Filellum Hincks 1868

Genus Filellum Hincks, 1868

Capsularia: Gray 1848: 151 (in part); Naumov 1960: 280; Naumov 1969: 303 [non Capsularia Cuvier, 1798: 665 = Coryne Gaertner, in Pallas, 1774; after Lamouroux et al. 1824: 224; Bedot 1901: 434, 437; Cornelius 1975: 378].

? Conchella Gray, 1848: 88 [discussion in Cornelius & Calder 1986: 338; Cornelius 1995: 253; Calder 1991: 35].

Coppinia Hassall, 1848: 2223 [discussion in Cornelius & Calder 1986: 335–337; Calder 1991: 35].

Reticularia Thomson, 1853: 443; Ralph 1958: 311; Rees and Thursfield 1965: 85 –88 (in part) [preoccupied by a name for a brachiopod described by McCoy, in Griffith 1844; after Vervoort 1972: 50; Cornelius 1975: 378; Calder 1991: 35 – Stechow 1923: 144 considered Reticularia as a mollusk].

Halia Hincks, 1855: 128 [preoccupied by a name for a gastropod described by Risso 1826; after Stechow 1923: 144 (quoting Scudder 1882, Nomenclator Zoologicus: 152); Calder 1991: 35; Cornelius 1995: 253].

Thalia L. Agassiz, 1862: 355 [incorrect subsequent spelling of Halia Hincks, 1855, after Bedot 1910: 308].

Filellum Hincks, 1868: 214; Nutting 1901: 179; 1905: 946; Stechow 1913b: 44; Stechow 1923: 137 (comparative table of lafoeid genera), 144–145; Naumov 1960: 280; Naumov 1969: 303; Vervoort 1972: 50; Cornelius 1975: 378; Millard 1975: 175; Cornelius and Calder 1986: 335 –339; Calder 1991: 35 –36; Cornelius 1995: 253; Hirohito 1995: 110; Peña Cantero et al. 1998: 298 –299; Vervoort and Watson 2003: 57.

Fillelum Billard, 1906: 166 [incorrect subsequent spelling].

Grammaria: Vervoort 1946: 194 (in part) cf. Hirohito 1995: 110 [not Grammaria Stimpson, 1854].

Corystolona Watson, 2002: 333 –334.

Type species. Campanularia serpens Hassall, 1848, by monotypy in Hincks (1868: 214).

Description. Lafoeidae with young and adult colonies stolonal; hydrorhiza filiform, branched, creeping on substratum. Hydrorhizal stolons giving rise directly to hydrothecae. Hydrothecae tubular, sessile; basal portion adherent to substratum, usually parallel to hydrorhizal stolon; distal free portion directed upwards at varying degrees and extension. Hydranth long, one distal whorl of filiform tentacles; hypostome short, dome-shaped. Hydrothecal diaphragm, hydrothecal operculum, nematothecae and nematophores absent. Gonophores as fixed sporosacs, in gonothecae forming coppiniae. Gonothecae either closely set, with lateral walls juxtaposed each other, or weakly aggregated, gonothecae being isolated. Coppinia with or without defensive tubes (modified hydrothecae). Cnidome consisting basically of heterotrichous microbasic mastigophores and/or microbasic euryteles.

Distribution. Based on literature, some species of Filellum are distributed worldwide, usually epibiotic on other hydroids (Cornelius & Calder 1986: 335; Cornelius 1995: 253).

Remarks. Several generic names were proposed prior to Filellum Hincks, 1868, but they were dismissed either by ICZN decision or because they were preoccupied (ICZN 1999, art. 60). The nomenclatural history of the group may be found in Stechow (1923: 144–145), Vervoort (1972: 50), Cornelius (1975: 378), Cornelius and Calder (1986: 335–341), Calder (1991: 35–36), and Peña Cantero et al. (1998: 299). A summary of the nomenclatural issues is given below.

Conchella Gray, 1848 and Coppinia Hassall, 1848 are two generic names used in specific combinations of taxa presently referred to the generic name Filellum. The identification of the type species of Conchella, Campanularia intertexta Couch, 1844, whose type specimen is not existent (see Couch, 1844: 41–42), is doubtful. The species may refer to Filellum serpens (Hassall, 1848), Lafoea dumosa (Fleming, 1820), Orthopyxis integra (Macgillivray, 1842), or even to all of them (Cornelius & Calder 1986: 338). The last of these three was excluded as type of C. intertexa by designation as lectotype of an illustration by Couch of a specimen having coppiniae (Cornelius 1982: 122). The generic name Conchella was never used subsequently (see Cornelius & Calder 1986). Conversely, the generic name Coppinia Hassall, 1848 was based on a lafoeid reproductive structure that had been confused as a distinct taxon, presently known in the literature as “coppinia”. The type species of the genus, Coppinia mirabilis Hassall, 1848, was eventually found to be the widely known species Filellum serpens (Hassall, 1848), as it is considered today. The generic name Coppinia, although rarely used during the 20th century, remained valid and threatened the more widely used name Filellum (Cornelius & Calder 1986: 335–336). A case was submitted to the ICZN requesting suppression, for the purposes of the Principle of Priority, of the obscure and infrequently used names Conchella Gray, 1848 and Coppinia Hassall, 1848. In Opinion 1485 (ICZN 1988), both names were placed on the Official Index of Rejected and Invalid Generic Names in Zoology.

