Halecium corrugatissimum Trebilcock, 1928

Schuchert, Peter, 2005, Taxonomic revision and systematic notes on some Halecium species (Cnidaria, Hydrozoa), Journal of Natural History 39 (8), pp. 607-639 : 634-636

Halecium corrugatissimum Trebilcock, 1928

( Figure 15 ) Halecium corrugatissimum Trebilcock 1928, p 7 , Plate 3 Figure 1 ; Ralph 1958, p 329,

Figure 9 c–f. Not Halecium corrugatissimum: Patriti 1970, p 25 , Figure 24 [5 H. pusillum (M. Sars 1857) ].

Material examined

MHNG INVE 26670 , New Zealand, Wellington, coll. P. Schuchert, 1 November 1993, several male and female colonies . MHNG INVE 29460 , New Zealand, Devonport, Cheltenham Beach, coll. P. Schuchert, 27 July 1991, on seaweeds, fertile male .

Description

Stems small, up to 5 mm high, arising from creeping, ramified stolons. Stems unbranched or sparingly branched, usually less than 10 hydranths per stem, monosiphonic, nodes irregular. Perisarc with strong, regular annulation or irregular corrugation. Hydrotheca sitting at the end of segment like a prolongation of its axis, not or only slightly inclined, wall straight and not everted, a small part near the rim can be recurved, desmocytes present. Diameter of hydrotheca base 0.12–0.13 mm, depth 30–50 mm. Side-branches originate immediately below hydrothecae, curved steeply upwards. Gonothecae on stems and sometimes stolons, dimorphic, the two sexes on separate stems. Female gonothecae ellipsoid, straight, length 0.7–0.85 mm, diameter 0.35 mm, strongly sculptured by up to 10 transverse ridges, chimney-like opening in middle on side, short, formed by two fused tubes, with median separation line, two hydranths protrude from this aperture, four to five eggs that develop in situ. Male gonothecae, without lateral opening, straight, spindleshaped, smaller than female, 0.6 mm long and 0.25 mm diameter, less corrugated than female gonotheca, variable within the same colony. Vegetative propagules unknown.

Distribution

New Zealand, North and South Island. Type locality: St Clair, Dunedin , New Zealand.

Remarks

The male gonothecae of this species have not been described so far. As for many other Halecium species, their morphology differs from the female ones.

Patriti (1970) identified closely similar colonies from Morocco as H. corrugatissimum . The hydrothecae of her material were clearly everted and therefore her material was more likely Halecium pusillum (M. Sars, 1857) , a well-known Mediterranean species. Halecium pusillum is very similar to H. corrugatissimum , but usually has everted hydrothecae (see Broch 1912 for re-description of the type material; Babić 1913 for figures of gonothecae). Motz-Kossowska (1911) attributed similar, but infertile, colonies to H. pusillum , despite the hydrothecae having straight walls. Stechow (1919) therefore considered this material to belong to a separate species which he named Halecium annulatum . Because this name was preoccupied by H. annulatum Torrey, 1902 , Leloup (1938) changed it to Halecium stechoaei . Peña Cantero and García Carrascosa (2002) also attributed the records of Motz- Kossowska (1911), hence H. stechoaei , to H. pusillum . The presence of the characteristic vegetative propagules in the material of Motz-Kossowska (1911) makes this quite reasonable, but allowing also straight hydrothecae for H. pusillum narrows uncomfortably the gap to H. corrugatissimum .

Another nominal species in this complex is Halecium speciosum Nutting, 1901 , a species originally described from Alaska (see also Fraser 1937). Considering their climatic and geographic separation, it appears unlikely to me that H. corrugatissimum , H. pusillum and H. speciosum belong to the same biological species.

These three nominal species are likely another example of the limitations we must be aware of when we attempt to discriminate biological species by morphological characters.

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 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 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).