Halecium mediterraneum Weismann, 1883

Schuchert, Peter, 2005, Taxonomic revision and systematic notes on some Halecium species (Cnidaria, Hydrozoa), Journal of Natural History 39 (8), pp. 607-639: 626-629

publication ID

http://doi.org/ 10.1080/00222930400001319

persistent identifier

http://treatment.plazi.org/id/4B6087F1-8B5E-FFDC-CB3D-FF6DFE06FCF8

treatment provided by

Carolina

scientific name

Halecium mediterraneum Weismann, 1883
status

 

Halecium mediterraneum Weismann, 1883  

( Figure 11 View Figure 11 )

Halecium tenellum   υar. mediteranea Weismann 1883, p 160, Plate 2 Figures 5 View Figure 5 , 6 View Figure 6 .

Halecium gracile: Motz-Kossowska 1911, p 335   , Figures 7 View Figure 7 , 8.1 View Figure 8 , Plate 18 Figure 2 View Figure 2 ; Neppi 1921, p 12, Figure 10 View Figure 10 , Plate 1 Figure 10 View Figure 10 .

Halecium flexile: Müller 1914, p 288   , Figures 1–3 View Figure 1 View Figure 2 View Figure 3 , Plate 10 Figures 1–7 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 .

Halecium mediterraneum: Stechow 1919, p 34   ; Gili and Garcia Rubies 1985, p 41, Figure 2K View Figure 2 .

Halecium tenellum: García Corrales et al. 1978, p 9   , Figures 1 View Figure 1 , 2 View Figure 2 .

[Not Halecium tenellum Hincks 1861   .]

Halecium delicatulum: Patriti 1970, p 23   , Figure 20; Ramil Blanco and Iglesias Diaz 1988, p 72, Figure 2 View Figure 2 ; Ramil and Vervoort 1992, p 82, Figure 20a–c. A; Medel and Vervoort 2000, p 12, bibliography; Peña Cantero and García Carrascosa 2002, p 63, Figure 12a, b View Figure 12 .

Material examined

MHNG INVE 26664, Anse de Troc , Banyuls-sur-Mer, France, Mediterranean, coll. P. Schuchert, 12 July 1999   , fertile female colony. MHNG INVE 26666, under raft, beach of Banyuls-sur-Mer , coll. P. Schuchert, 4 September 1996   , fertile male colony. MHNG INVE 31115, Anse de Troc , Banyuls-sur-Mer, coll. P. Schuchert, 23 June 1997   , infertile. MHNG INVE 32955, between Laboratoire Arago and Anse de Troc, Banyuls-sur-Mer, coll. P. Schuchert, 11 May 2002   , male and female colonies, mass occurrence, examined alive. MHNG INVE 34233, Santa Lucia, Naples , Italy, 1 m, coll. 14 April 1911   , fertile male. MHNG INVE 34232, Nisida , Naples, Italy, 1 m, 28 February 1902   , fertile male. MHNG INVE 34230, Nisida , Naples, Italy, 1 m, 14 February 1911   , fertile female. MHNG INVE 34229, Nisida , Naples, Italy, 1 m, 7 April 1911   , fertile female. MHNG INVE 34437, Calanque du Port d’Alon, Bandol , France, Mediterranean, 24 April 2003, 1 m.  

Description

Colonies growing on rock, algae and hydroids, occasionally mass occurrence covering areas of square metres forming a lawn or tangled mass of stems. Stolons tubular, creeping, ramified. Individual shoots 1–3 cm in height, irregularly branched, usually monosiphonic, occasionally weakly polysiphonic, bushy, limp when out of the water, distal parts often geniculate, with regular succession of alternately inclined nodes, nodes distinct. Each internode with a distal hydrophore, oblique, alternately pointing left or right, long and distinctly surpassing level of distal node, hydrophore not delimited by a node. Length of internode 0.4–0.6 mm (mode 0.5 mm), diameter 0.10–0.14 mm, internode length quite homogeneous. Perisarc of internodes smooth, near nodes somewhat bulging, relatively thin. Primary hydrotheca gradually widening and rim somewhat everted or rolled, diameter at base 70–125 mm (mode 80 mm), depth 20–40 mm (mode 30 mm), ring of desmocytes present. Sometimes below diaphragm a semicircular thickening on adcauline side (pseudodiaphragm). Secondary or higher hydrothecae often present, length of their hydrophores as in primary one or longer, often corrugated. Ramification of stems originate from primary hydrophores or from below them; branching usually dichotomous, occasionally trichotomous. Hydranth with 18–20 tentacles. Gonothecae arise in upper axils of branching points and hydrophores; gonothecae dimorphic, the two sexes on separate shoots. Gonothecae of both sexes without protruding hydranths. Female gonothecae smooth, ovoid to rectangular, length 0.7–0.8 mm, breadth 0.5 mm, always compressed but degree variable, along sides a crease-line, distal end obtuse, with or without curved notchlike opening of variable breadth and depth ( Figure 11L, M View Figure 11 ), without distinct lateral ears. Mature female gonothecae have a thin perisarc capsule on inside ( Figure 11L View Figure 11 ). This secondary capsule envelops the gonangium, towards the opening its wall gets thicker. Gonangium oblong, surface epidermis with numerous nematocysts, without hydranth, 6– 13 eggs embedded in tissue of ovoid shape, egg diameter about 0.1 mm. Development to planula takes place within gonotheca (larviparity). Male gonothecae smaller, ovoid, length up to 0.7 mm, compressed, sides with crease, distal end rounded, without notch or inner secondary capsule, opening slit-like. One oblong sperm mass. Living colonies have a characteristic yellow-brown colour; the pigment is extracted in formalin fixative.