Campanularia serpens Hassall, 1848 was transferred to the genus Reticularia Thomson, 1853 by Totton (1930: 160–161), based on its hypothesized conspecificity with the type species of the genus, Reticularia immersa Thomson, 1853. The generic name Reticularia has been used by a series of authors in combination with many specific names presently referred to Filellum, such as Reticularia annulata Watson, 1973 (Watson 1973: 164); Reticularia antarctica (Hartlaub, 1904) (Totton 1930: 160 –161; Briggs 1938: 26; Rees & Thursfield 1965: 85 –86; Watson 1973: 163 –164); Reticularia serpens (Hassall, 1848) (Hastings 1943: 394; Millard 1957: 203; Rees & Thursfield 1965: 87 –88); and Reticularia serrata (Clarke, 1879) (Ralph 1958: 312; Rees & Thursfield 1965: 86 –87). Hincks (1868) believed that the generic name Reticularia Thomson, 1853 was preoccupied by Reticularia Bulliard, 1791, a name applied to a fungus, and founded Filellum as a replacement for it. Bulliard’s usage of the name is excluded from, and does not become a homonym in, zoological nomenclature (Vervoort 1972: 49; Calder 1991: 35; see ICZN 1999, art. 1.4). However, the name is preoccupied by Reticularia McCoy, in Griffith 1844, a fossil brachiopod. As the oldest available and valid synonym of Reticularia Thomson, 1853, Filellum becomes the name of the genus.

The genus name Halia Hincks, 1855, and the binomen Halia praetenuis Hincks, 1855, were applied to what was originally thought to have been a bryozoan. The species was transferred to Hydrozoa by Hincks (1856), who held Halia to be a congener of Reticularia Thomson, 1853. In fact, the name Halia Hincks, 1855 is an invalid junior homonym of the gastropod genus Halia Risso, 1826 (see Calder 1991: 35). The generic name Thalia, as used by L. Agassiz (1862: 355), is a misspelling of Halia; as such it does not constitute a threat to Filellum.

Within the family Lafoeidae, Filellum was previously considered to be related to Grammaria, either as: (1) the subgenus of Grammaria (Filellum) (e.g., Broch 1913, 1928a, 1928b, 1933; Leloup 1933; Berezina 1948); (2) the genus Filellum (Grammaria) (e.g., Leloup 1935); or (3) directly as a junior synonym (e.g., Kramp 1913; Broch 1918; Mathisen 1928; Remane 1933; Leloup 1938, 1947; Vervoort 1942, 1946, 1959; da Cunha 1950; Arndt 1964; Fey 1970; Füller 1970; Castric-Fey 1973). Evidence against this relationship was given by Vervoort (1972: 50), and re-affirmed by Calder (1991: 35). Similarly, the genus Filellum has also incorrectly been considered as including the subgenus Lafoea, such as in the use of Filellum (Lafoea) adhaerens (Stechow 1913b: 30).

Filellum was considered a junior synonym of Capsularia Modeer, 1793 (Cornelius 1975: 378). The generic name was used by Naumov (1960: 280; 1969: 303), probably following Gray (1848: 151, as in the binomen Capsularia serpens). Capsularia Cuvier, 1798 was considered a synonym of Coryne Gaertner, in Pallas 1774 by Lamouroux et al. (1824: 220, 224), Bedot (1901: 437), Cornelius (1975: 378, who provided the historical account on the case), and Calder (1991: 35–36).

Although the genus Filellum is herein described as lacking nematothecae and nematophores, Calder (1991: 35) described the genus with “nematothecae usually absent”. As far as we know, based on all specimens of Filellum we have studied, there is no trace of nematothecae in the members of the genus.

As stated above, most authors have based their identifications and descriptions exclusively on characters of the trophosome. Nevertheless, the paramount taxonomical importance of the reproductive structures (coppiniae) is evident, as illustrated by F. disaggregatum and F. serpens (see Peña Cantero et al. 1998), species with indistinguishable trophosome, but easily recognized by their coppinia. As already stated, this fact makes unreliable all previous identifications of species of Filellum exclusively based on non-reproductive characters (Peña Cantero et al. 1998: 297).

The following species were described as belonging to, or subsequently referred to, the genus Filellum. Nevertheless, to our knowledge, only the species listed in bold belong to Filellum. The remaining species belong to other genera of Lafoeidae (Grammaria, Lafoea) or to other phyla.

Filellum adnatum (Fraser, 1925) species inquirenda (from Lafoea adnata Fraser, 1925)

Filellum adhaerens (Nutting, 1901) (from Lafoea adhaerens Nutting, 1901)

Filellum annulatum (Watson, 1973)

Filellum antarcticum (Hartlaub, 1904) (from Lafoea antarctica Hartlaub, 1904)

Filellum bouvieri Jullien, 1880 species inquirenda (from Filellum Bouvieri Jullien, 1880)

Filellum conopeum Watson, 2003

Filellum contortum (Nutting, 1905) species inquirenda (from Lafoea contorta Nutting, 1905)

Filellum disaggregatum Peña Cantero et al., 1998

Filellum expansum Levinsen, 1893 = Folliculina gigantea (Dons, 1910) (Ciliophora), after Dons (1910) and Vannucci (1955)

Filellum gabriellae Vannucci, 1949 = Folliculina gigantea (Dons, 1910) (Ciliophora), after Vannucci (1955)

Filellum magnificum Peña Cantero et al., 2004b

Filellum minimum García Corrales et al., 1979 = Folliculina gigantea (Dons, 1910) (Ciliophora), after Peña Cantero et al. 1998

Filellum nitidum Watson, 2005

Filellum parasiticum (Antsulevich, 1987) (from Lineolaria parasitica Antsulevich, 1987)

Filellum plicatum (Hartlaub, 1904) species inquirenda (from Lafoea plicata Hartlaub, 1904)

Filellum serpens (Hassall, 1848) (from Campanularia serpens Hassall, 1848)

Filellum serratum (Clarke, 1879) (from Lafoea serrata Clarke, 1879)

Filellum tubiforme Schydlowsky, 1902 = Filellum serpens (Hassall, 1848)