Hincksella cylindrica ( Bale, 1888 )

Galea, Horia R., 2010, Additional shallow-water thecate hydroids (Cnidaria: Hydrozoa) from Guadeloupe and Les Saintes, French Lesser Antilles, Zootaxa 2570, pp. 1-40 : 20-23

Hincksella cylindrica ( Bale, 1888)

(fig. 5N–P, table 3)

Sertularella cylindrica Bale, 1888: 765 , pl. 16 fig. 7.

Sertularella cylindrica var. pusilla Ritchie, 1910: 817 , pl. 77 fig. 9.

Synthecium cylindricum ― Nutting, 1904: 136, pl. 41 fig. 7.― Ritchie, 1911: 847.― Fraser, 1944: 234, pl. 48 fig. 216.― Fraser, 1948: 234.

Synthecium cylindricum var. pusilla ― Leloup, 1935: 31, fig. 14.― Leloup, 1940: 3, fig. 2.

Hincksella cylindrica var. pusilla ― Billard, 1925: 124.― Vervoort, 1959: 247, fig. 19B, C.― Vervoort, 1968: 28, fig. 12.―Hirohito, 1983: 35.

Hincksella cylindrica pusilla ― Millard, 1964: 22, fig. 6A–D.―Millard, 1975: 232, fig. 76B–E.― Millard & Bouillon, 1975: 12.―Hirohito, 1995: 151, fig. 48A, B.

Hincksella cylindrica ― Blackburn, 1937: 173, fig. 2.― Pennycuik, 1959: 198.― Watson, 1979: 234.― Calder, 1991: 82, fig. 43.― Calder, 1993: 68.― Watson & McInnes, 1999: 108, fig. 4C.― Watson, 2002: 346, fig. 5D.― Calder et al., 2003: 1188, fig. 12. ― Watson, 2003: 250.

Sertularella halecina Torrey, 1902: 61 , pl. 6 fig. 55, pl. 7 fig. 56.― Torrey, 1904: 26, figs 14–18.

Cyclonia gracilis Stechow, 1921: 230 .

Cyclonia pusilla ―Hirohito, 1969: 16, fig. 12.

Synthecium gracile Fraser, 1937: 2 , pl. 1 fig. 2.― Fraser, 1938b: 134.― Fraser, 1943: 91.― Deevey, 1954: 270.

Synthecium (?) gracile ― Fraser, 1944: 234, pl. 48 fig. 217.

Material examined. Stn.9: 21.11.2009, 21 m—numerous sterile stems to 8 mm high, on sponge. Stn.10: 0 2.12.2009, 15–20 m—a few sterile stems to 4 mm high, on Halimeda sp., and numerous sterile stems to 9 mm high, on sponge (the latter as MHNG-INVE-68725). Stn.12: 30.11.2009, 12–15 m—two sterile colonies with stems to 8 mm high, on worm tubes (part as MNHN-IK.2009-814).

Remarks. Billard (1910) included Sertularella cylindrica Bale, 1888 in the synonymy of Synthecium alternans Allman, 1888 , mainly based on their common geographical origin, and also on some unspecified similar characteristics (“caractères semblables de ces deux formes”, p. 27). Nevertheless, he admitted, by comparing the figures provided by Allman and Bale, that the free part of the hydrotheca was comparatively shorter in S. alternans than in S. cylindrica .

Millard (1964), as Vervoort (1968), as Millard & Bouillon (1975), Calder (1991), as Hincksella cylindrica Hincksella cylindrica var. as Hincksella cylindrica Hincksella cylindrica pusilla pusilla pusilla

Stem

Distribution South Africa St. Thomas, Caribbean South Africa Bermuda, W Atlantic Ritchie (1911), examining material from New South Wales attributable to Bale’s species, rejected Billard’s conclusion and added several personal observations. His specimens were 3.0– 5.3 cm high, though lacking firmness, with monosiphonic stems and irregularly-set, occasionally alternate, up to 2 cm long cladia in one plane, sometimes branching again. The hydrothecae were adnate for one third and of “great tenuity and delicacy”. Ritchie’s specimens, as well as the material examined by Bale, were of considerable dimensions, especially at a microscopic scale (see table 3). Similar specimens were never found again since then, and all the subsequent records attributable to Bale’s (1888) species belong to Ritchie’s (1910) variety pusilla . The latter is characterized by its delicate, short (up to 1 cm high), generally unbranched stems, and comparatively smaller hydrothecae (table 3). The gonothecae of the nominal species are unknown and they may prove different from those described for Ritchie’s variety. Therefore, it is presently unclear whether the two forms belong to the same species, but the more complex habit of Bale’s species and its globally larger size point towards two distinct species. The variety pusilla is held conspecific until additional material, ideally fertile, corresponding phenotypically to Bale’s species is found.

There is apparently no available data on the cnidome of H. cylindrica in particular, and the nematocyst complement of the various members of the genus is incompletely known in general. Two types of undischarged capsules were seen in the present material: small microbasic mastigophores (6.3–6.6 × 2.0–2.1 µm) and large (?) macrobasic mastigophores (17.1–18.6 × 6.1–6.7 µm). As pointed out by Peña Cantero & Vervoort (2003), distinction between the genera Hincksella and Staurotheca Allman, 1888 is not completely understood. While the macrobasic mastigophores seem to characterize the syntheciid genus Hincksella , only microbasic mastigophores have been reported in the sertulariid genus Staurotheca . The present observations support the distinction between the two genera.

The gonothecae of H. cylindrica var. pusilla have rarely been found. According to the available data from the literature, the male gonothecae are club-shaped, simple or occasionally forked, and arise either from within the hydrothecae or the stolon ( Torrey 1902, 1904; Hirohito 1969, 1995; Millard & Bouillon 1975). The female gonothecae are spherical, pedicellate, and are borne on the stolon ( Stechow 1921, Hirohito 1969). Blackburn (1937) described spherical gonothecae arising from below the hydrothecal base, but no information on the gametes was provided, but nevertheless they were probably female.

Some colonies of H. cylindrica may be branched and, when present, the branches arise generally from within the stem hydrothecae, more rarely from below their bases ( Torrey 1904).

Caribbean records. Aruba and Curaçao ( Leloup 1935), Puerto Rico ( Fraser 1937), Tortugas ( Fraser 1943), St. Thomas ( Vervoort 1968).

World distribution. Circumglobal in tropical to temperate waters: Australia ( Bale 1888; Ritchie 1911; Blackburn 1937; Pennycuik 1959; Watson & McInnes 1999; Watson 2002, 2003), California ( Torrey 1902, 1904, both as Sertularella halecina ; Fraser 1948), Mergui Islands ( Ritchie 1910), Borneo ( Billard 1925), Ecuador, Pacific coasts of Panama and Colombia ( Fraser 1938b), West coast of Lower California ( Mexico) ( Fraser 1948), Japan ( Leloup 1940; Hirohito 1969, 1983, 1995), off Guinea Bissau ( Vervoort 1959), South Africa ( Millard 1964, 1975), Seychelles ( Millard & Bouillon 1975), Bermuda ( Calder 1991, 1993), Galápagos ( Calder et al. 2003).