Clytia linearis ( Thornely, 1900 )

Mendoza-Becerril, María A., Estrada-González, Mariae C., Mazariegos-Villarreal, Alejandra, Restrepo-Avendaño, Luisa, Villar-Beltrán, Rogelio D., Agüero, José & Cunha, Amanda F., 2020, Taxonomy and diversity of Hydrozoa (Cnidaria, Medusozoa) of La Paz Bay, Gulf of California, Zootaxa 4808 (1), pp. 1-37 : 22-23

Clytia linearis ( Thornely, 1900)

Figs. 8 A–H

Obelia linearis Thornely 1900: 453 , pl. 44, fig. 6.

Clytia acutidentata Fraser 1938a: 28 , pl. 7, fig. 29.— Fraser 1938b: 109.— Fraser 1948: 206.

Gonothyraea serialis Fraser 1938a: 35 , pl. 8, fig. 37.— Fraser 1938c: 133.— Fraser 1948: 212.

? Clytia striata .— Álvarez-Léon & Wedler 1982: 27, figs. 2g, 5e [not Clytia striata ( Clarke, 1907) ].

Clytia linearis .— Calder 1996: 258, fig. 2.— Humara-Gil & Cruz-Gómez 2018: 458 , fig. 3.

Type locality. Papua New Guinea: Blanche Bay , New Britain ( Thornely 1900) .

Material examined. Medusa—PB7_1b, sampling site 1 (2), mature, females 27°C; PB7_20, sampling site 2 (2), mature, one female and one male, 27°C. Polyp—PB7_27, sampling site 1 (1), mature, 27°C, on cirripeds; PB7_ 32, sampling site 2 (1), immature, 27°C, on Sargassum ; PB7_38, sampling site 3 (1), immature, 26.5°C, on alga.

Description. Medusa—Umbrella slightly flattened, hemispherical (1.5–2.3 mm wide, 0.5–1.6 mm high), with narrow velum. Manubrium short and quadrangular (0.3 mm long, 0.3–0.9 mm wide), without peduncle, mouth with four simple lips. Circular canal and four radial canals narrow. Gonads oval (0.1–0.6 mm long), with median groove and without peduncle, located on the middle of radial canals in small specimens or on the distal portion of radial canals in large specimens. Eight to 16 hollow marginal tentacles, each associated with a tentacle bulb. Eight to 15 ectodermal closed statocysts, each with one statolith, alternating with tentacle bulbs.

Polyp—Colonies erect, sympodial, occasionally branching. Erect stems up to 12 mm high, monosiphonic, arising from a creeping hydrorhiza. Internodes 768.4 μm long, slightly curved, each with 4–7 annulations at the base; pedicel with distal hydrotheca. Internodes with upward curved apophysis, adjacent to hydrothecal pedicel, given off the next internode in alternate directions. Pedicels 439.0 μm long, with 5–16 annulations along its whole length. Hydrotheca cylindrical, 822.8 μm long, 476.3 μm wide at margin, 154.6 μm wide at diaphragm, with thin perisarc. Margin with 12–15 acute triangular cusps, often folded inwards, with pleats extending from the tips of the cusps downwards to the upper part of the hydrothecal wall. Hydrothecal diaphragm thin, transverse. Gonotheca cylindrical, smooth, arising from the base of hydrothecal pedicels. Gonothecae pedicels short, with 3–4 annulations. Gonotheca 918.5 μm long, 417.4 μm in maximum diameter, with a small constriction near the aperture (297.3 μm wide), and truncated on top. Up to eight young medusae inside the gonothecae.

Nematocysts (length x diam.). Medusa—Microbasic b-mastigophore type A (7.9–9.1 x 1.6–2.1 µm). Polyp—Mi-crobasic b-mastigophore type A (4.9–6.5 x 1.7–2.2 µm), microbasic b-mastigophore type B (8.7–9.8 x 2.5–3.04 µm).

More detailed description in Calder (1991a) and Lindner & Migotto (2002).

Taxonomic status. Accepted. AphiaID 117370.

Remarks. Clytia striata ( Clarke, 1907) was included in the synonym of C. linearis (Thorneley, 1900) by Calder (1991a), as well as Clytia acutidentata Fraser, 1938a and Gonothyraea serialis Fraser, 1938b from the northeastern Pacific ( Calder 1991a; Calder et al. 2009). However, the shape of the hydrothecal cusps and the fact that C. striata have been frequently reported in association with pteropods ( Clarke 1907; Vervoort 1946) suggest they might be different species. The description and figure of C. striata from Álvarez-León & Wedler (1982) closely agrees with C. linearis (Thorneley, 1900) , but as the status of Clytia striata ( Clarke, 1907) is still not clear, a more detailed study is needed to confirm its identification. Specimens of C. linearis recorded by Humara-Gil & Cruz-Gómez (2018) are smaller in size (colonies 1.4–2.3 mm high and hydrothecae 270 µm long) when compared with our specimens and descriptions from the literature (colonies up to 21.5 mm high and hydrothecae 500–1200 µm long) ( Calder 1991a; Lindner & Migotto 2002; current study). Although their description could be based on early stages of development ( Humara-Gil & Cruz-Gómez 2018), it is also possible that their record represents a different species, but this hypothesis needs to be further investigated.

The diameter of the umbrella, the number of tentacles, and the position of the gonads varied among our medusae specimens, suggesting they represent different stages of development. Considering these variations, as well as the shape of the gonads, they agree with the description of C. linearis (Thorneley, 1900) of Lindner & Migotto (2002). However, it is important to acknowledge that the medusae of Clytia Lamouroux, 1812 are usually challenging to identify due to the paucity of diagnostic characters that frequently overlap among different species, as a result of their ontogenetic variation. Therefore, we stress the importance of additional life cycle studies with species of Clytia to uncover potential morphological and genetic variation of their medusa stage, contributing to species delimitation.

Distribution. Species widely distributed in warm waters of all oceans, occasionally occurring in temperate waters ( Calder 1991a; Lindner & Migotto 2002). In Mexican Pacific, only the polyp phase was reported for the coasts of Baja California ( Isla Partida) ( Fraser 1938b), Baja California Sur (Rocas Alijos) ( Calder 1996), Sinaloa (Mazatlán) ( Álvarez-León & Wedler 1982), Jalisco (Tenacatita Bay) ( Fraser 1938c), Colima (Socorro Island) ( Fraser 1948), Guerrero (White Friars Islands) ( Fraser 1938a), and Oaxaca (Corralero Bay and Santa Cruz Bay) ( Humara-Gil & Cruz-Gómez 2018).

Figures

FIGURE 8. A–H Clytia linearis (Thornely, 1900): A–E, medusa; B, manubrium; C, female and male gonads; D, statocyst; E, nematocysts microbasic b-mastigophore type A; F–H, polyp; G–H, hydrothecae and gonothecae. I–J Clytia simplex (Browne, 1902): I, medusa with gonads; J, manubrium. Scale equals A, G, I—500 µm; B, C, J—200 µm; D—100 µm, E—20 µm; F—1 mm; H—340 µm.