Hydractinia pacifica Hartlaub, 1905

Galea, Horia R., 2007, Hydroids and hydromedusae (Cnidaria: Hydrozoa) from the fjords region of southern Chile, Zootaxa 1597 (1), pp. 1-116 : 23-25

Hydractinia pacifica Hartlaub, 1905

(fig. 6G–K, pl. 1D–G)

Hydractinia pacifica Hartlaub, 1905: 519 , figs B–D; Stepanjants, 1979: 14, pl. 1 fig. 10.

Material examined. Stn. COM 02 —22.i.2006, 20– 25 m, S98: one sterile colony, on polychaete tube ( MHNG INVE 53352). Stn. COM 03 —25.ii.2005, 15– 25 m, S69: a sterile colony on polychaete tube ( MHNG INVE 53255); 21.i.2006, 17– 21 m, S153: one sterile colony on polychaete tube ( MHNG INVE 53475). Stn. COM 07 —25.xii. 2004, 22 m, S57: a small, sterile colony, epizoic on Plumularia setacea ( MHNG INVE 53235); 20.i.2006, 5– 10 m, S158: one sterile colony on polychaete tube. Stn. COM 08 —17.i.2006, 8– 20 m, S159: sterile colonies investing two polychaete tubes; 07.11. 2006, 24 m, S171: one colony with female gonophores, on polychaete tube ( MHNG INVE 53507). Stn. COM 09 —04.v. 2005, 20 m, S7: sterile colonies investing five polychaete tubes ( MHNG INVE 53160). Stn. SWA — 15.iii. 2006, 25 m, S131: a sterile colony, on unidentified substrate ( MHNG INVE 53405). Stn. CCA — 12.iii. 2006, 28 m, S87f: a sterile colony, epizoic on Lafoea dumosa ( MHNG INVE 53312). Stn. CFA — 14.iii. 2006, 10 m, S147: some hydranths, without gonophores, epizoic on Bougainvillia pyramidata . Stn. CCO — 09.iii. 2006, 18 m, S144: a small, sterile colony, epizoic on Symplectoscyphus sp. Stn. GDA — 07.iii. 2006, 15 m, S132: one sterile colony, on wood.

Type locality. Calbuco , Chile .

Description. Colonies stolonal, arising from a creeping hydrorhiza firmly attached to external surface of polychaete tubes. Hydrorhiza reticulated, composed of a closely-meshed network of perisarc-covered stolonal tubes. Spines absent. Colony polymorphic, with three types of individuals: gastrozooids, gonozooids and tentaculozooids. All polyps sessile, naked. Polyps pale pink, with hypostome region orange in gastro- and gono- zooids. Gastrozooids claviform to tubular when extended, slightly tapering at base, up to 4 mm high. Hypostome large, rounded-conical, encircled by a row of up to 18 amphicoronate, filiform tentacles. Smaller polyps (probably young gastrozooids) also present within the colony; provided with 7–12 tentacles. A few tentaculozooids scattered among the colony; long (ca 1 cm), slender, with rounded tips, not swollen. Colonies dioecious. Gonozooids with 5–8 filiform tentacles, bearing a ring of 2–4 ovoid gonophores above middle part of their body. Male gonozooids smaller than female ones, and both smaller than gastrozooids. Gonophores styloid, borne on short pedicels, often in opposite directions. Female gonophores containing one large egg; spadix trifid or quadrifid in more mature gonophores. Egg yellow, spadix orange. Male gonophores containing a homogenous mass of sperm cells. Cnidome:

a) microbasic euryteles in tentacles of gastrozooid, undischarged (9.2–10.3) x (3.4–3.9) µm;

b) desmonemes in tentacles of gastrozooid, undischarged (6.3–6.8) x (3.4–3.7) µm;

c) microbasic euryteles in tentaculozooids, undischarged (8.8–9.5) x (3.3–4.0) µm, discharged (7.0–7.3) x (5.8–3.3) µm.

World distribution. Kerguelen ( Stepanjants 1979).

Records from Chile. This species was previously reported from Calbuco ( Hartlaub 1905). The present material has a range of distribution between 42°10' S and 51°40' S .