Filellum conopeum, Watson, 2003

Watson, Jeanette W., 2003, Deep-water hydroids (Hydrozoa: Leptolida) from Macquarie Island, Memoirs of Museum Victoria 60 (2), pp. 151-180 : 159-160

Filellum conopeum sp. nov.

Figures 9A–C

Filellum sp. — Watson and Vervoort, 2001: 161, figs 6a, b.

Material examined. Stn 94, NMV F91342 , holotype, malinol-mounted microslide, sparse fertile colony on stem of Acryptolaria patagonica .

Description (of holotype). Hydrothecae stolonal, arising from a tunnel-shaped stolon with flattened base, wall rugose, perisarc thin. Proximal quarter to one third of hydrotheca adnate to stolon, dorsal abcauline wall furrowed by many close, sharp-edged ridges with minute ragged frill of perisarc; ridges fading on adnate wall. Adnate wall becoming free at a sharp upward bend, free part cylindrical or weakly expanding from bend to margin, free part straight to broadly curved, walls smooth, occasionally with several regenerations. Margin circular, transverse, with smooth, distinctly everted rim. Perisarc of walls fairly thick, thinning distally. Hydranth with c. 12 tentacles and clavate hypostome.

Coppinia bud-shaped, c. 1 mm wide and 1 mm high, comprising many tightly packed gonothecae enclosed within a cone of protective nematophorous tubules. Gonotheca flask-shaped (lateral view), base rounded, body expanding a little from base to shoulder then narrowing into a short straight or slightly curved neck tapering to a circular aperture; in transverse view gonothecae polygonal. Nematophorous tubules similar in length, not forked, conjoined just above gonothecae then becoming free, most narrowing distally and inwardly curved to meet above gonotheca; terminal orifice circular. Perisarc of gonothecae and tubes moderately thick; perisarc of tubes somewhat roughened. Planulae enclosed in gonothecae small, spherical.

Colour. Colonies colourless, planulae creamy pink.

Measurements (µm)

Hydrorhiza width 40 Hydrotheca dorsal length of adnate part 180–240

depth of adnate part 92–116

length of free part 320–420

width of free part at bend 88–128

diameter at margin 140–168 Coppinia diameter of nematophorous tubules 64–120

length of gonotheca 320–440

maximum width of gonotheca 128–160

diameter of orifice 64–80

diameter of planula 80–120

Etymology. Named for the cone of tubes protecting the gonothecae.

Remarks. Epizoic colonies of Filellum conopeum occur sparsely on the stem of Acryptolaria . The thin ragged perisarcal frill surmounting the abcauline ridges of the hydrotheca, together with the bud-shaped coppinia are characteristic.

The trophosome of F. conopeum resembles that of F. serratum , however, the coppinia of that species as described and figured by Peña Cantero et al. (1998) is quite different, the gonothecae being protected by a canopy of apically divided tubes, some of which originate from within the gonothecal mass. Watson and Vervoort (2001) reported a species of Filellum from the deep-water seamounts south-east of Tasmania, Australia, but as their material was infertile and dimensions somewhat greater than those of F. serratum ( Clarke, 1879) (the only other known species with a wrinkled abcauline wall), they hesitated to identify it with that species. While the hydrothecae of F. conopeum are somewhat smaller than those of the Tasmanian specimens I consider the two are conspecific.

Figures

Figures 9A–C. Filellum conopeum sp. nov., stn 94. A, hydrotheca with ridged and frilled basal perisarc. B, lateral section through coppinia showing gonothecae and protective tubes. C, transverse section through coppinia. Scale bar: A, 0.2 mm; B, 0.5 mm.