Symplectoscyphus fasciculatus, Galea, 2016

Galea, Horia R., 2016, Notes on some sertulariid hydroids (Cnidaria: Hydrozoa) from the tropical western Pacific, with descriptions of nine new species, European Journal of Taxonomy 218, pp. 1-52 : 41-45

Symplectoscyphus fasciculatus nom. nov.

Fig. 10 I–L

Symplectoscyphus johnstoni tropicus Vervoort, 1993: 259 , figs 61, 62a–d [not S. johnstoni (Gray, 1843) ].

non Symplectoscyphus johnstoni tropicus – Vervoort & Watson 2003: 217, fig. 51f–l.

Material examined

Holotype

MUSORSTOM 4: Stn. CP153, “several well developed, flabellate colonies 30× 50 mm, stems basally polysiphonic; many appressed gonothecae […]. One large colony 30× 40 mm is holotype (MNHN-Hy. 1117)” ( Vervoort 1993).

Additional material

MUSORTSOM 4: Stn. CC 174, a 4.5 cm high, fertile (male) colony.

Description

Flaccid, flabellate, up to 4 cm high and 5 cm wide colonies arising from branched, rhizoid stolon. Stems strongly fascicled basally, thinning out gradually to monosiphonic distally; flexuous, usually regularly and alternately branched; occasionally with “irregular” branches resulting from considerable development of secondary stems from branches growing as long as the main stem itself, and resulting in multiple tangled stems, whose distalmost branches form multiple anastomoses between them and with neighboring stems. Division into internodes indistinct, even in monosiphonic parts, but equivalents of internodes long, geniculate, comprising a basal apophysis and its associated axillar hydrotheca, as well as two alternate hydrothecae above. Apophyses alternate. Side branches straight (until they rebranch again in pseudodichotomous manner), nodes indistinct, but each equivalent of internode bearing hydrothecae arranged alternately. Hydrothecae tubular, curving away from internode, adnate for nearly half their length. Free adaxial wall straight to slightly convex; abaxial wall straight basally, curving suddenly in its distal third. Hydrothecal aperture nearly parallel to longitudinal axis of internode; margin with three pointed cusps separated by rather deep embayments; adaxial cusp recurved; renovations common and numerous. No conspicuous submarginal, intrathecal cusps, except for an occasional abaxial thickening. Gonothecae given off from below hydrothecal bases, fitting tightly and neatly against internodes. Male and female similar in shape; sac-shaped, wall undulated and never ribbed; undulations more pronounced distally, fading off basally; aperture distal, borne on outwardly-projecting, trumpet-shaped terminal tube.

Remarks

The description provided above combines Vervoort’s (1993) account with personal observations of the material in hand. The latter apparently belongs to a “large tangled tuft of c. 30 mm high colonies on wormtubes” previously examined by Vervoort.

Owing to the fasciculate habit of its stems and the gonothecae with undulated walls, the large material studied by Vervoort was assigned to a new subspecies, tropicus , of Symplectoscyphus johnstoni (Gray, 1843) . In doing so, Vervoort distinguished it from its congeners with monosiphonic stems and transversely-ribbed gonothecae, viz. S. johnstoni johnstoni (Gray, 1843) and S. johnstoni subtropicus Ralph, 1961 , the latter being additionally characterized by the presence of three submarginal, intrathecal cusps.

As stated by Ralph (1961), S. johnstoni is a species with strictly monosiphonic stems, and its gonothecae are provided with “8 to14 evenly spaced transverse ridges”. Consequently, the subspecies tropicus could be confidently raised to species. However, when doing so, it becomes an invalid junior homonym of S. tropicus ( Hartlaub, 1901) . To avoid this situation, the junior homonym is replaced here with the binomen S. fasciculatus nom. nov., whose holotype remains the same for both the original and the new name of the single biological species (ICZN Art. 72.7). The measurements of S. fasciculatus nom. nov. are given by Vervoort (1993: 260, table 51).

A restricted number of species belonging to this highly speciose genus are polysiphonic in habit: six congeners from the Antarctic [ S. bellinghauseni Peña Cantero, 2012 ( Peña Cantero 2012); S. cumberlandicus ( Jäderholm, 1905) ( Peña Cantero et al. 2002) ; S. frondosus Peña Cantero, 2010 (Peña Cantero 2010); S. hesperides Peña Cantero, 2012 ( Peña Cantero 2012); S. liouvillei (Billard, 1914) ( Peña Cantero et al. 2002) ; S. sofiae Peña Cantero et al., 2002 ( Peña Cantero et al. 2002)], ten from the subantarctic [ S. adpressus ( Ritchie, 1911) ( Ritchie 1911) ; S. amoenus Vervoort & Watson, 2003 ( Vervoort & Watson 2003); S. arboriformis (Marktanner-Turneretscher, 1890) ( Millard 1975) ; S. columnarius (Briggs, 1914) ( Ralph 1961) ; S. divaricatus (Busk, 1852) ( Ralph 1961) ; S. magellanicus (Marktanner-Turneretscher, 1890) ( Galea & Schories 2012) ; S. patagonicus Galea & Schories, 2012 ( Galea & Schories 2012); S. paulensis Stechow, 1923 ( Watson 2003) ; S. procerus (Trebilcock, 1928) ( Ralph 1961) ; S. subarticulatus (Coughtrey, 1875) ( Millard 1977) ], and two from the tropics, both assigned to S. tropicus Hartlaub, 1901 [sensu Clarke 1894 (as Sertularella variabilis ) and sensu Billard 1925b].

Ecologically, S. fasciculatus nom. nov. occurs in a biogeographical area radically different from that of the majority of species listed above. Its gonothecae are different from those of the following species, which exhibit transverse ridges: S. aggreggatus (Jäderholm, 1917) ( Peña Cantero et al. 2002) , S. arboriformis ( Millard 1975) , S. columnarius ( Ralph 1961) , S. cumberlandicus ( Jäderholm 1905) , S. magellanicus ( Galea & Schories 2012) , S. patagonicus ( Galea et al. 2014) , S. procerus ( Ralph 1961) , S. sofiae ( Peña Cantero et al. 2002) , and S. subarticulatus ( Ralph 1961) . The gonothecae of S. frondosus (Peña Cantero 2010) and S. liouvillei ( Peña Cantero et al. 2002) are exceedingly long and tubular, while those of S. amoenus ( Vervoort & Watson 2003) and S. paulensis ( Peña Cantero 2012) are ovoid and have smooth to slightly undulated walls, yet they are not adherent to their corresponding internodes, and their distal tubes are not eccentrically placed. The habit and shape of the gonothecae of S. fasciculatus nom. nov. come closest to those of S. adpressus . However, the latter is a more robust species, with pinnate appearance, and its hydrothecae are subopposite and highly immersed into their internodes ( Ritchie 1911). Although not completely formed in the specimens of S. bellinghauseni studied by Peña Cantero (2012), the gonothecae seem “to be characterized by the presence of rings”. Similarly, the gonothecae of S. hesperides were incipient and apparently smooth ( Peña Cantero 2012), but this species is distinguished through its hydrothecae that are adnate for one-third or less their adaxial length. Finally, the gonothecae of S. divaricatus are unknown yet, but this species possesses rather highly immersed hydrothecae ( Ralph 1961).

Geographical distribution

New Caledonia ( Vervoort 1993).