Clytia gregaria ( L. Agassiz, 1862 )

Peter Schuchert, 2017, Systematic notes on some leptomedusa species with a description of Neotima galeai n. spec. (Hydrozoa, Cnidaria), Revue suisse de Zoologie 124 (2), pp. 351-375 : 370-371

Clytia gregaria ( L. Agassiz, 1862)

Oceania gregaria L. Agassiz, 1862: 353 .

Clytia osterudi Strong, 1925: 389 , pl. 37, hydroid.

Phialidium gregarium . ‒ Murbach & Shearer, 1903: 179, pl. 20. – Kramp, 1961: 167, 444. ‒ Kramp, 1962: 25. – Kramp, 1968: 78, fig. 206. ‒ Roosen-Runge, 1970: 217, figs. 2-25, hydroid. – Arai & Brinckmann-Voss, 1980: 104, figs 59-60.

Clytia gregaria . – Bouillon, 1995: 233. ‒ Bouillon & Barnett, 1999: 99, fig. 101.

Material examined: Several specimens; USA, Friday Harbor Laboratories, floating docks, 48.545141°N 123.012059°W, 0.5 m depth; collection date 23.05.2011; DNA was isolated from two individuals, DNA 920 giving the sequences 16S MF000539 , COI MF000499 ; DNA isolate 1169 yielding the 16S sequence MF000540 . Specimens without black pigment; archived document see Table 1.

Diagnosis: Umbrella up to 22 mm wide, hemispherical to lens-shaped. Manubrium small, attached on a short gastric peduncle of variable height, manubrium base cross-shaped and attached to peduncle, mouth with 4 long, folded lips. Gonads linear, undulated, along distal half to two-thirds of radial canals, not touching circular canal; females with> 100 eggs per gonad. Marginal tentacles 60-80, marginal bulbs nearly globular, few or no bulbs without tentacles when fully grown; l statocyst (or rarely 2 or 3) between successive tentacle bulbs, usually 1, sometimes 2 concretions per statocyst. Without colour or gonads pale yellow to salmon. With or without variable amounts of black or dark brown pigment on margin of lips, gonads, marginal bulbs and ring canal.

Distribution: Shallow waters of coastal regions of the NE Pacific Ocean, from British Columbia to Oregon ( Arai & Brinckmann-Voss, 1980). Bouillon (1995) and Bouillon & Barnett (1999) recorded it also from New Zealand, mostly in deeper waters. Type locality: Strait of Georgia, British Columbia, Canada, Pacific Ocean.

Similar species: Preserved and damaged material of this medusa can easily be confounded with Eirene mollis Torrey, 1909 (see Arai & Brinckmann-Voss, 1980 for description). Eirene mollis has up to 180 tentacles and a somewhat more pronounced gastric peduncle. It is not known if it has excretory papillae.

Remarks: A summary on the identity, taxonomy, biology, and distribution of this species is given in Arai & Brinckmann-Voss (1980). This is a locally very common medusa. It has served for a large number of experimental studies (mostly using the superseded name Phialidium gregariaum , e.g. Dabiri et al., 2010; Freeman, 2005; Colin & Costello, 2002; Colin et al., 2003; Costello & Colin, 2002; Ridgway & Freeman, 1999; Mills, 1981; and many more references given in these works).

The hydroid of Clytia gregaria has been raised from the medusae several times but it was not possible to relate it to colonies sampled in nature ( Arai & Brinckmann-Voss, 1980). The 16S and COI barcode sequence of the present material will hopefully help to identify its polyp stage in nature (cf. Schuchert et al., 2017).

Although rather shallow and sometimes absent, the gastric peduncle of Clytia gregaria is rather unusual for the genus Clytia and makes the medusa very prone to be mistaken for an Eirene species, e.g. the sympatric Eirene mollis Torrey, 1909 . Some Eirene species (cf. Schuchert, 2017) with a shallow peduncle and no excretory papillae could thus turn out to be Clytia species.

Figures

Fig. 18. Clytia gregaria, bell diameter about 20 mm, after photographs of living specimens. (A) Lateral view. (B) Oral view. (C) Bell margin in oral view with three tentacles and 3 statocysts.