Biology

Mature colonies were observed from April to November ( Motz-Kossowska 1911; Peña Cantero and García Carrascosa 2002; own observations). Depth range 0.5–145 m ( Peña Cantero and García Carrascosa 2002).

Distribution

Mediterranean, perhaps also adjacent Atlantic Ocean from Morocco to Galicia. Type locality: Naples, Italy, Mediterranean.

Remarks

Upon closer examination of mature female gonothecae, I noted that there is a delicate tubelike inner capsule enveloping the gonangium. This secondary capsule attaches to the outer capsule along its distal opening ( Figure 11L View Figure 11 ). Such a secondary capsule was also found in H. delicatulum   and in H. labrosum   , although in the latter it is very thin and difficult to see. Ralph (1958) also found this inner capsule in H. delicatulum   .

Halecium mediterraneum   is almost indistinguishable from Halecium delicatulum   . Halecium delicatulum   was first described by Coughtrey (1876) based on colonies found in Dunedin Harbour, New Zealand. Ralph (1958) re-described and revised it and she synonymized several similar nominal species. She also suspected that Halecium mediterraneum   might be conspecific with it. Rees and Vervoort (1987) agreed and formally synonymized both names. Subsequent studies dealing with Mediterranean collections (e.g. Ramil and Vervoort 1992; Peña Cantero and García Carrascosa 2002) continued this usage. Vervoort and Watson (2003), however, did not synonymize it.

Halecium mediterraneum   was initially described by Weismann (1883) as a variant of H. tenellum Hincks, 1861   . Because it is clearly distinct from H. tenellum, Stechow (1919)   raised it to full species level.

Comparison of H. mediterraneum   from the Mediterranean and H. delicatulum   from New Zealand showed that at least the microscopic structure of their trophosomes is very similar. There were differences in the shape of the female gonotheca (compare Figures 11 View Figure 11 and 12 View Figure 12 ). Ralph (1958) documented the variability of female gonothecae and her figures also show shapes as found here in H. mediterraneum   . Therefore, the differences apparent in Figures 11 View Figure 11 and 12 View Figure 12 are perhaps not really representative. There remain only some slight differences in egg numbers per gonotheca, colony colour and colony form. Because of the slight differences, and mainly for biogeographic reasons, both nominal species are here kept separate, although it is acknowledged that they are very similar. Genetic methods might hopefully clarify whether they really belong to the same biological species.

Among the European Halecium   species, H. mediterraneum   is uncomfortably intermediate between Halecium labrosum   and H. tenellum   and it is not always easy to draw a dividing line. This may have led García Corrales et al. (1978) to synonymize H. tenellum   and H. delicatulum   . This proposal has been rejected already by other authors (e.g. Ramil and Vervort 1992) and also the present author agrees that they are distinct. Halecium tenellum   is more gracile and forms smaller colonies, it is sparingly branched only, the internodes appear more elongate, and it never forms polysiphonic colonies. Fertile Halecium labrosum   , in contradistinction, are always polysiphonic, their gonothecae are about twice as large and their shape differs slightly (compare Figures 10E, F View Figure 10 and 11 View Figure 11 E–G). Halecium labrosum   often also has a characteristically undulated perisarc ( Cornelius 1995), but this is not a diagnostic feature as the perisarc can be entirely smooth. These differences are valid for European populations only. Halecium mediterraneum   may occasionally have been misidentified as H. labrosum   . Colonies growing epizoically on dead stems of Eudendrium   sp. can feign a strong polysiphonic stem and are prone to be confounded.

Another species within this species cluster is Halecium textum Kramp, 1911   (see below). The main trait to distinguish H. textum   from H. mediterraneum   is its undulated or corrugated perisarc. There are also differences in its branching pattern (frequent trifid branching) and the more pointed gonothecae. The distributions are disjunct. Halecium textum   is an arctic or northern boreal species. Although I am convinced that they are good species, the diagnosis of the limits of all four species remains difficult due to the absence of clearly apomorphic characters.

MHNG

Museum d'Histoire Naturelle

Kingdom

Animalia

Phylum

Cnidaria

Class

Hydrozoa

Order

Leptothecata

Family

Haleciidae

Genus

Halecium

Loc

Halecium mediterraneum Weismann, 1883

Schuchert, Peter 2005
2005
Loc

Halecium tenellum: García Corrales et al. 1978 , p 9

Garcia Corrales 1978: 9
1978
Loc

Halecium delicatulum

: Patriti 1970: 23
1970
Loc

Halecium delicatulum

: Patriti 1970
1970
Loc

Halecium delicatulum

: Patriti 1970
1970
Loc

H. delicatulum

: Patriti 1970
1970
Loc

Halecium mediterraneum:

Stechow 1919: 34
1919
Loc

H. tenellum

, Stechow 1919
1919
Loc

Halecium flexile: Müller 1914 , p 288

Muller 1914: 288
1914
Loc

Halecium gracile:

Motz-Kossowska 1911: 335
1911
Loc

Halecium mediterraneum

Weismann 1883
1883
Loc

Halecium mediterraneum

Weismann 1883
1883
Loc

Halecium mediterraneum

Weismann 1883
1883
Loc

H. mediterraneum

Weismann 1883
1883
Loc

H. mediterraneum

Weismann 1883
1883
Loc

Halecium tenellum

Hincks 1861
1861
Loc

H. tenellum

Hincks 1861
1861