Halecium fjordlandicum, Galea, 2007

Galea, Horia R., 2007, Hydroids and hydromedusae (Cnidaria: Hydrozoa) from the fjords region of southern Chile, Zootaxa 1597 (1), pp. 1-116 : 56-58

Halecium fjordlandicum sp. nov.

(fig. 13A–D, pl. 2C–I, table 18)

Material examined. Stn. COM 06 —26.i.2006, 20– 23 m, S95: one sterile colony, less than 1 cm high, on tunicate ( MHNG INVE 53342 ) . Stn. COM 10 —22.i.2006, 15– 20 m, S162: several sterile stems and fragments, up to 4 cm high ( MHNG INVE 53487 ) . Stn. COM 13 —25.i.2006, 25– 32 m, S94, holotype: several sterile stems and fragments, up to 4 cm high, on dead gorgonian ( MHNG INVE 53340 ) .

Type locality. Punta Gruesa , fjord Comau, Chile .

Description. Colonies up to 4 cm high; stem slightly polysiphonic basally, grading rapidly to monosiphonic; divided into long internodes by slightly oblique nodes; perisarc relatively thin and transparent. Internodes slightly curving, giving the stem a slightly geniculate appearance; each internode with a distal hydrotheca, alternately disposed left and right and slightly pointing forward; hydrotheca shallow, borne on short hydranthophore oblique to main axis of internode; walls slightly diverging distally; rim of hydrotheca generally not surpassing level of distal node; circular, even, opening plane inclined; desmocytes visible as refringent nodules. Side branches generally alternate, borne on quite long stem apophyses originating below stem hydrothecae, the latter becoming thus axillar; structure of branches similar to that of caulus. Renovations present in some hydrothecae, with most often only one renovation, but up to 3 sometimes observed; secondary hydrothecae borne on quite long hydrophores, basal part of secondary hydrophore with a kink. Hydranths with 22–26 filiform tentacles. Gonothecae not found. Cnidome (plate 2F–I):

a) large macrobasic mastigophores, in a sheath around middle part of hydranth body, undischarged (15.2– 16.2) x (7.1–7.6) µm, discharged (12.6–13.6) x (5.2–6.0) µm, shaft more than 10 times longer than exploded capsule;

b) small microbasic mastigophores on tentacles, undischarged (6.3–6.8) x (1.8–2.1) µm, discharged (5.2– 5.8) x (1.6–1.8) µm.

Remarks. Halecium fjordlandicum shares several characteristics with H. halecinum ( Linnaeus, 1758) , i.e. the mode of branching, the uniformity in length of internodes within a colony, the shape and position of hydrothecae and their corresponding hydrophores. However, the cnidome is different in the two species (see Schuchert 2005), and only H. fjordlandicum possesses a sheath of large macrobasic mastigophores on the hydranth body.

Etymology. Named after the geographic area of occurrence, i.e. the fjords region of southern Chile.

Records from Chile. This rare species was found only three times in fjord Comau, where extensive hydroid samplings were undertaken. However, its occurence along the coast of southern Chile is entirely plausible.