Filellum adnatum Fraser 1925

Filellum adnatum (Fraser, 1925)

Figures 5 A–C

Lafoea adnata Fraser, 1925: 170 –171, figs. 5a–b.

Type series. Lectotype— Lafoea adnata Fraser, 1925 (BCPM 976-324-1).

Type locality. From the lectotype, United States Bureau of Fisheries Steamer “Albatross”, “near Farallon Islands [California], in 33–35 fathoms [59–63 m], on algae, bryozoa, and other hydroids” (Fraser 1925: 171).

Material examined. Lectotype BCPM 976-324-1.

Description of lectotype. Colony stolonal growing on algae, with filiform creeping hydrorhiza, 0.08–0.1 mm wide; hydrorhizal tubes and hydrothecae reticulated, with anastomosed perisarc, forming a more or less tight mesh. Hydrothecae sessile, arising with no definite pattern from hydrorhiza, varying in form, from almost completely adnate to substratum (either parallel to or over hydrorhizal stolon) to provided with a short free part. Perisarc tubes between hydrothecae and hydrorhiza thinner than hydrothecae themselves. Adnate portion of hydrothecae tubular or maximally slightly flattened, 0.24–0.46 mm (0.34 ±0.07, n=10) long, slightly constricted at base, perisarc with numerous striae on upper part up to hydrothecal curvature; free part cylindrical, arising at angles larger than 60o, mostly 90o, smooth, 0.2–0.32 mm (0.25 ±0.05, n=10) long; perisarc moderately thin; hydrothecae widening distally, margin even and smooth, with up to three renovations; hydrothecal orifice circular, 0.16–0.2 mm (0.19 ±0.01, n=10) wide, perpendicular to long axis of free part of hydrotheca. Hydranths badly preserved, with ca. 8–10 tentacles, hypostome conical. Hydranths, when retracted, lying at adnate space of hydrothecae. Coppinia absent. Nematocysts of one category (heterotrichous microbasic?mastigophores), but of two size classes (not seen discharged): 6.0–7.0 X 2.5–3.0 μm (6.45 ±0.50 X 2.76 ±0.5, n=10), rice-shaped and common, and 22.0–25.0 X 8.0–10.0 μm (23.50 ±1.12 X 8.80 ±0.76, n=5), ovoid and rare.

Distribution. Filellum adnatum was recorded only for the Farallon Islands (California) by Fraser (1925).

Remarks. Fraser (1925: 170–171) described Lafoea adnata as a new species with hydrotheca “attached to a reticulate stolon, with no definite pedicels, although there is a definite constriction at the base of each; in nearly all cases the wall of the hydrotheca is attached to the stolon for a part of its length but the proportion varies very materially”. However, the specimen described by Fraser (1925) does not refer to Lafoea, a genus with “colonies occasionally stolonial but usually erect, branched, with a polysiphonic hydrocaulus. Hydrothecae pedicellate, usually free from stem or stolon” (Calder 1991: 36). The specimen designated as lectotype of Lafoea adnata Fraser 1925 is stolonal with sessile hydrothecae and, therefore, should be assigned to the genus Filellum.

Although not remarked on by Fraser (1925), the material described by him is striated on the adnate part of the hydrotheca, a characteristic also observed in F. antarcticum, F. magnificum, F. nitidum and F. serratum. Inasmuch as the material lacks coppiniae, its identification is uncertain and, therefore, the taxon is here considered as species inquirenda.