Halecium halecinum ( Linnaeus, 1758 )

Halecium halecinum ( Linnaeus, 1758) View in CoL

( Figures 3 View Figure 3 , 4 View Figure 4 )

Sertularia halecina Linnaeus 1758, p 809 .

Halecium geniculatum Norman 1867, p 205 View in CoL .

[Not H. geniculatum Nutting View in CoL 18995 H. tenellum Hincks 1861 View in CoL .]

Halecium halecinum: Broch 1911, p 22 View in CoL , Figure 22; Broch 1918, p 36, Figures 11 View Figure 11 , 12 View Figure 12 ; Naumov 1969, p 482, Figures 16K, 335, Plate 17 Figure 3 View Figure 3 ; Vervoort 1972, p 25, Figure 3a View Figure 3 ; Cornelius 1975, p 393, Figure 6 View Figure 6 , synonymy; Millard 1975, p 150, Figure 49A–H; Cornelius 1995, p 279, Figure 63; Medel and Vervoort 2000, p 14, Figure 2 View Figure 2 , bibliography; Schuchert 2001, p 78, Figure 64A, B.

Not Halecium halecinum var. minor Pictet 1893, p 20 View in CoL , Plate 1 Figures 14 View Figure 14 , 15 View Figure 15 ; Schuchert 2003, p 153.

Material examined

MHNG INVE 34732 , France, Baie de Seine , 17 September 1987 , dredged at 25 m depth, female and male colonies. MHNG INVE 26671 , France, Brittany, Roscoff, Roscoff Bretagne, coll. September 1995 . MHNG INVE 27667 , Canary Islands, Lanzarote , 23 September 1999, coll. A. Faucci. MHNG INVE 33575 ( BIOFAR station 205), 62.06 ° N, 5.89 ° W, 160 m, 11 May 1988 GoogleMaps , with female gonothecae, colony form atypical. MHNG INVE 33580 ( BIOFAR station 402), the Faroes , 62.1 ° N, 8.14 ° W, 121 m, 30 May 1989 GoogleMaps , with male gonothecae. MHNG INVE 33582 ( BIOFAR station 350), the Faroes , 62.26 ° N, 7.99 ° W, 107 m, 22 July 1988 GoogleMaps , typical female colonies. MHNG INVE 33587 ( BIOFAR station 554), 61.94 ° N, 6.49 ° W, 62 m, 22 September 1989 GoogleMaps , no gonothecae, typical colony form. BIOFAR station 111, 62.12 ° N, 6.50 ° W, 50 m, 25 July 1987 GoogleMaps , one female gonotheca present. BIOFAR station 351, 62.26 ° N, 7.77 ° W, 102 m, 22 July 1988 GoogleMaps , with female gonothecae. BIOFAR station 597, The Faroes , 62.17 ° N, 6.22 ° W, 100 m, 11 April 1990 GoogleMaps , male gonothecae present.

Description

Colonies erect, stiff, up to 10 cm high, colony form often regularly pinnate, sometimes irregular or with several pinnate side-branches. Side-branches alternate, straight, evenly spaced, at constant angle of 40–60 ° to main axis, secondary branching possible. Stem and main branches polysiphonic, thinning out to terminal monosiphonic branches. Segments of similar length within a region of the colony, segment length much variable among colonies, nodes approximately transverse. Hydrotheca sitting on a shallow hydrophore which is oblique to main axis of internode, opening plane inclined. Hydrothecae alternate, walls straight, with desmocytes, hydrotheca diameter at base 0.12–0.14 mm, depth 30–50 mm. Secondary hydrothecae frequent, on a long hydrophore, the latter at least twice as long as diameter, secondary hydrophore near base usually with a kink. Male gonotheca clubshaped, length about 0.9 mm, aperture terminal. Female gonotheca paddle-shaped, tapering below, distally having a terminal aperture on one side and with right-angled ‘‘shoulder’’ on other side, aperture formed by a fused pair of hydrothecae that overtops gonotheca like a chimney, one or two polyps protruding from aperture, one to four eggs. Nematocysts: two types, type I (8–9.5)X(3.5–4) mm, type II (5–6)X(1.5–2) mm.

Distribution

East and West Atlantic , Mediterranean, South Africa , Pacific, Arctic Seas. Type locality: Whitstable , Kent, England .

Remarks

As discussed under H. scutum , this species can be difficult to distinguish from H. scutum and H. beanii . In waters around the British Isles and continental Europe, Halecium halecinum often forms quite regular, pinnate colonies ( Figure 3A, C View Figure 3 ). Cornelius (1995) considers this an important diagnostic trait of the species. In the material from the Faroes, the colonies were often quite irregular ( Figure 3B View Figure 3 ). The pinnate colony form, however, is also found in Faroese waters ( Figure 3C View Figure 3 ). Also some of the colonies examined from the English Channel were not so obviously pinnate. Hincks (1868, Plate 42, Figure a) depicted a colony originating from the British Isles which also deviates somewhat from the strictly pinnate form shown in the same plate. The colony form of H. halecinum is therefore not always regularly pinnate. But if present, the pinnate colony form is certainly a diagnostic trait of H. halecinum . Infertile or male colonies with atypical colony form can be impossible to identify if they are not part of a larger series that also includes fertile females.

Broch (1918) thought that the shape of the secondary hydrothecae in H. halecinum differs from those of H. beanii in having an asymmetric adcauline wall. Such a difference was not found in the material examined here and neither was it mentioned by Cornelius (1995) (compare Figures 4 View Figure 4 A–C and 5D, F). Millard (1966, 1975) also found that only the female gonotheca allows a reliable identification. Medel and Vervoort (2000) found that side-branches arise frontally or at the rear in H. halecinum , while in H. beanii they arise laterally.