Macrorhynchia philippina Kirchenpauer, 1872

Calder, Dale R. & Faucci, Anuschka, 2021, Shallow water hydroids (Cnidaria, Hydrozoa) from the 2002 NOWRAMP cruise to the Northwestern Hawaiian Islands, Zootaxa 5085 (1), pp. 1-73 : 52-53

Macrorhynchia philippina Kirchenpauer, 1872

Fig. 14g

Macrorhynchia philippina Kirchenpauer, 1872: 19 .— Hoover, 1998: 21, unnumbered figure; 2006: 21, unnumbered figure.— Coles et al., 2004: 72.— Calder, 2020: 235, fig. 9g.

Aglaophenia philippina Kirchenpauer, 1872: 45 , text-fig. p. 17; pl. 1 fig. 26; pl. 2 fig. 26a–b; pl. 7 fig. 26.

Type locality. Philippines: Manila ( Kirchenpauer 1872) .

Voucher material. Pearl & Hermes Atoll , 28.ix.2002, one fragmentary colony, 3 cm high, without gonophores, coll. A. Faucci, ROMIZ B5469 .— Midway Atoll , detached, 20.ix.2002, two colony fragments, to 4.5 cm high, without gonophores, coll. A. Faucci, ROMIZ B5470 .

Remarks. In the original description of this species by Kirchenpauer (1872), its binomen was introduced as both Macrorhynchia philippina and Aglaophenia philippina , with a full account under the latter name. Macrorhynchia Kirchenpauer, 1872 was proposed in that work as a subgenus of Aglaophenia Lamouroux, 1812 , and later elevated to generic rank by Stechow (1920). Currently included as subjective synonyms of M. philippina are A. urens Kirchenpauer, 1872 , Lytocarpus crosslandi Ritchie, 1907 , and L. philippinus atlanticus Billard, 1913 ( Calder 1997; Ansín Agís et al. 2001). As for the names Aglaophenia perforata and Aglaophenia (Macrorhynchia) perforata used by Kirchenpauer (1872) and Stechow (1919b), both are nomenclaturally unavailable ( Calder 1997). With M. philippina and A. urens being simultaneous synonyms, their relative precedence was established by Bale (1919), as First Reviser (ICZN 1999, Art. 24.2.2). Macrorhynchia philippina was chosen by him as the valid name of the species.

Based on traditional taxonomic investigations, M. philippina is thought to have an exceptionally wide geographic distribution in shallow tropical to warm-temperate waters (e.g., Millard 1975, as Lytocarpus philippinus ; Calder 1983, 2013; Hirohito 1995; Migotto 1996; Watson 2000; Ansín Agís et al. 2001; Schuchert 2003; Vervoort & Watson 2003; Di Camillo et al. 2009; Chakraborty & Raghunathan 2020). That conclusion has now been generally supported by molecular phylogenetic studies ( Moura et al. 2012, 2018, 2019; Postaire et al. 2016b; Boissin et al. 2018). Of two putative species detected under the binomen by Moura et al. (2018), one extended from the southwest Indian Ocean to the tropical west Pacific, and the other was taken to be circumglobal in tropical and subtropical waters. In a study of some 198 putative species of plumularioids by Moura et al. (2019), only M. philippina and a clade of Halopteris cf. alternata displayed corresponding 16S haplotypes in the Atlantic and the eastern Pacific oceans on either side of the Central American Isthmus. Transport of the species across this and other biogeographic barriers has been attributed to either human-mediated dispersal or rafting, or both ( Moura et al. 2012, 2018, 2019; Boissin et al. 2018). Macrorhynchia philippina is known to liberate actively swimming medusoids ( Gravier 1970; Migotto 1996; Watson 2000; Bourmaud & Gravier-Bonnet 2004; Galea 2018). However, in being very short-lived (ca. 2 hours) and negatively buoyant ( Gravier 1970; Gravier-Bonnet & Migotto 2000), their capacity for dispersal appears decidedly limited. An account of the colonization and expansion of this invasive species on Gran Canaria Island, Canary Islands, in the eastern North Atlantic, has been described by Espino et al. (2020).

Lytocarpus balei Nutting, 1905 from waters off Molokai, Hawaii, at first thought by Billard (1907) to be conspecific with M. philippina , is now considered a valid species ( Stechow 1907, 1909; Billard 1913; Schuchert 2003, 2015, 2021d; Calder 2020). Currently assigned the binomen Macrorhynchia balei , it differs from M. philippina in having nematopores on cladial internodes below the hydrothecae, and on primary and auxiliary tubes of the hydrocauli. Other differences distinguishing the two species have been noted by Schuchert (2003). Molecular studies ( Moura et al. 2019) further support recognition of both species.

Macrorhynchia philippina is a typically large, branched species. Although colonies are usually smaller than 15 cm high, they may attain heights of as much as two feet (61 cm) ( Pictet 1893). Identification of M. philippina in the field is facilitated by its colony morphology, its dark stems and branches, and especially its salient white to translucent cladia. Hydroids of the species have long been known to be venomous to humans ( Kirchenpauer 1872, as Aglaophenia urens ; Gravely 1927, as Lytocarpus philippinus ; Halstead 1988, as L. philippinus ; Rifkin et al. 1993, as L. philippinus ; Santhanam 2020).

Reported Distribution. Hawaiian archipelago. Oahu: Palea Point, 30 ft (9 m) ( Hoover 1998, 2006; Calder 2020).—Molokai: Hale O Lono Reef ( Coles et al. 2004).

Elsewhere. Circumglobal in shallow tropical, subtropical, and warm-temperate seas ( Calder 1997, 2013, 2019; Ansín Agís et al. 2001; Schuchert 2003; Xu et al. 2014b; Moura et al. 2018, 2019; Chakraborty & Raghunathan 2020).

Figures

FIGURE 14. Aglaopheniidae. a, Aglaophenia postdentata Billard, 1913, part of a cladium with two hydrothecae, Gardner Pinnacles, ROMIZ B5462. Scale equals 0.1 mm. b, Aglaophenia suensonii Jäderholm, 1896, part of a cladium with three hydrothecae, Laysan Island, ROMIZ B5463. Scale equals 0.1 mm. c, Aglaophenia suensonii Jäderholm, 1896, corbula, Laysan Island, ROMIZ B5463. Scale equals 0.2 mm. d, Aglaophenia whiteleggei Bale, 1888, part of a cladium with two hydrothecae, Pearl & HermesAtoll, ROMIZ B5464. Scale equals 0.1 mm. e, Lytocarpia flexuosa (Lamouroux, 1816), part of a cladium with three hydrothecae, Pearl & Hermes Atoll, ROMIZ B5479. Scale equals 0.1 mm. f, Lytocarpia phyteuma (Stechow, 1919b), part of a cladium with two hydrothecae, Pearl & Hermes Atoll, ROMIZ B5468. Scale equals 0.1 mm. g, Macrorhynchia philippina Kirchenpauer, 1872, part of a cladium with two hydrothecae, Midway Atoll, ROMIZ B5470. Scale equals 0.1 mm. h, Macrorhynchia phoenicea (Busk, 1852), part of a cladium with three hydrothecae, Gardner Pinnacles, ROMIZ B5475. Scale equals 0.1 mm. i, Macrorhynchia phoenicea (Busk, 1852), one phylactocarp, without gonothecae, Gardner Pinnacles, ROMIZ B5475. Scale equals 0.2 mm.