Halecium fraseri Ralph 1958

Halecium fraseri Ralph, 1958

(fig. 2C–K, table 1)

Halecium fraseri Ralph, 1958: 338; Leloup, 1974: 11, fig. 8.

Halecium flexile: Fraser, 1914: 165, pl. 20 fig. 71; Fraser, 1937: 104, pl. 21 fig. 111; Fraser, 1944: 192, pl. 35 fig. 169; Fraser, 1946: 73, 264; Fraser, 1948: 222.

Material examined. Stn. RM 1 – 09.iii.2007, Fjord Piti Palena, Raul Marin, 43°46.510’ S, 72°52.706’ W, 15– 20 m, boulder on sandy ground: one male and one female colony, both bearing numerous gonothecae (MHNG INVE 54634).

Type locality. Nanoose Bay, off West Rocks, Vancouver Island region, Canada. The type locality was selected by Ralph (1958) as the first named locality given for the species by Fraser (1914).

Description. Colonies up to 12 cm high, planar, arising from root-like stolons, firmly attached to substrate. Stems erect, branched or unbranched, giving rise to side branches in a regularly pinnate manner. Both main stem and branches polysiphonic, thinning out to monosiphonic at distal end; divided into long, roughly equal internodes; nodes, though indistinct, transverse to slightly oblique; an incision of perisarc at distal end of internode, on side next to adcauline base of primary hydrophore. Side branches originating directly under a primary hydrotheca and placed on small apophysis, forming annulus at junction of the two. Abcauline wall of primary hydrophore at place of fusion with basal part of side branch having characteristic, comma-shaped, internal projection of perisarc (fig. 2E). Side branches alternate, straight to slightly flexuose, evenly spaced, and at a constant angle of ca 45° to main stem; some secondary branches occur. Primary hydrophore prominent, surpassing distal node of segment and not delimited by basal constriction; pseudodiaphragm always present, at least below primary hydrotheca. Hydrothecae alternate; short, asymmetric, with abcauline side nearly straight and adcauline side flared. Rim even, very slightly everted; wall of hydrotheca with row of desmocytes; renovations often present (up to 6). Length of additional secondary hydrophores varied, longer than diameter; basally with undulated perisarc, elsewhere smooth. Hydranths with 16–20 filiform tentacles.

Gonothecae inserted below hydrothecae on primary hydrophores. Male club-shaped in frontal view, tapering basally, with distal end only slightly curved (fig. 2J); flattened laterally. Female similar to male, but shorter; with 3– 5 eggs embedded in tissue of ovoid shape; embryos developing in externally held acrocysts (fig. 2I).

Nematocysts: microbasic mastigophores, (6.2–6.8) × (2.0–2.4) µm (undischarged) and ca 5.6 × 2.1 µm (discharged).

Chile, present study

Stem internodes

– length 704–841 – diameter 143–159 – diameter at node 116–131 Hydrothecae

– primary hydrophore length 130–157 – primary hydrophore diameter 107–111 – height 24–30 – diameter at rim 143–148 – diameter at base 119– 122 Female gonotheca

– length 1084–1292 – maximum width 365–477 – thickness 270– 309 Male gonotheca

– length 1410–1718 – maximum width 352–476

Remarks. The hydroid now known as Halecium fraseri Ralph, 1958 was initially misidentified by Fraser (1914) as H. flexile Allman, 1888 (= H. delicatulum Coughtrey, 1876). Ralph (1958) noted in detail the important differences between Fraser’s material and Allman’s species, and provided a new name for it.

Leloup (1974) described the female gonothecae for the first time, reporting ca 2– 4 eggs per gonotheca. In our material, we found 3– 5 eggs per gonotheca, and embryos developing in external acrocysts.

World distribution. Eastern Pacific, from Moresby Island (British Columbia, Canada), to the San Juan Archipelago (Ralph 1958); northwestern Atlantic, from Narragansett Bay, south of Hope Island (Fraser 1944).

Records from Chile. Gulf of Ancud (Leloup 1974), Fjord Piti Palena (present study).

Ecology. This species has been found on boulders in an area dominated by sandy substrates, at depths between 15– 20 m.