Halecium beanii ( Johnston, 1838 )

Schuchert, Peter, 2005, Taxonomic revision and systematic notes on some Halecium species (Cnidaria, Hydrozoa), Journal of Natural History 39 (8), pp. 607-639 : 615-618

Halecium beanii ( Johnston, 1838)

( Figures 5 , 6 )

Thoa beanii Johnston 1838, p 120 , Plate 7 Figures 1 , 2 .

Halecium beanii: Broch 1918, p 38 , Figure 13 ; Millard 1975, p 144, Figure 47A–E; Cornelius 1995, p 276, Figure 62; Hirohito 1995, p 17, Figure 3 d–f, Plate 1 Figure A; Medel and Vervoort 2000, p 8, Figure 1 , bibliography; Vervoort and Watson 2003, p 86, Figure 15 D–H.

In part Halecium beanii: Ralph 1958, p 332 , Figure 10a, b , e–k; Naumov 1969, p 483, Figures 19G, H, 336; Schuchert 2001, p 73, Figure 59A–D.

? Halecium lankesterii: Hamond 1957, p 302 , Figures 9 , 10 ; Vervoort 1959, p 221, Figures 3–5 ; Cornelius 1995, p 285, Figure 65.

Material examined

MHNG INVE 33451 , France, Brittany, Roscoff , between Islets Astan and Ty Saozon, 24 May 1910 , leg. M. Bedot, with female gonothecae. MHNG INVE 33556 ( BIOFAR station 193), The Faroes , 62.41 ° N, 6.91 ° W, 10 May 1988, 108 m, with female gonothecae. MHNG INVE 33593 ( BIOFAR station 111), The Faroes , 62.11 ° N, 6.50 ° W, 50 m, 25 July 1987 . MHNG INVE 32968 , Mediterranean, France, off Banyuls-sur-Mer , 62 m, 15 May 2002 , on shell debris, with typical female gonothecae, polysiphonic. MHNG INVE 34011 , South Africa, Simon’s Town, Boulder Beach , coll. P. Schuchert, 11 January 2003 , 1– 2 m depth, several female and male colonies. MHNG INVE 25068 , New Zealand, Devonport, Cheltenham Beach , coll. P. Schuchert, 14 October 1998 , preserved as three slides, with female gonothecae.

Description of European material

Colonies 1–10 cm, irregularly branched, varied in appearance. Fertile colonies polysiphonic, thinning out to monosiphonic. Internode length of one colony relatively homogeneous, variable between colonies. Nodes alternately oblique. Hydrotheca sitting on a shallow hydrophore, the latter held oblique to main axis of internode, opening plane of hydrotheca inclined. Hydrothecae alternate, not adnate to internode, rim not overtopping level of distal node. Hydrotheca with straight walls, walls not much diverging, diameter at level of diaphragm 0.12–0.16 mm, depth 25–45 mm. Secondary hydrothecae frequent, their hydrophores long, length two to four times longer than diameter, often with basal kink. Female gonotheca 1–1.2 mm long, curved, approximately kidney-shaped, in middle of concave side two fused hydrothecae, in side-view held oblique, without hood-like cover, normally with two hydranths (may be reduced), convex side of gonotheca without longitudinal crests or crease-lines, four to six eggs per gonotheca, develop in situ into planulae. Male gonothecae club-shaped with terminal aperture, length up to 1 mm, breadth up to 0.25 mm. Nematocysts: two types of capsules, type I is a heteroneme (13–15)X(6–6.5) mm; type II (5.5–6.5)X(1.5–2) mm.

Characteristics of South African material

Like European material, but hydrothecae adnate; female gonotheca with polygonal crosssection and with five to six longitudinal crease-lines or shallow ridges, egg number 8–20. Male gonotheca also polygonal in cross-section, but more irregular, distal end often wedgeshaped, aperture terminal. Nematocysts: two types of capsules, larger one is a macrobasic eurytele (11–12)X(4–5) mm; smaller one as above.

Characteristics of Neae Zealand material

Like European material, but hydrothecae adnate and smaller, diameter 0.10 mm, depth 25–30 mm. Female gonothecae also identical to European population, with four to five embryos or eggs.

Distribution

Considered to be nearly cosmopolitan, found in mostly shallow to moderately deep waters (0–150 m). Type locality: near Scarborough , Yorkshire, England ( Cornelius 1975) .

