Halecium halecinum ( Linnaeus, 1758 )

Schuchert, Peter, 2005, Taxonomic revision and systematic notes on some Halecium species (Cnidaria, Hydrozoa), Journal of Natural History 39 (8), pp. 607-639 : 612-614

Halecium halecinum ( Linnaeus, 1758)

( Figures 3 , 4 )

Sertularia halecina Linnaeus 1758, p 809 .

Halecium geniculatum Norman 1867, p 205 .

[Not H. geniculatum Nutting 18995 H. tenellum Hincks 1861 .]

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

Not Halecium halecinum var. minor Pictet 1893, p 20 , Plate 1 Figures 14 , 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 , 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 , with male gonothecae. MHNG INVE 33582 ( BIOFAR station 350), the Faroes , 62.26 ° N, 7.99 ° W, 107 m, 22 July 1988 , typical female colonies. MHNG INVE 33587 ( BIOFAR station 554), 61.94 ° N, 6.49 ° W, 62 m, 22 September 1989 , no gonothecae, typical colony form. BIOFAR station 111, 62.12 ° N, 6.50 ° W, 50 m, 25 July 1987 , one female gonotheca present. BIOFAR station 351, 62.26 ° N, 7.77 ° W, 102 m, 22 July 1988 , with female gonothecae. BIOFAR station 597, The Faroes , 62.17 ° N, 6.22 ° W, 100 m, 11 April 1990 , 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 ). 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 ). The pinnate colony form, however, is also found in Faroese waters ( Figure 3C ). 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 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.

Figures

Figure 2. Halecium scutum Clark, 1877. (A) From BIOFAR 699; (B) BIOFAR 556; (C–E) Holsteinsborg, Greenland; (F, G) Augpilagtoq, Greenland. (A–C, F) Segments from monosiphonic parts with primary and sometimes secondary hydrothecae (scale bar: 0.2 mm); (D) female gonotheca in side view, eggs stippled (scale bar: 0.2 mm); (E) higher magnification of gonothecal opening, side view (scale bar: 0.1 mm); (G) male gonotheca (same scale bar as D).

Figure 3. Halecium halecinum (Linnaeus, 1758); colony silhouettes, note variation of shapes. (A) Canary Islands; (B) The Faroes (BIOFAR station 111); (C) The Faroes (BIOFAR station 554). Scale bar: 2 cm.

Figure 4. Halecium halecinum (Linnaeus, 1758). (A–C) Segments of monosiphonic parts, with secondary hydrothecae, note length variation of internodes, BIOFAR station 350, 205 and 351; (D) BIOFAR 351, female gonotheca in side view; (E) as in (D), but seen from anterior side, note bipartite hydrotheca; (F) BIOFAR 597, male gonotheca. Scale bar: 0.2 mm.

Figure 6. Halecium beanii (Johnston, 1838). (A–D) After material from South Africa; (E–F) after material from New Zealand. (A) Two internodes (scale bar: 0.2 mm); (B) female gonotheca in oblique view (scale bar: 0.2 mm); (C) cross-section of female gonothecae in about the middle of its height, note polygonal outline (same scale bar as B); (D) three male gonothecae, note variability (same scale bar as B); (E) two internodes (same scale bar as A); (F) female gonotheca (same scale bar as B).

Figure 11. Halecium mediterraneum Weismann, 1883; after preserved Mediterranean material. (A) Silhouettes of three fertile colonies showing variability of growth (scale bar: 1 cm); (B) branching pattern of stem (scale bar: 0.2 mm); (C) distal part with geniculate segments (same scale bar as B); (D) primary and secondary hydrotheca (scale bar: 0.1 mm); (E–G) female gonothecae (same scale bar as B), (E) in frontal view and with broad opening, (F) in side view, (G) most commonly found opening size; (H–K) male gonothecae (same scale bar as B), (H) with soft tissue, (I) empty, (K) in side view; (L) empty female gonotheca cut apart to demonstrate secondary capsule within outer capsule (scale bar: 0.1 mm); (M) range of variation of distal openings of female gonothecae (same scale bar as L).

Figure 12. Halecium delicatulum Coughtrey, 1876, after preserved material from New Zealand. (A) Segment with primary and secondary hydrotheca; (B) female gonotheca, broad view. Scale bar: 0.1 mm.

Figure 14. Halecium banyulense Motz-Kossowska, 1911, after MHNG INVE 34237. (A) Colony silhouette (scale bar: 1 cm); (B) internode from monosiphonic part (scale bar: 0.2 mm); (C) hydrothecae with regenerated hydrothecae of second and higher degree (scale bar: 0.1 mm); (D) female gonotheca, drawn opaque to visualize radiating depressions (same scale bar as B).

Figure 15. Halecium corrugatissimum Trebilcock, 1928. (A) Part of stem with hydrotheca and secondary hydrothecae (scale bar: 0.1 mm); (B) same as (A), note distance of hydrotheca from side-branch and apophysis; (C, D) female gonothecae with eggs (stippled) (scale bar: 0.2 mm); (E, F) male gonothecae (same scale bar as C, D).