia are unbranched capitate, and Cladosarsia and Dipurenella have branched capitate tentacles. Caltsacoryne lacks adaxial cnidocyst pads on the marginal bulbs, whereas these pads are present in Cladosarsia and Dipurenella . Furthermore, unlike species of Cladosarsia , Dipurenella , Sarsia and Slabberia , the manubrium in Caltsacoryne does not extend beyond the umbrella margin, and in contrast to Dipurenella , Slabberia , and some species of Stauridiosarsia , in which the gonads are divided, those in Caltsacoryne are divided