Halecium scutum Clark, 1877

Schuchert, Peter, 2005, Taxonomic revision and systematic notes on some Halecium species (Cnidaria, Hydrozoa), Journal of Natural History 39 (8), pp. 607-639: 608-612

publication ID

http://doi.org/ 10.1080/00222930400001319

persistent identifier

http://treatment.plazi.org/id/4B6087F1-8B48-FFCD-CB8E-F99EFD67FCA5

treatment provided by

Carolina

scientific name

Halecium scutum Clark, 1877
status

 

Halecium scutum Clark, 1877  

( Figures 1 View Figure 1 , 2 View Figure 2 ) Halecium scutum Clark 1877, p 14   , Plate 4 Figures 13 View Figure 13 , 14 View Figure 14 ; Broch 1918, p 39, Figures 14 View Figure 14 ; Calder 1970, p 1509, Plate 2 Figures 2 View Figure 2 , 3 View Figure 3 .

Halecium boreale Lorenz 1886, p 26   , Plate 1 Figures 1 View Figure 1 , 2 View Figure 2 .

Halecium halecinum   : in part Broch 1910, p 144, Figure 4 View Figure 4 I–VIII (not others).

Halecium beringi Naumov 1960, p 449   , Figures 337, 338; Naumov 1969, p 484, Figures 337, 338; Antsulevich 1987, p 107.

Halecium beanii: Naumov 1969, p 483   , Figure 336; in part Schuchert 2001, p 73, Figure 59A–D.

[not Halecium beanii ( Johnston 1838)   .]

Material examined

MHNG INVE 28450, Greenland, Holsteinsborg , 66.93 ° N, 53.68 ° W, 165 m, 8 July 1971 GoogleMaps   , with female gonothecae. MHNG INVE 28731, Greenland, Augpilagtoq , 60.14 ° N, 44.31 ° W, 50–60 m, 30 July 1970 GoogleMaps   , on rock, with male gonothecae. MHNG INVE 33550   , BIOFAR station 111, The Faroes , 62.11 ° N, 6.5 ° W, 50 m, 25 July 1987 GoogleMaps   . BIOFAR collection station 556, The Faroes , 61.97 ° N, 6.54 ° W, 41 m, 22 September 1989 GoogleMaps   , on barnacles. BIOFAR collection station 699, The Faroes , 62.12 ° N, 6.83 ° W, 72 m, 10 May 1990 GoogleMaps   , on Tubularia   indiυisa, with gonothecae. BIOICE collection, Iceland, 65.78 ° N, 14.22 ° W, 28–60 m, 24 July 1991 GoogleMaps   . BIOFAR station 459, The Faroes , 63.00 ° N, 6.96 ° W, 910 m, 4 June 1989 GoogleMaps   .

Description

Colonies erect, up to 10 cm (reportedly up to 30 cm), imperfectly pinnate to shrubby, some colonies perfectly planar. Stem sometimes covered by bark-like overgrowth of anastomosed stolons. Main stem and branches polysiphonic, thinning out to monosiphonic ends. Internodes roughly equal in length; nodes oblique, sometimes indistinct. Hydrotheca sitting at the end of segment like a prolongation of it, not or only slightly inclined, slightly overtopping distal node of segment. Hydrotheca very shallow, walls straight, diameter at base 0.18–0.25 mm, depth 20–40 mm, with desmocytes, without pseudodiaphragms, rim of hydrotheca often damaged. Secondary hydrothecae on short hydrophore, the latter usually shorter than 1.5 times the diameter. Male gonotheca club- to oblong sac-shaped, 1.4 mm long. Female gonotheca club-shaped, up to 2 mm long and 0.8 mm broad, straight, somewhat flattened, distal end rounded, opening at side at approximately middle of gonotheca on a distinct shoulder; opening partially covered by a characteristic hood-like process, two protruding polyps, 10– 20 eggs per gonotheca. Nematocysts: two types of capsules, type I (9–10)X(3.5–4) mm; type II (5.5–7)X(1.5–2.5) mm.

Distribution

Circumpolar in the Arctic Sea , in the North Atlantic south to Cape Farewell in Greenland, Iceland and Faroe Islands. Type locality: Clark (1877) gives several localities in Alaska   .

