Filellum nitidum Watson 2005

Filellum nitidum Watson, 2005

Filellum nitidum Watson, 2005: 504 –505, figs. 3c–e.

Type series. Holotype— Filellum nitidum Watson, 2005, fertile colony on stem of Gymnangium sp. (NMV F 101650). Paratype— Filellum nitidum Watson, 2005, fertile colony on basal stems of additional colonies of Gymnangium sp. (WAM Z29955) (Watson 2005: 504).

Type locality. From the holotype, Australia, Middle Island, 25 m (Watson 2005: 504).

Description. See Watson (2005: 504).

Distribution. Filellum nitidum is only known from its original description, from Australia, Middle Island (Watson 2005).

Remarks. Filellum nitidum was described by Watson (2005: 504) as bearing “Hydrothecae sessile […] adnate part of base fairly short, free part long, perisarc of abcauline wall faintly wrinkled; perisarc of free wall rather thick, marginal rim slightly everted and thickened” and “hydrothecae with several regenerations along length”. Surprisingly, in spite of the original description and the figure 3C, where wrinkled hydrothecae are shown, Watson (2005: 505) also stated that the “absence of marked abcauline rugosity and absence of a distinctly everted rim” would make the trophosome of the species similar to that of F. antarcticum. This seems to be an inapt description, since F. antarcticum has distinctly marked striae on the upper side of the adnate portion of the hydrothecae (Peña Cantero et al. 2004b). On the other hand, as also remarked by Watson (2005), both species have clearly different gonothecae. Other morphological features listed by Watson (2005) do not distinguish this species from the others of the genus Filellum. Therefore, we believe that reliable diagnosis of F. nitidum must be based on coppiniae characters, described as “surface of coppinia a mosaic covered by a thin pellicle of tissue perforated by small openings flush with surface; hydrothecae protruding above surface together with large inverted funnel-shaped tubules, some tubules bifurcated, apices of others closed” and the sectional view of “numerous rather haphazardly arranged elongate gonothecae” (Watson 2005: 504–505). The figure illustrating the coppinia of this species (Watson 2005: 503, figs. 3D–E) shows protective tubes among the gonothecae; this, together with the different shape of the gonothecae, make the species distinct from F. magnificum, for which the defensive tubes are mainly situated on the periphery of the mass of gonothecae, like a fence, arching over the gonothecae. There is no information on the cnidome of the species, and no further comparison concerning this character can be made.