Filellum conopeum Watson 2003

Filellum conopeum Watson, 2003

Filellum conopeum Watson, 2003: 159 –160, figs. 9a–c.

Type series. Holotype— Filellum conopeum Watson, 2003, malinol-mounted microslide, sparse fertile colony on stem of Acryptolaria patagonica (NMV F91342) (Watson 2003: 159).

Type locality. From the holotype, off Macquarie Island (53˚55.8´S–53˚55.7´S; 159˚5.5´E–159˚4.7´E), 453 m, (Watson 2003).

Description. See Watson (2003: 159–160).

Distribution. Filellum conopeum is known only from its original description, off Macquarie Island (53˚55.8´– 53˚55.7´S; 159˚5.5´–159˚4.7´E) (Watson 2003).

Remarks. Filellum conopeum was described by Watson (2003: 159) as bearing “Hydrothecae stolonal […]. Proximal quarter to one third of hydrotheca adnate to stolon, dorsal abcauline wall furrowed by many close, sharpedged 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”. Trophosome features of F. conopeum are found in other species of the genus, such as F. serratum, F. a n t a rc t i c u m or F. magnificum, so they alone do not allow a proper identification of the species, although F. mangnificum differs from Watson’s species by the distinctly larger hydrothecae, particularly in relation to the diameter of the hydrothecal aperture.

As with other species of the genus, truly diagnostic characters of F. conopeum are based on features of the coppiniae: “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.” (Watson 2003: 160). The general structure of the coppinia of this species resembles that of F. a n t a rc t i c u m and F. magnificum, in which the defensive tubes are situated on the periphery of the mass of gonothecae, like a fence, arching over the gonothecae (in F. magnificum the defensive tubes also arise among the gonothecae). They are different, however, because the gonothecae lack a distal neck in F. antarcticum, and have a short, clearly differentiated distal neck with an everted rim in F. magnificum. In Watson’s species, however, the “body expanding a little from base to shoulder then narrowing into a short straight or slightly curved neck tapering to a circular aperture”. Although Watson did not give measurements of the gonothecal neck, this seems distinctly longer in general and variable in shape. The cnidome of F. conopeum is unknown and, therefore, no comparison concerning this character can be made.