Remarks

The trophosome and male gonothecae of Halecium scutum   , H. halecinum   and H. beanii   can resemble each other closely and it is difficult to identify immature or male specimens. In contrast, their female gonothecae are quite distinct and allow a relatively secure identification (compare Figures 2D View Figure 2 , 4D View Figure 4 and 5G View Figure 5 ). The female gonotheca of H. scutum   has a characteristic lip or hood above the hydrothecae on its side wall ( Figure 2E View Figure 2 ). Unfortunately, the shape of the female gonotheca of H. scutum   can occasionally be so variable as to make it resemble that of H. halecinum   ( Broch 1918, Figure 14 View Figure 14 ). It is therefore not surprising that Broch (1910, as H. halecinum   forma gigantea) considered H. scutum   as an arctic form of H. halecinum   . Later, Broch (1918) revised his opinion and kept both species distinct. Calder (1970) likewise regarded H. scutum   as valid and distinct from H. halecinum   . Naumov (1969) synonymized H. scutum   and H. beanii   , a view later hesitatingly adopted by, for example, Cornelius (1975) and myself ( Schuchert 2001).

Examination of material from the Faroes and Greenland, however, convinced me that H. scutum   is clearly distinct from both H. beanii   and H. halecinum   . Although my material from the Faroes did not contain female gonothecae, there were many large infertile and male colonies that agreed well with female colonies from Greenland and with the description of Broch (1918).

Mature colonies of H. scutum   are larger and considerably more robust than those of H. halecinum   and especially H. beanii   (compare Figures 1 View Figure 1 A–C, 3A–C and 5A–C). The best character, to distinguish H. scutum   from H. halecinum   and H. beanii   , apart from the female gonothecae, is the relative shortness of the secondary hydrophores ( Figure 2 View Figure 2 A–C). These secondary hydrophores are maximally as long as 1.5 times their diameter, but normally much shorter. In H. halecinum   and H. beanii   , they are longer, the ratio of length to diameter being in the range of 2 and more (compare Figures 2 View Figure 2 A–C, 4A–C and 5D, F). Halecium scutum   also lacks the characteristic pinnate growth often found in H. halecinum   and its hydrophores are in line with the main axis of the internode. In H. halecinum   the hydrophores are inclined ( Figure 4A, B View Figure 4 ). In H. beanii   , the diameter of the hydrotheca is distinctly smaller (0.12–0.16 versus 0.18–0.25 mm), the hydrotheca is usually held oblique relative to the internode axis, and the size of the type I nematocyst capsule is larger.

In the material from the Faroe Islands, one large colony of H. scutum   was overgrown with several other hydroids, among them were female and male shoots identified as H. beanii   . The differences in the microscopic structure were quite evident. This syntopic occurrence is further evidence for them being separate species. For further details see below under H. beanii   .

Another peculiarity of most large colonies of H. scutum   is a bark-like covering of the stem by a layer of tightly anastomosed stolons. A similar, but less anastomosed formation may occur in some larger colonies of H. halecinum   .

Another European species that can be confused with the species discussed above is Halecium sessile Norman, 1867   . According to Cornelius (1995), this species has very short secondary hydrothecae without distinct hydrophores. This trait may allow a reliable distinction.

Halecium boreale Lorenz, 1886   is likely a synonym of H. scutum   . Lorenz (1886) described H. boreale   as devoid of female gonothecae and the eggs are reported to develop in the gastric cavity of the feeding zooids (sic!). The males have normal gonothecae. Lorenz depicts a male colony that is indistinguishable from H. scutum   . The feeding zooid of this colony contains spherical bodies. It seems to me that Lorenz misinterpreted food items, perhaps even eggs of another animal, as the eggs of his Halecium boreale   . Although it is thinkable that there exist Halecium   species without gonothecae, I am not aware of any other such species. Moreover, the presence of normal male gonothecae and the position of the eggs within the gastric cavity make Lorenz’s assertion improbable.

Halecium beringi Naumov, 1960   was synonymized with H. scutum   by Antsulevich (1987).

Clark’s publication with the original description of H. scutum   was apparently published in 1877 and not 1876 ( Cornelius 1982, p 129).

MHNG

Museum d'Histoire Naturelle

Kingdom

Animalia

Phylum

Cnidaria

Class

Hydrozoa

Order

Leptothecata

Family

Haleciidae

Genus

Halecium

Loc

Halecium scutum Clark, 1877

Schuchert, Peter 2005
2005
Loc

Halecium beanii

: Naumov 1969: 483
1969
Loc

Halecium beringi

Naumov 1960: 449
1960
Loc

Halecium beringi

Naumov 1960
1960
Loc

Halecium boreale

Lorenz 1886: 26
1886
Loc

Halecium boreale

Lorenz 1886
1886
Loc

H. boreale

Lorenz 1886
1886
Loc

Halecium boreale

Lorenz 1886
1886
Loc

H. scutum

Clark 1877
1877
Loc

H. scutum

Clark 1877
1877
Loc

H. scutum

Clark 1877
1877
Loc

H. scutum

Clark 1877
1877
Loc

Halecium

Oken 1815
1815