Branchiomma bairdi McIntosh 1885

Branchiomma bairdi (McIntosh, 1885)

Branchiomma bairdi, originally from the Caribbean, is a recent introduction in the Gulf of California via the Panama Canal (Tovar-Hernández et al. 2009a, b) and to the eastern Mediterranean through the Gibraltar Strait (Çinar 2009; Giangrande et al. 2012; Arias et al. 2013), Australia (Capa & Murray 2015) and the northeastern Atlantic Ocean (Ramalhosa et al. 2014).

In the Gulf of California, this species is highly abundant reaching densities of 18,000 ind./m 2 in perturbed sites (marinas, ports, shrimp and oyster farms), on hard anthropogenic substrates (metal buoys, hulls of vessels, ropes, floating docks, and concrete and wood water gates), and also reported as epibionts on Crassostrea gigas (Thunberg, 1793) and C. sikamea (Amemiya, 1928), and on natural substrates (rocks and wood) from a marine protect area (Tovar-Hernández et al. 2012; 2014).

Çinar (2009) documented B. bairdi along the coasts of Turkey (Levantine Sea) in 2005 and found specimens at 0.5 and 8 m depth, associated with ropes, rocks and mud, but in low densities (53 ind. m -2). In Lake Faro (Italy), B. bairdi has been recorded since 2007 near a mollusc farm, among photophilic algae, on the leaves of a Cymodocea nodosa (Ucria) Ascherson patch, and on rocks and boulders used for restoration purposes where the overall estimated density of B. bairdi ranged from 35 up to 400 ind. m -2 (Giangrande et al. 2012).

Branchiomma bairdi was also recorded in harbours and ports from Malta, Spain and both coasts of Italy, where it is spreading and overtaking stressed habitats with low species competition, reaching densities of 16,000 ind. m–2 (Arias et al. 2013).

In Cairns, Australia, Capa et al. (2013) recorded B. bairdi based on morphological and molecular data and more recently in Lizard Island, a marine protected area of the Great Barrier Reef (Capa & Murray 2015). Ramalhosa et al. (2014) reported this species on Madeira Island reaching densities of 238–516 ind. m–2.

Branchiomma bairdi is a conspicuous component of most benthic communities and mostly in confined environments and areas degraded by anthropogenic impacts (Arias et al. 2013; Giangrande et al. 2014a).

This species also tolerates broad environmental conditions in the Gulf of California: reproductive specimens live in marine waterbodies with temperatures of 18.4–32.1ºC (average 26.4ºC), salinity ranges from 25.6–38.0 PSU (average 34.2 PSU), and dissolved oxygen concentrations of 3.05–6.66 mg /l (average 4.83 mg /l) (Tovar-Hernández et al. 2011). The highest survivorship temperatures (27–33ºC) and salinities (40–47 PSU) were recorded in shrimp farms from Gulf of California during culture cycles (Tovar-Hernández et al. 2014). In addition, this species tolerates a desiccation period up to 24 hrs (Tovar-Hernández & Yáñez-Rivera, 2012).

The reproductive features, the functional traits and the local environmental conditions are useful to understand and predict the dispersion capability of potentially invasive species (Sarà et al. 2013). The reproductive habits of B. bairdi include both sexual (simultaneous hermaphrodite), and asexual reproduction (architomy). Its success as an invader could be facilitated by chemical defenses that help reduce attacks by predators (Kicklighter & Hay 2007; Giangrande et al. 2014b) especially outside its native range where it lacks native predator. In fact, in Tampa Bay many B. bairdi specimens were found with evidence of predation, including regeneration of the crown. Also, tubes of B. bairdi are colonized by other marine invertebrate NIS, as demonstrated in the Gulf of California for the NIS ascidians B. violaceus, B. schlosseri and P. constellatum and the bryozoans A. verticillata and B. neritina (Tovar- Hernández et al. 2014); Mytilus galloprovincialis is also reported on tubes of B. bairdi in Malta (Arias et al. 2013).

The risk analysis by Tovar-Hernández & Yáñez-Rivera (2012) classified B. bairdi as highly invasive and included it in the Lista de Especies Invasoras de México (CONABIO 2015).