Hydroides cf. brachyacantha Rioja, 1941a

Figs 4B, 5

Hydroides cf. brachyacanthus – Bastida-Zavala & ten Hove 2002: 154 –155, figs 29A–K, 31A–D, 33 (Cura ҫao, Venezuela and Grenada; intertidal to 20 m, on Rhizophora and Thalassia, mud and sand, and a destroyer hull).

Hydroides brachyacantha (non Rioja 1941a) – Zibrowius 1970: 6 (São Sebastião, Ubatuba, Brazil; 6–15 m, rocks, corals and gorgonians). — Díaz-Díaz & Liñero-Arana 2001: 11 –12, fig. 2g–m (Cariaco Gulf, Venezuela; on PVC dock pilings).

Material examined

Seven specimens: BB (1) Aug. 2004, PB (6) Aug. 2002.

Diagnosis

Tube white; without peristomes, transverse ridges, longitudinal ridges or alveoli. Opercular peduncle smooth, white. Opercular funnel with 19–30 radii with pointed tip (Fig. 4B); verticil with 7–8 spines, strongly curving inwards; dorsalmost spine larger; all spines with basal internal spinule, without external and lateral spinules, or wings (Fig. 4B). Special collar chaetae with two blunt, short teeth and smooth distal blade.

Taxonomic remarks

The nominal species, Hydroides brachyacantha, has been recorded in various parts of the world including Australia (Dew 1959; Straughan 1967; Kupriyanova et al. 2006), Hawaii (Straughan 1969; Bailey-Brock 1976, 1987; Bastida-Zavala & ten Hove 2003; Carlton & Eldredge 2009), Palau and Yap Islands (Imajima 1982), Truk and Ponape Islands, and Majuro Atoll (Imajima & ten Hove 1984), Solomon Islands (Imajima & ten Hove 1986), Israel (Ben-Eliahu 1991; Ben-Eliahu & ten Hove 1992), northeastern Venezuela (Díaz-Díaz & Liñero-Arana 2001) and Turkey (Çinar 2006).

However, most of the records of H. brachyacantha from Australia belong to a new species recently described from Australia, H. amri Sun, Wong, ten Hove, Hutchings, Williamson & Kupriyanova, 2015 . The records from Hawaii also belong to a similar species, recently reported as H. cf. amri (Bastida-Zavala et al. 2016) .The specimens recorded from Turkey apparently belong to H.brachyacantha sensu stricto, which might have reached the Turkish coast via ship-borne fouling (Çinar 2006, fig. 2). Due to the absence of a holotype, a specimen collected from the type locality (Mazatlán, Mexico) was designated as the neotype (Sun et al. 2016b).

While the specimens recorded from the western Atlantic also resemble H. brachyacantha, they do not have the characteristic large knobs on the verticil spines of the nominal species(Bastida-Zavala&ten Hove2003: figs 3A, C, G–K), nor the small “sharp to round knob” of H. amri (Sun et al. 2015: fig. 3A–B).Apparently, in the Caribbean there are two forms of H. cf. brachyacantha, one from Grenada with a large dorsal spine and six smaller spines on the rest of the verticil (Bastida-Zavala & ten Hove 2002: fig. 29A–C), and the other from Brazil and Venezuela, with dorsal spines smaller than those in Grenada’s specimens (Bastida-Zavala & ten Hove 2002: fig. 29D–F). The specimens examined in this survey (Fig. 4B) are more similar to the Brazilian and Venezuelan form.

Ecology

Intertidal to sublittoral (20 m). In tropical marine areas, on mangrove, seagrass, rocks, corals and gorgonians, and artificial substrates (Zibrowius 1970; Díaz-Díaz & Liñero-Arana 2001; Bastida-Zavala & ten Hove 2002).

Distribution

Eastern Caribbean to southeastern Brazil (Zibrowius 1970; Bastida-Zavala & ten Hove 2002). In this work, Hydroides cf. brachyacantha was occasionally found on fouling plates from Biscayne Bay and Pensacola Bay, Florida (Fig. 5). This species extends its northward range from Cura ҫao, southern Caribbean (Bastida-Zavala & ten Hove 2002) to Pensacola Bay, Florida (2700 km).