Remarks

The examined fertile female colonies from the northern Atlantic and Mediterranean were all rather small and delicate (see Figure 5 A–C). One sample ( MHNG INVE 33593) was particularly confusing as it was growing on a large colony of H. scutum . There were female as well as male stems present, although in different regions. The host had therefore been colonized by several, independent colonies (genets). The gonothecae bearing shoots included typical, polysiphonic ones, but also many monosiphonic ones. These monosiphonic colonies were thus hardly distinguishable from H. lankesterii sensu Cornelius (1995) , a species closely resembling H. beanii . The principal difference between H. lankesterii and H. beanii according to Cornelius (1995) are the monosiphonic stems in the former versus polysiphonic stems in the latter. Halecium lankesterii is, however, doubtless a valid species and comparison with material from Brittany showed that it is distinct from H. beanii . I suspect that at least some material identified as H. lankesterii by Hamond (1957), Vervoort (1959) and Cornelius (1995) was in fact monosiphonic H. beanii (see under H. lankesterii ).

The microscopic structure of Halecium beanii is almost identical to that of H. halecinum (cf. Millard 1966, 1975). Both species can only reliably be distinguished by comparing the female gonothecae. Halecium halecinum additionally forms often quite regularly pinnate colonies, which helps to distinguish it from H. beanii and H. scutum (compare Figures 1 A– C, 3A–C and 5A–C).

Naumov (1969) synonymized Halecium scutum Clark, 1877 and H. beanii , a view later hesitatingly adopted by, for example, Cornelius (1975) and myself ( Schuchert 2001). However, examination of the material described in this report convinced me that H. scutum is a distinct species. The female gonothecae of the two species allow a distinction. There are also significant differences in the colony size and details of the hydrotheca (see under H. scutum ). The occurrence of H. beanii on a colony of H. scutum described above strongly argues in favour of them being distinct. Vervoort (1972) and Hirohito (1995) also thought that they are separate species.

The material of H. beanii from New Zealand described above was in no significant way different from European specimens, confirming the reports of Ralph (1958). However, part of Ralph’s material allocated to H. beanii has recently been attributed to a new species, Halecium ralphae , by Watson and Vervoort (2001). The female gonothecae of this species is strongly curved, forming nearly a complete circle. Watson and Vervoort (2001) postulated also that H. beanii has female gonothecae with one hydrotheca only. This is evidently not the case, as also all here examined female gonothecae had a pair of fused hydrothecae.

The material from South Africa deviated in several aspects from European specimens. Especially the female gonothecae with their polygonal cross-section and the longitudinal ridges or crease-lines rendered it distinct. Also the increased egg number per gonotheca is a significant difference. Following the general practice in current hydrozoan systematics, all these differences would justify the postulation that the South African population belongs to a different species. Because the limited number of examined colonies does not allow the variability of the South African population to be assessed, no new name is proposed here.

Figures

Figure 1. Halecium scutum Clark, 1877; colony silhouettes of material from The Faroes. (A) MHNG INVE 33550; (B) BIOFAR station 699; (C) BIOFAR station 459. Scale bar: 2 cm.

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 5. Halecium beanii (Johnston, 1838). (A, D) From Roscoff; (B, C, E–H) from The Faroes. (A–C) Colony silhouettes (scale bar: 1 cm); (D–F) subterminal portions of branches (scale bar: 0.2 mm); (G) female gonotheca, middle one seen from side of hydrothecae, right one shown with developing embryos (scale bar: 0.2 mm); (H) male gonotheca (same scale bar as G).

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 9. Halecium labrosum Alder, 1859. (A, B) From Roscoff; (C, D) from The Faroes, MHNG INVE 33524 and 33581; (E) MHNG INVE 25337, Iceland; (F) MHNG INVE 26684, Iceland; (G) MHNG INVE 28451, Greenland. (A) Silhouette of infertile colony (scale bar: 1 cm); (B–D) internodes and secondary hydrothecae (scale bar: 0.2 mm); (E) female gonotheca (scale bar: 0.5 mm); (F) distal opening of female gonotheca (scale bar 0.1 mm); (G) male gonotheca (same scale as E).

Figure 10. Halecium labrosum Alder, 1859. (A–D) MHNG INVE 33563, Iceland; (E–G) MHNG 33583, The Faroes. (A) Colony silhouette (scale bar: 1 cm); (B) segments of distal branch, note short internodes (scale bar: 0.2 mm); (C) gonotheca (scale bar: 0.5 mm); (D) distal opening of gonotheca (scale bar: 0.2 mm); (E) colony silhouette (scale bar: 1 cm); (F) segments of distal branches, note variability of internode length; (G) gonotheca (scale bar: 0.5 mm).

Figure 13. Halecium textum Kramp, 1911; after MHNG INVE 33592, Iceland. (A, B) Hydrothecae and internodes, note strong corrugation (scale bar: 0.1 mm); (C) part of colony with three female gonothecae, eggs stippled (scale bar: 0.5 mm).

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).