Filellum adhaerens Nutting 1901

Filellum adhaerens (Nutting, 1901)

(Figures 1 A–E)

Lafoea adhaerens Nutting, 1901: 178, pl. 21, figs. 3–4. Filellum adherens: Peña Cantero et al. 1998: 299 –230.

Type series. Neotype— Lafoea adhaerens Nutting, 1901, former University of California no. 5245 (Nutting 1901 and specimen’s label) (USNM 43728).

Type locality. From the neotype, Harriman Expedition 1899, Kodiak Harbor, Alaska, epibiotic on Abietinaria turgida (Clark, 1876). The data coincide with those of the original description.

Material examined. Neotype USNM 43728.

Description of neotype. Colony stolonal, growing on stem and branches of Abietinaria turgida (Clark, 1876), arising from a creeping filiform, though flattened, hydrorhiza, 0.07–0.08 mm wide; hydrorhizal tubes and hydrothecae covered by a thin sheath (possibly produced by the host), with anastomosed perisarc, forming a tight mesh with no free space left in some parts of the sertulariid substrate. Hydrothecae sessile, arising with no definite pattern from hydrorhiza, varying in form, from almost completely adnate to substratum (either parallel to or over the hydrorhizal stolon), to provided with a short free part (especially both where substrate ends and where hydrothecae ascend one another). Hydrothecae irregularly curved in diverse patterns, in varied degrees to horizontal plane, rarely emerging from substrate plane. Perisarc tube connecting hydrothecae and hydrorhiza thinner than hydrothecae themselves. Adnate portion of hydrothecae tubular or maximally slightly flattened, 0.32–0.53 mm (0.41 ±0.08, n=10) long, perisarc smooth; free part cylindrical, smooth, 0.00– 0.19 mm (0.08 ±0.06, n=10) long; perisarc moderately thin; hydrothecae not widening distally, margin even and smooth, with up to 4 renovations, rarely slightly flaring; hydrothecal aperture circular, 0.12–0.14 mm (0.13 ±0.01, n=10) wide, perpendicular to axis of free part of hydrotheca. Hydranths not seen.

Gonothecae packed in coppinia up to 2 mm wide. Gonothecae closely set, contiguous, perimeters distinct in dorsal view, general form elongated flask-shaped. Gonothecae 0.47–0.70 mm (0.54 ±0.06, n=10) high (from substrate to distal plateau), with narrowest part adnate to substratum, distal part widening until forming a distal plateau varying from flattened to roof-shaped, plateau 0.14–0.24 mm (0.18 ±0.03, n=10) wide; apical part with distal short neck, 0.01–0.03 mm (0.02 ±0.01, n=10) high (from plateau to aperture), bearing circular aperture, 0.03–0.05 mm (0.04 ±0.01, n=10) wide, rim even, not flared, without renovations. Protective tubes present, curved, hollow, with distal aperture, arising amongst gonothecae; some protective tubes merge with each other. Planulae diameter larger than gonothecal aperture.

Nematocysts not seen.

Distribution. Filellum adhaerens was recorded only at the type locality, Kodiak Harbor, Alaska by Nutting (1901).

Remarks. There is a single specimen of the paratype of Filellum adhaerens (Nutting, 1901), originally Lafoea adhaerens Nutting, 1901, in the collection of the Smithsonian National Museum of Natural History (USNM 43728). This specimen has the same information as the original description on its label, which states: “ paratype undoubtedly type lost—has Nutting’s label”. Indeed, as far as we know, there is no other specimen of the type series and, therefore, we designate the material USNM 43728 as the neotype of Lafoea adhaerens Nutting, 1901.

Nutting (1901: 178), in the original description of Lafoea adhaerens, remarked that “this interesting species is so different in appearance from the others of the genus that I was at first inclined to make it the type of a new genus”. The author described the species as “forming an encrusting mass of adherent rootstocks disposed both longitudinally and transversely over colonies of other hydroids, the tubes of the rootstock interwoven much like the threads of a fabric. Hydrothecae sessile, tubular, often more or less curved, aperture facing upwards, entire; margin slightly expanded. The hydrothecae are very irregularly disposed, being much more crowded in some places than in others” (Nutting 1901: 174). Inconsistently with his assignment, he described Filellum as “stem a creeping, slender rootstock, parasitic on other hydroids, often forming a reticulate structure. Hydrothecae curved, decumbent, and partly adherent; margin entire, without operculum” (Nutting 1901: 179). Therefore, it was only a matter of time before the species was correctly assigned to Filellum (Stechow 1913b: 30; see also Peña Cantero et al. 1998: 299).

Filellum adhaerens is a species characterized by the structure of its coppinia, with the juxtaposed bottle-shaped gonothecae with a short distal neck and protective tubes amongst the gonothecae. Nutting (1901) considered the coppinia similar to that of Lafoea dumosa (Fleming, 1820) and described it as “being composed of closely packed gonangia interspersed with long, tubular, variously curved modified hydrothecae. The gonangia are flask-shaped, with a tubular neck and small aperture” (Nutting 1901: 178).