Hydroides gracilis ( Bush, 1905 )

Bastida-Zavala, J. Rolando, McCANN, Linda D., Keppel, Erica & Ruiz, Gregory M., 2017, The fouling serpulids (Polychaeta: Serpulidae) from United States coastal waters: an overview, European Journal of Taxonomy 344, pp. 1-76 : 35-36

Hydroides gracilis ( Bush, 1905)

Figs 4G , 6

Eupomatus gracilis Bush, 1905: 234–235 , pl. 27, fig. 9, pl. 34, fig. 25, pl. 37, figs 26–27 (type locality: Pacific Grove, California, United States).

Eupomatus intereans Chamberlin, 1919a: 23 (type locality: Laguna Beach, southern California).

Eupomatus gracilis – Treadwell 1914: 225 ( San Pedro and San Diego, southern California).

Hydroides uncinata (non Philippi 1844) – Berkeley & Berkeley 1941: 56 (southern California; on seaweed holdfast); 1958: 405 (west coast of Baja California Peninsula: Tortugas Bay, Baja California Sur).

Hydroides gracilis – Zibrowius 1971: 694 –695 (synonymization of E. intereans and H. uncinata recorded by Berkeley & Berkeley 1941, 1958). — Bastida-Zavala & ten Hove 2003: 89 –92, fig. 13A–V (California and Baja California, Mexican Pacific; intertidal to 5 m; on colony of vermetid Aletes sp., on Trochidae , also from aquaculture tanks and lead filter). — Bastida-Zavala 2008: 27, fig. 6K (California; PVC plates).

Material examined

232 specimens: SF (3) Sep. 2000 and 2001, LB (185) Sep. 2003, MO (5) Sep. 2013, MI (7) Aug. 2013, SD (32) Aug. 2000 and Jul. 2013.

Diagnosis

Tube white; with two longitudinal ridges, with or without peristomes; but no transverse ridges or alveoli. Opercular peduncle smooth, white. Opercular funnel with 16–42 radii with pointed tips ( Fig. 4G ); verticil with 9–12 smooth spines, curving inwards, without internal, external or lateral spinules or wings ( Fig. 4G ). Special collar chaetae with two blunt or pointed teeth and smooth distal blade.

Taxonomic remarks

Two tiny specimens have the Hydroides “ priscus ” type opercula ( ten Hove & Ben-Eliahu 2005), with only a chitinous funnel instead of the normal funnel and verticil. The abundance of H. gracilis is variable in the fouling community, sometimes occurring at high abundances. Nonetheless, its distribution is restricted to California and the west coast of the Baja California Peninsula.

Ecology

Intertidal to sublittoral (5 m). On holdfast of seaweeds, shells of gastropods ( Aletes sp. and Trochidae ), and in aquaculture facilities ( Berkeley & Berkeley 1941; Bastida-Zavala & ten Hove 2003).

Distribution

California to Bahía Tortugas, west coast of Baja California Peninsula ( Bastida-Zavala & ten Hove 2003). In this work, Hydroides gracilis was found abundantly on fouling plates from Long Beach and San Diego, California; and occasionally from San Francisco, Morro Bay and Mission Bay, California ( Fig. 6 ). Hydroides gracilis extends its range northward from Pacific Grove ( Bush 1905) to San Francisco, California (140 km).

Figures

Fig. 4. Serpulids from United States fouling plates. Hydroides bispinosa. A. Operculum, from Biscayne Bay, Florida (SERC-118756). – H. cf. brachyacantha. B. Operculum, Pensacola Bay, Florida (SERC- 92415). – H. dianthus. C. Operculum, Corpus Christi, Texas (SERC-87878RB). – H. dirampha. D. Operculum, Biscayne Bay, Florida (SERC-118709). – H. elegans. E. Operculum, San Diego, California (SERC-04075R). – H. floridana. F. Operculum, Corpus Christi, Texas (SERC-87968). – H. gracilis. G. Operculum, San Diego, California (SERC-34585R). – H. longispinosa. H. Operculum, Oahu, Hawaii (SERC-19654). – H. parva. I. Operculum, Biscayne Bay, Florida (SERC-118709). – H. sanctaecrucis. J. Operculum, Tampa Bay, Florida (SERC-66920R).

Fig. 6. Distribution of serpulids (Hydroides spp.) from United States fouling plates (closed symbols) and literature records (open symbols).