Hydractinia sp.

Galea, Horia R., 2007, Hydroids and hydromedusae (Cnidaria: Hydrozoa) from the fjords region of southern Chile, Zootaxa 1597 (1), pp. 1-116 : 25-26

Hydractinia sp.

(fig. 7A, B)

Material examined. Stn. COM 08 —17.i.2006, 8– 20 m, HG009: a fertile colony, with medusa buds, investing a gastropod shell ( MHNG INVE 53508 ) .

Description. Hydrorhiza reticulate, frequently branching and anastomozing, covering surface of a gasteropod shell. Spines absent. Colony dimorphic. Gastrozooids with rounded-conical hypostome and 9–15 filiform tentacles. Gonozooids smaller than gastrozooids, with 5–8 filiform tentacles; with up to 5 gonophores in a row around middle part of body. Gonophores liberated as free-swimming medusae with 8 well-developed marginal tentacles. Cnidome (gastrozooid):

a) microbasic euryteles, with shaft only slightly dilated, discharged (8.3–9.3) x 2.7 µm, undischarged (7.7–8.0) x (2.7–3.3) µm;

b) desmonemes, discharged ca 4.0 x 2.3 µm, undischarged (5.3–6.0) x (3.0–3.3) µm.

Remarks. The present material may belong to H. borealis ( Mayer, 1900) , but this identification should remain provisional since no rearing experiments were done with the medusa. However, adult medusae of H. borealis were abundant in the same area as the present hydroid material. Moreover, medusa buds in the present specimens have 8 well-developed marginal tentacles, a situation similar to the observation made by Rees (1941) on the newly-liberated medusa of H. borealis . In addition, the nematocyst complement of the polyp stage is in agreement with Schuchert’s (2001a) observations. The presence of spines or tentaculozooids in this species is a variable phenomenon, as stated by Rees (1941) and Bouillon et al. (2004).

Records from Chile. The present specimen originates from fjord Comau.