Published December 31, 2008 | Version v1
Taxonomic treatment Open

Halecium elegantulum Watson 2008, sp. nov.

Description

Halecium elegantulum sp. nov.

Figure 6A-C

Holotype NMV F147463, Station 103, two microslides displaying several infertile stems. Paratypes NMV F147464, Station 103, two microslides displaying stems. NMV F147476, Station 103, one microslide displaying a small colony. All material probably from same colony on sertulariid hydroid.

Diagnosis. Stems arising from a creeping hydrorhiza; stolons tubular, smooth to crumpled. Hydrocaulus minute, variable in length, simple, unbranched, walls cylindrical, narrow, smooth, without nodes but with occasional shallow constrictions marking zones of regrowth after breakage. Hydrocaulus with either a single terminal hydrothecaor a linear series of up to six hydrophores each arising from diaphragm of preceding hydrotheca; base of hydophore swollen above supporting diaphragm.

Hydrotheca moderately deep, trumpet-shaped, expanding strongly from diaphragm to margin; rim circular, weakly outrolled; no replication of margin. Diaphragm delicate, transverse to concave, no desmocytes visible.

Perisarc thickest in proximal stem region, thinning distally; very thin on hydrotheca.

Gonotheca absent.

Measurements (μm) Remarks. As there are few clearly visible diaphragms and concave pseudo-diaphragms are visible in some hydrothecae. In most instances the depth from rim to diaphragm has been estimated as the distance from the base of secondary hydrophores to the rim of the supporting hydrotheca.

The few remaining hydranths are too decomposed for description but seem to have been very long and extensile. No desmocytes were seen but the interior of most hydrothecae is obscured by adventitious matter.

Two small, closely related species were considered: Halecium tenellum Hincks, 1861 and Halecium fragile Hodgson, 1950. Although most measurements of Halecium elegantulum fall within the range given by Cornelius (1995) for H. tenellum from the North Atlantic and by Watson (2003) for H. tenellum from the subantarctic, both of these species are branched whereas all material of H. elegantulum is unbranched showing no evidence of branching. Furthermore, the hydrotheca of H. elegantulum is elongated, not shallow as in H. fragile.

Etymology. The name refers to the elegantly simple hydrocaulus.

Notes

Published as part of Watson, Jeanette E., 2008, Hydroids of the BANZARE expeditions, 1929 – 1931: the family Haleciidae (Hydrozoa, Leptothecata) from the Australian Antarctic Territory, pp. 165-178 in Memoirs of Museum Victoria 65 on pages 170-171, DOI: 10.24199/j.mmv.2008.65.9, http://zenodo.org/record/4630462

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Linked records

Additional details

Biodiversity

Collection code
NMV
Family
Haleciidae
Genus
Halecium
Kingdom
Animalia
Order
Leptothecata
Phylum
Cnidaria
Scientific name authorship
Watson
Species
elegantulum
Taxonomic status
sp. nov.
Taxon rank
species
Type status
holotype , paratype
Taxonomic concept label
Halecium elegantulum Watson, 2008

References

  • Watson, J. E. 2003. Deep-water hydroids (Hydrozoa: Leptolida) from Macquarie Island. Memoirs of Museum Victoria 60: 151 - 180.