Filellum serratum

Filellum serratum (Clarke, 1879)

(fig. 10B–E, tables 9–10)

Lafoea serrata Clarke, 1879: 242, pl. 4 fig. 25; Hartlaub, 1905: 595, fig. Q 2.

Reticularia serrata: Ralph, 1958: 312, figs 2J, 3A.

Filellum serratum: Stechow, 1923: 145; Hargitt, 1924: 488; Fraser, 1944: 216, pl. 44 fig. 199; Vervoort, 1968: 100; 1972a: 51, fig. 14A–B; Leloup, 1974: 8, fig. 9; Millard, 1975: 178, fig. 59A–C; Blanco, 1976: 32, pl.2 figs 1–3; Millard, 1977: 12; Stepanjants, 1979: 50, pl. 8 fig. 8A–B; Hirohito, 1983: 20; Calder, 1991: 36, fig. 21; El Beshbeeshy, 1991: 78, fig. 18; Ramil & Vervoort, 1992: 354; Hirohito, 1995 (English text): 110, fig. 31A–C; Peña Cantero et al., 1998: 304, figs 1–2; Schuchert, 2001a: 63, fig. 50; Peña Cantero & García Carrascosa, 2002: 53; Calder et al., 2003: 1209; Vervoort & Watson, 2003: 59; Bouillon et al., 2004: 156, fig. 84I–J.

Filellum cf. serratum: Ramil & Vervoort, 1992: 54; Vervoort, 2006: 231.

Material examined. Stn. CHL 02 —04.iii.2005, 13– 20 m, S80: several sterile colonies, epizoic on Symplectoscyphus filiformis and polychaete tube. Stn. COM 06 —26.i.2006, 20– 23 m, S95: several sterile colonies, epizoic on Obelia dichotoma, Sertularella polyzonias and a piece of wood. Stn. COM 07 —25.xii. 2004, 22 m, S57: a small, sterile colony, epizoic on Plumularia setacea. Stn. COM 11 —11.ix. 2004, 26 m, S14: a sterile colony, epizoic on Sertularella polyzonias (MHNG INVE 53168). Stn. SWA — 15.iii.2006, S134 (20 m): a sterile colony, epizoic on Obelia dichotoma; S131 (25 m): a fertile colony, with 3 coppiniae, epizoic on Bougainvillia pyramidata, and some hydrothecae, without coppinia, epizoic on Modeeria rotunda. Stn. CCA — 12.iii. 2006, 28 m, S87: several sterile colonies epizoic on Obelia dichotoma, Campanularia agas, and Halecium delicatulum. Stn. CCO — 09.iii.2006, 0–20 m, S140: several sterile colonies, epizoic on Synthecium robustum. Stn. CPA — 09.iii. 2005, 15 m, S170: infertile colonies investing almost the entire surface of a colony of Symplectoscyphus subdichotomus. Stn. CPI — 07.iii. 2006, 18 m, S133: a sterile colony, epizoic on Symplectoscyphus magellanicus.

Type locality. Caribbean, near Havana, Cuba.

Description. Colonies stolonal with creeping, irregularly branched, adhering stolon. Hydrotheca sessile, cylindrical, with basal part adnate to substratum and free part curving upwards. Adnate part with variable number of transverse striae on outer surface. Hydrothecal aperture rounded, rim even, usually everted; renovations sometimes present. Gonothecae borne in coppiniae. Coppinia a basket-like structure composed of a central mass of tightly packed gonothecae, surrounded by a fence of defensive or accessory tubes. Gonothecae tubular, rounded to polygonal in transverse section, lateral walls fused, distal end truncated. Most gonothecae empty, others with badly preserved soft parts; no acrocysts have been seen. Accessory tubes disposed in two concentric rows. An external sheath is directly in contact with the exterior of coppinia; it is composed of tubes of irregular shape, up to 4 times longer than gonothecae; walls of adjacent tubes fused, with only the distal part, of variable length, free; lateral walls often undulated. Distal part of tubes curved above the central mass of corbula, forming a nest-like protective structure. An internal sheet of accessory tubes interposed between the mass of gonothecae and the external sheet; it is composed of much shorter tubes (but still longer than gonothecae), with straight walls, circular in transverse section, with distal extremity truncated.

Remarks. Hartlaub (1905) reported small, cup-shaped structures irregularly arising from the stolon, with smooth walls and everted rim, that were interpreted as possible nematothecae. However, similar structures were never mentioned by other authors and consequently they may represent anatomical parts belonging to another species.

Since no coppiniae were formed in the majority of the available samples of the present material, their identification is exclusively based on the presence of striae on the upper adnate part, the general shape and the similarities in the hydrothecal dimensions compared with those of the fertile material from sample S131. Comparison of measurements proved that all the hydrothecae are nearly identical in dimensions (Table 10), and most probably belong to the same species, F.serratum.

Peña Cantero et al. (1998) studied the coppiniae of F. serratum from Mediterranean material. The accessory tubes were branched and the gonothecae were bottle-shaped, with a short distal neck bearing the gonothecal aperture. Similar gonothecae were also figured by Hirohito (1995), who however provided no description. Conversely, Millard (1975) described the structure of coppinia from South African material. She found unbranched accessory tubes of irregular shape, usually curved or twisted, and at least double the length of the gonothecae. Moreover, the gonothecae lacked the distal neck.

The coppiniae in the present material agree better with the description and illustration provided by Millard (1975). However, the lack of gonothecal neck in both the Chilean and South African material may be interpreted as a possible mechanical breakage following egg release or by the fact that the coppiniae were too old and therefore deciduous.

Due to the differences cited above, Peña Cantero et al. (1998) supposed that F. serratum may be a complex of more than one species. Thus, F. serratum needs the examination of more fertile material from different geographic locations.

World distribution. F. serratum is considered a cosmopolitan species. However, since most of the records are based on sterile material, its actual distribution is only speculated (Peña Cantero et al. 1998).

Records from Chile. This species was previously reported from the Strait of Magellan (Hartlaub 1905) and Golfo de Ancud (Leloup 1974). The present material was collected between 42°10' S and 50°50' S.