Filellum contortum Nutting 1905

Filellum contortum (Nutting, 1905)

(Figure 6 A–D)

Lafoea contorta Nutting, 1905: 945, pl. 3, fig. 6, pl. 9, figs. 8–9.

? Filellum contortum: Peña Cantero et al. 1998: 301.

Non Filellum contortum: Peña Cantero and Gili 2006: 766 [= Filellum bouvetensis sp. nov.].

Type series. Lectotype— Lafoea contorta Nutting, 1905; alcohol specimen on Aglaopheniidae (USNM 70715; specimen represented by Nutting 1905, pl. 3, fig. 6, pl. 9, figs. 8–9). Paralectotype— Lafoea contorta Nutting 1905; alcohol specimen (USNM 68984).

Type locality. From the lectotype, “Albatross R/V” Expedition, Hawaiian Explorations, Stn. 3949, north Pacific Ocean, Hawaii, north of Laysan Island, 27o47’45’’N; 171o52’35’’W, 108–238 m, 21 May 1902, leg. Albatross R/V. Paralectotype: “Albatross R/V” Expedition, Hawaiian Explorations, Stn. 4102, north Pacific Ocean, Hawaii, Pailolo Channel, between Maui and Molokai Islands, 21o03’10’’N; 156o45’20’’W, 223–241 m, 23 September 1902, leg. Albatross R/V.

Material examined. Lectotype USNM 70715 and paralectotype USNM 68984.

Description of lectotype. Colony stolonal, with a filiform and creeping hydrorhiza growing over some 7 mm at base of an aglaopheniid hydroid; hydrorhizal tubes 0.10–0.14 mm wide, with few anastomosed perisarc. Hydrothecae sessile, arising with no definite pattern from hydrorhiza, less than half of their total length partially adnate to substratum parallel to hydrorhizal stolon, free part emerging from substrate plane at angles wide than 60o, usually 90o.

Adnate portion of hydrothecae tubular or maximally slightly flattened, 0.41–0.73 mm (0.58 ±0.11, n=10) long, perisarc with many striae on abaxial hydrothecal surface of adnate part, striae extend up to curvature of hydrothecae; free part cylindrical, smooth, 0.84–1.40 mm (1.22 ±0.15, n=10) long; perisarc moderately thin; hydrothecae slightly widening distally, margin even and smooth, with up to two renovations, tenuous flaring; hydrothecal orifice circular, 0.21–0.27 mm (0.24±0.02, n=10) wide, perpendicular to axis of free part of hydrotheca. Hydranths badly preserved, with ca. 14 tentacles, hypostome conical. Hydranths, when retracted, lying at the adnate space of the hydrothecae. Gonothecae absent.

Nematocysts of one category, heterotrichous microbasic?mastigophores (not seen discharged), 5.0–6.0 X 2.0– 2.5 µm (5.60 ± 0.39 X 2.35 ± 0.24, n = 10), rice-shaped, common.

Distribution. Filellum contortum was recorded for the coast of Japan (Stechow 1913b).

Remarks. Filellum contortum was originally described as Lafoea contorta Nutting, 1905, and diagnosed as a “colony parasitic, growing from a twisted rootstock” with hydrothecae “sessile, tubular, very long, and often bent and twisted in various ways”. The specimens described by Nutting (1905: 945) were sterile.

This species is different from most of the species of Filellum in its morphometry (e.g., larger dimension of the free part of hydrotheca). The cnidome of F. contortum is also different, comprising a single type of nematocyst (heterotrichous microbasic mastigophore), comparatively smaller than those found in other species. Although these differences could characterize the species, they may be variable or dependent on the quality of specimen preservation. Besides, Nutting’s (1905) material lacks coppinia, so the crucial information concerning the reproductive structure, necessary to properly assign new material to this species, is unknown. The only coppiniae assigned to F. contortum was described by Peña Cantero and Gili (2006) from Bouvet Island, herein redescribed as Filellum bouvetensis sp. nov. Therefore, a reliable diagnosis of the species is difficult, and its validity remains dubious (Peña Cantero et al. 1998) until its reproductive parts are described. We consider F. contortum as a species inquirenda.